Re: [PATCH 10/13] gdbstub: add reverse step support in replay mode

[Alex Bennée]

Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru> writes:

> From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
>
> GDB remote protocol supports two reverse debugging commands:
> reverse step and reverse continue.
> This patch adds support of the first one to the gdbstub.
> Reverse step is intended to step one instruction in the backwards
> direction. This is not possible in regular execution.
> But replayed execution is deterministic, therefore we can load one of
> the prior snapshots and proceed to the desired step. It is equivalent
> to stepping one instruction back.
> There should be at least one snapshot preceding the debugged part of
> the replay log.
>
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
> ---
>  0 files changed
>
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 603d17ff83..fb1e19c585 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -17,6 +17,7 @@
>  #include "exec/log.h"
>  #include "exec/translator.h"
>  #include "exec/plugin-gen.h"
> +#include "sysemu/replay.h"
>  
>  /* Pairs with tcg_clear_temp_count.
>     To be called by #TranslatorOps.{translate_insn,tb_stop} if
> diff --git a/cpus.c b/cpus.c
> index 41d1c5099f..35381ea941 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -1100,9 +1100,17 @@ static bool cpu_can_run(CPUState *cpu)
>  
>  static void cpu_handle_guest_debug(CPUState *cpu)
>  {
> -    gdb_set_stop_cpu(cpu);
> -    qemu_system_debug_request();
> -    cpu->stopped = true;
> +    if (!replay_running_debug()) {
> +        gdb_set_stop_cpu(cpu);
> +        qemu_system_debug_request();
> +        cpu->stopped = true;
> +    } else {
> +        if (!cpu->singlestep_enabled) {
> +            cpu_single_step(cpu, SSTEP_ENABLE);
> +        } else {
> +            cpu_single_step(cpu, 0);
> +        }
> +    }

This no longer applies cleanly.

-- 
Alex Bennée