source: azure_iot_hub/trunk/musl-1.1.18/src/env/__libc_start_main.c@ 389

#include <elf.h>
#include <poll.h>
#include <fcntl.h>
#include <signal.h>
#include "syscall.h"
#include "atomic.h"
#include "libc.h"

void __init_tls(size_t *);

#ifndef __c2__
static void dummy(void) {}
weak_alias(dummy, _init);
#else
__attribute((weak))
void _init(void) {}
#endif

#ifndef __c2__
__attribute__((__weak__, __visibility__("hidden")))
extern void (*const __init_array_start)(void), (*const __init_array_end)(void);
#else
extern void(*const __init_array_start)(void);
#define __init_array_end __init_array_start
#endif

#ifndef __c2__
static void dummy1(void *p) {}
weak_alias(dummy1, __init_ssp);
#else
__attribute((weak))
void __init_ssp(void *p) {}
#endif

#define AUX_CNT 38

void __init_libc(char **envp, char *pn)
{
        size_t i, *auxv, aux[AUX_CNT] = { 0 };
        __environ = envp;
        for (i=0; envp[i]; i++);
        libc.auxv = auxv = (void *)(envp+i+1);
        for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
        __hwcap = aux[AT_HWCAP];
        __sysinfo = aux[AT_SYSINFO];
        libc.page_size = aux[AT_PAGESZ];

        if (!pn) pn = (void*)aux[AT_EXECFN];
        if (!pn) pn = "";
        __progname = __progname_full = pn;
        for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;

        __init_tls(aux);
        __init_ssp((void *)aux[AT_RANDOM]);

        if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
                && !aux[AT_SECURE]) return;

        struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
#ifdef SYS_poll
        __syscall(SYS_poll, pfd, 3, 0);
#else
        __syscall(SYS_ppoll, pfd, 3, &(struct timespec){0}, 0, _NSIG/8);
#endif
        for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
                if (__sys_open("/dev/null", O_RDWR)<0)
                        a_crash();
        libc.secure = 1;
}

static void libc_start_init(void)
{
        _init();
        uintptr_t a = (uintptr_t)&__init_array_start;
        for (; a<(uintptr_t)&__init_array_end; a+=sizeof(void(*)()))
                (*(void (**)(void))a)();
}

#ifndef __c2__
weak_alias(libc_start_init, __libc_start_init);
#else
void __libc_start_init(void)
{
        libc_start_init();
}
#undef exit
#define exit(x) x
#endif

int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv)
{
        char **envp = argv+argc+1;

        __init_libc(envp, argv[0]);
        __libc_start_init();

        /* Pass control to the application */
        exit(main(argc, argv, envp));
        return 0;
}