linux-kernel - Re: [PATCH 1/2] Move the pt_regs_offset struct definition from arch to common include file

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Date:	Wed, 17 Jun 2015 14:30:40 -0400
From:	David Long <dave.long@...aro.org>
To:	Rob Herring <robherring2@...il.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Anton Blanchard <anton@...ba.org>,
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	Martin Schwidefsky <schwidefsky@...ibm.com>,
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Subject: Re: [PATCH 1/2] Move the pt_regs_offset struct definition from arch
 to common include file

On 06/16/15 09:17, Rob Herring wrote:
> On Mon, Jun 15, 2015 at 11:42 AM, David Long <dave.long@...aro.org> wrote:
>> From: "David A. Long" <dave.long@...aro.org>
>>
>> The pt_regs_offset structure is used for HAVE_REGS_AND_STACK_ACCESS_API
>>   feature and has identical definitions in four different arch ptrace.h
>> include files. It seems unlikely that definition would ever need to be
>> changed regardless of architecture so lets move it into
>> include/linux/ptrace.h.
>>
>> Signed-off-by: David A. Long <dave.long@...aro.org>
>> ---
>>   arch/arm/kernel/ptrace.c     | 5 -----
>>   arch/powerpc/kernel/ptrace.c | 5 -----
>>   arch/sh/include/asm/ptrace.h | 5 -----
>>   arch/x86/kernel/ptrace.c     | 5 -----
>>   include/linux/ptrace.h       | 9 +++++++++
>>   5 files changed, 9 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
>> index ef9119f..fb45cf1 100644
>> --- a/arch/arm/kernel/ptrace.c
>> +++ b/arch/arm/kernel/ptrace.c
>> @@ -59,11 +59,6 @@
>>   #define BREAKINST_THUMB        0xde01
>>   #endif
>>
>> -struct pt_regs_offset {
>> -       const char *name;
>> -       int offset;
>> -};
>> -
>>   #define REG_OFFSET_NAME(r) \
>>          {.name = #r, .offset = offsetof(struct pt_regs, ARM_##r)}
>>   #define REG_OFFSET_END {.name = NULL, .offset = 0}
>
> Can't you also move these? ARM is complicated with the "ARM_"
> prefixing, but the others appear to be the same. Maybe you can remove
> the prefix or redefine the macro for ARM.
>
> Rob
>

That would mandate that all the architecture-specific pt_regs structures 
would have to use a top-level named field for each named register.  That 
seems to me like an unnecessary restriction when the point of 
regs_offset_table is to provide the offset of the register inside an 
arbitarily complex pt_regs struct.  The often redundant definition of 
these two macros doesn't seem to me that high a price for that.

-dl

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