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RE: [patch] [gdbserver] Do not crash on file load without inferior
- From: Marc Khouzam <marc dot khouzam at ericsson dot com>
- To: "'Pedro Alves'" <pedro at codesourcery dot com>, "'gdb-patches at sourceware dot org'" <gdb-patches at sourceware dot org>
- Cc: "'Jan Kratochvil'" <jan dot kratochvil at redhat dot com>
- Date: Fri, 4 Mar 2011 16:24:51 -0500
- Subject: RE: [patch] [gdbserver] Do not crash on file load without inferior
- References: <20110224114001.GA24673@host1.dyn.jankratochvil.net> <201102241242.49342.pedro@codesourcery.com>
> -----Original Message-----
> From: gdb-patches-owner@sourceware.org
> [mailto:gdb-patches-owner@sourceware.org] On Behalf Of Pedro Alves
> Sent: Thursday, February 24, 2011 7:43 AM
> To: gdb-patches@sourceware.org
> Cc: Jan Kratochvil
> Subject: Re: [patch] [gdbserver] Do not crash on file load
> without inferior
>
> On Thursday 24 February 2011 11:40:02, Jan Kratochvil wrote:
> > Hi Pedro,
> >
> > I always got:
> >
> > (gdb) file .../gdb/testsuite/gdb.server/ext-run
> > Load new symbol table from
> ".../gdb/testsuite/gdb.server/ext-run"? (y or n) y
> > Reading symbols from .../gdb/testsuite/gdb.server/ext-run...done.
> > gdbserver: Current inferior requested, but current_inferior is NULL
> >
> > Remote connection closed
> > (gdb)
> >
> > if one connects to gdbserver --multi before loading the
> file. One needs to
> > load the file first to be able to place a breakpoint at
> *_start or main.
> >
> > But I face other bugs so I cannot say much more.
> >
> > I do not think this patch can ever have a regression.
>
> Thanks. I that revealed a problem on the GDB side instead.
>
> E.g., if you have two inferiors loaded, and the not-current
> inferior is running, but you do "file" on the not-running-yet
> inferior, you'll see:
>
> $ ./gdb ./testsuite/gdb.server/ext-run -ex "tar
> extended-remote :9999" -ex "set remote exec-file
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-ru
> n" -ex "start"
> ...
> Reading symbols from
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-ru
> n...done.
> Setting up the environment for debugging gdb.
> Remote debugging using :9999
> Temporary breakpoint 1 at 0x4004ef: file
> ../../../src/gdb/testsuite/gdb.server/server.c, line 21.
> Starting program:
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-run
>
> Temporary breakpoint 1, main (argc=1, argv=0x7fffffffe068) at
> ../../../src/gdb/testsuite/gdb.server/server.c:21
> 21 return 0;
> (gdb) add-inferior
> Added inferior 2
> (gdb) info inferiors
> Num Description Executable
> 2 <null>
> * 1 process 15952
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-run
> (gdb) inferior 2
> [Switching to inferior 2 [Thread 0.0] (<noexec>)]
> (gdb) set debug remote 1
> (gdb) file
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-run
> Reading symbols from
> /home/pedro/gdb/baseline/build/gdb/testsuite/gdb.server/ext-ru
> n...done.
> Sending packet: $Hgp0.0#ad...Packet received: OK
> ^^^^^^^
> Sending packet: $qSymbol::#5b...Packet received:
> qSymbol:6764625f6167656e745f6764625f74705f686561705f627566666572
> Sending packet:
> $qSymbol::6764625f6167656e745f6764625f74705f686561705f62756666
> 6572#1e...Packet received:
> qSymbol:6764625f6167656e745f6764625f6a756d705f7061645f627566666572
> Sending packet:
> $qSymbol::6764625f6167656e745f6764625f6a756d705f7061645f627566
> 666572#e1...Packet received:
> qSymbol:6764625f6167656e745f6764625f6a756d705f7061645f62756666
> 65725f656e64
> Sending packet:
> $qSymbol::6764625f6167656e745f6764625f6a756d705f7061645f627566
> 6665725f656e64#ec...Packet received:
> qSymbol:6764625f6167656e745f636f6c6c656374696e67
>
>
> But, Hgp0.0 means select _any_ thread in any process, not _no
> thread at all_.
> Meaning GDBserver's current_inferior ends up set to a thread of the
> wrong process, and GDBserver is querying inferior 1's symbols on
> inferior 2! See on GDBserver:
>
> (gdb) p current_inferior->entry.id
> $3 = {pid = 15952, lwp = 15952, tid = 0}
That sounds pretty bad.
Any chance of getting a fix for this in the 7_2 branch?
Which I gather would fix the problem Jan originally reported.
Having to specify the 'file' before connecting to the target
is a regression from previous versions of GDB and I was hoping
not to have to special-case it in Eclipse :-)
Thanks
Marc
>
> So I think that we shouldn't send qSymbol at all when inferior_ptid is
> null_ptid or rather with !target_has_execution (which ends up in
> default_child_has_execution and currently resolves the same)?
>
> --
> Pedro Alves
>