src/env/__libc_start_main.c

   1 #include <elf.h>
   2 #include <poll.h>
   3 #include <fcntl.h>
   4 #include <signal.h>
   5 #include "syscall.h"
   6 #include "atomic.h"
   7 #include "libc.h"
   8
   9 void __init_tls(size_t *);
  10
  11 extern void _init() __attribute__((weak));
  12 extern void (*const __init_array_start)() __attribute__((weak));
  13 extern void (*const __init_array_end)() __attribute__((weak));
  14
  15 static void dummy1(void *p) {}
  16 weak_alias(dummy1, __init_ssp);
  17
  18 #define AUX_CNT 38
  19
  20 void __init_libc(char **envp, char *pn)
  21 {
  22         size_t i, *auxv, aux[AUX_CNT] = { 0 };
  23         __environ = envp;
  24         for (i=0; envp[i]; i++);
  25         libc.auxv = auxv = (void *)(envp+i+1);
  26         for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
  27         __hwcap = aux[AT_HWCAP];
  28         __sysinfo = aux[AT_SYSINFO];
  29         libc.page_size = aux[AT_PAGESZ];
  30
  31         if (pn) {
  32                 __progname = __progname_full = pn;
  33                 for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
  34         }
  35
  36         __init_tls(aux);
  37         __init_ssp((void *)aux[AT_RANDOM]);
  38
  39         if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
  40                 && !aux[AT_SECURE]) return;
  41
  42         struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
  43 #ifdef SYS_poll
  44         __syscall(SYS_poll, pfd, 3, 0);
  45 #else
  46         __syscall(SYS_ppoll, pfd, 3, &(struct timespec){0}, 0, _NSIG/8);
  47 #endif
  48         for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
  49                 if (__sys_open("/dev/null", O_RDWR)<0)
  50                         a_crash();
  51         libc.secure = 1;
  52 }
  53
  54 static void libc_start_init(void)
  55 {
  56         if (_init) _init();
  57         uintptr_t a = (uintptr_t)&__init_array_start;
  58         for (; a<(uintptr_t)&__init_array_end; a+=sizeof(void(*)()))
  59                 (*(void (**)())a)();
  60 }
  61
  62 weak_alias(libc_start_init, __libc_start_init);
  63
  64 int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv)
  65 {
  66         char **envp = argv+argc+1;
  67
  68         __init_libc(envp, argv[0]);
  69         __libc_start_init();
  70
  71         /* Pass control to the application */
  72         exit(main(argc, argv, envp));
  73         return 0;
  74 }