/*
 * Copyright 2002  John W. De Boskey <jwd@FreeBSD.Org>
 * 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. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JOHN W. DE BOSKEY ``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 JOHN W. DE BOSKEY 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.
 *
 */

#include <sys/types.h>
#include <elf.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include "elfutil.h"

void
open_elf_image(filename,fdp,filebufp)
char  *filename;
int   *fdp;
char **filebufp;
{
   int   fd;
   int   rc;
   char *filebuf;
   struct stat sb;
   Elf32_Ehdr *eh;


   fd = open(filename, O_RDONLY);
   if (fd < 0)
      err(1,"open(\"%s\")",filename);

   rc = fstat(fd, &sb);
   if (rc < 0)
      err(1,"fstat()");
   filebuf = mmap(0, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
   if (filebuf == MAP_FAILED)
      err(1,"mmap()");

   eh = (Elf32_Ehdr *)filebuf;
   if (eh->e_ident[EI_MAG1] != 'E' ||
       eh->e_ident[EI_MAG2] != 'L' ||
       eh->e_ident[EI_MAG3] != 'F') {
      fprintf(stderr,"%s is not an ELF format image\n",filename);
      exit(1);
   }

   *fdp = fd;
   *filebufp = filebuf;

   return;
}

/*
 * Given a pointer to an elf object, find the interpreter
 */
char *
get_elf_interp(elf)
char *elf;
{
   Elf32_Ehdr *eh = (Elf32_Ehdr *)elf;
   Elf32_Shdr *sh = (Elf32_Shdr *)&elf[eh->e_shoff];
   Elf32_Shdr *si = &sh[eh->e_shstrndx];
   char *shstrtab = &elf[si->sh_offset];
   char *interp = NULL;
   int i;

   for (i=1; i<eh->e_shnum; i++)
      if (!strcmp(&shstrtab[sh[i].sh_name], ".interp")) {
         interp = &elf[sh[i].sh_offset];
         break;
      }

   if (interp)
      return(strdup(interp));
   return(interp);
}


/*
 * Locate a function within an elf section table
 */
unsigned
get_function_offset(elf,table,func)
char *elf;
char *table;
char *func;
{
   Elf32_Ehdr *eh = (Elf32_Ehdr *)elf;
   Elf32_Shdr *sh = (Elf32_Shdr *)&elf[eh->e_shoff];
   Elf32_Shdr *si = &sh[eh->e_shstrndx];
   char *shstrtab = &elf[si->sh_offset];
   Elf32_Sym  *st = NULL;
   int symcnt = NULL;
   char *strtab   = NULL;
   int  offset;

   int i;

   for (i=1; i<eh->e_shnum; i++)
      if (!strcmp(&shstrtab[sh[i].sh_name], table)) {
         st     = (Elf32_Sym *)&elf[sh[i].sh_offset];
         strtab = &elf[sh[sh[i].sh_link].sh_offset];
         symcnt = sh[i].sh_size / sh[i].sh_entsize;
         break;
      }

   if (!st) {
      fprintf(stderr,"Could not locate %s section\n",table);
      exit(1);
   }

   for (i=0; i<symcnt; i++) {
      if (!strcmp( &strtab[st[i].st_name], func)) {
         offset = st[i].st_value;
         break;
      }
   }

   if (!offset) {
      fprintf(stderr,"Could not locate %s in %s\n",func,table);
      exit(1);
   }

   return(offset);
}

/*
 * return the entry point of an elf object
 */
unsigned
get_image_entrypt(elf)
char *elf;
{
   Elf32_Ehdr *eh = (Elf32_Ehdr *)elf;

   return(eh->e_entry);
}


/*
 * Return information about the interpreter
 */

#define HOOKSECT ".dynsym"
#define HOOKNAME "r_debug_state"

void
get_interp_info(interp)
__interp *interp;
{
   int   fd;
   char *i_buf;

   open_elf_image(interp->name,&fd,&i_buf);

   interp->hookpt = get_function_offset(i_buf,HOOKSECT,HOOKNAME);
   if (! interp->hookpt) {
      fprintf(stderr,"[%s] not found in [%s]\n",HOOKNAME,HOOKSECT);
      exit(1);
   }

   interp->entrypt = get_image_entrypt(i_buf);
   if (! interp->entrypt) {
      fprintf(stderr,"Could not locate entrypt in %s\n",interp->name);
      exit(1);
   }

   return;
}