From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 66F90C43458 for ; Fri, 10 Jul 2026 05:09:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:Mime-Version:References:In-Reply-To: Message-Id:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=/gvB5qwbT78hXA6WigUj4DzknIHPDynctPCi9ezZArQ=; b=hGEaq73rXm0WQD f8YOxm7v7DksDeAVyfPTuB4gR4B1CqNhbDVumQAySj7JA6h8xIjqdw3FMZGcMXxfiZTf0RTtGlI9L EHjEdnZVk5cELcLbes9GMqrKcfRDxG2DWZvXidZ7iM9bnHGv+49mX6jfkYtfM+LKnoSX8EXt0OKIQ 4u1Hz1GProjN2d8lg1UqlWgCNb3NRY4y9o3iWrm8lchtPcAJ7H4NQl08c9/PyDUne8LbEm3qOROsE Aop5nONc/gYm3VIfAXyFgVaPK3q+s9HXNVeajf1RjKDa2UhcO+tP2jroAVsiTRk+B1rGQ6+ZNmfdz s2z1aY/cf07L6FrNLERw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wi3Ue-00000004AtC-4A6t; Fri, 10 Jul 2026 05:09:44 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wi3Ud-00000004AsT-0IFV for linux-arm-kernel@lists.infradead.org; Fri, 10 Jul 2026 05:09:43 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id B5BD66001A; Fri, 10 Jul 2026 05:09:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFD641F000E9; Fri, 10 Jul 2026 05:09:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783660181; bh=/gvB5qwbT78hXA6WigUj4DzknIHPDynctPCi9ezZArQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=RV6c1iXakob2plSYioZq0ZlQFxbU0si4E0zbzqFMhpsnIOL/qW84hVY3I/rBp5KA6 8jpgSJr3mGUxqYb/QpBzEOqPCMAm4KDqMvOFIY4umfyT/9gwFRbUIhZ1HWTJ3Dx5Ok s2KJUJqmWTd3MvL7/D5HJXiOseK9GWy8mtpjqoRhSXe1KQemCk3LuPvymovPU+SsIz 7l+sQk1Hg9fW2P4OvWMqa1I8el+LjzM0gEX2DAr0ZPhfWrVhdntU0er+Z1FYce0wRg m4EREBILvvVmtbsc4BdUA+1gmoBfAYJeTeHhFBq9sHZjQFKw7Xr/oNgEhcLmJsQ9GR IrpcOLcYdb/1A== Date: Fri, 10 Jul 2026 14:09:36 +0900 From: Masami Hiramatsu (Google) To: Pu Hu Subject: Re: [RFC v2 2/3] arm64: kprobes: Allow reentering kprobes while single-stepping Message-Id: <20260710140936.8788416564452e490c71634c@kernel.org> In-Reply-To: <20260709142215.226872-3-hupu@transsion.com> References: <20260709142215.226872-1-hupu@transsion.com> <20260709142215.226872-3-hupu@transsion.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Hongyan Xia , Jiazi Li , "catalin.marinas@arm.com" , "linux-kernel@vger.kernel.org" , "naveen@kernel.org" , "yang@os.amperecomputing.com" , "will@kernel.org" , "davem@davemloft.net" , "linux-arm-kernel@lists.infradead.org" , "linux-trace-kernel@vger.kernel.org" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 9 Jul 2026 14:22:25 +0000 Pu Hu wrote: > From: Pu Hu > > A kprobe can be hit while another kprobe is in KPROBE_HIT_SS state. This > can happen when tracing or perf code runs from the debug exception path > while the first kprobe is preparing or executing its out-of-line > single-step instruction. > > Currently arm64 treats a kprobe hit in KPROBE_HIT_SS as unrecoverable, > the same as a hit in KPROBE_REENTER. This is too strict. A hit in > KPROBE_HIT_SS is still a one-level reentry and can be handled by saving > the current kprobe state and setting up single-step for the new probe, > just like reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. > > The truly unrecoverable case is hitting another kprobe while already in > KPROBE_REENTER, because the reentry save area has already been consumed. > > Move KPROBE_HIT_SS to the recoverable reentry cases and leave > KPROBE_REENTER as the unrecoverable nested reentry case. > > This mirrors the x86 fix in commit 6a5022a56ac3 > ("kprobes/x86: Allow to handle reentered kprobe on single-stepping"). > Hi, as Sashiko commented, we have to save the saved_irqflag to prev_kprobbe. https://sashiko.dev/#/patchset/20260709142215.226872-1-hupu%40transsion.com?part=2 Thank you, > Signed-off-by: Pu Hu > Signed-off-by: Hongyan Xia > --- > arch/arm64/kernel/probes/kprobes.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > index 798e4b091d1a..2ca5916eca2f 100644 > --- a/arch/arm64/kernel/probes/kprobes.c > +++ b/arch/arm64/kernel/probes/kprobes.c > @@ -240,10 +240,16 @@ static int __kprobes reenter_kprobe(struct kprobe *p, > switch (kcb->kprobe_status) { > case KPROBE_HIT_SSDONE: > case KPROBE_HIT_ACTIVE: > + case KPROBE_HIT_SS: > + /* > + * A probe can be hit while another kprobe is preparing or > + * executing its XOL single-step instruction. This is still a > + * recoverable one-level reentry, so handle it in the same way as > + * reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. > + */ > kprobes_inc_nmissed_count(p); > setup_singlestep(p, regs, kcb, 1); > break; > - case KPROBE_HIT_SS: > case KPROBE_REENTER: > pr_warn("Failed to recover from reentered kprobes.\n"); > dump_kprobe(p); > -- > 2.43.0 > -- Masami Hiramatsu (Google)