[v3,2/2] posix: Use posix_spawn on system
Commit Message
This patch uses posix_spawn on system implementation. On Linux this has
the advantage of much lower memory consumption (usually 32 Kb minimum for
the mmap stack area).
Although POSIX does not require, glibc system implementation aims to be
thread and cancellation safe. The cancellation code is moved to generic
implementation and enabled iff SIGCANCEL is defined (similar on how the
cancellation handler is enabled on nptl-init.c).
The _LIBC_REENTRANT related code is removed and the signal handler reset
when cancellation happens is handled all by the cleanup handler (system
is already a AS-unsafe function).
Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
arm-linux-gnueabihf, and powerpc64le-linux-gnu.
* sysdeps/unix/sysv/linux/spawni.c (__spawni_child): Use
__sigismember instead of sigismember.
* sysdeps/posix/system.c [SIGCANCEL] (cancel_handler_args,
cancel_handler): New definitions.
(CLEANUP_HANDLER, CLEANUP_RESET): Likewise.
(DO_LOCK, DO_UNLOCK, INIT_LOCK, ADD_REF, SUB_REF): Remove.
(do_system): Use posix_spawn instead of fork and execl and remove
reentracy code.
* sysdeps/generic/not-errno.h (__kill_noerrno): New prototype.
* sysdeps/unix/sysv/linux/not-errno.h (__kill_noerrno): Likewise.
* sysdeps/unix/sysv/linux/ia64/system.c: Remove file.
* sysdeps/unix/sysv/linux/s390/system.c: Likewise.
* sysdeps/unix/sysv/linux/sparc/system.c: Likewise.
* sysdeps/unix/sysv/linux/system.c: Likewise.
---
ChangeLog | 15 ++
sysdeps/generic/not-errno.h | 2 +
sysdeps/posix/system.c | 201 +++++++++++--------------
sysdeps/unix/sysv/linux/ia64/system.c | 30 ----
sysdeps/unix/sysv/linux/not-errno.h | 14 ++
sysdeps/unix/sysv/linux/s390/system.c | 29 ----
sysdeps/unix/sysv/linux/sparc/system.c | 29 ----
sysdeps/unix/sysv/linux/spawni.c | 4 +-
sysdeps/unix/sysv/linux/system.c | 76 ----------
9 files changed, 119 insertions(+), 281 deletions(-)
delete mode 100644 sysdeps/unix/sysv/linux/ia64/system.c
delete mode 100644 sysdeps/unix/sysv/linux/s390/system.c
delete mode 100644 sysdeps/unix/sysv/linux/sparc/system.c
delete mode 100644 sysdeps/unix/sysv/linux/system.c
Comments
Ping.
On 25/10/2018 14:41, Adhemerval Zanella wrote:
> This patch uses posix_spawn on system implementation. On Linux this has
> the advantage of much lower memory consumption (usually 32 Kb minimum for
> the mmap stack area).
>
> Although POSIX does not require, glibc system implementation aims to be
> thread and cancellation safe. The cancellation code is moved to generic
> implementation and enabled iff SIGCANCEL is defined (similar on how the
> cancellation handler is enabled on nptl-init.c).
>
> The _LIBC_REENTRANT related code is removed and the signal handler reset
> when cancellation happens is handled all by the cleanup handler (system
> is already a AS-unsafe function).
>
> Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
> arm-linux-gnueabihf, and powerpc64le-linux-gnu.
>
> * sysdeps/unix/sysv/linux/spawni.c (__spawni_child): Use
> __sigismember instead of sigismember.
> * sysdeps/posix/system.c [SIGCANCEL] (cancel_handler_args,
> cancel_handler): New definitions.
> (CLEANUP_HANDLER, CLEANUP_RESET): Likewise.
> (DO_LOCK, DO_UNLOCK, INIT_LOCK, ADD_REF, SUB_REF): Remove.
> (do_system): Use posix_spawn instead of fork and execl and remove
> reentracy code.
> * sysdeps/generic/not-errno.h (__kill_noerrno): New prototype.
> * sysdeps/unix/sysv/linux/not-errno.h (__kill_noerrno): Likewise.
> * sysdeps/unix/sysv/linux/ia64/system.c: Remove file.
> * sysdeps/unix/sysv/linux/s390/system.c: Likewise.
> * sysdeps/unix/sysv/linux/sparc/system.c: Likewise.
> * sysdeps/unix/sysv/linux/system.c: Likewise.
> ---
> ChangeLog | 15 ++
> sysdeps/generic/not-errno.h | 2 +
> sysdeps/posix/system.c | 201 +++++++++++--------------
> sysdeps/unix/sysv/linux/ia64/system.c | 30 ----
> sysdeps/unix/sysv/linux/not-errno.h | 14 ++
> sysdeps/unix/sysv/linux/s390/system.c | 29 ----
> sysdeps/unix/sysv/linux/sparc/system.c | 29 ----
> sysdeps/unix/sysv/linux/spawni.c | 4 +-
> sysdeps/unix/sysv/linux/system.c | 76 ----------
> 9 files changed, 119 insertions(+), 281 deletions(-)
> delete mode 100644 sysdeps/unix/sysv/linux/ia64/system.c
> delete mode 100644 sysdeps/unix/sysv/linux/s390/system.c
> delete mode 100644 sysdeps/unix/sysv/linux/sparc/system.c
> delete mode 100644 sysdeps/unix/sysv/linux/system.c
>
> diff --git a/sysdeps/generic/not-errno.h b/sysdeps/generic/not-errno.h
> index 93617a3266..0fd66b5c5e 100644
> --- a/sysdeps/generic/not-errno.h
> +++ b/sysdeps/generic/not-errno.h
> @@ -17,3 +17,5 @@
> <http://www.gnu.org/licenses/>. */
>
> extern __typeof (__access) __access_noerrno attribute_hidden;
> +
> +extern __typeof (__kill) __kill_noerrno attribute_hidden;
> diff --git a/sysdeps/posix/system.c b/sysdeps/posix/system.c
> index d7594436ed..c762f15995 100644
> --- a/sysdeps/posix/system.c
> +++ b/sysdeps/posix/system.c
> @@ -17,36 +17,63 @@
>
> #include <errno.h>
> #include <signal.h>
> -#include <stddef.h>
> #include <stdlib.h>
> #include <unistd.h>
> +#include <sigsetops.h>
> +#include <spawn.h>
> +#include <pthread.h>
> #include <sys/types.h>
> #include <sys/wait.h>
> -#include <libc-lock.h>
> -#include <sysdep-cancel.h>
> -#include <sigsetops.h>
> +#include <stdio.h>
>
> +#include <libc-lock.h>
> +#include <not-errno.h>
> +#include <internal-signals.h>
>
> #define SHELL_PATH "/bin/sh" /* Path of the shell. */
> #define SHELL_NAME "sh" /* Name to give it. */
>
> +/* We have to and actually can handle cancelable system(). The big
> + problem: we have to kill the child process if necessary. To do
> + this a cleanup handler has to be registered and it has to be able
> + to find the PID of the child. The main problem is to reliable have
> + the PID when needed. It is not necessary for the parent thread to
> + return. It might still be in the kernel when the cancellation
> + request comes. Therefore we have to use the clone() calls ability
> + to have the kernel write the PID into the user-level variable. */
>
> -#ifdef _LIBC_REENTRANT
> -static struct sigaction intr, quit;
> -static int sa_refcntr;
> -__libc_lock_define_initialized (static, lock);
> +#ifdef SIGCANCEL
> +
> +struct cancel_handler_args
> +{
> + struct sigaction *quit;
> + struct sigaction *intr;
> + pid_t pid;
> +};
> +
> +static void
> +cancel_handler (void *arg)
> +{
> + struct cancel_handler_args *args = (struct cancel_handler_args *) (arg);
>
> -# define DO_LOCK() __libc_lock_lock (lock)
> -# define DO_UNLOCK() __libc_lock_unlock (lock)
> -# define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
> -# define ADD_REF() sa_refcntr++
> -# define SUB_REF() --sa_refcntr
> + __kill_noerrno (args->pid, SIGKILL);
> +
> + TEMP_FAILURE_RETRY (__waitpid (args->pid, NULL, 0));
> +
> + __sigaction (SIGQUIT, args->quit, NULL);
> + __sigaction (SIGINT, args->intr, NULL);
> +}
> +# define CLEANUP_HANDLER(q, i, p) \
> + __libc_cleanup_region_start (1, cancel_handler, \
> + &((struct cancel_handler_args) { \
> + .quit = &(q), \
> + .intr = &(i), \
> + .pid = (p) }))
> +# define CLEANUP_RESET() \
> + __libc_cleanup_region_end (0)
> #else
> -# define DO_LOCK()
> -# define DO_UNLOCK()
> -# define INIT_LOCK()
> -# define ADD_REF() 0
> -# define SUB_REF() 0
> +# define CLEANUP_HANDLER(q, i, p)
> +# define CLEANUP_RESET()
> #endif
>
>
> @@ -54,122 +81,66 @@ __libc_lock_define_initialized (static, lock);
> static int
> do_system (const char *line)
> {
> - int status, save;
> + int status;
> pid_t pid;
> struct sigaction sa;
> -#ifndef _LIBC_REENTRANT
> struct sigaction intr, quit;
> -#endif
> sigset_t omask;
> + sigset_t reset;
>
> sa.sa_handler = SIG_IGN;
> sa.sa_flags = 0;
> __sigemptyset (&sa.sa_mask);
>
> - DO_LOCK ();
> - if (ADD_REF () == 0)
> - {
> - if (__sigaction (SIGINT, &sa, &intr) < 0)
> - {
> - (void) SUB_REF ();
> - goto out;
> - }
> - if (__sigaction (SIGQUIT, &sa, &quit) < 0)
> - {
> - save = errno;
> - (void) SUB_REF ();
> - goto out_restore_sigint;
> - }
> - }
> - DO_UNLOCK ();
> + /* sigaction can not fail with SIGINT/SIGQUIT used with SIG_IGN. */
> + __sigaction (SIGINT, &sa, &intr);
> + __sigaction (SIGQUIT, &sa, &quit);
>
> - /* We reuse the bitmap in the 'sa' structure. */
> __sigaddset (&sa.sa_mask, SIGCHLD);
> - save = errno;
> - if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
> - {
> -#ifndef _LIBC
> - if (errno == ENOSYS)
> - __set_errno (save);
> - else
> -#endif
> - {
> - DO_LOCK ();
> - if (SUB_REF () == 0)
> - {
> - save = errno;
> - (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
> - out_restore_sigint:
> - (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
> - __set_errno (save);
> - }
> - out:
> - DO_UNLOCK ();
> - return -1;
> - }
> - }
> -
> -#ifdef CLEANUP_HANDLER
> - CLEANUP_HANDLER;
> -#endif
> -
> -#ifdef FORK
> - pid = FORK ();
> -#else
> - pid = __fork ();
> -#endif
> - if (pid == (pid_t) 0)
> - {
> - /* Child side. */
> - const char *new_argv[4];
> - new_argv[0] = SHELL_NAME;
> - new_argv[1] = "-c";
> - new_argv[2] = line;
> - new_argv[3] = NULL;
> -
> - /* Restore the signals. */
> - (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
> - (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
> - (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
> - INIT_LOCK ();
> -
> - /* Exec the shell. */
> - (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
> - _exit (127);
> - }
> - else if (pid < (pid_t) 0)
> - /* The fork failed. */
> - status = -1;
> - else
> - /* Parent side. */
> + /* sigprocmask can not fail with SIG_BLOCK used with valid input
> + arguments. */
> + __sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask);
> +
> + __sigemptyset (&reset);
> + if (intr.sa_handler != SIG_IGN)
> + __sigaddset(&reset, SIGINT);
> + if (quit.sa_handler != SIG_IGN)
> + __sigaddset(&reset, SIGQUIT);
> +
> + posix_spawnattr_t spawn_attr;
> + /* None of the posix_spawnattr_* function returns an error, including
> + posix_spawnattr_setflags for the follow specific usage (using valid
> + flags). */
> + __posix_spawnattr_init (&spawn_attr);
> + __posix_spawnattr_setsigmask (&spawn_attr, &omask);
> + __posix_spawnattr_setsigdefault (&spawn_attr, &reset);
> + __posix_spawnattr_setflags (&spawn_attr,
> + POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK);
> +
> + status = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr,
> + (char *const[]){ (char*) SHELL_NAME,
> + (char*) "-c",
> + (char *) line, NULL },
> + __environ);
> + __posix_spawnattr_destroy (&spawn_attr);
> +
> + if (status == 0)
> {
> + /* Cancellation results in cleanup handlers running as exceptions in
> + the block where they were installed, so it is safe to reference
> + stack variable allocate in the broader scope. */
> + CLEANUP_HANDLER (quit, intr, pid);
> /* Note the system() is a cancellation point. But since we call
> waitpid() which itself is a cancellation point we do not
> have to do anything here. */
> if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
> status = -1;
> + CLEANUP_RESET ();
> }
>
> -#ifdef CLEANUP_HANDLER
> - CLEANUP_RESET;
> -#endif
> -
> - save = errno;
> - DO_LOCK ();
> - if ((SUB_REF () == 0
> - && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL)
> - | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
> - || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
> - {
> -#ifndef _LIBC
> - /* glibc cannot be used on systems without waitpid. */
> - if (errno == ENOSYS)
> - __set_errno (save);
> - else
> -#endif
> - status = -1;
> - }
> - DO_UNLOCK ();
> + __sigaction (SIGINT, &intr, NULL);
> + __sigaction (SIGQUIT, &quit, NULL);
> + __sigprocmask (SIG_SETMASK, &omask, NULL);
>
> return status;
> }
> diff --git a/sysdeps/unix/sysv/linux/ia64/system.c b/sysdeps/unix/sysv/linux/ia64/system.c
> deleted file mode 100644
> index d09fefefe6..0000000000
> --- a/sysdeps/unix/sysv/linux/ia64/system.c
> +++ /dev/null
> @@ -1,30 +0,0 @@
> -/* Copyright (C) 2002-2018 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/>. */
> -
> -/* We have to and actually can handle cancelable system(). The big
> - problem: we have to kill the child process if necessary. To do
> - this a cleanup handler has to be registered and is has to be able
> - to find the PID of the child. The main problem is to reliable have
> - the PID when needed. It is not necessary for the parent thread to
> - return. It might still be in the kernel when the cancellation
> - request comes. Therefore we have to use the clone() calls ability
> - to have the kernel write the PID into the user-level variable. */
> -#define FORK() \
> - INLINE_SYSCALL (clone2, 6, CLONE_PARENT_SETTID | SIGCHLD, NULL, 0, \
> - &pid, NULL, NULL)
> -
> -#include <sysdeps/unix/sysv/linux/system.c>
> diff --git a/sysdeps/unix/sysv/linux/not-errno.h b/sysdeps/unix/sysv/linux/not-errno.h
> index 106ba5c72e..b2f72cfb3d 100644
> --- a/sysdeps/unix/sysv/linux/not-errno.h
> +++ b/sysdeps/unix/sysv/linux/not-errno.h
> @@ -16,6 +16,9 @@
> License along with the GNU C Library; if not, see
> <http://www.gnu.org/licenses/>. */
>
> +#include <sysdep.h>
> +#include <fcntl.h>
> +
> /* This function is used on maybe_enable_malloc_check (elf/dl-tunables.c)
> and to avoid having to build/use multiple versions if stack protection
> in enabled it is defined as inline. */
> @@ -33,3 +36,14 @@ __access_noerrno (const char *pathname, int mode)
> return INTERNAL_SYSCALL_ERRNO (res, err);
> return 0;
> }
> +
> +static inline int
> +__kill_noerrno (pid_t pid, int sig)
> +{
> + int res;
> + INTERNAL_SYSCALL_DECL (err);
> + res = INTERNAL_SYSCALL_CALL (kill, err, pid, sig);
> + if (INTERNAL_SYSCALL_ERROR_P (res, err))
> + return INTERNAL_SYSCALL_ERRNO (res, err);
> + return 0;
> +}
> diff --git a/sysdeps/unix/sysv/linux/s390/system.c b/sysdeps/unix/sysv/linux/s390/system.c
> deleted file mode 100644
> index d8ef461334..0000000000
> --- a/sysdeps/unix/sysv/linux/s390/system.c
> +++ /dev/null
> @@ -1,29 +0,0 @@
> -/* Copyright (C) 2003-2018 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/>. */
> -
> -/* We have to and actually can handle cancelable system(). The big
> - problem: we have to kill the child process if necessary. To do
> - this a cleanup handler has to be registered and is has to be able
> - to find the PID of the child. The main problem is to reliable have
> - the PID when needed. It is not necessary for the parent thread to
> - return. It might still be in the kernel when the cancellation
> - request comes. Therefore we have to use the clone() calls ability
> - to have the kernel write the PID into the user-level variable. */
> -#define FORK() \
> - INLINE_SYSCALL (clone, 3, 0, CLONE_PARENT_SETTID | SIGCHLD, &pid)
> -
> -#include "../system.c"
> diff --git a/sysdeps/unix/sysv/linux/sparc/system.c b/sysdeps/unix/sysv/linux/sparc/system.c
> deleted file mode 100644
> index 1f65c83399..0000000000
> --- a/sysdeps/unix/sysv/linux/sparc/system.c
> +++ /dev/null
> @@ -1,29 +0,0 @@
> -/* Copyright (C) 2003-2018 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/>. */
> -
> -/* We have to and actually can handle cancelable system(). The big
> - problem: we have to kill the child process if necessary. To do
> - this a cleanup handler has to be registered and is has to be able
> - to find the PID of the child. The main problem is to reliable have
> - the PID when needed. It is not necessary for the parent thread to
> - return. It might still be in the kernel when the cancellation
> - request comes. Therefore we have to use the clone() calls ability
> - to have the kernel write the PID into the user-level variable. */
> -#define FORK() \
> - INLINE_CLONE_SYSCALL (CLONE_PARENT_SETTID | SIGCHLD, 0, &pid, NULL, NULL)
> -
> -#include "../system.c"
> diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
> index 85239cedbf..6a8bd2ed2e 100644
> --- a/sysdeps/unix/sysv/linux/spawni.c
> +++ b/sysdeps/unix/sysv/linux/spawni.c
> @@ -138,11 +138,11 @@ __spawni_child (void *arguments)
> for (int sig = 1; sig < _NSIG; ++sig)
> {
> if ((attr->__flags & POSIX_SPAWN_SETSIGDEF)
> - && sigismember (&attr->__sd, sig))
> + && __sigismember (&attr->__sd, sig))
> {
> sa.sa_handler = SIG_DFL;
> }
> - else if (sigismember (&hset, sig))
> + else if (__sigismember (&hset, sig))
> {
> if (__is_internal_signal (sig))
> sa.sa_handler = SIG_IGN;
> diff --git a/sysdeps/unix/sysv/linux/system.c b/sysdeps/unix/sysv/linux/system.c
> deleted file mode 100644
> index 7cc68a1528..0000000000
> --- a/sysdeps/unix/sysv/linux/system.c
> +++ /dev/null
> @@ -1,76 +0,0 @@
> -/* Copyright (C) 2002-2018 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 <sched.h>
> -#include <signal.h>
> -#include <string.h> /* For the real memset prototype. */
> -#include <sysdep.h>
> -#include <unistd.h>
> -#include <sys/wait.h>
> -#include <libc-lock.h>
> -
> -/* We have to and actually can handle cancelable system(). The big
> - problem: we have to kill the child process if necessary. To do
> - this a cleanup handler has to be registered and is has to be able
> - to find the PID of the child. The main problem is to reliable have
> - the PID when needed. It is not necessary for the parent thread to
> - return. It might still be in the kernel when the cancellation
> - request comes. Therefore we have to use the clone() calls ability
> - to have the kernel write the PID into the user-level variable. */
> -#ifndef FORK
> -# define FORK() \
> - INLINE_SYSCALL (clone, 3, CLONE_PARENT_SETTID | SIGCHLD, 0, &pid)
> -#endif
> -
> -#ifdef _LIBC_REENTRANT
> -static void cancel_handler (void *arg);
> -
> -# define CLEANUP_HANDLER \
> - __libc_cleanup_region_start (1, cancel_handler, &pid)
> -
> -# define CLEANUP_RESET \
> - __libc_cleanup_region_end (0)
> -#endif
> -
> -
> -/* Linux has waitpid(), so override the generic unix version. */
> -#include <sysdeps/posix/system.c>
> -
> -
> -#ifdef _LIBC_REENTRANT
> -/* The cancellation handler. */
> -static void
> -cancel_handler (void *arg)
> -{
> - pid_t child = *(pid_t *) arg;
> -
> - INTERNAL_SYSCALL_DECL (err);
> - INTERNAL_SYSCALL (kill, err, 2, child, SIGKILL);
> -
> - TEMP_FAILURE_RETRY (__waitpid (child, NULL, 0));
> -
> - DO_LOCK ();
> -
> - if (SUB_REF () == 0)
> - {
> - (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
> - (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
> - }
> -
> - DO_UNLOCK ();
> -}
> -#endif
>
* Adhemerval Zanella:
> +/* We have to and actually can handle cancelable system(). The big
> + problem: we have to kill the child process if necessary. To do
> + this a cleanup handler has to be registered and it has to be able
> + to find the PID of the child. The main problem is to reliable have
> + the PID when needed. It is not necessary for the parent thread to
> + return. It might still be in the kernel when the cancellation
> + request comes. Therefore we have to use the clone() calls ability
> + to have the kernel write the PID into the user-level variable. */
This comment does not look relevant to me anymore.
> -#ifdef _LIBC_REENTRANT
> -static struct sigaction intr, quit;
> -static int sa_refcntr;
> -__libc_lock_define_initialized (static, lock);
> +#ifdef SIGCANCEL
> +
> +struct cancel_handler_args
> +{
> + struct sigaction *quit;
> + struct sigaction *intr;
> + pid_t pid;
Trailing whitespace on the last line.
> +# define CLEANUP_HANDLER(q, i, p) \
> + __libc_cleanup_region_start (1, cancel_handler, \
> + &((struct cancel_handler_args) { \
> + .quit = &(q), \
> + .intr = &(i), \
> + .pid = (p) }))
> +# define CLEANUP_RESET() \
> + __libc_cleanup_region_end (0)
I don't see the value in those macros, they just hide what is going on.
You should also use a named local variable instead of the compound
literal. I think it is acceptable to duplicate the actual __waitpid
call for the cancellation and non-cancellation cases.
Rest looks okay to me.
I think we should seriously consider not messing with signals if
__libc_multiple_threads, but that is a separate change.
Thanks,
Florian
@@ -17,3 +17,5 @@
<http://www.gnu.org/licenses/>. */
extern __typeof (__access) __access_noerrno attribute_hidden;
+
+extern __typeof (__kill) __kill_noerrno attribute_hidden;
@@ -17,36 +17,63 @@
#include <errno.h>
#include <signal.h>
-#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
+#include <sigsetops.h>
+#include <spawn.h>
+#include <pthread.h>
#include <sys/types.h>
#include <sys/wait.h>
-#include <libc-lock.h>
-#include <sysdep-cancel.h>
-#include <sigsetops.h>
+#include <stdio.h>
+#include <libc-lock.h>
+#include <not-errno.h>
+#include <internal-signals.h>
#define SHELL_PATH "/bin/sh" /* Path of the shell. */
#define SHELL_NAME "sh" /* Name to give it. */
+/* We have to and actually can handle cancelable system(). The big
+ problem: we have to kill the child process if necessary. To do
+ this a cleanup handler has to be registered and it has to be able
+ to find the PID of the child. The main problem is to reliable have
+ the PID when needed. It is not necessary for the parent thread to
+ return. It might still be in the kernel when the cancellation
+ request comes. Therefore we have to use the clone() calls ability
+ to have the kernel write the PID into the user-level variable. */
-#ifdef _LIBC_REENTRANT
-static struct sigaction intr, quit;
-static int sa_refcntr;
-__libc_lock_define_initialized (static, lock);
+#ifdef SIGCANCEL
+
+struct cancel_handler_args
+{
+ struct sigaction *quit;
+ struct sigaction *intr;
+ pid_t pid;
+};
+
+static void
+cancel_handler (void *arg)
+{
+ struct cancel_handler_args *args = (struct cancel_handler_args *) (arg);
-# define DO_LOCK() __libc_lock_lock (lock)
-# define DO_UNLOCK() __libc_lock_unlock (lock)
-# define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
-# define ADD_REF() sa_refcntr++
-# define SUB_REF() --sa_refcntr
+ __kill_noerrno (args->pid, SIGKILL);
+
+ TEMP_FAILURE_RETRY (__waitpid (args->pid, NULL, 0));
+
+ __sigaction (SIGQUIT, args->quit, NULL);
+ __sigaction (SIGINT, args->intr, NULL);
+}
+# define CLEANUP_HANDLER(q, i, p) \
+ __libc_cleanup_region_start (1, cancel_handler, \
+ &((struct cancel_handler_args) { \
+ .quit = &(q), \
+ .intr = &(i), \
+ .pid = (p) }))
+# define CLEANUP_RESET() \
+ __libc_cleanup_region_end (0)
#else
-# define DO_LOCK()
-# define DO_UNLOCK()
-# define INIT_LOCK()
-# define ADD_REF() 0
-# define SUB_REF() 0
+# define CLEANUP_HANDLER(q, i, p)
+# define CLEANUP_RESET()
#endif
@@ -54,122 +81,66 @@ __libc_lock_define_initialized (static, lock);
static int
do_system (const char *line)
{
- int status, save;
+ int status;
pid_t pid;
struct sigaction sa;
-#ifndef _LIBC_REENTRANT
struct sigaction intr, quit;
-#endif
sigset_t omask;
+ sigset_t reset;
sa.sa_handler = SIG_IGN;
sa.sa_flags = 0;
__sigemptyset (&sa.sa_mask);
- DO_LOCK ();
- if (ADD_REF () == 0)
- {
- if (__sigaction (SIGINT, &sa, &intr) < 0)
- {
- (void) SUB_REF ();
- goto out;
- }
- if (__sigaction (SIGQUIT, &sa, &quit) < 0)
- {
- save = errno;
- (void) SUB_REF ();
- goto out_restore_sigint;
- }
- }
- DO_UNLOCK ();
+ /* sigaction can not fail with SIGINT/SIGQUIT used with SIG_IGN. */
+ __sigaction (SIGINT, &sa, &intr);
+ __sigaction (SIGQUIT, &sa, &quit);
- /* We reuse the bitmap in the 'sa' structure. */
__sigaddset (&sa.sa_mask, SIGCHLD);
- save = errno;
- if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
- {
-#ifndef _LIBC
- if (errno == ENOSYS)
- __set_errno (save);
- else
-#endif
- {
- DO_LOCK ();
- if (SUB_REF () == 0)
- {
- save = errno;
- (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
- out_restore_sigint:
- (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
- __set_errno (save);
- }
- out:
- DO_UNLOCK ();
- return -1;
- }
- }
-
-#ifdef CLEANUP_HANDLER
- CLEANUP_HANDLER;
-#endif
-
-#ifdef FORK
- pid = FORK ();
-#else
- pid = __fork ();
-#endif
- if (pid == (pid_t) 0)
- {
- /* Child side. */
- const char *new_argv[4];
- new_argv[0] = SHELL_NAME;
- new_argv[1] = "-c";
- new_argv[2] = line;
- new_argv[3] = NULL;
-
- /* Restore the signals. */
- (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
- (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
- (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
- INIT_LOCK ();
-
- /* Exec the shell. */
- (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
- _exit (127);
- }
- else if (pid < (pid_t) 0)
- /* The fork failed. */
- status = -1;
- else
- /* Parent side. */
+ /* sigprocmask can not fail with SIG_BLOCK used with valid input
+ arguments. */
+ __sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask);
+
+ __sigemptyset (&reset);
+ if (intr.sa_handler != SIG_IGN)
+ __sigaddset(&reset, SIGINT);
+ if (quit.sa_handler != SIG_IGN)
+ __sigaddset(&reset, SIGQUIT);
+
+ posix_spawnattr_t spawn_attr;
+ /* None of the posix_spawnattr_* function returns an error, including
+ posix_spawnattr_setflags for the follow specific usage (using valid
+ flags). */
+ __posix_spawnattr_init (&spawn_attr);
+ __posix_spawnattr_setsigmask (&spawn_attr, &omask);
+ __posix_spawnattr_setsigdefault (&spawn_attr, &reset);
+ __posix_spawnattr_setflags (&spawn_attr,
+ POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK);
+
+ status = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr,
+ (char *const[]){ (char*) SHELL_NAME,
+ (char*) "-c",
+ (char *) line, NULL },
+ __environ);
+ __posix_spawnattr_destroy (&spawn_attr);
+
+ if (status == 0)
{
+ /* Cancellation results in cleanup handlers running as exceptions in
+ the block where they were installed, so it is safe to reference
+ stack variable allocate in the broader scope. */
+ CLEANUP_HANDLER (quit, intr, pid);
/* Note the system() is a cancellation point. But since we call
waitpid() which itself is a cancellation point we do not
have to do anything here. */
if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
status = -1;
+ CLEANUP_RESET ();
}
-#ifdef CLEANUP_HANDLER
- CLEANUP_RESET;
-#endif
-
- save = errno;
- DO_LOCK ();
- if ((SUB_REF () == 0
- && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL)
- | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
- || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
- {
-#ifndef _LIBC
- /* glibc cannot be used on systems without waitpid. */
- if (errno == ENOSYS)
- __set_errno (save);
- else
-#endif
- status = -1;
- }
- DO_UNLOCK ();
+ __sigaction (SIGINT, &intr, NULL);
+ __sigaction (SIGQUIT, &quit, NULL);
+ __sigprocmask (SIG_SETMASK, &omask, NULL);
return status;
}
deleted file mode 100644
@@ -1,30 +0,0 @@
-/* Copyright (C) 2002-2018 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/>. */
-
-/* We have to and actually can handle cancelable system(). The big
- problem: we have to kill the child process if necessary. To do
- this a cleanup handler has to be registered and is has to be able
- to find the PID of the child. The main problem is to reliable have
- the PID when needed. It is not necessary for the parent thread to
- return. It might still be in the kernel when the cancellation
- request comes. Therefore we have to use the clone() calls ability
- to have the kernel write the PID into the user-level variable. */
-#define FORK() \
- INLINE_SYSCALL (clone2, 6, CLONE_PARENT_SETTID | SIGCHLD, NULL, 0, \
- &pid, NULL, NULL)
-
-#include <sysdeps/unix/sysv/linux/system.c>
@@ -16,6 +16,9 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+#include <sysdep.h>
+#include <fcntl.h>
+
/* This function is used on maybe_enable_malloc_check (elf/dl-tunables.c)
and to avoid having to build/use multiple versions if stack protection
in enabled it is defined as inline. */
@@ -33,3 +36,14 @@ __access_noerrno (const char *pathname, int mode)
return INTERNAL_SYSCALL_ERRNO (res, err);
return 0;
}
+
+static inline int
+__kill_noerrno (pid_t pid, int sig)
+{
+ int res;
+ INTERNAL_SYSCALL_DECL (err);
+ res = INTERNAL_SYSCALL_CALL (kill, err, pid, sig);
+ if (INTERNAL_SYSCALL_ERROR_P (res, err))
+ return INTERNAL_SYSCALL_ERRNO (res, err);
+ return 0;
+}
deleted file mode 100644
@@ -1,29 +0,0 @@
-/* Copyright (C) 2003-2018 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/>. */
-
-/* We have to and actually can handle cancelable system(). The big
- problem: we have to kill the child process if necessary. To do
- this a cleanup handler has to be registered and is has to be able
- to find the PID of the child. The main problem is to reliable have
- the PID when needed. It is not necessary for the parent thread to
- return. It might still be in the kernel when the cancellation
- request comes. Therefore we have to use the clone() calls ability
- to have the kernel write the PID into the user-level variable. */
-#define FORK() \
- INLINE_SYSCALL (clone, 3, 0, CLONE_PARENT_SETTID | SIGCHLD, &pid)
-
-#include "../system.c"
deleted file mode 100644
@@ -1,29 +0,0 @@
-/* Copyright (C) 2003-2018 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/>. */
-
-/* We have to and actually can handle cancelable system(). The big
- problem: we have to kill the child process if necessary. To do
- this a cleanup handler has to be registered and is has to be able
- to find the PID of the child. The main problem is to reliable have
- the PID when needed. It is not necessary for the parent thread to
- return. It might still be in the kernel when the cancellation
- request comes. Therefore we have to use the clone() calls ability
- to have the kernel write the PID into the user-level variable. */
-#define FORK() \
- INLINE_CLONE_SYSCALL (CLONE_PARENT_SETTID | SIGCHLD, 0, &pid, NULL, NULL)
-
-#include "../system.c"
@@ -138,11 +138,11 @@ __spawni_child (void *arguments)
for (int sig = 1; sig < _NSIG; ++sig)
{
if ((attr->__flags & POSIX_SPAWN_SETSIGDEF)
- && sigismember (&attr->__sd, sig))
+ && __sigismember (&attr->__sd, sig))
{
sa.sa_handler = SIG_DFL;
}
- else if (sigismember (&hset, sig))
+ else if (__sigismember (&hset, sig))
{
if (__is_internal_signal (sig))
sa.sa_handler = SIG_IGN;
deleted file mode 100644
@@ -1,76 +0,0 @@
-/* Copyright (C) 2002-2018 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 <sched.h>
-#include <signal.h>
-#include <string.h> /* For the real memset prototype. */
-#include <sysdep.h>
-#include <unistd.h>
-#include <sys/wait.h>
-#include <libc-lock.h>
-
-/* We have to and actually can handle cancelable system(). The big
- problem: we have to kill the child process if necessary. To do
- this a cleanup handler has to be registered and is has to be able
- to find the PID of the child. The main problem is to reliable have
- the PID when needed. It is not necessary for the parent thread to
- return. It might still be in the kernel when the cancellation
- request comes. Therefore we have to use the clone() calls ability
- to have the kernel write the PID into the user-level variable. */
-#ifndef FORK
-# define FORK() \
- INLINE_SYSCALL (clone, 3, CLONE_PARENT_SETTID | SIGCHLD, 0, &pid)
-#endif
-
-#ifdef _LIBC_REENTRANT
-static void cancel_handler (void *arg);
-
-# define CLEANUP_HANDLER \
- __libc_cleanup_region_start (1, cancel_handler, &pid)
-
-# define CLEANUP_RESET \
- __libc_cleanup_region_end (0)
-#endif
-
-
-/* Linux has waitpid(), so override the generic unix version. */
-#include <sysdeps/posix/system.c>
-
-
-#ifdef _LIBC_REENTRANT
-/* The cancellation handler. */
-static void
-cancel_handler (void *arg)
-{
- pid_t child = *(pid_t *) arg;
-
- INTERNAL_SYSCALL_DECL (err);
- INTERNAL_SYSCALL (kill, err, 2, child, SIGKILL);
-
- TEMP_FAILURE_RETRY (__waitpid (child, NULL, 0));
-
- DO_LOCK ();
-
- if (SUB_REF () == 0)
- {
- (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
- (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
- }
-
- DO_UNLOCK ();
-}
-#endif