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RE: vdso handling
- From: "Metzger, Markus T" <markus dot t dot metzger at intel dot com>
- To: Alan Modra <amodra at gmail dot com>, Cary Coutant <ccoutant at google dot com>
- Cc: Doug Evans <dje at google dot com>, "gdb at sourceware dot org" <gdb at sourceware dot org>, "binutils at sourceware dot org" <binutils at sourceware dot org>
- Date: Thu, 13 Mar 2014 08:23:40 +0000
- Subject: RE: vdso handling
- Authentication-results: sourceware.org; auth=none
- References: <A78C989F6D9628469189715575E55B230AA884EB at IRSMSX104 dot ger dot corp dot intel dot com> <20140312071701 dot GW26922 at bubble dot grove dot modra dot org> <CADPb22SAmK5JB3muW_nCvuHN5L-aOcdyzYNR+OtnM3bA1x_OJg at mail dot gmail dot com> <CAHACq4o=HmdCo1FPFL-96raf2UN805jvM=VZM-9dbKrmzJFJTw at mail dot gmail dot com> <20140313010147 dot GZ26922 at bubble dot grove dot modra dot org>
> -----Original Message-----
> From: Alan Modra [mailto:amodra@gmail.com]
> Sent: Thursday, March 13, 2014 2:02 AM
> To: Cary Coutant
> Cc: Doug Evans; Metzger, Markus T; gdb@sourceware.org;
> binutils@sourceware.org
> Subject: Re: vdso handling
>
> On Wed, Mar 12, 2014 at 01:22:58PM -0700, Cary Coutant wrote:
> > > I think a case can be made that gdb should be able to use the
> > > "execution view" of the program here.
> > > As for how to achieve that ... "Discuss." :-)
> >
> > Add a PT_DEBUG program header entry? The PT_DEBUG segment would
> need
> > to have a small header that allows the debugger to find .debug_abbrev,
> > .debug_info, etc. (i.e., a mini section table). Or, just add
> > individual program header entries for each of the standard debug
> > sections: PT_DEBUG_ABBREV, PT_DEBUG_INFO, etc.
>
> Debug sections are not normally loaded. For that reason I don't think
> it makes any sense to specify program headers for them. It wouldn't
> help in the vdso case anyway, since the problem there is that you only
> have the loaded part of the original ELF file.
The vdso contains a section table, as well. When I hack
bfd_from_remote_memory to create BFD sections from them similar
to what elf_object_p does, I get the target sections that I wanted in GDB.
The patch is rather big, though, and duplicating a lot of elf_object_p's code.
I have not tried generating fake sections from segments, yet.
Regards,
Markus.
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