[PATCH 02/16] powerpc: override __ALIGN() and __ALIGN_STR() macros
Sathvika Vasireddy
sv at linux.vnet.ibm.com
Thu Aug 18 20:46:47 AEST 2022
Hi Christophe,
On 10/08/22 14:01, Christophe Leroy wrote:
>
> Le 08/08/2022 à 13:48, Sathvika Vasireddy a écrit :
>> Since we need an alignment of 4 bytes, override
>> __ALIGN() and __ALIGN_STR() accordingly.
> Why/When do we now need an alignment of 4 bytes ? Please explain the
> reason in the commit message.
Powerpc instructions must be word-aligned. Currently, there is an
alignment of 16 bytes (by default),
and it is much more than what is required for powerpc (4 bytes).
The default expansion of these macros are:
#define __ALIGN .align 4,0x90
#define __ALIGN_STR ".align 4,0x90"
Since Powerpc Linux does not require a 16 byte alignment, override
_ALIGN() and __ALIGN_STR() macros
to use required 4 byte alignment.
Sure, I'll explain the reason in commit message.
>
>> Signed-off-by: Sathvika Vasireddy <sv at linux.ibm.com>
>> ---
>> arch/powerpc/include/asm/linkage.h | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/linkage.h b/arch/powerpc/include/asm/linkage.h
>> index b71b9582e754..8df88fe61438 100644
>> --- a/arch/powerpc/include/asm/linkage.h
>> +++ b/arch/powerpc/include/asm/linkage.h
>> @@ -2,8 +2,12 @@
>> #ifndef _ASM_POWERPC_LINKAGE_H
>> #define _ASM_POWERPC_LINKAGE_H
>>
>> +#include <linux/stringify.h>
>> #include <asm/types.h>
>>
>> +#define __ALIGN .align 2
>> +#define __ALIGN_STR __stringify(__ALIGN)
> Why do you need to use __stringify ?
>
> ARM64 does:
>
> #define __ALIGN .align 2
> #define __ALIGN_STR ".align 2"
We could use either __stringify() or quotes, both do the same thing.
While arm64 does ".align 2",
x86 does:
#define __ALIGN .p2align 4, 0x90
#define __ALIGN_STR __stringify(__ALIGN)
>
>
>
>
>> +
>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>> #define cond_syscall(x) \
>> asm ("\t.weak " #x "\n\t.set " #x ", sys_ni_syscall\n" \
Thanks for reviewing!
- Sathvika
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