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//===- Unix/Process.cpp - Unix Process Implementation --------- -*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file provides the generic Unix implementation of the Process class.
#include "Unix.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/config.h"
#include <mutex>
#include <optional>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <signal.h>
#if defined(HAVE_MALLINFO) || defined(HAVE_MALLINFO2)
#include <malloc.h>
#if defined(HAVE_MALLCTL)
#include <malloc_np.h>
#include <malloc/malloc.h>
#include <sys/ioctl.h>
#include <termios.h>
//=== WARNING: Implementation here must contain only generic UNIX code that
//=== is guaranteed to work on *all* UNIX variants.
using namespace llvm;
using namespace sys;
static std::pair<std::chrono::microseconds, std::chrono::microseconds>
getRUsageTimes() {
#if defined(HAVE_GETRUSAGE)
struct rusage RU;
::getrusage(RUSAGE_SELF, &RU);
return {toDuration(RU.ru_utime), toDuration(RU.ru_stime)};
#ifndef __MVS__ // Exclude for MVS in case -pedantic is used
#warning Cannot get usage times on this platform
return {std::chrono::microseconds::zero(), std::chrono::microseconds::zero()};
Process::Pid Process::getProcessId() {
static_assert(sizeof(Pid) >= sizeof(pid_t),
"Process::Pid should be big enough to store pid_t");
return Pid(::getpid());
// On Cygwin, getpagesize() returns 64k(AllocationGranularity) and
// offset in mmap(3) should be aligned to the AllocationGranularity.
Expected<unsigned> Process::getPageSize() {
static const int page_size = ::getpagesize();
#elif defined(HAVE_SYSCONF)
static long page_size = ::sysconf(_SC_PAGE_SIZE);
#error Cannot get the page size on this machine
if (page_size == -1)
return errorCodeToError(errnoAsErrorCode());
return static_cast<unsigned>(page_size);
size_t Process::GetMallocUsage() {
#if defined(HAVE_MALLINFO2)
struct mallinfo2 mi;
mi = ::mallinfo2();
return mi.uordblks;
#elif defined(HAVE_MALLINFO)
struct mallinfo mi;
mi = ::mallinfo();
return mi.uordblks;
malloc_statistics_t Stats;
malloc_zone_statistics(malloc_default_zone(), &Stats);
return Stats.size_in_use; // darwin
#elif defined(HAVE_MALLCTL)
size_t alloc, sz;
sz = sizeof(size_t);
if (mallctl("stats.allocated", &alloc, &sz, NULL, 0) == 0)
return alloc;
return 0;
#elif defined(HAVE_SBRK)
// Note this is only an approximation and more closely resembles
// the value returned by mallinfo in the arena field.
static char *StartOfMemory = reinterpret_cast<char *>(::sbrk(0));
char *EndOfMemory = (char *)sbrk(0);
if (EndOfMemory != ((char *)-1) && StartOfMemory != ((char *)-1))
return EndOfMemory - StartOfMemory;
return 0;
#ifndef __MVS__ // Exclude for MVS in case -pedantic is used
#warning Cannot get malloc info on this platform
return 0;
void Process::GetTimeUsage(TimePoint<> &elapsed,
std::chrono::nanoseconds &user_time,
std::chrono::nanoseconds &sys_time) {
elapsed = std::chrono::system_clock::now();
std::tie(user_time, sys_time) = getRUsageTimes();
#if defined(HAVE_MACH_MACH_H) && !defined(__GNU__)
#include <mach/mach.h>
// Some LLVM programs such as bugpoint produce core files as a normal part of
// their operation. To prevent the disk from filling up, this function
// does what's necessary to prevent their generation.
void Process::PreventCoreFiles() {
struct rlimit rlim;
getrlimit(RLIMIT_CORE, &rlim);
#ifdef __linux__
// On Linux, if the kernel.core_pattern sysctl starts with a '|' (i.e. it
// is being piped to a coredump handler such as systemd-coredumpd), the
// kernel ignores RLIMIT_CORE (since we aren't creating a file in the file
// system) except for the magic value of 1, which disables coredumps when
// piping. 1 byte is too small for any kind of valid core dump, so it
// also disables coredumps if kernel.core_pattern creates files directly.
// While most piped coredump handlers do respect the crashing processes'
// RLIMIT_CORE, this is notable not the case for Debian's systemd-coredump
// due to a local patch that changes sysctl.d/50-coredump.conf to ignore
// the specified limit and instead use RLIM_INFINITY.
// The alternative to using RLIMIT_CORE=1 would be to use prctl() with the
// PR_SET_DUMPABLE flag, however that also prevents ptrace(), so makes it
// impossible to attach a debugger.
rlim.rlim_cur = std::min<rlim_t>(1, rlim.rlim_max);
rlim.rlim_cur = 0;
setrlimit(RLIMIT_CORE, &rlim);
#if defined(HAVE_MACH_MACH_H) && !defined(__GNU__)
// Disable crash reporting on Mac OS X 10.0-10.4
// get information about the original set of exception ports for the task
mach_msg_type_number_t Count = 0;
exception_mask_t OriginalMasks[EXC_TYPES_COUNT];
exception_port_t OriginalPorts[EXC_TYPES_COUNT];
exception_behavior_t OriginalBehaviors[EXC_TYPES_COUNT];
thread_state_flavor_t OriginalFlavors[EXC_TYPES_COUNT];
kern_return_t err = task_get_exception_ports(
mach_task_self(), EXC_MASK_ALL, OriginalMasks, &Count, OriginalPorts,
OriginalBehaviors, OriginalFlavors);
if (err == KERN_SUCCESS) {
// replace each with MACH_PORT_NULL.
for (unsigned i = 0; i != Count; ++i)
task_set_exception_ports(mach_task_self(), OriginalMasks[i],
MACH_PORT_NULL, OriginalBehaviors[i],
// Disable crash reporting on Mac OS X 10.5
signal(SIGABRT, _exit);
signal(SIGILL, _exit);
signal(SIGFPE, _exit);
signal(SIGSEGV, _exit);
signal(SIGBUS, _exit);
coreFilesPrevented = true;
std::optional<std::string> Process::GetEnv(StringRef Name) {
std::string NameStr = Name.str();
const char *Val = ::getenv(NameStr.c_str());
if (!Val)
return std::nullopt;
return std::string(Val);
namespace {
class FDCloser {
FDCloser(int &FD) : FD(FD), KeepOpen(false) {}
void keepOpen() { KeepOpen = true; }
~FDCloser() {
if (!KeepOpen && FD >= 0)
FDCloser(const FDCloser &) = delete;
void operator=(const FDCloser &) = delete;
int &FD;
bool KeepOpen;
} // namespace
std::error_code Process::FixupStandardFileDescriptors() {
int NullFD = -1;
FDCloser FDC(NullFD);
for (int StandardFD : StandardFDs) {
struct stat st;
errno = 0;
if (RetryAfterSignal(-1, ::fstat, StandardFD, &st) < 0) {
assert(errno && "expected errno to be set if fstat failed!");
// fstat should return EBADF if the file descriptor is closed.
if (errno != EBADF)
return errnoAsErrorCode();
// if fstat succeeds, move on to the next FD.
if (!errno)
assert(errno == EBADF && "expected errno to have EBADF at this point!");
if (NullFD < 0) {
// Call ::open in a lambda to avoid overload resolution in
// RetryAfterSignal when open is overloaded, such as in Bionic.
auto Open = [&]() { return ::open("/dev/null", O_RDWR); };
if ((NullFD = RetryAfterSignal(-1, Open)) < 0)
return errnoAsErrorCode();
if (NullFD == StandardFD)
else if (dup2(NullFD, StandardFD) < 0)
return errnoAsErrorCode();
return std::error_code();
std::error_code Process::SafelyCloseFileDescriptor(int FD) {
// Create a signal set filled with *all* signals.
sigset_t FullSet, SavedSet;
if (sigfillset(&FullSet) < 0 || sigfillset(&SavedSet) < 0)
return errnoAsErrorCode();
// Atomically swap our current signal mask with a full mask.
if (int EC = pthread_sigmask(SIG_SETMASK, &FullSet, &SavedSet))
return std::error_code(EC, std::generic_category());
if (sigprocmask(SIG_SETMASK, &FullSet, &SavedSet) < 0)
return errnoAsErrorCode();
// Attempt to close the file descriptor.
// We need to save the error, if one occurs, because our subsequent call to
// pthread_sigmask might tamper with errno.
int ErrnoFromClose = 0;
if (::close(FD) < 0)
ErrnoFromClose = errno;
// Restore the signal mask back to what we saved earlier.
int EC = 0;
EC = pthread_sigmask(SIG_SETMASK, &SavedSet, nullptr);
if (sigprocmask(SIG_SETMASK, &SavedSet, nullptr) < 0)
EC = errno;
// The error code from close takes precedence over the one from
// pthread_sigmask.
if (ErrnoFromClose)
return std::error_code(ErrnoFromClose, std::generic_category());
return std::error_code(EC, std::generic_category());
bool Process::StandardInIsUserInput() {
return FileDescriptorIsDisplayed(STDIN_FILENO);
bool Process::StandardOutIsDisplayed() {
return FileDescriptorIsDisplayed(STDOUT_FILENO);
bool Process::StandardErrIsDisplayed() {
return FileDescriptorIsDisplayed(STDERR_FILENO);
bool Process::FileDescriptorIsDisplayed(int fd) {
return isatty(fd);
// If we don't have isatty, just return false.
return false;
static unsigned getColumns() {
// If COLUMNS is defined in the environment, wrap to that many columns.
if (const char *ColumnsStr = std::getenv("COLUMNS")) {
int Columns = std::atoi(ColumnsStr);
if (Columns > 0)
return Columns;
// We used to call ioctl TIOCGWINSZ to determine the width. It is considered
// unuseful.
return 0;
unsigned Process::StandardOutColumns() {
if (!StandardOutIsDisplayed())
return 0;
return getColumns();
unsigned Process::StandardErrColumns() {
if (!StandardErrIsDisplayed())
return 0;
return getColumns();
static bool terminalHasColors() {
// Check if the current terminal is one of terminals that are known to support
// ANSI color escape codes.
if (const char *TermStr = std::getenv("TERM")) {
return StringSwitch<bool>(TermStr)
.Case("ansi", true)
.Case("cygwin", true)
.Case("linux", true)
.StartsWith("screen", true)
.StartsWith("xterm", true)
.StartsWith("vt100", true)
.StartsWith("rxvt", true)
.EndsWith("color", true)
return false;
bool Process::FileDescriptorHasColors(int fd) {
// A file descriptor has colors if it is displayed and the terminal has
// colors.
return FileDescriptorIsDisplayed(fd) && terminalHasColors();
bool Process::StandardOutHasColors() {
return FileDescriptorHasColors(STDOUT_FILENO);
bool Process::StandardErrHasColors() {
return FileDescriptorHasColors(STDERR_FILENO);
void Process::UseANSIEscapeCodes(bool /*enable*/) {
// No effect.
bool Process::ColorNeedsFlush() {
// No, we use ANSI escape sequences.
return false;
const char *Process::OutputColor(char code, bool bold, bool bg) {
return colorcodes[bg ? 1 : 0][bold ? 1 : 0][code & 15];
const char *Process::OutputBold(bool bg) { return "\033[1m"; }
const char *Process::OutputReverse() { return "\033[7m"; }
const char *Process::ResetColor() { return "\033[0m"; }
static unsigned GetRandomNumberSeed() {
// Attempt to get the initial seed from /dev/urandom, if possible.
int urandomFD = open("/dev/urandom", O_RDONLY);
if (urandomFD != -1) {
unsigned seed;
// Don't use a buffered read to avoid reading more data
// from /dev/urandom than we need.
int count = read(urandomFD, (void *)&seed, sizeof(seed));
// Return the seed if the read was successful.
if (count == sizeof(seed))
return seed;
// Otherwise, swizzle the current time and the process ID to form a reasonable
// seed.
const auto Now = std::chrono::high_resolution_clock::now();
return hash_combine(Now.time_since_epoch().count(), ::getpid());
unsigned llvm::sys::Process::GetRandomNumber() {
return arc4random();
static int x = (static_cast<void>(::srand(GetRandomNumberSeed())), 0);
return ::rand();
[[noreturn]] void Process::ExitNoCleanup(int RetCode) { _Exit(RetCode); }