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

["Metzger, Markus T" <markus dot t dot metzger at intel dot com>]

> -----Original Message-----
> From: Metzger, Markus T
> Sent: Monday, June 2, 2014 10:21 AM
> To: Pedro Alves
> Cc: gdb-patches@sourceware.org
> Subject: RE: [PATCH v3 3/3] btrace, vdso: add vdso target sections
> 
> 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.

Looks like btrace got broken when async was made default and btrace
did not support it.  I took the async bits from record-full and now at
least the btrace tests are running again.  I'll send the patch in a separate
email.

Regards,
Markus.


> 
> 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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