linux-kernel - Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception

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Message-Id: <20210401093036.037f2abbce7ed5d1e68466b7@kernel.org>
Date:   Thu, 1 Apr 2021 09:30:36 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jisheng Zhang <jszhang3@...l.ustc.edu.cn>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Guo Ren <guoren@...ux.alibaba.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT
 exception

Hi,

On Wed, 31 Mar 2021 22:22:44 +0800
Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:

> On Tue, 30 Mar 2021 18:33:16 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Hi Jisheng,
> 
> Hi Masami,
> 
> > 
> > On Tue, 30 Mar 2021 02:16:24 +0800
> > Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
> > 
> > > From: Jisheng Zhang <jszhang@...nel.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.  
> > 
> > Not only while the breakpoint exception but also until the end of
> > the single step (maybe you are using __BUG_INSN_32 ??) need to be
> > disable interrupts. Can this do that?
> > 
> 
> interrupt is disabled during "single step" by kprobes_save_local_irqflag()
> and kprobes_restore_local_irqflag(). The code flow looks like: 
> 
> do_trap_break()   // for bp
>   kprobe_breakpoint_handler()
>     setup_singlestep()
>       kprobes_restore_local_irqflag()
> 
> do_trap_break()  // for ss
>   kprobe_single_step_handler()
>     kprobes_restore_local_irqflag()

OK, thanks for the confirmation!

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks,

-- 
Masami Hiramatsu <mhiramat@...nel.org>