glibc/sysdeps/generic/dl-sysdep.c

/* Operating system support for run-time dynamic linker.  Generic Unix version.
Copyright (C) 1995, 96 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <elf.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <link.h>
#include <unistd.h>
#include <stdarg.h>
#include <string.h>


extern int _dl_argc;
extern char **_dl_argv;
extern char **_environ;
extern void _start (void);

int __libc_enable_secure;

ElfW(Addr)
_dl_sysdep_start (void **start_argptr,
		  void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
				   ElfW(Addr) *user_entry))
{
  const ElfW(Phdr) *phdr;
  ElfW(Word) phnum;
  ElfW(Addr) user_entry;
  ElfW(auxv_t) *av;
  uid_t uid, euid;
  gid_t gid, egid;
  unsigned int seen;

  user_entry = (ElfW(Addr)) &_start;
  _dl_argc = *(long *) start_argptr;
  _dl_argv = (char **) start_argptr + 1;
  _environ = &_dl_argv[_dl_argc + 1];
  start_argptr = (void **) _environ;
  while (*start_argptr)
    ++start_argptr;

  seen = 0;
#define M(type) (1 << (type))

  for (av = (void *) ++start_argptr;
       av->a_type != AT_NULL;
       seen |= M ((++av)->a_type))
    switch (av->a_type)
      {
      case AT_PHDR:
	phdr = av->a_un.a_ptr;
	break;
      case AT_PHNUM:
	phnum = av->a_un.a_val;
	break;
      case AT_ENTRY:
	user_entry = av->a_un.a_val;
	break;
      case AT_UID:
	uid = av->a_un.a_val;
	break;
      case AT_GID:
	gid = av->a_un.a_val;
	break;
      case AT_EUID:
	euid = av->a_un.a_val;
	break;
      case AT_EGID:
	egid = av->a_un.a_val;
	break;
      }

  /* Linux doesn't provide us with any of these values on the stack
     when the dynamic linker is run directly as a program.  */

#define SEE(UID, uid) if ((seen & M (AT_##UID)) == 0) uid = __get##uid ()
  SEE (UID, uid);
  SEE (GID, gid);
  SEE (EUID, euid);
  SEE (EGID, egid);


  __libc_enable_secure = uid != euid || gid != egid;

#ifdef DL_SYSDEP_INIT
  DL_SYSDEP_INIT;
#endif

  (*dl_main) (phdr, phnum, &user_entry);
  return user_entry;
}

void
_dl_sysdep_start_cleanup (void)
{
}

#ifndef MAP_ANON
/* This is only needed if the system doesn't support MAP_ANON.  */

int
_dl_sysdep_open_zero_fill (void)
{
  return __open ("/dev/zero", O_RDONLY);
}
#endif

/* Read the whole contents of FILE into new mmap'd space with given
   protections.  *SIZEP gets the size of the file.  */

void *
_dl_sysdep_read_whole_file (const char *file, size_t *sizep, int prot)
{
  void *result;
  struct stat st;
  int fd = __open (file, O_RDONLY);
  if (fd < 0)
    return NULL;
  if (__fstat (fd, &st) < 0)
    result = NULL;
  else
    {
      /* Map a copy of the file contents.  */
      result = __mmap (0, st.st_size, prot,
#ifdef MAP_COPY
		       MAP_COPY
#else
		       MAP_PRIVATE
#endif
#ifdef MAP_FILE
		       | MAP_FILE
#endif
		       , fd, 0);
      if (result == (void *) -1)
	result = NULL;
      else
	*sizep = st.st_size;
    }
  __close (fd);
  return result;
}

void
_dl_sysdep_fatal (const char *msg, ...)
{
  va_list ap;

  va_start (ap, msg);
  do
    {
      size_t len = strlen (msg);
      __write (STDERR_FILENO, msg, len);
      msg = va_arg (ap, const char *);
    } while (msg);
  va_end (ap);

  _exit (127);
}


void
_dl_sysdep_message (const char *msg, ...)
{
  va_list ap;

  va_start (ap, msg);
  do
    {
      size_t len = strlen (msg);
      __write (STDOUT_FILENO, msg, len);
      msg = va_arg (ap, const char *);
    } while (msg);
  va_end (ap);
}