Re: [PATCH v5 05/23] target/ppc: Move single-step check to ppc_tr_tb_stop

[David Gibson]

On Mon, May 17, 2021 at 05:50:07PM -0300, matheus.ferst@eldorado.org.br wrote:
> From: Richard Henderson <richard.henderson@linaro.org>
> 
> When single-stepping, force max_insns to 1 in init_disas
> so that we exit the translation loop immediately.
> 
> Combine the single-step checks in tb_stop, and give the
> gdb exception priority over the cpu exception, just as
> we already do in gen_lookup_and_goto_ptr.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>

Applied to ppc-for-6.1, thanks.

> ---
>  target/ppc/translate.c | 33 +++++++++++++++++++--------------
>  1 file changed, 19 insertions(+), 14 deletions(-)
> 
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 80cd11b3f8..05e3c0417a 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -8992,7 +8992,6 @@ static void ppc_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>      DisasContext *ctx = container_of(dcbase, DisasContext, base);
>      CPUPPCState *env = cs->env_ptr;
>      uint32_t hflags = ctx->base.tb->flags;
> -    int bound;
>  
>      ctx->spr_cb = env->spr_cb;
>      ctx->pr = (hflags >> HFLAGS_PR) & 1;
> @@ -9032,8 +9031,12 @@ static void ppc_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>          ctx->singlestep_enabled |= GDBSTUB_SINGLE_STEP;
>      }
>  
> -    bound = -(ctx->base.pc_first | TARGET_PAGE_MASK) / 4;
> -    ctx->base.max_insns = MIN(ctx->base.max_insns, bound);
> +    if (ctx->singlestep_enabled & (CPU_SINGLE_STEP | GDBSTUB_SINGLE_STEP)) {
> +        ctx->base.max_insns = 1;
> +    } else {
> +        int bound = -(ctx->base.pc_first | TARGET_PAGE_MASK) / 4;
> +        ctx->base.max_insns = MIN(ctx->base.max_insns, bound);
> +    }
>  }
>  
>  static void ppc_tr_tb_start(DisasContextBase *db, CPUState *cs)
> @@ -9087,14 +9090,6 @@ static void ppc_tr_translate_insn(DisasContextBase 
> *dcbase, CPUState *cs)
>      handler->count++;
>  #endif
>  
> -    /* Check trace mode exceptions */
> -    if (unlikely(ctx->singlestep_enabled & CPU_SINGLE_STEP &&
> -                 (ctx->base.pc_next <= 0x100 || ctx->base.pc_next > 0xF00) &&
> -                 ctx->base.is_jmp != DISAS_NORETURN)) {
> -        uint32_t excp = gen_prep_dbgex(ctx);
> -        gen_exception_nip(ctx, excp, ctx->base.pc_next);
> -    }
> -
>      if (tcg_check_temp_count()) {
>          qemu_log("Opcode %02x %02x %02x %02x (%08x) leaked "
>                   "temporaries\n", opc1(ctx->opcode), opc2(ctx->opcode),
> @@ -9107,6 +9102,7 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, 
> CPUState *cs)
>      DisasContext *ctx = container_of(dcbase, DisasContext, base);
>      DisasJumpType is_jmp = ctx->base.is_jmp;
>      target_ulong nip = ctx->base.pc_next;
> +    int sse;
>  
>      if (is_jmp == DISAS_NORETURN) {
>          /* We have already exited the TB. */
> @@ -9114,7 +9110,8 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, 
> CPUState *cs)
>      }
>  
>      /* Honor single stepping. */
> -    if (unlikely(ctx->base.singlestep_enabled)) {
> +    sse = ctx->singlestep_enabled & (CPU_SINGLE_STEP | GDBSTUB_SINGLE_STEP);
> +    if (unlikely(sse)) {
>          switch (is_jmp) {
>          case DISAS_TOO_MANY:
>          case DISAS_EXIT_UPDATE:
> @@ -9127,8 +9124,16 @@ static void ppc_tr_tb_stop(DisasContextBase *dcbase, 
> CPUState *cs)
>          default:
>              g_assert_not_reached();
>          }
> -        gen_debug_exception(ctx);
> -        return;
> +
> +        if (sse & GDBSTUB_SINGLE_STEP) {
> +            gen_debug_exception(ctx);
> +            return;
> +        }
> +        /* else CPU_SINGLE_STEP... */
> +        if (nip <= 0x100 || nip > 0xf00) {
> +            gen_exception(ctx, gen_prep_dbgex(ctx));
> +            return;
> +        }
>      }
>  
>      switch (is_jmp) {

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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