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https://github.com/fluencelabs/musl
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76f28cfce5
ideally, system would also be cancellable while running the external command, but I cannot find any way to make that work without either leaking zombie processes or introducing behavior that is far outside what the standard specifies. glibc handles cancellation by killing the child process with SIGKILL, but this could be unsafe in that it could leave the data being manipulated by the command in an inconsistent state.
69 lines
1.5 KiB
C
69 lines
1.5 KiB
C
#include <unistd.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <sys/wait.h>
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#include <errno.h>
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#include "pthread_impl.h"
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#include "libc.h"
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static void dummy_0()
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{
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}
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weak_alias(dummy_0, __acquire_ptc);
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weak_alias(dummy_0, __release_ptc);
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pid_t __vfork(void);
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void __testcancel(void);
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int system(const char *cmd)
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{
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pid_t pid;
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sigset_t old;
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struct sigaction sa = { .sa_handler = SIG_IGN }, oldint, oldquit;
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int status = -1, i;
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__testcancel();
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if (!cmd) return 1;
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sigaction(SIGINT, &sa, &oldint);
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sigaction(SIGQUIT, &sa, &oldquit);
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sigprocmask(SIG_BLOCK, SIGALL_SET, &old);
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__acquire_ptc();
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pid = __vfork();
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if (pid) __release_ptc();
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if (pid > 0) {
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sigset_t new = old;
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sigaddset(&new, SIGCHLD);
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sigprocmask(SIG_BLOCK, &new, 0);
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while (waitpid(pid, &status, 0) && errno == EINTR);
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}
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if (pid) {
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sigaction(SIGINT, &oldint, NULL);
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sigaction(SIGQUIT, &oldquit, NULL);
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sigprocmask(SIG_SETMASK, &old, NULL);
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return status;
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}
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/* Before we can unblock signals in the child, all signal
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* handlers must be eliminated -- even implementation-internal
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* ones. Otherwise, a signal handler could run in the child
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* and clobber the parent's memory (due to vfork). */
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for (i=1; i<=8*__SYSCALL_SSLEN; i++) {
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struct sigaction sa;
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__libc_sigaction(i, 0, &sa);
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if (sa.sa_handler!=SIG_IGN && sa.sa_handler!=SIG_DFL) {
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sa.sa_handler = SIG_DFL;
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__libc_sigaction(i, &sa, 0);
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}
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}
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sigprocmask(SIG_SETMASK, &old, NULL);
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execl("/bin/sh", "sh", "-c", cmd, (char *)0);
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_exit(127);
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}
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