Re: [Qemu-devel] [PATCH] PPC: Fix for the gdb single step problem on an rfi instruction

[Alexander Graf <agraf@suse.de>]

On 08/10/2011 01:41 PM, Sebastian Bauer wrote:
> When using gdb to single step a ppc interrupt routine, the execution 
> flow passes
> the rfi instruction without actually returning from the interrupt. The 
> patch
> fixes this by avoiding to update the nip when the debug exception is 
> raised
> and a previous POWERPC_EXCP_SYNC was set. The latter is the case only, 
> if code for
> rfi or a related instruction was generated.
>
> Signed-off-by: Sebastian Bauer <mail@sebastianbauer.info>
> ---
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index fd7c208..42b91fd 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -287,7 +287,7 @@ static inline void 
> gen_debug_exception(DisasContext *ctx)
>  {
>      TCGv_i32 t0;
>
> -    if (ctx->exception != POWERPC_EXCP_BRANCH)
> +    if (ctx->exception != POWERPC_EXCP_BRANCH && ctx->exception != 
> POWERPC_EXCP_SYNC)
>          gen_update_nip(ctx, ctx->nip);

I fixed the patch up to align with the coding style rules:


diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 99e995c..66eae30 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -298,8 +298,10 @@ static inline void gen_debug_exception(DisasContext 
*ctx)
  {
      TCGv_i32 t0;

-    if (ctx->exception != POWERPC_EXCP_BRANCH)
+    if ((ctx->exception != POWERPC_EXCP_BRANCH) &&
+        (ctx->exception != POWERPC_EXCP_SYNC)) {
          gen_update_nip(ctx, ctx->nip);
+    }
      t0 = tcg_const_i32(EXCP_DEBUG);
      gen_helper_raise_exception(t0);
      tcg_temp_free_i32(t0);


Otherwise, applied to ppc-next now. Thanks a lot! And sorry for the late 
reply again. Please send your next patch CC'ed to qemu-ppc@nongnu.org - 
that makes it a lot easier for to not lose track of it :).


Alex