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glib/glib/gspawn.c
Philip Withnall 7cd67c935f gspawn: Add sysprof trace support for spawning 
Use this to replace the much-hated `g_debug()` which told people that
`posix_spawn()` (the fast path) wasn’t being used for various reasons.

If people want to make their process spawning faster now, they’ll have
to use a profiling tool like sysprof to check their program’s
performance. Shocking.

I think I was wrong to put this `g_debug()` in there in the first place
— it hasn’t served its purpose of making people speed up their spawn
paths to use `posix_spawn()`, it’s only cluttered up logs and frustrated
people.

Signed-off-by: Philip Withnall <withnall@endlessm.com>
2020-07-07 11:17:10 +01:00

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/* gspawn.c - Process launching
*
* Copyright 2000 Red Hat, Inc.
* g_execvpe implementation based on GNU libc execvp:
* Copyright 1991, 92, 95, 96, 97, 98, 99 Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h> /* for fdwalk */
#include <dirent.h>
#ifdef HAVE_SPAWN_H
#include <spawn.h>
#endif /* HAVE_SPAWN_H */
#ifdef HAVE_CRT_EXTERNS_H
#include <crt_externs.h> /* for _NSGetEnviron */
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif /* HAVE_SYS_SELECT_H */
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif /* HAVE_SYS_RESOURCE_H */
#if defined(__linux__) || defined(__DragonFly__)
#include <sys/syscall.h> /* for syscall and SYS_getdents64 */
#endif
#include "gspawn.h"
#include "gspawn-private.h"
#include "gthread.h"
#include "gtrace-private.h"
#include "glib/gstdio.h"
#include "genviron.h"
#include "gmem.h"
#include "gshell.h"
#include "gstring.h"
#include "gstrfuncs.h"
#include "gtestutils.h"
#include "gutils.h"
#include "glibintl.h"
#include "glib-unix.h"
/* posix_spawn() is assumed the fastest way to spawn, but glibc's
* implementation was buggy before glibc 2.24, so avoid it on old versions.
*/
#ifdef HAVE_POSIX_SPAWN
#ifdef __GLIBC__
#if __GLIBC_PREREQ(2,24)
#define POSIX_SPAWN_AVAILABLE
#endif
#else /* !__GLIBC__ */
/* Assume that all non-glibc posix_spawn implementations are fine. */
#define POSIX_SPAWN_AVAILABLE
#endif /* __GLIBC__ */
#endif /* HAVE_POSIX_SPAWN */
#ifdef HAVE__NSGETENVIRON
#define environ (*_NSGetEnviron())
#else
extern char **environ;
#endif
#ifndef O_CLOEXEC
#define O_CLOEXEC 0
#else
#define HAVE_O_CLOEXEC 1
#endif
/**
* SECTION:spawn
* @Short_description: process launching
* @Title: Spawning Processes
*
* GLib supports spawning of processes with an API that is more
* convenient than the bare UNIX fork() and exec().
*
* The g_spawn family of functions has synchronous (g_spawn_sync())
* and asynchronous variants (g_spawn_async(), g_spawn_async_with_pipes()),
* as well as convenience variants that take a complete shell-like
* commandline (g_spawn_command_line_sync(), g_spawn_command_line_async()).
*
* See #GSubprocess in GIO for a higher-level API that provides
* stream interfaces for communication with child processes.
*
* An example of using g_spawn_async_with_pipes():
* |[<!-- language="C" -->
* const gchar * const argv[] = { "my-favourite-program", "--args", NULL };
* gint child_stdout, child_stderr;
* GPid child_pid;
* g_autoptr(GError) error = NULL;
*
* // Spawn child process.
* g_spawn_async_with_pipes (NULL, argv, NULL, G_SPAWN_DO_NOT_REAP_CHILD, NULL,
* NULL, &child_pid, NULL, &child_stdout,
* &child_stderr, &error);
* if (error != NULL)
* {
* g_error ("Spawning child failed: %s", error->message);
* return;
* }
*
* // Add a child watch function which will be called when the child process
* // exits.
* g_child_watch_add (child_pid, child_watch_cb, NULL);
*
* // You could watch for output on @child_stdout and @child_stderr using
* // #GUnixInputStream or #GIOChannel here.
*
* static void
* child_watch_cb (GPid pid,
* gint status,
* gpointer user_data)
* {
* g_message ("Child %" G_PID_FORMAT " exited %s", pid,
* g_spawn_check_exit_status (status, NULL) ? "normally" : "abnormally");
*
* // Free any resources associated with the child here, such as I/O channels
* // on its stdout and stderr FDs. If you have no code to put in the
* // child_watch_cb() callback, you can remove it and the g_child_watch_add()
* // call, but you must also remove the G_SPAWN_DO_NOT_REAP_CHILD flag,
* // otherwise the child process will stay around as a zombie until this
* // process exits.
*
* g_spawn_close_pid (pid);
* }
* ]|
*/
static gint safe_close (gint fd);
static gint g_execute (const gchar *file,
gchar **argv,
gchar **argv_buffer,
gsize argv_buffer_len,
gchar **envp,
const gchar *search_path,
gchar *search_path_buffer,
gsize search_path_buffer_len);
static gboolean fork_exec_with_pipes (gboolean intermediate_child,
const gchar *working_directory,
gchar **argv,
gchar **envp,
gboolean close_descriptors,
gboolean search_path,
gboolean search_path_from_envp,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
gboolean cloexec_pipes,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint *standard_input,
gint *standard_output,
gint *standard_error,
GError **error);
static gboolean fork_exec_with_fds (gboolean intermediate_child,
const gchar *working_directory,
gchar **argv,
gchar **envp,
gboolean close_descriptors,
gboolean search_path,
gboolean search_path_from_envp,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
gboolean cloexec_pipes,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint *child_close_fds,
gint stdin_fd,
gint stdout_fd,
gint stderr_fd,
GError **error);
G_DEFINE_QUARK (g-exec-error-quark, g_spawn_error)
G_DEFINE_QUARK (g-spawn-exit-error-quark, g_spawn_exit_error)
/**
* g_spawn_async:
* @working_directory: (type filename) (nullable): child's current working
* directory, or %NULL to inherit parent's
* @argv: (array zero-terminated=1) (element-type filename):
* child's argument vector
* @envp: (array zero-terminated=1) (element-type filename) (nullable):
* child's environment, or %NULL to inherit parent's
* @flags: flags from #GSpawnFlags
* @child_setup: (scope async) (nullable): function to run in the child just before exec()
* @user_data: (closure): user data for @child_setup
* @child_pid: (out) (optional): return location for child process reference, or %NULL
* @error: return location for error
*
* See g_spawn_async_with_pipes() for a full description; this function
* simply calls the g_spawn_async_with_pipes() without any pipes.
*
* You should call g_spawn_close_pid() on the returned child process
* reference when you don't need it any more.
*
* If you are writing a GTK+ application, and the program you are spawning is a
* graphical application too, then to ensure that the spawned program opens its
* windows on the right screen, you may want to use #GdkAppLaunchContext,
* #GAppLaunchContext, or set the %DISPLAY environment variable.
*
* Note that the returned @child_pid on Windows is a handle to the child
* process and not its identifier. Process handles and process identifiers
* are different concepts on Windows.
*
* Returns: %TRUE on success, %FALSE if error is set
**/
gboolean
g_spawn_async (const gchar *working_directory,
gchar **argv,
gchar **envp,
GSpawnFlags flags,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
GError **error)
{
g_return_val_if_fail (argv != NULL, FALSE);
return g_spawn_async_with_pipes (working_directory,
argv, envp,
flags,
child_setup,
user_data,
child_pid,
NULL, NULL, NULL,
error);
}
/* Avoids a danger in threaded situations (calling close()
* on a file descriptor twice, and another thread has
* re-opened it since the first close)
*
* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)).
*/
static void
close_and_invalidate (gint *fd)
{
if (*fd < 0)
return;
else
{
safe_close (*fd);
*fd = -1;
}
}
/* Some versions of OS X define READ_OK in public headers */
#undef READ_OK
typedef enum
{
READ_FAILED = 0, /* FALSE */
READ_OK,
READ_EOF
} ReadResult;
static ReadResult
read_data (GString *str,
gint fd,
GError **error)
{
gssize bytes;
gchar buf[4096];
again:
bytes = read (fd, buf, 4096);
if (bytes == 0)
return READ_EOF;
else if (bytes > 0)
{
g_string_append_len (str, buf, bytes);
return READ_OK;
}
else if (errno == EINTR)
goto again;
else
{
int errsv = errno;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_READ,
_("Failed to read data from child process (%s)"),
g_strerror (errsv));
return READ_FAILED;
}
}
/**
* g_spawn_sync:
* @working_directory: (type filename) (nullable): child's current working
* directory, or %NULL to inherit parent's
* @argv: (array zero-terminated=1) (element-type filename):
* child's argument vector
* @envp: (array zero-terminated=1) (element-type filename) (nullable):
* child's environment, or %NULL to inherit parent's
* @flags: flags from #GSpawnFlags
* @child_setup: (scope async) (nullable): function to run in the child just before exec()
* @user_data: (closure): user data for @child_setup
* @standard_output: (out) (array zero-terminated=1) (element-type guint8) (optional): return location for child output, or %NULL
* @standard_error: (out) (array zero-terminated=1) (element-type guint8) (optional): return location for child error messages, or %NULL
* @exit_status: (out) (optional): return location for child exit status, as returned by waitpid(), or %NULL
* @error: return location for error, or %NULL
*
* Executes a child synchronously (waits for the child to exit before returning).
* All output from the child is stored in @standard_output and @standard_error,
* if those parameters are non-%NULL. Note that you must set the
* %G_SPAWN_STDOUT_TO_DEV_NULL and %G_SPAWN_STDERR_TO_DEV_NULL flags when
* passing %NULL for @standard_output and @standard_error.
*
* If @exit_status is non-%NULL, the platform-specific exit status of
* the child is stored there; see the documentation of
* g_spawn_check_exit_status() for how to use and interpret this.
* Note that it is invalid to pass %G_SPAWN_DO_NOT_REAP_CHILD in
* @flags, and on POSIX platforms, the same restrictions as for
* g_child_watch_source_new() apply.
*
* If an error occurs, no data is returned in @standard_output,
* @standard_error, or @exit_status.
*
* This function calls g_spawn_async_with_pipes() internally; see that
* function for full details on the other parameters and details on
* how these functions work on Windows.
*
* Returns: %TRUE on success, %FALSE if an error was set
*/
gboolean
g_spawn_sync (const gchar *working_directory,
gchar **argv,
gchar **envp,
GSpawnFlags flags,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
gchar **standard_output,
gchar **standard_error,
gint *exit_status,
GError **error)
{
gint outpipe = -1;
gint errpipe = -1;
GPid pid;
gint ret;
GString *outstr = NULL;
GString *errstr = NULL;
gboolean failed;
gint status;
g_return_val_if_fail (argv != NULL, FALSE);
g_return_val_if_fail (!(flags & G_SPAWN_DO_NOT_REAP_CHILD), FALSE);
g_return_val_if_fail (standard_output == NULL ||
!(flags & G_SPAWN_STDOUT_TO_DEV_NULL), FALSE);
g_return_val_if_fail (standard_error == NULL ||
!(flags & G_SPAWN_STDERR_TO_DEV_NULL), FALSE);
/* Just to ensure segfaults if callers try to use
* these when an error is reported.
*/
if (standard_output)
*standard_output = NULL;
if (standard_error)
*standard_error = NULL;
if (!fork_exec_with_pipes (FALSE,
working_directory,
argv,
envp,
!(flags & G_SPAWN_LEAVE_DESCRIPTORS_OPEN),
(flags & G_SPAWN_SEARCH_PATH) != 0,
(flags & G_SPAWN_SEARCH_PATH_FROM_ENVP) != 0,
(flags & G_SPAWN_STDOUT_TO_DEV_NULL) != 0,
(flags & G_SPAWN_STDERR_TO_DEV_NULL) != 0,
(flags & G_SPAWN_CHILD_INHERITS_STDIN) != 0,
(flags & G_SPAWN_FILE_AND_ARGV_ZERO) != 0,
(flags & G_SPAWN_CLOEXEC_PIPES) != 0,
child_setup,
user_data,
&pid,
NULL,
standard_output ? &outpipe : NULL,
standard_error ? &errpipe : NULL,
error))
return FALSE;
/* Read data from child. */
failed = FALSE;
if (outpipe >= 0)
{
outstr = g_string_new (NULL);
}
if (errpipe >= 0)
{
errstr = g_string_new (NULL);
}
/* Read data until we get EOF on both pipes. */
while (!failed &&
(outpipe >= 0 ||
errpipe >= 0))
{
/* Any negative FD in the array is ignored, so we can use a fixed length.
* We can use UNIX FDs here without worrying about Windows HANDLEs because
* the Windows implementation is entirely in gspawn-win32.c. */
GPollFD fds[] =
{
{ outpipe, G_IO_IN | G_IO_HUP | G_IO_ERR, 0 },
{ errpipe, G_IO_IN | G_IO_HUP | G_IO_ERR, 0 },
};
ret = g_poll (fds, G_N_ELEMENTS (fds), -1 /* no timeout */);
if (ret < 0)
{
int errsv = errno;
if (errno == EINTR)
continue;
failed = TRUE;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_READ,
_("Unexpected error in reading data from a child process (%s)"),
g_strerror (errsv));
break;
}
if (outpipe >= 0 && fds[0].revents != 0)
{
switch (read_data (outstr, outpipe, error))
{
case READ_FAILED:
failed = TRUE;
break;
case READ_EOF:
close_and_invalidate (&outpipe);
outpipe = -1;
break;
default:
break;
}
if (failed)
break;
}
if (errpipe >= 0 && fds[1].revents != 0)
{
switch (read_data (errstr, errpipe, error))
{
case READ_FAILED:
failed = TRUE;
break;
case READ_EOF:
close_and_invalidate (&errpipe);
errpipe = -1;
break;
default:
break;
}
if (failed)
break;
}
}
/* These should only be open still if we had an error. */
if (outpipe >= 0)
close_and_invalidate (&outpipe);
if (errpipe >= 0)
close_and_invalidate (&errpipe);
/* Wait for child to exit, even if we have
* an error pending.
*/
again:
ret = waitpid (pid, &status, 0);
if (ret < 0)
{
if (errno == EINTR)
goto again;
else if (errno == ECHILD)
{
if (exit_status)
{
g_warning ("In call to g_spawn_sync(), exit status of a child process was requested but ECHILD was received by waitpid(). See the documentation of g_child_watch_source_new() for possible causes.");
}
else
{
/* We don't need the exit status. */
}
}
else
{
if (!failed) /* avoid error pileups */
{
int errsv = errno;
failed = TRUE;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_READ,
_("Unexpected error in waitpid() (%s)"),
g_strerror (errsv));
}
}
}
if (failed)
{
if (outstr)
g_string_free (outstr, TRUE);
if (errstr)
g_string_free (errstr, TRUE);
return FALSE;
}
else
{
if (exit_status)
*exit_status = status;
if (standard_output)
*standard_output = g_string_free (outstr, FALSE);
if (standard_error)
*standard_error = g_string_free (errstr, FALSE);
return TRUE;
}
}
/**
* g_spawn_async_with_pipes:
* @working_directory: (type filename) (nullable): child's current working
* directory, or %NULL to inherit parent's, in the GLib file name encoding
* @argv: (array zero-terminated=1) (element-type filename): child's argument
* vector, in the GLib file name encoding
* @envp: (array zero-terminated=1) (element-type filename) (nullable):
* child's environment, or %NULL to inherit parent's, in the GLib file
* name encoding
* @flags: flags from #GSpawnFlags
* @child_setup: (scope async) (nullable): function to run in the child just before exec()
* @user_data: (closure): user data for @child_setup
* @child_pid: (out) (optional): return location for child process ID, or %NULL
* @standard_input: (out) (optional): return location for file descriptor to write to child's stdin, or %NULL
* @standard_output: (out) (optional): return location for file descriptor to read child's stdout, or %NULL
* @standard_error: (out) (optional): return location for file descriptor to read child's stderr, or %NULL
* @error: return location for error
*
* Executes a child program asynchronously (your program will not
* block waiting for the child to exit). The child program is
* specified by the only argument that must be provided, @argv.
* @argv should be a %NULL-terminated array of strings, to be passed
* as the argument vector for the child. The first string in @argv
* is of course the name of the program to execute. By default, the
* name of the program must be a full path. If @flags contains the
* %G_SPAWN_SEARCH_PATH flag, the `PATH` environment variable is
* used to search for the executable. If @flags contains the
* %G_SPAWN_SEARCH_PATH_FROM_ENVP flag, the `PATH` variable from
* @envp is used to search for the executable. If both the
* %G_SPAWN_SEARCH_PATH and %G_SPAWN_SEARCH_PATH_FROM_ENVP flags
* are set, the `PATH` variable from @envp takes precedence over
* the environment variable.
*
* If the program name is not a full path and %G_SPAWN_SEARCH_PATH flag is not
* used, then the program will be run from the current directory (or
* @working_directory, if specified); this might be unexpected or even
* dangerous in some cases when the current directory is world-writable.
*
* On Windows, note that all the string or string vector arguments to
* this function and the other g_spawn*() functions are in UTF-8, the
* GLib file name encoding. Unicode characters that are not part of
* the system codepage passed in these arguments will be correctly
* available in the spawned program only if it uses wide character API
* to retrieve its command line. For C programs built with Microsoft's
* tools it is enough to make the program have a wmain() instead of
* main(). wmain() has a wide character argument vector as parameter.
*
* At least currently, mingw doesn't support wmain(), so if you use
* mingw to develop the spawned program, it should call
* g_win32_get_command_line() to get arguments in UTF-8.
*
* On Windows the low-level child process creation API CreateProcess()
* doesn't use argument vectors, but a command line. The C runtime
* library's spawn*() family of functions (which g_spawn_async_with_pipes()
* eventually calls) paste the argument vector elements together into
* a command line, and the C runtime startup code does a corresponding
* reconstruction of an argument vector from the command line, to be
* passed to main(). Complications arise when you have argument vector
* elements that contain spaces or double quotes. The `spawn*()` functions
* don't do any quoting or escaping, but on the other hand the startup
* code does do unquoting and unescaping in order to enable receiving
* arguments with embedded spaces or double quotes. To work around this
* asymmetry, g_spawn_async_with_pipes() will do quoting and escaping on
* argument vector elements that need it before calling the C runtime
* spawn() function.
*
* The returned @child_pid on Windows is a handle to the child
* process, not its identifier. Process handles and process
* identifiers are different concepts on Windows.
*
* @envp is a %NULL-terminated array of strings, where each string
* has the form `KEY=VALUE`. This will become the child's environment.
* If @envp is %NULL, the child inherits its parent's environment.
*
* @flags should be the bitwise OR of any flags you want to affect the
* function's behaviour. The %G_SPAWN_DO_NOT_REAP_CHILD means that the
* child will not automatically be reaped; you must use a child watch
* (g_child_watch_add()) to be notified about the death of the child process,
* otherwise it will stay around as a zombie process until this process exits.
* Eventually you must call g_spawn_close_pid() on the @child_pid, in order to
* free resources which may be associated with the child process. (On Unix,
* using a child watch is equivalent to calling waitpid() or handling
* the %SIGCHLD signal manually. On Windows, calling g_spawn_close_pid()
* is equivalent to calling CloseHandle() on the process handle returned
* in @child_pid). See g_child_watch_add().
*
* Open UNIX file descriptors marked as `FD_CLOEXEC` will be automatically
* closed in the child process. %G_SPAWN_LEAVE_DESCRIPTORS_OPEN means that
* other open file descriptors will be inherited by the child; otherwise all
* descriptors except stdin/stdout/stderr will be closed before calling exec()
* in the child. %G_SPAWN_SEARCH_PATH means that @argv[0] need not be an
* absolute path, it will be looked for in the `PATH` environment
* variable. %G_SPAWN_SEARCH_PATH_FROM_ENVP means need not be an
* absolute path, it will be looked for in the `PATH` variable from
* @envp. If both %G_SPAWN_SEARCH_PATH and %G_SPAWN_SEARCH_PATH_FROM_ENVP
* are used, the value from @envp takes precedence over the environment.
* %G_SPAWN_STDOUT_TO_DEV_NULL means that the child's standard output
* will be discarded, instead of going to the same location as the parent's
* standard output. If you use this flag, @standard_output must be %NULL.
* %G_SPAWN_STDERR_TO_DEV_NULL means that the child's standard error
* will be discarded, instead of going to the same location as the parent's
* standard error. If you use this flag, @standard_error must be %NULL.
* %G_SPAWN_CHILD_INHERITS_STDIN means that the child will inherit the parent's
* standard input (by default, the child's standard input is attached to
* `/dev/null`). If you use this flag, @standard_input must be %NULL.
* %G_SPAWN_FILE_AND_ARGV_ZERO means that the first element of @argv is
* the file to execute, while the remaining elements are the actual
* argument vector to pass to the file. Normally g_spawn_async_with_pipes()
* uses @argv[0] as the file to execute, and passes all of @argv to the child.
*
* @child_setup and @user_data are a function and user data. On POSIX
* platforms, the function is called in the child after GLib has
* performed all the setup it plans to perform (including creating
* pipes, closing file descriptors, etc.) but before calling exec().
* That is, @child_setup is called just before calling exec() in the
* child. Obviously actions taken in this function will only affect
* the child, not the parent.
*
* On Windows, there is no separate fork() and exec() functionality.
* Child processes are created and run with a single API call,
* CreateProcess(). There is no sensible thing @child_setup
* could be used for on Windows so it is ignored and not called.
*
* If non-%NULL, @child_pid will on Unix be filled with the child's
* process ID. You can use the process ID to send signals to the child,
* or to use g_child_watch_add() (or waitpid()) if you specified the
* %G_SPAWN_DO_NOT_REAP_CHILD flag. On Windows, @child_pid will be
* filled with a handle to the child process only if you specified the
* %G_SPAWN_DO_NOT_REAP_CHILD flag. You can then access the child
* process using the Win32 API, for example wait for its termination
* with the WaitFor*() functions, or examine its exit code with
* GetExitCodeProcess(). You should close the handle with CloseHandle()
* or g_spawn_close_pid() when you no longer need it.
*
* If non-%NULL, the @standard_input, @standard_output, @standard_error
* locations will be filled with file descriptors for writing to the child's
* standard input or reading from its standard output or standard error.
* The caller of g_spawn_async_with_pipes() must close these file descriptors
* when they are no longer in use. If these parameters are %NULL, the
* corresponding pipe won't be created.
*
* If @standard_input is %NULL, the child's standard input is attached to
* `/dev/null` unless %G_SPAWN_CHILD_INHERITS_STDIN is set.
*
* If @standard_error is NULL, the child's standard error goes to the same
* location as the parent's standard error unless %G_SPAWN_STDERR_TO_DEV_NULL
* is set.
*
* If @standard_output is NULL, the child's standard output goes to the same
* location as the parent's standard output unless %G_SPAWN_STDOUT_TO_DEV_NULL
* is set.
*
* @error can be %NULL to ignore errors, or non-%NULL to report errors.
* If an error is set, the function returns %FALSE. Errors are reported
* even if they occur in the child (for example if the executable in
* @argv[0] is not found). Typically the `message` field of returned
* errors should be displayed to users. Possible errors are those from
* the #G_SPAWN_ERROR domain.
*
* If an error occurs, @child_pid, @standard_input, @standard_output,
* and @standard_error will not be filled with valid values.
*
* If @child_pid is not %NULL and an error does not occur then the returned
* process reference must be closed using g_spawn_close_pid().
*
* On modern UNIX platforms, GLib can use an efficient process launching
* codepath driven internally by posix_spawn(). This has the advantage of
* avoiding the fork-time performance costs of cloning the parent process
* address space, and avoiding associated memory overcommit checks that are
* not relevant in the context of immediately executing a distinct process.
* This optimized codepath will be used provided that the following conditions
* are met:
*
* 1. %G_SPAWN_DO_NOT_REAP_CHILD is set
* 2. %G_SPAWN_LEAVE_DESCRIPTORS_OPEN is set
* 3. %G_SPAWN_SEARCH_PATH_FROM_ENVP is not set
* 4. @working_directory is %NULL
* 5. @child_setup is %NULL
* 6. The program is of a recognised binary format, or has a shebang. Otherwise, GLib will have to execute the program through the shell, which is not done using the optimized codepath.
*
* If you are writing a GTK+ application, and the program you are spawning is a
* graphical application too, then to ensure that the spawned program opens its
* windows on the right screen, you may want to use #GdkAppLaunchContext,
* #GAppLaunchContext, or set the %DISPLAY environment variable.
*
* Returns: %TRUE on success, %FALSE if an error was set
*/
gboolean
g_spawn_async_with_pipes (const gchar *working_directory,
gchar **argv,
gchar **envp,
GSpawnFlags flags,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint *standard_input,
gint *standard_output,
gint *standard_error,
GError **error)
{
g_return_val_if_fail (argv != NULL, FALSE);
g_return_val_if_fail (standard_output == NULL ||
!(flags & G_SPAWN_STDOUT_TO_DEV_NULL), FALSE);
g_return_val_if_fail (standard_error == NULL ||
!(flags & G_SPAWN_STDERR_TO_DEV_NULL), FALSE);
/* can't inherit stdin if we have an input pipe. */
g_return_val_if_fail (standard_input == NULL ||
!(flags & G_SPAWN_CHILD_INHERITS_STDIN), FALSE);
return fork_exec_with_pipes (!(flags & G_SPAWN_DO_NOT_REAP_CHILD),
working_directory,
argv,
envp,
!(flags & G_SPAWN_LEAVE_DESCRIPTORS_OPEN),
(flags & G_SPAWN_SEARCH_PATH) != 0,
(flags & G_SPAWN_SEARCH_PATH_FROM_ENVP) != 0,
(flags & G_SPAWN_STDOUT_TO_DEV_NULL) != 0,
(flags & G_SPAWN_STDERR_TO_DEV_NULL) != 0,
(flags & G_SPAWN_CHILD_INHERITS_STDIN) != 0,
(flags & G_SPAWN_FILE_AND_ARGV_ZERO) != 0,
(flags & G_SPAWN_CLOEXEC_PIPES) != 0,
child_setup,
user_data,
child_pid,
standard_input,
standard_output,
standard_error,
error);
}
/**
* g_spawn_async_with_fds:
* @working_directory: (type filename) (nullable): child's current working directory, or %NULL to inherit parent's, in the GLib file name encoding
* @argv: (array zero-terminated=1): child's argument vector, in the GLib file name encoding
* @envp: (array zero-terminated=1) (nullable): child's environment, or %NULL to inherit parent's, in the GLib file name encoding
* @flags: flags from #GSpawnFlags
* @child_setup: (scope async) (nullable): function to run in the child just before exec()
* @user_data: (closure): user data for @child_setup
* @child_pid: (out) (optional): return location for child process ID, or %NULL
* @stdin_fd: file descriptor to use for child's stdin, or -1
* @stdout_fd: file descriptor to use for child's stdout, or -1
* @stderr_fd: file descriptor to use for child's stderr, or -1
* @error: return location for error
*
* Identical to g_spawn_async_with_pipes() but instead of
* creating pipes for the stdin/stdout/stderr, you can pass existing
* file descriptors into this function through the @stdin_fd,
* @stdout_fd and @stderr_fd parameters. The following @flags
* also have their behaviour slightly tweaked as a result:
*
* %G_SPAWN_STDOUT_TO_DEV_NULL means that the child's standard output
* will be discarded, instead of going to the same location as the parent's
* standard output. If you use this flag, @standard_output must be -1.
* %G_SPAWN_STDERR_TO_DEV_NULL means that the child's standard error
* will be discarded, instead of going to the same location as the parent's
* standard error. If you use this flag, @standard_error must be -1.
* %G_SPAWN_CHILD_INHERITS_STDIN means that the child will inherit the parent's
* standard input (by default, the child's standard input is attached to
* /dev/null). If you use this flag, @standard_input must be -1.
*
* It is valid to pass the same fd in multiple parameters (e.g. you can pass
* a single fd for both stdout and stderr).
*
* Returns: %TRUE on success, %FALSE if an error was set
*
* Since: 2.58
*/
gboolean
g_spawn_async_with_fds (const gchar *working_directory,
gchar **argv,
gchar **envp,
GSpawnFlags flags,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint stdin_fd,
gint stdout_fd,
gint stderr_fd,
GError **error)
{
g_return_val_if_fail (argv != NULL, FALSE);
g_return_val_if_fail (stdout_fd < 0 ||
!(flags & G_SPAWN_STDOUT_TO_DEV_NULL), FALSE);
g_return_val_if_fail (stderr_fd < 0 ||
!(flags & G_SPAWN_STDERR_TO_DEV_NULL), FALSE);
/* can't inherit stdin if we have an input pipe. */
g_return_val_if_fail (stdin_fd < 0 ||
!(flags & G_SPAWN_CHILD_INHERITS_STDIN), FALSE);
return fork_exec_with_fds (!(flags & G_SPAWN_DO_NOT_REAP_CHILD),
working_directory,
argv,
envp,
!(flags & G_SPAWN_LEAVE_DESCRIPTORS_OPEN),
(flags & G_SPAWN_SEARCH_PATH) != 0,
(flags & G_SPAWN_SEARCH_PATH_FROM_ENVP) != 0,
(flags & G_SPAWN_STDOUT_TO_DEV_NULL) != 0,
(flags & G_SPAWN_STDERR_TO_DEV_NULL) != 0,
(flags & G_SPAWN_CHILD_INHERITS_STDIN) != 0,
(flags & G_SPAWN_FILE_AND_ARGV_ZERO) != 0,
(flags & G_SPAWN_CLOEXEC_PIPES) != 0,
child_setup,
user_data,
child_pid,
NULL,
stdin_fd,
stdout_fd,
stderr_fd,
error);
}
/**
* g_spawn_command_line_sync:
* @command_line: (type filename): a command line
* @standard_output: (out) (array zero-terminated=1) (element-type guint8) (optional): return location for child output
* @standard_error: (out) (array zero-terminated=1) (element-type guint8) (optional): return location for child errors
* @exit_status: (out) (optional): return location for child exit status, as returned by waitpid()
* @error: return location for errors
*
* A simple version of g_spawn_sync() with little-used parameters
* removed, taking a command line instead of an argument vector. See
* g_spawn_sync() for full details. @command_line will be parsed by
* g_shell_parse_argv(). Unlike g_spawn_sync(), the %G_SPAWN_SEARCH_PATH flag
* is enabled. Note that %G_SPAWN_SEARCH_PATH can have security
* implications, so consider using g_spawn_sync() directly if
* appropriate. Possible errors are those from g_spawn_sync() and those
* from g_shell_parse_argv().
*
* If @exit_status is non-%NULL, the platform-specific exit status of
* the child is stored there; see the documentation of
* g_spawn_check_exit_status() for how to use and interpret this.
*
* On Windows, please note the implications of g_shell_parse_argv()
* parsing @command_line. Parsing is done according to Unix shell rules, not
* Windows command interpreter rules.
* Space is a separator, and backslashes are
* special. Thus you cannot simply pass a @command_line containing
* canonical Windows paths, like "c:\\program files\\app\\app.exe", as
* the backslashes will be eaten, and the space will act as a
* separator. You need to enclose such paths with single quotes, like
* "'c:\\program files\\app\\app.exe' 'e:\\folder\\argument.txt'".
*
* Returns: %TRUE on success, %FALSE if an error was set
**/
gboolean
g_spawn_command_line_sync (const gchar *command_line,
gchar **standard_output,
gchar **standard_error,
gint *exit_status,
GError **error)
{
gboolean retval;
gchar **argv = NULL;
g_return_val_if_fail (command_line != NULL, FALSE);
if (!g_shell_parse_argv (command_line,
NULL, &argv,
error))
return FALSE;
retval = g_spawn_sync (NULL,
argv,
NULL,
G_SPAWN_SEARCH_PATH,
NULL,
NULL,
standard_output,
standard_error,
exit_status,
error);
g_strfreev (argv);
return retval;
}
/**
* g_spawn_command_line_async:
* @command_line: (type filename): a command line
* @error: return location for errors
*
* A simple version of g_spawn_async() that parses a command line with
* g_shell_parse_argv() and passes it to g_spawn_async(). Runs a
* command line in the background. Unlike g_spawn_async(), the
* %G_SPAWN_SEARCH_PATH flag is enabled, other flags are not. Note
* that %G_SPAWN_SEARCH_PATH can have security implications, so
* consider using g_spawn_async() directly if appropriate. Possible
* errors are those from g_shell_parse_argv() and g_spawn_async().
*
* The same concerns on Windows apply as for g_spawn_command_line_sync().
*
* Returns: %TRUE on success, %FALSE if error is set
**/
gboolean
g_spawn_command_line_async (const gchar *command_line,
GError **error)
{
gboolean retval;
gchar **argv = NULL;
g_return_val_if_fail (command_line != NULL, FALSE);
if (!g_shell_parse_argv (command_line,
NULL, &argv,
error))
return FALSE;
retval = g_spawn_async (NULL,
argv,
NULL,
G_SPAWN_SEARCH_PATH,
NULL,
NULL,
NULL,
error);
g_strfreev (argv);
return retval;
}
/**
* g_spawn_check_exit_status:
* @exit_status: An exit code as returned from g_spawn_sync()
* @error: a #GError
*
* Set @error if @exit_status indicates the child exited abnormally
* (e.g. with a nonzero exit code, or via a fatal signal).
*
* The g_spawn_sync() and g_child_watch_add() family of APIs return an
* exit status for subprocesses encoded in a platform-specific way.
* On Unix, this is guaranteed to be in the same format waitpid() returns,
* and on Windows it is guaranteed to be the result of GetExitCodeProcess().
*
* Prior to the introduction of this function in GLib 2.34, interpreting
* @exit_status required use of platform-specific APIs, which is problematic
* for software using GLib as a cross-platform layer.
*
* Additionally, many programs simply want to determine whether or not
* the child exited successfully, and either propagate a #GError or
* print a message to standard error. In that common case, this function
* can be used. Note that the error message in @error will contain
* human-readable information about the exit status.
*
* The @domain and @code of @error have special semantics in the case
* where the process has an "exit code", as opposed to being killed by
* a signal. On Unix, this happens if WIFEXITED() would be true of
* @exit_status. On Windows, it is always the case.
*
* The special semantics are that the actual exit code will be the
* code set in @error, and the domain will be %G_SPAWN_EXIT_ERROR.
* This allows you to differentiate between different exit codes.
*
* If the process was terminated by some means other than an exit
* status, the domain will be %G_SPAWN_ERROR, and the code will be
* %G_SPAWN_ERROR_FAILED.
*
* This function just offers convenience; you can of course also check
* the available platform via a macro such as %G_OS_UNIX, and use
* WIFEXITED() and WEXITSTATUS() on @exit_status directly. Do not attempt
* to scan or parse the error message string; it may be translated and/or
* change in future versions of GLib.
*
* Returns: %TRUE if child exited successfully, %FALSE otherwise (and
* @error will be set)
*
* Since: 2.34
*/
gboolean
g_spawn_check_exit_status (gint exit_status,
GError **error)
{
gboolean ret = FALSE;
if (WIFEXITED (exit_status))
{
if (WEXITSTATUS (exit_status) != 0)
{
g_set_error (error, G_SPAWN_EXIT_ERROR, WEXITSTATUS (exit_status),
_("Child process exited with code %ld"),
(long) WEXITSTATUS (exit_status));
goto out;
}
}
else if (WIFSIGNALED (exit_status))
{
g_set_error (error, G_SPAWN_ERROR, G_SPAWN_ERROR_FAILED,
_("Child process killed by signal %ld"),
(long) WTERMSIG (exit_status));
goto out;
}
else if (WIFSTOPPED (exit_status))
{
g_set_error (error, G_SPAWN_ERROR, G_SPAWN_ERROR_FAILED,
_("Child process stopped by signal %ld"),
(long) WSTOPSIG (exit_status));
goto out;
}
else
{
g_set_error (error, G_SPAWN_ERROR, G_SPAWN_ERROR_FAILED,
_("Child process exited abnormally"));
goto out;
}
ret = TRUE;
out:
return ret;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gssize
write_all (gint fd, gconstpointer vbuf, gsize to_write)
{
gchar *buf = (gchar *) vbuf;
while (to_write > 0)
{
gssize count = write (fd, buf, to_write);
if (count < 0)
{
if (errno != EINTR)
return FALSE;
}
else
{
to_write -= count;
buf += count;
}
}
return TRUE;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
G_GNUC_NORETURN
static void
write_err_and_exit (gint fd, gint msg)
{
gint en = errno;
write_all (fd, &msg, sizeof(msg));
write_all (fd, &en, sizeof(en));
_exit (1);
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static int
set_cloexec (void *data, gint fd)
{
if (fd >= GPOINTER_TO_INT (data))
fcntl (fd, F_SETFD, FD_CLOEXEC);
return 0;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gint
safe_close (gint fd)
{
gint ret;
do
ret = close (fd);
while (ret < 0 && errno == EINTR);
return ret;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
G_GNUC_UNUSED static int
close_func (void *data, int fd)
{
if (fd >= GPOINTER_TO_INT (data))
(void) safe_close (fd);
return 0;
}
#ifdef __linux__
struct linux_dirent64
{
guint64 d_ino; /* 64-bit inode number */
guint64 d_off; /* 64-bit offset to next structure */
unsigned short d_reclen; /* Size of this dirent */
unsigned char d_type; /* File type */
char d_name[]; /* Filename (null-terminated) */
};
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gint
filename_to_fd (const char *p)
{
char c;
int fd = 0;
const int cutoff = G_MAXINT / 10;
const int cutlim = G_MAXINT % 10;
if (*p == '\0')
return -1;
while ((c = *p++) != '\0')
{
if (c < '0' || c > '9')
return -1;
c -= '0';
/* Check for overflow. */
if (fd > cutoff || (fd == cutoff && c > cutlim))
return -1;
fd = fd * 10 + c;
}
return fd;
}
#endif
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static int
safe_fdwalk (int (*cb)(void *data, int fd), void *data)
{
#if 0
/* Use fdwalk function provided by the system if it is known to be
* async-signal safe.
*
* Currently there are no operating systems known to provide a safe
* implementation, so this section is not used for now.
*/
return fdwalk (cb, data);
#else
/* Fallback implementation of fdwalk. It should be async-signal safe, but it
* may be slow on non-Linux operating systems, especially on systems allowing
* very high number of open file descriptors.
*/
gint open_max = -1;
gint fd;
gint res = 0;
#if 0 && defined(HAVE_SYS_RESOURCE_H)
struct rlimit rl;
#endif
#ifdef __linux__
/* Avoid use of opendir/closedir since these are not async-signal-safe. */
int dir_fd = open ("/proc/self/fd", O_RDONLY | O_DIRECTORY);
if (dir_fd >= 0)
{
char buf[4096];
int pos, nread;
struct linux_dirent64 *de;
while ((nread = syscall (SYS_getdents64, dir_fd, buf, sizeof(buf))) > 0)
{
for (pos = 0; pos < nread; pos += de->d_reclen)
{
de = (struct linux_dirent64 *)(buf + pos);
fd = filename_to_fd (de->d_name);
if (fd < 0 || fd == dir_fd)
continue;
if ((res = cb (data, fd)) != 0)
break;
}
}
safe_close (dir_fd);
return res;
}
/* If /proc is not mounted or not accessible we fall back to the old
* rlimit trick. */
#endif
#if 0 && defined(HAVE_SYS_RESOURCE_H)
/* Use getrlimit() function provided by the system if it is known to be
* async-signal safe.
*
* Currently there are no operating systems known to provide a safe
* implementation, so this section is not used for now.
*/
if (getrlimit (RLIMIT_NOFILE, &rl) == 0 && rl.rlim_max != RLIM_INFINITY)
open_max = rl.rlim_max;
#endif
#if defined(__FreeBSD__) || defined(__OpenBSD__)
/* Use sysconf() function provided by the system if it is known to be
* async-signal safe.
*
* FreeBSD: sysconf() is included in the list of async-signal safe functions
* found in https://man.freebsd.org/sigaction(2).
*
* OpenBSD: sysconf() is included in the list of async-signal safe functions
* found in https://man.openbsd.org/sigaction.2.
*/
if (open_max < 0)
open_max = sysconf (_SC_OPEN_MAX);
#endif
/* Hardcoded fallback: the default process hard limit in Linux as of 2020 */
if (open_max < 0)
open_max = 4096;
for (fd = 0; fd < open_max; fd++)
if ((res = cb (data, fd)) != 0)
break;
return res;
#endif
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static void
safe_closefrom (int lowfd)
{
#if defined(__FreeBSD__) || defined(__OpenBSD__)
/* Use closefrom function provided by the system if it is known to be
* async-signal safe.
*
* FreeBSD: closefrom is included in the list of async-signal safe functions
* found in https://man.freebsd.org/sigaction(2).
*
* OpenBSD: closefrom is not included in the list, but a direct system call
* should be safe to use.
*/
(void) closefrom (lowfd);
#elif defined(__DragonFly__)
/* It is unclear whether closefrom function included in DragonFlyBSD libc_r
* is safe to use because it calls a lot of library functions. It is also
* unclear whether libc_r itself is still being used. Therefore, we do a
* direct system call here ourselves to avoid possible issues.
*/
(void) syscall (SYS_closefrom, lowfd);
#elif defined(F_CLOSEM)
/* NetBSD and AIX have a special fcntl command which does the same thing as
* closefrom. NetBSD also includes closefrom function, which seems to be a
* simple wrapper of the fcntl command.
*/
(void) fcntl (lowfd, F_CLOSEM);
#else
(void) safe_fdwalk (close_func, GINT_TO_POINTER (lowfd));
#endif
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gint
safe_dup2 (gint fd1, gint fd2)
{
gint ret;
do
ret = dup2 (fd1, fd2);
while (ret < 0 && (errno == EINTR || errno == EBUSY));
return ret;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gint
safe_open (const char *path, gint mode)
{
gint ret;
do
ret = open (path, mode);
while (ret < 0 && errno == EINTR);
return ret;
}
enum
{
CHILD_CHDIR_FAILED,
CHILD_EXEC_FAILED,
CHILD_DUP2_FAILED,
CHILD_FORK_FAILED
};
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)) until it calls exec(). */
static void
do_exec (gint child_err_report_fd,
gint stdin_fd,
gint stdout_fd,
gint stderr_fd,
const gchar *working_directory,
gchar **argv,
gchar **argv_buffer,
gsize argv_buffer_len,
gchar **envp,
gboolean close_descriptors,
const gchar *search_path,
gchar *search_path_buffer,
gsize search_path_buffer_len,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
GSpawnChildSetupFunc child_setup,
gpointer user_data)
{
if (working_directory && chdir (working_directory) < 0)
write_err_and_exit (child_err_report_fd,
CHILD_CHDIR_FAILED);
/* Redirect pipes as required */
if (stdin_fd >= 0)
{
/* dup2 can't actually fail here I don't think */
if (safe_dup2 (stdin_fd, 0) < 0)
write_err_and_exit (child_err_report_fd,
CHILD_DUP2_FAILED);
set_cloexec (GINT_TO_POINTER(0), stdin_fd);
}
else if (!child_inherits_stdin)
{
/* Keep process from blocking on a read of stdin */
gint read_null = safe_open ("/dev/null", O_RDONLY);
if (read_null < 0)
write_err_and_exit (child_err_report_fd,
CHILD_DUP2_FAILED);
safe_dup2 (read_null, 0);
close_and_invalidate (&read_null);
}
if (stdout_fd >= 0)
{
/* dup2 can't actually fail here I don't think */
if (safe_dup2 (stdout_fd, 1) < 0)
write_err_and_exit (child_err_report_fd,
CHILD_DUP2_FAILED);
set_cloexec (GINT_TO_POINTER(0), stdout_fd);
}
else if (stdout_to_null)
{
gint write_null = safe_open ("/dev/null", O_WRONLY);
if (write_null < 0)
write_err_and_exit (child_err_report_fd,
CHILD_DUP2_FAILED);
safe_dup2 (write_null, 1);
close_and_invalidate (&write_null);
}
if (stderr_fd >= 0)
{
/* dup2 can't actually fail here I don't think */
if (safe_dup2 (stderr_fd, 2) < 0)
write_err_and_exit (child_err_report_fd,
CHILD_DUP2_FAILED);
set_cloexec (GINT_TO_POINTER(0), stderr_fd);
}
else if (stderr_to_null)
{
gint write_null = safe_open ("/dev/null", O_WRONLY);
safe_dup2 (write_null, 2);
close_and_invalidate (&write_null);
}
/* Close all file descriptors but stdin, stdout and stderr
* before we exec. Note that this includes
* child_err_report_fd, which keeps the parent from blocking
* forever on the other end of that pipe.
*/
if (close_descriptors)
{
if (child_setup == NULL)
{
safe_dup2 (child_err_report_fd, 3);
set_cloexec (GINT_TO_POINTER (0), 3);
safe_closefrom (4);
child_err_report_fd = 3;
}
else
{
safe_fdwalk (set_cloexec, GINT_TO_POINTER (3));
}
}
else
{
/* We need to do child_err_report_fd anyway */
set_cloexec (GINT_TO_POINTER (0), child_err_report_fd);
}
/* Call user function just before we exec */
if (child_setup)
{
(* child_setup) (user_data);
}
g_execute (argv[0],
file_and_argv_zero ? argv + 1 : argv,
argv_buffer, argv_buffer_len,
envp, search_path, search_path_buffer, search_path_buffer_len);
/* Exec failed */
write_err_and_exit (child_err_report_fd,
CHILD_EXEC_FAILED);
}
static gboolean
read_ints (int fd,
gint* buf,
gint n_ints_in_buf,
gint *n_ints_read,
GError **error)
{
gsize bytes = 0;
while (TRUE)
{
gssize chunk;
if (bytes >= sizeof(gint)*2)
break; /* give up, who knows what happened, should not be
* possible.
*/
again:
chunk = read (fd,
((gchar*)buf) + bytes,
sizeof(gint) * n_ints_in_buf - bytes);
if (chunk < 0 && errno == EINTR)
goto again;
if (chunk < 0)
{
int errsv = errno;
/* Some weird shit happened, bail out */
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FAILED,
_("Failed to read from child pipe (%s)"),
g_strerror (errsv));
return FALSE;
}
else if (chunk == 0)
break; /* EOF */
else /* chunk > 0 */
bytes += chunk;
}
*n_ints_read = (gint)(bytes / sizeof(gint));
return TRUE;
}
#ifdef POSIX_SPAWN_AVAILABLE
static gboolean
do_posix_spawn (gchar **argv,
gchar **envp,
gboolean search_path,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
GPid *child_pid,
gint *child_close_fds,
gint stdin_fd,
gint stdout_fd,
gint stderr_fd)
{
pid_t pid;
gchar **argv_pass;
posix_spawnattr_t attr;
posix_spawn_file_actions_t file_actions;
gint parent_close_fds[3];
gint num_parent_close_fds = 0;
GSList *child_close = NULL;
GSList *elem;
sigset_t mask;
int i, r;
if (*argv[0] == '\0')
{
/* We check the simple case first. */
return ENOENT;
}
r = posix_spawnattr_init (&attr);
if (r != 0)
return r;
if (child_close_fds)
{
int i = -1;
while (child_close_fds[++i] != -1)
child_close = g_slist_prepend (child_close,
GINT_TO_POINTER (child_close_fds[i]));
}
r = posix_spawnattr_setflags (&attr, POSIX_SPAWN_SETSIGDEF);
if (r != 0)
goto out_free_spawnattr;
/* Reset some signal handlers that we may use */
sigemptyset (&mask);
sigaddset (&mask, SIGCHLD);
sigaddset (&mask, SIGINT);
sigaddset (&mask, SIGTERM);
sigaddset (&mask, SIGHUP);
r = posix_spawnattr_setsigdefault (&attr, &mask);
if (r != 0)
goto out_free_spawnattr;
r = posix_spawn_file_actions_init (&file_actions);
if (r != 0)
goto out_free_spawnattr;
/* Redirect pipes as required */
if (stdin_fd >= 0)
{
r = posix_spawn_file_actions_adddup2 (&file_actions, stdin_fd, 0);
if (r != 0)
goto out_close_fds;
if (!g_slist_find (child_close, GINT_TO_POINTER (stdin_fd)))
child_close = g_slist_prepend (child_close, GINT_TO_POINTER (stdin_fd));
}
else if (!child_inherits_stdin)
{
/* Keep process from blocking on a read of stdin */
gint read_null = safe_open ("/dev/null", O_RDONLY | O_CLOEXEC);
g_assert (read_null != -1);
parent_close_fds[num_parent_close_fds++] = read_null;
#ifndef HAVE_O_CLOEXEC
fcntl (read_null, F_SETFD, FD_CLOEXEC);
#endif
r = posix_spawn_file_actions_adddup2 (&file_actions, read_null, 0);
if (r != 0)
goto out_close_fds;
}
if (stdout_fd >= 0)
{
r = posix_spawn_file_actions_adddup2 (&file_actions, stdout_fd, 1);
if (r != 0)
goto out_close_fds;
if (!g_slist_find (child_close, GINT_TO_POINTER (stdout_fd)))
child_close = g_slist_prepend (child_close, GINT_TO_POINTER (stdout_fd));
}
else if (stdout_to_null)
{
gint write_null = safe_open ("/dev/null", O_WRONLY | O_CLOEXEC);
g_assert (write_null != -1);
parent_close_fds[num_parent_close_fds++] = write_null;
#ifndef HAVE_O_CLOEXEC
fcntl (write_null, F_SETFD, FD_CLOEXEC);
#endif
r = posix_spawn_file_actions_adddup2 (&file_actions, write_null, 1);
if (r != 0)
goto out_close_fds;
}
if (stderr_fd >= 0)
{
r = posix_spawn_file_actions_adddup2 (&file_actions, stderr_fd, 2);
if (r != 0)
goto out_close_fds;
if (!g_slist_find (child_close, GINT_TO_POINTER (stderr_fd)))
child_close = g_slist_prepend (child_close, GINT_TO_POINTER (stderr_fd));
}
else if (stderr_to_null)
{
gint write_null = safe_open ("/dev/null", O_WRONLY | O_CLOEXEC);
g_assert (write_null != -1);
parent_close_fds[num_parent_close_fds++] = write_null;
#ifndef HAVE_O_CLOEXEC
fcntl (write_null, F_SETFD, FD_CLOEXEC);
#endif
r = posix_spawn_file_actions_adddup2 (&file_actions, write_null, 2);
if (r != 0)
goto out_close_fds;
}
/* Intentionally close the fds in the child as the last file action,
* having been careful not to add the same fd to this list twice.
*
* This is important to allow (e.g.) for the same fd to be passed as stdout
* and stderr (we must not close it before we have dupped it in both places,
* and we must not attempt to close it twice).
*/
for (elem = child_close; elem != NULL; elem = elem->next)
{
r = posix_spawn_file_actions_addclose (&file_actions,
GPOINTER_TO_INT (elem->data));
if (r != 0)
goto out_close_fds;
}
argv_pass = file_and_argv_zero ? argv + 1 : argv;
if (envp == NULL)
envp = environ;
/* Don't search when it contains a slash. */
if (!search_path || strchr (argv[0], '/') != NULL)
r = posix_spawn (&pid, argv[0], &file_actions, &attr, argv_pass, envp);
else
r = posix_spawnp (&pid, argv[0], &file_actions, &attr, argv_pass, envp);
if (r == 0 && child_pid != NULL)
*child_pid = pid;
out_close_fds:
for (i = 0; i < num_parent_close_fds; i++)
close_and_invalidate (&parent_close_fds [i]);
posix_spawn_file_actions_destroy (&file_actions);
out_free_spawnattr:
posix_spawnattr_destroy (&attr);
g_slist_free (child_close);
return r;
}
#endif /* POSIX_SPAWN_AVAILABLE */
static gboolean
fork_exec_with_fds (gboolean intermediate_child,
const gchar *working_directory,
gchar **argv,
gchar **envp,
gboolean close_descriptors,
gboolean search_path,
gboolean search_path_from_envp,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
gboolean cloexec_pipes,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint *child_close_fds,
gint stdin_fd,
gint stdout_fd,
gint stderr_fd,
GError **error)
{
GPid pid = -1;
gint child_err_report_pipe[2] = { -1, -1 };
gint child_pid_report_pipe[2] = { -1, -1 };
guint pipe_flags = cloexec_pipes ? FD_CLOEXEC : 0;
gint status;
const gchar *chosen_search_path;
gchar *search_path_buffer = NULL;
gsize search_path_buffer_len = 0;
gchar **argv_buffer = NULL;
gsize argv_buffer_len = 0;
#ifdef POSIX_SPAWN_AVAILABLE
if (!intermediate_child && working_directory == NULL && !close_descriptors &&
!search_path_from_envp && child_setup == NULL)
{
g_trace_mark (G_TRACE_CURRENT_TIME, 0,
"GLib", "posix_spawn",
"%s", argv[0]);
status = do_posix_spawn (argv,
envp,
search_path,
stdout_to_null,
stderr_to_null,
child_inherits_stdin,
file_and_argv_zero,
child_pid,
child_close_fds,
stdin_fd,
stdout_fd,
stderr_fd);
if (status == 0)
return TRUE;
if (status != ENOEXEC)
{
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FAILED,
_("Failed to spawn child process “%s” (%s)"),
argv[0],
g_strerror (status));
return FALSE;
}
/* posix_spawn is not intended to support script execution. It does in
* some situations on some glibc versions, but that will be fixed.
* So if it fails with ENOEXEC, we fall through to the regular
* gspawn codepath so that script execution can be attempted,
* per standard gspawn behaviour. */
g_debug ("posix_spawn failed (ENOEXEC), fall back to regular gspawn");
}
else
{
g_trace_mark (G_TRACE_CURRENT_TIME, 0,
"GLib", "fork",
"posix_spawn avoided %s%s%s%s%s",
!intermediate_child ? "" : "(automatic reaping requested) ",
working_directory == NULL ? "" : "(workdir specified) ",
!close_descriptors ? "" : "(fd close requested) ",
!search_path_from_envp ? "" : "(using envp for search path) ",
child_setup == NULL ? "" : "(child_setup specified) ");
}
#endif /* POSIX_SPAWN_AVAILABLE */
/* Choose a search path. This has to be done before calling fork()
* as getenv() isn’t async-signal-safe (see `man 7 signal-safety`). */
chosen_search_path = NULL;
if (search_path_from_envp)
chosen_search_path = g_environ_getenv (envp, "PATH");
if (search_path && chosen_search_path == NULL)
chosen_search_path = g_getenv ("PATH");
if (chosen_search_path == NULL)
{
/* There is no 'PATH' in the environment. The default
* * search path in libc is the current directory followed by
* * the path 'confstr' returns for '_CS_PATH'.
* */
/* In GLib we put . last, for security, and don't use the
* * unportable confstr(); UNIX98 does not actually specify
* * what to search if PATH is unset. POSIX may, dunno.
* */
chosen_search_path = "/bin:/usr/bin:.";
}
/* Allocate a buffer which the fork()ed child can use to assemble potential
* paths for the binary to exec(), combining the argv[0] and elements from
* the chosen_search_path. This can’t be done in the child because malloc()
* (or alloca()) are not async-signal-safe (see `man 7 signal-safety`).
*
* Add 2 for the nul terminator and a leading `/`. */
search_path_buffer_len = strlen (chosen_search_path) + strlen (argv[0]) + 2;
search_path_buffer = g_malloc (search_path_buffer_len);
/* And allocate a buffer which is 2 elements longer than @argv, so that if
* script_execute() has to be called later on, it can build a wrapper argv
* array in this buffer. */
argv_buffer_len = g_strv_length (argv) + 2;
argv_buffer = g_new (gchar *, argv_buffer_len);
if (!g_unix_open_pipe (child_err_report_pipe, pipe_flags, error))
{
g_free (search_path_buffer);
g_free (argv_buffer);
return FALSE;
}
if (intermediate_child && !g_unix_open_pipe (child_pid_report_pipe, pipe_flags, error))
goto cleanup_and_fail;
pid = fork ();
if (pid < 0)
{
int errsv = errno;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FORK,
_("Failed to fork (%s)"),
g_strerror (errsv));
goto cleanup_and_fail;
}
else if (pid == 0)
{
/* Immediate child. This may or may not be the child that
* actually execs the new process.
*/
/* Reset some signal handlers that we may use */
signal (SIGCHLD, SIG_DFL);
signal (SIGINT, SIG_DFL);
signal (SIGTERM, SIG_DFL);
signal (SIGHUP, SIG_DFL);
/* Be sure we crash if the parent exits
* and we write to the err_report_pipe
*/
signal (SIGPIPE, SIG_DFL);
/* Close the parent's end of the pipes;
* not needed in the close_descriptors case,
* though
*/
close_and_invalidate (&child_err_report_pipe[0]);
close_and_invalidate (&child_pid_report_pipe[0]);
if (child_close_fds != NULL)
{
int i = -1;
while (child_close_fds[++i] != -1)
close_and_invalidate (&child_close_fds[i]);
}
if (intermediate_child)
{
/* We need to fork an intermediate child that launches the
* final child. The purpose of the intermediate child
* is to exit, so we can waitpid() it immediately.
* Then the grandchild will not become a zombie.
*/
GPid grandchild_pid;
grandchild_pid = fork ();
if (grandchild_pid < 0)
{
/* report -1 as child PID */
write_all (child_pid_report_pipe[1], &grandchild_pid,
sizeof(grandchild_pid));
write_err_and_exit (child_err_report_pipe[1],
CHILD_FORK_FAILED);
}
else if (grandchild_pid == 0)
{
close_and_invalidate (&child_pid_report_pipe[1]);
do_exec (child_err_report_pipe[1],
stdin_fd,
stdout_fd,
stderr_fd,
working_directory,
argv,
argv_buffer,
argv_buffer_len,
envp,
close_descriptors,
chosen_search_path,
search_path_buffer,
search_path_buffer_len,
stdout_to_null,
stderr_to_null,
child_inherits_stdin,
file_and_argv_zero,
child_setup,
user_data);
}
else
{
write_all (child_pid_report_pipe[1], &grandchild_pid, sizeof(grandchild_pid));
close_and_invalidate (&child_pid_report_pipe[1]);
_exit (0);
}
}
else
{
/* Just run the child.
*/
do_exec (child_err_report_pipe[1],
stdin_fd,
stdout_fd,
stderr_fd,
working_directory,
argv,
argv_buffer,
argv_buffer_len,
envp,
close_descriptors,
chosen_search_path,
search_path_buffer,
search_path_buffer_len,
stdout_to_null,
stderr_to_null,
child_inherits_stdin,
file_and_argv_zero,
child_setup,
user_data);
}
}
else
{
/* Parent */
gint buf[2];
gint n_ints = 0;
/* Close the uncared-about ends of the pipes */
close_and_invalidate (&child_err_report_pipe[1]);
close_and_invalidate (&child_pid_report_pipe[1]);
/* If we had an intermediate child, reap it */
if (intermediate_child)
{
wait_again:
if (waitpid (pid, &status, 0) < 0)
{
if (errno == EINTR)
goto wait_again;
else if (errno == ECHILD)
; /* do nothing, child already reaped */
else
g_warning ("waitpid() should not fail in "
"'fork_exec_with_pipes'");
}
}
if (!read_ints (child_err_report_pipe[0],
buf, 2, &n_ints,
error))
goto cleanup_and_fail;
if (n_ints >= 2)
{
/* Error from the child. */
switch (buf[0])
{
case CHILD_CHDIR_FAILED:
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_CHDIR,
_("Failed to change to directory “%s” (%s)"),
working_directory,
g_strerror (buf[1]));
break;
case CHILD_EXEC_FAILED:
g_set_error (error,
G_SPAWN_ERROR,
_g_spawn_exec_err_to_g_error (buf[1]),
_("Failed to execute child process “%s” (%s)"),
argv[0],
g_strerror (buf[1]));
break;
case CHILD_DUP2_FAILED:
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FAILED,
_("Failed to redirect output or input of child process (%s)"),
g_strerror (buf[1]));
break;
case CHILD_FORK_FAILED:
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FORK,
_("Failed to fork child process (%s)"),
g_strerror (buf[1]));
break;
default:
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FAILED,
_("Unknown error executing child process “%s”"),
argv[0]);
break;
}
goto cleanup_and_fail;
}
/* Get child pid from intermediate child pipe. */
if (intermediate_child)
{
n_ints = 0;
if (!read_ints (child_pid_report_pipe[0],
buf, 1, &n_ints, error))
goto cleanup_and_fail;
if (n_ints < 1)
{
int errsv = errno;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_FAILED,
_("Failed to read enough data from child pid pipe (%s)"),
g_strerror (errsv));
goto cleanup_and_fail;
}
else
{
/* we have the child pid */
pid = buf[0];
}
}
/* Success against all odds! return the information */
close_and_invalidate (&child_err_report_pipe[0]);
close_and_invalidate (&child_pid_report_pipe[0]);
g_free (search_path_buffer);
g_free (argv_buffer);
if (child_pid)
*child_pid = pid;
return TRUE;
}
cleanup_and_fail:
/* There was an error from the Child, reap the child to avoid it being
a zombie.
*/
if (pid > 0)
{
wait_failed:
if (waitpid (pid, NULL, 0) < 0)
{
if (errno == EINTR)
goto wait_failed;
else if (errno == ECHILD)
; /* do nothing, child already reaped */
else
g_warning ("waitpid() should not fail in "
"'fork_exec_with_pipes'");
}
}
close_and_invalidate (&child_err_report_pipe[0]);
close_and_invalidate (&child_err_report_pipe[1]);
close_and_invalidate (&child_pid_report_pipe[0]);
close_and_invalidate (&child_pid_report_pipe[1]);
g_free (search_path_buffer);
g_free (argv_buffer);
return FALSE;
}
static gboolean
fork_exec_with_pipes (gboolean intermediate_child,
const gchar *working_directory,
gchar **argv,
gchar **envp,
gboolean close_descriptors,
gboolean search_path,
gboolean search_path_from_envp,
gboolean stdout_to_null,
gboolean stderr_to_null,
gboolean child_inherits_stdin,
gboolean file_and_argv_zero,
gboolean cloexec_pipes,
GSpawnChildSetupFunc child_setup,
gpointer user_data,
GPid *child_pid,
gint *standard_input,
gint *standard_output,
gint *standard_error,
GError **error)
{
guint pipe_flags = cloexec_pipes ? FD_CLOEXEC : 0;
gint stdin_pipe[2] = { -1, -1 };
gint stdout_pipe[2] = { -1, -1 };
gint stderr_pipe[2] = { -1, -1 };
gint child_close_fds[4];
gboolean ret;
if (standard_input && !g_unix_open_pipe (stdin_pipe, pipe_flags, error))
goto cleanup_and_fail;
if (standard_output && !g_unix_open_pipe (stdout_pipe, pipe_flags, error))
goto cleanup_and_fail;
if (standard_error && !g_unix_open_pipe (stderr_pipe, FD_CLOEXEC, error))
goto cleanup_and_fail;
child_close_fds[0] = stdin_pipe[1];
child_close_fds[1] = stdout_pipe[0];
child_close_fds[2] = stderr_pipe[0];
child_close_fds[3] = -1;
ret = fork_exec_with_fds (intermediate_child,
working_directory,
argv,
envp,
close_descriptors,
search_path,
search_path_from_envp,
stdout_to_null,
stderr_to_null,
child_inherits_stdin,
file_and_argv_zero,
pipe_flags,
child_setup,
user_data,
child_pid,
child_close_fds,
stdin_pipe[0],
stdout_pipe[1],
stderr_pipe[1],
error);
if (!ret)
goto cleanup_and_fail;
/* Close the uncared-about ends of the pipes */
close_and_invalidate (&stdin_pipe[0]);
close_and_invalidate (&stdout_pipe[1]);
close_and_invalidate (&stderr_pipe[1]);
if (standard_input)
*standard_input = stdin_pipe[1];
if (standard_output)
*standard_output = stdout_pipe[0];
if (standard_error)
*standard_error = stderr_pipe[0];
return TRUE;
cleanup_and_fail:
close_and_invalidate (&stdin_pipe[0]);
close_and_invalidate (&stdin_pipe[1]);
close_and_invalidate (&stdout_pipe[0]);
close_and_invalidate (&stdout_pipe[1]);
close_and_invalidate (&stderr_pipe[0]);
close_and_invalidate (&stderr_pipe[1]);
return FALSE;
}
/* Based on execvp from GNU C Library */
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)) until it calls exec(). */
static gboolean
script_execute (const gchar *file,
gchar **argv,
gchar **argv_buffer,
gsize argv_buffer_len,
gchar **envp)
{
/* Count the arguments. */
int argc = 0;
while (argv[argc])
++argc;
/* Construct an argument list for the shell. */
if (argc + 2 > argv_buffer_len)
return FALSE;
argv_buffer[0] = (char *) "/bin/sh";
argv_buffer[1] = (char *) file;
while (argc > 0)
{
argv_buffer[argc + 1] = argv[argc];
--argc;
}
/* Execute the shell. */
if (envp)
execve (argv_buffer[0], argv_buffer, envp);
else
execv (argv_buffer[0], argv_buffer);
return TRUE;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)). */
static gchar*
my_strchrnul (const gchar *str, gchar c)
{
gchar *p = (gchar*) str;
while (*p && (*p != c))
++p;
return p;
}
/* This function is called between fork() and exec() and hence must be
* async-signal-safe (see signal-safety(7)) until it calls exec(). */
static gint
g_execute (const gchar *file,
gchar **argv,
gchar **argv_buffer,
gsize argv_buffer_len,
gchar **envp,
const gchar *search_path,
gchar *search_path_buffer,
gsize search_path_buffer_len)
{
if (*file == '\0')
{
/* We check the simple case first. */
errno = ENOENT;
return -1;
}
if (search_path == NULL || strchr (file, '/') != NULL)
{
/* Don't search when it contains a slash. */
if (envp)
execve (file, argv, envp);
else
execv (file, argv);
if (errno == ENOEXEC &&
!script_execute (file, argv, argv_buffer, argv_buffer_len, envp))
{
errno = ENOMEM;
return -1;
}
}
else
{
gboolean got_eacces = 0;
const gchar *path, *p;
gchar *name;
gsize len;
gsize pathlen;
path = search_path;
len = strlen (file) + 1;
pathlen = strlen (path);
name = search_path_buffer;
if (search_path_buffer_len < pathlen + len + 1)
{
errno = ENOMEM;
return -1;
}
/* Copy the file name at the top, including '\0' */
memcpy (name + pathlen + 1, file, len);
name = name + pathlen;
/* And add the slash before the filename */
*name = '/';
p = path;
do
{
char *startp;
path = p;
p = my_strchrnul (path, ':');
if (p == path)
/* Two adjacent colons, or a colon at the beginning or the end
* of 'PATH' means to search the current directory.
*/
startp = name + 1;
else
startp = memcpy (name - (p - path), path, p - path);
/* Try to execute this name. If it works, execv will not return. */
if (envp)
execve (startp, argv, envp);
else
execv (startp, argv);
if (errno == ENOEXEC &&
!script_execute (startp, argv, argv_buffer, argv_buffer_len, envp))
{
errno = ENOMEM;
return -1;
}
switch (errno)
{
case EACCES:
/* Record the we got a 'Permission denied' error. If we end
* up finding no executable we can use, we want to diagnose
* that we did find one but were denied access.
*/
got_eacces = TRUE;
G_GNUC_FALLTHROUGH;
case ENOENT:
#ifdef ESTALE
case ESTALE:
#endif
#ifdef ENOTDIR
case ENOTDIR:
#endif
/* Those errors indicate the file is missing or not executable
* by us, in which case we want to just try the next path
* directory.
*/
break;
case ENODEV:
case ETIMEDOUT:
/* Some strange filesystems like AFS return even
* stranger error numbers. They cannot reasonably mean anything
* else so ignore those, too.
*/
break;
default:
/* Some other error means we found an executable file, but
* something went wrong executing it; return the error to our
* caller.
*/
return -1;
}
}
while (*p++ != '\0');
/* We tried every element and none of them worked. */
if (got_eacces)
/* At least one failure was due to permissions, so report that
* error.
*/
errno = EACCES;
}
/* Return the error from the last attempt (probably ENOENT). */
return -1;
}
/**
* g_spawn_close_pid:
* @pid: The process reference to close
*
* On some platforms, notably Windows, the #GPid type represents a resource
* which must be closed to prevent resource leaking. g_spawn_close_pid()
* is provided for this purpose. It should be used on all platforms, even
* though it doesn't do anything under UNIX.
**/
void
g_spawn_close_pid (GPid pid)
{
}
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