//===----------------------------------------------------------------------===//
//
// 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
//
//
//  Implements unw_* functions from <libunwind.h>
//
//===----------------------------------------------------------------------===//

#include <libunwind.h>

#include "config.h"
#include "libunwind_ext.h"

#include <stdlib.h>

#if defined(__FreeBSD__) && defined(__x86_64__) &&                             \
    !defined(_LIBUNWIND_IS_BAREMETAL)
#include <signal.h>
#include <ucontext.h>
#endif

// Define the __has_feature extension for compilers that do not support it so
// that we can later check for the presence of ASan in a compiler-neutral way.
#if !defined(__has_feature)
#define __has_feature(feature) 0
#endif

#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
#include <sanitizer/asan_interface.h>
#endif

#if !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__wasm__)
#include "AddressSpace.hpp"
#include "UnwindCursor.hpp"

using namespace libunwind;

#if defined(__FreeBSD__) && defined(__x86_64__) &&                             \
    !defined(_LIBUNWIND_IS_BAREMETAL)
// Changing FS/GS selectors can clear their bases, while sysarch base setters
// replace the selectors. Let sigreturn restore the complete state atomically.
// use sigreturn() over setcontext() as setcontext() intentionally leaves CS
// unchanged.
extern "C" _LIBUNWIND_HIDDEN void
__libunwind_Registers_x86_64_jumpto(Registers_x86_64 *registers) {
  ucontext_t context;
  if (getcontext(&context) != 0)
    _LIBUNWIND_ABORT("getcontext failed");
  mcontext_t &mc = context.uc_mcontext;
#define RESTORE(reg, field) mc.field = registers->getRegister(UNW_X86_64_##reg)
  RESTORE(RAX, mc_rax);
  RESTORE(RBX, mc_rbx);
  RESTORE(RCX, mc_rcx);
  RESTORE(RDX, mc_rdx);
  RESTORE(RDI, mc_rdi);
  RESTORE(RSI, mc_rsi);
  RESTORE(RBP, mc_rbp);
  RESTORE(RSP, mc_rsp);
  RESTORE(R8, mc_r8);
  RESTORE(R9, mc_r9);
  RESTORE(R10, mc_r10);
  RESTORE(R11, mc_r11);
  RESTORE(R12, mc_r12);
  RESTORE(R13, mc_r13);
  RESTORE(R14, mc_r14);
  RESTORE(R15, mc_r15);
  RESTORE(RIP, mc_rip);
  RESTORE(RFLAGS, mc_rflags);
  RESTORE(CS, mc_cs);
  RESTORE(SS, mc_ss);
  RESTORE(DS, mc_ds);
  RESTORE(ES, mc_es);
  RESTORE(FS, mc_fs);
  RESTORE(GS, mc_gs);
  RESTORE(FS_BASE, mc_fsbase);
  RESTORE(GS_BASE, mc_gsbase);
#undef RESTORE
  mc.mc_flags |= _MC_HASSEGS | _MC_HASBASES;
  sigreturn(&context);
  _LIBUNWIND_ABORT("sigreturn failed");
}
#endif

/// internal object to represent this process's address space
LocalAddressSpace LocalAddressSpace::sThisAddressSpace;

_LIBUNWIND_EXPORT unw_addr_space_t unw_local_addr_space =
    (unw_addr_space_t)&LocalAddressSpace::sThisAddressSpace;

/// Create a cursor of a thread in this process given 'context' recorded by
/// __unw_getcontext().
_LIBUNWIND_HIDDEN int __unw_init_local(unw_cursor_t *cursor,
                                       unw_context_t *context) {
  _LIBUNWIND_TRACE_API("__unw_init_local(cursor=%p, context=%p)",
                       static_cast<void *>(cursor),
                       static_cast<void *>(context));
#if defined(__i386__)
# define REGISTER_KIND Registers_x86
#elif defined(__x86_64__)
# define REGISTER_KIND Registers_x86_64
#elif defined(__powerpc64__)
# define REGISTER_KIND Registers_ppc64
#elif defined(__powerpc__)
# define REGISTER_KIND Registers_ppc
#elif defined(__aarch64__)
# define REGISTER_KIND Registers_arm64
#elif defined(__arm__)
# define REGISTER_KIND Registers_arm
#elif defined(__or1k__)
# define REGISTER_KIND Registers_or1k
#elif defined(__hexagon__)
# define REGISTER_KIND Registers_hexagon
#elif defined(__mips__) && defined(_ABIO32) && _MIPS_SIM == _ABIO32
# define REGISTER_KIND Registers_mips_o32
#elif defined(__mips64)
# define REGISTER_KIND Registers_mips_newabi
#elif defined(__mips__)
# warning The MIPS architecture is not supported with this ABI and environment!
#elif defined(__sparc__) && defined(__arch64__)
#define REGISTER_KIND Registers_sparc64
#elif defined(__sparc__)
# define REGISTER_KIND Registers_sparc
#elif defined(__riscv)
# define REGISTER_KIND Registers_riscv
#elif defined(__ve__)
# define REGISTER_KIND Registers_ve
#elif defined(__s390x__)
# define REGISTER_KIND Registers_s390x
#elif defined(__loongarch__) && __loongarch_grlen == 64
#define REGISTER_KIND Registers_loongarch
#else
# error Architecture not supported
#endif
  // Use "placement new" to allocate UnwindCursor in the cursor buffer.
  new (reinterpret_cast<UnwindCursor<LocalAddressSpace, REGISTER_KIND> *>(cursor))
      UnwindCursor<LocalAddressSpace, REGISTER_KIND>(
          context, LocalAddressSpace::sThisAddressSpace);
#undef REGISTER_KIND
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  co->setInfoBasedOnIPRegister();

  return UNW_ESUCCESS;
}
_LIBUNWIND_WEAK_ALIAS(__unw_init_local, unw_init_local)

/// Get value of specified register at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_get_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
                                    unw_word_t *value) {
  _LIBUNWIND_TRACE_API("__unw_get_reg(cursor=%p, regNum=%d, &value=%p)",
                       static_cast<void *>(cursor), regNum,
                       static_cast<void *>(value));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  if (co->validReg(regNum)) {
    *value = co->getReg(regNum);
    return UNW_ESUCCESS;
  }
  return UNW_EBADREG;
}
_LIBUNWIND_WEAK_ALIAS(__unw_get_reg, unw_get_reg)

/// Set value of specified register at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_set_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
                                    unw_word_t value) {
  _LIBUNWIND_TRACE_API("__unw_set_reg(cursor=%p, regNum=%d, value=0x%" PRIxPTR
                       ")",
                       static_cast<void *>(cursor), regNum, value);
  typedef LocalAddressSpace::pint_t pint_t;
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  if (co->validReg(regNum)) {
    // special case altering IP to re-find info (being called by personality
    // function)
    if (regNum == UNW_REG_IP) {
      unw_proc_info_t info;
      // First, get the FDE for the old location and then update it.
      co->getInfo(&info);

      pint_t sp = (pint_t)co->getReg(UNW_REG_SP);

#if defined(_LIBUNWIND_TARGET_AARCH64_AUTHENTICATED_UNWINDING)
      {
        // It is only valid to set the IP within the current function. This is
        // important for ptrauth, otherwise the IP cannot be correctly signed.
        //
        // However many JITs do not configure CFI frames, so we cannot actually
        // enforce this - at least not without an extremely expensive syscall.
        //
        // For the forseeable future this will need to be a debug only assertion
        // so we just strip and assert to avoid the unnecessary auths in release
        // builds.
        unw_word_t stripped_value = (unw_word_t)ptrauth_strip(
            (void *)value, ptrauth_key_return_address);
        if (stripped_value < info.start_ip && stripped_value > info.end_ip)
          _LIBUNWIND_LOG("Badly behaved use of unw_set_reg: moving IP(0x%zX) "
                         "outside of CFI bounds function (0x%zX, 0x%zX)",
                         stripped_value, info.start_ip, info.end_ip);

        // PC should have been signed with the sp, so we verify that
        // roundtripping does not fail. The `ptrauth_auth_and_resign` is
        // guaranteed to trap on authentication failure even without FPAC
        // feature.
        pint_t pc = (pint_t)co->getReg(UNW_REG_IP);
        if (ptrauth_auth_and_resign((void *)pc, ptrauth_key_return_address, sp,
                                    ptrauth_key_return_address,
                                    sp) != (void *)pc) {
          _LIBUNWIND_LOG(
              "Bad unwind with PAuth-enabled ABI (0x%zX, 0x%zX)->0x%zX\n", pc,
              sp,
              (pint_t)ptrauth_auth_data((void *)pc, ptrauth_key_return_address,
                                        sp));
          _LIBUNWIND_ABORT("Bad unwind with PAuth-enabled ABI");
        }
      }
#endif

      // If the original call expects stack adjustment, perform this now.
      // Normal frame unwinding would have included the offset already in the
      // CFA computation.
      // Note: for PA-RISC and other platforms where the stack grows up,
      // this should actually be - info.gp. LLVM doesn't currently support
      // any such platforms and Clang doesn't export a macro for them.
      if (info.gp)
        co->setReg(UNW_REG_SP, sp + info.gp);
      co->setReg(UNW_REG_IP, value);
      co->setInfoBasedOnIPRegister(false);
    } else {
      co->setReg(regNum, (pint_t)value);
    }
    return UNW_ESUCCESS;
  }
  return UNW_EBADREG;
}
_LIBUNWIND_WEAK_ALIAS(__unw_set_reg, unw_set_reg)

/// Get value of specified float register at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_get_fpreg(unw_cursor_t *cursor, unw_regnum_t regNum,
                                      unw_fpreg_t *value) {
  _LIBUNWIND_TRACE_API("__unw_get_fpreg(cursor=%p, regNum=%d, &value=%p)",
                       static_cast<void *>(cursor), regNum,
                       static_cast<void *>(value));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  if (co->validFloatReg(regNum)) {
    *value = co->getFloatReg(regNum);
    return UNW_ESUCCESS;
  }
  return UNW_EBADREG;
}
_LIBUNWIND_WEAK_ALIAS(__unw_get_fpreg, unw_get_fpreg)

/// Set value of specified float register at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_set_fpreg(unw_cursor_t *cursor, unw_regnum_t regNum,
                                      unw_fpreg_t value) {
#if defined(_LIBUNWIND_ARM_EHABI)
  _LIBUNWIND_TRACE_API("__unw_set_fpreg(cursor=%p, regNum=%d, value=%llX)",
                       static_cast<void *>(cursor), regNum, value);
#else
  _LIBUNWIND_TRACE_API("__unw_set_fpreg(cursor=%p, regNum=%d, value=%g)",
                       static_cast<void *>(cursor), regNum, value);
#endif
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  if (co->validFloatReg(regNum)) {
    co->setFloatReg(regNum, value);
    return UNW_ESUCCESS;
  }
  return UNW_EBADREG;
}
_LIBUNWIND_WEAK_ALIAS(__unw_set_fpreg, unw_set_fpreg)

/// Move cursor to next frame.
_LIBUNWIND_HIDDEN int __unw_step(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("__unw_step(cursor=%p)", static_cast<void *>(cursor));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->step();
}
_LIBUNWIND_WEAK_ALIAS(__unw_step, unw_step)

// Move cursor to next frame and for stage2 of unwinding.
// This resets MTE tags of tagged frames to zero.
extern "C" _LIBUNWIND_HIDDEN int __unw_step_stage2(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("__unw_step_stage2(cursor=%p)",
                       static_cast<void *>(cursor));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->step(true);
}

/// Get unwind info at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_get_proc_info(unw_cursor_t *cursor,
                                          unw_proc_info_t *info) {
  _LIBUNWIND_TRACE_API("__unw_get_proc_info(cursor=%p, &info=%p)",
                       static_cast<void *>(cursor), static_cast<void *>(info));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  co->getInfo(info);
  if (info->end_ip == 0)
    return UNW_ENOINFO;
  return UNW_ESUCCESS;
}
_LIBUNWIND_WEAK_ALIAS(__unw_get_proc_info, unw_get_proc_info)

/// Rebalance the execution flow by injecting the right amount of `ret`
/// instruction relatively to the amount of `walkedFrames` then resume execution
/// at cursor position (aka longjump).
_LIBUNWIND_HIDDEN int __unw_resume_with_frames_walked(unw_cursor_t *cursor,
                                                      unsigned walkedFrames) {
  _LIBUNWIND_TRACE_API("__unw_resume(cursor=%p, walkedFrames=%u)",
                       static_cast<void *>(cursor), walkedFrames);
#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
  // Inform the ASan runtime that now might be a good time to clean stuff up.
  __asan_handle_no_return();
#endif
#ifdef _LIBUNWIND_TRACE_RET_INJECT
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  co->setWalkedFrames(walkedFrames);
#endif
  return __unw_resume(cursor);
}
_LIBUNWIND_WEAK_ALIAS(__unw_resume_with_frames_walked,
                      unw_resume_with_frames_walked)

/// Legacy function. Resume execution at cursor position (aka longjump).
_LIBUNWIND_HIDDEN int __unw_resume(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("__unw_resume(cursor=%p)", static_cast<void *>(cursor));
#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
  // Inform the ASan runtime that now might be a good time to clean stuff up.
  __asan_handle_no_return();
#endif
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  co->jumpto();
  return UNW_EUNSPEC;
}
_LIBUNWIND_WEAK_ALIAS(__unw_resume, unw_resume)

/// Get name of function at cursor position in stack frame.
_LIBUNWIND_HIDDEN int __unw_get_proc_name(unw_cursor_t *cursor, char *buf,
                                          size_t bufLen, unw_word_t *offset) {
  _LIBUNWIND_TRACE_API("__unw_get_proc_name(cursor=%p, &buf=%p, bufLen=%lu)",
                       static_cast<void *>(cursor), static_cast<void *>(buf),
                       static_cast<unsigned long>(bufLen));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  if (co->getFunctionName(buf, bufLen, offset))
    return UNW_ESUCCESS;
  return UNW_EUNSPEC;
}
_LIBUNWIND_WEAK_ALIAS(__unw_get_proc_name, unw_get_proc_name)

/// Checks if a register is a floating-point register.
_LIBUNWIND_HIDDEN int __unw_is_fpreg(unw_cursor_t *cursor,
                                     unw_regnum_t regNum) {
  _LIBUNWIND_TRACE_API("__unw_is_fpreg(cursor=%p, regNum=%d)",
                       static_cast<void *>(cursor), regNum);
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->validFloatReg(regNum);
}
_LIBUNWIND_WEAK_ALIAS(__unw_is_fpreg, unw_is_fpreg)

/// Get name of specified register at cursor position in stack frame.
_LIBUNWIND_HIDDEN const char *__unw_regname(unw_cursor_t *cursor,
                                            unw_regnum_t regNum) {
  _LIBUNWIND_TRACE_API("__unw_regname(cursor=%p, regNum=%d)",
                       static_cast<void *>(cursor), regNum);
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->getRegisterName(regNum);
}
_LIBUNWIND_WEAK_ALIAS(__unw_regname, unw_regname)

/// Checks if current frame is signal trampoline.
_LIBUNWIND_HIDDEN int __unw_is_signal_frame(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("__unw_is_signal_frame(cursor=%p)",
                       static_cast<void *>(cursor));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->isSignalFrame();
}
_LIBUNWIND_WEAK_ALIAS(__unw_is_signal_frame, unw_is_signal_frame)

#ifdef _AIX
_LIBUNWIND_EXPORT uintptr_t __unw_get_data_rel_base(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("unw_get_data_rel_base(cursor=%p)",
                       static_cast<void *>(cursor));
  AbstractUnwindCursor *co = reinterpret_cast<AbstractUnwindCursor *>(cursor);
  return co->getDataRelBase();
}
_LIBUNWIND_WEAK_ALIAS(__unw_get_data_rel_base, unw_get_data_rel_base)
#endif

#ifdef __arm__
// Save VFP registers d0-d15 using FSTMIADX instead of FSTMIADD
_LIBUNWIND_HIDDEN void __unw_save_vfp_as_X(unw_cursor_t *cursor) {
  _LIBUNWIND_TRACE_API("__unw_get_fpreg_save_vfp_as_X(cursor=%p)",
                       static_cast<void *>(cursor));
  AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
  return co->saveVFPAsX();
}
_LIBUNWIND_WEAK_ALIAS(__unw_save_vfp_as_X, unw_save_vfp_as_X)
#endif


#if defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
/// SPI: walks cached DWARF entries
_LIBUNWIND_HIDDEN void __unw_iterate_dwarf_unwind_cache(void (*func)(
    unw_word_t ip_start, unw_word_t ip_end, unw_word_t fde, unw_word_t mh)) {
  _LIBUNWIND_TRACE_API("__unw_iterate_dwarf_unwind_cache(func=%p)",
                       reinterpret_cast<void *>(func));
  DwarfFDECache<LocalAddressSpace>::iterateCacheEntries(func);
}
_LIBUNWIND_WEAK_ALIAS(__unw_iterate_dwarf_unwind_cache,
                      unw_iterate_dwarf_unwind_cache)

/// IPI: for __register_frame()
void __unw_add_dynamic_fde(unw_word_t fde) {
  CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
  CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
  const char *message = CFI_Parser<LocalAddressSpace>::decodeFDE(
                           LocalAddressSpace::sThisAddressSpace,
                          (LocalAddressSpace::pint_t) fde, &fdeInfo, &cieInfo);
  if (message == NULL) {
    // dynamically registered FDEs don't have a mach_header group they are in.
    // Use fde as mh_group
    unw_word_t mh_group = fdeInfo.fdeStart;
    DwarfFDECache<LocalAddressSpace>::add((LocalAddressSpace::pint_t)mh_group,
                                          fdeInfo.pcStart, fdeInfo.pcEnd,
                                          fdeInfo.fdeStart);
  } else {
    _LIBUNWIND_DEBUG_LOG("__unw_add_dynamic_fde: bad fde: %s", message);
  }
}

/// IPI: for __deregister_frame()
void __unw_remove_dynamic_fde(unw_word_t fde) {
  // fde is own mh_group
  DwarfFDECache<LocalAddressSpace>::removeAllIn((LocalAddressSpace::pint_t)fde);
}

void __unw_add_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
  // The eh_frame section start serves as the mh_group
  unw_word_t mh_group = eh_frame_start;
  CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
  CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
  auto p = (LocalAddressSpace::pint_t)eh_frame_start;
  while (LocalAddressSpace::sThisAddressSpace.get32(p)) {
    if (CFI_Parser<LocalAddressSpace>::decodeFDE(
            LocalAddressSpace::sThisAddressSpace, p, &fdeInfo, &cieInfo,
            true) == NULL) {
      DwarfFDECache<LocalAddressSpace>::add((LocalAddressSpace::pint_t)mh_group,
                                            fdeInfo.pcStart, fdeInfo.pcEnd,
                                            fdeInfo.fdeStart);
      p += fdeInfo.fdeLength;
    } else if (CFI_Parser<LocalAddressSpace>::parseCIE(
                   LocalAddressSpace::sThisAddressSpace, p, &cieInfo) == NULL) {
      p += cieInfo.cieLength;
    } else
      return;
  }
}

void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
  // The eh_frame section start serves as the mh_group
  DwarfFDECache<LocalAddressSpace>::removeAllIn(
      (LocalAddressSpace::pint_t)eh_frame_start);
}

#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)

/// Maps the UNW_* error code to a textual representation
_LIBUNWIND_HIDDEN const char *__unw_strerror(int error_code) {
  switch (error_code) {
  case UNW_ESUCCESS:
    return "no error";
  case UNW_EUNSPEC:
    return "unspecified (general) error";
  case UNW_ENOMEM:
    return "out of memory";
  case UNW_EBADREG:
    return "bad register number";
  case UNW_EREADONLYREG:
    return "attempt to write read-only register";
  case UNW_ESTOPUNWIND:
    return "stop unwinding";
  case UNW_EINVALIDIP:
    return "invalid IP";
  case UNW_EBADFRAME:
    return "bad frame";
  case UNW_EINVAL:
    return "unsupported operation or bad value";
  case UNW_EBADVERSION:
    return "unwind info has unsupported version";
  case UNW_ENOINFO:
    return "no unwind info found";
#if defined(_LIBUNWIND_TARGET_AARCH64) && !defined(_LIBUNWIND_IS_NATIVE_ONLY)
  case UNW_ECROSSRASIGNING:
    return "cross unwind with return address signing";
#endif
  }
  return "invalid error code";
}
_LIBUNWIND_WEAK_ALIAS(__unw_strerror, unw_strerror)

#endif // !defined(__USING_SJLJ_EXCEPTIONS__) && !defined(__wasm__)

#ifdef __APPLE__

namespace libunwind {

static constexpr size_t MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS = 8;

static RWMutex findDynamicUnwindSectionsLock;
static size_t numDynamicUnwindSectionsFinders = 0;
static unw_find_dynamic_unwind_sections
    dynamicUnwindSectionsFinders[MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS] = {0};

bool findDynamicUnwindSections(void *addr, unw_dynamic_unwind_sections *info) {
  bool found = false;
  findDynamicUnwindSectionsLock.lock_shared();
  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
    if (dynamicUnwindSectionsFinders[i]((unw_word_t)addr, info)) {
      found = true;
      break;
    }
  }
  findDynamicUnwindSectionsLock.unlock_shared();
  return found;
}

} // namespace libunwind

int __unw_add_find_dynamic_unwind_sections(
    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections) {
  findDynamicUnwindSectionsLock.lock();

  // Check that we have enough space...
  if (numDynamicUnwindSectionsFinders == MAX_DYNAMIC_UNWIND_SECTIONS_FINDERS) {
    findDynamicUnwindSectionsLock.unlock();
    return UNW_ENOMEM;
  }

  // Check for value already present...
  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
    if (dynamicUnwindSectionsFinders[i] == find_dynamic_unwind_sections) {
      findDynamicUnwindSectionsLock.unlock();
      return UNW_EINVAL;
    }
  }

  // Success -- add callback entry.
  dynamicUnwindSectionsFinders[numDynamicUnwindSectionsFinders++] =
    find_dynamic_unwind_sections;
  findDynamicUnwindSectionsLock.unlock();

  return UNW_ESUCCESS;
}

int __unw_remove_find_dynamic_unwind_sections(
    unw_find_dynamic_unwind_sections find_dynamic_unwind_sections) {
  findDynamicUnwindSectionsLock.lock();

  // Find index to remove.
  size_t finderIdx = numDynamicUnwindSectionsFinders;
  for (size_t i = 0; i != numDynamicUnwindSectionsFinders; ++i) {
    if (dynamicUnwindSectionsFinders[i] == find_dynamic_unwind_sections) {
      finderIdx = i;
      break;
    }
  }

  // If no such registration is present then error out.
  if (finderIdx == numDynamicUnwindSectionsFinders) {
    findDynamicUnwindSectionsLock.unlock();
    return UNW_EINVAL;
  }

  // Remove entry.
  for (size_t i = finderIdx; i != numDynamicUnwindSectionsFinders - 1; ++i)
    dynamicUnwindSectionsFinders[i] = dynamicUnwindSectionsFinders[i + 1];
  dynamicUnwindSectionsFinders[--numDynamicUnwindSectionsFinders] = nullptr;

  findDynamicUnwindSectionsLock.unlock();
  return UNW_ESUCCESS;
}

#endif // __APPLE__

// Add logging hooks in Debug builds only
#ifndef NDEBUG
#include <stdlib.h>

_LIBUNWIND_HIDDEN
bool logAPIs() {
  // do manual lock to avoid use of _cxa_guard_acquire or initializers
  static bool checked = false;
  static bool log = false;
  if (!checked) {
    log = (getenv("LIBUNWIND_PRINT_APIS") != NULL);
    checked = true;
  }
  return log;
}

_LIBUNWIND_HIDDEN
bool logUnwinding() {
  // do manual lock to avoid use of _cxa_guard_acquire or initializers
  static bool checked = false;
  static bool log = false;
  if (!checked) {
    log = (getenv("LIBUNWIND_PRINT_UNWINDING") != NULL);
    checked = true;
  }
  return log;
}

_LIBUNWIND_HIDDEN
bool logDWARF() {
  // do manual lock to avoid use of _cxa_guard_acquire or initializers
  static bool checked = false;
  static bool log = false;
  if (!checked) {
    log = (getenv("LIBUNWIND_PRINT_DWARF") != NULL);
    checked = true;
  }
  return log;
}

#endif // NDEBUG