PPC: Fix for the gdb single step problem on an rfi instruction

Submitted by Sebastian Bauer on Aug. 10, 2011, 11:41 a.m.

Details

Message ID 1dff061de511be8246b1e86a63cbf4a8@sebastianbauer.info
State New
Headers show

Commit Message

Sebastian Bauer Aug. 10, 2011, 11:41 a.m.
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>
---
      t0 = tcg_const_i32(EXCP_DEBUG);
      gen_helper_raise_exception(t0);

Comments

Elie Richa Aug. 12, 2011, 1:29 p.m.
Hello,

I've had this problem recently and your patch does fix the issue, thanks!

Regards,
Elie

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);
> t0 = tcg_const_i32(EXCP_DEBUG);
> gen_helper_raise_exception(t0);
>
>
Sebastian Bauer Sept. 14, 2011, 10:57 a.m.
Hi!

On Fri, 12 Aug 2011 15:29:58 +0200, Elie Richa wrote:
> I've had this problem recently and your patch does fix the issue, 
> thanks!

I like to bump this as this was not in the latest ppc patch queue. Is 
there anything wrong with that patch?

TIA

Best,
Sebastian

> 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);
>> t0 = tcg_const_i32(EXCP_DEBUG);
>> gen_helper_raise_exception(t0);
>>
>>

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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);