Re: [PATCH v2 10/11] mips: Implement setjmp/longjmp/initjmp

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Peter,

On 07.03.21 13:00, Peter Mamonov wrote:
> On Thu, Mar 04, 2021 at 09:38:11AM +0100, Sascha Hauer wrote:
>> Hi Peter,
>>
>> On Wed, Mar 03, 2021 at 01:19:26AM +0300, Peter Mamonov wrote:
>>> Hi, Sascha and Ahmad,
>>>
>>> On Mon, Mar 01, 2021 at 12:01:05PM +0100, Ahmad Fatoum wrote:
>>>> From: Sascha Hauer <s.hauer@pengutronix.de>
>>>>
>>>> The header has been taken from glibc, the implementation itself is based
>>>> on the newlib implementation.
>>>>
>>>> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>>>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>>>> ---
>>>>  arch/mips/Kconfig              |  1 +
>>>>  arch/mips/include/asm/setjmp.h | 32 ++++++++++++++++++++++
>>>>  arch/mips/lib/Makefile         |  1 +
>>>>  arch/mips/lib/setjmp.S         | 50 ++++++++++++++++++++++++++++++++++
>>>>  4 files changed, 84 insertions(+)
>>>>  create mode 100644 arch/mips/include/asm/setjmp.h
>>>>  create mode 100644 arch/mips/lib/setjmp.S
>>>>
>>>> ...
>>>>
>>>> diff --git a/arch/mips/lib/setjmp.S b/arch/mips/lib/setjmp.S
>>>> new file mode 100644
>>>> index 000000000000..b09a7c55293c
>>>> --- /dev/null
>>>> +++ b/arch/mips/lib/setjmp.S
>>>> @@ -0,0 +1,50 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>>> +
>>>> +#include <asm/regdef.h>
>>>> +#include <asm/asm.h>
>>>> +#include <linux/linkage.h>
>>>> +
>>>> +/* int setjmp (jmp_buf);  */
>>>> +LEAF(setjmp)
>>>> +	sw	ra, (0 * 4)(a0)
>>>> +	sw	sp, (1 * 4)(a0)
>>>> +	sw	s0, (2 * 4)(a0)
>>>> +	sw	s1, (3 * 4)(a0)
>>>> +	sw	s2, (4 * 4)(a0)
>>>> +	sw	s3, (5 * 4)(a0)
>>>> +	sw	s4, (6 * 4)(a0)
>>>> +	sw	s5, (7 * 4)(a0)
>>>> +	sw	s6, (8 * 4)(a0)
>>>> +	sw	s7, (9 * 4)(a0)
>>>> +	sw	fp, (10 * 4)(a0)
>>>> +	move	v0, zero
>>>> +	j	ra
>>>> +END(setjmp)
>>>> +
>>>> +/* volatile void longjmp (jmp_buf, int);  */
>>>> +LEAF(longjmp)
>>>> +	lw	ra, (0 * 4)(a0)
>>>> +	lw	sp, (1 * 4)(a0)
>>>> +	lw	s0, (2 * 4)(a0)
>>>> +	lw	s1, (3 * 4)(a0)
>>>> +	lw	s2, (4 * 4)(a0)
>>>> +	lw	s3, (5 * 4)(a0)
>>>> +	lw	s4, (6 * 4)(a0)
>>>> +	lw	s5, (7 * 4)(a0)
>>>> +	lw	s6, (8 * 4)(a0)
>>>> +	lw	s7, (9 * 4)(a0)
>>>> +	lw	fp, (10 * 4)(a0)
>>>> +	bne	a1, zero, 1f
>>>> +	li	a1, 1
>>>> +1:
>>>> +	move	v0, a1
>>>> +	j	ra
>>>> +END(longjmp)
>>>> +
>>>> +/* int initjmp(jmp_buf jmp, void __noreturn (*func)(void), void *stack_top); */
>>>> +LEAF(initjmp)
>>>> +	sw	a1, (0 * 4)(a0)
>>>> +	sw	a2, (1 * 4)(a0)
>>>> +	move	v0, zero
>>>> +	j	ra
>>>> +END(initjmp)
>>>
>>> I would suggest using `REG_S/REG_L r, (n * SZREG)(a0)` here for the sake of 
>>> MIPS64 targets. See arch/mips/include/asm/asm.h:272.
>>
>> I agree with you, but barebox doesn't support MIPS64 currently and I
>> wasn't confident enough to add such things when I can't test them.
> 
> Well, what can possibly go wrong? =) Actually you've used this approach for RV: 
> http://lists.infradead.org/pipermail/barebox/2021-March/035173.html.
> 
>> Maybe we can add a
>>
>> #if SZREG != 4
>> #error setjmp/longjmp currently only supports 32bit targets
>> #endif
> 
> Definitely it's better than random fails after context switch in runtime.

I changed the select to happen only from the 32-bit symbols for RISC-V and MIPS.

> 
> Regards,
> Peter
> 
>> Sascha
>>> -- > Pengutronix e.K.                           |                             
> |
>> Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
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> 

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
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