lib/dfsan/dfsan_custom.cpp - llvm-project/compiler-rt - Git at Google

 //===-- dfsan_custom.cpp --------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of DataFlowSanitizer.
 //
 // This file defines the custom functions listed in done_abilist.txt.
 //===----------------------------------------------------------------------===//

 #include <arpa/inet.h>
 #include <assert.h>
 #include <ctype.h>
 #include <dlfcn.h>
 #include <link.h>
 #include <poll.h>
 #include <pthread.h>
 #include <pwd.h>
 #include <sched.h>
 #include <signal.h>
 #include <stdarg.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/epoll.h>
 #include <sys/resource.h>
 #include <sys/select.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>

 #include "dfsan/dfsan.h"
 #include "dfsan/dfsan_chained_origin_depot.h"
 #include "dfsan/dfsan_flags.h"
 #include "dfsan/dfsan_thread.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_internal_defs.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"

 using namespace __dfsan;

 #define CALL_WEAK_INTERCEPTOR_HOOK(f, ...)                                     \
   do {                                                                         \
     if (f)                                                                     \
       f(__VA_ARGS__);                                                          \
   } while (false)
 #define DECLARE_WEAK_INTERCEPTOR_HOOK(f, ...) \
 SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE void f(__VA_ARGS__);

 // Async-safe, non-reentrant spin lock.
 class SignalSpinLocker {
  public:
   SignalSpinLocker() {
     sigset_t all_set;
     sigfillset(&all_set);
     pthread_sigmask(SIG_SETMASK, &all_set, &saved_thread_mask_);
     sigactions_mu.Lock();
   }
   ~SignalSpinLocker() {
     sigactions_mu.Unlock();
     pthread_sigmask(SIG_SETMASK, &saved_thread_mask_, nullptr);
   }

  private:
   static StaticSpinMutex sigactions_mu;
   sigset_t saved_thread_mask_;

   SignalSpinLocker(const SignalSpinLocker &) = delete;
   SignalSpinLocker &operator=(const SignalSpinLocker &) = delete;
 };

 StaticSpinMutex SignalSpinLocker::sigactions_mu;

 extern "C" {
 SANITIZER_INTERFACE_ATTRIBUTE int
 __dfsw_stat(const char *path, struct stat *buf, dfsan_label path_label,
             dfsan_label buf_label, dfsan_label *ret_label) {
   int ret = stat(path, buf);
   if (ret == 0)
     dfsan_set_label(0, buf, sizeof(struct stat));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_stat(
     const char *path, struct stat *buf, dfsan_label path_label,
     dfsan_label buf_label, dfsan_label *ret_label, dfsan_origin path_origin,
     dfsan_origin buf_origin, dfsan_origin *ret_origin) {
   int ret = __dfsw_stat(path, buf, path_label, buf_label, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_fstat(int fd, struct stat *buf,
                                                dfsan_label fd_label,
                                                dfsan_label buf_label,
                                                dfsan_label *ret_label) {
   int ret = fstat(fd, buf);
   if (ret == 0)
     dfsan_set_label(0, buf, sizeof(struct stat));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_fstat(
     int fd, struct stat *buf, dfsan_label fd_label, dfsan_label buf_label,
     dfsan_label *ret_label, dfsan_origin fd_origin, dfsan_origin buf_origin,
     dfsan_origin *ret_origin) {
   int ret = __dfsw_fstat(fd, buf, fd_label, buf_label, ret_label);
   return ret;
 }

 static char *dfsan_strchr_with_label(const char *s, int c, size_t *bytes_read,
                                      dfsan_label s_label, dfsan_label c_label,
                                      dfsan_label *ret_label) {
   char *match_pos = nullptr;
   for (size_t i = 0;; ++i) {
     if (s[i] == c || s[i] == 0) {
       // If s[i] is the \0 at the end of the string, and \0 is not the
       // character we are searching for, then return null.
       *bytes_read = i + 1;
       match_pos = s[i] == 0 && c != 0 ? nullptr : const_cast<char *>(s + i);
       break;
     }
   }
   if (flags().strict_data_dependencies)
     *ret_label = s_label;
   else
     *ret_label = dfsan_union(dfsan_read_label(s, *bytes_read),
                              dfsan_union(s_label, c_label));
   return match_pos;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strchr(const char *s, int c,
                                                   dfsan_label s_label,
                                                   dfsan_label c_label,
                                                   dfsan_label *ret_label) {
   size_t bytes_read;
   return dfsan_strchr_with_label(s, c, &bytes_read, s_label, c_label,
                                  ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strchr(
     const char *s, int c, dfsan_label s_label, dfsan_label c_label,
     dfsan_label *ret_label, dfsan_origin s_origin, dfsan_origin c_origin,
     dfsan_origin *ret_origin) {
   size_t bytes_read;
   char *r =
       dfsan_strchr_with_label(s, c, &bytes_read, s_label, c_label, ret_label);
   if (flags().strict_data_dependencies) {
     *ret_origin = s_origin;
   } else if (*ret_label) {
     dfsan_origin o = dfsan_read_origin_of_first_taint(s, bytes_read);
     *ret_origin = o ? o : (s_label ? s_origin : c_origin);
   }
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strpbrk(const char *s,
                                                    const char *accept,
                                                    dfsan_label s_label,
                                                    dfsan_label accept_label,
                                                    dfsan_label *ret_label) {
   const char *ret = strpbrk(s, accept);
   if (flags().strict_data_dependencies) {
     *ret_label = ret ? s_label : 0;
   } else {
     size_t s_bytes_read = (ret ? ret - s : strlen(s)) + 1;
     *ret_label =
         dfsan_union(dfsan_read_label(s, s_bytes_read),
                     dfsan_union(dfsan_read_label(accept, strlen(accept) + 1),
                                 dfsan_union(s_label, accept_label)));
   }
   return const_cast<char *>(ret);
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strpbrk(
     const char *s, const char *accept, dfsan_label s_label,
     dfsan_label accept_label, dfsan_label *ret_label, dfsan_origin s_origin,
     dfsan_origin accept_origin, dfsan_origin *ret_origin) {
   const char *ret = __dfsw_strpbrk(s, accept, s_label, accept_label, ret_label);
   if (flags().strict_data_dependencies) {
     if (ret)
       *ret_origin = s_origin;
   } else {
     if (*ret_label) {
       size_t s_bytes_read = (ret ? ret - s : strlen(s)) + 1;
       dfsan_origin o = dfsan_read_origin_of_first_taint(s, s_bytes_read);
       if (o) {
         *ret_origin = o;
       } else {
         o = dfsan_read_origin_of_first_taint(accept, strlen(accept) + 1);
         *ret_origin = o ? o : (s_label ? s_origin : accept_origin);
       }
     }
   }
   return const_cast<char *>(ret);
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strsep(char **s, const char *delim,
                                                   dfsan_label s_label,
                                                   dfsan_label delim_label,
                                                   dfsan_label *ret_label) {
   dfsan_label base_label = dfsan_read_label(s, sizeof(*s));
   char *base = *s;
   char *res = strsep(s, delim);
   if (res != *s) {
     char *token_start = res;
     int token_length = strlen(res);
     // the delimiter byte has been set to NULL
     dfsan_set_label(0, token_start + token_length, 1);
   }

   if (flags().strict_data_dependencies) {
     *ret_label = res ? base_label : 0;
   } else {
     size_t s_bytes_read = (res ? strlen(res) : strlen(base)) + 1;
     *ret_label = dfsan_union(
         dfsan_union(base_label, dfsan_read_label(base, sizeof(s_bytes_read))),
         dfsan_union(dfsan_read_label(delim, strlen(delim) + 1),
                     dfsan_union(s_label, delim_label)));
   }

   return res;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strsep(
     char **s, const char *delim, dfsan_label s_label, dfsan_label delim_label,
     dfsan_label *ret_label, dfsan_origin s_origin, dfsan_origin delim_origin,
     dfsan_origin *ret_origin) {
   dfsan_origin base_origin = dfsan_read_origin_of_first_taint(s, sizeof(*s));
   char *res = __dfsw_strsep(s, delim, s_label, delim_label, ret_label);
   if (flags().strict_data_dependencies) {
     if (res)
       *ret_origin = base_origin;
   } else {
     if (*ret_label) {
       if (base_origin) {
         *ret_origin = base_origin;
       } else {
         dfsan_origin o =
             dfsan_read_origin_of_first_taint(delim, strlen(delim) + 1);
         *ret_origin = o ? o : (s_label ? s_origin : delim_origin);
       }
     }
   }

   return res;
 }

 static int dfsan_memcmp_bcmp(const void *s1, const void *s2, size_t n,
                              size_t *bytes_read) {
   const char *cs1 = (const char *) s1, *cs2 = (const char *) s2;
   for (size_t i = 0; i != n; ++i) {
     if (cs1[i] != cs2[i]) {
       *bytes_read = i + 1;
       return cs1[i] - cs2[i];
     }
   }
   *bytes_read = n;
   return 0;
 }

 static dfsan_label dfsan_get_memcmp_label(const void *s1, const void *s2,
                                           size_t pos) {
   if (flags().strict_data_dependencies)
     return 0;
   return dfsan_union(dfsan_read_label(s1, pos), dfsan_read_label(s2, pos));
 }

 static void dfsan_get_memcmp_origin(const void *s1, const void *s2, size_t pos,
                                     dfsan_label *ret_label,
                                     dfsan_origin *ret_origin) {
   *ret_label = dfsan_get_memcmp_label(s1, s2, pos);
   if (*ret_label == 0)
     return;
   dfsan_origin o = dfsan_read_origin_of_first_taint(s1, pos);
   *ret_origin = o ? o : dfsan_read_origin_of_first_taint(s2, pos);
 }

 static int dfsan_memcmp_bcmp_label(const void *s1, const void *s2, size_t n,
                                    dfsan_label *ret_label) {
   size_t bytes_read;
   int r = dfsan_memcmp_bcmp(s1, s2, n, &bytes_read);
   *ret_label = dfsan_get_memcmp_label(s1, s2, bytes_read);
   return r;
 }

 static int dfsan_memcmp_bcmp_origin(const void *s1, const void *s2, size_t n,
                                     dfsan_label *ret_label,
                                     dfsan_origin *ret_origin) {
   size_t bytes_read;
   int r = dfsan_memcmp_bcmp(s1, s2, n, &bytes_read);
   dfsan_get_memcmp_origin(s1, s2, bytes_read, ret_label, ret_origin);
   return r;
 }

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, uptr caller_pc,
                               const void *s1, const void *s2, size_t n,
                               dfsan_label s1_label, dfsan_label s2_label,
                               dfsan_label n_label)

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_memcmp, uptr caller_pc,
                               const void *s1, const void *s2, size_t n,
                               dfsan_label s1_label, dfsan_label s2_label,
                               dfsan_label n_label, dfsan_origin s1_origin,
                               dfsan_origin s2_origin, dfsan_origin n_origin)

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_memcmp(const void *s1, const void *s2,
                                                 size_t n, dfsan_label s1_label,
                                                 dfsan_label s2_label,
                                                 dfsan_label n_label,
                                                 dfsan_label *ret_label) {
   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_memcmp, GET_CALLER_PC(), s1, s2, n,
                              s1_label, s2_label, n_label);
   return dfsan_memcmp_bcmp_label(s1, s2, n, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_memcmp(
     const void *s1, const void *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label,
     dfsan_origin s1_origin, dfsan_origin s2_origin, dfsan_origin n_origin,
     dfsan_origin *ret_origin) {
   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_memcmp, GET_CALLER_PC(), s1,
                              s2, n, s1_label, s2_label, n_label, s1_origin,
                              s2_origin, n_origin);
   return dfsan_memcmp_bcmp_origin(s1, s2, n, ret_label, ret_origin);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_bcmp(const void *s1, const void *s2,
                                               size_t n, dfsan_label s1_label,
                                               dfsan_label s2_label,
                                               dfsan_label n_label,
                                               dfsan_label *ret_label) {
   return dfsan_memcmp_bcmp_label(s1, s2, n, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_bcmp(
     const void *s1, const void *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label,
     dfsan_origin s1_origin, dfsan_origin s2_origin, dfsan_origin n_origin,
     dfsan_origin *ret_origin) {
   return dfsan_memcmp_bcmp_origin(s1, s2, n, ret_label, ret_origin);
 }

 // When n == 0, compare strings without byte limit.
 // When n > 0, compare the first (at most) n bytes of s1 and s2.
 static int dfsan_strncmp(const char *s1, const char *s2, size_t n,
                          size_t *bytes_read) {
   for (size_t i = 0;; ++i) {
     if (s1[i] != s2[i] || s1[i] == 0 || s2[i] == 0 || (n > 0 && i == n - 1)) {
       *bytes_read = i + 1;
       return s1[i] - s2[i];
     }
   }
 }

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_strcmp, uptr caller_pc,
                               const char *s1, const char *s2,
                               dfsan_label s1_label, dfsan_label s2_label)

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_strcmp, uptr caller_pc,
                               const char *s1, const char *s2,
                               dfsan_label s1_label, dfsan_label s2_label,
                               dfsan_origin s1_origin, dfsan_origin s2_origin)

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_strcmp(const char *s1, const char *s2,
                                                 dfsan_label s1_label,
                                                 dfsan_label s2_label,
                                                 dfsan_label *ret_label) {
   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_strcmp, GET_CALLER_PC(), s1, s2,
                              s1_label, s2_label);
   size_t bytes_read;
   int r = dfsan_strncmp(s1, s2, 0, &bytes_read);
   *ret_label = dfsan_get_memcmp_label(s1, s2, bytes_read);
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_strcmp(
     const char *s1, const char *s2, dfsan_label s1_label, dfsan_label s2_label,
     dfsan_label *ret_label, dfsan_origin s1_origin, dfsan_origin s2_origin,
     dfsan_origin *ret_origin) {
   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_strcmp, GET_CALLER_PC(), s1,
                              s2, s1_label, s2_label, s1_origin, s2_origin);
   size_t bytes_read;
   int r = dfsan_strncmp(s1, s2, 0, &bytes_read);
   dfsan_get_memcmp_origin(s1, s2, bytes_read, ret_label, ret_origin);
   return r;
 }

 // When n == 0, compare strings without byte limit.
 // When n > 0, compare the first (at most) n bytes of s1 and s2.
 static int dfsan_strncasecmp(const char *s1, const char *s2, size_t n,
                              size_t *bytes_read) {
   for (size_t i = 0;; ++i) {
     char s1_lower = tolower(s1[i]);
     char s2_lower = tolower(s2[i]);

     if (s1_lower != s2_lower || s1[i] == 0 || s2[i] == 0 ||
         (n > 0 && i == n - 1)) {
       *bytes_read = i + 1;
       return s1_lower - s2_lower;
     }
   }
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_strcasecmp(const char *s1,
                                                     const char *s2,
                                                     dfsan_label s1_label,
                                                     dfsan_label s2_label,
                                                     dfsan_label *ret_label) {
   size_t bytes_read;
   int r = dfsan_strncasecmp(s1, s2, 0, &bytes_read);
   *ret_label = dfsan_get_memcmp_label(s1, s2, bytes_read);
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_strcasecmp(
     const char *s1, const char *s2, dfsan_label s1_label, dfsan_label s2_label,
     dfsan_label *ret_label, dfsan_origin s1_origin, dfsan_origin s2_origin,
     dfsan_origin *ret_origin) {
   size_t bytes_read;
   int r = dfsan_strncasecmp(s1, s2, 0, &bytes_read);
   dfsan_get_memcmp_origin(s1, s2, bytes_read, ret_label, ret_origin);
   return r;
 }

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_strncmp, uptr caller_pc,
                               const char *s1, const char *s2, size_t n,
                               dfsan_label s1_label, dfsan_label s2_label,
                               dfsan_label n_label)

 DECLARE_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_strncmp, uptr caller_pc,
                               const char *s1, const char *s2, size_t n,
                               dfsan_label s1_label, dfsan_label s2_label,
                               dfsan_label n_label, dfsan_origin s1_origin,
                               dfsan_origin s2_origin, dfsan_origin n_origin)

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_strncmp(const char *s1, const char *s2,
                                                  size_t n, dfsan_label s1_label,
                                                  dfsan_label s2_label,
                                                  dfsan_label n_label,
                                                  dfsan_label *ret_label) {
   if (n == 0) {
     *ret_label = 0;
     return 0;
   }

   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_strncmp, GET_CALLER_PC(), s1, s2,
                              n, s1_label, s2_label, n_label);

   size_t bytes_read;
   int r = dfsan_strncmp(s1, s2, n, &bytes_read);
   *ret_label = dfsan_get_memcmp_label(s1, s2, bytes_read);
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_strncmp(
     const char *s1, const char *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label,
     dfsan_origin s1_origin, dfsan_origin s2_origin, dfsan_origin n_origin,
     dfsan_origin *ret_origin) {
   if (n == 0) {
     *ret_label = 0;
     return 0;
   }

   CALL_WEAK_INTERCEPTOR_HOOK(dfsan_weak_hook_origin_strncmp, GET_CALLER_PC(),
                              s1, s2, n, s1_label, s2_label, n_label, s1_origin,
                              s2_origin, n_origin);

   size_t bytes_read;
   int r = dfsan_strncmp(s1, s2, n, &bytes_read);
   dfsan_get_memcmp_origin(s1, s2, bytes_read, ret_label, ret_origin);
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_strncasecmp(
     const char *s1, const char *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label) {
   if (n == 0) {
     *ret_label = 0;
     return 0;
   }

   size_t bytes_read;
   int r = dfsan_strncasecmp(s1, s2, n, &bytes_read);
   *ret_label = dfsan_get_memcmp_label(s1, s2, bytes_read);
   return r;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_strncasecmp(
     const char *s1, const char *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label,
     dfsan_origin s1_origin, dfsan_origin s2_origin, dfsan_origin n_origin,
     dfsan_origin *ret_origin) {
   if (n == 0) {
     *ret_label = 0;
     return 0;
   }

   size_t bytes_read;
   int r = dfsan_strncasecmp(s1, s2, n, &bytes_read);
   dfsan_get_memcmp_origin(s1, s2, bytes_read, ret_label, ret_origin);
   return r;
 }


 SANITIZER_INTERFACE_ATTRIBUTE size_t
 __dfsw_strlen(const char *s, dfsan_label s_label, dfsan_label *ret_label) {
   size_t ret = strlen(s);
   if (flags().strict_data_dependencies) {
     *ret_label = 0;
   } else {
     *ret_label = dfsan_read_label(s, ret + 1);
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE size_t __dfso_strlen(const char *s,
                                                    dfsan_label s_label,
                                                    dfsan_label *ret_label,
                                                    dfsan_origin s_origin,
                                                    dfsan_origin *ret_origin) {
   size_t ret = __dfsw_strlen(s, s_label, ret_label);
   if (!flags().strict_data_dependencies)
     *ret_origin = dfsan_read_origin_of_first_taint(s, ret + 1);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE size_t __dfsw_strnlen(const char *s,
                                                     size_t maxlen,
                                                     dfsan_label s_label,
                                                     dfsan_label maxlen_label,
                                                     dfsan_label *ret_label) {
   size_t ret = strnlen(s, maxlen);
   if (flags().strict_data_dependencies) {
     *ret_label = 0;
   } else {
     size_t full_len = strlen(s);
     size_t covered_len = maxlen > (full_len + 1) ? (full_len + 1) : maxlen;
     *ret_label = dfsan_union(maxlen_label, dfsan_read_label(s, covered_len));
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE size_t __dfso_strnlen(
     const char *s, size_t maxlen, dfsan_label s_label, dfsan_label maxlen_label,
     dfsan_label *ret_label, dfsan_origin s_origin, dfsan_origin maxlen_origin,
     dfsan_origin *ret_origin) {
   size_t ret = __dfsw_strnlen(s, maxlen, s_label, maxlen_label, ret_label);
   if (!flags().strict_data_dependencies) {
     size_t full_len = strlen(s);
     size_t covered_len = maxlen > (full_len + 1) ? (full_len + 1) : maxlen;
     dfsan_origin o = dfsan_read_origin_of_first_taint(s, covered_len);
     *ret_origin = o ? o : maxlen_origin;
   }
   return ret;
 }

 static void *dfsan_memmove(void *dest, const void *src, size_t n) {
   dfsan_label *sdest = shadow_for(dest);
   const dfsan_label *ssrc = shadow_for(src);
   internal_memmove((void *)sdest, (const void *)ssrc, n * sizeof(dfsan_label));
   return internal_memmove(dest, src, n);
 }

 static void *dfsan_memmove_with_origin(void *dest, const void *src, size_t n) {
   dfsan_mem_origin_transfer(dest, src, n);
   return dfsan_memmove(dest, src, n);
 }

 static void *dfsan_memcpy(void *dest, const void *src, size_t n) {
   dfsan_mem_shadow_transfer(dest, src, n);
   return internal_memcpy(dest, src, n);
 }

 static void *dfsan_memcpy_with_origin(void *dest, const void *src, size_t n) {
   dfsan_mem_origin_transfer(dest, src, n);
   return dfsan_memcpy(dest, src, n);
 }

 static void dfsan_memset(void *s, int c, dfsan_label c_label, size_t n) {
   internal_memset(s, c, n);
   dfsan_set_label(c_label, s, n);
 }

 static void dfsan_memset_with_origin(void *s, int c, dfsan_label c_label,
                                      dfsan_origin c_origin, size_t n) {
   internal_memset(s, c, n);
   dfsan_set_label_origin(c_label, c_origin, s, n);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfsw_memcpy(void *dest, const void *src, size_t n,
                     dfsan_label dest_label, dfsan_label src_label,
                     dfsan_label n_label, dfsan_label *ret_label) {
   *ret_label = dest_label;
   return dfsan_memcpy(dest, src, n);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfso_memcpy(void *dest, const void *src, size_t n,
                     dfsan_label dest_label, dfsan_label src_label,
                     dfsan_label n_label, dfsan_label *ret_label,
                     dfsan_origin dest_origin, dfsan_origin src_origin,
                     dfsan_origin n_origin, dfsan_origin *ret_origin) {
   *ret_label = dest_label;
   *ret_origin = dest_origin;
   return dfsan_memcpy_with_origin(dest, src, n);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfsw_memmove(void *dest, const void *src, size_t n,
                      dfsan_label dest_label, dfsan_label src_label,
                      dfsan_label n_label, dfsan_label *ret_label) {
   *ret_label = dest_label;
   return dfsan_memmove(dest, src, n);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfso_memmove(void *dest, const void *src, size_t n,
                      dfsan_label dest_label, dfsan_label src_label,
                      dfsan_label n_label, dfsan_label *ret_label,
                      dfsan_origin dest_origin, dfsan_origin src_origin,
                      dfsan_origin n_origin, dfsan_origin *ret_origin) {
   *ret_label = dest_label;
   *ret_origin = dest_origin;
   return dfsan_memmove_with_origin(dest, src, n);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfsw_memset(void *s, int c, size_t n,
                     dfsan_label s_label, dfsan_label c_label,
                     dfsan_label n_label, dfsan_label *ret_label) {
   dfsan_memset(s, c, c_label, n);
   *ret_label = s_label;
   return s;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 void *__dfso_memset(void *s, int c, size_t n, dfsan_label s_label,
                     dfsan_label c_label, dfsan_label n_label,
                     dfsan_label *ret_label, dfsan_origin s_origin,
                     dfsan_origin c_origin, dfsan_origin n_origin,
                     dfsan_origin *ret_origin) {
   dfsan_memset_with_origin(s, c, c_label, c_origin, n);
   *ret_label = s_label;
   *ret_origin = s_origin;
   return s;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strcat(char *dest, const char *src,
                                                   dfsan_label dest_label,
                                                   dfsan_label src_label,
                                                   dfsan_label *ret_label) {
   size_t dest_len = strlen(dest);
   char *ret = strcat(dest, src);
   dfsan_mem_shadow_transfer(dest + dest_len, src, strlen(src));
   *ret_label = dest_label;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strcat(
     char *dest, const char *src, dfsan_label dest_label, dfsan_label src_label,
     dfsan_label *ret_label, dfsan_origin dest_origin, dfsan_origin src_origin,
     dfsan_origin *ret_origin) {
   size_t dest_len = strlen(dest);
   char *ret = strcat(dest, src);
   size_t src_len = strlen(src);
   dfsan_mem_origin_transfer(dest + dest_len, src, src_len);
   dfsan_mem_shadow_transfer(dest + dest_len, src, src_len);
   *ret_label = dest_label;
   *ret_origin = dest_origin;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *
 __dfsw_strdup(const char *s, dfsan_label s_label, dfsan_label *ret_label) {
   size_t len = strlen(s);
   void *p = malloc(len+1);
   dfsan_memcpy(p, s, len+1);
   *ret_label = 0;
   return static_cast<char *>(p);
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strdup(const char *s,
                                                   dfsan_label s_label,
                                                   dfsan_label *ret_label,
                                                   dfsan_origin s_origin,
                                                   dfsan_origin *ret_origin) {
   size_t len = strlen(s);
   void *p = malloc(len + 1);
   dfsan_memcpy_with_origin(p, s, len + 1);
   *ret_label = 0;
   return static_cast<char *>(p);
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *
 __dfsw_strncpy(char *s1, const char *s2, size_t n, dfsan_label s1_label,
                dfsan_label s2_label, dfsan_label n_label,
                dfsan_label *ret_label) {
   size_t len = strlen(s2);
   if (len < n) {
     dfsan_memcpy(s1, s2, len+1);
     dfsan_memset(s1+len+1, 0, 0, n-len-1);
   } else {
     dfsan_memcpy(s1, s2, n);
   }

   *ret_label = s1_label;
   return s1;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strncpy(
     char *s1, const char *s2, size_t n, dfsan_label s1_label,
     dfsan_label s2_label, dfsan_label n_label, dfsan_label *ret_label,
     dfsan_origin s1_origin, dfsan_origin s2_origin, dfsan_origin n_origin,
     dfsan_origin *ret_origin) {
   size_t len = strlen(s2);
   if (len < n) {
     dfsan_memcpy_with_origin(s1, s2, len + 1);
     dfsan_memset_with_origin(s1 + len + 1, 0, 0, 0, n - len - 1);
   } else {
     dfsan_memcpy_with_origin(s1, s2, n);
   }

   *ret_label = s1_label;
   *ret_origin = s1_origin;
   return s1;
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t
 __dfsw_pread(int fd, void *buf, size_t count, off_t offset,
              dfsan_label fd_label, dfsan_label buf_label,
              dfsan_label count_label, dfsan_label offset_label,
              dfsan_label *ret_label) {
   ssize_t ret = pread(fd, buf, count, offset);
   if (ret > 0)
     dfsan_set_label(0, buf, ret);
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t __dfso_pread(
     int fd, void *buf, size_t count, off_t offset, dfsan_label fd_label,
     dfsan_label buf_label, dfsan_label count_label, dfsan_label offset_label,
     dfsan_label *ret_label, dfsan_origin fd_origin, dfsan_origin buf_origin,
     dfsan_origin count_origin, dfsan_label offset_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_pread(fd, buf, count, offset, fd_label, buf_label, count_label,
                       offset_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t
 __dfsw_read(int fd, void *buf, size_t count,
              dfsan_label fd_label, dfsan_label buf_label,
              dfsan_label count_label,
              dfsan_label *ret_label) {
   ssize_t ret = read(fd, buf, count);
   if (ret > 0)
     dfsan_set_label(0, buf, ret);
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t __dfso_read(
     int fd, void *buf, size_t count, dfsan_label fd_label,
     dfsan_label buf_label, dfsan_label count_label, dfsan_label *ret_label,
     dfsan_origin fd_origin, dfsan_origin buf_origin, dfsan_origin count_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_read(fd, buf, count, fd_label, buf_label, count_label,
                      ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_clock_gettime(clockid_t clk_id,
                                                        struct timespec *tp,
                                                        dfsan_label clk_id_label,
                                                        dfsan_label tp_label,
                                                        dfsan_label *ret_label) {
   int ret = clock_gettime(clk_id, tp);
   if (ret == 0)
     dfsan_set_label(0, tp, sizeof(struct timespec));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_clock_gettime(
     clockid_t clk_id, struct timespec *tp, dfsan_label clk_id_label,
     dfsan_label tp_label, dfsan_label *ret_label, dfsan_origin clk_id_origin,
     dfsan_origin tp_origin, dfsan_origin *ret_origin) {
   return __dfsw_clock_gettime(clk_id, tp, clk_id_label, tp_label, ret_label);
 }

 static void dfsan_set_zero_label(const void *ptr, uptr size) {
   dfsan_set_label(0, const_cast<void *>(ptr), size);
 }

 // dlopen() ultimately calls mmap() down inside the loader, which generally
 // doesn't participate in dynamic symbol resolution.  Therefore we won't
 // intercept its calls to mmap, and we have to hook it here.
 SANITIZER_INTERFACE_ATTRIBUTE void *
 __dfsw_dlopen(const char *filename, int flag, dfsan_label filename_label,
               dfsan_label flag_label, dfsan_label *ret_label) {
   void *handle = dlopen(filename, flag);
   link_map *map = GET_LINK_MAP_BY_DLOPEN_HANDLE(handle);
   if (map)
     ForEachMappedRegion(map, dfsan_set_zero_label);
   *ret_label = 0;
   return handle;
 }

 SANITIZER_INTERFACE_ATTRIBUTE void *__dfso_dlopen(
     const char *filename, int flag, dfsan_label filename_label,
     dfsan_label flag_label, dfsan_label *ret_label,
     dfsan_origin filename_origin, dfsan_origin flag_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_dlopen(filename, flag, filename_label, flag_label, ret_label);
 }

 static void *DFsanThreadStartFunc(void *arg) {
   DFsanThread *t = (DFsanThread *)arg;
   SetCurrentThread(t);
   t->Init();
   SetSigProcMask(&t->starting_sigset_, nullptr);
   return t->ThreadStart();
 }

 static int dfsan_pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                                 void *start_routine, void *arg,
                                 dfsan_label *ret_label,
                                 bool track_origins = false) {
   pthread_attr_t myattr;
   if (!attr) {
     pthread_attr_init(&myattr);
     attr = &myattr;
   }

   // Ensure that the thread stack is large enough to hold all TLS data.
   AdjustStackSize((void *)(const_cast<pthread_attr_t *>(attr)));

   DFsanThread *t =
       DFsanThread::Create((thread_callback_t)start_routine, arg, track_origins);
   ScopedBlockSignals block(&t->starting_sigset_);
   int res = pthread_create(thread, attr, DFsanThreadStartFunc, t);

   if (attr == &myattr)
     pthread_attr_destroy(&myattr);
   *ret_label = 0;
   return res;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_pthread_create(
     pthread_t *thread, const pthread_attr_t *attr, void *start_routine,
     void *arg, dfsan_label thread_label, dfsan_label attr_label,
     dfsan_label start_routine_label, dfsan_label arg_label,
     dfsan_label *ret_label) {
   return dfsan_pthread_create(thread, attr, start_routine, arg, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_pthread_create(
     pthread_t *thread, const pthread_attr_t *attr, void *start_routine,
     void *arg, dfsan_label thread_label, dfsan_label attr_label,
     dfsan_label start_routine_label, dfsan_label arg_label,
     dfsan_label *ret_label, dfsan_origin thread_origin,
     dfsan_origin attr_origin, dfsan_origin start_routine_origin,
     dfsan_origin arg_origin, dfsan_origin *ret_origin) {
   return dfsan_pthread_create(thread, attr, start_routine, arg, ret_label,
                               true);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_pthread_join(pthread_t thread,
                                                       void **retval,
                                                       dfsan_label thread_label,
                                                       dfsan_label retval_label,
                                                       dfsan_label *ret_label) {
   int ret = pthread_join(thread, retval);
   if (ret == 0 && retval)
     dfsan_set_label(0, retval, sizeof(*retval));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_pthread_join(
     pthread_t thread, void **retval, dfsan_label thread_label,
     dfsan_label retval_label, dfsan_label *ret_label,
     dfsan_origin thread_origin, dfsan_origin retval_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_pthread_join(thread, retval, thread_label, retval_label,
                              ret_label);
 }

 struct dl_iterate_phdr_info {
   int (*callback)(struct dl_phdr_info *info, size_t size, void *data);
   void *data;
 };

 int dl_iterate_phdr_cb(struct dl_phdr_info *info, size_t size, void *data) {
   dl_iterate_phdr_info *dipi = (dl_iterate_phdr_info *)data;
   dfsan_set_label(0, *info);
   dfsan_set_label(0, const_cast<char *>(info->dlpi_name),
                   strlen(info->dlpi_name) + 1);
   dfsan_set_label(
       0, const_cast<char *>(reinterpret_cast<const char *>(info->dlpi_phdr)),
       sizeof(*info->dlpi_phdr) * info->dlpi_phnum);

   dfsan_clear_thread_local_state();
   return dipi->callback(info, size, dipi->data);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_dl_iterate_phdr(
     int (*callback)(struct dl_phdr_info *info, size_t size, void *data),
     void *data, dfsan_label callback_label, dfsan_label data_label,
     dfsan_label *ret_label) {
   dl_iterate_phdr_info dipi = {callback, data};
   *ret_label = 0;
   return dl_iterate_phdr(dl_iterate_phdr_cb, &dipi);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_dl_iterate_phdr(
     int (*callback)(struct dl_phdr_info *info, size_t size, void *data),
     void *data, dfsan_label callback_label, dfsan_label data_label,
     dfsan_label *ret_label, dfsan_origin callback_origin,
     dfsan_origin data_origin, dfsan_origin *ret_origin) {
   dl_iterate_phdr_info dipi = {callback, data};
   *ret_label = 0;
   return dl_iterate_phdr(dl_iterate_phdr_cb, &dipi);
 }

 // This function is only available for glibc 2.27 or newer.  Mark it weak so
 // linking succeeds with older glibcs.
 SANITIZER_WEAK_ATTRIBUTE void _dl_get_tls_static_info(size_t *sizep,
                                                       size_t *alignp);

 SANITIZER_INTERFACE_ATTRIBUTE void __dfsw__dl_get_tls_static_info(
     size_t *sizep, size_t *alignp, dfsan_label sizep_label,
     dfsan_label alignp_label) {
   assert(_dl_get_tls_static_info);
   _dl_get_tls_static_info(sizep, alignp);
   dfsan_set_label(0, sizep, sizeof(*sizep));
   dfsan_set_label(0, alignp, sizeof(*alignp));
 }

 SANITIZER_INTERFACE_ATTRIBUTE void __dfso__dl_get_tls_static_info(
     size_t *sizep, size_t *alignp, dfsan_label sizep_label,
     dfsan_label alignp_label, dfsan_origin sizep_origin,
     dfsan_origin alignp_origin) {
   __dfsw__dl_get_tls_static_info(sizep, alignp, sizep_label, alignp_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_ctime_r(const time_t *timep, char *buf, dfsan_label timep_label,
                      dfsan_label buf_label, dfsan_label *ret_label) {
   char *ret = ctime_r(timep, buf);
   if (ret) {
     dfsan_set_label(dfsan_read_label(timep, sizeof(time_t)), buf,
                     strlen(buf) + 1);
     *ret_label = buf_label;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_ctime_r(const time_t *timep, char *buf, dfsan_label timep_label,
                      dfsan_label buf_label, dfsan_label *ret_label,
                      dfsan_origin timep_origin, dfsan_origin buf_origin,
                      dfsan_origin *ret_origin) {
   char *ret = ctime_r(timep, buf);
   if (ret) {
     dfsan_set_label_origin(
         dfsan_read_label(timep, sizeof(time_t)),
         dfsan_read_origin_of_first_taint(timep, sizeof(time_t)), buf,
         strlen(buf) + 1);
     *ret_label = buf_label;
     *ret_origin = buf_origin;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_fgets(char *s, int size, FILE *stream, dfsan_label s_label,
                    dfsan_label size_label, dfsan_label stream_label,
                    dfsan_label *ret_label) {
   char *ret = fgets(s, size, stream);
   if (ret) {
     dfsan_set_label(0, ret, strlen(ret) + 1);
     *ret_label = s_label;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_fgets(char *s, int size, FILE *stream, dfsan_label s_label,
                    dfsan_label size_label, dfsan_label stream_label,
                    dfsan_label *ret_label, dfsan_origin s_origin,
                    dfsan_origin size_origin, dfsan_origin stream_origin,
                    dfsan_origin *ret_origin) {
   char *ret = __dfsw_fgets(s, size, stream, s_label, size_label, stream_label,
                            ret_label);
   if (ret)
     *ret_origin = s_origin;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_getcwd(char *buf, size_t size, dfsan_label buf_label,
                     dfsan_label size_label, dfsan_label *ret_label) {
   char *ret = getcwd(buf, size);
   if (ret) {
     dfsan_set_label(0, ret, strlen(ret) + 1);
     *ret_label = buf_label;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_getcwd(char *buf, size_t size, dfsan_label buf_label,
                     dfsan_label size_label, dfsan_label *ret_label,
                     dfsan_origin buf_origin, dfsan_origin size_origin,
                     dfsan_origin *ret_origin) {
   char *ret = __dfsw_getcwd(buf, size, buf_label, size_label, ret_label);
   if (ret)
     *ret_origin = buf_origin;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_get_current_dir_name(dfsan_label *ret_label) {
   char *ret = get_current_dir_name();
   if (ret)
     dfsan_set_label(0, ret, strlen(ret) + 1);
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_get_current_dir_name(dfsan_label *ret_label,
                                   dfsan_origin *ret_origin) {
   return __dfsw_get_current_dir_name(ret_label);
 }

 // This function is only available for glibc 2.25 or newer.  Mark it weak so
 // linking succeeds with older glibcs.
 SANITIZER_WEAK_ATTRIBUTE int getentropy(void *buffer, size_t length);

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getentropy(void *buffer, size_t length,
                                                     dfsan_label buffer_label,
                                                     dfsan_label length_label,
                                                     dfsan_label *ret_label) {
   int ret = getentropy(buffer, length);
   if (ret == 0) {
     dfsan_set_label(0, buffer, length);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_getentropy(void *buffer, size_t length,
                                                     dfsan_label buffer_label,
                                                     dfsan_label length_label,
                                                     dfsan_label *ret_label,
                                                     dfsan_origin buffer_origin,
                                                     dfsan_origin length_origin,
                                                     dfsan_origin *ret_origin) {
   return __dfsw_getentropy(buffer, length, buffer_label, length_label,
                            ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_gethostname(char *name, size_t len, dfsan_label name_label,
                        dfsan_label len_label, dfsan_label *ret_label) {
   int ret = gethostname(name, len);
   if (ret == 0) {
     dfsan_set_label(0, name, strlen(name) + 1);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_gethostname(char *name, size_t len, dfsan_label name_label,
                        dfsan_label len_label, dfsan_label *ret_label,
                        dfsan_origin name_origin, dfsan_origin len_origin,
                        dfsan_label *ret_origin) {
   return __dfsw_gethostname(name, len, name_label, len_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_getrlimit(int resource, struct rlimit *rlim,
                      dfsan_label resource_label, dfsan_label rlim_label,
                      dfsan_label *ret_label) {
   int ret = getrlimit(resource, rlim);
   if (ret == 0) {
     dfsan_set_label(0, rlim, sizeof(struct rlimit));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_getrlimit(int resource, struct rlimit *rlim,
                      dfsan_label resource_label, dfsan_label rlim_label,
                      dfsan_label *ret_label, dfsan_origin resource_origin,
                      dfsan_origin rlim_origin, dfsan_origin *ret_origin) {
   return __dfsw_getrlimit(resource, rlim, resource_label, rlim_label,
                           ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_getrusage(int who, struct rusage *usage, dfsan_label who_label,
                      dfsan_label usage_label, dfsan_label *ret_label) {
   int ret = getrusage(who, usage);
   if (ret == 0) {
     dfsan_set_label(0, usage, sizeof(struct rusage));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_getrusage(int who, struct rusage *usage, dfsan_label who_label,
                      dfsan_label usage_label, dfsan_label *ret_label,
                      dfsan_origin who_origin, dfsan_origin usage_origin,
                      dfsan_label *ret_origin) {
   return __dfsw_getrusage(who, usage, who_label, usage_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfsw_strcpy(char *dest, const char *src, dfsan_label dst_label,
                     dfsan_label src_label, dfsan_label *ret_label) {
   char *ret = strcpy(dest, src);
   if (ret) {
     dfsan_mem_shadow_transfer(dest, src, strlen(src) + 1);
   }
   *ret_label = dst_label;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 char *__dfso_strcpy(char *dest, const char *src, dfsan_label dst_label,
                     dfsan_label src_label, dfsan_label *ret_label,
                     dfsan_origin dst_origin, dfsan_origin src_origin,
                     dfsan_origin *ret_origin) {
   char *ret = strcpy(dest, src);
   if (ret) {
     size_t str_len = strlen(src) + 1;
     dfsan_mem_origin_transfer(dest, src, str_len);
     dfsan_mem_shadow_transfer(dest, src, str_len);
   }
   *ret_label = dst_label;
   *ret_origin = dst_origin;
   return ret;
 }

 static long int dfsan_strtol(const char *nptr, char **endptr, int base,
                              char **tmp_endptr) {
   assert(tmp_endptr);
   long int ret = strtol(nptr, tmp_endptr, base);
   if (endptr)
     *endptr = *tmp_endptr;
   return ret;
 }

 static void dfsan_strtolong_label(const char *nptr, const char *tmp_endptr,
                                   dfsan_label base_label,
                                   dfsan_label *ret_label) {
   if (tmp_endptr > nptr) {
     // If *tmp_endptr is '\0' include its label as well.
     *ret_label = dfsan_union(
         base_label,
         dfsan_read_label(nptr, tmp_endptr - nptr + (*tmp_endptr ? 0 : 1)));
   } else {
     *ret_label = 0;
   }
 }

 static void dfsan_strtolong_origin(const char *nptr, const char *tmp_endptr,
                                    dfsan_label base_label,
                                    dfsan_label *ret_label,
                                    dfsan_origin base_origin,
                                    dfsan_origin *ret_origin) {
   if (tmp_endptr > nptr) {
     // When multiple inputs are tainted, we propagate one of its origins.
     // Because checking if base_label is tainted does not need additional
     // computation, we prefer to propagating base_origin.
     *ret_origin = base_label
                       ? base_origin
                       : dfsan_read_origin_of_first_taint(
                             nptr, tmp_endptr - nptr + (*tmp_endptr ? 0 : 1));
   }
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long int __dfsw_strtol(const char *nptr, char **endptr, int base,
                        dfsan_label nptr_label, dfsan_label endptr_label,
                        dfsan_label base_label, dfsan_label *ret_label) {
   char *tmp_endptr;
   long int ret = dfsan_strtol(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long int __dfso_strtol(const char *nptr, char **endptr, int base,
                        dfsan_label nptr_label, dfsan_label endptr_label,
                        dfsan_label base_label, dfsan_label *ret_label,
                        dfsan_origin nptr_origin, dfsan_origin endptr_origin,
                        dfsan_origin base_origin, dfsan_origin *ret_origin) {
   char *tmp_endptr;
   long int ret = dfsan_strtol(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   dfsan_strtolong_origin(nptr, tmp_endptr, base_label, ret_label, base_origin,
                          ret_origin);
   return ret;
 }

 static double dfsan_strtod(const char *nptr, char **endptr, char **tmp_endptr) {
   assert(tmp_endptr);
   double ret = strtod(nptr, tmp_endptr);
   if (endptr)
     *endptr = *tmp_endptr;
   return ret;
 }

 static void dfsan_strtod_label(const char *nptr, const char *tmp_endptr,
                                dfsan_label *ret_label) {
   if (tmp_endptr > nptr) {
     // If *tmp_endptr is '\0' include its label as well.
     *ret_label = dfsan_read_label(
         nptr,
         tmp_endptr - nptr + (*tmp_endptr ? 0 : 1));
   } else {
     *ret_label = 0;
   }
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 double __dfsw_strtod(const char *nptr, char **endptr, dfsan_label nptr_label,
                      dfsan_label endptr_label, dfsan_label *ret_label) {
   char *tmp_endptr;
   double ret = dfsan_strtod(nptr, endptr, &tmp_endptr);
   dfsan_strtod_label(nptr, tmp_endptr, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 double __dfso_strtod(const char *nptr, char **endptr, dfsan_label nptr_label,
                      dfsan_label endptr_label, dfsan_label *ret_label,
                      dfsan_origin nptr_origin, dfsan_origin endptr_origin,
                      dfsan_origin *ret_origin) {
   char *tmp_endptr;
   double ret = dfsan_strtod(nptr, endptr, &tmp_endptr);
   dfsan_strtod_label(nptr, tmp_endptr, ret_label);
   if (tmp_endptr > nptr) {
     // If *tmp_endptr is '\0' include its label as well.
     *ret_origin = dfsan_read_origin_of_first_taint(
         nptr, tmp_endptr - nptr + (*tmp_endptr ? 0 : 1));
   } else {
     *ret_origin = 0;
   }
   return ret;
 }

 static long long int dfsan_strtoll(const char *nptr, char **endptr, int base,
                                    char **tmp_endptr) {
   assert(tmp_endptr);
   long long int ret = strtoll(nptr, tmp_endptr, base);
   if (endptr)
     *endptr = *tmp_endptr;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long long int __dfsw_strtoll(const char *nptr, char **endptr, int base,
                              dfsan_label nptr_label, dfsan_label endptr_label,
                              dfsan_label base_label, dfsan_label *ret_label) {
   char *tmp_endptr;
   long long int ret = dfsan_strtoll(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long long int __dfso_strtoll(const char *nptr, char **endptr, int base,
                              dfsan_label nptr_label, dfsan_label endptr_label,
                              dfsan_label base_label, dfsan_label *ret_label,
                              dfsan_origin nptr_origin,
                              dfsan_origin endptr_origin,
                              dfsan_origin base_origin,
                              dfsan_origin *ret_origin) {
   char *tmp_endptr;
   long long int ret = dfsan_strtoll(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   dfsan_strtolong_origin(nptr, tmp_endptr, base_label, ret_label, base_origin,
                          ret_origin);
   return ret;
 }

 static unsigned long int dfsan_strtoul(const char *nptr, char **endptr,
                                        int base, char **tmp_endptr) {
   assert(tmp_endptr);
   unsigned long int ret = strtoul(nptr, tmp_endptr, base);
   if (endptr)
     *endptr = *tmp_endptr;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 unsigned long int __dfsw_strtoul(const char *nptr, char **endptr, int base,
                        dfsan_label nptr_label, dfsan_label endptr_label,
                        dfsan_label base_label, dfsan_label *ret_label) {
   char *tmp_endptr;
   unsigned long int ret = dfsan_strtoul(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 unsigned long int __dfso_strtoul(
     const char *nptr, char **endptr, int base, dfsan_label nptr_label,
     dfsan_label endptr_label, dfsan_label base_label, dfsan_label *ret_label,
     dfsan_origin nptr_origin, dfsan_origin endptr_origin,
     dfsan_origin base_origin, dfsan_origin *ret_origin) {
   char *tmp_endptr;
   unsigned long int ret = dfsan_strtoul(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   dfsan_strtolong_origin(nptr, tmp_endptr, base_label, ret_label, base_origin,
                          ret_origin);
   return ret;
 }

 static long long unsigned int dfsan_strtoull(const char *nptr, char **endptr,
                                              int base, char **tmp_endptr) {
   assert(tmp_endptr);
   long long unsigned int ret = strtoull(nptr, tmp_endptr, base);
   if (endptr)
     *endptr = *tmp_endptr;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long long unsigned int __dfsw_strtoull(const char *nptr, char **endptr,
                                        int base, dfsan_label nptr_label,
                                        dfsan_label endptr_label,
                                        dfsan_label base_label,
                                        dfsan_label *ret_label) {
   char *tmp_endptr;
   long long unsigned int ret = dfsan_strtoull(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 long long unsigned int __dfso_strtoull(
     const char *nptr, char **endptr, int base, dfsan_label nptr_label,
     dfsan_label endptr_label, dfsan_label base_label, dfsan_label *ret_label,
     dfsan_origin nptr_origin, dfsan_origin endptr_origin,
     dfsan_origin base_origin, dfsan_origin *ret_origin) {
   char *tmp_endptr;
   long long unsigned int ret = dfsan_strtoull(nptr, endptr, base, &tmp_endptr);
   dfsan_strtolong_label(nptr, tmp_endptr, base_label, ret_label);
   dfsan_strtolong_origin(nptr, tmp_endptr, base_label, ret_label, base_origin,
                          ret_origin);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 time_t __dfsw_time(time_t *t, dfsan_label t_label, dfsan_label *ret_label) {
   time_t ret = time(t);
   if (ret != (time_t) -1 && t) {
     dfsan_set_label(0, t, sizeof(time_t));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 time_t __dfso_time(time_t *t, dfsan_label t_label, dfsan_label *ret_label,
                    dfsan_origin t_origin, dfsan_origin *ret_origin) {
   return __dfsw_time(t, t_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_inet_pton(int af, const char *src, void *dst, dfsan_label af_label,
                      dfsan_label src_label, dfsan_label dst_label,
                      dfsan_label *ret_label) {
   int ret = inet_pton(af, src, dst);
   if (ret == 1) {
     dfsan_set_label(dfsan_read_label(src, strlen(src) + 1), dst,
                     af == AF_INET ? sizeof(struct in_addr) : sizeof(in6_addr));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_inet_pton(int af, const char *src, void *dst, dfsan_label af_label,
                      dfsan_label src_label, dfsan_label dst_label,
                      dfsan_label *ret_label, dfsan_origin af_origin,
                      dfsan_origin src_origin, dfsan_origin dst_origin,
                      dfsan_origin *ret_origin) {
   int ret = inet_pton(af, src, dst);
   if (ret == 1) {
     int src_len = strlen(src) + 1;
     dfsan_set_label_origin(
         dfsan_read_label(src, src_len),
         dfsan_read_origin_of_first_taint(src, src_len), dst,
         af == AF_INET ? sizeof(struct in_addr) : sizeof(in6_addr));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 struct tm *__dfsw_localtime_r(const time_t *timep, struct tm *result,
                               dfsan_label timep_label, dfsan_label result_label,
                               dfsan_label *ret_label) {
   struct tm *ret = localtime_r(timep, result);
   if (ret) {
     dfsan_set_label(dfsan_read_label(timep, sizeof(time_t)), result,
                     sizeof(struct tm));
     *ret_label = result_label;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 struct tm *__dfso_localtime_r(const time_t *timep, struct tm *result,
                               dfsan_label timep_label, dfsan_label result_label,
                               dfsan_label *ret_label, dfsan_origin timep_origin,
                               dfsan_origin result_origin,
                               dfsan_origin *ret_origin) {
   struct tm *ret = localtime_r(timep, result);
   if (ret) {
     dfsan_set_label_origin(
         dfsan_read_label(timep, sizeof(time_t)),
         dfsan_read_origin_of_first_taint(timep, sizeof(time_t)), result,
         sizeof(struct tm));
     *ret_label = result_label;
     *ret_origin = result_origin;
   } else {
     *ret_label = 0;
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_getpwuid_r(id_t uid, struct passwd *pwd,
                       char *buf, size_t buflen, struct passwd **result,
                       dfsan_label uid_label, dfsan_label pwd_label,
                       dfsan_label buf_label, dfsan_label buflen_label,
                       dfsan_label result_label, dfsan_label *ret_label) {
   // Store the data in pwd, the strings referenced from pwd in buf, and the
   // address of pwd in *result.  On failure, NULL is stored in *result.
   int ret = getpwuid_r(uid, pwd, buf, buflen, result);
   if (ret == 0) {
     dfsan_set_label(0, pwd, sizeof(struct passwd));
     dfsan_set_label(0, buf, strlen(buf) + 1);
   }
   *ret_label = 0;
   dfsan_set_label(0, result, sizeof(struct passwd*));
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_getpwuid_r(id_t uid, struct passwd *pwd, char *buf, size_t buflen,
                       struct passwd **result, dfsan_label uid_label,
                       dfsan_label pwd_label, dfsan_label buf_label,
                       dfsan_label buflen_label, dfsan_label result_label,
                       dfsan_label *ret_label, dfsan_origin uid_origin,
                       dfsan_origin pwd_origin, dfsan_origin buf_origin,
                       dfsan_origin buflen_origin, dfsan_origin result_origin,
                       dfsan_origin *ret_origin) {
   return __dfsw_getpwuid_r(uid, pwd, buf, buflen, result, uid_label, pwd_label,
                            buf_label, buflen_label, result_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_epoll_wait(int epfd, struct epoll_event *events, int maxevents,
                       int timeout, dfsan_label epfd_label,
                       dfsan_label events_label, dfsan_label maxevents_label,
                       dfsan_label timeout_label, dfsan_label *ret_label) {
   int ret = epoll_wait(epfd, events, maxevents, timeout);
   if (ret > 0)
     dfsan_set_label(0, events, ret * sizeof(*events));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_epoll_wait(int epfd, struct epoll_event *events, int maxevents,
                       int timeout, dfsan_label epfd_label,
                       dfsan_label events_label, dfsan_label maxevents_label,
                       dfsan_label timeout_label, dfsan_label *ret_label,
                       dfsan_origin epfd_origin, dfsan_origin events_origin,
                       dfsan_origin maxevents_origin,
                       dfsan_origin timeout_origin, dfsan_origin *ret_origin) {
   return __dfsw_epoll_wait(epfd, events, maxevents, timeout, epfd_label,
                            events_label, maxevents_label, timeout_label,
                            ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_poll(struct pollfd *fds, nfds_t nfds, int timeout,
                 dfsan_label dfs_label, dfsan_label nfds_label,
                 dfsan_label timeout_label, dfsan_label *ret_label) {
   int ret = poll(fds, nfds, timeout);
   if (ret >= 0) {
     for (; nfds > 0; --nfds) {
       dfsan_set_label(0, &fds[nfds - 1].revents, sizeof(fds[nfds - 1].revents));
     }
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_poll(struct pollfd *fds, nfds_t nfds, int timeout,
                 dfsan_label dfs_label, dfsan_label nfds_label,
                 dfsan_label timeout_label, dfsan_label *ret_label,
                 dfsan_origin dfs_origin, dfsan_origin nfds_origin,
                 dfsan_origin timeout_origin, dfsan_origin *ret_origin) {
   return __dfsw_poll(fds, nfds, timeout, dfs_label, nfds_label, timeout_label,
                      ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_select(int nfds, fd_set *readfds, fd_set *writefds,
                   fd_set *exceptfds, struct timeval *timeout,
                   dfsan_label nfds_label, dfsan_label readfds_label,
                   dfsan_label writefds_label, dfsan_label exceptfds_label,
                   dfsan_label timeout_label, dfsan_label *ret_label) {
   int ret = select(nfds, readfds, writefds, exceptfds, timeout);
   // Clear everything (also on error) since their content is either set or
   // undefined.
   if (readfds) {
     dfsan_set_label(0, readfds, sizeof(fd_set));
   }
   if (writefds) {
     dfsan_set_label(0, writefds, sizeof(fd_set));
   }
   if (exceptfds) {
     dfsan_set_label(0, exceptfds, sizeof(fd_set));
   }
   dfsan_set_label(0, timeout, sizeof(struct timeval));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_select(int nfds, fd_set *readfds, fd_set *writefds,
                   fd_set *exceptfds, struct timeval *timeout,
                   dfsan_label nfds_label, dfsan_label readfds_label,
                   dfsan_label writefds_label, dfsan_label exceptfds_label,
                   dfsan_label timeout_label, dfsan_label *ret_label,
                   dfsan_origin nfds_origin, dfsan_origin readfds_origin,
                   dfsan_origin writefds_origin, dfsan_origin exceptfds_origin,
                   dfsan_origin timeout_origin, dfsan_origin *ret_origin) {
   return __dfsw_select(nfds, readfds, writefds, exceptfds, timeout, nfds_label,
                        readfds_label, writefds_label, exceptfds_label,
                        timeout_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask,
                              dfsan_label pid_label,
                              dfsan_label cpusetsize_label,
                              dfsan_label mask_label, dfsan_label *ret_label) {
   int ret = sched_getaffinity(pid, cpusetsize, mask);
   if (ret == 0) {
     dfsan_set_label(0, mask, cpusetsize);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_sched_getaffinity(pid_t pid, size_t cpusetsize, cpu_set_t *mask,
                              dfsan_label pid_label,
                              dfsan_label cpusetsize_label,
                              dfsan_label mask_label, dfsan_label *ret_label,
                              dfsan_origin pid_origin,
                              dfsan_origin cpusetsize_origin,
                              dfsan_origin mask_origin,
                              dfsan_origin *ret_origin) {
   return __dfsw_sched_getaffinity(pid, cpusetsize, mask, pid_label,
                                   cpusetsize_label, mask_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sigemptyset(sigset_t *set, dfsan_label set_label,
                        dfsan_label *ret_label) {
   int ret = sigemptyset(set);
   dfsan_set_label(0, set, sizeof(sigset_t));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_sigemptyset(sigset_t *set, dfsan_label set_label,
                        dfsan_label *ret_label, dfsan_origin set_origin,
                        dfsan_origin *ret_origin) {
   return __dfsw_sigemptyset(set, set_label, ret_label);
 }

 class SignalHandlerScope {
  public:
   SignalHandlerScope() {
     if (DFsanThread *t = GetCurrentThread())
       t->EnterSignalHandler();
   }
   ~SignalHandlerScope() {
     if (DFsanThread *t = GetCurrentThread())
       t->LeaveSignalHandler();
   }
 };

 // Clear DFSan runtime TLS state at the end of a scope.
 //
 // Implementation must be async-signal-safe and use small data size, because
 // instances of this class may live on the signal handler stack.
 //
 // DFSan uses TLS to pass metadata of arguments and return values. When an
 // instrumented function accesses the TLS, if a signal callback happens, and the
 // callback calls other instrumented functions with updating the same TLS, the
 // TLS is in an inconsistent state after the callback ends. This may cause
 // either under-tainting or over-tainting.
 //
 // The current implementation simply resets TLS at restore. This prevents from
 // over-tainting. Although under-tainting may still happen, a taint flow can be
 // found eventually if we run a DFSan-instrumented program multiple times. The
 // alternative option is saving the entire TLS. However the TLS storage takes
 // 2k bytes, and signal calls could be nested. So it does not seem worth.
 class ScopedClearThreadLocalState {
  public:
   ScopedClearThreadLocalState() {}
   ~ScopedClearThreadLocalState() { dfsan_clear_thread_local_state(); }
 };

 // SignalSpinLocker::sigactions_mu guarantees atomicity of sigaction() calls.
 const int kMaxSignals = 1024;
 static atomic_uintptr_t sigactions[kMaxSignals];

 static void SignalHandler(int signo) {
   SignalHandlerScope signal_handler_scope;
   ScopedClearThreadLocalState scoped_clear_tls;

   // Clear shadows for all inputs provided by system.
   dfsan_clear_arg_tls(0, sizeof(dfsan_label));

   typedef void (*signal_cb)(int x);
   signal_cb cb =
       (signal_cb)atomic_load(&sigactions[signo], memory_order_relaxed);
   cb(signo);
 }

 static void SignalAction(int signo, siginfo_t *si, void *uc) {
   SignalHandlerScope signal_handler_scope;
   ScopedClearThreadLocalState scoped_clear_tls;

   // Clear shadows for all inputs provided by system. Similar to SignalHandler.
   dfsan_clear_arg_tls(0, 3 * sizeof(dfsan_label));
   dfsan_set_label(0, si, sizeof(*si));
   dfsan_set_label(0, uc, sizeof(ucontext_t));

   typedef void (*sigaction_cb)(int, siginfo_t *, void *);
   sigaction_cb cb =
       (sigaction_cb)atomic_load(&sigactions[signo], memory_order_relaxed);
   cb(signo, si, uc);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sigaction(int signum, const struct sigaction *act,
                      struct sigaction *oldact, dfsan_label signum_label,
                      dfsan_label act_label, dfsan_label oldact_label,
                      dfsan_label *ret_label) {
   CHECK_LT(signum, kMaxSignals);
   SignalSpinLocker lock;
   uptr old_cb = atomic_load(&sigactions[signum], memory_order_relaxed);
   struct sigaction new_act;
   struct sigaction *pnew_act = act ? &new_act : nullptr;
   if (act) {
     internal_memcpy(pnew_act, act, sizeof(struct sigaction));
     if (pnew_act->sa_flags & SA_SIGINFO) {
       uptr cb = (uptr)(pnew_act->sa_sigaction);
       if (cb != (uptr)SIG_IGN && cb != (uptr)SIG_DFL) {
         atomic_store(&sigactions[signum], cb, memory_order_relaxed);
         pnew_act->sa_sigaction = SignalAction;
       }
     } else {
       uptr cb = (uptr)(pnew_act->sa_handler);
       if (cb != (uptr)SIG_IGN && cb != (uptr)SIG_DFL) {
         atomic_store(&sigactions[signum], cb, memory_order_relaxed);
         pnew_act->sa_handler = SignalHandler;
       }
     }
   }

   int ret = sigaction(signum, pnew_act, oldact);

   if (ret == 0 && oldact) {
     if (oldact->sa_flags & SA_SIGINFO) {
       if (oldact->sa_sigaction == SignalAction)
         oldact->sa_sigaction = (decltype(oldact->sa_sigaction))old_cb;
     } else {
       if (oldact->sa_handler == SignalHandler)
         oldact->sa_handler = (decltype(oldact->sa_handler))old_cb;
     }
   }

   if (oldact) {
     dfsan_set_label(0, oldact, sizeof(struct sigaction));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_sigaction(int signum, const struct sigaction *act,
                      struct sigaction *oldact, dfsan_label signum_label,
                      dfsan_label act_label, dfsan_label oldact_label,
                      dfsan_label *ret_label, dfsan_origin signum_origin,
                      dfsan_origin act_origin, dfsan_origin oldact_origin,
                      dfsan_origin *ret_origin) {
   return __dfsw_sigaction(signum, act, oldact, signum_label, act_label,
                           oldact_label, ret_label);
 }

 static sighandler_t dfsan_signal(int signum, sighandler_t handler,
                                  dfsan_label *ret_label) {
   CHECK_LT(signum, kMaxSignals);
   SignalSpinLocker lock;
   uptr old_cb = atomic_load(&sigactions[signum], memory_order_relaxed);
   if (handler != SIG_IGN && handler != SIG_DFL) {
     atomic_store(&sigactions[signum], (uptr)handler, memory_order_relaxed);
     handler = &SignalHandler;
   }

   sighandler_t ret = signal(signum, handler);

   if (ret == SignalHandler)
     ret = (sighandler_t)old_cb;

   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 sighandler_t __dfsw_signal(int signum, sighandler_t handler,
                            dfsan_label signum_label, dfsan_label handler_label,
                            dfsan_label *ret_label) {
   return dfsan_signal(signum, handler, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 sighandler_t __dfso_signal(int signum, sighandler_t handler,
                            dfsan_label signum_label, dfsan_label handler_label,
                            dfsan_label *ret_label, dfsan_origin signum_origin,
                            dfsan_origin handler_origin,
                            dfsan_origin *ret_origin) {
   return dfsan_signal(signum, handler, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sigaltstack(const stack_t *ss, stack_t *old_ss, dfsan_label ss_label,
                        dfsan_label old_ss_label, dfsan_label *ret_label) {
   int ret = sigaltstack(ss, old_ss);
   if (ret != -1 && old_ss)
     dfsan_set_label(0, old_ss, sizeof(*old_ss));
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_sigaltstack(const stack_t *ss, stack_t *old_ss, dfsan_label ss_label,
                        dfsan_label old_ss_label, dfsan_label *ret_label,
                        dfsan_origin ss_origin, dfsan_origin old_ss_origin,
                        dfsan_origin *ret_origin) {
   return __dfsw_sigaltstack(ss, old_ss, ss_label, old_ss_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_gettimeofday(struct timeval *tv, struct timezone *tz,
                         dfsan_label tv_label, dfsan_label tz_label,
                         dfsan_label *ret_label) {
   int ret = gettimeofday(tv, tz);
   if (tv) {
     dfsan_set_label(0, tv, sizeof(struct timeval));
   }
   if (tz) {
     dfsan_set_label(0, tz, sizeof(struct timezone));
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_gettimeofday(struct timeval *tv, struct timezone *tz,
                         dfsan_label tv_label, dfsan_label tz_label,
                         dfsan_label *ret_label, dfsan_origin tv_origin,
                         dfsan_origin tz_origin, dfsan_origin *ret_origin) {
   return __dfsw_gettimeofday(tv, tz, tv_label, tz_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE void *__dfsw_memchr(void *s, int c, size_t n,
                                                   dfsan_label s_label,
                                                   dfsan_label c_label,
                                                   dfsan_label n_label,
                                                   dfsan_label *ret_label) {
   void *ret = memchr(s, c, n);
   if (flags().strict_data_dependencies) {
     *ret_label = ret ? s_label : 0;
   } else {
     size_t len =
         ret ? reinterpret_cast<char *>(ret) - reinterpret_cast<char *>(s) + 1
             : n;
     *ret_label =
         dfsan_union(dfsan_read_label(s, len), dfsan_union(s_label, c_label));
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE void *__dfso_memchr(
     void *s, int c, size_t n, dfsan_label s_label, dfsan_label c_label,
     dfsan_label n_label, dfsan_label *ret_label, dfsan_origin s_origin,
     dfsan_origin c_origin, dfsan_origin n_origin, dfsan_origin *ret_origin) {
   void *ret = __dfsw_memchr(s, c, n, s_label, c_label, n_label, ret_label);
   if (flags().strict_data_dependencies) {
     if (ret)
       *ret_origin = s_origin;
   } else {
     size_t len =
         ret ? reinterpret_cast<char *>(ret) - reinterpret_cast<char *>(s) + 1
             : n;
     dfsan_origin o = dfsan_read_origin_of_first_taint(s, len);
     *ret_origin = o ? o : (s_label ? s_origin : c_origin);
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strrchr(char *s, int c,
                                                    dfsan_label s_label,
                                                    dfsan_label c_label,
                                                    dfsan_label *ret_label) {
   char *ret = strrchr(s, c);
   if (flags().strict_data_dependencies) {
     *ret_label = ret ? s_label : 0;
   } else {
     *ret_label =
         dfsan_union(dfsan_read_label(s, strlen(s) + 1),
                     dfsan_union(s_label, c_label));
   }

   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strrchr(
     char *s, int c, dfsan_label s_label, dfsan_label c_label,
     dfsan_label *ret_label, dfsan_origin s_origin, dfsan_origin c_origin,
     dfsan_origin *ret_origin) {
   char *ret = __dfsw_strrchr(s, c, s_label, c_label, ret_label);
   if (flags().strict_data_dependencies) {
     if (ret)
       *ret_origin = s_origin;
   } else {
     size_t s_len = strlen(s) + 1;
     dfsan_origin o = dfsan_read_origin_of_first_taint(s, s_len);
     *ret_origin = o ? o : (s_label ? s_origin : c_origin);
   }

   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfsw_strstr(char *haystack, char *needle,
                                                   dfsan_label haystack_label,
                                                   dfsan_label needle_label,
                                                   dfsan_label *ret_label) {
   char *ret = strstr(haystack, needle);
   if (flags().strict_data_dependencies) {
     *ret_label = ret ? haystack_label : 0;
   } else {
     size_t len = ret ? ret + strlen(needle) - haystack : strlen(haystack) + 1;
     *ret_label =
         dfsan_union(dfsan_read_label(haystack, len),
                     dfsan_union(dfsan_read_label(needle, strlen(needle) + 1),
                                 dfsan_union(haystack_label, needle_label)));
   }

   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE char *__dfso_strstr(char *haystack, char *needle,
                                                   dfsan_label haystack_label,
                                                   dfsan_label needle_label,
                                                   dfsan_label *ret_label,
                                                   dfsan_origin haystack_origin,
                                                   dfsan_origin needle_origin,
                                                   dfsan_origin *ret_origin) {
   char *ret =
       __dfsw_strstr(haystack, needle, haystack_label, needle_label, ret_label);
   if (flags().strict_data_dependencies) {
     if (ret)
       *ret_origin = haystack_origin;
   } else {
     size_t needle_len = strlen(needle);
     size_t len = ret ? ret + needle_len - haystack : strlen(haystack) + 1;
     dfsan_origin o = dfsan_read_origin_of_first_taint(haystack, len);
     if (o) {
       *ret_origin = o;
     } else {
       o = dfsan_read_origin_of_first_taint(needle, needle_len + 1);
       *ret_origin = o ? o : (haystack_label ? haystack_origin : needle_origin);
     }
   }

   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_nanosleep(const struct timespec *req,
                                                    struct timespec *rem,
                                                    dfsan_label req_label,
                                                    dfsan_label rem_label,
                                                    dfsan_label *ret_label) {
   int ret = nanosleep(req, rem);
   *ret_label = 0;
   if (ret == -1) {
     // Interrupted by a signal, rem is filled with the remaining time.
     dfsan_set_label(0, rem, sizeof(struct timespec));
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_nanosleep(
     const struct timespec *req, struct timespec *rem, dfsan_label req_label,
     dfsan_label rem_label, dfsan_label *ret_label, dfsan_origin req_origin,
     dfsan_origin rem_origin, dfsan_origin *ret_origin) {
   return __dfsw_nanosleep(req, rem, req_label, rem_label, ret_label);
 }

 static void clear_msghdr_labels(size_t bytes_written, struct msghdr *msg) {
   dfsan_set_label(0, msg, sizeof(*msg));
   dfsan_set_label(0, msg->msg_name, msg->msg_namelen);
   dfsan_set_label(0, msg->msg_control, msg->msg_controllen);
   for (size_t i = 0; bytes_written > 0; ++i) {
     assert(i < msg->msg_iovlen);
     struct iovec *iov = &msg->msg_iov[i];
     size_t iov_written =
         bytes_written < iov->iov_len ? bytes_written : iov->iov_len;
     dfsan_set_label(0, iov->iov_base, iov_written);
     bytes_written -= iov_written;
   }
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_recvmmsg(
     int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags,
     struct timespec *timeout, dfsan_label sockfd_label,
     dfsan_label msgvec_label, dfsan_label vlen_label, dfsan_label flags_label,
     dfsan_label timeout_label, dfsan_label *ret_label) {
   int ret = recvmmsg(sockfd, msgvec, vlen, flags, timeout);
   for (int i = 0; i < ret; ++i) {
     dfsan_set_label(0, &msgvec[i].msg_len, sizeof(msgvec[i].msg_len));
     clear_msghdr_labels(msgvec[i].msg_len, &msgvec[i].msg_hdr);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_recvmmsg(
     int sockfd, struct mmsghdr *msgvec, unsigned int vlen, int flags,
     struct timespec *timeout, dfsan_label sockfd_label,
     dfsan_label msgvec_label, dfsan_label vlen_label, dfsan_label flags_label,
     dfsan_label timeout_label, dfsan_label *ret_label,
     dfsan_origin sockfd_origin, dfsan_origin msgvec_origin,
     dfsan_origin vlen_origin, dfsan_origin flags_origin,
     dfsan_origin timeout_origin, dfsan_origin *ret_origin) {
   return __dfsw_recvmmsg(sockfd, msgvec, vlen, flags, timeout, sockfd_label,
                          msgvec_label, vlen_label, flags_label, timeout_label,
                          ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t __dfsw_recvmsg(
     int sockfd, struct msghdr *msg, int flags, dfsan_label sockfd_label,
     dfsan_label msg_label, dfsan_label flags_label, dfsan_label *ret_label) {
   ssize_t ret = recvmsg(sockfd, msg, flags);
   if (ret >= 0)
     clear_msghdr_labels(ret, msg);
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE ssize_t __dfso_recvmsg(
     int sockfd, struct msghdr *msg, int flags, dfsan_label sockfd_label,
     dfsan_label msg_label, dfsan_label flags_label, dfsan_label *ret_label,
     dfsan_origin sockfd_origin, dfsan_origin msg_origin,
     dfsan_origin flags_origin, dfsan_origin *ret_origin) {
   return __dfsw_recvmsg(sockfd, msg, flags, sockfd_label, msg_label,
                         flags_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int
 __dfsw_socketpair(int domain, int type, int protocol, int sv[2],
                   dfsan_label domain_label, dfsan_label type_label,
                   dfsan_label protocol_label, dfsan_label sv_label,
                   dfsan_label *ret_label) {
   int ret = socketpair(domain, type, protocol, sv);
   *ret_label = 0;
   if (ret == 0) {
     dfsan_set_label(0, sv, sizeof(*sv) * 2);
   }
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_socketpair(
     int domain, int type, int protocol, int sv[2], dfsan_label domain_label,
     dfsan_label type_label, dfsan_label protocol_label, dfsan_label sv_label,
     dfsan_label *ret_label, dfsan_origin domain_origin,
     dfsan_origin type_origin, dfsan_origin protocol_origin,
     dfsan_origin sv_origin, dfsan_origin *ret_origin) {
   return __dfsw_socketpair(domain, type, protocol, sv, domain_label, type_label,
                            protocol_label, sv_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getsockopt(
     int sockfd, int level, int optname, void *optval, socklen_t *optlen,
     dfsan_label sockfd_label, dfsan_label level_label,
     dfsan_label optname_label, dfsan_label optval_label,
     dfsan_label optlen_label, dfsan_label *ret_label) {
   int ret = getsockopt(sockfd, level, optname, optval, optlen);
   if (ret != -1 && optval && optlen) {
     dfsan_set_label(0, optlen, sizeof(*optlen));
     dfsan_set_label(0, optval, *optlen);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_getsockopt(
     int sockfd, int level, int optname, void *optval, socklen_t *optlen,
     dfsan_label sockfd_label, dfsan_label level_label,
     dfsan_label optname_label, dfsan_label optval_label,
     dfsan_label optlen_label, dfsan_label *ret_label,
     dfsan_origin sockfd_origin, dfsan_origin level_origin,
     dfsan_origin optname_origin, dfsan_origin optval_origin,
     dfsan_origin optlen_origin, dfsan_origin *ret_origin) {
   return __dfsw_getsockopt(sockfd, level, optname, optval, optlen, sockfd_label,
                            level_label, optname_label, optval_label,
                            optlen_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getsockname(
     int sockfd, struct sockaddr *addr, socklen_t *addrlen,
     dfsan_label sockfd_label, dfsan_label addr_label, dfsan_label addrlen_label,
     dfsan_label *ret_label) {
   socklen_t origlen = addrlen ? *addrlen : 0;
   int ret = getsockname(sockfd, addr, addrlen);
   if (ret != -1 && addr && addrlen) {
     socklen_t written_bytes = origlen < *addrlen ? origlen : *addrlen;
     dfsan_set_label(0, addrlen, sizeof(*addrlen));
     dfsan_set_label(0, addr, written_bytes);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_getsockname(
     int sockfd, struct sockaddr *addr, socklen_t *addrlen,
     dfsan_label sockfd_label, dfsan_label addr_label, dfsan_label addrlen_label,
     dfsan_label *ret_label, dfsan_origin sockfd_origin,
     dfsan_origin addr_origin, dfsan_origin addrlen_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_getsockname(sockfd, addr, addrlen, sockfd_label, addr_label,
                             addrlen_label, ret_label);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfsw_getpeername(
     int sockfd, struct sockaddr *addr, socklen_t *addrlen,
     dfsan_label sockfd_label, dfsan_label addr_label, dfsan_label addrlen_label,
     dfsan_label *ret_label) {
   socklen_t origlen = addrlen ? *addrlen : 0;
   int ret = getpeername(sockfd, addr, addrlen);
   if (ret != -1 && addr && addrlen) {
     socklen_t written_bytes = origlen < *addrlen ? origlen : *addrlen;
     dfsan_set_label(0, addrlen, sizeof(*addrlen));
     dfsan_set_label(0, addr, written_bytes);
   }
   *ret_label = 0;
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_getpeername(
     int sockfd, struct sockaddr *addr, socklen_t *addrlen,
     dfsan_label sockfd_label, dfsan_label addr_label, dfsan_label addrlen_label,
     dfsan_label *ret_label, dfsan_origin sockfd_origin,
     dfsan_origin addr_origin, dfsan_origin addrlen_origin,
     dfsan_origin *ret_origin) {
   return __dfsw_getpeername(sockfd, addr, addrlen, sockfd_label, addr_label,
                             addrlen_label, ret_label);
 }

 // Type of the function passed to dfsan_set_write_callback.
 typedef void (*write_dfsan_callback_t)(int fd, const void *buf, ssize_t count);

 // Calls to dfsan_set_write_callback() set the values in this struct.
 // Calls to the custom version of write() read (and invoke) them.
 static struct {
   write_dfsan_callback_t write_callback = nullptr;
 } write_callback_info;

 SANITIZER_INTERFACE_ATTRIBUTE void __dfsw_dfsan_set_write_callback(
     write_dfsan_callback_t write_callback, dfsan_label write_callback_label,
     dfsan_label *ret_label) {
   write_callback_info.write_callback = write_callback;
 }

 SANITIZER_INTERFACE_ATTRIBUTE void __dfso_dfsan_set_write_callback(
     write_dfsan_callback_t write_callback, dfsan_label write_callback_label,
     dfsan_label *ret_label, dfsan_origin write_callback_origin,
     dfsan_origin *ret_origin) {
   write_callback_info.write_callback = write_callback;
 }

 static inline void setup_tls_args_for_write_callback(
     dfsan_label fd_label, dfsan_label buf_label, dfsan_label count_label,
     bool origins, dfsan_origin fd_origin, dfsan_origin buf_origin,
     dfsan_origin count_origin) {
   // The callback code will expect argument shadow labels in the args TLS,
   // and origin labels in the origin args TLS.
   // Previously this was done by a trampoline, but we want to remove this:
   // https://github.com/llvm/llvm-project/issues/54172
   //
   // Instead, this code is manually setting up the args TLS data.
   //
   // The offsets used need to correspond with the instrumentation code,
   // see llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
   // DFSanFunction::getShadowForTLSArgument.
   // https://github.com/llvm/llvm-project/blob/0acc9e4b5edd8b39ff3d4c6d0e17f02007671c4e/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp#L1684
   // https://github.com/llvm/llvm-project/blob/0acc9e4b5edd8b39ff3d4c6d0e17f02007671c4e/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp#L125
   //
   // Here the arguments are all primitives, but it can be more complex
   // to compute offsets for array/aggregate type arguments.
   //
   // TODO(browneee): Consider a builtin to improve maintainabliity.
   // With a builtin, we would provide the argument labels via builtin,
   // and the builtin would reuse parts of the instrumentation code to ensure
   // that this code and the instrumentation can never be out of sync.
   // Note: Currently DFSan instrumentation does not run on this code, so
   // the builtin may need to be handled outside DFSan instrumentation.
   dfsan_set_arg_tls(0, fd_label);
   dfsan_set_arg_tls(1, buf_label);
   dfsan_set_arg_tls(2, count_label);
   if (origins) {
     dfsan_set_arg_origin_tls(0, fd_origin);
     dfsan_set_arg_origin_tls(1, buf_origin);
     dfsan_set_arg_origin_tls(2, count_origin);
   }
 }

 SANITIZER_INTERFACE_ATTRIBUTE int
 __dfsw_write(int fd, const void *buf, size_t count,
              dfsan_label fd_label, dfsan_label buf_label,
              dfsan_label count_label, dfsan_label *ret_label) {
   if (write_callback_info.write_callback) {
     setup_tls_args_for_write_callback(fd_label, buf_label, count_label, false,
                                       0, 0, 0);
     write_callback_info.write_callback(fd, buf, count);
   }

   *ret_label = 0;
   return write(fd, buf, count);
 }

 SANITIZER_INTERFACE_ATTRIBUTE int __dfso_write(
     int fd, const void *buf, size_t count, dfsan_label fd_label,
     dfsan_label buf_label, dfsan_label count_label, dfsan_label *ret_label,
     dfsan_origin fd_origin, dfsan_origin buf_origin, dfsan_origin count_origin,
     dfsan_origin *ret_origin) {
   if (write_callback_info.write_callback) {
     setup_tls_args_for_write_callback(fd_label, buf_label, count_label, true,
                                       fd_origin, buf_origin, count_origin);
     write_callback_info.write_callback(fd, buf, count);
   }

   *ret_label = 0;
   return write(fd, buf, count);
 }
 } // namespace __dfsan

 // Type used to extract a dfsan_label with va_arg()
 typedef int dfsan_label_va;

 // Formats a chunk either a constant string or a single format directive (e.g.,
 // '%.3f').
 struct Formatter {
   Formatter(char *str_, const char *fmt_, size_t size_)
       : str(str_), str_off(0), size(size_), fmt_start(fmt_), fmt_cur(fmt_),
         width(-1) {}

   int format() {
     char *tmp_fmt = build_format_string();
     int retval =
         snprintf(str + str_off, str_off < size ? size - str_off : 0, tmp_fmt,
                  0 /* used only to avoid warnings */);
     free(tmp_fmt);
     return retval;
   }

   template <typename T> int format(T arg) {
     char *tmp_fmt = build_format_string();
     int retval;
     if (width >= 0) {
       retval = snprintf(str + str_off, str_off < size ? size - str_off : 0,
                         tmp_fmt, width, arg);
     } else {
       retval = snprintf(str + str_off, str_off < size ? size - str_off : 0,
                         tmp_fmt, arg);
     }
     free(tmp_fmt);
     return retval;
   }

   char *build_format_string() {
     size_t fmt_size = fmt_cur - fmt_start + 1;
     char *new_fmt = (char *)malloc(fmt_size + 1);
     assert(new_fmt);
     internal_memcpy(new_fmt, fmt_start, fmt_size);
     new_fmt[fmt_size] = '\0';
     return new_fmt;
   }

   char *str_cur() { return str + str_off; }

   size_t num_written_bytes(int retval) {
     if (retval < 0) {
       return 0;
     }

     size_t num_avail = str_off < size ? size - str_off : 0;
     if (num_avail == 0) {
       return 0;
     }

     size_t num_written = retval;
     // A return value of {v,}snprintf of size or more means that the output was
     // truncated.
     if (num_written >= num_avail) {
       num_written -= num_avail;
     }

     return num_written;
   }

   char *str;
   size_t str_off;
   size_t size;
   const char *fmt_start;
   const char *fmt_cur;
   int width;
 };

 // Formats the input and propagates the input labels to the output. The output
 // is stored in 'str'. 'size' bounds the number of output bytes. 'format' and
 // 'ap' are the format string and the list of arguments for formatting. Returns
 // the return value vsnprintf would return.
 //
 // The function tokenizes the format string in chunks representing either a
 // constant string or a single format directive (e.g., '%.3f') and formats each
 // chunk independently into the output string. This approach allows to figure
 // out which bytes of the output string depends on which argument and thus to
 // propagate labels more precisely.
 //
 // WARNING: This implementation does not support conversion specifiers with
 // positional arguments.
 static int format_buffer(char *str, size_t size, const char *fmt,
                          dfsan_label *va_labels, dfsan_label *ret_label,
                          dfsan_origin *va_origins, dfsan_origin *ret_origin,
                          va_list ap) {
   Formatter formatter(str, fmt, size);

   while (*formatter.fmt_cur) {
     formatter.fmt_start = formatter.fmt_cur;
     formatter.width = -1;
     int retval = 0;

     if (*formatter.fmt_cur != '%') {
       // Ordinary character. Consume all the characters until a '%' or the end
       // of the string.
       for (; *(formatter.fmt_cur + 1) && *(formatter.fmt_cur + 1) != '%';
            ++formatter.fmt_cur) {}
       retval = formatter.format();
       dfsan_set_label(0, formatter.str_cur(),
                       formatter.num_written_bytes(retval));
     } else {
       // Conversion directive. Consume all the characters until a conversion
       // specifier or the end of the string.
       bool end_fmt = false;
       for (; *formatter.fmt_cur && !end_fmt; ) {
         switch (*++formatter.fmt_cur) {
         case 'd':
         case 'i':
         case 'o':
         case 'u':
         case 'x':
         case 'X':
           switch (*(formatter.fmt_cur - 1)) {
           case 'h':
             // Also covers the 'hh' case (since the size of the arg is still
             // an int).
             retval = formatter.format(va_arg(ap, int));
             break;
           case 'l':
             if (formatter.fmt_cur - formatter.fmt_start >= 2 &&
                 *(formatter.fmt_cur - 2) == 'l') {
               retval = formatter.format(va_arg(ap, long long int));
             } else {
               retval = formatter.format(va_arg(ap, long int));
             }
             break;
           case 'q':
             retval = formatter.format(va_arg(ap, long long int));
             break;
           case 'j':
             retval = formatter.format(va_arg(ap, intmax_t));
             break;
           case 'z':
           case 't':
             retval = formatter.format(va_arg(ap, size_t));
             break;
           default:
             retval = formatter.format(va_arg(ap, int));
           }
           if (va_origins == nullptr)
             dfsan_set_label(*va_labels++, formatter.str_cur(),
                             formatter.num_written_bytes(retval));
           else
             dfsan_set_label_origin(*va_labels++, *va_origins++,
                                    formatter.str_cur(),
                                    formatter.num_written_bytes(retval));
           end_fmt = true;
           break;

         case 'a':
         case 'A':
         case 'e':
         case 'E':
         case 'f':
         case 'F':
         case 'g':
         case 'G':
           if (*(formatter.fmt_cur - 1) == 'L') {
             retval = formatter.format(va_arg(ap, long double));
           } else {
             retval = formatter.format(va_arg(ap, double));
           }
           if (va_origins == nullptr)
             dfsan_set_label(*va_labels++, formatter.str_cur(),
                             formatter.num_written_bytes(retval));
           else
             dfsan_set_label_origin(*va_labels++, *va_origins++,
                                    formatter.str_cur(),
                                    formatter.num_written_bytes(retval));
           end_fmt = true;
           break;

         case 'c':
           retval = formatter.format(va_arg(ap, int));
           if (va_origins == nullptr)
             dfsan_set_label(*va_labels++, formatter.str_cur(),
                             formatter.num_written_bytes(retval));
           else
             dfsan_set_label_origin(*va_labels++, *va_origins++,
                                    formatter.str_cur(),
                                    formatter.num_written_bytes(retval));
           end_fmt = true;
           break;

         case 's': {
           char *arg = va_arg(ap, char *);
           retval = formatter.format(arg);
           if (va_origins) {
             va_origins++;
             dfsan_mem_origin_transfer(formatter.str_cur(), arg,
                                       formatter.num_written_bytes(retval));
           }
           va_labels++;
           dfsan_mem_shadow_transfer(formatter.str_cur(), arg,
                                     formatter.num_written_bytes(retval));
           end_fmt = true;
           break;
         }

         case 'p':
           retval = formatter.format(va_arg(ap, void *));
           if (va_origins == nullptr)
             dfsan_set_label(*va_labels++, formatter.str_cur(),
                             formatter.num_written_bytes(retval));
           else
             dfsan_set_label_origin(*va_labels++, *va_origins++,
                                    formatter.str_cur(),
                                    formatter.num_written_bytes(retval));
           end_fmt = true;
           break;

         case 'n': {
           int *ptr = va_arg(ap, int *);
           *ptr = (int)formatter.str_off;
           va_labels++;
           if (va_origins)
             va_origins++;
           dfsan_set_label(0, ptr, sizeof(ptr));
           end_fmt = true;
           break;
         }

         case '%':
           retval = formatter.format();
           dfsan_set_label(0, formatter.str_cur(),
                           formatter.num_written_bytes(retval));
           end_fmt = true;
           break;

         case '*':
           formatter.width = va_arg(ap, int);
           va_labels++;
           if (va_origins)
             va_origins++;
           break;

         default:
           break;
         }
       }
     }

     if (retval < 0) {
       return retval;
     }

     formatter.fmt_cur++;
     formatter.str_off += retval;
   }

   *ret_label = 0;
   if (ret_origin)
     *ret_origin = 0;

   // Number of bytes written in total.
   return formatter.str_off;
 }

 extern "C" {
 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sprintf(char *str, const char *format, dfsan_label str_label,
                    dfsan_label format_label, dfsan_label *va_labels,
                    dfsan_label *ret_label, ...) {
   va_list ap;
   va_start(ap, ret_label);
   int ret = format_buffer(str, ~0ul, format, va_labels, ret_label, nullptr,
                           nullptr, ap);
   va_end(ap);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_sprintf(char *str, const char *format, dfsan_label str_label,
                    dfsan_label format_label, dfsan_label *va_labels,
                    dfsan_label *ret_label, dfsan_origin str_origin,
                    dfsan_origin format_origin, dfsan_origin *va_origins,
                    dfsan_origin *ret_origin, ...) {
   va_list ap;
   va_start(ap, ret_origin);
   int ret = format_buffer(str, ~0ul, format, va_labels, ret_label, va_origins,
                           ret_origin, ap);
   va_end(ap);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_snprintf(char *str, size_t size, const char *format,
                     dfsan_label str_label, dfsan_label size_label,
                     dfsan_label format_label, dfsan_label *va_labels,
                     dfsan_label *ret_label, ...) {
   va_list ap;
   va_start(ap, ret_label);
   int ret = format_buffer(str, size, format, va_labels, ret_label, nullptr,
                           nullptr, ap);
   va_end(ap);
   return ret;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 int __dfso_snprintf(char *str, size_t size, const char *format,
                     dfsan_label str_label, dfsan_label size_label,
                     dfsan_label format_label, dfsan_label *va_labels,
                     dfsan_label *ret_label, dfsan_origin str_origin,
                     dfsan_origin size_origin, dfsan_origin format_origin,
                     dfsan_origin *va_origins, dfsan_origin *ret_origin, ...) {
   va_list ap;
   va_start(ap, ret_origin);
   int ret = format_buffer(str, size, format, va_labels, ret_label, va_origins,
                           ret_origin, ap);
   va_end(ap);
   return ret;
 }

 static void BeforeFork() {
   StackDepotLockAll();
   GetChainedOriginDepot()->LockAll();
 }

 static void AfterFork() {
   GetChainedOriginDepot()->UnlockAll();
   StackDepotUnlockAll();
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 pid_t __dfsw_fork(dfsan_label *ret_label) {
   pid_t pid = fork();
   *ret_label = 0;
   return pid;
 }

 SANITIZER_INTERFACE_ATTRIBUTE
 pid_t __dfso_fork(dfsan_label *ret_label, dfsan_origin *ret_origin) {
   BeforeFork();
   pid_t pid = __dfsw_fork(ret_label);
   AfterFork();
   return pid;
 }

 // Default empty implementations (weak). Users should redefine them.
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard, u32 *) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_guard_init, u32 *,
                              u32 *) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_pcs_init, const uptr *beg,
                              const uptr *end) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_pc_indir, void) {}

 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp1, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp2, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp4, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_cmp8, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp1,
                              void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp2,
                              void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp4,
                              void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_const_cmp8,
                              void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __dfsw___sanitizer_cov_trace_switch, void) {}
 }  // extern "C"