linux-kernel - Re: [PATCH V2 1/2] riscv: stack: Fixup independent irq stack for CONFIG_FRAME

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Message-ID: <5540704.q0sY26EuUQ@basile.remlab.net>
Date:   Sun, 16 Jul 2023 11:14:40 +0300
From:   Rémi Denis-Courmont <remi@...lab.net>
To:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] riscv: stack: Fixup independent irq stack for
 CONFIG_FRAME_POINTER=n

Le sunnuntaina 16. heinäkuuta 2023, 3.15.05 EEST guoren@...nel.org a écrit :
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> The independent irq stack uses s0 to save & restore sp, but s0 would be
> corrupted when CONFIG_FRAME_POINTER=n. So add s0 in the clobber list to
> fix the problem.

Isn't it *always* corrupted? Shouldn't the clobber be always there? Am I 
guessing that the compiler whine that you can't mark the frame pointer as 
clobbered? If so, it would be worth mentioning in the commit log, IMO.

> Fixes: 163e76cc6ef4 ("riscv: stack: Support HAVE_IRQ_EXIT_ON_IRQ_STACK")
> Cc: stable@...r.kernel.org
> Reported-by: Zhangjin Wu <falcon@...ylab.org>
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>
> ---
>  arch/riscv/kernel/traps.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index f910dfccbf5d..927347a19847 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -372,6 +372,9 @@ asmlinkage void noinstr do_irq(struct pt_regs *regs)
> 
>  		: [sp] "r" (sp), [regs] "r" (regs)
>  		: "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7",
> 
>  		  "t0", "t1", "t2", "t3", "t4", "t5", "t6",
> +#ifndef CONFIG_FRAME_POINTER
> +		  "s0",
> +#endif
>  		  "memory");
>  	} else
>  #endif


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