vdso handling

Samuel Bronson naesten@gmail.com
Sun Jun 1 20:32:00 GMT 2014

Pedro Alves <palves@redhat.com> writes:

> On 03/13/2014 10:07 AM, Pedro Alves wrote:
>> Why's that?  Why doesn't the memory-backed bfd paths take the same paths as
>> a file-backed bfd internally in bfd?  It sounds to me that this should be
>> doable without duplication.
> BTW, I meant that for vDSO's only.  The vsyscall page is not an elf,
> and therefore bfd still needs to be passed a template elf.  For the
> latter, GDB would indeed need to work with the segments.  Do we still
> care for vsyscall kernels?  But for the former, bfd should just be
> able to read the whole DSO as a plain elf.
> Some glibc versions even include the vdso in the DSO list (*), and GDB
> should be able to tell that that DSO is the vDSO (by matching addresses), and
Hmm, why don't we already do that? It's bound to be easier than meeting
the conditions to get glibc to stop falsely cliaming that the vDSO comes
from a file <https://sourceware.org/bugzilla/show_bug.cgi?id=13097#c5>.

That'd be enough to take two bugs off of <http://bugs.debian.org/gdb>
right there.

> load it completely from memory, still using a memory backed bfd, but _without_
> a template.  So with that in mind, bfd should be able to read the vdso
> as a bfd from memory using the same paths as a file-backed bfd, except,
> well, the bfd's backing store is in memory rather than in a file.
> (*) note how linux-vdso.so.1 is listed by ldd, even if "info shared" in gdb
> doesn't show it, on some systems.

What versions don't list the vdso under some name or other?  (Mine calls
it linux-gate.so.1 for some reason.)

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