1//===- llvm/Support/Unix/Program.cpp -----------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the Unix specific portion of the Program class.
10//
11//===----------------------------------------------------------------------===//
12
13//===----------------------------------------------------------------------===//
14//=== WARNING: Implementation here must contain only generic UNIX code that
15//===          is guaranteed to work on *all* UNIX variants.
16//===----------------------------------------------------------------------===//
17
18#include "Unix.h"
19#include "llvm/ADT/StringExtras.h"
20#include "llvm/Config/config.h"
21#include "llvm/Support/Compiler.h"
22#include "llvm/Support/Errc.h"
23#include "llvm/Support/FileSystem.h"
24#include "llvm/Support/Path.h"
25#include "llvm/Support/StringSaver.h"
26#include "llvm/Support/raw_ostream.h"
27#if HAVE_SYS_STAT_H
28#include <sys/stat.h>
29#endif
30#if HAVE_SYS_RESOURCE_H
31#include <sys/resource.h>
32#endif
33#if HAVE_SIGNAL_H
34#include <signal.h>
35#endif
36#if HAVE_FCNTL_H
37#include <fcntl.h>
38#endif
39#if HAVE_UNISTD_H
40#include <unistd.h>
41#endif
42#ifdef HAVE_POSIX_SPAWN
43#include <spawn.h>
44
45#if defined(__APPLE__)
46#include <TargetConditionals.h>
47#endif
48
49#if defined(__APPLE__) && !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE)
50#define USE_NSGETENVIRON 1
51#else
52#define USE_NSGETENVIRON 0
53#endif
54
55#if !USE_NSGETENVIRON
56  extern char **environ;
57#else
58#include <crt_externs.h> // _NSGetEnviron
59#endif
60#endif
61
62namespace llvm {
63
64using namespace sys;
65
66ProcessInfo::ProcessInfo() : Pid(0), ReturnCode(0) {}
67
68ErrorOr<std::string> sys::findProgramByName(StringRef Name,
69                                            ArrayRef<StringRef> Paths) {
70  assert(!Name.empty() && "Must have a name!");
71  // Use the given path verbatim if it contains any slashes; this matches
72  // the behavior of sh(1) and friends.
73  if (Name.find('/') != StringRef::npos)
74    return std::string(Name);
75
76  SmallVector<StringRef, 16> EnvironmentPaths;
77  if (Paths.empty())
78    if (const char *PathEnv = std::getenv("PATH")) {
79      SplitString(PathEnv, EnvironmentPaths, ":");
80      Paths = EnvironmentPaths;
81    }
82
83  for (auto Path : Paths) {
84    if (Path.empty())
85      continue;
86
87    // Check to see if this first directory contains the executable...
88    SmallString<128> FilePath(Path);
89    sys::path::append(FilePath, Name);
90    if (sys::fs::can_execute(FilePath.c_str()))
91      return std::string(FilePath.str()); // Found the executable!
92  }
93  return errc::no_such_file_or_directory;
94}
95
96static bool RedirectIO(Optional<StringRef> Path, int FD, std::string* ErrMsg) {
97  if (!Path) // Noop
98    return false;
99  std::string File;
100  if (Path->empty())
101    // Redirect empty paths to /dev/null
102    File = "/dev/null";
103  else
104    File = *Path;
105
106  // Open the file
107  int InFD = open(File.c_str(), FD == 0 ? O_RDONLY : O_WRONLY|O_CREAT, 0666);
108  if (InFD == -1) {
109    MakeErrMsg(ErrMsg, "Cannot open file '" + File + "' for "
110              + (FD == 0 ? "input" : "output"));
111    return true;
112  }
113
114  // Install it as the requested FD
115  if (dup2(InFD, FD) == -1) {
116    MakeErrMsg(ErrMsg, "Cannot dup2");
117    close(InFD);
118    return true;
119  }
120  close(InFD);      // Close the original FD
121  return false;
122}
123
124#ifdef HAVE_POSIX_SPAWN
125static bool RedirectIO_PS(const std::string *Path, int FD, std::string *ErrMsg,
126                          posix_spawn_file_actions_t *FileActions) {
127  if (!Path) // Noop
128    return false;
129  const char *File;
130  if (Path->empty())
131    // Redirect empty paths to /dev/null
132    File = "/dev/null";
133  else
134    File = Path->c_str();
135
136  if (int Err = posix_spawn_file_actions_addopen(
137          FileActions, FD, File,
138          FD == 0 ? O_RDONLY : O_WRONLY | O_CREAT, 0666))
139    return MakeErrMsg(ErrMsg, "Cannot dup2", Err);
140  return false;
141}
142#endif
143
144static void TimeOutHandler(int Sig) {
145}
146
147static void SetMemoryLimits(unsigned size) {
148#if HAVE_SYS_RESOURCE_H && HAVE_GETRLIMIT && HAVE_SETRLIMIT
149  struct rlimit r;
150  __typeof__ (r.rlim_cur) limit = (__typeof__ (r.rlim_cur)) (size) * 1048576;
151
152  // Heap size
153  getrlimit (RLIMIT_DATA, &r);
154  r.rlim_cur = limit;
155  setrlimit (RLIMIT_DATA, &r);
156#ifdef RLIMIT_RSS
157  // Resident set size.
158  getrlimit (RLIMIT_RSS, &r);
159  r.rlim_cur = limit;
160  setrlimit (RLIMIT_RSS, &r);
161#endif
162#endif
163}
164
165}
166
167static std::vector<const char *>
168toNullTerminatedCStringArray(ArrayRef<StringRef> Strings, StringSaver &Saver) {
169  std::vector<const char *> Result;
170  for (StringRef S : Strings)
171    Result.push_back(Saver.save(S).data());
172  Result.push_back(nullptr);
173  return Result;
174}
175
176static bool Execute(ProcessInfo &PI, StringRef Program,
177                    ArrayRef<StringRef> Args, Optional<ArrayRef<StringRef>> Env,
178                    ArrayRef<Optional<StringRef>> Redirects,
179                    unsigned MemoryLimit, std::string *ErrMsg) {
180  if (!llvm::sys::fs::exists(Program)) {
181    if (ErrMsg)
182      *ErrMsg = std::string("Executable \"") + Program.str() +
183                std::string("\" doesn't exist!");
184    return false;
185  }
186
187  BumpPtrAllocator Allocator;
188  StringSaver Saver(Allocator);
189  std::vector<const char *> ArgVector, EnvVector;
190  const char **Argv = nullptr;
191  const char **Envp = nullptr;
192  ArgVector = toNullTerminatedCStringArray(Args, Saver);
193  Argv = ArgVector.data();
194  if (Env) {
195    EnvVector = toNullTerminatedCStringArray(*Env, Saver);
196    Envp = EnvVector.data();
197  }
198
199  // If this OS has posix_spawn and there is no memory limit being implied, use
200  // posix_spawn.  It is more efficient than fork/exec.
201#ifdef HAVE_POSIX_SPAWN
202  if (MemoryLimit == 0) {
203    posix_spawn_file_actions_t FileActionsStore;
204    posix_spawn_file_actions_t *FileActions = nullptr;
205
206    // If we call posix_spawn_file_actions_addopen we have to make sure the
207    // c strings we pass to it stay alive until the call to posix_spawn,
208    // so we copy any StringRefs into this variable.
209    std::string RedirectsStorage[3];
210
211    if (!Redirects.empty()) {
212      assert(Redirects.size() == 3);
213      std::string *RedirectsStr[3] = {nullptr, nullptr, nullptr};
214      for (int I = 0; I < 3; ++I) {
215        if (Redirects[I]) {
216          RedirectsStorage[I] = *Redirects[I];
217          RedirectsStr[I] = &RedirectsStorage[I];
218        }
219      }
220
221      FileActions = &FileActionsStore;
222      posix_spawn_file_actions_init(FileActions);
223
224      // Redirect stdin/stdout.
225      if (RedirectIO_PS(RedirectsStr[0], 0, ErrMsg, FileActions) ||
226          RedirectIO_PS(RedirectsStr[1], 1, ErrMsg, FileActions))
227        return false;
228      if (!Redirects[1] || !Redirects[2] || *Redirects[1] != *Redirects[2]) {
229        // Just redirect stderr
230        if (RedirectIO_PS(RedirectsStr[2], 2, ErrMsg, FileActions))
231          return false;
232      } else {
233        // If stdout and stderr should go to the same place, redirect stderr
234        // to the FD already open for stdout.
235        if (int Err = posix_spawn_file_actions_adddup2(FileActions, 1, 2))
236          return !MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout", Err);
237      }
238    }
239
240    if (!Envp)
241#if !USE_NSGETENVIRON
242      Envp = const_cast<const char **>(environ);
243#else
244      // environ is missing in dylibs.
245      Envp = const_cast<const char **>(*_NSGetEnviron());
246#endif
247
248    // Explicitly initialized to prevent what appears to be a valgrind false
249    // positive.
250    pid_t PID = 0;
251    int Err = posix_spawn(&PID, Program.str().c_str(), FileActions,
252                          /*attrp*/ nullptr, const_cast<char **>(Argv),
253                          const_cast<char **>(Envp));
254
255    if (FileActions)
256      posix_spawn_file_actions_destroy(FileActions);
257
258    if (Err)
259     return !MakeErrMsg(ErrMsg, "posix_spawn failed", Err);
260
261    PI.Pid = PID;
262    PI.Process = PID;
263
264    return true;
265  }
266#endif
267
268  // Create a child process.
269  int child = fork();
270  switch (child) {
271    // An error occurred:  Return to the caller.
272    case -1:
273      MakeErrMsg(ErrMsg, "Couldn't fork");
274      return false;
275
276    // Child process: Execute the program.
277    case 0: {
278      // Redirect file descriptors...
279      if (!Redirects.empty()) {
280        // Redirect stdin
281        if (RedirectIO(Redirects[0], 0, ErrMsg)) { return false; }
282        // Redirect stdout
283        if (RedirectIO(Redirects[1], 1, ErrMsg)) { return false; }
284        if (Redirects[1] && Redirects[2] && *Redirects[1] == *Redirects[2]) {
285          // If stdout and stderr should go to the same place, redirect stderr
286          // to the FD already open for stdout.
287          if (-1 == dup2(1,2)) {
288            MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout");
289            return false;
290          }
291        } else {
292          // Just redirect stderr
293          if (RedirectIO(Redirects[2], 2, ErrMsg)) { return false; }
294        }
295      }
296
297      // Set memory limits
298      if (MemoryLimit!=0) {
299        SetMemoryLimits(MemoryLimit);
300      }
301
302      // Execute!
303      std::string PathStr = Program;
304      if (Envp != nullptr)
305        execve(PathStr.c_str(), const_cast<char **>(Argv),
306               const_cast<char **>(Envp));
307      else
308        execv(PathStr.c_str(), const_cast<char **>(Argv));
309      // If the execve() failed, we should exit. Follow Unix protocol and
310      // return 127 if the executable was not found, and 126 otherwise.
311      // Use _exit rather than exit so that atexit functions and static
312      // object destructors cloned from the parent process aren't
313      // redundantly run, and so that any data buffered in stdio buffers
314      // cloned from the parent aren't redundantly written out.
315      _exit(errno == ENOENT ? 127 : 126);
316    }
317
318    // Parent process: Break out of the switch to do our processing.
319    default:
320      break;
321  }
322
323  PI.Pid = child;
324  PI.Process = child;
325
326  return true;
327}
328
329namespace llvm {
330
331ProcessInfo sys::Wait(const ProcessInfo &PI, unsigned SecondsToWait,
332                      bool WaitUntilTerminates, std::string *ErrMsg) {
333  struct sigaction Act, Old;
334  assert(PI.Pid && "invalid pid to wait on, process not started?");
335
336  int WaitPidOptions = 0;
337  pid_t ChildPid = PI.Pid;
338  if (WaitUntilTerminates) {
339    SecondsToWait = 0;
340  } else if (SecondsToWait) {
341    // Install a timeout handler.  The handler itself does nothing, but the
342    // simple fact of having a handler at all causes the wait below to return
343    // with EINTR, unlike if we used SIG_IGN.
344    memset(&Act, 0, sizeof(Act));
345    Act.sa_handler = TimeOutHandler;
346    sigemptyset(&Act.sa_mask);
347    sigaction(SIGALRM, &Act, &Old);
348    alarm(SecondsToWait);
349  } else if (SecondsToWait == 0)
350    WaitPidOptions = WNOHANG;
351
352  // Parent process: Wait for the child process to terminate.
353  int status;
354  ProcessInfo WaitResult;
355
356  do {
357    WaitResult.Pid = waitpid(ChildPid, &status, WaitPidOptions);
358  } while (WaitUntilTerminates && WaitResult.Pid == -1 && errno == EINTR);
359
360  if (WaitResult.Pid != PI.Pid) {
361    if (WaitResult.Pid == 0) {
362      // Non-blocking wait.
363      return WaitResult;
364    } else {
365      if (SecondsToWait && errno == EINTR) {
366        // Kill the child.
367        kill(PI.Pid, SIGKILL);
368
369        // Turn off the alarm and restore the signal handler
370        alarm(0);
371        sigaction(SIGALRM, &Old, nullptr);
372
373        // Wait for child to die
374        if (wait(&status) != ChildPid)
375          MakeErrMsg(ErrMsg, "Child timed out but wouldn't die");
376        else
377          MakeErrMsg(ErrMsg, "Child timed out", 0);
378
379        WaitResult.ReturnCode = -2; // Timeout detected
380        return WaitResult;
381      } else if (errno != EINTR) {
382        MakeErrMsg(ErrMsg, "Error waiting for child process");
383        WaitResult.ReturnCode = -1;
384        return WaitResult;
385      }
386    }
387  }
388
389  // We exited normally without timeout, so turn off the timer.
390  if (SecondsToWait && !WaitUntilTerminates) {
391    alarm(0);
392    sigaction(SIGALRM, &Old, nullptr);
393  }
394
395  // Return the proper exit status. Detect error conditions
396  // so we can return -1 for them and set ErrMsg informatively.
397  int result = 0;
398  if (WIFEXITED(status)) {
399    result = WEXITSTATUS(status);
400    WaitResult.ReturnCode = result;
401
402    if (result == 127) {
403      if (ErrMsg)
404        *ErrMsg = llvm::sys::StrError(ENOENT);
405      WaitResult.ReturnCode = -1;
406      return WaitResult;
407    }
408    if (result == 126) {
409      if (ErrMsg)
410        *ErrMsg = "Program could not be executed";
411      WaitResult.ReturnCode = -1;
412      return WaitResult;
413    }
414  } else if (WIFSIGNALED(status)) {
415    if (ErrMsg) {
416      *ErrMsg = strsignal(WTERMSIG(status));
417#ifdef WCOREDUMP
418      if (WCOREDUMP(status))
419        *ErrMsg += " (core dumped)";
420#endif
421    }
422    // Return a special value to indicate that the process received an unhandled
423    // signal during execution as opposed to failing to execute.
424    WaitResult.ReturnCode = -2;
425  }
426  return WaitResult;
427}
428
429std::error_code sys::ChangeStdinToBinary() {
430  // Do nothing, as Unix doesn't differentiate between text and binary.
431  return std::error_code();
432}
433
434std::error_code sys::ChangeStdoutToBinary() {
435  // Do nothing, as Unix doesn't differentiate between text and binary.
436  return std::error_code();
437}
438
439std::error_code
440llvm::sys::writeFileWithEncoding(StringRef FileName, StringRef Contents,
441                                 WindowsEncodingMethod Encoding /*unused*/) {
442  std::error_code EC;
443  llvm::raw_fd_ostream OS(FileName, EC, llvm::sys::fs::OpenFlags::F_Text);
444
445  if (EC)
446    return EC;
447
448  OS << Contents;
449
450  if (OS.has_error())
451    return make_error_code(errc::io_error);
452
453  return EC;
454}
455
456bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program,
457                                                  ArrayRef<StringRef> Args) {
458  static long ArgMax = sysconf(_SC_ARG_MAX);
459  // POSIX requires that _POSIX_ARG_MAX is 4096, which is the lowest possible
460  // value for ARG_MAX on a POSIX compliant system.
461  static long ArgMin = _POSIX_ARG_MAX;
462
463  // This the same baseline used by xargs.
464  long EffectiveArgMax = 128 * 1024;
465
466  if (EffectiveArgMax > ArgMax)
467    EffectiveArgMax = ArgMax;
468  else if (EffectiveArgMax < ArgMin)
469    EffectiveArgMax = ArgMin;
470
471  // System says no practical limit.
472  if (ArgMax == -1)
473    return true;
474
475  // Conservatively account for space required by environment variables.
476  long HalfArgMax = EffectiveArgMax / 2;
477
478  size_t ArgLength = Program.size() + 1;
479  for (StringRef Arg : Args) {
480    // Ensure that we do not exceed the MAX_ARG_STRLEN constant on Linux, which
481    // does not have a constant unlike what the man pages would have you
482    // believe. Since this limit is pretty high, perform the check
483    // unconditionally rather than trying to be aggressive and limiting it to
484    // Linux only.
485    if (Arg.size() >= (32 * 4096))
486      return false;
487
488    ArgLength += Arg.size() + 1;
489    if (ArgLength > size_t(HalfArgMax)) {
490      return false;
491    }
492  }
493
494  return true;
495}
496}
497