Replace pty with pipe in macOS posix_spawn path

Author: ndrewh

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

@@ -281,53 +281,39 @@ int internal_sysctlbyname(const char *sname, void *oldp, uptr *oldlenp,
                       (size_t)newlen);
 }
 
-static fd_t internal_spawn_impl(const char *argv[], const char *envp[],
-                                pid_t *pid) {
-  fd_t primary_fd = kInvalidFd;
-  fd_t secondary_fd = kInvalidFd;
+bool internal_spawn(const char* argv[], const char* envp[], pid_t* pid,
+                    fd_t fd_stdin, fd_t fd_stdout) {
+  // NOTE: Caller ensures that fd_stdin and fd_stdout are not 0, 1, or 2, since
+  // this can break communication.
 
+  int res;
   auto fd_closer = at_scope_exit([&] {
-    internal_close(primary_fd);
-    internal_close(secondary_fd);
+    internal_close(fd_stdin);
+    internal_close(fd_stdout);
   });
 
-  // We need a new pseudoterminal to avoid buffering problems. The 'atos' tool
-  // in particular detects when it's talking to a pipe and forgets to flush the
-  // output stream after sending a response.
-  primary_fd = posix_openpt(O_RDWR);
-  if (primary_fd == kInvalidFd)
-    return kInvalidFd;
-
-  int res = grantpt(primary_fd) || unlockpt(primary_fd);
-  if (res != 0) return kInvalidFd;
-
-  // Use TIOCPTYGNAME instead of ptsname() to avoid threading problems.
-  char secondary_pty_name[128];
-  res = ioctl(primary_fd, TIOCPTYGNAME, secondary_pty_name);
-  if (res == -1) return kInvalidFd;
-
-  secondary_fd = internal_open(secondary_pty_name, O_RDWR);
-  if (secondary_fd == kInvalidFd)
-    return kInvalidFd;
-
   // File descriptor actions
   posix_spawn_file_actions_t acts;
   res = posix_spawn_file_actions_init(&acts);
-  if (res != 0) return kInvalidFd;
+  if (res != 0)
+    return false;
 
   auto acts_cleanup = at_scope_exit([&] {
     posix_spawn_file_actions_destroy(&acts);
   });
 
-  res = posix_spawn_file_actions_adddup2(&acts, secondary_fd, STDIN_FILENO) ||
-        posix_spawn_file_actions_adddup2(&acts, secondary_fd, STDOUT_FILENO) ||
-        posix_spawn_file_actions_addclose(&acts, secondary_fd);
-  if (res != 0) return kInvalidFd;
+  res = posix_spawn_file_actions_adddup2(&acts, fd_stdin, STDIN_FILENO) ||
+        posix_spawn_file_actions_adddup2(&acts, fd_stdout, STDOUT_FILENO) ||
+        posix_spawn_file_actions_addclose(&acts, fd_stdin) ||
+        posix_spawn_file_actions_addclose(&acts, fd_stdout);
+  if (res != 0)
+    return false;
 
   // Spawn attributes
   posix_spawnattr_t attrs;
   res = posix_spawnattr_init(&attrs);
-  if (res != 0) return kInvalidFd;
+  if (res != 0)
+    return false;
 
   auto attrs_cleanup  = at_scope_exit([&] {
     posix_spawnattr_destroy(&attrs);
@@ -336,50 +322,17 @@ static fd_t internal_spawn_impl(const char *argv[], const char *envp[],
   // In the spawned process, close all file descriptors that are not explicitly
   // described by the file actions object. This is Darwin-specific extension.
   res = posix_spawnattr_setflags(&attrs, POSIX_SPAWN_CLOEXEC_DEFAULT);
-  if (res != 0) return kInvalidFd;
+  if (res != 0)
+    return false;
 
   // posix_spawn
   char **argv_casted = const_cast<char **>(argv);
   char **envp_casted = const_cast<char **>(envp);
   res = posix_spawn(pid, argv[0], &acts, &attrs, argv_casted, envp_casted);
-  if (res != 0) return kInvalidFd;
-
-  // Disable echo in the new terminal, disable CR.
-  struct termios termflags;
-  tcgetattr(primary_fd, &termflags);
-  termflags.c_oflag &= ~ONLCR;
-  termflags.c_lflag &= ~ECHO;
-  tcsetattr(primary_fd, TCSANOW, &termflags);
-
-  // On success, do not close primary_fd on scope exit.
-  fd_t fd = primary_fd;
-  primary_fd = kInvalidFd;
-
-  return fd;
-}
-
-fd_t internal_spawn(const char *argv[], const char *envp[], pid_t *pid) {
-  // The client program may close its stdin and/or stdout and/or stderr thus
-  // allowing open/posix_openpt to reuse file descriptors 0, 1 or 2. In this
-  // case the communication is broken if either the parent or the child tries to
-  // close or duplicate these descriptors. We temporarily reserve these
-  // descriptors here to prevent this.
-  fd_t low_fds[3];
-  size_t count = 0;
-
-  for (; count < 3; count++) {
-    low_fds[count] = posix_openpt(O_RDWR);
-    if (low_fds[count] >= STDERR_FILENO)
-      break;
-  }
-
-  fd_t fd = internal_spawn_impl(argv, envp, pid);
-
-  for (; count > 0; count--) {
-    internal_close(low_fds[count]);
-  }
+  if (res != 0)
+    return false;
 
-  return fd;
+  return true;
 }
 
 uptr internal_rename(const char *oldpath, const char *newpath) {

compiler-rt/lib/sanitizer_common/sanitizer_posix.h

@@ -67,7 +67,8 @@ uptr internal_ptrace(int request, int pid, void *addr, void *data);
 uptr internal_waitpid(int pid, int *status, int options);
 
 int internal_fork();
-fd_t internal_spawn(const char *argv[], const char *envp[], pid_t *pid);
+bool internal_spawn(const char* argv[], const char* envp[], pid_t* pid,
+                    fd_t stdin, fd_t stdout);
 
 int internal_sysctl(const int *name, unsigned int namelen, void *oldp,
                     uptr *oldlenp, const void *newp, uptr newlen);

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp

@@ -156,42 +156,42 @@ bool SymbolizerProcess::StartSymbolizerSubprocess() {
     Printf("\n");
   }
 
+  fd_t infd[2] = {}, outfd[2] = {};
+  if (!CreateTwoHighNumberedPipes(infd, outfd)) {
+    Report(
+        "WARNING: Can't create a socket pair to start "
+        "external symbolizer (errno: %d)\n",
+        errno);
+    return false;
+  }
+
   if (use_posix_spawn_) {
 #  if SANITIZER_APPLE
-    fd_t fd = internal_spawn(argv, const_cast<const char **>(GetEnvP()), &pid);
-    if (fd == kInvalidFd) {
+    bool success = internal_spawn(argv, const_cast<const char**>(GetEnvP()),
+                                  &pid, outfd[0], infd[1]);
+    if (!success) {
       Report("WARNING: failed to spawn external symbolizer (errno: %d)\n",
              errno);
+      internal_close(infd[0]);
+      internal_close(outfd[1]);
       return false;
     }
-
-    input_fd_ = fd;
-    output_fd_ = fd;
 #  else   // SANITIZER_APPLE
     UNIMPLEMENTED();
 #  endif  // SANITIZER_APPLE
   } else {
-    fd_t infd[2] = {}, outfd[2] = {};
-    if (!CreateTwoHighNumberedPipes(infd, outfd)) {
-      Report(
-          "WARNING: Can't create a socket pair to start "
-          "external symbolizer (errno: %d)\n",
-          errno);
-      return false;
-    }
-
     pid = StartSubprocess(path_, argv, GetEnvP(), /* stdin */ outfd[0],
                           /* stdout */ infd[1]);
     if (pid < 0) {
       internal_close(infd[0]);
       internal_close(outfd[1]);
       return false;
     }
-
-    input_fd_ = infd[0];
-    output_fd_ = outfd[1];
   }
 
+  input_fd_ = infd[0];
+  output_fd_ = outfd[1];
+
   CHECK_GT(pid, 0);
 
   // Check that symbolizer subprocess started successfully.