Re: [Xen-devel] [PATCH for-4.5] xen/arm: Correct the opcode for BUG_INSTR on arm32

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-12-04 at 14:34 -0500, Konrad Rzeszutek Wilk wrote:
> On Thu, Dec 04, 2014 at 07:26:55PM +0000, Julien Grall wrote:
> > A 0 was forgotten when the arm32 BUG instruction opcode has been added in 
> > commit
> > 3e802c6ca1fb9a9549258c2855a57cad483f3cbd "xen/arm: Correctly support 
> > WARN_ON".
> > 
> > This will result to use a valid instruction (mcreq 0, 3, r0, cr15, cr0, 
> > {7}),
> > and inhibit usage of BUG/WARN_ON and co.

Doh!

> > 
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > 
> > ---
> > 
> > Not sure, why I dropped the 0 when I implemented the patch...
> > This is a bug fixed for Xen 4.5. This is only affected ARM32 where the
> > BUG opcode was malformed.
> > 
> > With the malformed opcode, the ASSERT/BUG_ON is skipped and the
> > processor may execute another patch (because the compiler has optimized
> 
> s/patch/path/ ?

Will fix on commit.

> > due the unreachable in both macro).
> > 
> > The code modified is only executed when Xen is in bad state.
> 
> Release-Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

> 
> > ---
> >  xen/include/asm-arm/arm32/bug.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/xen/include/asm-arm/arm32/bug.h 
> > b/xen/include/asm-arm/arm32/bug.h
> > index 155b420..3e66f35 100644
> > --- a/xen/include/asm-arm/arm32/bug.h
> > +++ b/xen/include/asm-arm/arm32/bug.h
> > @@ -6,7 +6,7 @@
> >  /* ARMv7 provides a list of undefined opcode (see A8.8.247 DDI 0406C.b)
> >   * Use one them encoding A1 to go in exception mode
> >   */
> > -#define BUG_OPCODE  0xe7f00f0
> > +#define BUG_OPCODE  0xe7f000f0
> >  
> >  #define BUG_INSTR ".word " __stringify(BUG_OPCODE)
> >  
> > -- 
> > 2.1.3
> > 
> 
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