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Date:   Sun, 11 Apr 2021 18:09:08 -0700 (PDT)
Subject:     Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception
In-Reply-To: <20210330021624.2b776386@xhacker>
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        guoren@linux.alibaba.com, mhiramat@kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     jszhang3@mail.ustc.edu.cn
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On Mon, 29 Mar 2021 11:16:24 PDT (-0700), jszhang3@mail.ustc.edu.cn wrote:
> From: Jisheng Zhang <jszhang@kernel.org>
>
> Current riscv's kprobe handlers are run with both preemption and
> interrupt enabled, this violates kprobe requirements. Fix this issue
> by keeping interrupts disabled for BREAKPOINT exception.
>
> Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
>  arch/riscv/kernel/entry.S | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 744f3209c48d..4114b65698ec 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -130,6 +130,8 @@ skip_context_tracking:
>  	 */
>  	andi t0, s1, SR_PIE
>  	beqz t0, 1f
> +	li t0, EXC_BREAKPOINT
> +	beq s4, t0, 1f
>  #ifdef CONFIG_TRACE_IRQFLAGS
>  	call trace_hardirqs_on
>  #endif

This is on fixes, with a comment as otherwise I'm just going to forget 
why.