elfinterp.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* vi: set sw=4 ts=4: */
/* sparc ELF shared library loader suppport
 *
 * Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald, 
 *				David Engel, Hongjiu Lu and Mitch D'Souza
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. The name of the above contributors may not be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined (__SUPPORT_LD_DEBUG__)
static const char * _dl_reltypes[] = { "R_SPARC_NONE", "R_SPARC_8",
  "R_SPARC_16", "R_SPARC_32", "R_SPARC_DISP8", "R_SPARC_DISP16",
  "R_SPARC_DISP32", "R_SPARC_WDISP30", "R_SPARC_WDISP22",
  "R_SPARC_HI22", "R_SPARC_22", "R_SPARC_13", "R_SPARC_LO10",
  "R_SPARC_GOT10", "R_SPARC_GOT13", "R_SPARC_GOT22", "R_SPARC_PC10",
  "R_SPARC_PC22", "R_SPARC_WPLT30", "R_SPARC_COPY",
  "R_SPARC_GLOB_DAT", "R_SPARC_JMP_SLOT", "R_SPARC_RELATIVE",
  "R_SPARC_UA32"};
#endif

/* Program to load an ELF binary on a linux system, and run it.
References to symbols in sharable libraries can be resolved by either
an ELF sharable library or a linux style of shared library. */

/* Disclaimer:  I have never seen any AT&T source code for SVr4, nor have
   I ever taken any courses on internals.  This program was developed using
   information available through the book "UNIX SYSTEM V RELEASE 4,
   Programmers guide: Ansi C and Programming Support Tools", which did
   a more than adequate job of explaining everything required to get this
   working. */

extern _dl_linux_resolve(void);

unsigned int _dl_linux_resolver(unsigned int reloc_entry, unsigned int * plt)
{
  int reloc_type;
  Elf32_Rela * this_reloc;
  char * strtab;
  Elf32_Sym * symtab; 
  Elf32_Rela * rel_addr;
  struct elf_resolve * tpnt;
  int symtab_index;
  char * new_addr;
  char ** got_addr;
  unsigned int instr_addr;
  tpnt = (struct elf_resolve *) plt[2];

  rel_addr = (Elf32_Rela *) (tpnt->dynamic_info[DT_JMPREL] + 
				   tpnt->loadaddr);

  /*
   * Generate the correct relocation index into the .rela.plt section.
   */
  reloc_entry = (reloc_entry >> 12) - 0xc;

  this_reloc = (Elf32_Rela *) ((char *) rel_addr + reloc_entry);

  reloc_type = ELF32_R_TYPE(this_reloc->r_info);
  symtab_index = ELF32_R_SYM(this_reloc->r_info);

  symtab =  (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
  strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);

  _dl_dprintf(2, "tpnt = %x\n", tpnt);
  _dl_dprintf(2, "reloc = %x\n", this_reloc);
  _dl_dprintf(2, "symtab = %x\n", symtab);
  _dl_dprintf(2, "strtab = %x\n", strtab);


  if (reloc_type != R_SPARC_JMP_SLOT) {
    _dl_dprintf(2, "%s: incorrect relocation type in jump relocations (%d)\n",
		  _dl_progname, reloc_type);
    _dl_exit(30);
  };

  /* Address of jump instruction to fix up */
  instr_addr  = ((int)this_reloc->r_offset  + (int)tpnt->loadaddr);
  got_addr = (char **) instr_addr;

  _dl_dprintf(2, "symtab_index %d\n", symtab_index);

#ifdef __SUPPORT_LD_DEBUG__
  if (_dl_debug_symbols) {
	  _dl_dprintf(2, "Resolving symbol %s\n",
			  strtab + symtab[symtab_index].st_name);
  }
#endif

  /* Get the address of the GOT entry */
  new_addr = _dl_find_hash(strtab + symtab[symtab_index].st_name, 
  			tpnt->symbol_scope, tpnt, resolver);
  if(!new_addr) {
    _dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
	       _dl_progname, strtab + symtab[symtab_index].st_name);
    _dl_exit(31);
  };

#if defined (__SUPPORT_LD_DEBUG__)
	if ((unsigned long) got_addr < 0x40000000)
	{
		if (_dl_debug_bindings)
		{
			_dl_dprintf(_dl_debug_file, "\nresolve function: %s",
					strtab + symtab[symtab_index].st_name);
			if(_dl_debug_detail) _dl_dprintf(_dl_debug_file, 
					"\tpatch %x ==> %x @ %x", *got_addr, new_addr, got_addr);
		}
	}
	if (!_dl_debug_nofixups) {
		got_addr[1] = (char *) (0x03000000 | (((unsigned int) new_addr >> 10) & 0x3fffff));
		got_addr[2] = (char *) (0x81c06000 | ((unsigned int) new_addr & 0x3ff));
	}
#else
	got_addr[1] = (char *) (0x03000000 | (((unsigned int) new_addr >> 10) & 0x3fffff));
	got_addr[2] = (char *) (0x81c06000 | ((unsigned int) new_addr & 0x3ff));
#endif

	_dl_dprintf(2, "Address = %x\n",new_addr);
	_dl_exit(32);

  return (unsigned int) new_addr;
}

void _dl_parse_lazy_relocation_information(struct elf_resolve * tpnt, int rel_addr,
       int rel_size, int type){
  int i;
  char * strtab;
  int reloc_type;
  int symtab_index;
  Elf32_Sym * symtab; 
  Elf32_Rela * rpnt;
  unsigned int * reloc_addr;

  /* Now parse the relocation information */
  rpnt = (Elf32_Rela *) (rel_addr + tpnt->loadaddr);

  symtab =  (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
  strtab = ( char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);

  for(i=0; i< rel_size; i += sizeof(Elf32_Rela), rpnt++){
    reloc_addr = (int *) (tpnt->loadaddr + (int)rpnt->r_offset);
    reloc_type = ELF32_R_TYPE(rpnt->r_info);
    symtab_index = ELF32_R_SYM(rpnt->r_info);

    /* When the dynamic linker bootstrapped itself, it resolved some symbols.
       Make sure we do not do them again */
    if(!symtab_index && tpnt->libtype == program_interpreter) continue;
    if(symtab_index && tpnt->libtype == program_interpreter &&
       _dl_symbol(strtab + symtab[symtab_index].st_name))
      continue;

    switch(reloc_type){
    case R_SPARC_NONE:
      break;
    case R_SPARC_JMP_SLOT:
      break;
    default:
      _dl_dprintf(2, "%s: (LAZY) can't handle reloc type ", _dl_progname);
#if defined (__SUPPORT_LD_DEBUG__)
      _dl_dprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
      if(symtab_index) _dl_dprintf(2, "'%s'\n",
				  strtab + symtab[symtab_index].st_name);
      _dl_exit(33);
    };
  };
}

int _dl_parse_relocation_information(struct elf_resolve * tpnt, int rel_addr,
       int rel_size, int type){
  int i;
  char * strtab;
  int reloc_type;
  int goof = 0;
  Elf32_Sym * symtab; 
  Elf32_Rela * rpnt;
  unsigned int * reloc_addr;
  unsigned int symbol_addr;
  int symtab_index;
  /* Now parse the relocation information */

  rpnt = (Elf32_Rela *) (rel_addr + tpnt->loadaddr);

  symtab =  (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
  strtab = ( char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);

  for(i=0; i< rel_size; i+= sizeof(Elf32_Rela), rpnt++){
    reloc_addr = (int *) (tpnt->loadaddr + (int)rpnt->r_offset);
    reloc_type = ELF32_R_TYPE(rpnt->r_info);
    symtab_index = ELF32_R_SYM(rpnt->r_info);
    symbol_addr = 0;

    if(!symtab_index && tpnt->libtype == program_interpreter) continue;

    if(symtab_index) {

      if(tpnt->libtype == program_interpreter && 
	 _dl_symbol(strtab + symtab[symtab_index].st_name))
	continue;

      symbol_addr = (unsigned int) 
	_dl_find_hash(strtab + symtab[symtab_index].st_name,
			      tpnt->symbol_scope,
		      (reloc_type == R_SPARC_JMP_SLOT ? tpnt : NULL), symbolrel);

      if(!symbol_addr &&
	 ELF32_ST_BIND(symtab [symtab_index].st_info) == STB_GLOBAL) {
	_dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
		     _dl_progname, strtab + symtab[symtab_index].st_name);
	goof++;
      };
    };
    switch(reloc_type){
    case R_SPARC_NONE:
	break;
    case R_SPARC_32:
      *reloc_addr = symbol_addr + rpnt->r_addend;
      break;
    case R_SPARC_DISP32:
      *reloc_addr = symbol_addr + rpnt->r_addend - (unsigned int) reloc_addr;
      break;
    case R_SPARC_GLOB_DAT:
      *reloc_addr = symbol_addr + rpnt->r_addend;
      break;
    case R_SPARC_JMP_SLOT:
      reloc_addr[1] = 0x03000000 | ((symbol_addr >> 10) & 0x3fffff);
      reloc_addr[2] = 0x81c06000 | (symbol_addr & 0x3ff);
      break;
    case R_SPARC_RELATIVE:
      *reloc_addr += (unsigned int) tpnt->loadaddr + rpnt->r_addend;
      break;
    case R_SPARC_HI22:
      if (!symbol_addr)
        symbol_addr = tpnt->loadaddr + rpnt->r_addend;
      else
	symbol_addr += rpnt->r_addend;
      *reloc_addr = (*reloc_addr & 0xffc00000)|(symbol_addr >> 10);
      break;
    case R_SPARC_LO10:
      if (!symbol_addr)
        symbol_addr = tpnt->loadaddr + rpnt->r_addend;
      else
	symbol_addr += rpnt->r_addend;
      *reloc_addr = (*reloc_addr & ~0x3ff)|(symbol_addr & 0x3ff);
      break;
    case R_SPARC_WDISP30:
      *reloc_addr = (*reloc_addr & 0xc0000000)|
	((symbol_addr - (unsigned int) reloc_addr) >> 2);
      break;
    case R_SPARC_COPY:
#if 0 /* This one is done later */
      _dl_dprintf(2, "Doing copy for symbol ");
      if(symtab_index) _dl_dprintf(2, strtab + symtab[symtab_index].st_name);
      _dl_dprintf(2, "\n");
      _dl_memcpy((void *) symtab[symtab_index].st_value,
		 (void *) symbol_addr, 
		 symtab[symtab_index].st_size);
#endif
      break;
    default:
      _dl_dprintf(2, "%s: can't handle reloc type ", _dl_progname);
#if defined (__SUPPORT_LD_DEBUG__)
      _dl_dprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
      if (symtab_index)
	_dl_dprintf(2, "'%s'\n", strtab + symtab[symtab_index].st_name);
      _dl_exit(34);
    };

  };
  return goof;
}


/* This is done as a separate step, because there are cases where
   information is first copied and later initialized.  This results in
   the wrong information being copied.  Someone at Sun was complaining about
   a bug in the handling of _COPY by SVr4, and this may in fact be what he
   was talking about.  Sigh. */

/* No, there are cases where the SVr4 linker fails to emit COPY relocs
   at all */

int _dl_parse_copy_information(struct dyn_elf * xpnt, int rel_addr,
       int rel_size, int type)
{
  int i;
  char * strtab;
  int reloc_type;
  int goof = 0;
  Elf32_Sym * symtab; 
  Elf32_Rela * rpnt;
  unsigned int * reloc_addr;
  unsigned int symbol_addr;
  struct elf_resolve *tpnt;
  int symtab_index;
  /* Now parse the relocation information */

  tpnt = xpnt->dyn;
  
  rpnt = (Elf32_Rela *) (rel_addr + tpnt->loadaddr);

  symtab =  (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
  strtab = ( char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);

  for(i=0; i< rel_size; i+= sizeof(Elf32_Rela), rpnt++){
    reloc_addr = (int *) (tpnt->loadaddr + (int)rpnt->r_offset);
    reloc_type = ELF32_R_TYPE(rpnt->r_info);
    if(reloc_type != R_SPARC_COPY) continue;
    symtab_index = ELF32_R_SYM(rpnt->r_info);
    symbol_addr = 0;
    if(!symtab_index && tpnt->libtype == program_interpreter) continue;
    if(symtab_index) {

      if(tpnt->libtype == program_interpreter && 
	 _dl_symbol(strtab + symtab[symtab_index].st_name))
	continue;

      symbol_addr = (unsigned int) 
	_dl_find_hash(strtab + symtab[symtab_index].st_name,
			      xpnt->next, NULL, copyrel);
      if(!symbol_addr) {
	_dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
		   _dl_progname, strtab + symtab[symtab_index].st_name);
	goof++;
      };
    };
    if (!goof)
      _dl_memcpy((char *) symtab[symtab_index].st_value, 
		  (char *) symbol_addr, 
		  symtab[symtab_index].st_size);
  };
  return goof;
}