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[PATCH v2] Use execveat syscall in fexecve
- From: Andreas Schwab <schwab at suse dot de>
- To: libc-alpha at sourceware dot org
- Date: Mon, 11 Sep 2017 12:23:09 +0200
- Subject: [PATCH v2] Use execveat syscall in fexecve
- Authentication-results: sourceware.org; auth=none
- References: <mvm8thqdgj1.fsf@suse.de> <87bmmmlpe1.fsf@mid.deneb.enyo.de>
By using execveat we no longer depend on /proc. The execveat syscall was
introduced in 3.19, except for a few late comers.
* sysdeps/unix/sysv/linux/fexecve.c (fexecve) [__NR_execveat]: Try
execveat first.
[!__ASSUME_EXECVEAT]: Fall back to /proc if execveat is
unimplemented.
* sysdeps/unix/sysv/linux/kernel-features.h (__ASSUME_EXECVEAT)
[__LINUX_KERNEL_VERSION >= 0x031300]: Define.
* sysdeps/unix/sysv/linux/alpha/kernel-features.h
(__ASSUME_EXECVEAT) [__LINUX_KERNEL_VERSION < 0x040200]: Undef.
* sysdeps/unix/sysv/linux/hppa/kernel-features.h
(__ASSUME_EXECVEAT) [__LINUX_KERNEL_VERSION < 0x040000]: Undef.
* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
(__ASSUME_EXECVEAT) [__LINUX_KERNEL_VERSION < 0x040000]: Undef.
* posix/Makefile (tests): Add tst-fexecve.
* posix/tst-fexecve.c: New file.
---
posix/Makefile | 2 +-
posix/tst-fexecve.c | 88 ++++++++++++++++++++++
sysdeps/unix/sysv/linux/alpha/kernel-features.h | 5 ++
sysdeps/unix/sysv/linux/fexecve.c | 15 ++++
sysdeps/unix/sysv/linux/hppa/kernel-features.h | 5 ++
sysdeps/unix/sysv/linux/kernel-features.h | 5 ++
.../unix/sysv/linux/microblaze/kernel-features.h | 5 ++
7 files changed, 124 insertions(+), 1 deletion(-)
create mode 100644 posix/tst-fexecve.c
diff --git a/posix/Makefile b/posix/Makefile
index 4021e4f19e..75d905b922 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -94,7 +94,7 @@ tests := test-errno tstgetopt testfnm runtests runptests \
tst-fnmatch4 tst-fnmatch5 \
tst-posix_spawn-fd tst-posix_spawn-setsid \
tst-posix_fadvise tst-posix_fadvise64 \
- tst-sysconf-empty-chroot
+ tst-sysconf-empty-chroot tst-fexecve
tests-internal := bug-regex5 bug-regex20 bug-regex33 \
tst-rfc3484 tst-rfc3484-2 tst-rfc3484-3
xtests := bug-ga2
diff --git a/posix/tst-fexecve.c b/posix/tst-fexecve.c
new file mode 100644
index 0000000000..2409102e21
--- /dev/null
+++ b/posix/tst-fexecve.c
@@ -0,0 +1,88 @@
+/* Copyright (C) 2017 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 <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/wait.h>
+
+#include <support/check.h>
+
+/* Try executing "/bin/sh -c true", using FD opened on /bin/sh. */
+static int
+try_fexecve (int fd)
+{
+ pid_t pid = fork ();
+
+ if (pid == 0)
+ {
+ static const char *const argv[] = {
+ "/bin/sh", "-c", "true", NULL
+ };
+ fexecve (fd, (char *const *) argv, environ);
+ _exit (errno);
+ }
+ if (pid < 0)
+ FAIL_RET ("fork failed: %m");
+
+ pid_t termpid;
+ int status;
+ termpid = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
+ if (termpid == -1)
+ FAIL_RET ("waitpid failed: %m");
+ if (termpid != pid)
+ FAIL_RET ("waitpid returned %ld != %ld",
+ (long int) termpid, (long int) pid);
+ if (!WIFEXITED (status))
+ FAIL_RET ("child hasn't exited normally");
+
+ /* If fexecve is unimplemented mark this test as UNSUPPORTED. */
+ if (WEXITSTATUS (status) == ENOSYS)
+ FAIL_UNSUPPORTED ("fexecve is unimplemented");
+
+ if (WEXITSTATUS (status) != 0)
+ {
+ errno = WEXITSTATUS (status);
+ FAIL_RET ("fexecve failed: %m");
+ }
+ return 0;
+}
+
+static int
+do_test (void)
+{
+ int fd;
+ int ret;
+
+ fd = open ("/bin/sh", O_RDONLY);
+ if (fd < 0)
+ FAIL_UNSUPPORTED ("/bin/sh cannot be opened: %m");
+ ret = try_fexecve (fd);
+ close (fd);
+
+#ifdef O_PATH
+ fd = open ("/bin/sh", O_RDONLY | O_PATH);
+ if (fd < 0)
+ FAIL_UNSUPPORTED ("/bin/sh cannot be opened (O_PATH): %m");
+ ret |= try_fexecve (fd);
+ close (fd);
+#endif
+
+ return ret;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/alpha/kernel-features.h b/sysdeps/unix/sysv/linux/alpha/kernel-features.h
index 53f7611f93..5bc2ddb713 100644
--- a/sysdeps/unix/sysv/linux/alpha/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/alpha/kernel-features.h
@@ -35,4 +35,9 @@
#define __ASSUME_RECV_SYSCALL 1
#define __ASSUME_SEND_SYSCALL 1
+/* Support for the execveat syscall was added in 4.2. */
+#if __LINUX_KERNEL_VERSION < 0x040200
+# undef __ASSUME_EXECVEAT
+#endif
+
#endif /* _KERNEL_FEATURES_H */
diff --git a/sysdeps/unix/sysv/linux/fexecve.c b/sysdeps/unix/sysv/linux/fexecve.c
index 30fa719b56..3bf5de507f 100644
--- a/sysdeps/unix/sysv/linux/fexecve.c
+++ b/sysdeps/unix/sysv/linux/fexecve.c
@@ -19,8 +19,13 @@
#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
+#include <fcntl.h>
#include <sys/stat.h>
+#include <sysdep.h>
+#include <sys/syscall.h>
+#include <kernel-features.h>
+
/* Execute the file FD refers to, overlaying the running program image.
ARGV and ENVP are passed to the new program, as for `execve'. */
@@ -33,6 +38,15 @@ fexecve (int fd, char *const argv[], char *const envp[])
return -1;
}
+#ifdef __NR_execveat
+ INLINE_SYSCALL (execveat, 5, fd, "", argv, envp, AT_EMPTY_PATH);
+# ifndef __ASSUME_EXECVEAT
+ if (errno != ENOSYS)
+ return -1;
+# endif
+#endif
+
+#ifndef __ASSUME_EXECVEAT
/* We use the /proc filesystem to get the information. If it is not
mounted we fail. */
char buf[sizeof "/proc/self/fd/" + sizeof (int) * 3];
@@ -50,6 +64,7 @@ fexecve (int fd, char *const argv[], char *const envp[])
save = ENOSYS;
__set_errno (save);
+#endif
return -1;
}
diff --git a/sysdeps/unix/sysv/linux/hppa/kernel-features.h b/sysdeps/unix/sysv/linux/hppa/kernel-features.h
index 0e73a5c0df..f25a840040 100644
--- a/sysdeps/unix/sysv/linux/hppa/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/hppa/kernel-features.h
@@ -27,3 +27,8 @@
#define __ASSUME_RECV_SYSCALL 1
#define __ASSUME_SEND_SYSCALL 1
+
+/* Support for the execveat syscall was added in 4.0. */
+#if __LINUX_KERNEL_VERSION < 0x040000
+# undef __ASSUME_EXECVEAT
+#endif
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 9495db4fef..2e1fe6597a 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -102,3 +102,8 @@
implementation does not assume the __ASSUME_* and instead use a fallback
implementation based on p{read,write}v and returning an error for
non supported flags. */
+
+/* Support for the execveat syscall was added in 3.19. */
+#if __LINUX_KERNEL_VERSION >= 0x031300
+# define __ASSUME_EXECVEAT 1
+#endif
diff --git a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
index 0257524777..6575df2a95 100644
--- a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
@@ -47,3 +47,8 @@
#if __LINUX_KERNEL_VERSION < 0x030300
# undef __ASSUME_SENDMMSG_SYSCALL
#endif
+
+/* Support for the execveat syscall was added in 4.0. */
+#if __LINUX_KERNEL_VERSION < 0x040000
+# undef __ASSUME_EXECVEAT
+#endif
--
2.14.1
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."