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 X-Spam-Level: X-Spam-Status: No, score=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0C96C2B9F4 for ; Thu, 17 Jun 2021 15:02:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1B46610A0 for ; Thu, 17 Jun 2021 15:02:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233117AbhFQPE7 (ORCPT ); Thu, 17 Jun 2021 11:04:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:34106 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233104AbhFQPEv (ORCPT ); Thu, 17 Jun 2021 11:04:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 386E6610A3; Thu, 17 Jun 2021 15:02:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1623942163; bh=z1iyLhNJsf7wtbsK5AmP9LuCmt80iLYAIIgiUSThkRk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mm8n+Tlbxe2H14BC1lijg42X/bWhlB+XtItSgLm9Fb8/9MioxRxj6Rg3MZQCqqt2B BNZzK3hsNMmKmZZ7a1ORDbjU5lzS4bEE932nlB5xg3DZ3fwj8++O5jgbrnBcRBXNFK 4BvyBLrYovGKEwflMQHGFfjE8cy9BTqcP/5iDkZaP204BQ8qCioWg7ahpok558d524 1lucS75wb7jK9VFFrpJDLVmY/Zjqj3RtdF96MzxRe1iUgNB09XvhEiYVNhAe5krmBg JxcY8nNQYJQY7u1wR69KDUJ9yMhcgPjmVnLHIeGh/M5BjW1/zmI7ccRVr7DZh9F7iD WFmIJSdx7uHRw== Date: Fri, 18 Jun 2021 00:02:39 +0900 From: Masami Hiramatsu To: Masami Hiramatsu , Andrii Nakryiko Cc: Josh Poimboeuf , Steven Rostedt , Ingo Molnar , X86 ML , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org, Abhishek Sagar Subject: Re: [PATCH -tip v7 09/13] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Message-Id: <20210618000239.f95de17418beae6d84ce783d@kernel.org> In-Reply-To: <20210617234001.54cd2ff60410ff82a39a2020@kernel.org> References: <162209754288.436794.3904335049560916855.stgit@devnote2> <162209762943.436794.874947392889792501.stgit@devnote2> <20210617043909.fgu2lhnkxflmy5mk@treble> <20210617044032.txng4enhiduacvt6@treble> <20210617234001.54cd2ff60410ff82a39a2020@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 17 Jun 2021 23:40:01 +0900 Masami Hiramatsu wrote: > On Wed, 16 Jun 2021 23:40:32 -0500 > Josh Poimboeuf wrote: > > > On Wed, Jun 16, 2021 at 11:39:11PM -0500, Josh Poimboeuf wrote: > > > On Thu, May 27, 2021 at 03:40:29PM +0900, Masami Hiramatsu wrote: > > > > To simplify the stacktrace with pt_regs from kretprobe handler, > > > > set the correct return address to the instruction pointer in > > > > the pt_regs before calling kretprobe handlers. > > > > > > > > Suggested-by: Josh Poimboeuf > > > > Signed-off-by: Masami Hiramatsu > > > > Tested-by: Andrii Nakryik > > > > --- > > > > Changes in v3: > > > > - Cast the correct_ret_addr to unsigned long. > > > > --- > > > > kernel/kprobes.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > > index 54e5b89aad67..1598aca375c9 100644 > > > > --- a/kernel/kprobes.c > > > > +++ b/kernel/kprobes.c > > > > @@ -1914,6 +1914,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, > > > > BUG_ON(1); > > > > } > > > > > > > > + /* Set the instruction pointer to the correct address */ > > > > + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); > > > > + > > > > /* Run them. */ > > > > first = current->kretprobe_instances.first; > > > > while (first) { > > > > > > > > > > Hi Masami, > > > > > > I know I suggested this patch, but I believe it would only be useful in > > > combination with the use of UNWIND_HINT_REGS in SAVE_REGS_STRING. But I > > > think that would be tricky to pull off correctly. Instead, we have > > > UNWIND_HINT_FUNC, which is working fine. > > > > > > So I'd suggest dropping this patch, as the unwinder isn't actually > > > reading regs->ip after all. > > > > ... and I guess this means patches 6-8 are no longer necessary. > > OK, I also confirmed that dropping those patche does not make any change > on the stacktrace. > Let me update the series without those. Oops, Andrii, can you also test the kernel without this patch? (you don't need to drop patch 6-8) This changes the kretprobe to pass the return address via regs->ip to handler. Dynamic-event doesn't use it, but I'm not sure bcc is using it or not. Thank you, > > Thank you, > > > > > -- > > Josh > > > > > -- > Masami Hiramatsu -- Masami Hiramatsu