Patchwork Fix missing TRACE exception

login
register
mail settings
Submitter Julio Guerra
Date Oct. 19, 2012, 10:17 a.m.
Message ID <CAFAwnGMTjFUMgbB_sWxZz2_3CwhrMkvjGmkGGpyeZ_4u=dtRhQ@mail.gmail.com>
Download mbox | patch
Permalink /patch/192635/
State New
Headers show

Comments

Julio Guerra - Oct. 19, 2012, 10:17 a.m.
This patch fixes bug 1031698 :
https://bugs.launchpad.net/qemu/+bug/1031698

If we look at the (truncated) translation of the conditional branch
instruction in the test submitted in the bug post, the call to the
exception helper is missing in the "bne-false" chunk of translated
code :

IN:
bne-    0x1800278

OUT:
0xb544236d:  jne    0xb5442396

0xb5442373:  mov    %ebp,(%esp)
0xb5442376:  mov    $0x44,%ebx
0xb544237b:  mov    %ebx,0x4(%esp)
0xb544237f:  mov    $0x1800278,%ebx
0xb5442384:  mov    %ebx,0x25c(%ebp)
0xb544238a:  call   0x827475a
                     ^^^^^^^^^^^^^^^^^^
# OK : call the exception helper function

0xb5442396:  mov    %ebp,(%esp)
0xb5442399:  mov    $0x44,%ebx
0xb544239e:  mov    %ebx,0x4(%esp)
0xb54423a2:  mov    $0x1800270,%ebx
0xb54423a7:  mov    %ebx,0x25c(%ebp)
# KO : missing "call 0x827475a"


Indeed, gen_exception(ctx, excp) called by gen_goto_tb (called by
gen_bcond) changes ctx->exception's value to excp's :

gen_bcond()
{
  gen_goto_tb(ctx, 0, ctx->nip + li - 4);
  /* ctx->exception value is POWERPC_EXCP_BRANCH */

  gen_goto_tb(ctx, 1, ctx->nip);
  /* ctx->exception now value is POWERPC_EXCP_TRACE */
}


Making the following gen_goto_tb()'s test false during the second call :

if ((ctx->singlestep_enabled &
    (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
    ctx->exception == POWERPC_EXCP_BRANCH /* false...*/) {
         target_ulong tmp = ctx->nip;
         ctx->nip = dest;
         /* ... and this is the missing call */
         gen_exception(ctx, POWERPC_EXCP_TRACE);
         ctx->nip = tmp;
}

So the patch simply adds the missing matching case, fixing our problem.

Signed-off-by: Julio Guerra <guerr@julio.in>
---
 target-ppc/translate.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
Julio Guerra - Nov. 22, 2012, 9:26 a.m.
2012/10/19 Julio Guerra <guerr@julio.in>:
> This patch fixes bug 1031698 :
> https://bugs.launchpad.net/qemu/+bug/1031698
>
> If we look at the (truncated) translation of the conditional branch
> instruction in the test submitted in the bug post, the call to the
> exception helper is missing in the "bne-false" chunk of translated
> code :
>
> IN:
> bne-    0x1800278
>
> OUT:
> 0xb544236d:  jne    0xb5442396
>
> 0xb5442373:  mov    %ebp,(%esp)
> 0xb5442376:  mov    $0x44,%ebx
> 0xb544237b:  mov    %ebx,0x4(%esp)
> 0xb544237f:  mov    $0x1800278,%ebx
> 0xb5442384:  mov    %ebx,0x25c(%ebp)
> 0xb544238a:  call   0x827475a
>                      ^^^^^^^^^^^^^^^^^^
> # OK : call the exception helper function
>
> 0xb5442396:  mov    %ebp,(%esp)
> 0xb5442399:  mov    $0x44,%ebx
> 0xb544239e:  mov    %ebx,0x4(%esp)
> 0xb54423a2:  mov    $0x1800270,%ebx
> 0xb54423a7:  mov    %ebx,0x25c(%ebp)
> # KO : missing "call 0x827475a"
>
>
> Indeed, gen_exception(ctx, excp) called by gen_goto_tb (called by
> gen_bcond) changes ctx->exception's value to excp's :
>
> gen_bcond()
> {
>   gen_goto_tb(ctx, 0, ctx->nip + li - 4);
>   /* ctx->exception value is POWERPC_EXCP_BRANCH */
>
>   gen_goto_tb(ctx, 1, ctx->nip);
>   /* ctx->exception now value is POWERPC_EXCP_TRACE */
> }
>
>
> Making the following gen_goto_tb()'s test false during the second call :
>
> if ((ctx->singlestep_enabled &
>     (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
>     ctx->exception == POWERPC_EXCP_BRANCH /* false...*/) {
>          target_ulong tmp = ctx->nip;
>          ctx->nip = dest;
>          /* ... and this is the missing call */
>          gen_exception(ctx, POWERPC_EXCP_TRACE);
>          ctx->nip = tmp;
> }
>
> So the patch simply adds the missing matching case, fixing our problem.
>
> Signed-off-by: Julio Guerra <guerr@julio.in>
> ---
>  target-ppc/translate.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff -up a/target-ppc/translate.c b/target-ppc/translate.c
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -3466,7 +3466,8 @@ static inline void gen_goto_tb(DisasCont
>          if (unlikely(ctx->singlestep_enabled)) {
>              if ((ctx->singlestep_enabled &
>                  (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
> -                ctx->exception == POWERPC_EXCP_BRANCH) {
> +                (ctx->exception == POWERPC_EXCP_BRANCH ||
> +                 ctx->exception == POWERPC_EXCP_TRACE)) {
>                  target_ulong tmp = ctx->nip;
>                  ctx->nip = dest;
>                  gen_exception(ctx, POWERPC_EXCP_TRACE);


ping

--
Julio Guerra
Alexander Graf - Nov. 23, 2012, 4:06 p.m.
On 19.10.2012, at 12:17, Julio Guerra wrote:

> This patch fixes bug 1031698 :
> https://bugs.launchpad.net/qemu/+bug/1031698
> 
> If we look at the (truncated) translation of the conditional branch
> instruction in the test submitted in the bug post, the call to the
> exception helper is missing in the "bne-false" chunk of translated
> code :
> 
> IN:
> bne-    0x1800278
> 
> OUT:
> 0xb544236d:  jne    0xb5442396
> 
> 0xb5442373:  mov    %ebp,(%esp)
> 0xb5442376:  mov    $0x44,%ebx
> 0xb544237b:  mov    %ebx,0x4(%esp)
> 0xb544237f:  mov    $0x1800278,%ebx
> 0xb5442384:  mov    %ebx,0x25c(%ebp)
> 0xb544238a:  call   0x827475a
>                     ^^^^^^^^^^^^^^^^^^
> # OK : call the exception helper function
> 
> 0xb5442396:  mov    %ebp,(%esp)
> 0xb5442399:  mov    $0x44,%ebx
> 0xb544239e:  mov    %ebx,0x4(%esp)
> 0xb54423a2:  mov    $0x1800270,%ebx
> 0xb54423a7:  mov    %ebx,0x25c(%ebp)
> # KO : missing "call 0x827475a"
> 
> 
> Indeed, gen_exception(ctx, excp) called by gen_goto_tb (called by
> gen_bcond) changes ctx->exception's value to excp's :
> 
> gen_bcond()
> {
>  gen_goto_tb(ctx, 0, ctx->nip + li - 4);
>  /* ctx->exception value is POWERPC_EXCP_BRANCH */
> 
>  gen_goto_tb(ctx, 1, ctx->nip);
>  /* ctx->exception now value is POWERPC_EXCP_TRACE */
> }
> 
> 
> Making the following gen_goto_tb()'s test false during the second call :
> 
> if ((ctx->singlestep_enabled &
>    (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
>    ctx->exception == POWERPC_EXCP_BRANCH /* false...*/) {
>         target_ulong tmp = ctx->nip;
>         ctx->nip = dest;
>         /* ... and this is the missing call */
>         gen_exception(ctx, POWERPC_EXCP_TRACE);
>         ctx->nip = tmp;
> }
> 
> So the patch simply adds the missing matching case, fixing our problem.
> 
> Signed-off-by: Julio Guerra <guerr@julio.in>

Thanks, applied to ppc-next :)

Alex

> ---
> target-ppc/translate.c |    4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff -up a/target-ppc/translate.c b/target-ppc/translate.c
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -3466,7 +3466,8 @@ static inline void gen_goto_tb(DisasCont
>         if (unlikely(ctx->singlestep_enabled)) {
>             if ((ctx->singlestep_enabled &
>                 (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
> -                ctx->exception == POWERPC_EXCP_BRANCH) {
> +                (ctx->exception == POWERPC_EXCP_BRANCH ||
> +                 ctx->exception == POWERPC_EXCP_TRACE)) {
>                 target_ulong tmp = ctx->nip;
>                 ctx->nip = dest;
>                 gen_exception(ctx, POWERPC_EXCP_TRACE);
Andreas Färber - Nov. 23, 2012, 4:35 p.m.
Am 23.11.2012 17:06, schrieb Alexander Graf:
> 
> On 19.10.2012, at 12:17, Julio Guerra wrote:
> 
>> This patch fixes bug 1031698 :
>> https://bugs.launchpad.net/qemu/+bug/1031698
>>
>> If we look at the (truncated) translation of the conditional branch
>> instruction in the test submitted in the bug post, the call to the
>> exception helper is missing in the "bne-false" chunk of translated
>> code :
>>
>> IN:
>> bne-    0x1800278
>>
>> OUT:
>> 0xb544236d:  jne    0xb5442396
>>
>> 0xb5442373:  mov    %ebp,(%esp)
>> 0xb5442376:  mov    $0x44,%ebx
>> 0xb544237b:  mov    %ebx,0x4(%esp)
>> 0xb544237f:  mov    $0x1800278,%ebx
>> 0xb5442384:  mov    %ebx,0x25c(%ebp)
>> 0xb544238a:  call   0x827475a
>>                     ^^^^^^^^^^^^^^^^^^
>> # OK : call the exception helper function
>>
>> 0xb5442396:  mov    %ebp,(%esp)
>> 0xb5442399:  mov    $0x44,%ebx
>> 0xb544239e:  mov    %ebx,0x4(%esp)
>> 0xb54423a2:  mov    $0x1800270,%ebx
>> 0xb54423a7:  mov    %ebx,0x25c(%ebp)
>> # KO : missing "call 0x827475a"
>>
>>
>> Indeed, gen_exception(ctx, excp) called by gen_goto_tb (called by
>> gen_bcond) changes ctx->exception's value to excp's :
>>
>> gen_bcond()
>> {
>>  gen_goto_tb(ctx, 0, ctx->nip + li - 4);
>>  /* ctx->exception value is POWERPC_EXCP_BRANCH */
>>
>>  gen_goto_tb(ctx, 1, ctx->nip);
>>  /* ctx->exception now value is POWERPC_EXCP_TRACE */
>> }
>>
>>
>> Making the following gen_goto_tb()'s test false during the second call :
>>
>> if ((ctx->singlestep_enabled &
>>    (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
>>    ctx->exception == POWERPC_EXCP_BRANCH /* false...*/) {
>>         target_ulong tmp = ctx->nip;
>>         ctx->nip = dest;
>>         /* ... and this is the missing call */
>>         gen_exception(ctx, POWERPC_EXCP_TRACE);
>>         ctx->nip = tmp;
>> }
>>
>> So the patch simply adds the missing matching case, fixing our problem.
>>
>> Signed-off-by: Julio Guerra <guerr@julio.in>
> 
> Thanks, applied to ppc-next :)

Please don't forget to add the missing "target-ppc: ". :)

Andreas

Patch

diff -up a/target-ppc/translate.c b/target-ppc/translate.c
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -3466,7 +3466,8 @@  static inline void gen_goto_tb(DisasCont
         if (unlikely(ctx->singlestep_enabled)) {
             if ((ctx->singlestep_enabled &
                 (CPU_BRANCH_STEP | CPU_SINGLE_STEP)) &&
-                ctx->exception == POWERPC_EXCP_BRANCH) {
+                (ctx->exception == POWERPC_EXCP_BRANCH ||
+                 ctx->exception == POWERPC_EXCP_TRACE)) {
                 target_ulong tmp = ctx->nip;
                 ctx->nip = dest;
                 gen_exception(ctx, POWERPC_EXCP_TRACE);