Re: [PATCH] powerpc: Allow relative pointers in bug table entries

[Michael Ellerman <mpe@ellerman.id.au>]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> Le 27/11/2020 à 04:02, Jordan Niethe a écrit :
>> This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
>> offsets are stored in the bug entries rather than 64-bit pointers.
>> 
>> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
>> ---
>>   arch/powerpc/Kconfig           |  4 ++++
>>   arch/powerpc/include/asm/bug.h | 37 ++++++++++++++++++++++++++++++++--
>>   arch/powerpc/xmon/xmon.c       | 17 ++++++++++++++--
>>   3 files changed, 54 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index e9f13fe08492..294108e0e5c6 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -311,6 +311,10 @@ config GENERIC_BUG
>>   	default y
>>   	depends on BUG
>>   
>> +config GENERIC_BUG_RELATIVE_POINTERS
>> +	def_bool y
>> +	depends on GENERIC_BUG
>> +
>>   config SYS_SUPPORTS_APM_EMULATION
>>   	default y if PMAC_APM_EMU
>>   	bool
>> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
>> index 338f36cd9934..d03d834042a1 100644
>> --- a/arch/powerpc/include/asm/bug.h
>> +++ b/arch/powerpc/include/asm/bug.h
>> @@ -12,7 +12,11 @@
>>   #ifdef CONFIG_DEBUG_BUGVERBOSE
>>   .macro EMIT_BUG_ENTRY addr,file,line,flags
>>   	 .section __bug_table,"aw"
>> +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
>
> As far as I understand, as soon as CONFIG_BUG is selected, GENERIC_BUG is automatically selected so 
> GENERIC_BUG_RELATIVE_POINTERS is selected as well. Therefore this #ifndef is never possible.

Yeah.

There is one place in the generic code that has an ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
but that's because it has to support arches that don't select it.

In the arch code we know that it's enabled, so there should be no need
for any ifdefs.

cheers