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93d78ec1cb
No new symbol version is required because there was a forwarder. The symbol has been moved using scripts/move-symbol-to-libc.py. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
210 lines
5.9 KiB
C
210 lines
5.9 KiB
C
/* Copyright (C) 1991-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sigsetops.h>
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#include <spawn.h>
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#include <pthread.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <stdio.h>
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#include <libc-lock.h>
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#include <not-errno.h>
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#include <not-cancel.h>
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#include <internal-signals.h>
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#define SHELL_PATH "/bin/sh" /* Path of the shell. */
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#define SHELL_NAME "sh" /* Name to give it. */
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/* This system implementation aims to be thread-safe, which requires to
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restore the signal dispositions for SIGINT and SIGQUIT correctly and to
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deal with cancellation by terminating the child process.
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The signal disposition restoration on the single-thread case is
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straighfoward. For multithreaded case, a reference-counter with a lock
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is used, so the first thread will set the SIGINT/SIGQUIT dispositions and
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last thread will restore them.
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Cancellation handling is done with thread cancellation clean-up handlers
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on waitpid call. */
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#ifdef _LIBC_REENTRANT
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static struct sigaction intr, quit;
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static int sa_refcntr;
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__libc_lock_define_initialized (static, lock);
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# define DO_LOCK() __libc_lock_lock (lock)
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# define DO_UNLOCK() __libc_lock_unlock (lock)
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# define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
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# define ADD_REF() sa_refcntr++
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# define SUB_REF() --sa_refcntr
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#else
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# define DO_LOCK()
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# define DO_UNLOCK()
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# define INIT_LOCK()
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# define ADD_REF() 0
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# define SUB_REF() 0
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#endif
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#if defined(_LIBC_REENTRANT) && defined(SIGCANCEL)
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struct cancel_handler_args
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{
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struct sigaction *quit;
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struct sigaction *intr;
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pid_t pid;
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};
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static void
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cancel_handler (void *arg)
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{
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struct cancel_handler_args *args = (struct cancel_handler_args *) (arg);
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__kill_noerrno (args->pid, SIGKILL);
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int state;
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__pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state);
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TEMP_FAILURE_RETRY (__waitpid (args->pid, NULL, 0));
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__pthread_setcancelstate (state, NULL);
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DO_LOCK ();
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if (SUB_REF () == 0)
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{
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__sigaction (SIGQUIT, args->quit, NULL);
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__sigaction (SIGINT, args->intr, NULL);
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}
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DO_UNLOCK ();
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}
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#endif
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/* Execute LINE as a shell command, returning its status. */
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static int
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do_system (const char *line)
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{
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int status = -1;
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int ret;
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pid_t pid;
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struct sigaction sa;
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#ifndef _LIBC_REENTRANT
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struct sigaction intr, quit;
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#endif
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sigset_t omask;
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sigset_t reset;
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sa.sa_handler = SIG_IGN;
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sa.sa_flags = 0;
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__sigemptyset (&sa.sa_mask);
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DO_LOCK ();
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if (ADD_REF () == 0)
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{
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/* sigaction can not fail with SIGINT/SIGQUIT used with SIG_IGN. */
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__sigaction (SIGINT, &sa, &intr);
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__sigaction (SIGQUIT, &sa, &quit);
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}
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DO_UNLOCK ();
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__sigaddset (&sa.sa_mask, SIGCHLD);
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/* sigprocmask can not fail with SIG_BLOCK used with valid input
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arguments. */
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__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask);
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__sigemptyset (&reset);
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if (intr.sa_handler != SIG_IGN)
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__sigaddset(&reset, SIGINT);
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if (quit.sa_handler != SIG_IGN)
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__sigaddset(&reset, SIGQUIT);
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posix_spawnattr_t spawn_attr;
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/* None of the posix_spawnattr_* function returns an error, including
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posix_spawnattr_setflags for the follow specific usage (using valid
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flags). */
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__posix_spawnattr_init (&spawn_attr);
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__posix_spawnattr_setsigmask (&spawn_attr, &omask);
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__posix_spawnattr_setsigdefault (&spawn_attr, &reset);
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__posix_spawnattr_setflags (&spawn_attr,
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POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK);
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ret = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr,
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(char *const[]){ (char *) SHELL_NAME,
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(char *) "-c",
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(char *) line, NULL },
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__environ);
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__posix_spawnattr_destroy (&spawn_attr);
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if (ret == 0)
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{
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/* Cancellation results in cleanup handlers running as exceptions in
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the block where they were installed, so it is safe to reference
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stack variable allocate in the broader scope. */
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#if defined(_LIBC_REENTRANT) && defined(SIGCANCEL)
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struct cancel_handler_args cancel_args =
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{
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.quit = &quit,
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.intr = &intr,
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.pid = pid
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};
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__libc_cleanup_region_start (1, cancel_handler, &cancel_args);
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#endif
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/* Note the system() is a cancellation point. But since we call
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waitpid() which itself is a cancellation point we do not
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have to do anything here. */
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if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
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status = -1;
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#if defined(_LIBC_REENTRANT) && defined(SIGCANCEL)
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__libc_cleanup_region_end (0);
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#endif
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}
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else
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/* POSIX states that failure to execute the shell should return
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as if the shell had terminated using _exit(127). */
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status = W_EXITCODE (127, 0);
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DO_LOCK ();
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if (SUB_REF () == 0)
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{
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/* sigaction can not fail with SIGINT/SIGQUIT used with old
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disposition. Same applies for sigprocmask. */
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__sigaction (SIGINT, &intr, NULL);
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__sigaction (SIGQUIT, &quit, NULL);
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__sigprocmask (SIG_SETMASK, &omask, NULL);
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}
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DO_UNLOCK ();
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if (ret != 0)
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__set_errno (ret);
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return status;
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}
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int
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__libc_system (const char *line)
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{
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if (line == NULL)
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/* Check that we have a command processor available. It might
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not be available after a chroot(), for example. */
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return do_system ("exit 0") == 0;
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return do_system (line);
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}
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weak_alias (__libc_system, system)
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