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llvm-project/llvm/lib/Support/Unix/Program.inc

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//===- llvm/Support/Unix/Program.cpp -----------------------------*- C++ -*-===//
//
// 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 implements the Unix specific portion of the Program class.
//
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only generic UNIX code that
//=== is guaranteed to work on *all* UNIX variants.
//===----------------------------------------------------------------------===//
#include "Unix.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/raw_ostream.h"
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
#if HAVE_SIGNAL_H
#include <signal.h>
#endif
#if HAVE_FCNTL_H
#include <fcntl.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_POSIX_SPAWN
#include <spawn.h>
#if defined(__APPLE__)
#include <TargetConditionals.h>
#endif
#if defined(__APPLE__) && !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE)
#define USE_NSGETENVIRON 1
#else
#define USE_NSGETENVIRON 0
#endif
#if !USE_NSGETENVIRON
extern char **environ;
#else
#include <crt_externs.h> // _NSGetEnviron
#endif
#endif
namespace llvm {
using namespace sys;
ProcessInfo::ProcessInfo() : Pid(0), ReturnCode(0) {}
ErrorOr<std::string> sys::findProgramByName(StringRef Name,
ArrayRef<StringRef> Paths) {
assert(!Name.empty() && "Must have a name!");
// Use the given path verbatim if it contains any slashes; this matches
// the behavior of sh(1) and friends.
if (Name.find('/') != StringRef::npos)
return std::string(Name);
SmallVector<StringRef, 16> EnvironmentPaths;
if (Paths.empty())
if (const char *PathEnv = std::getenv("PATH")) {
SplitString(PathEnv, EnvironmentPaths, ":");
Paths = EnvironmentPaths;
}
for (auto Path : Paths) {
if (Path.empty())
continue;
// Check to see if this first directory contains the executable...
SmallString<128> FilePath(Path);
sys::path::append(FilePath, Name);
if (sys::fs::can_execute(FilePath.c_str()))
return std::string(FilePath.str()); // Found the executable!
}
return errc::no_such_file_or_directory;
}
static bool RedirectIO(Optional<StringRef> Path, int FD, std::string* ErrMsg) {
if (!Path) // Noop
return false;
std::string File;
if (Path->empty())
// Redirect empty paths to /dev/null
File = "/dev/null";
else
File = *Path;
// Open the file
int InFD = open(File.c_str(), FD == 0 ? O_RDONLY : O_WRONLY|O_CREAT, 0666);
if (InFD == -1) {
MakeErrMsg(ErrMsg, "Cannot open file '" + File + "' for "
+ (FD == 0 ? "input" : "output"));
return true;
}
// Install it as the requested FD
if (dup2(InFD, FD) == -1) {
MakeErrMsg(ErrMsg, "Cannot dup2");
close(InFD);
return true;
}
close(InFD); // Close the original FD
return false;
}
#ifdef HAVE_POSIX_SPAWN
static bool RedirectIO_PS(const std::string *Path, int FD, std::string *ErrMsg,
posix_spawn_file_actions_t *FileActions) {
if (!Path) // Noop
return false;
const char *File;
if (Path->empty())
// Redirect empty paths to /dev/null
File = "/dev/null";
else
File = Path->c_str();
if (int Err = posix_spawn_file_actions_addopen(
FileActions, FD, File,
FD == 0 ? O_RDONLY : O_WRONLY | O_CREAT, 0666))
return MakeErrMsg(ErrMsg, "Cannot dup2", Err);
return false;
}
#endif
static void TimeOutHandler(int Sig) {
}
static void SetMemoryLimits(unsigned size) {
#if HAVE_SYS_RESOURCE_H && HAVE_GETRLIMIT && HAVE_SETRLIMIT
struct rlimit r;
__typeof__ (r.rlim_cur) limit = (__typeof__ (r.rlim_cur)) (size) * 1048576;
// Heap size
getrlimit (RLIMIT_DATA, &r);
r.rlim_cur = limit;
setrlimit (RLIMIT_DATA, &r);
#ifdef RLIMIT_RSS
// Resident set size.
getrlimit (RLIMIT_RSS, &r);
r.rlim_cur = limit;
setrlimit (RLIMIT_RSS, &r);
#endif
#endif
}
}
static std::vector<const char *>
toNullTerminatedCStringArray(ArrayRef<StringRef> Strings, StringSaver &Saver) {
std::vector<const char *> Result;
for (StringRef S : Strings)
Result.push_back(Saver.save(S).data());
Result.push_back(nullptr);
return Result;
}
static bool Execute(ProcessInfo &PI, StringRef Program,
ArrayRef<StringRef> Args, Optional<ArrayRef<StringRef>> Env,
ArrayRef<Optional<StringRef>> Redirects,
unsigned MemoryLimit, std::string *ErrMsg) {
if (!llvm::sys::fs::exists(Program)) {
if (ErrMsg)
*ErrMsg = std::string("Executable \"") + Program.str() +
std::string("\" doesn't exist!");
return false;
}
BumpPtrAllocator Allocator;
StringSaver Saver(Allocator);
std::vector<const char *> ArgVector, EnvVector;
const char **Argv = nullptr;
const char **Envp = nullptr;
ArgVector = toNullTerminatedCStringArray(Args, Saver);
Argv = ArgVector.data();
if (Env) {
EnvVector = toNullTerminatedCStringArray(*Env, Saver);
Envp = EnvVector.data();
}
// If this OS has posix_spawn and there is no memory limit being implied, use
// posix_spawn. It is more efficient than fork/exec.
#ifdef HAVE_POSIX_SPAWN
if (MemoryLimit == 0) {
posix_spawn_file_actions_t FileActionsStore;
posix_spawn_file_actions_t *FileActions = nullptr;
// If we call posix_spawn_file_actions_addopen we have to make sure the
// c strings we pass to it stay alive until the call to posix_spawn,
// so we copy any StringRefs into this variable.
std::string RedirectsStorage[3];
if (!Redirects.empty()) {
assert(Redirects.size() == 3);
std::string *RedirectsStr[3] = {nullptr, nullptr, nullptr};
for (int I = 0; I < 3; ++I) {
if (Redirects[I]) {
RedirectsStorage[I] = *Redirects[I];
RedirectsStr[I] = &RedirectsStorage[I];
}
}
FileActions = &FileActionsStore;
posix_spawn_file_actions_init(FileActions);
// Redirect stdin/stdout.
if (RedirectIO_PS(RedirectsStr[0], 0, ErrMsg, FileActions) ||
RedirectIO_PS(RedirectsStr[1], 1, ErrMsg, FileActions))
return false;
if (!Redirects[1] || !Redirects[2] || *Redirects[1] != *Redirects[2]) {
// Just redirect stderr
if (RedirectIO_PS(RedirectsStr[2], 2, ErrMsg, FileActions))
return false;
} else {
// If stdout and stderr should go to the same place, redirect stderr
// to the FD already open for stdout.
if (int Err = posix_spawn_file_actions_adddup2(FileActions, 1, 2))
return !MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout", Err);
}
}
if (!Envp)
#if !USE_NSGETENVIRON
Envp = const_cast<const char **>(environ);
#else
// environ is missing in dylibs.
Envp = const_cast<const char **>(*_NSGetEnviron());
#endif
constexpr int maxRetries = 8;
int retries = 0;
pid_t PID;
int Err;
do {
PID = 0; // Make Valgrind happy.
Err = posix_spawn(&PID, Program.str().c_str(), FileActions,
/*attrp*/ nullptr, const_cast<char **>(Argv),
const_cast<char **>(Envp));
} while (Err == EINTR && ++retries < maxRetries);
if (FileActions)
posix_spawn_file_actions_destroy(FileActions);
if (Err)
return !MakeErrMsg(ErrMsg, "posix_spawn failed", Err);
PI.Pid = PID;
PI.Process = PID;
return true;
}
#endif
// Create a child process.
int child = fork();
switch (child) {
// An error occurred: Return to the caller.
case -1:
MakeErrMsg(ErrMsg, "Couldn't fork");
return false;
// Child process: Execute the program.
case 0: {
// Redirect file descriptors...
if (!Redirects.empty()) {
// Redirect stdin
if (RedirectIO(Redirects[0], 0, ErrMsg)) { return false; }
// Redirect stdout
if (RedirectIO(Redirects[1], 1, ErrMsg)) { return false; }
if (Redirects[1] && Redirects[2] && *Redirects[1] == *Redirects[2]) {
// If stdout and stderr should go to the same place, redirect stderr
// to the FD already open for stdout.
if (-1 == dup2(1,2)) {
MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout");
return false;
}
} else {
// Just redirect stderr
if (RedirectIO(Redirects[2], 2, ErrMsg)) { return false; }
}
}
// Set memory limits
if (MemoryLimit!=0) {
SetMemoryLimits(MemoryLimit);
}
// Execute!
std::string PathStr = Program;
if (Envp != nullptr)
execve(PathStr.c_str(), const_cast<char **>(Argv),
const_cast<char **>(Envp));
else
execv(PathStr.c_str(), const_cast<char **>(Argv));
// If the execve() failed, we should exit. Follow Unix protocol and
// return 127 if the executable was not found, and 126 otherwise.
// Use _exit rather than exit so that atexit functions and static
// object destructors cloned from the parent process aren't
// redundantly run, and so that any data buffered in stdio buffers
// cloned from the parent aren't redundantly written out.
_exit(errno == ENOENT ? 127 : 126);
}
// Parent process: Break out of the switch to do our processing.
default:
break;
}
PI.Pid = child;
PI.Process = child;
return true;
}
namespace llvm {
ProcessInfo sys::Wait(const ProcessInfo &PI, unsigned SecondsToWait,
bool WaitUntilTerminates, std::string *ErrMsg) {
struct sigaction Act, Old;
assert(PI.Pid && "invalid pid to wait on, process not started?");
int WaitPidOptions = 0;
pid_t ChildPid = PI.Pid;
if (WaitUntilTerminates) {
SecondsToWait = 0;
} else if (SecondsToWait) {
// Install a timeout handler. The handler itself does nothing, but the
// simple fact of having a handler at all causes the wait below to return
// with EINTR, unlike if we used SIG_IGN.
memset(&Act, 0, sizeof(Act));
Act.sa_handler = TimeOutHandler;
sigemptyset(&Act.sa_mask);
sigaction(SIGALRM, &Act, &Old);
alarm(SecondsToWait);
} else if (SecondsToWait == 0)
WaitPidOptions = WNOHANG;
// Parent process: Wait for the child process to terminate.
int status;
ProcessInfo WaitResult;
do {
WaitResult.Pid = waitpid(ChildPid, &status, WaitPidOptions);
} while (WaitUntilTerminates && WaitResult.Pid == -1 && errno == EINTR);
if (WaitResult.Pid != PI.Pid) {
if (WaitResult.Pid == 0) {
// Non-blocking wait.
return WaitResult;
} else {
if (SecondsToWait && errno == EINTR) {
// Kill the child.
kill(PI.Pid, SIGKILL);
// Turn off the alarm and restore the signal handler
alarm(0);
sigaction(SIGALRM, &Old, nullptr);
// Wait for child to die
if (wait(&status) != ChildPid)
MakeErrMsg(ErrMsg, "Child timed out but wouldn't die");
else
MakeErrMsg(ErrMsg, "Child timed out", 0);
WaitResult.ReturnCode = -2; // Timeout detected
return WaitResult;
} else if (errno != EINTR) {
MakeErrMsg(ErrMsg, "Error waiting for child process");
WaitResult.ReturnCode = -1;
return WaitResult;
}
}
}
// We exited normally without timeout, so turn off the timer.
if (SecondsToWait && !WaitUntilTerminates) {
alarm(0);
sigaction(SIGALRM, &Old, nullptr);
}
// Return the proper exit status. Detect error conditions
// so we can return -1 for them and set ErrMsg informatively.
int result = 0;
if (WIFEXITED(status)) {
result = WEXITSTATUS(status);
WaitResult.ReturnCode = result;
if (result == 127) {
if (ErrMsg)
*ErrMsg = llvm::sys::StrError(ENOENT);
WaitResult.ReturnCode = -1;
return WaitResult;
}
if (result == 126) {
if (ErrMsg)
*ErrMsg = "Program could not be executed";
WaitResult.ReturnCode = -1;
return WaitResult;
}
} else if (WIFSIGNALED(status)) {
if (ErrMsg) {
*ErrMsg = strsignal(WTERMSIG(status));
#ifdef WCOREDUMP
if (WCOREDUMP(status))
*ErrMsg += " (core dumped)";
#endif
}
// Return a special value to indicate that the process received an unhandled
// signal during execution as opposed to failing to execute.
WaitResult.ReturnCode = -2;
}
return WaitResult;
}
std::error_code sys::ChangeStdinToBinary() {
// Do nothing, as Unix doesn't differentiate between text and binary.
return std::error_code();
}
std::error_code sys::ChangeStdoutToBinary() {
// Do nothing, as Unix doesn't differentiate between text and binary.
return std::error_code();
}
std::error_code
llvm::sys::writeFileWithEncoding(StringRef FileName, StringRef Contents,
WindowsEncodingMethod Encoding /*unused*/) {
std::error_code EC;
llvm::raw_fd_ostream OS(FileName, EC, llvm::sys::fs::OpenFlags::F_Text);
if (EC)
return EC;
OS << Contents;
if (OS.has_error())
return make_error_code(errc::io_error);
return EC;
}
bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program,
ArrayRef<StringRef> Args) {
static long ArgMax = sysconf(_SC_ARG_MAX);
// POSIX requires that _POSIX_ARG_MAX is 4096, which is the lowest possible
// value for ARG_MAX on a POSIX compliant system.
static long ArgMin = _POSIX_ARG_MAX;
// This the same baseline used by xargs.
long EffectiveArgMax = 128 * 1024;
if (EffectiveArgMax > ArgMax)
EffectiveArgMax = ArgMax;
else if (EffectiveArgMax < ArgMin)
EffectiveArgMax = ArgMin;
// System says no practical limit.
if (ArgMax == -1)
return true;
// Conservatively account for space required by environment variables.
long HalfArgMax = EffectiveArgMax / 2;
size_t ArgLength = Program.size() + 1;
for (StringRef Arg : Args) {
// Ensure that we do not exceed the MAX_ARG_STRLEN constant on Linux, which
// does not have a constant unlike what the man pages would have you
// believe. Since this limit is pretty high, perform the check
// unconditionally rather than trying to be aggressive and limiting it to
// Linux only.
if (Arg.size() >= (32 * 4096))
return false;
ArgLength += Arg.size() + 1;
if (ArgLength > size_t(HalfArgMax)) {
return false;
}
}
return true;
}
}
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