RE: [PATCH v3 3/3] btrace, vdso: add vdso target sections

["Metzger, Markus T" <markus.t.metzger@intel.com>]

Thanks for reporting this crash.  I'll look into it.  I thought I ran all tests
for each patch in the vdso series.

It seems btrace got broken, as well.  I now get an assertion: "
to_execution_direction must be implemented ...".  The trivial solution
of providing a to_execution_direction method that just returns
execution_direction does not seem to work - or there's another
bug underneath.

Regards,
Markus.

> -----Original Message-----
> From: Pedro Alves [mailto:palves@redhat.com]
> Sent: Thursday, May 29, 2014 7:04 PM
> To: Metzger, Markus T
> Cc: gdb-patches@sourceware.org
> Subject: Re: [PATCH v3 3/3] btrace, vdso: add vdso target sections
> 
> On 05/29/2014 05:54 PM, Pedro Alves wrote:
> > Hi Markus,
> >
> > On 05/21/2014 08:01 AM, Markus Metzger wrote:
> >> When loading symbols for the vdso, also add its sections to
> target_sections.
> >>
> >> This fixes an issue with record btrace where vdso instructions could not be
> >> disassembled during replay.
> >>
> >> 2014-05-21  Markus Metzger  <markus.t.metzger@intel.com>
> >>
> >> 	* symfile-mem.c (symbol_file_add_from_memory): Add BFD
> sections.
> >
> > Unfortunately this caused regressions in break-interp.exp:
> >
> >  Running ../../../src/gdb/testsuite/gdb.base/break-interp.exp ...
> >  ERROR: Process no longer exists
> >
> > That is GDB crashing.
> >
> > 589fdceb99db9868e34bc976b7e234dbfaf327e2 is the first bad commit
> > commit 589fdceb99db9868e34bc976b7e234dbfaf327e2
> > Author: Markus Metzger <markus.t.metzger@intel.com>
> > Date:   Wed Apr 2 09:54:11 2014 +0200
> >
> >     btrace, vdso: add vdso target sections
> >
> >     When loading symbols for the vdso, also add its sections to
> target_sections.
> >
> >     This fixes an issue with record btrace where vdso instructions could not
> be
> >     disassembled during replay.
> >
> >         * symfile-mem.c (symbol_file_add_from_memory): Add BFD sections.
> >
> >     testsuite/
> >         * gdb.btrace/vdso.c: New.
> >         * gdb.btrace/vdso.exp: New.
> >
> >
> > Core was generated by
> `/home/pedro/gdb/mygit/build/gdb/testsuite/../../gdb/gdb -nw -nx -data-
> directory'.
> > Program terminated with signal SIGSEGV, Segmentation fault.
> > #0  0x0000000000647bce in exec_set_section_address
> (filename=0x27bb1f0
> "/home/pedro/gdb/mygit/build/gdb/testsuite/gdb.base/break-interp-
> LDprelinkNOdebugNO", index=0,
> >     address=139930618982856) at ../../src/gdb/exec.c:919
> > 919           if (filename_cmp (filename, p->the_bfd_section->owner-
> >filename) == 0
> 
> 'p', a target section, points at garbage.
> 
> Hmm, wait, nothing is removing the vdso symbols target sections, like ever,
> not even when the process dies, isn't it?  I guess that's it.
> 
> --
> Pedro Alves

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