uclibc-ng/ldso/util/readelf2.c

char *readsonameXX(char *name, FILE *infile, int expected_type, int *type)
{
  ElfW(Ehdr) *epnt;
  ElfW(Phdr) *ppnt;
  int i, j;
  char *header;
  ElfW(Word) dynamic_addr = 0;
  ElfW(Word) dynamic_size = 0;
  unsigned long page_size = getpagesize();
  ElfW(Word) strtab_val = 0;
  ElfW(Word) needed_val;
  ElfW(Sword) loadaddr = -1;
  ElfW(Dyn) *dpnt;
  struct stat st;
  char *needed;
  char *soname = NULL;
  int multi_libcs = 0;

  if(expected_type == LIB_DLL)
    {
      warn("%s does not match type specified for directory!", name);
      expected_type = LIB_ANY;
    }

  *type = LIB_ELF;

  if (fstat(fileno(infile), &st))
    return NULL;
  header = mmap(0, st.st_size, PROT_READ, MAP_SHARED, fileno(infile), 0);
  if (header == (caddr_t)-1)
    return NULL;

  epnt = (ElfW(Ehdr) *)header;
  if ((char *)(epnt+1) > (char *)(header + st.st_size))
    goto skip;

  ppnt = (ElfW(Phdr) *)&header[epnt->e_phoff];
  if ((char *)ppnt < (char *)header ||
      (char *)(ppnt+epnt->e_phnum) > (char *)(header + st.st_size))
    goto skip;

  for(i = 0; i < epnt->e_phnum; i++)
  {
    if (loadaddr == -1 && ppnt->p_type == PT_LOAD) 
      loadaddr = (ppnt->p_vaddr & ~(page_size-1)) -
	(ppnt->p_offset & ~(page_size-1));
    if(ppnt->p_type == 2)
    {
      dynamic_addr = ppnt->p_offset;
      dynamic_size = ppnt->p_filesz;
    };
    ppnt++;
  };
    
  dpnt = (ElfW(Dyn) *) &header[dynamic_addr];
  dynamic_size = dynamic_size / sizeof(ElfW(Dyn));
  if ((char *)dpnt < (char *)header ||
      (char *)(dpnt+dynamic_size) > (char *)(header + st.st_size))
    goto skip;
  
  while (dpnt->d_tag != DT_NULL)
  {
    if (dpnt->d_tag == DT_STRTAB)
      strtab_val = dpnt->d_un.d_val;
    dpnt++;
  };

  if (!strtab_val)
    goto skip;

  dpnt = (ElfW(Dyn) *) &header[dynamic_addr];
  while (dpnt->d_tag != DT_NULL)
  {
    if (dpnt->d_tag == DT_SONAME || dpnt->d_tag == DT_NEEDED)
    {
      needed_val = dpnt->d_un.d_val;
      if (needed_val + strtab_val - loadaddr >= 0 ||
	  needed_val + strtab_val - loadaddr < st.st_size)
      {
	needed = (char *) (header - loadaddr + strtab_val + needed_val);

	if (dpnt->d_tag == DT_SONAME)
	  soname = xstrdup(needed);

	for (j = 0; needed_tab[j].soname != NULL; j++)
	{
	  if (strcmp(needed, needed_tab[j].soname) == 0)
	  {
	    if (*type != LIB_ELF && *type != needed_tab[j].type)
	      multi_libcs = 1;
	    *type = needed_tab[j].type;
	  }
	}
      }
    }
    dpnt++;
  };
  
  if (multi_libcs)
    warn("%s appears to be for multiple libc's", name);

  /* If we could not deduce the libc type, and we know what to expect, set the type */
  if(*type == LIB_ELF && expected_type != LIB_ANY) *type = expected_type;

  if(expected_type != LIB_ANY && expected_type != LIB_ELF && 
     expected_type != *type)
  {
      warn("%s does not match type specified for directory!", name);
  }

 skip:
  munmap(header, st.st_size);

  return soname;
}