Re: [Qemu-devel] [PATCH v2] target-arm: Fix non-CPU breakpoint handling in arm_debug_excp_handler()

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 06.11.2015 14:57, Peter Maydell wrote:
> On 5 November 2015 at 12:26, Sergey Fedorov <serge.fdrv@gmail.com> wrote:
>> Do not raise a CPU exception if no CPU breakpoint has fired, since
>> singlestep is also done by generating a debug internal exception. This
>> fixes a bug with singlestepping in gdbstub.
>>
>> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
>> ---
>> This is a v2 of 'target-arm: Fix arm_debug_excp_handler() for singlestep
>> enabled.'
>>
>> Changes in v2:
>>  * Commit subject and body changed
>>  * Instead of checking for singlestep enabled, CPU breakpoint match checked
> Isn't this fixing singlestep, not non-CPU breakpoints?
> (GDB breakpoints were already being checked for and early-returned.)

Sorry for the confusing commit subject, actually, I meant "fix handling
of EXCP_DEBUG in case of no CPU breakpoint fired" :)

>
> I'll tweak the commit subject line and apply to target-arm.next.
>
> Incidentally, this only affects gdbstub singlestep for aarch64
> in practice, because gdb for 32-bit ARM uses set-breakpoint-and-continue
> rather than the singlestep gdbstub protocol command.
>
>>  target-arm/op_helper.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
>> index b5db345..6cd54c8 100644
>> --- a/target-arm/op_helper.c
>> +++ b/target-arm/op_helper.c
>> @@ -917,7 +917,13 @@ void arm_debug_excp_handler(CPUState *cs)
>>          uint64_t pc = is_a64(env) ? env->pc : env->regs[15];
>>          bool same_el = (arm_debug_target_el(env) == arm_current_el(env));
>>
>> -        if (cpu_breakpoint_test(cs, pc, BP_GDB)) {
>> +        /* (1) GDB breakpoints should be handled first.
>> +         * (2) Do not raise a CPU exception if no CPU breakpoint has fired,
>> +         * since singlestep is also done by generating a debug internal
>> +         * exception.
>> +         */
>> +        if (cpu_breakpoint_test(cs, pc, BP_GDB)
>> +            || !cpu_breakpoint_test(cs, pc, BP_CPU)) {
>>              return;
>>          }
>>
>> --
>> 1.9.1
>>
>

Thanks,
Sergey