[352] | 1 | #define _GNU_SOURCE
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| 2 | #include <spawn.h>
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| 3 | #include <sched.h>
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| 4 | #include <unistd.h>
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| 5 | #include <signal.h>
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| 6 | #include <fcntl.h>
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| 7 | #include <sys/wait.h>
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| 8 | #include "syscall.h"
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| 9 | #include "pthread_impl.h"
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| 10 | #include "fdop.h"
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| 11 | #include "libc.h"
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| 12 |
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| 13 | struct args {
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| 14 | int p[2];
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| 15 | sigset_t oldmask;
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| 16 | const char *path;
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| 17 | int (*exec)(const char *, char *const *, char *const *);
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| 18 | const posix_spawn_file_actions_t *fa;
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| 19 | const posix_spawnattr_t *restrict attr;
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| 20 | char *const *argv, *const *envp;
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| 21 | };
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| 22 |
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| 23 | void __get_handler_set(sigset_t *);
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| 24 |
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| 25 | static int __sys_dup2(int old, int new)
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| 26 | {
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| 27 | #ifdef SYS_dup2
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| 28 | return __syscall(SYS_dup2, old, new);
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| 29 | #else
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| 30 | if (old==new) {
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| 31 | int r = __syscall(SYS_fcntl, old, F_GETFD);
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| 32 | return r<0 ? r : old;
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| 33 | } else {
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| 34 | return __syscall(SYS_dup3, old, new, 0);
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| 35 | }
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| 36 | #endif
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| 37 | }
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| 38 |
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| 39 | static int child(void *args_vp)
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| 40 | {
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| 41 | int i, ret;
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| 42 | struct sigaction sa = {0};
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| 43 | struct args *args = args_vp;
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| 44 | int p = args->p[1];
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| 45 | const posix_spawn_file_actions_t *fa = args->fa;
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| 46 | const posix_spawnattr_t *restrict attr = args->attr;
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| 47 | sigset_t hset;
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| 48 |
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| 49 | close(args->p[0]);
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| 50 |
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| 51 | /* All signal dispositions must be either SIG_DFL or SIG_IGN
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| 52 | * before signals are unblocked. Otherwise a signal handler
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| 53 | * from the parent might get run in the child while sharing
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| 54 | * memory, with unpredictable and dangerous results. To
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| 55 | * reduce overhead, sigaction has tracked for us which signals
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| 56 | * potentially have a signal handler. */
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| 57 | __get_handler_set(&hset);
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| 58 | for (i=1; i<_NSIG; i++) {
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| 59 | if ((attr->__flags & POSIX_SPAWN_SETSIGDEF)
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| 60 | && sigismember(&attr->__def, i)) {
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| 61 | sa.sa_handler = SIG_DFL;
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| 62 | } else if (sigismember(&hset, i)) {
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| 63 | if (i-32<3U) {
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| 64 | sa.sa_handler = SIG_IGN;
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| 65 | } else {
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| 66 | __libc_sigaction(i, 0, &sa);
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| 67 | if (sa.sa_handler==SIG_IGN) continue;
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| 68 | sa.sa_handler = SIG_DFL;
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| 69 | }
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| 70 | } else {
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| 71 | continue;
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| 72 | }
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| 73 | __libc_sigaction(i, &sa, 0);
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| 74 | }
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| 75 |
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| 76 | if (attr->__flags & POSIX_SPAWN_SETSID)
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| 77 | if ((ret=__syscall(SYS_setsid)) < 0)
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| 78 | goto fail;
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| 79 |
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| 80 | if (attr->__flags & POSIX_SPAWN_SETPGROUP)
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| 81 | if ((ret=__syscall(SYS_setpgid, 0, attr->__pgrp)))
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| 82 | goto fail;
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| 83 |
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| 84 | /* Use syscalls directly because the library functions attempt
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| 85 | * to do a multi-threaded synchronized id-change, which would
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| 86 | * trash the parent's state. */
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| 87 | if (attr->__flags & POSIX_SPAWN_RESETIDS)
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| 88 | if ((ret=__syscall(SYS_setgid, __syscall(SYS_getgid))) ||
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| 89 | (ret=__syscall(SYS_setuid, __syscall(SYS_getuid))) )
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| 90 | goto fail;
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| 91 |
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| 92 | if (fa && fa->__actions) {
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| 93 | struct fdop *op;
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| 94 | int fd;
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| 95 | for (op = fa->__actions; op->next; op = op->next);
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| 96 | for (; op; op = op->prev) {
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| 97 | /* It's possible that a file operation would clobber
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| 98 | * the pipe fd used for synchronizing with the
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| 99 | * parent. To avoid that, we dup the pipe onto
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| 100 | * an unoccupied fd. */
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| 101 | if (op->fd == p) {
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| 102 | ret = __syscall(SYS_dup, p);
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| 103 | if (ret < 0) goto fail;
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| 104 | __syscall(SYS_close, p);
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| 105 | p = ret;
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| 106 | }
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| 107 | switch(op->cmd) {
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| 108 | case FDOP_CLOSE:
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| 109 | __syscall(SYS_close, op->fd);
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| 110 | break;
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| 111 | case FDOP_DUP2:
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| 112 | if ((ret=__sys_dup2(op->srcfd, op->fd))<0)
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| 113 | goto fail;
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| 114 | break;
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| 115 | case FDOP_OPEN:
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| 116 | fd = __sys_open(op->path, op->oflag, op->mode);
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| 117 | if ((ret=fd) < 0) goto fail;
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| 118 | if (fd != op->fd) {
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| 119 | if ((ret=__sys_dup2(fd, op->fd))<0)
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| 120 | goto fail;
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| 121 | __syscall(SYS_close, fd);
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| 122 | }
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| 123 | break;
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| 124 | }
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| 125 | }
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| 126 | }
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| 127 |
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| 128 | /* Close-on-exec flag may have been lost if we moved the pipe
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| 129 | * to a different fd. We don't use F_DUPFD_CLOEXEC above because
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| 130 | * it would fail on older kernels and atomicity is not needed --
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| 131 | * in this process there are no threads or signal handlers. */
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| 132 | __syscall(SYS_fcntl, p, F_SETFD, FD_CLOEXEC);
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| 133 |
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| 134 | pthread_sigmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
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| 135 | ? &attr->__mask : &args->oldmask, 0);
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| 136 |
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| 137 | args->exec(args->path, args->argv, args->envp);
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| 138 | ret = -errno;
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| 139 |
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| 140 | fail:
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| 141 | /* Since sizeof errno < PIPE_BUF, the write is atomic. */
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| 142 | ret = -ret;
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| 143 | if (ret) while (__syscall(SYS_write, p, &ret, sizeof ret) < 0);
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| 144 | _exit(127);
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| 145 | }
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| 146 |
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| 147 |
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| 148 | int __posix_spawnx(pid_t *restrict res, const char *restrict path,
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| 149 | int (*exec)(const char *, char *const *, char *const *),
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| 150 | const posix_spawn_file_actions_t *fa,
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| 151 | const posix_spawnattr_t *restrict attr,
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| 152 | char *const argv[restrict], char *const envp[restrict])
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| 153 | {
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| 154 | pid_t pid;
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| 155 | char stack[1024+PATH_MAX];
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| 156 | int ec=0, cs;
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| 157 | struct args args;
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| 158 |
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| 159 | if (pipe2(args.p, O_CLOEXEC))
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| 160 | return errno;
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| 161 |
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| 162 | pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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| 163 |
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| 164 | args.path = path;
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| 165 | args.exec = exec;
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| 166 | args.fa = fa;
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| 167 | args.attr = attr ? attr : &(const posix_spawnattr_t){0};
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| 168 | args.argv = argv;
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| 169 | args.envp = envp;
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| 170 | pthread_sigmask(SIG_BLOCK, SIGALL_SET, &args.oldmask);
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| 171 |
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| 172 | pid = __clone(child, stack+sizeof stack,
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| 173 | CLONE_VM|CLONE_VFORK|SIGCHLD, &args);
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| 174 | close(args.p[1]);
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| 175 |
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| 176 | if (pid > 0) {
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| 177 | if (read(args.p[0], &ec, sizeof ec) != sizeof ec) ec = 0;
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| 178 | else waitpid(pid, &(int){0}, 0);
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| 179 | } else {
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| 180 | ec = -pid;
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| 181 | }
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| 182 |
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| 183 | close(args.p[0]);
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| 184 |
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| 185 | if (!ec && res) *res = pid;
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| 186 |
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| 187 | pthread_sigmask(SIG_SETMASK, &args.oldmask, 0);
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| 188 | pthread_setcancelstate(cs, 0);
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| 189 |
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| 190 | return ec;
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| 191 | }
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| 192 |
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| 193 | int posix_spawn(pid_t *restrict res, const char *restrict path,
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| 194 | const posix_spawn_file_actions_t *fa,
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| 195 | const posix_spawnattr_t *restrict attr,
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| 196 | char *const argv[restrict], char *const envp[restrict])
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| 197 | {
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| 198 | return __posix_spawnx(res, path, execve, fa, attr, argv, envp);
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| 199 | }
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