Fix fbsd core matching

On Thu, Jun 09, 2022 at 08:59:37AM -0700, John Baldwin wrote:
> 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?

Looks good.

> 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.

Yes, the commit 0aabe54e6222 changes likely should go in too.  I'm a
little wary of adding all the sanity checks to elf_core_file_p since
that might result in some core files not being recognised at all.  For
example, despite the FIXME I'd guess leaving out the EI_VERSION check
was deliberate.  The following seems reasonable to me.  Please test.

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