Re: [PATCH v2 02/16] powerpc: override __ALIGN() and __ALIGN_STR() macros
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2022-08-31 03:24:58
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On Mon Aug 29, 2022 at 3:52 PM AEST, Sathvika Vasireddy wrote:
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 __ALIGN() macro is: #define __ALIGN .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.
Alignment can be desirable beyond the minimum requirement, for example 16 byte alignment for functions could be helpful for instruction fetch. So it should be explained why possible benefits of the larger alignment are not worth it. And if you have the patch in a series, it should be explained why the patch is required for the series if it is not obvious. Thanks, Nick
quoted hunk ↗ jump to hunk
Signed-off-by: Sathvika Vasireddy <redacted> --- 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) + #ifdef CONFIG_PPC64_ELF_ABI_V1 #define cond_syscall(x) \ asm ("\t.weak " #x "\n\t.set " #x ", sys_ni_syscall\n" \-- 2.31.1