Re: BFD assumes ELF phdrs in core files are just after ELF header

[Nick Clifton]

Hi Mirek,

: BFD in binutils 2.10.1 (affects gdb 5.0 as well) assumes that
: program headers in ELF core files immediatelly follow the ELF
: header. To reproduce, look at the attached core file:
:
: but 'objdump -p core' says:
:
:    SHLIB off    0x00000000 vaddr 0x00000001 paddr 0x00002000 align 2**12
:          filesz 0x0804e000 memsz 0x00000000 flags --- 1000
:      0x7 off    0x00000000 vaddr 0x00000001 paddr 0x00003000 align 2**12
:          filesz 0xbf7c2000 memsz 0x00000000 flags ---
: This is completely bogus, and is made from the data directly following the
: ELF header, which is in fact occupied by the note segment.

Thanks for reporting this.

: Possible fix (completely untested! - not even that it compiles):
: ----------------------------------------------------------------
: --- elfcore.h.orig      Fri Dec 15 14:54:50 2000
: +++ elfcore.h   Fri Dec 15 14:56:32 2000
: @@ -193,6 +193,8 @@
: 
:    elf_tdata (abfd)->phdr = i_phdrp;
: 
: +  if (bfd_seek (abfd, i_ehdrp->e_phoff, SEEK_SET) != 0)
: +    return NULL;
:    /* Read and convert to internal form. */
:    for (phindex = 0; phindex < i_ehdrp->e_phnum; ++phindex)
:      {
: ----------------------------------------------------------------

This works, but I have actually checked in a slight variation which
uses 'goto wrong' so that an error code is set before the function
exits.

Cheers
        Nick

2000-12-15  Miloslav Trmac <address@hidden>

        * elfcore.h (elf_core_file_p): Move to the start of the program
        headers before attempting to read them.

Index: bfd/elfcore.h
===================================================================
RCS file: /cvs/src//src/bfd/elfcore.h,v
retrieving revision 1.4
diff -p -r1.4 elfcore.h
*** elfcore.h   2000/06/19 01:22:37     1.4
--- elfcore.h   2000/12/15 18:51:11
*************** elf_core_file_p (abfd)
*** 182,187 ****
--- 182,191 ----
    if (i_ehdrp->e_phentsize != sizeof (Elf_External_Phdr))
      goto wrong;
  
+   /* Move to the start of the program headers.  */
+   if (bfd_seek (abfd, i_ehdrp->e_phoff, SEEK_SET) != 0)
+     goto wrong;
+   
    /* Allocate space for the program headers. */
    i_phdrp = (Elf_Internal_Phdr *)
      bfd_alloc (abfd, sizeof (*i_phdrp) * i_ehdrp->e_phnum);