From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Pat DeSantis <pdesantis3@gmail.com>
Date: Mon, 25 Jan 2021 15:53:44 -0500
Subject: darwin,libuv: use posix_spawn
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Spawning child processes in an Electron application with a hardened runtime has become slow in macOS Big Sur.
This patch is a cherry-pick of https://github.com/libuv/libuv/pull/3064. This patch should be removed when Electron's libuv version is updated to a version containing this fix.
Fixes: https://github.com/libuv/libuv/issues/3050
Fixes: https://github.com/electron/electron/issues/26143
PR-URL: https://github.com/libuv/libuv/pull/3064
Authored-by: Juan Pablo Canepa <jpcanepa@gmail.com>
Co-authored-by: Marcello Bastéa-Forte <marcello@descript.com>
Electron patch prepared by: Pat DeSantis <pdesantis3@gmail.com>
diff --git a/deps/uv/src/unix/process.c b/deps/uv/src/unix/process.c
index b021aaeba87d0b466341f40a016ef69e8beb7543..b4e44b049f5da2eccb051a6ec0403f5a401636d3 100644
--- a/deps/uv/src/unix/process.c
+++ b/deps/uv/src/unix/process.c
@@ -26,6 +26,7 @@
#include <stdlib.h>
#include <assert.h>
#include <errno.h>
+#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
@@ -34,8 +35,20 @@
#include <poll.h>
#if defined(__APPLE__) && !TARGET_OS_IPHONE
+# include <spawn.h>
+# include <paths.h>
+# include <sys/kauth.h>
+# include <sys/types.h>
+# include <sys/sysctl.h>
+# include <dlfcn.h>
# include <crt_externs.h>
# define environ (*_NSGetEnviron())
+
+/* macOS 10.14 back does not define this constant */
+# ifndef POSIX_SPAWN_SETSID
+# define POSIX_SPAWN_SETSID 1024
+# endif
+
#else
extern char **environ;
#endif
@@ -44,7 +57,6 @@ extern char **environ;
# include <grp.h>
#endif
-
static void uv__chld(uv_signal_t* handle, int signum) {
uv_process_t* process;
uv_loop_t* loop;
@@ -364,9 +376,8 @@ static void uv__process_child_init(const uv_process_options_t* options,
_exit(127);
}
- if (options->env != NULL) {
+ if (options->env != NULL)
environ = options->env;
- }
/* Reset signal disposition. Use a hard-coded limit because NSIG
* is not fixed on Linux: it's either 32, 34 or 64, depending on
@@ -405,6 +416,476 @@ static void uv__process_child_init(const uv_process_options_t* options,
#endif
+#if defined(__APPLE__)
+typedef struct uv__posix_spawn_fncs_tag {
+ struct {
+ int (*set_uid_np)(const posix_spawnattr_t *, uid_t);
+ int (*set_gid_np)(const posix_spawnattr_t *, gid_t);
+ int (*set_groups_np)(const posix_spawnattr_t*, int, gid_t*, uid_t);
+ } spawnattr;
+
+ struct {
+ int (*addchdir_np)(const posix_spawn_file_actions_t *, const char *);
+ } file_actions;
+} uv__posix_spawn_fncs_t;
+
+
+static uv_once_t posix_spawn_init_once = UV_ONCE_INIT;
+static uv__posix_spawn_fncs_t posix_spawn_fncs;
+static int posix_spawn_can_use_setsid;
+
+
+void uv__spawn_init_posix_spawn_fncs(void) {
+ /* Try to locate all non-portable functions at runtime */
+ posix_spawn_fncs.spawnattr.set_uid_np =
+ dlsym(RTLD_DEFAULT, "posix_spawnattr_set_uid_np");
+ posix_spawn_fncs.spawnattr.set_gid_np =
+ dlsym(RTLD_DEFAULT, "posix_spawnattr_set_gid_np");
+ posix_spawn_fncs.spawnattr.set_groups_np =
+ dlsym(RTLD_DEFAULT, "posix_spawnattr_set_groups_np");
+ posix_spawn_fncs.file_actions.addchdir_np =
+ dlsym(RTLD_DEFAULT, "posix_spawn_file_actions_addchdir_np");
+}
+
+
+void uv__spawn_init_can_use_setsid(void) {
+ static const int MACOS_CATALINA_VERSION_MAJOR = 19;
+ char version_str[256];
+ char* version_major_str;
+ size_t version_str_size = 256;
+ int r;
+ int version_major;
+
+ /* By default, assume failure */
+ posix_spawn_can_use_setsid = 0;
+
+ /* Get a version string */
+ r = sysctlbyname("kern.osrelease", version_str, &version_str_size, NULL, 0);
+ if (r != 0)
+ return;
+
+ /* Try to get the major version number. If not found
+ * fall back to the fork/exec flow */
+ version_major_str = strtok(version_str, ".");
+ if (version_major_str == NULL)
+ return;
+
+ /* Parse the version major as a number. If it is greater than
+ * the major version for macOS Catalina (aka macOS 10.15), then
+ * the POSIX_SPAWN_SETSID flag is available */
+ version_major = atoi(version_major_str);
+ if (version_major >= MACOS_CATALINA_VERSION_MAJOR)
+ posix_spawn_can_use_setsid = 1;
+}
+
+
+void uv__spawn_init_posix_spawn(void) {
+ /* Init handles to all potentially non-defined functions */
+ uv__spawn_init_posix_spawn_fncs();
+
+ /* Init feature detection for POSIX_SPAWN_SETSID flag */
+ uv__spawn_init_can_use_setsid();
+}
+
+
+int uv__spawn_set_posix_spawn_attrs(posix_spawnattr_t* attrs,
+ const uv__posix_spawn_fncs_t* posix_spawn_fncs,
+ const uv_process_options_t* options) {
+ int err;
+ unsigned int flags;
+ sigset_t signal_set;
+
+ err = posix_spawnattr_init(attrs);
+ if (err != 0) {
+ /* If initialization fails, no need to de-init, just return */
+ return err;
+ }
+
+ if (options->flags & UV_PROCESS_SETUID) {
+ if (posix_spawn_fncs->spawnattr.set_uid_np == NULL) {
+ err = ENOSYS;
+ goto error;
+ }
+
+ err = posix_spawn_fncs->spawnattr.set_uid_np(attrs, options->uid);
+ if (err != 0)
+ goto error;
+ }
+
+ if (options->flags & UV_PROCESS_SETGID) {
+ if (posix_spawn_fncs->spawnattr.set_gid_np == NULL) {
+ err = ENOSYS;
+ goto error;
+ }
+
+ err = posix_spawn_fncs->spawnattr.set_gid_np(attrs, options->gid);
+ if (err != 0)
+ goto error;
+ }
+
+ if (options->flags & (UV_PROCESS_SETUID | UV_PROCESS_SETGID)) {
+ /* Using ngroups = 0 implied the group_array is empty, and so
+ * its contents are never traversed. Still the
+ * posix_spawn_set_groups_np function seems to require that the
+ * group_array pointer be non-null */
+ const int ngroups = 0;
+ gid_t group_array = KAUTH_GID_NONE;
+
+ if (posix_spawn_fncs->spawnattr.set_groups_np == NULL) {
+ err = ENOSYS;
+ goto error;
+ }
+
+ /* See the comment on the call to setgroups in uv__process_child_init above
+ * for why this is not a fatal error */
+ SAVE_ERRNO(posix_spawn_fncs->spawnattr.set_groups_np(
+ attrs,
+ ngroups,
+ &group_array,
+ KAUTH_UID_NONE));
+ }
+
+ /* Set flags for spawn behavior
+ * 1) POSIX_SPAWN_CLOEXEC_DEFAULT: (Apple Extension) All descriptors in
+ * the parent will be treated as if they had been created with O_CLOEXEC.
+ * The only fds that will be passed on to the child are those manipulated
+ * by the file actions
+ * 2) POSIX_SPAWN_SETSIGDEF: Signals mentioned in spawn-sigdefault in
+ * the spawn attributes will be reset to behave as their default
+ * 3) POSIX_SPAWN_SETSIGMASK: Signal mask will be set to the value of
+ * spawn-sigmask in attributes
+ * 4) POSIX_SPAWN_SETSID: Make the process a new session leader if a
+ * detached session was requested. */
+ flags = POSIX_SPAWN_CLOEXEC_DEFAULT |
+ POSIX_SPAWN_SETSIGDEF |
+ POSIX_SPAWN_SETSIGMASK;
+ if (options->flags & UV_PROCESS_DETACHED) {
+ /* If running on a version of macOS where this flag is not supported,
+ * revert back to the fork/exec flow. Otherwise posix_spawn will
+ * silently ignore the flag. */
+ if (!posix_spawn_can_use_setsid) {
+ err = ENOSYS;
+ goto error;
+ }
+
+ flags |= POSIX_SPAWN_SETSID;
+ }
+ err = posix_spawnattr_setflags(attrs, flags);
+ if (err != 0)
+ goto error;
+
+ /* Reset all signal the child to their default behavior */
+ sigfillset(&signal_set);
+ err = posix_spawnattr_setsigdefault(attrs, &signal_set);
+ if (err != 0)
+ goto error;
+
+ /* Reset the signal mask for all signals */
+ sigemptyset(&signal_set);
+ err = posix_spawnattr_setsigmask(attrs, &signal_set);
+ if (err != 0)
+ goto error;
+
+ return err;
+
+error:
+ (void) posix_spawnattr_destroy(attrs);
+ return err;
+}
+
+
+int uv__spawn_set_posix_spawn_file_actions(posix_spawn_file_actions_t* actions,
+ const uv__posix_spawn_fncs_t* posix_spawn_fncs,
+ const uv_process_options_t* options,
+ int stdio_count,
+ int (*pipes)[2]) {
+ int fd;
+ int err;
+
+ err = posix_spawn_file_actions_init(actions);
+ if (err != 0) {
+ /* If initialization fails, no need to de-init, just return */
+ return err;
+ }
+
+ /* Set the current working directory if requested */
+ if (options->cwd != NULL) {
+ if (posix_spawn_fncs->file_actions.addchdir_np == NULL) {
+ err = ENOSYS;
+ goto error;
+ }
+
+ err = posix_spawn_fncs->file_actions.addchdir_np(actions, options->cwd);
+ if (err != 0)
+ goto error;
+ }
+
+ /* First, duplicate any required fd into orbit, out of the range of
+ * the descriptors that should be mapped in. */
+ for (fd = 0; fd < stdio_count; fd++) {
+ if (pipes[fd][1] < 0)
+ continue;
+
+ err = posix_spawn_file_actions_adddup2(
+ actions,
+ pipes[fd][1],
+ stdio_count + fd);
+ if (err != 0)
+ goto error;
+ }
+
+ /* Second, move the descriptors into their respective places */
+ for (fd = 0; fd < stdio_count; fd++) {
+ if (pipes[fd][1] < 0)
+ continue;
+
+ err = posix_spawn_file_actions_adddup2(actions, stdio_count + fd, fd);
+ if (err != 0)
+ goto error;
+ }
+
+ /* Finally, close all the superfluous descriptors */
+ for (fd = 0; fd < stdio_count; fd++) {
+ if (pipes[fd][1] < 0)
+ continue;
+
+ err = posix_spawn_file_actions_addclose(actions, stdio_count + fd);
+ if (err != 0)
+ goto error;
+ }
+
+ /* Finally process the standard streams as per documentation */
+ for (fd = 0; fd < 3; fd++) {
+ int oflags;
+ const int mode = 0;
+
+ oflags = fd == 0 ? O_RDONLY : O_RDWR;
+
+ if (pipes[fd][1] != -1) {
+ /* If not ignored, make sure the fd is marked as non-blocking */
+ uv__nonblock_fcntl(pipes[fd][1], 0);
+ } else {
+ /* If ignored, redirect to (or from) /dev/null, */
+ err = posix_spawn_file_actions_addopen(
+ actions,
+ fd,
+ "/dev/null",
+ oflags,
+ mode);
+ if (err != 0)
+ goto error;
+ }
+ }
+
+ return 0;
+
+error:
+ (void) posix_spawn_file_actions_destroy(actions);
+ return err;
+}
+
+char* uv__spawn_find_path_in_env(char** env) {
+ char** env_iterator;
+ const char path_var[] = "PATH=";
+
+ /* Look for an environment variable called PATH in the
+ * provided env array, and return its value if found */
+ for (env_iterator = env; *env_iterator != NULL; env_iterator++) {
+ if (strncmp(*env_iterator, path_var, sizeof(path_var) - 1) == 0) {
+ /* Found "PATH=" at the beginning of the string */
+ return *env_iterator + sizeof(path_var) - 1;
+ }
+ }
+
+ return NULL;
+}
+
+
+int uv__spawn_resolve_and_spawn(const uv_process_options_t* options,
+ posix_spawnattr_t* attrs,
+ posix_spawn_file_actions_t* actions,
+ pid_t* pid) {
+ const char *p;
+ const char *z;
+ const char *path;
+ size_t l;
+ size_t k;
+ int err;
+
+ path = NULL;
+ err = -1;
+
+ /* Short circuit for erroneous case */
+ if (options->file == NULL)
+ return ENOENT;
+
+ /* The environment for the child process is that of the parent unless overriden
+ * by options->env */
+ char** env = environ;
+ if (options->env != NULL)
+ env = options->env;
+
+ /* If options->file contains a slash, posix_spawn/posix_spawnp behave
+ * the same, and don't involve PATH resolution at all. Otherwise, if
+ * options->file does not include a slash, but no custom environment is
+ * to be used, the environment used for path resolution as well for the
+ * child process is that of the parent process, so posix_spawnp is the
+ * way to go. */
+ if (strchr(options->file, '/') != NULL || options->env == NULL)
+ return posix_spawnp(pid, options->file, actions, attrs, options->args, env);
+
+ /* Look for the definition of PATH in the provided env */
+ path = uv__spawn_find_path_in_env(options->env);
+
+ /* The following resolution logic (execvpe emulation) is taken from
+ * https://github.com/JuliaLang/libuv/commit/9af3af617138d6a6de7d72819ed362996ff255d9
+ * and adapted to work around our own situations */
+
+ /* If no path was provided in options->env, use the default value
+ * to look for the executable */
+ if (path == NULL)
+ path = _PATH_DEFPATH;
+
+ k = strnlen(options->file, NAME_MAX + 1);
+ if (k > NAME_MAX)
+ return ENAMETOOLONG;
+
+ l = strnlen(path, PATH_MAX - 1) + 1;
+
+ for (p = path;; p = z) {
+ /* Compose the new process file from the entry in the PATH
+ * environment variable and the actual file name */
+ char b[PATH_MAX + NAME_MAX];
+ z = strchr(p, ':');
+ if (!z)
+ z = p + strlen(p);
+ if ((size_t)(z - p) >= l) {
+ if (!*z++)
+ break;
+
+ continue;
+ }
+ memcpy(b, p, z - p);
+ b[z - p] = '/';
+ memcpy(b + (z - p) + (z > p), options->file, k + 1);
+
+ /* Try to spawn the new process file. If it fails with ENOENT, the
+ * new process file is not in this PATH entry, continue with the next
+ * PATH entry. */
+ err = posix_spawn(pid, b, actions, attrs, options->args, env);
+ if (err != ENOENT)
+ return err;
+
+ if (!*z++)
+ break;
+ }
+
+ return err;
+}
+
+
+int uv__spawn_and_init_child_posix_spawn(const uv_process_options_t* options,
+ int stdio_count,
+ int (*pipes)[2],
+ pid_t* pid,
+ const uv__posix_spawn_fncs_t* posix_spawn_fncs) {
+ int err;
+ posix_spawnattr_t attrs;
+ posix_spawn_file_actions_t actions;
+
+ err = uv__spawn_set_posix_spawn_attrs(&attrs, posix_spawn_fncs, options);
+ if (err != 0)
+ goto error;
+
+ err = uv__spawn_set_posix_spawn_file_actions(
+ &actions,
+ posix_spawn_fncs,
+ options,
+ stdio_count,
+ pipes);
+ if (err != 0) {
+ (void) posix_spawnattr_destroy(&attrs);
+ goto error;
+ }
+
+ /* Try to spawn options->file resolving in the provided environment
+ * if any */
+ err = uv__spawn_resolve_and_spawn(options, &attrs, &actions, pid);
+
+ /* Destroy the actions/attributes */
+ (void) posix_spawn_file_actions_destroy(&actions);
+ (void) posix_spawnattr_destroy(&attrs);
+
+error:
+ /* In an error situation, the attributes and file actions are
+ * already destroyed, only the happy path requires cleanup */
+ return UV__ERR(err);
+}
+#endif
+
+int uv__spawn_and_init_child_fork(const uv_process_options_t* options,
+ int stdio_count,
+ int (*pipes)[2],
+ int error_fd,
+ pid_t* pid) {
+ *pid = fork();
+
+ if (*pid == -1) {
+ /* Failed to fork */
+ return UV__ERR(errno);
+ }
+
+ if (*pid == 0) {
+ /* Fork succeeded, in the child process */
+ uv__process_child_init(options, stdio_count, pipes, error_fd);
+ abort();
+ }
+
+ /* Fork succeeded, in the parent process */
+ return 0;
+}
+
+int uv__spawn_and_init_child(const uv_process_options_t* options,
+ int stdio_count,
+ int (*pipes)[2],
+ int error_fd,
+ pid_t* pid) {
+ int err;
+
+#if defined(__APPLE__)
+ uv_once(&posix_spawn_init_once, uv__spawn_init_posix_spawn);
+
+ /* Special child process spawn case for macOS Big Sur (11.0) onwards
+ *
+ * Big Sur introduced a significant performance degradation on a call to
+ * fork/exec when the process has many pages mmaped in with MAP_JIT, like, say
+ * a javascript interpreter. Electron-based applications, for example,
+ * are impacted; though the magnitude of the impact depends on how much the
+ * app relies on subprocesses.
+ *
+ * On macOS, though, posix_spawn is implemented in a way that does not
+ * exhibit the problem. This block implements the forking and preparation
+ * logic with posix_spawn and its related primitives. It also takes advantage of
+ * the macOS extension POSIX_SPAWN_CLOEXEC_DEFAULT that makes impossible to
+ * leak descriptors to the child process. */
+ err = uv__spawn_and_init_child_posix_spawn(options,
+ stdio_count,
+ pipes,
+ pid,
+ &posix_spawn_fncs);
+
+ /* The posix_spawn flow will return UV_ENOSYS if any of the posix_spawn_x_np
+ * non-standard functions is both _needed_ and _undefined_. In those cases,
+ * default back to the fork/execve strategy. For all other errors, just fail. */
+ if (err != UV_ENOSYS)
+ return err;
+
+#endif
+ err = uv__spawn_and_init_child_fork(options, stdio_count, pipes, error_fd, pid);
+
+ return err;
+}
+
int uv_spawn(uv_loop_t* loop,
uv_process_t* process,
const uv_process_options_t* options) {
@@ -486,21 +967,16 @@ int uv_spawn(uv_loop_t* loop,
/* Acquire write lock to prevent opening new fds in worker threads */
uv_rwlock_wrlock(&loop->cloexec_lock);
- pid = fork();
- if (pid == -1) {
- err = UV__ERR(errno);
+ /* Spawn the child */
+ err = uv__spawn_and_init_child(options, stdio_count, pipes, signal_pipe[1], &pid);
+ if (err != 0) {
uv_rwlock_wrunlock(&loop->cloexec_lock);
uv__close(signal_pipe[0]);
uv__close(signal_pipe[1]);
goto error;
}
- if (pid == 0) {
- uv__process_child_init(options, stdio_count, pipes, signal_pipe[1]);
- abort();
- }
-
/* Release lock in parent process */
uv_rwlock_wrunlock(&loop->cloexec_lock);
uv__close(signal_pipe[1]);