Add a `Symbolizer::GetEnvP()` method that allows symbolizer implementations to customise the environment of the symbolizer binary.

Summary:
This change introduces the `Symbolizer::GetEnvP()` method that returns a
pointer to environment array used for spawning the symbolizer process.
The motivation is to allow implementations to customise the environment
if required.  The default implementation just returns
`__sanitizer::GetEnviron()` which (provided it's implemented) should
preserve the existing behaviours of the various implementations.

This change has been plumbed through the `internal_spawn(...)` and
`StartSubprocess(...)` process spawning implementations.

For the `StartSubprocess()` implementation we need to call `execve()`
rather than `execv()` to pass the environment. However, it appears that
`internal_execve(...)` exists in sanitizer_common so this patch use that
which seems like a nice clean up.

Support in the Windows implementation of
`SymbolizerProcess:StartSymbolizerSubprocess()` has not been added
because the Windows sanitizer runtime doesn't implement `GetEnviron()`.

rdar://problem/58789439

Reviewers: kubamracek, yln, dvyukov, vitalybuka, eugenis, phosek, aizatsky, rnk

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D76666

compiler-rt/lib/sanitizer_common/sanitizer_file.h

@@ -87,8 +87,8 @@ bool IsAbsolutePath(const char *path);
 // The child process will close all fds after STDERR_FILENO
 // before passing control to a program.
 pid_t StartSubprocess(const char *filename, const char *const argv[],
-                      fd_t stdin_fd = kInvalidFd, fd_t stdout_fd = kInvalidFd,
-                      fd_t stderr_fd = kInvalidFd);
+                      const char *const envp[], fd_t stdin_fd = kInvalidFd,
+                      fd_t stdout_fd = kInvalidFd, fd_t stderr_fd = kInvalidFd);
 // Checks if specified process is still running
 bool IsProcessRunning(pid_t pid);
 // Waits for the process to finish and returns its exit code.

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

@@ -246,7 +246,8 @@ int internal_sysctlbyname(const char *sname, void *oldp, uptr *oldlenp,
                       (size_t)newlen);
 }
 
-static fd_t internal_spawn_impl(const char *argv[], pid_t *pid) {
+static fd_t internal_spawn_impl(const char *argv[], const char *envp[],
+                                pid_t *pid) {
   fd_t master_fd = kInvalidFd;
   fd_t slave_fd = kInvalidFd;
 
@@ -302,8 +303,8 @@ static fd_t internal_spawn_impl(const char *argv[], pid_t *pid) {
 
   // posix_spawn
   char **argv_casted = const_cast<char **>(argv);
-  char **env = GetEnviron();
-  res = posix_spawn(pid, argv[0], &acts, &attrs, argv_casted, env);
+  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.
@@ -320,7 +321,7 @@ static fd_t internal_spawn_impl(const char *argv[], pid_t *pid) {
   return fd;
 }
 
-fd_t internal_spawn(const char *argv[], pid_t *pid) {
+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
@@ -335,7 +336,7 @@ fd_t internal_spawn(const char *argv[], pid_t *pid) {
       break;
   }
 
-  fd_t fd = internal_spawn_impl(argv, pid);
+  fd_t fd = internal_spawn_impl(argv, envp, pid);
 
   for (; count > 0; count--) {
     internal_close(low_fds[count]);

compiler-rt/lib/sanitizer_common/sanitizer_posix.h

@@ -63,7 +63,7 @@ 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[], pid_t *pid);
+fd_t internal_spawn(const char *argv[], const char *envp[], pid_t *pid);
 
 int internal_sysctl(const int *name, unsigned int namelen, void *oldp,
                     uptr *oldlenp, const void *newp, uptr newlen);

compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp

@@ -426,7 +426,8 @@ void AdjustStackSize(void *attr_) {
 #endif // !SANITIZER_GO
 
 pid_t StartSubprocess(const char *program, const char *const argv[],
-                      fd_t stdin_fd, fd_t stdout_fd, fd_t stderr_fd) {
+                      const char *const envp[], fd_t stdin_fd, fd_t stdout_fd,
+                      fd_t stderr_fd) {
   auto file_closer = at_scope_exit([&] {
     if (stdin_fd != kInvalidFd) {
       internal_close(stdin_fd);
@@ -469,7 +470,8 @@ pid_t StartSubprocess(const char *program, const char *const argv[],
 
     for (int fd = sysconf(_SC_OPEN_MAX); fd > 2; fd--) internal_close(fd);
 
-    execv(program, const_cast<char **>(&argv[0]));
+    internal_execve(program, const_cast<char **>(&argv[0]),
+                    const_cast<char *const *>(envp));
     internal__exit(1);
   }
 

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_internal.h

@@ -86,6 +86,8 @@ class SymbolizerProcess {
   // Customizable by subclasses.
   virtual bool StartSymbolizerSubprocess();
   virtual bool ReadFromSymbolizer(char *buffer, uptr max_length);
+  // Return the environment to run the symbolizer in.
+  virtual char **GetEnvP() { return GetEnviron(); }
 
  private:
   virtual bool ReachedEndOfOutput(const char *buffer, uptr length) const {

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp

@@ -153,7 +153,7 @@ bool SymbolizerProcess::StartSymbolizerSubprocess() {
 
   if (use_posix_spawn_) {
 #if SANITIZER_MAC
-    fd_t fd = internal_spawn(argv, &pid);
+    fd_t fd = internal_spawn(argv, const_cast<const char **>(GetEnvP()), &pid);
     if (fd == kInvalidFd) {
       Report("WARNING: failed to spawn external symbolizer (errno: %d)\n",
              errno);
@@ -173,7 +173,7 @@ bool SymbolizerProcess::StartSymbolizerSubprocess() {
       return false;
     }
 
-    pid = StartSubprocess(path_, argv, /* stdin */ outfd[0],
+    pid = StartSubprocess(path_, argv, GetEnvP(), /* stdin */ outfd[0],
                           /* stdout */ infd[1]);
     if (pid < 0) {
       internal_close(infd[0]);

compiler-rt/lib/sanitizer_common/sanitizer_win.cpp

@@ -1064,7 +1064,8 @@ char **GetEnviron() {
 }
 
 pid_t StartSubprocess(const char *program, const char *const argv[],
-                      fd_t stdin_fd, fd_t stdout_fd, fd_t stderr_fd) {
+                      const char *const envp[], fd_t stdin_fd, fd_t stdout_fd,
+                      fd_t stderr_fd) {
   // FIXME: implement on this platform
   // Should be implemented based on
   // SymbolizerProcess::StarAtSymbolizerSubprocess

compiler-rt/lib/sanitizer_common/tests/sanitizer_linux_test.cpp

@@ -264,7 +264,7 @@ TEST(SanitizerCommon, StartSubprocessTest) {
   const char *shell = "/bin/sh";
 #endif
   const char *argv[] = {shell, "-c", "echo -n 'hello'", (char *)NULL};
-  int pid = StartSubprocess(shell, argv,
+  int pid = StartSubprocess(shell, argv, GetEnviron(),
                             /* stdin */ kInvalidFd, /* stdout */ pipe_fds[1]);
   ASSERT_GT(pid, 0);