Re: [PATCH][gdb] Fix fbsd core matching

[John Baldwin <jhb@FreeBSD.org>]

On 6/9/22 1:58 AM, Tom de Vries via Gdb-patches wrote:
> Hi,
> 
> With an --enable-targets=all build and target board unix/-m32 I run into a
> FAIL in test-case gdb.base/corefile.exp:
> ...
> (gdb) file outputs/gdb.base/corefile/corefile^M
> Reading symbols from outputs/gdb.base/corefile/corefile...^M
> (gdb) core-file outputs/gdb.base/corefile/corefile.core^M
> warning: core file may not match specified executable file.^M
> [New LWP 12011]^M
> Core was generated by `outputs/gdb.base/corefile/co'.^M
> Program terminated with signal SIGABRT, Aborted.^M
> (gdb) FAIL: gdb.base/corefile.exp: core-file warning-free
> ...
> 
> The warning is there because of this mismatch between core and exec:
> ...
> (gdb) p core_bfd->xvec
> $3 = (const struct bfd_target *) 0x20112a0 <i386_elf32_fbsd_vec>
> (gdb) p exec_bfd->xvec
> $4 = (const struct bfd_target *) 0x2010b00 <i386_elf32_vec>
> ...
> 
> In the exec case, the detected architecture is i386_elf32_vec because this bit
> of code in elfcode.h:elf_object_p():
> ...
>    if (ebd->elf_machine_code != EM_NONE
>        && i_ehdrp->e_ident[EI_OSABI] != ebd->elf_osabi
>        && ebd->elf_osabi != ELFOSABI_NONE)
>      goto got_wrong_format_error;
> ...
> prevents i386_elf32_fbsd from matching.
> 
> Fix the core matching by copying that code to elfcore.h:elf_core_file_p().
> 
> Tested on x86_64-linux.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29227
> 
> Any comments?

Looking at elfcore.h, it seems to have not gotten changes made to elfcode.h over
time and is a bit rotted.  I suspect that all of changes made in commit 0aabe54e6222
that added these lines in elfcode.h (along with several other changes) need to
be applied to this function in elfcore.h, not just adding these lines.

I've cc'd Alan who made that commit above to elfcore.h.  There also seem to be
some other inconsistencies between the functions in elfcore.h and and elfcode.h
and perhaps the common functionality in these functions could be refactored
into a separate function to avoid the code duplication?

Note that the issue isn't really FreeBSD specific, I just suspect that the FreeBSD
i386 vec happens to be sorted first in the list for some reason.
  
> Thanks,
> - Tom
> 
> [gdb] Fix fbsd core matching
> 
> ---
>   bfd/elfcore.h | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/bfd/elfcore.h b/bfd/elfcore.h
> index 809f6711aed..4ce81e2e383 100644
> --- a/bfd/elfcore.h
> +++ b/bfd/elfcore.h
> @@ -272,6 +272,11 @@ elf_core_file_p (bfd *abfd)
>         && ebd->elf_machine_code != EM_NONE)
>       goto fail;
>   
> +  if (ebd->elf_machine_code != EM_NONE
> +      && i_ehdrp->e_ident[EI_OSABI] != ebd->elf_osabi
> +      && ebd->elf_osabi != ELFOSABI_NONE)
> +    goto fail;
> +
>     /* Let the backend double check the format and override global
>        information.  We do this before processing the program headers
>        to allow the correct machine (as opposed to just the default


-- 
John Baldwin