Merge "<spawn.h>: add posix_spawn_file_actions_addchdir_np()/posix_spawn_file_actions_addfchdir_np()."

docs/status.md

@@ -59,6 +59,9 @@ New libc functions in U (API level 34):
   * `close_range` and `copy_file_range` (Linux-specific GNU extensions).
   * `memset_explicit` in <string.h> (C23 addition).
   * `__freadahead` in <stdio_ext.h> (in musl but not glibc).
+  * `posix_spawn_file_actions_addchdir_np` and
+    `posix_spawn_file_actions_addfchdir_np` in <spawn.h> (in musl/glibc
+    and macOS, but not iOS).
 
 New libc behavior in U (API level 34):
   * Support for `%b` and `%B` in the printf/wprintf family, `%b` in the

libc/bionic/spawn.cpp

@@ -68,7 +68,9 @@ static int cloexec_except_stdioe() {
 enum Action {
   kOpen,
   kClose,
-  kDup2
+  kDup2,
+  kChdir,
+  kFchdir,
 };
 
 struct __posix_spawn_file_action {
@@ -93,6 +95,10 @@ struct __posix_spawn_file_action {
     } else if (what == kClose) {
       // Failure to close is ignored.
       close(fd);
+    } else if (what == kChdir) {
+      if (chdir(path) == -1) _exit(127);
+    } else if (what == kFchdir) {
+      if (fchdir(fd) == -1) _exit(127);
     } else {
       // It's a dup2.
       if (fd == new_fd) {
@@ -340,7 +346,7 @@ static int posix_spawn_add_file_action(posix_spawn_file_actions_t* actions,
   if (action == nullptr) return errno;
 
   action->next = nullptr;
-  if (what == kOpen) {
+  if (what == kOpen || what == kChdir) {
     action->path = strdup(path);
     if (action->path == nullptr) {
       free(action);
@@ -380,3 +386,12 @@ int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t* actions, int fd
   if (fd < 0 || new_fd < 0) return EBADF;
   return posix_spawn_add_file_action(actions, kDup2, fd, new_fd, nullptr, 0, 0);
 }
+
+int posix_spawn_file_actions_addchdir_np(posix_spawn_file_actions_t* actions, const char* path) {
+  return posix_spawn_add_file_action(actions, kChdir, -1, -1, path, 0, 0);
+}
+
+int posix_spawn_file_actions_addfchdir_np(posix_spawn_file_actions_t* actions, int fd) {
+  if (fd < 0) return EBADF;
+  return posix_spawn_add_file_action(actions, kFchdir, fd, -1, nullptr, 0, 0);
+}

libc/include/spawn.h

@@ -87,6 +87,9 @@ int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t _Nonnull * _Nonn
 int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t _Nonnull * _Nonnull __actions, int __fd) __INTRODUCED_IN(28);
 int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t _Nonnull * _Nonnull __actions, int __fd, int __new_fd) __INTRODUCED_IN(28);
 
+int posix_spawn_file_actions_addchdir_np(posix_spawn_file_actions_t _Nonnull * _Nonnull __actions, const char* _Nonnull __path) __INTRODUCED_IN(34);
+int posix_spawn_file_actions_addfchdir_np(posix_spawn_file_actions_t _Nonnull * _Nonnull __actions, int __fd) __INTRODUCED_IN(34);
+
 __END_DECLS
 
 #endif

libc/libc.map.txt

@@ -1580,6 +1580,8 @@ LIBC_U { # introduced=UpsideDownCake
     close_range;
     copy_file_range;
     memset_explicit;
+    posix_spawn_file_actions_addchdir_np;
+    posix_spawn_file_actions_addfchdir_np;
 } LIBC_T;
 
 LIBC_PRIVATE {

tests/spawn_test.cpp

@@ -232,18 +232,28 @@ TEST(spawn, posix_spawn_environment) {
 }
 
 TEST(spawn, posix_spawn_file_actions) {
+#if !defined(__GLIBC__)
   int fds[2];
   ASSERT_NE(-1, pipe(fds));
 
   posix_spawn_file_actions_t fa;
   ASSERT_EQ(0, posix_spawn_file_actions_init(&fa));
 
+  // Test addclose and adddup2 by redirecting output to the pipe created above.
   ASSERT_EQ(0, posix_spawn_file_actions_addclose(&fa, fds[0]));
   ASSERT_EQ(0, posix_spawn_file_actions_adddup2(&fa, fds[1], 1));
   ASSERT_EQ(0, posix_spawn_file_actions_addclose(&fa, fds[1]));
   // Check that close(2) failures are ignored by closing the same fd again.
   ASSERT_EQ(0, posix_spawn_file_actions_addclose(&fa, fds[1]));
+  // Open a file directly, to test addopen.
   ASSERT_EQ(0, posix_spawn_file_actions_addopen(&fa, 56, "/proc/version", O_RDONLY, 0));
+  // Test addfchdir by opening the same file a second way...
+  ASSERT_EQ(0, posix_spawn_file_actions_addopen(&fa, 57, "/proc", O_PATH, 0));
+  ASSERT_EQ(0, posix_spawn_file_actions_addfchdir_np(&fa, 57));
+  ASSERT_EQ(0, posix_spawn_file_actions_addopen(&fa, 58, "version", O_RDONLY, 0));
+  // Test addchdir by opening the same file a third way...
+  ASSERT_EQ(0, posix_spawn_file_actions_addchdir_np(&fa, "/"));
+  ASSERT_EQ(0, posix_spawn_file_actions_addopen(&fa, 59, "proc/version", O_RDONLY, 0));
 
   ExecTestHelper eth;
   eth.SetArgs({"ls", "-l", "/proc/self/fd", nullptr});
@@ -259,12 +269,21 @@ TEST(spawn, posix_spawn_file_actions) {
   AssertChildExited(pid, 0);
 
   // We'll know the dup2 worked if we see any ls(1) output in our pipe.
-  // The open we can check manually...
+  // The opens we can check manually (and they implicitly check the chdirs)...
   bool open_to_fd_56_worked = false;
+  bool open_to_fd_58_worked = false;
+  bool open_to_fd_59_worked = false;
   for (const auto& line : android::base::Split(content, "\n")) {
     if (line.find(" 56 -> /proc/version") != std::string::npos) open_to_fd_56_worked = true;
+    if (line.find(" 58 -> /proc/version") != std::string::npos) open_to_fd_58_worked = true;
+    if (line.find(" 59 -> /proc/version") != std::string::npos) open_to_fd_59_worked = true;
   }
-  ASSERT_TRUE(open_to_fd_56_worked);
+  ASSERT_TRUE(open_to_fd_56_worked) << content;
+  ASSERT_TRUE(open_to_fd_58_worked) << content;
+  ASSERT_TRUE(open_to_fd_59_worked) << content;
+#else
+  GTEST_SKIP() << "our old glibc doesn't have the chdirs; newer versions and musl do.";
+#endif
 }
 
 static void CatFileToString(posix_spawnattr_t* sa, const char* path, std::string* content) {