[glibc.git] / elf / rtld.c

/* Run time dynamic linker.
Copyright (C) 1995 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 <link.h>
#include "dynamic-link.h"
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>


#ifdef RTLD_START
RTLD_START
#else
#error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START"
#endif

/* System-specific function to do initial startup for the dynamic linker.
   After this, file access calls and getenv must work.  This is responsible
   for setting _dl_secure if we need to be secure (e.g. setuid),
   and for setting _dl_argc and _dl_argv, and then calling _dl_main.  */
extern Elf32_Addr _dl_sysdep_start (void **start_argptr,
				    void (*dl_main) (const Elf32_Phdr *phdr,
						     Elf32_Word phent,
						     Elf32_Addr *user_entry));

int _dl_secure;
int _dl_argc;
char **_dl_argv;

struct r_debug dl_r_debug;

static void dl_main (const Elf32_Phdr *phdr,
		     Elf32_Word phent,
		     Elf32_Addr *user_entry);

Elf32_Addr
_dl_start (void *arg)
{
  struct link_map rtld_map;

  /* Figure out the run-time load address of the dynamic linker itself.  */
  rtld_map.l_addr = elf_machine_load_address ();

  /* Read our own dynamic section and fill in the info array.
     Conveniently, the first element of the GOT contains the
     offset of _DYNAMIC relative to the run-time load address.  */
  rtld_map.l_ld = (void *) rtld_map.l_addr + *elf_machine_got ();
  elf_get_dynamic_info (rtld_map.l_ld, rtld_map.l_info);

#ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
  ELF_MACHINE_BEFORE_RTLD_RELOC (rtld_map.l_info);
#endif

  /* Relocate ourselves so we can do normal function calls and
     data access using the global offset table.  */

  ELF_DYNAMIC_RELOCATE (&rtld_map, 0, NULL);


  /* Now life is sane; we can call functions and access global data.
     Set up to use the operating system facilities, and find out from
     the operating system's program loader where to find the program
     header table in core.  */

  dl_r_debug.r_ldbase = rtld_map.l_addr; /* Record our load address.  */

  /* Call the OS-dependent function to set up life so we can do things like
     file access.  It will call `dl_main' (below) to do all the real work
     of the dynamic linker, and then unwind our frame and run the user
     entry point on the same stack we entered on.  */
  return _dl_sysdep_start (&arg, &dl_main);
}


/* Now life is peachy; we can do all normal operations.
   On to the real work.  */

void _start (void);

static void
dl_main (const Elf32_Phdr *phdr,
	 Elf32_Word phent,
	 Elf32_Addr *user_entry)
{
  void doit (void)
    {
      const Elf32_Phdr *ph;
      struct link_map *l;
      const char *interpreter_name;
      int lazy;

      if (*user_entry == (Elf32_Addr) &_start)
	{
	  /* Ho ho.  We are not the program interpreter!  We are the program
	     itself!  This means someone ran ld.so as a command.  Well, that
	     might be convenient to do sometimes.  We support it by
	     interpreting the args like this:
	     
	     ld.so PROGRAM ARGS...
	     
	     The first argument is the name of a file containing an ELF
	     executable we will load and run with the following arguments.
	     To simplify life here, PROGRAM is searched for using the
	     normal rules for shared objects, rather than $PATH or anything
	     like that.  We just load it and use its entry point; we don't
	     pay attention to its PT_INTERP command (we are the interpreter
	     ourselves).  This is an easy way to test a new ld.so before
	     installing it.  */
	  if (_dl_argc < 2)
	    _dl_sysdep_fatal ("\
Usage: ld.so EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
You have invoked `ld.so', the helper program for shared library executables.\n\
This program usually lives in the file `/lib/ld.so', and special directives\n\
in executable files using ELF shared libraries tell the system's program\n\
loader to load the helper program from this file.  This helper program loads\n\
the shared libraries needed by the program executable, prepares the program\n\
to run, and runs it.  You may invoke this helper program directly from the\n\
command line to load and run an ELF executable file; this is like executing\n\
that file itself, but always uses this helper program from the file you\n\
specified, instead of the helper program file specified in the executable\n\
file you run.  This is mostly of use for maintainers to test new versions\n\
of this helper program; chances are you did not intend to run this program.\n"
			      );

	  interpreter_name = _dl_argv[0];
	  --_dl_argc;
	  ++_dl_argv;
	  l = _dl_map_object (NULL, _dl_argv[0], user_entry);
	  phdr = l->l_phdr;
	  phent = l->l_phnum;
	  l->l_type = lt_executable;
	  l->l_libname = (char *) "";
	}
      else
	{
	  /* Create a link_map for the executable itself.
	     This will be what dlopen on "" returns.  */
	  l = _dl_new_object ((char *) "", "", lt_executable);
	  l->l_phdr = phdr;
	  l->l_phnum = phent;
	  interpreter_name = 0;
	}

      /* Scan the program header table for the dynamic section.  */
      for (ph = phdr; ph < &phdr[phent]; ++ph)
	switch (ph->p_type)
	  {
	  case PT_DYNAMIC:
	    /* This tells us where to find the dynamic section,
	       which tells us everything we need to do.  */
	    l->l_ld = (void *) ph->p_vaddr;
	    break;
	  case PT_INTERP:
	    /* This "interpreter segment" was used by the program loader to
	       find the program interpreter, which is this program itself, the
	       dynamic linker.  We note what name finds us, so that a future
	       dlopen call or DT_NEEDED entry, for something that wants to link
	       against the dynamic linker as a shared library, will know that
	       the shared object is already loaded.  */
	    interpreter_name = (void *) ph->p_vaddr;
	    break;
	  }
      assert (interpreter_name); /* How else did we get here?  */

      /* Extract the contents of the dynamic section for easy access.  */
      elf_get_dynamic_info (l->l_ld, l->l_info);
      /* Set up our cache of pointers into the hash table.  */
      _dl_setup_hash (l);

      if (l->l_info[DT_DEBUG])
	/* There is a DT_DEBUG entry in the dynamic section.  Fill it in
	   with the run-time address of the r_debug structure, which we
	   will set up later to communicate with the debugger.  */
	l->l_info[DT_DEBUG]->d_un.d_ptr = (Elf32_Addr) &dl_r_debug;

      l = _dl_new_object ((char *) interpreter_name, interpreter_name,
			  lt_interpreter);

      /* Now process all the DT_NEEDED entries and map in the objects.
	 Each new link_map will go on the end of the chain, so we will
	 come across it later in the loop to map in its dependencies.  */
      for (l = _dl_loaded; l; l = l->l_next)
	{
	  if (l->l_info[DT_NEEDED])
	    {
	      const char *strtab
		= (void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr;
	      const Elf32_Dyn *d;
	      for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
		if (d->d_tag == DT_NEEDED)
		  _dl_map_object (l, strtab + d->d_un.d_val, NULL);
	    }
	  l->l_deps_loaded = 1;
	}

      l = _dl_loaded->l_next;
      assert (l->l_type == lt_interpreter);
      if (l->l_opencount == 0)
	{
	  /* No DT_NEEDED entry referred to the interpreter object itself.
	     Remove it from the maps we will use for symbol resolution.  */
	  l->l_prev->l_next = l->l_next;
	  if (l->l_next)
	    l->l_next->l_prev = l->l_prev;
	}

      lazy = _dl_secure || *(getenv ("LD_BIND_NOW") ?: "");

      /* Now we have all the objects loaded.  Relocate them all.
	 We do this in reverse order so that copy relocs of earlier
	 objects overwrite the data written by later objects.  */
      l = _dl_loaded;
      while (l->l_next)
	l = l->l_next;
      do
	{
	  _dl_relocate_object (l, lazy);
	  l = l->l_prev;
	} while (l);

      /* Tell the debugger where to find the map of loaded objects.  */
      dl_r_debug.r_version = 1	/* R_DEBUG_VERSION XXX */;
      dl_r_debug.r_map = _dl_loaded;
      dl_r_debug.r_brk = (Elf32_Addr) &_dl_r_debug_state;
    }
  const char *errstring;
  const char *errobj;
  int err;

  err = _dl_catch_error (&errstring, &errobj, &doit);
  if (errstring)
    _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
		      ": error in loading shared libraries\n",
		      errobj ?: "", errobj ? ": " : "",
		      errstring, err ? ": " : NULL,
		      err ? strerror (err) : NULL, NULL);

  /* Once we return, _dl_sysdep_start will invoke
     the DT_INIT functions and then *USER_ENTRY.  */
}

/* This function exists solely to have a breakpoint set on it by the 
   debugger.  */
void
_dl_r_debug_state (void)
{
}
Commit	Line	Data
d66e34cd RM	1	/* Run time dynamic linker.
	2	Copyright (C) 1995 Free Software Foundation, Inc.
	3	This file is part of the GNU C Library.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Library General Public License as
	7	published by the Free Software Foundation; either version 2 of the
	8	License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Library General Public License for more details.
	14
	15	You should have received a copy of the GNU Library General Public
	16	License along with the GNU C Library; see the file COPYING.LIB. If
	17	not, write to the Free Software Foundation, Inc., 675 Mass Ave,
	18	Cambridge, MA 02139, USA. */
	19
	20	#include <link.h>
	21	#include "dynamic-link.h"
	22	#include <stddef.h>
	23	#include <stdlib.h>
	24	#include <unistd.h>
	25
	26
	27	#ifdef RTLD_START
	28	RTLD_START
	29	#else
	30	#error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START"
	31	#endif
	32
	33	/* System-specific function to do initial startup for the dynamic linker.
	34	After this, file access calls and getenv must work. This is responsible
	35	for setting _dl_secure if we need to be secure (e.g. setuid),
	36	and for setting _dl_argc and _dl_argv, and then calling _dl_main. */
	37	extern Elf32_Addr _dl_sysdep_start (void **start_argptr,
	38	void (dl_main) (const Elf32_Phdr phdr,
	39	Elf32_Word phent,
	40	Elf32_Addr *user_entry));
	41
	42	int _dl_secure;
	43	int _dl_argc;
	44	char **_dl_argv;
	45
	46	struct r_debug dl_r_debug;
	47
	48	static void dl_main (const Elf32_Phdr *phdr,
	49	Elf32_Word phent,
	50	Elf32_Addr *user_entry);
	51
	52	Elf32_Addr
	53	_dl_start (void *arg)
	54	{
421f82e5	55	struct link_map rtld_map;
d66e34cd RM	56
d66e34cd RM	57	/* Figure out the run-time load address of the dynamic linker itself. */
421f82e5	58	rtld_map.l_addr = elf_machine_load_address ();
d66e34cd RM	59
	60	/* Read our own dynamic section and fill in the info array.
	61	Conveniently, the first element of the GOT contains the
	62	offset of _DYNAMIC relative to the run-time load address. */
421f82e5 RM	63	rtld_map.l_ld = (void ) rtld_map.l_addr + elf_machine_got ();
421f82e5 RM	64	elf_get_dynamic_info (rtld_map.l_ld, rtld_map.l_info);
d66e34cd RM	65
d66e34cd RM	66	#ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
421f82e5	67	ELF_MACHINE_BEFORE_RTLD_RELOC (rtld_map.l_info);
d66e34cd RM	68	#endif
	69
	70	/* Relocate ourselves so we can do normal function calls and
	71	data access using the global offset table. */
421f82e5 RM	72
	73	ELF_DYNAMIC_RELOCATE (&rtld_map, 0, NULL);
	74
d66e34cd RM	75
	76	/* Now life is sane; we can call functions and access global data.
	77	Set up to use the operating system facilities, and find out from
	78	the operating system's program loader where to find the program
	79	header table in core. */
	80
421f82e5	81	dl_r_debug.r_ldbase = rtld_map.l_addr; /* Record our load address. */
d66e34cd RM	82
	83	/* Call the OS-dependent function to set up life so we can do things like
	84	file access. It will call `dl_main' (below) to do all the real work
	85	of the dynamic linker, and then unwind our frame and run the user
	86	entry point on the same stack we entered on. */
	87	return _dl_sysdep_start (&arg, &dl_main);
	88	}
	89
	90
	91	/* Now life is peachy; we can do all normal operations.
	92	On to the real work. */
	93
	94	void _start (void);
	95
	96	static void
	97	dl_main (const Elf32_Phdr *phdr,
	98	Elf32_Word phent,
	99	Elf32_Addr *user_entry)
	100	{
	101	void doit (void)
	102	{
421f82e5 RM	103	const Elf32_Phdr *ph;
	104	struct link_map *l;
	105	const char *interpreter_name;
	106	int lazy;
d66e34cd	107
421f82e5 RM	108	if (*user_entry == (Elf32_Addr) &_start)
	109	{
	110	/* Ho ho. We are not the program interpreter! We are the program
	111	itself! This means someone ran ld.so as a command. Well, that
	112	might be convenient to do sometimes. We support it by
	113	interpreting the args like this:
	114
	115	ld.so PROGRAM ARGS...
	116
	117	The first argument is the name of a file containing an ELF
	118	executable we will load and run with the following arguments.
	119	To simplify life here, PROGRAM is searched for using the
	120	normal rules for shared objects, rather than $PATH or anything
	121	like that. We just load it and use its entry point; we don't
	122	pay attention to its PT_INTERP command (we are the interpreter
	123	ourselves). This is an easy way to test a new ld.so before
	124	installing it. */
	125	if (_dl_argc < 2)
	126	_dl_sysdep_fatal ("\
d66e34cd RM	127	Usage: ld.so EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
	128	You have invoked `ld.so', the helper program for shared library executables.\n\
	129	This program usually lives in the file `/lib/ld.so', and special directives\n\
	130	in executable files using ELF shared libraries tell the system's program\n\
	131	loader to load the helper program from this file. This helper program loads\n\
	132	the shared libraries needed by the program executable, prepares the program\n\
	133	to run, and runs it. You may invoke this helper program directly from the\n\
	134	command line to load and run an ELF executable file; this is like executing\n\
	135	that file itself, but always uses this helper program from the file you\n\
	136	specified, instead of the helper program file specified in the executable\n\
	137	file you run. This is mostly of use for maintainers to test new versions\n\
	138	of this helper program; chances are you did not intend to run this program.\n"
421f82e5 RM	139	);
	140
	141	interpreter_name = _dl_argv[0];
	142	--_dl_argc;
	143	++_dl_argv;
	144	l = _dl_map_object (NULL, _dl_argv[0], user_entry);
	145	phdr = l->l_phdr;
	146	phent = l->l_phnum;
	147	l->l_type = lt_executable;
	148	l->l_libname = (char *) "";
	149	}
	150	else
	151	{
	152	/* Create a link_map for the executable itself.
	153	This will be what dlopen on "" returns. */
	154	l = _dl_new_object ((char *) "", "", lt_executable);
	155	l->l_phdr = phdr;
	156	l->l_phnum = phent;
	157	interpreter_name = 0;
	158	}
d66e34cd	159
421f82e5 RM	160	/* Scan the program header table for the dynamic section. */
	161	for (ph = phdr; ph < &phdr[phent]; ++ph)
	162	switch (ph->p_type)
	163	{
	164	case PT_DYNAMIC:
	165	/* This tells us where to find the dynamic section,
	166	which tells us everything we need to do. */
	167	l->l_ld = (void *) ph->p_vaddr;
	168	break;
	169	case PT_INTERP:
	170	/* This "interpreter segment" was used by the program loader to
	171	find the program interpreter, which is this program itself, the
	172	dynamic linker. We note what name finds us, so that a future
	173	dlopen call or DT_NEEDED entry, for something that wants to link
	174	against the dynamic linker as a shared library, will know that
	175	the shared object is already loaded. */
	176	interpreter_name = (void *) ph->p_vaddr;
	177	break;
	178	}
	179	assert (interpreter_name); /* How else did we get here? */
	180
	181	/* Extract the contents of the dynamic section for easy access. */
	182	elf_get_dynamic_info (l->l_ld, l->l_info);
	183	/* Set up our cache of pointers into the hash table. */
	184	_dl_setup_hash (l);
	185
	186	if (l->l_info[DT_DEBUG])
	187	/* There is a DT_DEBUG entry in the dynamic section. Fill it in
	188	with the run-time address of the r_debug structure, which we
	189	will set up later to communicate with the debugger. */
	190	l->l_info[DT_DEBUG]->d_un.d_ptr = (Elf32_Addr) &dl_r_debug;
	191
	192	l = _dl_new_object ((char *) interpreter_name, interpreter_name,
	193	lt_interpreter);
	194
	195	/* Now process all the DT_NEEDED entries and map in the objects.
	196	Each new link_map will go on the end of the chain, so we will
	197	come across it later in the loop to map in its dependencies. */
	198	for (l = _dl_loaded; l; l = l->l_next)
d66e34cd	199	{
421f82e5 RM	200	if (l->l_info[DT_NEEDED])
	201	{
	202	const char *strtab
	203	= (void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr;
	204	const Elf32_Dyn *d;
	205	for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
	206	if (d->d_tag == DT_NEEDED)
	207	_dl_map_object (l, strtab + d->d_un.d_val, NULL);
	208	}
	209	l->l_deps_loaded = 1;
d66e34cd	210	}
d66e34cd	211
421f82e5 RM	212	l = _dl_loaded->l_next;
	213	assert (l->l_type == lt_interpreter);
	214	if (l->l_opencount == 0)
	215	{
	216	/* No DT_NEEDED entry referred to the interpreter object itself.
	217	Remove it from the maps we will use for symbol resolution. */
	218	l->l_prev->l_next = l->l_next;
	219	if (l->l_next)
	220	l->l_next->l_prev = l->l_prev;
	221	}
d66e34cd	222
421f82e5	223	lazy = _dl_secure \|\| *(getenv ("LD_BIND_NOW") ?: "");
d66e34cd	224
421f82e5 RM	225	/* Now we have all the objects loaded. Relocate them all.
	226	We do this in reverse order so that copy relocs of earlier
	227	objects overwrite the data written by later objects. */
	228	l = _dl_loaded;
	229	while (l->l_next)
	230	l = l->l_next;
	231	do
	232	{
	233	_dl_relocate_object (l, lazy);
	234	l = l->l_prev;
	235	} while (l);
	236
	237	/* Tell the debugger where to find the map of loaded objects. */
	238	dl_r_debug.r_version = 1 /* R_DEBUG_VERSION XXX */;
	239	dl_r_debug.r_map = _dl_loaded;
	240	dl_r_debug.r_brk = (Elf32_Addr) &_dl_r_debug_state;
	241	}
d66e34cd	242	const char *errstring;
421f82e5	243	const char *errobj;
d66e34cd RM	244	int err;
d66e34cd RM	245
421f82e5	246	err = _dl_catch_error (&errstring, &errobj, &doit);
d66e34cd RM	247	if (errstring)
	248	_dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>",
	249	": error in loading shared libraries\n",
421f82e5	250	errobj ?: "", errobj ? ": " : "",
d66e34cd RM	251	errstring, err ? ": " : NULL,
	252	err ? strerror (err) : NULL, NULL);
	253
	254	/* Once we return, _dl_sysdep_start will invoke
	255	the DT_INIT functions and then USER_ENTRY. /
	256	}
	257
	258	/* This function exists solely to have a breakpoint set on it by the
	259	debugger. */
	260	void
	261	_dl_r_debug_state (void)
	262	{
	263	}