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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2016-01-19 17:33:32 -0200
committerAdhemerval Zanella <adhemerval.zanella@linaro.com>2016-03-07 11:53:47 +0700
commit9ff72da471a509a8c19791efe469f47fa6977410 (patch)
tree8c5f0563c5141f1401c5dd43d4255cde78085194 /posix
parent1eb8930608705702d5746e5491bab4e4429fcb83 (diff)
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posix: New Linux posix_spawn{p} implementation
This patch implements a new posix_spawn{p} implementation for Linux. The main difference is it uses the clone syscall directly with CLONE_VM and CLONE_VFORK flags and a direct allocated stack. The new stack and start function solves most the vfork limitation (possible parent clobber due stack spilling). The remaning issue are related to signal handling: 1. That no signal handlers must run in child context, to avoid corrupt parent's state. 2. Child must synchronize with parent to enforce stack deallocation and to possible return execv issues. The first one is solved by blocking all signals in child, even NPTL-internal ones (SIGCANCEL and SIGSETXID). The second issue is done by a stack allocation in parent and a synchronization with using a pipe or waitpid (in case or error). The pipe has the advantage of allowing the child signal an exec error (checked with new tst-spawn2 test). There is an inherent race condition in pipe2 usage for architectures that do not support the syscall directly. In such cases the a pipe plus fctnl is used instead and it may lead to file descriptor leak in parent (as decribed by fcntl documentation). The child process stack is allocate with a mmap with MAP_STACK flag using default architecture stack size. Although it is slower than use a stack buffer from parent, it allows some slack for the compatibility code to run scripts with no shebang (which may use a buffer with size depending of argument list count). Performance should be similar to the vfork default posix implementation and way faster than fork path (vfork on mostly linux ports are basically clone with CLONE_VM plus CLONE_VFORK). The only difference is the syscalls required for the stack allocation/deallocation. It fixes BZ#10354, BZ#14750, and BZ#18433. Tested on i386, x86_64, powerpc64le, and aarch64. [BZ #14750] [BZ #10354] [BZ #18433] * include/sched.h (__clone): Add hidden prototype. (__clone2): Likewise. * include/unistd.h (__dup): Likewise. * posix/Makefile (tests): Add tst-spawn2. * posix/tst-spawn2.c: New file. * sysdeps/posix/dup.c (__dup): Add hidden definition. * sysdeps/unix/sysv/linux/aarch64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/alpha/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/arm/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/hppa/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/i386/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/ia64/clone2.S (__clone): Likewise. * sysdeps/unix/sysv/linux/m68k/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/microblaze/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/mips/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/nios2/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/s390/s390-32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/s390/s390-64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sh/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sparc/sparc32/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/sparc/sparc64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/tile/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/x86_64/clone.S (__clone): Likewise. * sysdeps/unix/sysv/linux/nptl-signals.h (____nptl_is_internal_signal): New function. * sysdeps/unix/sysv/linux/spawni.c: New file.
Diffstat (limited to 'posix')
-rw-r--r--posix/Makefile2
-rw-r--r--posix/tst-spawn2.c72
2 files changed, 73 insertions, 1 deletions
diff --git a/posix/Makefile b/posix/Makefile
index 7ec110e80c..5b0e298f75 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -94,7 +94,7 @@ tests := tstgetopt testfnm runtests runptests \
xtests := bug-ga2
ifeq (yes,$(build-shared))
test-srcs := globtest
-tests += wordexp-test tst-exec tst-spawn
+tests += wordexp-test tst-exec tst-spawn tst-spawn2
endif
tests-static = tst-exec-static tst-spawn-static
tests += $(tests-static)
diff --git a/posix/tst-spawn2.c b/posix/tst-spawn2.c
new file mode 100644
index 0000000000..149f3d5cfa
--- /dev/null
+++ b/posix/tst-spawn2.c
@@ -0,0 +1,72 @@
+/* Further tests for spawn in case of invalid binary paths.
+ Copyright (C) 2016 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 <spawn.h>
+#include <error.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#include <stdio.h>
+
+int
+posix_spawn_test (void)
+{
+ /* Check if posix_spawn correctly returns an error and an invalid pid
+ by trying to spawn an invalid binary. */
+
+ const char *program = "/path/to/invalid/binary";
+ char * const args[] = { 0 };
+ pid_t pid = -1;
+
+ int ret = posix_spawn (&pid, program, 0, 0, args, environ);
+ if (ret != ENOENT)
+ error (EXIT_FAILURE, errno, "posix_spawn");
+
+ /* POSIX states the value returned on pid variable in case of an error
+ is not specified. GLIBC will update the value iff the child
+ execution is successful. */
+ if (pid != -1)
+ error (EXIT_FAILURE, errno, "posix_spawn returned pid != -1");
+
+ /* Check if no child is actually created. */
+ ret = waitpid (-1, NULL, 0);
+ if (ret != -1 || errno != ECHILD)
+ error (EXIT_FAILURE, errno, "waitpid");
+
+ /* Same as before, but with posix_spawnp. */
+ char *args2[] = { (char*) program, 0 };
+
+ ret = posix_spawnp (&pid, args2[0], 0, 0, args2, environ);
+ if (ret != ENOENT)
+ error (EXIT_FAILURE, errno, "posix_spawnp");
+
+ if (pid != -1)
+ error (EXIT_FAILURE, errno, "posix_spawnp returned pid != -1");
+
+ ret = waitpid (-1, NULL, 0);
+ if (ret != -1 || errno != ECHILD)
+ error (EXIT_FAILURE, errno, "waitpid");
+
+ return 0;
+}
+
+#define TEST_FUNCTION posix_spawn_test ()
+#include "../test-skeleton.c"