source: asp3_tinet_ecnl_rx/trunk/musl-1.1.18/src/unistd/setxid.c@ 342

#include <unistd.h>
#include <errno.h>
#include "syscall.h"
#include "libc.h"
#include "pthread_impl.h"

struct ctx {
        int id, eid, sid;
        int nr, err;
};

static void do_setxid(void *p)
{
        struct ctx *c = p;
        if (c->err>0) return;
        int ret = -__syscall_nr(c->nr, c->id, c->eid, c->sid);
        if (ret && !c->err) {
                /* If one thread fails to set ids after another has already
                 * succeeded, forcibly killing the process is the only safe
                 * thing to do. State is inconsistent and dangerous. Use
                 * SIGKILL because it is uncatchable. */
                __block_all_sigs(0);
                __syscall(SYS_kill, __syscall(SYS_getpid), SIGKILL);
        }
        c->err = ret;
}

int __setxid(int nr, int id, int eid, int sid)
{
        /* err is initially nonzero so that failure of the first thread does not
         * trigger the safety kill above. */
        struct ctx c = { .nr = nr, .id = id, .eid = eid, .sid = sid, .err = -1 };
        __synccall(do_setxid, &c);
        if (c.err) {
                if (c.err>0) errno = c.err;
                return -1;
        }
        return 0;
}