[edk2] ArmPkg/DefaultExceptionHandlerLib ARM: avoid endless loop in RELEASE builds

Message ID 20181211132510.21359-1-ard.biesheuvel@linaro.org
State New
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Series
  • [edk2] ArmPkg/DefaultExceptionHandlerLib ARM: avoid endless loop in RELEASE builds
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Commit Message

Ard Biesheuvel Dec. 11, 2018, 1:25 p.m.
Ensure that we prevent the CPU from proceeding after having taken an
unhandled exception on a RELEASE build, which does not contain the
ASSERT() which ensures this on DEBUG and NOOPT builds.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

---
 ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c | 5 +++++
 1 file changed, 5 insertions(+)

-- 
2.19.2

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Comments

Leif Lindholm Dec. 11, 2018, 2:03 p.m. | #1
On Tue, Dec 11, 2018 at 02:25:10PM +0100, Ard Biesheuvel wrote:
> Ensure that we prevent the CPU from proceeding after having taken an

> unhandled exception on a RELEASE build, which does not contain the

> ASSERT() which ensures this on DEBUG and NOOPT builds.


Sounds like a good idea.
Some silly questions below:

> Contributed-under: TianoCore Contribution Agreement 1.1

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---

>  ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c | 5 +++++

>  1 file changed, 5 insertions(+)

> 

> diff --git a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> index 0b9da031b47d..9d96d5aabd96 100644

> --- a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> +++ b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> @@ -267,10 +267,15 @@ DefaultExceptionHandler (

>    DEBUG ((EFI_D_ERROR, "\n"));

>    ASSERT (FALSE);

>  

> +  if (!PcAdjust) {


Won't this always be 0 for a RELEASE build? (By convention if nothing else.)
And won't we already have ASSERTed in any other case?

> +    CpuDeadLoop ();

> +  }

> +

>    // Clear the error registers that we have already displayed incase some one wants to keep going

>    SystemContext.SystemContextArm->DFSR = 0;

>    SystemContext.SystemContextArm->IFSR = 0;

>  

>    // If some one is stepping past the exception handler adjust the PC to point to the next instruction

>    SystemContext.SystemContextArm->PC += PcAdjust;

> +


Hmm?

/
    Leif

>  }

> -- 

> 2.19.2

> 

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Ard Biesheuvel Dec. 11, 2018, 2:06 p.m. | #2
On Tue, 11 Dec 2018 at 15:03, Leif Lindholm <leif.lindholm@linaro.org> wrote:
>

> On Tue, Dec 11, 2018 at 02:25:10PM +0100, Ard Biesheuvel wrote:

> > Ensure that we prevent the CPU from proceeding after having taken an

> > unhandled exception on a RELEASE build, which does not contain the

> > ASSERT() which ensures this on DEBUG and NOOPT builds.

>

> Sounds like a good idea.

> Some silly questions below:

>

> > Contributed-under: TianoCore Contribution Agreement 1.1

> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> > ---

> >  ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c | 5 +++++

> >  1 file changed, 5 insertions(+)

> >

> > diff --git a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> > index 0b9da031b47d..9d96d5aabd96 100644

> > --- a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> > +++ b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c

> > @@ -267,10 +267,15 @@ DefaultExceptionHandler (

> >    DEBUG ((EFI_D_ERROR, "\n"));

> >    ASSERT (FALSE);

> >

> > +  if (!PcAdjust) {

>

> Won't this always be 0 for a RELEASE build? (By convention if nothing else.)

> And won't we already have ASSERTed in any other case?

>


Yeah. I had it in my mind that you could set PcAdjust from the
debugger, but that doesn't really fly given that the optimizer will
just get rid of it in a RELEASE build, and you'd hit the ASSERT()
otherwise.



> > +    CpuDeadLoop ();

> > +  }

> > +

> >    // Clear the error registers that we have already displayed incase some one wants to keep going

> >    SystemContext.SystemContextArm->DFSR = 0;

> >    SystemContext.SystemContextArm->IFSR = 0;

> >

> >    // If some one is stepping past the exception handler adjust the PC to point to the next instruction

> >    SystemContext.SystemContextArm->PC += PcAdjust;

> > +

>

> Hmm?

>


Oops.
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Patch

diff --git a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
index 0b9da031b47d..9d96d5aabd96 100644
--- a/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
+++ b/ArmPkg/Library/DefaultExceptionHandlerLib/Arm/DefaultExceptionHandler.c
@@ -267,10 +267,15 @@  DefaultExceptionHandler (
   DEBUG ((EFI_D_ERROR, "\n"));
   ASSERT (FALSE);
 
+  if (!PcAdjust) {
+    CpuDeadLoop ();
+  }
+
   // Clear the error registers that we have already displayed incase some one wants to keep going
   SystemContext.SystemContextArm->DFSR = 0;
   SystemContext.SystemContextArm->IFSR = 0;
 
   // If some one is stepping past the exception handler adjust the PC to point to the next instruction
   SystemContext.SystemContextArm->PC += PcAdjust;
+
 }