[PATCH] powerpc: Fix instruction encoding for lis in ppc_function_entry()

[Naveen N. Rao]

On 2021/03/05 12:37PM, Christophe Leroy wrote:
> 
> 
> Le 04/03/2021 à 03:04, Naveen N. Rao a écrit :
> > 'lis r2,N' is 'addis r2,0,N' and the instruction encoding in the macro
> > LIS_R2 is incorrect (it currently maps to 'addis 0,r2,N'). Fix the same.
> > 
> > Fixes: c71b7eff426fa7 ("powerpc: Add ABIv2 support to ppc_function_entry")
> > Reported-by: Jiri Olsa <jolsa at redhat.com>
> > Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> > ---
> >   arch/powerpc/include/asm/code-patching.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
> > index eacc9102c2515c..d5b3c3bb95b400 100644
> > --- a/arch/powerpc/include/asm/code-patching.h
> > +++ b/arch/powerpc/include/asm/code-patching.h
> > @@ -73,7 +73,7 @@ void __patch_exception(int exc, unsigned long addr);
> >   #endif
> >   #define OP_RT_RA_MASK	0xffff0000UL
> > -#define LIS_R2		0x3c020000UL
> > +#define LIS_R2		0x3c400000UL
> >   #define ADDIS_R2_R12	0x3c4c0000UL
> >   #define ADDI_R2_R2	0x38420000UL
> 
> That probably goes beyond the scope of this patch, but it would be more
> readable and less error prone to use macros defined in ppc-opcode.h just
> like kernel/module_64.c does for instance:
> 
> #define LIS_R2	(PPC_INST_ADDIS | __PPC_RT(R2))
> #define ADDIS_R2_R12	(PPC_INST_ADDIS | __PPC_RT(R2) | __PPC_RA(R12))
> #define ADDI_R2_R2	(PPC_INST_ADDI | __PPC_RT(R2) | __PPC_RA(R2))

Good point. While that would have made it harder to spot the error, it 
probably would have avoided the error in the first place.

Your change looks good to me.

Thanks,
Naveen