librt: add posix_spawn support

Signed-off-by: Ismael Luceno <ismael.luceno@gmail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 259 insertions, 0 deletions

diff --git a/librt/spawn.c b/librt/spawn.c
new file mode 100644
index 000000000..b5935a1b4
--- /dev/null
+++ b/librt/spawn.c
@@ -0,0 +1,259 @@
+/* Copyright (C) 2000, 2011 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C 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.
+
+   The GNU C 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 the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <alloca.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <fcntl.h>
+
+#include <sys/resource.h>
+#include <not-cancel.h>
+
+#include <spawn.h>
+#include "spawn_int.h"
+
+/* The Unix standard contains a long explanation of the way to signal
+   an error after the fork() was successful.  Since no new wait status
+   was wanted there is no way to signal an error using one of the
+   available methods.  The committee chose to signal an error by a
+   normal program exit with the exit code 127.  */
+#define SPAWN_ERROR	127
+
+/* Execute file actions.
+ * Returns true on error.
+ */
+inline static bool execute_file_actions(const posix_spawn_file_actions_t *fa)
+{
+	struct rlimit64 fdlimit;
+	bool have_fdlimit = false;
+
+	for (int cnt = 0; cnt < fa->__used; ++cnt) {
+		struct __spawn_action *action = &fa->__actions[cnt];
+
+		switch (action->tag) {
+		case spawn_do_close:
+			if (close_not_cancel(action->action.close_action.fd) != 0) {
+				if (!have_fdlimit) {
+					getrlimit64(RLIMIT_NOFILE, &fdlimit);
+					have_fdlimit = true;
+				}
+
+				/* Only signal errors for file descriptors out of range.  */
+				if (0 > action->action.close_action.fd
+				    || action->action.close_action.fd >= fdlimit.rlim_cur)
+					/* Signal the error.  */
+					return true;
+			}
+			break;
+
+		case spawn_do_open:;
+			int new_fd = open_not_cancel(action->action.open_action.path,
+						     action->action.open_action.oflag
+						     | O_LARGEFILE,
+						     action->action.open_action.mode);
+
+			if (new_fd == -1)
+				return true;
+
+			/* Make sure the desired file descriptor is used.  */
+			if (new_fd != action->action.open_action.fd) {
+				if (dup2(new_fd, action->action.open_action.fd)
+				    != action->action.open_action.fd)
+					return true;
+
+				if (close_not_cancel(new_fd) != 0)
+					return true;
+			}
+			break;
+
+		case spawn_do_dup2:
+			if (dup2(action->action.dup2_action.fd,
+				   action->action.dup2_action.newfd)
+			    != action->action.dup2_action.newfd)
+				return true;
+			break;
+		}
+	}
+
+	return false;
+}
+
+#define DANGEROUS (POSIX_SPAWN_SETSIGMASK		\
+		   | POSIX_SPAWN_SETSIGDEF		\
+		   | POSIX_SPAWN_SETSCHEDPARAM		\
+		   | POSIX_SPAWN_SETSCHEDULER		\
+		   | POSIX_SPAWN_SETPGROUP		\
+		   | POSIX_SPAWN_RESETIDS)
+inline static bool is_vfork_safe(short int flags)
+{
+	return ((flags & POSIX_SPAWN_USEVFORK) || !(flags & DANGEROUS));
+}
+
+
+/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+static int
+__spawni(pid_t *pid, const char *file,
+	 const posix_spawn_file_actions_t *fa,
+	 const posix_spawnattr_t *attrp, char *const argv[],
+	 char *const envp[], const char *path)
+{
+	short int flags = attrp ? attrp->__flags : 0;
+
+	pid_t new_pid;
+	if (is_vfork_safe(flags) && !fa)
+		new_pid = vfork();
+	else
+		new_pid = fork();
+
+	if (new_pid) {
+		if (new_pid < 0)
+			return errno;
+
+		if (pid)
+			*pid = new_pid;
+
+		return 0;
+	}
+
+	if (flags & POSIX_SPAWN_SETSIGMASK) {
+		if (sigprocmask(SIG_SETMASK, &attrp->__ss, NULL) != 0)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_SETSIGDEF) {
+		/* We have to iterate over all signals.  This could possibly be
+		   done better but it requires system specific solutions since
+		   the sigset_t data type can be very different on different
+		   architectures.  */
+		struct sigaction sa;
+
+		memset(&sa, 0, sizeof(sa));
+		sa.sa_handler = SIG_DFL;
+
+		for (int sig = 1; sig <= _NSIG; ++sig) {
+			if (sigismember(&attrp->__sd, sig)) {
+				if (sigaction(sig, &sa, NULL) != 0)
+					goto error;
+			}
+		}
+	}
+
+	if (flags & POSIX_SPAWN_SETSCHEDULER) {
+		if (sched_setscheduler(0, attrp->__policy, &attrp->__sp) == -1)
+			goto error;
+	} else if (flags & POSIX_SPAWN_SETSCHEDPARAM) {
+		if (sched_setparam(0, &attrp->__sp) == -1)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_SETPGROUP) {
+		if (setpgid(0, attrp->__pgrp) != 0)
+			goto error;
+	}
+
+	if (flags & POSIX_SPAWN_RESETIDS) {
+		if (seteuid(getuid()) || setegid(getgid()))
+			goto error;
+	}
+
+	if (fa && execute_file_actions(fa))
+		goto error;
+
+	if (!path || strchr(file, '/')) {
+		execve(file, argv, envp);
+		goto error;
+	}
+
+
+	char *name;
+	{
+		size_t filelen = strlen(file) + 1;
+		size_t pathlen = strlen(path) + 1;
+		name = alloca(pathlen + filelen);
+
+		/* Copy the file name at the top. */
+		name = (char *) memcpy(name + pathlen, file, filelen);
+
+		/* And add the slash.  */
+		*--name = '/';
+	}
+
+	char *p;
+	do {
+		char *startp;
+		p = strchrnul(path, ':');
+
+		/* Two adjacent colons, or a colon at the beginning or the end
+		   of `PATH' means to search the current directory.  */
+		if (p == path)
+			startp = name + 1;
+		else
+			startp = (char *) memcpy(name - (p - path), path, p - path);
+
+		execve(startp, argv, envp);
+
+		switch (errno) {
+		case EACCES:
+		case ENOENT:
+		case ESTALE:
+		case ENOTDIR:
+			/* 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;
+		default:
+			/* Some other error means we found an executable file,
+			   but something went wrong executing it; return the
+			   error to our caller. */
+			goto error;
+		}
+
+		path = p;
+	} while (*p++ != '\0');
+
+error:
+	_exit(SPAWN_ERROR);
+}
+
+/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+int posix_spawn (pid_t *pid, const char *path,
+	       const posix_spawn_file_actions_t *fa,
+	       const posix_spawnattr_t *attrp, char *const argv[],
+	       char *const envp[])
+{
+	return __spawni(pid, path, fa, attrp, argv, envp, NULL);
+}
+
+/* Spawn a new process executing FILE with the attributes describes in *ATTRP.
+   Before running the process perform the actions described in FILE-ACTIONS. */
+int
+posix_spawnp(pid_t *pid, const char *file,
+	     const posix_spawn_file_actions_t *fa,
+	     const posix_spawnattr_t *attrp, char *const argv[],
+	     char *const envp[])
+{
+	const char *path = getenv("PATH");
+
+	if (!path)
+		path = ":/bin:/usr/bin";
+
+	return __spawni(pid, file, fa, attrp, argv, envp, path);
+}