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From: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Guo Ren <guoren@linux.alibaba.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception
Date: Wed, 31 Mar 2021 22:22:44 +0800	[thread overview]
Message-ID: <20210331222244.45a5807c@xhacker> (raw)
In-Reply-To: <20210330183316.942215efe8e6e8455ad14113@kernel.org>

On Tue, 30 Mar 2021 18:33:16 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hi Jisheng,

Hi Masami,

> 
> On Tue, 30 Mar 2021 02:16:24 +0800
> Jisheng Zhang <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.  
> 
> 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()

Thanks


WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang3@mail.ustc.edu.cn>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Guo Ren <guoren@linux.alibaba.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception
Date: Wed, 31 Mar 2021 22:22:44 +0800	[thread overview]
Message-ID: <20210331222244.45a5807c@xhacker> (raw)
In-Reply-To: <20210330183316.942215efe8e6e8455ad14113@kernel.org>

On Tue, 30 Mar 2021 18:33:16 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hi Jisheng,

Hi Masami,

> 
> On Tue, 30 Mar 2021 02:16:24 +0800
> Jisheng Zhang <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.  
> 
> 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()

Thanks


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  reply	other threads:[~2021-03-31 14:29 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-29 18:16 [PATCH] riscv: keep interrupts disabled for BREAKPOINT exception Jisheng Zhang
2021-03-29 18:16 ` Jisheng Zhang
2021-03-30  9:33 ` Masami Hiramatsu
2021-03-30  9:33   ` Masami Hiramatsu
2021-03-31 14:22   ` Jisheng Zhang [this message]
2021-03-31 14:22     ` Jisheng Zhang
2021-04-01  0:30     ` Masami Hiramatsu
2021-04-01  0:30       ` Masami Hiramatsu
2021-04-03 18:30       ` Maciej W. Rozycki
2021-04-03 18:30         ` Maciej W. Rozycki
2021-04-08 11:23         ` Jisheng Zhang
2021-04-08 11:23           ` Jisheng Zhang
2021-04-08 22:38           ` Masami Hiramatsu
2021-04-08 22:38             ` Masami Hiramatsu
2021-04-08 22:45             ` Maciej W. Rozycki
2021-04-08 22:45               ` Maciej W. Rozycki
2021-04-01  8:49     ` liaochang (A)
2021-04-01  8:49       ` liaochang (A)
2021-04-02 13:32       ` Jisheng Zhang
2021-04-02 13:32         ` Jisheng Zhang
2021-04-06  7:27         ` liaochang (A)
2021-04-06  7:27           ` liaochang (A)
2021-04-12  1:09 ` Palmer Dabbelt
2021-04-12  1:09   ` Palmer Dabbelt

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