Re: [PATCH] replay: fix watchpoint processing for reverse debugging

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

ping

On 11.05.2021 12:11, Pavel Dovgalyuk wrote:
> This patch enables reverse debugging with watchpoints.
> Reverse continue scans the execution to find the breakpoints
> and watchpoints that should fire. It uses helper function
> replay_breakpoint() for that. But this function needs to access
> icount, which can't be correct in the middle of TB.
> Therefore, in case of watchpoint, we have to retranslate the block
> to allow this access.
> 
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
> ---
>   softmmu/physmem.c |   10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index 5232696571..2826d60cef 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -904,6 +904,16 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
>           if (watchpoint_address_matches(wp, addr, len)
>               && (wp->flags & flags)) {
>               if (replay_running_debug()) {
> +                /*
> +                 * replay_breakpoint reads icount.
> +                 * Force recompile to succeed, because icount may
> +                 * be read only at the end of the block.
> +                 */
> +                if (!cpu->can_do_io) {
> +                    /* Force execution of one insn next time.  */
> +                    cpu->cflags_next_tb = 1 | CF_LAST_IO | curr_cflags(cpu);
> +                    cpu_loop_exit_restore(cpu, ra);
> +                }
>                   /*
>                    * Don't process the watchpoints when we are
>                    * in a reverse debugging operation.
>