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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 2 Nov 2015 18:28:38 +0000
Message-ID: <CAFEAcA8iUzhRhCfYtFiZOpKpS-udqRFGmOX-TXLV_OAWH5tdxA@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] target-arm: Fix arm_debug_excp_handler()
	for singlestep enabled
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To: Sergey Fedorov <serge.fdrv@gmail.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>

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.

thanks
-- PMM