Re: [PATCH -next] riscv:uprobe remove set/clear SR_SPIE in arch_uprobe_pre/post/abort_xol

From: Guo Ren <guoren@kernel.org>
To: Yipeng Zou <zouyipeng@huawei.com>
Cc: linux-riscv <linux-riscv@lists.infradead.org>,
	 Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Albert Ou <aou@eecs.berkeley.edu>
Subject: Re: [PATCH -next] riscv:uprobe remove set/clear SR_SPIE in arch_uprobe_pre/post/abort_xol
Date: Wed, 20 Jul 2022 11:43:20 +0800	[thread overview]
Message-ID: <CAJF2gTTBQrSVeF0aC5TKaH=CFo5QDuCE8noF7e2N5=4MK5bpmA@mail.gmail.com> (raw)
In-Reply-To: <20220711024350.49611-1-zouyipeng@huawei.com>

On Mon, Jul 11, 2022 at 10:46 AM Yipeng Zou <zouyipeng@huawei.com> wrote:
>
> In riscv the process of uprobe going to clear spie before exec
> the origin insn,and set spie after that.But When access the page
> which origin insn has been placed a page fault may happen and
> irq was disabled in arch_uprobe_pre_xol function,It cause a WARN
> as follows.
> There is no need to clear/set spie in arch_uprobe_pre/post/abort_xol.
> We can just remove it.
Seems there is no side effect on an interrupt in xol. I also checked
arm64, x86, MIPS, and csky (also written by me), which are the same as
yours (No irq mask). I forgot why I mask irq for userspace xol.

>
> [   31.684157] BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1488
> [   31.684677] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 76, name: work
> [   31.684929] preempt_count: 0, expected: 0
> [   31.685969] CPU: 2 PID: 76 Comm: work Tainted: G
> [   31.686542] Hardware name: riscv-virtio,qemu (DT)
> [   31.686797] Call Trace:
> [   31.687053] [<ffffffff80006442>] dump_backtrace+0x30/0x38
> [   31.687699] [<ffffffff80812118>] show_stack+0x40/0x4c
> [   31.688141] [<ffffffff8081817a>] dump_stack_lvl+0x44/0x5c
> [   31.688396] [<ffffffff808181aa>] dump_stack+0x18/0x20
> [   31.688653] [<ffffffff8003e454>] __might_resched+0x114/0x122
> [   31.688948] [<ffffffff8003e4b2>] __might_sleep+0x50/0x7a
> [   31.689435] [<ffffffff80822676>] down_read+0x30/0x130
> [   31.689728] [<ffffffff8000b650>] do_page_fault+0x166/x446
> [   31.689997] [<ffffffff80003c0c>] ret_from_exception+0x0/0xc
>
> Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
Please add the Fixes tag.

Then:

Reviewed-by: Guo Ren <guoren@kernel.org>

> ---
>  arch/riscv/kernel/probes/uprobes.c | 6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
> index 7a057b5f0adc..c976a21cd4bd 100644
> --- a/arch/riscv/kernel/probes/uprobes.c
> +++ b/arch/riscv/kernel/probes/uprobes.c
> @@ -59,8 +59,6 @@ int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>
>         instruction_pointer_set(regs, utask->xol_vaddr);
>
> -       regs->status &= ~SR_SPIE;
> -
>         return 0;
>  }
>
> @@ -72,8 +70,6 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>
>         instruction_pointer_set(regs, utask->vaddr + auprobe->insn_size);
>
> -       regs->status |= SR_SPIE;
> -
>         return 0;
>  }
>
> @@ -111,8 +107,6 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>          * address.
>          */
>         instruction_pointer_set(regs, utask->vaddr);
> -
> -       regs->status &= ~SR_SPIE;
>  }
>
>  bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
> --
> 2.17.1
>


-- 
Best Regards
 Guo Ren

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