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Re: [PATCH] testsuite: Add (extensive) hardware breakpoint testing
On Fri, 11 Nov 2011, Joel Brobecker wrote:
> > > ?The consistency of failures between i686-linux-gnu and i686-mingw makes
> > > me fairly sure that's a bug in x86 support in GDB of some sort rather than
> > > a problem with my setup -- is that a known bug?
> >
> > OOC, have you tried amd64-linux?
I have now, and the result is the same -- breakpoints silently missed.
> > {i386,amd64}-linux are important enough targets that I think this
> > should be fixed for 7.4. Joel?
>
> I think we should look at the context as well before making a decision:
> - Is that a regression? If it's been like that in previous versions,
> then maybe it's OK for it to fail for another version...
> - Are hardware breakpoints used much? Probably by the people who
> debug programs in ROM(/flash?).
Plus self-modifying code -- although I agree that hardware execution
breakpoints are less needed with hosted systems than on bare-iron targets.
> We should probably try to investigate the problem quickly and determine
> the extent of the problem. If we think we should fix that for 7.4, and
> someone is willing to take responsibility for it, then let's make it
> a high priority item on our list, and not release 7.4 without the fix.
Well, OOC I looked at the relevant source and the bug (and consequently
the fix) is quite obvious -- the debug registers are only actually pushed
down to hardware on data breakpoints and not execution breakpoints.
I'm getting:
# of expected passes 69
# of unexpected failures 2
now on x86_64-linux-gnu. The two failures are some matching problems with
my hbreak2.exp -- I'll investigate and fix that up.
OK to apply?
2011-11-11 Maciej W. Rozycki <macro@codesourcery.com>
gdb/
* i386-nat.c (i386_insert_hw_breakpoint): Call
i386_update_inferior_debug_regs.
(i386_remove_hw_breakpoint): Likewise.
Maciej
gdb-i386-hbreak.diff
Index: gdb-fsf-trunk-quilt/gdb/i386-nat.c
===================================================================
--- gdb-fsf-trunk-quilt.orig/gdb/i386-nat.c 2011-11-07 13:42:30.000000000 +0000
+++ gdb-fsf-trunk-quilt/gdb/i386-nat.c 2011-11-11 18:47:40.555635587 +0000
@@ -684,9 +684,15 @@ i386_insert_hw_breakpoint (struct gdbarc
{
unsigned len_rw = i386_length_and_rw_bits (1, hw_execute);
CORE_ADDR addr = bp_tgt->placed_address;
- int retval = i386_insert_aligned_watchpoint (&dr_mirror,
+ /* Work on a local copy of the debug registers, and on success,
+ commit the change back to the inferior. */
+ struct i386_debug_reg_state local_state = dr_mirror;
+ int retval = i386_insert_aligned_watchpoint (&local_state,
addr, len_rw) ? EBUSY : 0;
+ if (retval == 0)
+ i386_update_inferior_debug_regs (&local_state);
+
if (maint_show_dr)
i386_show_dr (&dr_mirror, "insert_hwbp", addr, 1, hw_execute);
@@ -702,9 +708,15 @@ i386_remove_hw_breakpoint (struct gdbarc
{
unsigned len_rw = i386_length_and_rw_bits (1, hw_execute);
CORE_ADDR addr = bp_tgt->placed_address;
- int retval = i386_remove_aligned_watchpoint (&dr_mirror,
+ /* Work on a local copy of the debug registers, and on success,
+ commit the change back to the inferior. */
+ struct i386_debug_reg_state local_state = dr_mirror;
+ int retval = i386_remove_aligned_watchpoint (&local_state,
addr, len_rw);
+ if (retval == 0)
+ i386_update_inferior_debug_regs (&local_state);
+
if (maint_show_dr)
i386_show_dr (&dr_mirror, "remove_hwbp", addr, 1, hw_execute);