/*

 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "salibelf.h"

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

extern void print_debug(const char*,...);

// ELF file parsing helpers. Note that we do *not* use libelf here.

int read_elf_header(int fd, ELF_EHDR* ehdr) {

   if (pread(fd, ehdr, sizeof (ELF_EHDR), 0) != sizeof (ELF_EHDR) ||

            memcmp(&ehdr->e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||

            ehdr->e_version != EV_CURRENT) {

        return 0;

   }

   return 1;

}

bool is_elf_file(int fd) {

   ELF_EHDR ehdr;

   return read_elf_header(fd, &ehdr);

}

// read program header table of an ELF file

ELF_PHDR* read_program_header_table(int fd, ELF_EHDR* hdr) {

   ELF_PHDR* phbuf = 0;

   // allocate memory for program header table

   size_t nbytes = hdr->e_phnum * hdr->e_phentsize;

   if ((phbuf = (ELF_PHDR*) malloc(nbytes)) == NULL) {

      print_debug("can't allocate memory for reading program header table\n");

      return NULL;

   }

   if (pread(fd, phbuf, nbytes, hdr->e_phoff) != nbytes) {

      print_debug("ELF file is truncated! can't read program header table\n");

      free(phbuf);

      return NULL;

   }

   return phbuf;

}

// read section header table of an ELF file

ELF_SHDR* read_section_header_table(int fd, ELF_EHDR* hdr) {

   ELF_SHDR* shbuf = 0;

   // allocate memory for section header table

   size_t nbytes = hdr->e_shnum * hdr->e_shentsize;

   if ((shbuf = (ELF_SHDR*) malloc(nbytes)) == NULL) {

      print_debug("can't allocate memory for reading section header table\n");

      return NULL;

   }

   if (pread(fd, shbuf, nbytes, hdr->e_shoff) != nbytes) {

      print_debug("ELF file is truncated! can't read section header table\n");

      free(shbuf);

      return NULL;

   }

   return shbuf;

}

// read a particular section's data

void* read_section_data(int fd, ELF_EHDR* ehdr, ELF_SHDR* shdr) {

  void *buf = NULL;

  if (shdr->sh_type == SHT_NOBITS || shdr->sh_size == 0) {

     return buf;

  }

  if ((buf = calloc(shdr->sh_size, 1)) == NULL) {

     print_debug("can't allocate memory for reading section data\n");

     return NULL;

  }

  if (pread(fd, buf, shdr->sh_size, shdr->sh_offset) != shdr->sh_size) {

     free(buf);

     print_debug("section data read failed\n");

     return NULL;

  }

  return buf;

}

uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) {

  uintptr_t baseaddr = (uintptr_t)-1;

  int cnt;

  ELF_PHDR *phbuf, *phdr;

  // read program header table

  if ((phbuf = read_program_header_table(fd, ehdr)) == NULL) {

    goto quit;

  }

  // the base address of a shared object is the lowest vaddr of

  // its loadable segments (PT_LOAD)

  for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) {

    if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) {

      baseaddr = phdr->p_vaddr;

    }

  }

quit:

  if (phbuf) free(phbuf);

  return baseaddr;

}