Re: [PATCH,ARM] Fix single step on vfork

Yao Qi
2010-09-02T01:04:14Z

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Pedro Alves wrote:
> On Wednesday 01 September 2010 17:56:32, Yao Qi wrote:
>> + /* Don't consider single-stepping when the inferior is
>> + waiting_for_vfork_done, either software or hardware step. In
>> + software step, child process will hit the software single step
>> + breakpoint inserted in parent process. In hardware step, GDB
>> + can resumes inferior, and waiting for vfork_done event. */
>
> This last sentence looks incomplete? At least, I can't seem to
> parse it.
>
I replaced "waiting" by "wait" in the new patch.

>> + if (current_inferior()->waiting_for_vfork_done)
>
> Space before parens.
>

Fixed.

>> if (use_displaced_stepping (gdbarch)
>> && (tp->trap_expected
>> || (step && gdbarch_software_single_step_p (gdbarch)))
>> - && sig == TARGET_SIGNAL_0)
>> + && sig == TARGET_SIGNAL_0
>> + && !current_inferior()->waiting_for_vfork_done)
>
> Space before parens.
>
Fixed.

--
Yao Qi
CodeSourcery
yao@codesourcery.com
(650) 331-3385 x739

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2010-09-02 Yao Qi <yao@codesourcery.com>

* infrunc(resume): When inferior is waiting_for_vfork_done,
clear step and don't use displaced stepping.

diff --git a/gdb/infrun.c b/gdb/infrun.c
index dd89e78..9d40f7c 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -1550,6 +1550,19 @@ resume (int step, enum target_signal sig)

QUIT;

+ /* Don't consider single-stepping when the inferior is
+ waiting_for_vfork_done, either software or hardware step. In
+ software step, child process will hit the software single step
+ breakpoint inserted in parent process. In hardware step, GDB
+ can resumes inferior, and wait for vfork_done event. */
+ if (current_inferior ()->waiting_for_vfork_done)
+ {
+ if (debug_infrun)
+ fprintf_unfiltered (gdb_stdlog,
+ "infrun: resume : clear step\n");
+ step = 0;
+ }
+
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog,
"infrun: resume (step=%d, signal=%d), "
@@ -1577,11 +1590,16 @@ a command like `return' or `jump' to continue execution."));
We can't use displaced stepping when we have a signal to deliver;
the comments for displaced_step_prepare explain why. The
comments in the handle_inferior event for dealing with 'random
- signals' explain what we do instead. */
+ signals' explain what we do instead.
+
+ We can't use displaced stepping when we are waiting for vfork_done
+ event, displaced stepping breaks the vfork child similarly as single
+ step software breakpoint. */
if (use_displaced_stepping (gdbarch)
&& (tp->trap_expected
|| (step && gdbarch_software_single_step_p (gdbarch)))
- && sig == TARGET_SIGNAL_0)
+ && sig == TARGET_SIGNAL_0
+ && !current_inferior ()->waiting_for_vfork_done)
{
struct displaced_step_inferior_state *displaced;