#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <elf.h>
#include <stdlib.h>
#include <endian.h>
#include <bits/wordsize.h>
/* Reads an ELF file, nukes all the RPATH entries. */

int
main(int argc, char **argv)
{
  int fd;
#if __WORDSIZE==32
  Elf32_Ehdr ehdr;
  Elf32_Phdr phdr;
  Elf32_Dyn *dyns;
#elif __WORDSIZE==64
  Elf64_Ehdr ehdr;
  Elf64_Phdr phdr;
  Elf64_Dyn *dyns;
#endif
  int i;
  int dynpos;

#if __BYTE_ORDER==__LITTLE_ENDIAN
    printf ("Using %d-bit LSB format\n", __WORDSIZE);
#elif __BYTE_ORDER==__BIG_ENDIAN
    printf ("Using %d-bit MSB format\n", __WORDSIZE);
#else
    print ("Unknown endian\n");
    return 1;
#endif

  if (argc != 2)
  {
    printf ("Usage: %s objectfile\n", argv[0]);
    return 1;
  }

  fd = open(argv[1], O_RDWR);
  if (fd == -1)
  {
    perror ("open");
    return 1;
  }
  
  if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
  {
    perror ("reading header");
    return 1;
  }

  if (*(unsigned *)ehdr.e_ident != *(const unsigned *)ELFMAG ||
#if __WORDSIZE==32
      ehdr.e_ident[EI_CLASS] != ELFCLASS32 ||
#elif __WORDSIZE==64
      ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
#endif
#if __BYTE_ORDER==__LITTLE_ENDIAN
      ehdr.e_ident[EI_DATA] != ELFDATA2LSB ||
#elif __BYTE_ORDER==__BIG_ENDIAN
      ehdr.e_ident[EI_DATA] != ELFDATA2MSB ||
#endif
      ehdr.e_ident[EI_VERSION] != EV_CURRENT)
  {
#if __BYTE_ORDER==__LITTLE_ENDIAN
    fprintf(stderr, "`%s' probably isn't a %d-bit LSB-first ELF file.\n",
#elif __BYTE_ORDER==__BIG_ENDIAN
    fprintf(stderr, "`%s' probably isn't a %d-bit MSB-first ELF file.\n",
#endif
	    argv[1], __WORDSIZE);
    return 1;
  }

#if __WORDSIZE==32
  if (ehdr.e_phentsize != sizeof(Elf32_Phdr))
  {
    fprintf(stderr, "section size was read as %d, not %d!\n",
	    ehdr.e_phentsize, sizeof(Elf32_Phdr));
    return 1;
  }
#elif __WORDSIZE==64
  if (ehdr.e_phentsize != sizeof(Elf64_Phdr))
  {
    fprintf(stderr, "section size was read as %d, not %d!\n",
	    ehdr.e_phentsize, sizeof(Elf64_Phdr));
    return 1;
  }
#endif

  if (lseek(fd, ehdr.e_phoff, SEEK_SET) == -1)
  {
    perror ("positioning for sections");
    return 1;
  }
  
  for (i = 0; i < ehdr.e_phnum; i++)
  {
    if (read(fd, &phdr, sizeof(phdr)) != sizeof(phdr))
    {
      perror ("reading section header");
      return 1;
    }
    if (phdr.p_type == PT_DYNAMIC)
      break;
  }
  if (i == ehdr.e_phnum)
    {
      fprintf (stderr, "No dynamic section found.\n");
      return 2;
    }

  dyns = malloc(phdr.p_memsz);
  if (dyns == NULL)
    {
      perror ("allocating memory for dynamic section");
      return 1;
    }
  memset(dyns, 0, phdr.p_memsz);
  if (lseek(fd, phdr.p_offset, SEEK_SET) == -1
      || read(fd, dyns, phdr.p_filesz) != phdr.p_filesz)
    {
      perror ("reading dynamic section");
      return 1;
    }

  dynpos = 0;
  for (i = 0; dyns[i].d_tag != DT_NULL; i++)
    {
      dyns[dynpos] = dyns[i];
      if (dyns[i].d_tag != DT_RPATH)
	dynpos++;
    }
  for (; dynpos < i; dynpos++)
    dyns[dynpos].d_tag = DT_NULL;

  if (lseek(fd, phdr.p_offset, SEEK_SET) == -1
      || write(fd, dyns, phdr.p_filesz) != phdr.p_filesz)
    {
      perror ("writing dynamic section");
      return 1;
    }
  return 0;
}