Re: [patch] solib-svr4.c - allow reading linkmap info from core without executable

Pedro Alves
2009-06-10T22:07:26Z

On Friday 29 May 2009 21:41:52, Aleksandar Ristovski wrote:
> Hello,
>
> This small patch allows solib-svr4.c to attempt to read
> linkmap info from core file when executable binary is not given.
>
> e.g.:
> $ gdb --core testsuite/gdb.base/bigcore.corefile
> ...
> (gdb) info sharedlibrary
> No shared libraries loaded at this time.
> (gdb)
>
> after patch:
>
> $ ./gdb --nx --core testsuite/gdb.base/bigcore.corefile
> GNU gdb (GDB) 6.8.50.20090529-cvs
> ...
> (gdb) info shared
> From To Syms Read Shared Object Library
> 0x4cb3e470 0x4cb58844 No /lib/libm.so.6
> 0x4ca18dd0 0x4cafe490 No /lib/libc.so.6
> 0x4c9e5880 0x4c9fa8ef No /lib/ld-linux.so.2
> (gdb)

Cool.

> if (info->debug_base == 0 && svr4_have_link_map_offsets ())
> {
> - if (exec_bfd != NULL
> + if ((exec_bfd != NULL
> && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
> + || (core_bfd != NULL
> + && bfd_get_flavour (core_bfd) == bfd_target_elf_flavour))
> info->debug_base = elf_locate_base ();
> }

Are there live debugging cases (archs?, PIE?) (e.g., "target remote"
without specifying an executable) where letting elf_locate_base
try to read the debug base from the target's auxv (scan_dyntag_auxv)
will work? It would mean that removing the exec_bfd checks instead
of adding core_bfd checks, would still improve your case, while
letting other cases benefit as well.

--
Pedro Alves