[PATCH] powerpc/40x: Fix assembler warning about r0

[PATCH] powerpc/40x: Fix assembler warning about r0

[Michael Ellerman]

The assembler says:
  arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression

It's objecting to the use of r0 as the RA argument. That's because
when RA = 0 the literal value 0 is used, rather than the content of
r0, making the use of r0 in the source potentially confusing.

Fix it to use a literal 0, the generated code is identical.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 arch/powerpc/kernel/head_40x.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 926bfa73586a..5b282d9965a5 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -620,7 +620,7 @@ _ENTRY(saved_ksp_limit)
 	ori	r6, r6, swapper_pg_dir@l
 	lis	r5, abatron_pteptrs@h
 	ori	r5, r5, abatron_pteptrs@l
-	stw	r5, 0xf0(r0)	/* Must match your Abatron config file */
+	stw	r5, 0xf0(0)	/* Must match your Abatron config file */
 	tophys(r5,r5)
 	stw	r6, 0(r5)
 
-- 
2.25.1

Re: [PATCH] powerpc/40x: Fix assembler warning about r0

[Michael Ellerman]

On Wed, 22 Jul 2020 12:24:22 +1000, Michael Ellerman wrote:
> The assembler says:
>   arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression
> 
> It's objecting to the use of r0 as the RA argument. That's because
> when RA = 0 the literal value 0 is used, rather than the content of
> r0, making the use of r0 in the source potentially confusing.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/40x: Fix assembler warning about r0
      https://git.kernel.org/powerpc/c/8d8a629d00a5283874b81b594f31f8d436dc57d8

cheers

Re: [PATCH] powerpc/40x: Fix assembler warning about r0

[Christophe Leroy]

Le 22/07/2020 à 04:24, Michael Ellerman a écrit :
> The assembler says:
>    arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression

I get exactly the same with head_32.S, for the exact same reason.

Christophe

> 
> It's objecting to the use of r0 as the RA argument. That's because
> when RA = 0 the literal value 0 is used, rather than the content of
> r0, making the use of r0 in the source potentially confusing.
> 
> Fix it to use a literal 0, the generated code is identical.
> 
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>   arch/powerpc/kernel/head_40x.S | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
> index 926bfa73586a..5b282d9965a5 100644
> --- a/arch/powerpc/kernel/head_40x.S
> +++ b/arch/powerpc/kernel/head_40x.S
> @@ -620,7 +620,7 @@ _ENTRY(saved_ksp_limit)
>   	ori	r6, r6, swapper_pg_dir@l
>   	lis	r5, abatron_pteptrs@h
>   	ori	r5, r5, abatron_pteptrs@l
> -	stw	r5, 0xf0(r0)	/* Must match your Abatron config file */
> +	stw	r5, 0xf0(0)	/* Must match your Abatron config file */
>   	tophys(r5,r5)
>   	stw	r6, 0(r5)
>   
> 

Re: [PATCH] powerpc/40x: Fix assembler warning about r0

[Michael Ellerman]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 22/07/2020 à 04:24, Michael Ellerman a écrit :
>> The assembler says:
>>    arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression
>
> I get exactly the same with head_32.S, for the exact same reason.

Ah yep, I see it. I mostly build pmac32_defconfig which doesn't have
BDI_SWITCH enabled.

Send a patch? :)

Do we still need the BDI_SWITCH code? Is it likely anyone still has one,
that works?

cheers

Re: [PATCH] powerpc/40x: Fix assembler warning about r0

[Christophe Leroy]

Le 06/08/2020 à 04:18, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> Le 22/07/2020 à 04:24, Michael Ellerman a écrit :
>>> The assembler says:
>>>     arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression
>>
>> I get exactly the same with head_32.S, for the exact same reason.
> 
> Ah yep, I see it. I mostly build pmac32_defconfig which doesn't have
> BDI_SWITCH enabled.
> 
> Send a patch? :)

Done.

> 
> Do we still need the BDI_SWITCH code? Is it likely anyone still has one,
> that works?

I have three (One for 83xx and two for 8xx) and they work, allthough I'm 
using them only for Uboot and for very very very early Linux boot 
debugging (Last time I used it with Linux was when implementing KASAN)

Christophe

Re: [PATCH] powerpc/40x: Fix assembler warning about r0

[Michael Ellerman]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 06/08/2020 à 04:18, Michael Ellerman a écrit :
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>>> Le 22/07/2020 à 04:24, Michael Ellerman a écrit :
>>>> The assembler says:
>>>>     arch/powerpc/kernel/head_40x.S:623: Warning: invalid register expression
>>>
>>> I get exactly the same with head_32.S, for the exact same reason.
>> 
>> Ah yep, I see it. I mostly build pmac32_defconfig which doesn't have
>> BDI_SWITCH enabled.
>> 
>> Send a patch? :)
>
> Done.
>
>> 
>> Do we still need the BDI_SWITCH code? Is it likely anyone still has one,
>> that works?
>
> I have three (One for 83xx and two for 8xx) and they work, allthough I'm 
> using them only for Uboot and for very very very early Linux boot 
> debugging (Last time I used it with Linux was when implementing KASAN)

OK, happy to keep the code around if it works and is being used, even
just a little bit.

cheers