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elfinterp.c

/* Run an ELF binary on a linux system.

   Copyright (C) 1993, Eric Youngdale.

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

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#ifndef VERBOSE_DLINKER
#define VERBOSE_DLINKER
#endif
#ifdef VERBOSE_DLINKER
static char * _dl_reltypes[] = {"R_386_NONE","R_386_32","R_386_PC32","R_386_GOT32",
                   "R_386_PLT32","R_386_COPY","R_386_GLOB_DAT",
                   "R_386_JMP_SLOT","R_386_RELATIVE","R_386_GOTOFF",
                   "R_386_GOTPC","R_386_NUM"};
#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. */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/unistd.h>
/*#include <stdlib.h>*/
#include "string.h"
#ifdef IBCS_COMPATIBLE
#include <ibcs/unistd.h>
#else
#include <linux/unistd.h>
#endif
#include <linux/fcntl.h>
#include <linux/elf.h>

#include "hash.h"
#include "linuxelf.h"
#include "syscall.h"
#include "string.h"

#define SVR4_COMPATIBILITY

extern char *_dl_progname;

extern _dl_linux_resolve(void);

unsigned int _dl_linux_resolver(int dummy, int i)
{
  unsigned int * sp;
  int reloc_entry;
  int reloc_type;
  struct elf32_rel * this_reloc;
  char * strtab;
  struct elf32_sym * symtab; 
  struct elf32_rel * rel_addr;
  struct elf_resolve * tpnt;
  int symtab_index;
  char * new_addr;
  char ** got_addr;
  unsigned int instr_addr;
  sp = &i;  
  reloc_entry = sp[1];
  tpnt = (struct elf_resolve *) sp[0];

  rel_addr = (struct elf32_rel *) (tpnt->dynamic_info[DT_JMPREL] + 
                           tpnt->loadaddr);

  this_reloc = rel_addr + (reloc_entry >> 3);
  reloc_type = ELF32_R_TYPE(this_reloc->r_info);
  symtab_index = ELF32_R_SYM(this_reloc->r_info);

  symtab =  (struct elf32_sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
  strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);


  if (reloc_type != R_386_JMP_SLOT) {
    _dl_fdprintf(2, "%s: Incorrect relocation type in jump relocations\n",
             _dl_progname);
    _dl_exit(1);
  };

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

#ifdef DEBUG
  _dl_fdprintf(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, (int) got_addr, tpnt, 0);
  if(!new_addr) {
    _dl_fdprintf(2, "%s: can't resolve symbol '%s'\n",
             _dl_progname, strtab + symtab[symtab_index].st_name);
    _dl_exit(1);
  };
/* #define DEBUG_LIBRARY */
#ifdef DEBUG_LIBRARY
  if((unsigned int) got_addr < 0x40000000) {
    _dl_fdprintf(2, "Calling library function: %s\n",
             strtab + symtab[symtab_index].st_name);
  } else {
    *got_addr = new_addr;
  }
#else
  *got_addr = new_addr;
#endif
  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;
  struct elf32_sym * symtab; 
  struct elf32_rel * rpnt;
  unsigned int * reloc_addr;

  /* Now parse the relocation information */
  rpnt = (struct elf32_rel *) (rel_addr + tpnt->loadaddr);
  rel_size = rel_size / sizeof(struct elf32_rel);

  symtab =  (struct 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++, 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_386_NONE: break;
    case R_386_JMP_SLOT:
      *reloc_addr += (unsigned int) tpnt->loadaddr;
      break;
    default:
      _dl_fdprintf(2, "%s: (LAZY) can't handle reloc type ", _dl_progname);
#ifdef VERBOSE_DLINKER
      _dl_fdprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
      if(symtab_index) _dl_fdprintf(2, "'%s'\n",
                          strtab + symtab[symtab_index].st_name);
      _dl_exit(1);
    };
  };
}

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;
  struct elf32_sym * symtab; 
  struct elf32_rel * rpnt;
  unsigned int * reloc_addr;
  unsigned int symbol_addr;
  int symtab_index;
  /* Now parse the relocation information */

  rpnt = (struct elf32_rel *) (rel_addr + tpnt->loadaddr);
  rel_size = rel_size / sizeof(struct elf32_rel);

  symtab =  (struct 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++, 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, (int) reloc_addr, 
                  (reloc_type == R_386_JMP_SLOT ? tpnt : NULL), 0);

      /*
       * We want to allow undefined references to weak symbols - this might
       * have been intentional.  We should not be linking local symbols
       * here, so all bases should be covered.
       */
      if(!symbol_addr && 
       ELF32_ST_BIND(symtab[symtab_index].st_info) == STB_GLOBAL) {
      _dl_fdprintf(2, "%s: can't resolve symbol '%s'\n",
               _dl_progname, strtab + symtab[symtab_index].st_name);
      goof++;
      }
    }
    switch(reloc_type){
    case R_386_NONE:
      break;
    case R_386_32:
      *reloc_addr += symbol_addr;
      break;
    case R_386_PC32:
      *reloc_addr += symbol_addr - (unsigned int) reloc_addr;
      break;
    case R_386_GLOB_DAT:
    case R_386_JMP_SLOT:
      *reloc_addr = symbol_addr;
      break;
    case R_386_RELATIVE:
      *reloc_addr += (unsigned int) tpnt->loadaddr;
      break;
    case R_386_COPY:
#if 0  /* Do this later */
      _dl_fdprintf(2, "Doing copy for symbol ");
      if(symtab_index) _dl_fdprintf(2, strtab + symtab[symtab_index].st_name);
      _dl_fdprintf(2, "\n");
      _dl_memcpy((void *) symtab[symtab_index].st_value,
             (void *) symbol_addr, 
             symtab[symtab_index].st_size);
#endif
      break;
    default:
      _dl_fdprintf(2, "%s: can't handle reloc type ", _dl_progname);
#ifdef VERBOSE_DLINKER
      _dl_fdprintf(2, "%s ", _dl_reltypes[reloc_type]);
#endif
      if (symtab_index)
      _dl_fdprintf(2, "'%s'\n", strtab + symtab[symtab_index].st_name);
      _dl_exit(1);
    };

  };
  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 */

#ifndef BROKEN_LINKER
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;
  struct elf32_sym * symtab; 
  struct elf32_rel * 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 = (struct elf32_rel *) (rel_addr + tpnt->loadaddr);
  rel_size = rel_size / sizeof(struct elf32_rel);

  symtab =  (struct 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++, rpnt++){
    reloc_addr = (int *) (tpnt->loadaddr + (int)rpnt->r_offset);
    reloc_type = ELF32_R_TYPE(rpnt->r_info);
    if(reloc_type != R_386_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, (int) reloc_addr, NULL, 1);
      if(!symbol_addr) {
      _dl_fdprintf(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;
}
#endif



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