[PATCH] ARM: asm: Rewrite get_thread_info using BIC

[Dmitry Osipenko]

21.07.2020 16:38, Russell King - ARM Linux admin пишет:
> On Tue, Jul 21, 2020 at 04:37:09PM +0300, Dmitry Osipenko wrote:
>> 27.05.2020 15:22, Linus Walleij пишет:
>>> By using two BIC instructions we can replace the ARM/thumb
>>> split instructions with something that works on either
>>> and also save one instruction.
>>>
>>> Based on code from proc-macros.S and an idea from Ard
>>> Biesheuvel.
>>>
>>> We need to include <linux/const.h> to expand the
>>> THREAD_SIZE definition properly in the preprocessor.
>>>
>>> Suggested-by: Russell King <linux at armlinux.org.uk>
>>> Suggested-by: Ard Biesheuvel <ardb at kernel.org>
>>> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
>>> ---
>>>  arch/arm/include/asm/assembler.h | 7 +++----
>>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
>>> index 99929122dad7..f218e8cf7f88 100644
>>> --- a/arch/arm/include/asm/assembler.h
>>> +++ b/arch/arm/include/asm/assembler.h
>>> @@ -17,6 +17,7 @@
>>>  #error "Only include this from assembly code"
>>>  #endif
>>>  
>>> +#include <linux/const.h>
>>>  #include <asm/ptrace.h>
>>>  #include <asm/domain.h>
>>>  #include <asm/opcodes-virt.h>
>>> @@ -203,10 +204,8 @@
>>>   * Get current thread_info.
>>>   */
>>>  	.macro	get_thread_info, rd
>>> - ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)
>>> - THUMB(	mov	\rd, sp			)
>>> - THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)
>>> -	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
>>> +	bic	\rd, sp, #(THREAD_SIZE - 1) & ~63
>>> +	bic	\rd, \rd, #63
>>>  	.endm
>>>  
>>>  /*
>>>
>>
>> Hello, Linus!
>>
>> This patch was merged into a recent linux-next, unfortunately it breaks
>> CONFIG_THUMB2_KERNEL=y compilation:
>>
>> arch/arm/kernel/entry-common.S: Assembler messages:
>> arch/arm/kernel/entry-common.S:159: Error: r13 not allowed here -- `bic
>> tsk,sp,#(((1<<12)<<1)-1)&~63'
>> arch/arm/kernel/entry-common.S:246: Error: r13 not allowed here -- `bic
>> tsk,sp,#(((1<<12)<<1)-1)&~63'
>> make[2]: *** [scripts/Makefile.build:361:
>> arch/arm/kernel/entry-common.o] Error 1
> 
> I've dropped it before you sent this email...

Hello, Russell!

Good to know, thank you!