Bug#794488: Re: Bug#794488: Piglit tests in Mesa crash, if radeonsi_dri.so is linked with libelf1 (libelfg0 works)

[Mark Wielaard]

On Wed, 2015-08-05 at 17:55 +0200, Kai Wasserbäch wrote:
> So, if I've understood you correctly, you want an ELF dump of a Mesa build
> linked against libelfg0 and one linked against libelf1. You can find the
> generated files in the attached Tar archive. Please note, that the run with
> libelf1 only produced two dumps before segfaulting.

That seems to confirm that the generation is the same (at least for the
first two files). I was hoping to find a difference between parsing some
of these files with an old/new libelf. So I wrote a little program that
is just the parsing as radeon_elf_read () does. But found no difference.
Maybe I am not testing against the right versions though (they are my
local builds).

Could you compile the following with:
gcc -g -lelf -o elfrel elfrel.c
and then run it against all these ELF files with the bad libelf like
for i in 794488_elfs/libelf*/dump.elf.*; do ./elfrel $i; done

For me the output looks like:

file: 794488_elfs/libelf1/dump.elf.EL5kJT
Nothing found
file: 794488_elfs/libelf1/dump.elf.J4EnbO
symbols: 5
1: not global or undefined
2: not global or undefined
3: not global or undefined
4: not global or undefined
5: 0
relocations: 2
0: 10, SCRATCH_RSRC_DWORD1
1: 2c, SCRATCH_RSRC_DWORD0
file: 794488_elfs/libelfg0/dump.elf.7NnBvc
Nothing found
file: 794488_elfs/libelfg0/dump.elf.ahPsJJ
symbols: 5
1: not global or undefined
2: not global or undefined
3: not global or undefined
4: not global or undefined
5: 0
relocations: 2
0: 10, SCRATCH_RSRC_DWORD1
1: 2c, SCRATCH_RSRC_DWORD0
file: 794488_elfs/libelfg0/dump.elf.DYTjdO
Nothing found
file: 794488_elfs/libelfg0/dump.elf.Lke6Xg
Nothing found

Hopefully for you the output looks different with the bad (or good)
libelf. Then I need to make sure I have the right bad/good version
myself. Otherwise I need to dig a bit deeper to understand what is going
wrong.

Thanks,

Mark

$ cat elfrel.c 
#include <gelf.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int
main (int argc, char **argv)
{
  elf_version(EV_CURRENT);

  printf ("file: %s\n", argv[1]);
  int fd = open (argv[1], O_RDONLY);
  Elf *elf = elf_begin (fd, ELF_C_READ, NULL);

  size_t section_str_index;
  elf_getshdrstrndx(elf, &section_str_index);

  size_t reloc_count, symbol_sh_link, symbol_count;
  Elf_Data *relocs, *symbols;
    {
      const char *name;
      GElf_Shdr section_header;
      if (gelf_getshdr(section, &section_header) != &section_header)
        {
          fprintf(stderr, "Failed to read ELF section header\n");
          return -1;
        }

      name = elf_strptr(elf, section_str_index, section_header.sh_name);

      if (strncmp(name, ".symtab", 7) == 0)
        {
          symbols = elf_getdata(section, NULL);
          symbol_sh_link = section_header.sh_link;
          symbol_count = section_header.sh_size / section_header.sh_entsize;
        }
      else if (strcmp (name, ".rel.text") == 0)
        {
          relocs = elf_getdata(section, NULL);
          reloc_count = section_header.sh_size / section_header.sh_entsize;
        }
    }

  if (!relocs || !symbols || !reloc_count)
    {
      printf("Nothing found\n");
      return -1;
    }

  printf ("symbols: %zd\n", symbol_count);
  GElf_Sym symbol;
  size_t i = 0;
  while (gelf_getsym (symbols, i++, &symbol))
    {
      if (GELF_ST_BIND(symbol.st_info) != STB_GLOBAL
          || symbol.st_shndx == 0)
        {
          printf ("%zd: not global or undefined\n", i);
          continue;
        }

      printf ("%zd: %" PRIx64 "\n", i, symbol.st_value);
    }

  printf ("relocations: %zd\n", reloc_count);
  for (size_t i = 0; i < reloc_count; i++)
    {
      GElf_Sym symbol;
      GElf_Rel rel;
      char *symbol_name;

      gelf_getrel(relocs, i, &rel);
      gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &symbol);
      symbol_name = elf_strptr(elf, symbol_sh_link, symbol.st_name);

      printf ("%zd: %" PRIx64 ", %s\n", i, rel.r_offset, symbol_name);
    }

  return 0;
}


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