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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 F233FC433E6 for ; Wed, 10 Mar 2021 15:43:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4D4A64FC0 for ; Wed, 10 Mar 2021 15:43:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233155AbhCJPm5 (ORCPT ); Wed, 10 Mar 2021 10:42:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:52042 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233161AbhCJPmb (ORCPT ); Wed, 10 Mar 2021 10:42:31 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4036B64F60; Wed, 10 Mar 2021 15:42:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615390951; bh=JOdkfpOFS6fkbawiuazEFw2CCzjQJ0pFxL/CxofoRsU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=g30NPMXI2QdxxB3J5nI4sNuTRLMmKcIBMwtc1w6cjCcbVNCrQaHVE/FFqSTIsV7Uw PBl9u99YWK1AgetTrcBpdZXt7k7Gb7Wup0NKvQ4oyL3NRkZJsA3bioiTLR/K5YGnmV OKHniCiQyibtS9p+VpgAYzqkwPlw6B3uJXfZBtPMQDWNx7CrHSDps7RHUcPp763+ZT 9px+SHHydWAMuQjV4EhJr3pwMsKpJ43LGqGJ1uoJhchNm0Mn8uYCMs6L8sunSUWz0v LjH8rc/XkpP1w/NY2Ak8jzYeC0WSwhZudGVgIwg4uEM0grOFNpQiWeysB7fF965wHT 43FgiSPgD82gw== Date: Thu, 11 Mar 2021 00:42:25 +0900 From: Masami Hiramatsu To: Miroslav Benes Cc: 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 Subject: Re: [PATCH -tip 3/5] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Message-Id: <20210311004225.77e844ff8170108bfb75b470@kernel.org> In-Reply-To: References: <161495873696.346821.10161501768906432924.stgit@devnote2> <161495876994.346821.11468535974887762132.stgit@devnote2> 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 Wed, 10 Mar 2021 15:21:01 +0100 (CET) Miroslav Benes wrote: > Hi Masami, > > > --- a/include/linux/kprobes.h > > +++ b/include/linux/kprobes.h > > @@ -205,15 +205,23 @@ extern void arch_prepare_kretprobe(struct kretprobe_instance *ri, > > struct pt_regs *regs); > > extern int arch_trampoline_kprobe(struct kprobe *p); > > > > +void kretprobe_trampoline(void); > > +/* > > + * Since some architecture uses structured function pointer, > > + * use arch_deref_entry_point() to get real function address. > > s/arch_deref_entry_point/dereference_function_descriptor/ ? Ah, I missed it. Thanks! > > > + */ > > +static nokprobe_inline void *kretprobe_trampoline_addr(void) > > +{ > > + return dereference_function_descriptor(kretprobe_trampoline); > > +} > > + > > Would it make sense to use this in s390 and powerpc reliable unwinders? > > Both > > arch/s390/kernel/stacktrace.c:arch_stack_walk_reliable() > arch/powerpc/kernel/stacktrace.c:__save_stack_trace_tsk_reliable() > > have > > if (state.ip == (unsigned long)kretprobe_trampoline) > return -EINVAL; > > which you wanted to hide previously if I am not mistaken. I think, if "ip" means "instruction pointer", it should point the real instruction address, which is dereferenced from function descriptor. So using kretprobe_trampoline_addr() is good. But of course, it depends on the architecture. I'm not familiar with the powerpc and s390, I need those maintainer's help... Thank you, -- Masami Hiramatsu