ClickHouse/libs/libglibc-compatibility/musl/posix_spawn.c

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/// Very limited implementation. Half of code from Musl was cut.
/// This is Ok, because for now, this function is used only from clang driver.
#define _GNU_SOURCE
#include <spawn.h>
#include <sched.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <syscall.h>
#include <sys/signal.h>
#include <pthread.h>
#include <spawn.h>
#include <errno.h>
#include "syscall.h"
struct args {
int p[2];
sigset_t oldmask;
const char *path;
int (*exec)(const char *, char *const *, char *const *);
const posix_spawn_file_actions_t *fa;
const posix_spawnattr_t *restrict attr;
char *const *argv, *const *envp;
};
void __get_handler_set(sigset_t *);
static int child(void *args_vp)
{
int ret;
struct args *args = args_vp;
int p = args->p[1];
const posix_spawnattr_t *restrict attr = args->attr;
close(args->p[0]);
/* Close-on-exec flag may have been lost if we moved the pipe
* to a different fd. We don't use F_DUPFD_CLOEXEC above because
* it would fail on older kernels and atomicity is not needed --
* in this process there are no threads or signal handlers. */
__syscall(SYS_fcntl, p, F_SETFD, FD_CLOEXEC);
pthread_sigmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
? &attr->__ss : &args->oldmask, 0);
args->exec(args->path, args->argv, args->envp);
ret = -errno;
/* Since sizeof errno < PIPE_BUF, the write is atomic. */
ret = -ret;
if (ret) while (__syscall(SYS_write, p, &ret, sizeof ret) < 0);
_exit(127);
}
int __posix_spawnx(pid_t *restrict res, const char *restrict path,
int (*exec)(const char *, char *const *, char *const *),
const posix_spawn_file_actions_t *fa,
const posix_spawnattr_t *restrict attr,
char *const argv[restrict], char *const envp[restrict])
{
pid_t pid;
char stack[1024];
int ec=0, cs;
struct args args;
if (pipe2(args.p, O_CLOEXEC))
return errno;
pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
args.path = path;
args.exec = exec;
args.fa = fa;
args.attr = attr ? attr : &(const posix_spawnattr_t){0};
args.argv = argv;
args.envp = envp;
pid = clone(child, stack+sizeof stack,
CLONE_VM|CLONE_VFORK|SIGCHLD, &args);
close(args.p[1]);
if (pid > 0) {
if (read(args.p[0], &ec, sizeof ec) != sizeof ec) ec = 0;
else waitpid(pid, &(int){0}, 0);
} else {
ec = -pid;
}
close(args.p[0]);
if (!ec && res) *res = pid;
pthread_setcancelstate(cs, 0);
return ec;
}
int posix_spawn(pid_t *restrict res, const char *restrict path,
const posix_spawn_file_actions_t *fa,
const posix_spawnattr_t *restrict attr,
char *const argv[restrict], char *const envp[restrict])
{
return __posix_spawnx(res, path, execve, fa, attr, argv, envp);
}