dl-reloc.c

Newlib 嵌入式 C库 标准实现代码

/* Relocate a shared object and resolve its references to other loaded objects.
   Copyright (C) 1995,96,97,98,99,2000,2001 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <errno.h>
#include <libintl.h>
#include <stdlib.h>
#include <unistd.h>
#include <ldsodefs.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/types.h>
#include "dynamic-link.h"

/* Statistics function.  */
unsigned long int _dl_num_cache_relocations;


void
_dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
		     int lazy, int consider_profiling)
{
  struct textrels
  {
    caddr_t start;
    size_t len;
    int prot;
    struct textrels *next;
  } *textrels = NULL;
  /* Initialize it to make the compiler happy.  */
  const char *errstring = NULL;

  if (l->l_relocated)
    return;

  /* If DT_BIND_NOW is set relocate all references in this object.  We
     do not do this if we are profiling, of course.  */
  if (!consider_profiling
      && __builtin_expect (l->l_info[DT_BIND_NOW] != NULL, 0))
    lazy = 0;

  if (__builtin_expect (_dl_debug_mask & DL_DEBUG_RELOC, 0))
    _dl_printf ("\nrelocation processing: %s%s\n",
		l->l_name[0] ? l->l_name : _dl_argv[0], lazy ? " (lazy)" : "");

  /* DT_TEXTREL is now in level 2 and might phase out at some time.
     But we rewrite the DT_FLAGS entry to a DT_TEXTREL entry to make
     testing easier and therefore it will be available at all time.  */
  if (__builtin_expect (l->l_info[DT_TEXTREL] != NULL, 0))
    {
      /* Bletch.  We must make read-only segments writable
	 long enough to relocate them.  */
      const ElfW(Phdr) *ph;
      for (ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
	if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W) == 0)
	  {
	    struct textrels *newp;

	    newp = (struct textrels *) alloca (sizeof (*newp));
	    newp->len = (((ph->p_vaddr + ph->p_memsz + _dl_pagesize - 1)
			  & ~(_dl_pagesize - 1))
			 - (ph->p_vaddr & ~(_dl_pagesize - 1)));
	    newp->start = ((ph->p_vaddr & ~(_dl_pagesize - 1))
			   + (caddr_t) l->l_addr);

	    if (mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
	      {
		errstring = N_("cannot make segment writable for relocation");
	      call_error:
		_dl_signal_error (errno, l->l_name, NULL, errstring);
	      }

#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
	    newp->prot = (PF_TO_PROT
			  >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
#else
	    newp->prot = 0;
	    if (ph->p_flags & PF_R)
	      newp->prot |= PROT_READ;
	    if (ph->p_flags & PF_W)
	      newp->prot |= PROT_WRITE;
	    if (ph->p_flags & PF_X)
	      newp->prot |= PROT_EXEC;
#endif
	    newp->next = textrels;
	    textrels = newp;
	  }
    }

  {
    /* Do the actual relocation of the object's GOT and other data.  */

    /* This macro is used as a callback from the ELF_DYNAMIC_RELOCATE code.  */
#define RESOLVE_MAP(ref, version, r_type, scope) \
    (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL			      \
     ? ((__builtin_expect ((*ref) == map->l_lookup_cache.sym, 0)	      \
	 && elf_machine_type_class (r_type) == map->l_lookup_cache.type_class)\
	? (++_dl_num_cache_relocations,					      \
	   (*ref) = map->l_lookup_cache.ret,				      \
	   map->l_lookup_cache.value)					      \
	: ({ lookup_t _lr;						      \
	     int _tc = elf_machine_type_class (r_type);			      \
	     map->l_lookup_cache.type_class = _tc;			      \
	     map->l_lookup_cache.sym = (*ref);				      \
	     _lr = ((version) != NULL && (version)->hash != 0		      \
		    ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name,  \
						   map, (ref), scope,	      \
						   (version), _tc, 0)	      \
		    : _dl_lookup_symbol (strtab + (*ref)->st_name, map, (ref),\
					 scope, _tc, 0));		      \
	     map->l_lookup_cache.ret = (*ref);				      \
	     map->l_lookup_cache.value = _lr; }))				      \
     : map)
#define RESOLVE(ref, version, r_type, scope) \
    (ELFW(ST_BIND) ((*ref)->st_info) != STB_LOCAL			      \
     ? ((__builtin_expect ((*ref) == map->l_lookup_cache.sym, 0)	      \
	 && elf_machine_type_class (r_type) == map->l_lookup_cache.type_class)\
	? (++_dl_num_cache_relocations,					      \
	   (*ref) = map->l_lookup_cache.ret,				      \
	   map->l_lookup_cache.value)					      \
	: ({ lookup_t _lr;						      \
	     int _tc = elf_machine_type_class (r_type);			      \
	     map->l_lookup_cache.type_class = _tc;			      \
	     map->l_lookup_cache.sym = (*ref);				      \
	     _lr = ((version) != NULL && (version)->hash != 0		      \
		    ? _dl_lookup_versioned_symbol (strtab + (*ref)->st_name,  \
						   map, (ref), scope,	      \
						   (version), _tc, 0)	      \
		    : _dl_lookup_symbol (strtab + (*ref)->st_name, map, (ref),\
					 scope, _tc, 0));		      \
	     map->l_lookup_cache.ret = (*ref);				      \
	     map->l_lookup_cache.value = _lr; }))			      \
     : map->l_addr)

#include "dynamic-link.h"

    ELF_DYNAMIC_RELOCATE (l, lazy, consider_profiling);

    if (__builtin_expect (consider_profiling, 0))
      {
	/* Allocate the array which will contain the already found
	   relocations.  If the shared object lacks a PLT (for example
	   if it only contains lead function) the l_info[DT_PLTRELSZ]
	   will be NULL.  */
	if (l->l_info[DT_PLTRELSZ] == NULL)
	  {
	    errstring = N_("%s: profiler found no PLTREL in object %s\n");
	  fatal:
	    _dl_fatal_printf (errstring,
			      _dl_argv[0] ?: "<program name unknown>",
			      l->l_name);
	  }

	l->l_reloc_result =
	  (ElfW(Addr) *) calloc (sizeof (ElfW(Addr)),
				 l->l_info[DT_PLTRELSZ]->d_un.d_val);
	if (l->l_reloc_result == NULL)
	  {
	    errstring = N_("\
%s: profiler out of memory shadowing PLTREL of %s\n");
	    goto fatal;
	  }
      }
  }

  /* Mark the object so we know this work has been done.  */
  l->l_relocated = 1;

  /* Undo the segment protection changes.  */
  while (__builtin_expect (textrels != NULL, 0))
    {
      if (mprotect (textrels->start, textrels->len, textrels->prot) < 0)
	{
	  errstring = N_("cannot restore segment prot after reloc");
	  goto call_error;
	}

      textrels = textrels->next;
    }
}

#include <machine/dl-machine.h>

void
internal_function
_dl_reloc_bad_type (struct link_map *map, unsigned int type, int plt)
{
  /* XXX We cannot translate these messages.  */
  static const char msg[2][32] = { "unexpected reloc type",
				   "unexpected PLT reloc type" };
  char msgbuf[sizeof (msg[0])];

  strcpy (msgbuf, msg[plt]);

  _dl_signal_error (0, map->l_name, NULL, msgbuf);
}