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From: Sergey Fedorov <serge.fdrv@gmail.com>
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Date: Tue, 3 Nov 2015 12:02:22 +0300
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Subject: Re: [Qemu-devel] [PATCH] target-arm: Fix arm_debug_excp_handler()
 for singlestep enabled
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 02.11.2015 21:28, Peter Maydell wrote:
> On 2 November 2015 at 17:51, Sergey Fedorov <serge.fdrv@gmail.com> wrote:
>> CPU singlestep is done by generating a debug internal exception. Do not
>> raise a real CPU exception in case of singlestepping.
>>
>> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
>> ---
>>  target-arm/op_helper.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
>> index 7929c71..67d9ffb 100644
>> --- a/target-arm/op_helper.c
>> +++ b/target-arm/op_helper.c
>> @@ -909,7 +909,7 @@ 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)) {
>> +        if (cs->singlestep_enabled || cpu_breakpoint_test(cs, pc, BP_GDB)) {
>>              return;
>>          }
> So I think this will mean that if we're gdbstub-single-stepping then
> an architectural breakpoint on the insn we're stepping won't fire.
>
> Does using a test
>
> if (!cpu_breakpoint_test(cs, pc, BP_CPU)) {
>     return;
> }
>
> fix the singlestep bug too? If so I think it would probably be
> preferable.

Actually, it is supposed that gdbstub breakpoints should be handled
before CPU breakpoints. So I think we should rather do this way:

if (cpu_breakpoint_test(cs, pc, BP_GDB) || !cpu_breakpoint_test(cs, pc, BP_CPU)) {
    return;
}


Thanks,
Sergey