diff options
Diffstat (limited to 'sysdeps/posix/system.c')
| -rw-r--r-- | sysdeps/posix/system.c | 189 |
1 files changed, 100 insertions, 89 deletions
diff --git a/sysdeps/posix/system.c b/sysdeps/posix/system.c index d7594436ed..8a51a6b991 100644 --- a/sysdeps/posix/system.c +++ b/sysdeps/posix/system.c @@ -17,20 +17,36 @@ #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 <not-cancel.h> +#include <internal-signals.h> #define SHELL_PATH "/bin/sh" /* Path of the shell. */ #define SHELL_NAME "sh" /* Name to give it. */ +/* This system implementation aims to be thread-safe, which requires to + restore the signal dispositions for SIGINT and SIGQUIT correctly and to + deal with cancellation by terminating the child process. + + The signal disposition restoration on the single-thread case is + straighfoward. For multithreaded case, a reference-counter with a lock + is used, so the first thread will set the SIGINT/SIGQUIT dispositions and + last thread will restore them. + + Cancellation handling is done with thread cancellation clean-up handlers + on waitpid call. */ + #ifdef _LIBC_REENTRANT static struct sigaction intr, quit; static int sa_refcntr; @@ -50,17 +66,45 @@ __libc_lock_define_initialized (static, lock); #endif +#if defined(_LIBC_REENTRANT) && defined(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); + + __kill_noerrno (args->pid, SIGKILL); + + TEMP_FAILURE_RETRY (__waitpid_nocancel (args->pid, NULL, 0)); + + DO_LOCK (); + if (SUB_REF () == 0) + { + __sigaction (SIGQUIT, args->quit, NULL); + __sigaction (SIGINT, args->intr, NULL); + } + DO_UNLOCK (); +} +#endif + /* Execute LINE as a shell command, returning its status. */ 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; @@ -69,105 +113,72 @@ do_system (const char *line) 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; - } + /* sigaction can not fail with SIGINT/SIGQUIT used with SIG_IGN. */ + __sigaction (SIGINT, &sa, &intr); + __sigaction (SIGQUIT, &sa, &quit); } DO_UNLOCK (); - /* We reuse the bitmap in the 'sa' structure. */ __sigaddset (&sa.sa_mask, SIGCHLD); - save = errno; - if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0) + /* 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) { -#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 (); + /* 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. */ +#if defined(_LIBC_REENTRANT) && defined(SIGCANCEL) + struct cancel_handler_args cancel_args = + { + .quit = &quit, + .intr = &intr, + .pid = pid + }; + __libc_cleanup_region_start (1, cancel_handler, &cancel_args); #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. */ - { /* 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; - } - -#ifdef CLEANUP_HANDLER - CLEANUP_RESET; +#if defined(_LIBC_REENTRANT) && defined(SIGCANCEL) + __libc_cleanup_region_end (0); #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) + if (SUB_REF () == 0) { -#ifndef _LIBC - /* glibc cannot be used on systems without waitpid. */ - if (errno == ENOSYS) - __set_errno (save); - else -#endif - status = -1; + /* sigaction can not fail with SIGINT/SIGQUIT used with old + disposition. Same applies for sigprocmask. */ + __sigaction (SIGINT, &intr, NULL); + __sigaction (SIGQUIT, &quit, NULL); + __sigprocmask (SIG_SETMASK, &omask, NULL); } DO_UNLOCK (); |