Re: backtrace/2224: backtrace doesn't work with bochs stub anymore

["Godmar Back" <godmar at gmail dot com>]

The following reply was made to PR backtrace/2224; it has been noted by GNATS.

From: "Godmar Back" <godmar@gmail.com>
To: "Daniel Jacobowitz" <drow@false.org>
Cc: gdb-gnats@sources.redhat.com
Subject: Re: backtrace/2224: backtrace doesn't work with bochs stub anymore
Date: Tue, 6 Feb 2007 22:14:04 -0500

 Urls are - works:
 http://people.cs.vt.edu/~gback/pintos/qemu-gdb.txt
 Doesn't work:
 http://people.cs.vt.edu/~gback/pintos/bochs-gdb.txt
 
 Output when it doesn't work - with bochs's stub:
 (gdb) target remote pistachio:1235
 Remote debugging using pistachio:1235
 0x0000fff0 in ?? ()
 Reply contains invalid hex digit 78
 (gdb) b test_priority_change
 Breakpoint 1 at 0xc010bc0c: file ../../tests/threads/priority-change.c, line 14.
 (gdb) c
 Continuing.
 
 Breakpoint 1, test_priority_change () at
 ../../tests/threads/priority-change.c:14
 14      {
 (gdb) bt
 #0  test_priority_change () at ../../tests/threads/priority-change.c:14
 Reply contains invalid hex digit 78
 (gdb) quit
 -------
 Output when it does work, with qemu's stub:
 
 GNU gdb Red Hat Linux (6.5-15.fc6rh)
 Copyright (C) 2006 Free Software Foundation, Inc.
 GDB is free software, covered by the GNU General Public License, and you are
 welcome to change it and/or distribute copies of it under certain conditions.
 Type "show copying" to see the conditions.
 There is absolutely no warranty for GDB.  Type "show warranty" for details.
 This GDB was configured as "i386-redhat-linux-gnu"...Using host
 libthread_db library "/lib/libthread_db.so.1".
 
 (gdb) target remote localhost:1235
 Remote debugging using localhost:1235
 0x0000fff0 in ?? ()
 (gdb) b test_priority_change
 Breakpoint 1 at 0xc010bc0c: file ../../tests/threads/priority-change.c, line 14.
 (gdb) c
 Continuing.
 
 Breakpoint 1, test_priority_change () at
 ../../tests/threads/priority-change.c:14
 14      {
 (gdb) bt
 #0  test_priority_change () at ../../tests/threads/priority-change.c:14
 #1  0xc010b1af in run_test (name=0xc0007d82 "priority-change")
     at ../../tests/threads/tests.c:56
 #2  0xc010069f in run_task (argv=0xc0113420) at ../../threads/init.c:268
 #3  0xc010078b in run_actions (argv=0xc0113420) at ../../threads/init.c:318
 #4  0xc01000a2 in main () at ../../threads/init.c:121
 (gdb) quit
 The program is running.  Exit anyway? (y or n) y
 
 The test yourself, you'd have to install bochs 2.2.6 and Pintos.
 
 Thanks!
 
  - Godmar
 
 
 On 2/6/07, Daniel Jacobowitz <drow@false.org> wrote:
 > On Wed, Feb 07, 2007 at 03:07:09AM -0000, godmar@gmail.com wrote:
 > > gdb used to show backtraces when used with bochs 2.2.6. It did so in
 > > version 6.3.0.0 shipped with FC4. It fails to do so with 6.5-15,
 > > shipped with FC6.
 > >
 > > The reason, I speculate, is that bochs sends the following reply to
 > > the $qOffsets query:
 > >
 > > $Text=0;Data=0;Bss=0#
 >
 > That should be fine.
 >
 > > qemu, on the other hand, simply ignores the qOffsets query, but on
 > > qemu, backtrace works.
 > >
 > > With bochs, gdb 6.5 never sends the necessary $m's to examine the backtrace.
 > > See:
 >
 > Missing URL?  Sorry, there isn't enough information here to reproduce
 > the problem.  Run _what_ in bochs?
 >
 > Please post a small test case and the complete text of your session.
 >
 > --
 > Daniel Jacobowitz
 > CodeSourcery
 >