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readelflib1.c

/* Load an ELF sharable library into memory.

   Copyright (C) 1993-1996, 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.  */



/* This file contains the helper routines to load an ELF sharable
   library into memory and add the symbol table info to the chain. */

#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/errno.h>
#include "string.h"
/*#include <stdlib.h>*/
#include <linux/mman.h>
#include <linux/stat.h>
#include "hash.h"
#include "linuxelf.h"
#include "sysdep.h"
#ifdef IBCS_COMPATIBLE
#include <ibcs/unistd.h>
#else
#include <linux/unistd.h>
#endif
#include "syscall.h"
#ifdef USE_CACHE
#include "../config.h"
#endif

extern char *_dl_progname;

#ifdef USE_CACHE

static caddr_t _dl_cache_addr = NULL;
static size_t _dl_cache_size = 0;

int _dl_map_cache(void)
{
  int fd;
  struct stat st;
  header_t *header;
  libentry_t *libent;
  int i, strtabsize;

  if (_dl_cache_addr == (caddr_t)-1)
    return -1;
  else if (_dl_cache_addr != NULL)
    return 0;

  if (_dl_stat(LDSO_CACHE, &st) || (fd = _dl_open(LDSO_CACHE, O_RDONLY)) < 0)
  {
    _dl_fdprintf(2, "%s: can't open cache '%s'\n", _dl_progname, LDSO_CACHE);
    _dl_cache_addr = (caddr_t)-1; /* so we won't try again */
    return -1;
  }

  _dl_cache_size = st.st_size;
  _dl_cache_addr = (caddr_t)_dl_mmap(0, _dl_cache_size, PROT_READ,
                             MAP_SHARED, fd, 0);
  _dl_close (fd);
  if (_dl_cache_addr == (caddr_t)-1)
  {
    _dl_fdprintf(2, "%s: can't map cache '%s'\n", _dl_progname, LDSO_CACHE);
    return -1;
  }

  header = (header_t *)_dl_cache_addr;

  if (_dl_cache_size < sizeof (header_t) ||
      _dl_memcmp(header->magic, LDSO_CACHE_MAGIC, LDSO_CACHE_MAGIC_LEN) ||
      _dl_memcmp(header->version, LDSO_CACHE_VER, LDSO_CACHE_VER_LEN) ||
      _dl_cache_size < 
        (sizeof (header_t) + header->nlibs * sizeof (libentry_t)) ||
      _dl_cache_addr[_dl_cache_size-1] != '\0')
  {
    _dl_fdprintf(2, "%s: cache '%s' is corrupt\n", _dl_progname, LDSO_CACHE);
    goto fail;
  }

  strtabsize = _dl_cache_size - sizeof (header_t) - 
    header->nlibs * sizeof (libentry_t);
  libent = (libentry_t *)&header[1];

  for (i = 0; i < header->nlibs; i++)
  {
    if (libent[i].sooffset >= strtabsize ||
      libent[i].liboffset >= strtabsize)
    {
      _dl_fdprintf(2, "%s: cache '%s' is corrupt\n", _dl_progname, LDSO_CACHE);
      goto fail;
    }
  }

  return 0;

fail:
  _dl_munmap(_dl_cache_addr, _dl_cache_size);
  _dl_cache_addr = (caddr_t)-1;
  return -1;
}

int _dl_unmap_cache(void)
{
  if (_dl_cache_addr == NULL || _dl_cache_addr == (caddr_t)-1)
    return -1;

#if 1
  _dl_munmap (_dl_cache_addr, _dl_cache_size);
  _dl_cache_addr = NULL;
#endif

  return 0;
}

#endif

/*
 * Used to return error codes back to dlopen et. al.
 */

unsigned int _dl_error_number;
unsigned int _dl_internal_error_number;

struct elf_resolve * _dl_load_shared_library(int secure, 
      struct elf_resolve * tpnt, char * full_libname) {
  char * pnt, *pnt1, *pnt2;
  struct elf_resolve *tpnt1 = NULL;
  char mylibname[2050];
  char * libname;

  _dl_internal_error_number = 0;

  /* quick hack to ensure mylibname buffer doesn't overflow.  don't 
     allow full_libname or any directory to be longer than 1024. */
  if (_dl_strlen(full_libname) > 1024)
    goto goof;

  pnt = libname = full_libname;
  while (*pnt) {
    if(*pnt == '/') libname = pnt+1;
    pnt++;
  }

 /* If the filename has any '/', try it straight and leave it at that.
     For IBCS2 compatibility under linux, we substitute the string 
     /usr/i486-sysv4/lib for /usr/lib in library names. */

  if (libname != full_libname) {
#ifdef IBCS_COMPATIBLE
    if (_dl_strncmp(full_libname, "/usr/lib/", 9) != 0) {
      tpnt1 = _dl_load_elf_shared_library(secure, full_libname, 0);
    } else {
      pnt1 = "/usr/i486-sysv4/lib/";
      pnt = mylibname;
      while(*pnt1) *pnt++ = *pnt1++;
      pnt1 = full_libname + 9;
      while(*pnt1) *pnt++ = *pnt1++;
      *pnt++ = 0;
      tpnt1 = _dl_load_elf_shared_library(secure, mylibname, 0);
    }
#else
    tpnt1 = _dl_load_elf_shared_library(secure, full_libname, 0);
#endif
    if (tpnt1)
      return tpnt1;
    goto goof;
  }

  /*
   * The ABI specifies that RPATH is searched before LD_*_PATH or
   * the default path of /usr/lib.
   * Check in rpath directories 
   */
  for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
    if (tpnt->libtype == elf_executable) {
      pnt1 = (char *)tpnt->dynamic_info[DT_RPATH];
      if(pnt1) {
      pnt1 += (unsigned int) tpnt->loadaddr + tpnt->dynamic_info[DT_STRTAB];
      while(*pnt1){
        pnt2 = mylibname;
        while(*pnt1 && *pnt1 != ':') {
          if (pnt2 - mylibname < 1024)
            *pnt2++ = *pnt1++;
          else
            pnt1++;
        }
        if (pnt2 - mylibname >= 1024)
          break;
        if(pnt2[-1] != '/') *pnt2++ = '/';
        pnt = libname;
        while(*pnt) *pnt2++  = *pnt++;
        *pnt2++ = 0;
        tpnt1 = _dl_load_elf_shared_library(secure, mylibname, 0);
        if(tpnt1) return tpnt1;
        if(*pnt1 == ':') pnt1++;
      }
      }
    }
  }
  

  /* Check in LD_{ELF_}LIBRARY_PATH, if specified and allowed */
  pnt1 = _dl_library_path;
  if (pnt1 && *pnt1) {
    while (*pnt1) {
      pnt2 = mylibname;
      while(*pnt1 && *pnt1 != ':' && *pnt1 != ';') {
      if (pnt2 - mylibname < 1024)
        *pnt2++ = *pnt1++;
      else
        pnt1++;
      }
      if (pnt2 - mylibname >= 1024)
      break;
      if(pnt2[-1] != '/') *pnt2++ = '/';
      pnt = libname;
      while(*pnt) *pnt2++  = *pnt++;
      *pnt2++ = 0;
      tpnt1 = _dl_load_elf_shared_library(secure, mylibname, 0);
      if(tpnt1) return tpnt1;
      if(*pnt1 == ':' || *pnt1 == ';') pnt1++;
    }
  }


  /*
   * Where should the cache be searched?  There is no such concept in the
   * ABI, so we have some flexibility here.  For now, search it before
   * the default path of /usr/lib.
   */
#ifdef USE_CACHE
  if (_dl_cache_addr != NULL && _dl_cache_addr != (caddr_t)-1)
  {
    int i;
    header_t *header = (header_t *)_dl_cache_addr;
    libentry_t *libent = (libentry_t *)&header[1];
    char *strs = (char *)&libent[header->nlibs];

    for (i = 0; i < header->nlibs; i++)
    {
      if ((libent[i].flags == LIB_ELF || 
         libent[i].flags == LIB_ELF_LIBC5) &&
        _dl_strcmp(libname, strs+libent[i].sooffset) == 0 &&
        (tpnt1 = _dl_load_elf_shared_library(secure, strs+libent[i].liboffset, 0)))
      return tpnt1;
    }
  }
#endif

  /* Check in /usr/lib */
#ifdef IBCS_COMPATIBLE
  pnt1 = "/usr/i486-sysv4/lib/";
#else
  pnt1 = "/usr/lib/";
#endif
  pnt = mylibname;
  while(*pnt1) *pnt++ = *pnt1++;
  pnt1 = libname;
  while(*pnt1) *pnt++ = *pnt1++;
  *pnt++ = 0;
  tpnt1 = _dl_load_elf_shared_library(secure, mylibname, 0);
  if (tpnt1) return tpnt1;
  
#ifndef IBCS_COMPATIBLE
  /* Check in /lib */
  /* try "/lib/". */
  pnt1 = "/lib/";
  pnt = mylibname;
  while(*pnt1) *pnt++ = *pnt1++;
  pnt1 = libname;
  while(*pnt1) *pnt++ = *pnt1++;
  *pnt++ = 0;
  tpnt1 = _dl_load_elf_shared_library(secure, mylibname, 0);
  if (tpnt1) return tpnt1;
#endif

goof:
  /* Well, we shot our wad on that one.  All we can do now is punt */
  if (_dl_internal_error_number) _dl_error_number = _dl_internal_error_number;
      else _dl_error_number = DL_ERROR_NOFILE;
  return NULL;
}

/*
 * Read one ELF library into memory, mmap it into the correct locations and
 * add the symbol info to the symbol chain.  Perform any relocations that
 * are required.
 */

extern _elf_rtbndr(void);

struct elf_resolve * _dl_load_elf_shared_library(int secure, 
        char * libname, int flag) {
  struct elfhdr * epnt;
  unsigned int dynamic_addr = 0;
  unsigned int dynamic_size = 0;
  struct dynamic * dpnt;
  struct elf_resolve * tpnt;
  struct elf_phdr * ppnt;
  int piclib;
  char * status;
  int flags;
  char header[4096];
  int dynamic_info[24];
  int * lpnt;
  unsigned int libaddr;
  unsigned int minvma=0xffffffff, maxvma=0;
  
  int i;
  int infile;

  /* If this file is already loaded, skip this step */
  tpnt = _dl_check_hashed_files(libname);
  if(tpnt) return tpnt;

  /* If we are in secure mode (i.e. a setu/gid binary using LD_PRELOAD),
     we don't load the library if it isn't setuid. */

  if (secure) {
    struct stat st;
    if (_dl_stat(libname, &st) || !(st.st_mode & S_ISUID))
      return NULL;
  }

  libaddr = 0;
  infile = _dl_open(libname, O_RDONLY);
  if(infile < 0)
  {
#if 0
    /*
     * NO!  When we open shared libraries we may search several paths.
     * it is inappropriate to generate an error here.
     */
    _dl_fdprintf(2, "%s: can't open '%s'\n", _dl_progname, libname);
#endif
    _dl_internal_error_number = DL_ERROR_NOFILE;
    return NULL;
  }
 
  _dl_read(infile, header, sizeof(header));
  epnt = (struct elfhdr *) header;
  if (epnt->e_ident[0] != 0x7f ||
      epnt->e_ident[1] != 'E' ||
      epnt->e_ident[2] != 'L' ||
      epnt->e_ident[3] != 'F') {
    _dl_fdprintf(2, "%s: '%s' is not an ELF file\n", _dl_progname, libname);
    _dl_internal_error_number = DL_ERROR_NOTELF;
    _dl_close(infile);
    return NULL;
  };
  
  if((epnt->e_type != ET_DYN) || 
     (epnt->e_machine != MAGIC1 
#ifdef MAGIC2
      && epnt->e_machine != MAGIC2
#endif
      )){
    _dl_internal_error_number = (epnt->e_type != ET_DYN ? DL_ERROR_NOTDYN : DL_ERROR_NOTMAGIC);
    _dl_fdprintf(2, "%s: '%s' is not an ELF executable for " ELF_TARGET "\n",
             _dl_progname, libname);
    _dl_close(infile);
    return NULL;
  };

  ppnt = (struct elf_phdr *) &header[epnt->e_phoff];

  piclib = 1;
  for(i=0;i < epnt->e_phnum; i++){

    if(ppnt->p_type == PT_DYNAMIC) {
      if (dynamic_addr)
      _dl_fdprintf(2, "%s: '%s' has more than one dynamic section\n",
                 _dl_progname, libname);
      dynamic_addr = ppnt->p_vaddr;
      dynamic_size = ppnt->p_filesz;
    };

    if(ppnt->p_type == PT_LOAD) {
      /* See if this is a PIC library. */
      if(i == 0 && ppnt->p_vaddr > 0x1000000) {
          piclib = 0;
          minvma=ppnt->p_vaddr;
      }
      if(piclib && ppnt->p_vaddr < minvma) {
          minvma = ppnt->p_vaddr;
      }
      if(((unsigned int)ppnt->p_vaddr + ppnt->p_memsz) > maxvma) {
          maxvma = ppnt->p_vaddr + ppnt->p_memsz;
      }
     }
    ppnt++;
  };

  maxvma=(maxvma+0xfffU)&~0xfffU;
  minvma=minvma&~0xffffU;
  
  flags = MAP_PRIVATE /*| MAP_DENYWRITE*/;
  if(!piclib) flags |= MAP_FIXED;
  
  status = (char *) _dl_mmap((char *) (piclib?0:minvma),
                    maxvma-minvma, 
                    PROT_NONE, 
                    flags | MAP_ANONYMOUS, -1,
                    0);
  if(_dl_mmap_check_error(status)) {
    _dl_fdprintf(2, "%s: can't map '/dev/zero'\n", _dl_progname);
    _dl_internal_error_number = DL_ERROR_MMAP_FAILED;
    _dl_close(infile);
     return NULL;
  };
  libaddr=(unsigned int)status;
  flags|=MAP_FIXED;

  /* Get the memory to store the library */
  ppnt = (struct elf_phdr *) &header[epnt->e_phoff];
  
  for(i=0;i < epnt->e_phnum; i++){
    if(ppnt->p_type == PT_LOAD) {

      /* See if this is a PIC library. */
      if(i == 0 && ppnt->p_vaddr > 0x1000000) {
      piclib = 0;
      /* flags |= MAP_FIXED; */
      }


      
      if(ppnt->p_flags & PF_W) {
      unsigned int map_size;
      char * cpnt;
      
      status = (char *) _dl_mmap((char *) ((piclib?libaddr:0)  +
                                   (ppnt->p_vaddr & 0xfffff000)),
                    (ppnt->p_vaddr & 0xfff) + ppnt->p_filesz, 
                    LXFLAGS(ppnt->p_flags), 
                    flags, infile,
                    ppnt->p_offset & 0x7ffff000);
      
      if(_dl_mmap_check_error(status)) {
          _dl_fdprintf(2, "%s: can't map '%s'\n", _dl_progname, libname);
          _dl_internal_error_number = DL_ERROR_MMAP_FAILED;
          _dl_munmap((char *)libaddr, maxvma-minvma);
          _dl_close(infile);
          return NULL;
      };
      
      /* Pad the last page with zeroes. */
      cpnt =(char *) (status + (ppnt->p_vaddr & 0xfff) + ppnt->p_filesz);
      while(((unsigned int) cpnt) & 0xfff) *cpnt++ = 0;

/* I am not quite sure if this is completely correct to do or not, but
   the basic way that we handle bss segments is that we mmap /dev/zero if
   there are any pages left over that are not mapped as part of the file */

      map_size = (ppnt->p_vaddr + ppnt->p_filesz + 0xfff) & 0xfffff000;
      if(map_size < ppnt->p_vaddr + ppnt->p_memsz)
        status = (char *) _dl_mmap((char *) map_size + (piclib?libaddr:0), 
                      ppnt->p_vaddr + ppnt->p_memsz - map_size,
                      LXFLAGS(ppnt->p_flags),
                      flags | MAP_ANONYMOUS, -1, 0);
      } else
      status = (char *) _dl_mmap((char *) (ppnt->p_vaddr & 0xfffff000) + 
                           (piclib?libaddr:0), 
                    (ppnt->p_vaddr & 0xfff) + ppnt->p_filesz, 
                    LXFLAGS(ppnt->p_flags), 
                    flags, infile, 
                    ppnt->p_offset & 0x7ffff000);
      if(_dl_mmap_check_error(status)) {
      _dl_fdprintf(2, "%s: can't map '%s'\n", _dl_progname, libname);
      _dl_internal_error_number = DL_ERROR_MMAP_FAILED;
      _dl_munmap((char *)libaddr, maxvma-minvma);
      _dl_close(infile);
      return NULL;
      };

      /* if(libaddr == 0 && piclib) {
      libaddr = (unsigned int) status;
      flags |= MAP_FIXED;
      }; */
    };
    ppnt++;
  };
  _dl_close(infile);
  
  /* For a non-PIC library, the addresses are all absolute */
  if(piclib) {
    dynamic_addr += (unsigned int) libaddr;
  }

 /* 
  * OK, the ELF library is now loaded into VM in the correct locations
  * The next step is to go through and do the dynamic linking (if needed).
  */
  
  /* Start by scanning the dynamic section to get all of the pointers */
  
  if(!dynamic_addr) {
    _dl_internal_error_number = DL_ERROR_NODYNAMIC;
    _dl_fdprintf(2, "%s: '%s' is missing a dynamic section\n", _dl_progname, libname);
    return NULL;
  }

  dpnt = (struct dynamic *) dynamic_addr;

  dynamic_size = dynamic_size / sizeof(struct dynamic);
  _dl_memset(dynamic_info, 0, sizeof(dynamic_info));
  for(i=0; i< dynamic_size; i++){
    if( dpnt->d_tag > DT_JMPREL ) {dpnt++; continue; }
    dynamic_info[dpnt->d_tag] = dpnt->d_un.d_val;
    if(dpnt->d_tag == DT_TEXTREL ||
       SVR4_BUGCOMPAT) dynamic_info[DT_TEXTREL] = 1;
    dpnt++;
  };

  /* If the TEXTREL is set, this means that we need to make the pages
     writable before we perform relocations.  Do this now. They get set back
     again later. */

  if (dynamic_info[DT_TEXTREL]) {
  ppnt = (struct elf_phdr *) &header[epnt->e_phoff];
  for(i=0;i < epnt->e_phnum; i++, ppnt++){
    if(ppnt->p_type == PT_LOAD && !(ppnt->p_flags & PF_W))
      _dl_mprotect((void *) ((piclib?libaddr:0) + (ppnt->p_vaddr & 0xfffff000)),
               (ppnt->p_vaddr & 0xfff) + (unsigned int) ppnt->p_filesz,
               PROT_READ | PROT_WRITE | PROT_EXEC);
  }
  }


  tpnt = _dl_add_elf_hash_table(libname, (char *) libaddr, dynamic_info, dynamic_addr, 
                        dynamic_size);

  tpnt->ppnt = (struct elf_phdr *) (tpnt->loadaddr + epnt->e_phoff);
  tpnt->n_phent = epnt->e_phnum;

  /*
   * OK, the next thing we need to do is to insert the dynamic linker into
   * the proper entry in the GOT so that the PLT symbols can be properly
   * resolved. 
   */
  
  lpnt = (int *) dynamic_info[DT_PLTGOT];
  
  if(lpnt) {
    lpnt = (int *) (dynamic_info[DT_PLTGOT] + ((int) libaddr));
    INIT_GOT(lpnt, tpnt);
  };
  
  return tpnt;
}

/* Ugly, ugly.  Some versions of the SVr4 linker fail to generate COPY
   relocations for global variables that are present both in the image and
   the shared library.  Go through and do it manually.  If the images
   are guaranteed to be generated by a trustworthy linker, then this
   step can be skipped. */

int _dl_copy_fixups(struct dyn_elf * rpnt)
{
  int goof = 0;
  struct elf_resolve * tpnt;
#ifdef BROKEN_LINKER
  int hn, hn1, si, si1;
  unsigned int elf_hash_number;
  struct elf_resolve * tpnt1;
  struct dyn_elf * rpnt1;
  char * strtab, *strtab1;
  struct Elf32_Sym * symtab, *symtab1;
  char * pnt, *pnt1;
#endif

  if(rpnt->next) goof += _dl_copy_fixups(rpnt->next);
  else return 0;

  tpnt = rpnt->dyn;
      
  if (tpnt->init_flag & COPY_RELOCS_DONE) return goof;
  tpnt->init_flag |= COPY_RELOCS_DONE;
  
/* Use BROKEN_LINKER if the SVr4 linker is being used. */
#ifndef BROKEN_LINKER
#ifdef ELF_USES_RELOCA
  goof += _dl_parse_copy_information(rpnt, tpnt->dynamic_info[DT_RELA],
                                 tpnt->dynamic_info[DT_RELASZ], 0);

#else
  goof += _dl_parse_copy_information(rpnt, tpnt->dynamic_info[DT_REL],
                                 tpnt->dynamic_info[DT_RELSZ], 0);

#endif
#else
  /* OK, now scan the symbol table for this module */

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

  for(hn = 0; hn < tpnt->nbucket; hn++) {
    if(!tpnt->elf_buckets[hn]) continue;
    for(si = tpnt->elf_buckets[hn]; si; si = tpnt->chains[si]) {
      if(ELF32_ST_TYPE(symtab[si].st_info) != STT_OBJECT) continue;
      if(ELF32_ST_BIND(symtab[si].st_info) != STB_GLOBAL) continue; 
      if(symtab[si].st_value == 0 || symtab[si].st_shndx == 0) continue;
      if(!symtab[si].st_size) continue;
      pnt = strtab + symtab[si].st_name;

      elf_hash_number = _dl_elf_hash(pnt);

      /* OK, we have a candidate.  Now search for the same symbol in other
       libraries.  The hash number will be the same. */
      for(rpnt1 = rpnt->next; rpnt1; rpnt1 = rpnt1->next)
      {
        tpnt1 = rpnt1->dyn;
        hn1 = elf_hash_number % tpnt1->nbucket;
        if(!tpnt1->elf_buckets[hn1]) continue;

        symtab1 = (struct Elf32_Sym *) (tpnt1->dynamic_info[DT_SYMTAB] + 
                               tpnt1->loadaddr);
        strtab1 = (char *) (tpnt1->dynamic_info[DT_STRTAB] + tpnt1->loadaddr);
        for(si1 = tpnt1->elf_buckets[hn1]; si1; si1 = tpnt1->chains[si1]) {
          pnt1 = strtab1 + symtab1[si1].st_name;
          if(ELF32_ST_TYPE(symtab1[si1].st_info) != STT_OBJECT) continue;
          if(ELF32_ST_BIND(symtab1[si1].st_info) != STB_GLOBAL) continue; 
          if(symtab1[si1].st_value == 0 || symtab1[si1].st_shndx == 0) continue;
          if(!symtab1[si1].st_size) continue;
          if(symtab1[si1].st_size != symtab[si].st_size) continue;
          pnt1 = strtab1 + symtab1[si1].st_name;
          if(_dl_strcmp(pnt, pnt1) == 0) {
            char * to, *from;
            int count;
            to = tpnt->loadaddr + symtab[si].st_value;
            from = tpnt1->loadaddr + symtab1[si1].st_value;
            count = symtab[si].st_size;
            while(count--) *to++ = *from++;
            /* Cannot use memcpy - SVr4 assembler complains about dup label*/
#if 0
            _dl_fdprintf(2, "Global symbol in %s %s\n", tpnt1->libname, pnt);
#endif
          };
        };
      };
    };
  };
#endif
  return goof;
}


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