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 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 3C03FC433DB for ; Sat, 20 Mar 2021 13:06:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1BE9561974 for ; Sat, 20 Mar 2021 13:06:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229805AbhCTNGB (ORCPT ); Sat, 20 Mar 2021 09:06:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:40638 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229583AbhCTNFs (ORCPT ); Sat, 20 Mar 2021 09:05:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3FCE561961; Sat, 20 Mar 2021 13:05:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616245548; bh=QXdaST1hot6+jYq0oDK7muVDY+aF5hPeweOnMuFWDCs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NydJpk1snnUb6dtJ3ZHVlpmHmHA2q14dEvUBuB0jJFMpTdDmqu/qwgRRbY0n6v2Gy Ix/wCW4nQ4qR9WeEborqVTAbWBQgbMSyqOF3qnwwGhryXy5SmB9jrJz0f8WFY2GiH/ klxCX3q38Y4Q0gl7kitV6r+mQXBbX9Li9FIWO5x8FfmzCi6yHF4BFsLTs6ku6yg/Kv 2+4ED1VkoHQecF2OHyU27+JmTIFl7IKPT3Bsjfudo11Mfb+Iwg8q+jORyMC+URCKmZ 7Ta2AeQELSGacKdCasQzz5ethCyiqe6B8z+AIoOdFU+GXEhksadHdGdSRrItVXMO92 3PN+YfIR3UVow== Date: Sat, 20 Mar 2021 22:05:43 +0900 From: Masami Hiramatsu To: Masami Hiramatsu 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, Josh Poimboeuf , linux-ia64@vger.kernel.org Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Message-Id: <20210320220543.e1558ce3a351554c6be3ea26@kernel.org> In-Reply-To: <20210320211616.a976fc66d0c51e13d3121e2f@kernel.org> References: <161615650355.306069.17260992641363840330.stgit@devnote2> <161615655969.306069.4545805781593088526.stgit@devnote2> <20210320211616.a976fc66d0c51e13d3121e2f@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 Sat, 20 Mar 2021 21:16:16 +0900 Masami Hiramatsu wrote: > On Fri, 19 Mar 2021 21:22:39 +0900 > Masami Hiramatsu wrote: > > > From: Josh Poimboeuf > > > > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC > > information is generated on the kretprobe_trampoline correctly. > > > > Test bot also found a new warning for this. > > > >> arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x25: call without frame pointer save/setup > > With CONFIG_FRAME_POINTER=y. > > Of course this can be fixed with additional "push %bp; mov %sp, %bp" before calling > trampoline_handler. But actually we know that this function has a bit special > stack frame too. > > Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when CONFIG_FRAME_POINTER=y ? So something like this. Does it work? diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index b31058a152b6..651f337dc880 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -760,6 +760,10 @@ int kprobe_int3_handler(struct pt_regs *regs) } NOKPROBE_SYMBOL(kprobe_int3_handler); +#ifdef CONFIG_FRAME_POINTER +#undef UNWIND_HINT_FUNC +#define UNWIND_HINT_FUNC +#endif /* * When a retprobed function returns, this code saves registers and * calls trampoline_handler() runs, which calls the kretprobe's handler. @@ -797,7 +801,14 @@ asm( ".size kretprobe_trampoline, .-kretprobe_trampoline\n" ); NOKPROBE_SYMBOL(kretprobe_trampoline); - +#ifdef CONFIG_FRAME_POINTER +/* + * kretprobe_trampoline skips updating frame pointer. The frame pointer + * saved in trampoline_handler points to the real caller function's + * frame pointer. + */ +STACK_FRAME_NON_STANDARD(kretprobe_trampoline); +#endif /* * Called from kretprobe_trampoline -- Masami Hiramatsu From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Sat, 20 Mar 2021 13:05:43 +0000 Subject: Re: [PATCH -tip v3 05/11] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Message-Id: <20210320220543.e1558ce3a351554c6be3ea26@kernel.org> List-Id: References: <161615650355.306069.17260992641363840330.stgit@devnote2> <161615655969.306069.4545805781593088526.stgit@devnote2> <20210320211616.a976fc66d0c51e13d3121e2f@kernel.org> In-Reply-To: <20210320211616.a976fc66d0c51e13d3121e2f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Masami Hiramatsu 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, Josh Poimboeuf , linux-ia64@vger.kernel.org On Sat, 20 Mar 2021 21:16:16 +0900 Masami Hiramatsu wrote: > On Fri, 19 Mar 2021 21:22:39 +0900 > Masami Hiramatsu wrote: > > > From: Josh Poimboeuf > > > > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC > > information is generated on the kretprobe_trampoline correctly. > > > > Test bot also found a new warning for this. > > > >> arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x25: call without frame pointer save/setup > > With CONFIG_FRAME_POINTER=y. > > Of course this can be fixed with additional "push %bp; mov %sp, %bp" before calling > trampoline_handler. But actually we know that this function has a bit special > stack frame too. > > Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when CONFIG_FRAME_POINTER=y ? So something like this. Does it work? diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index b31058a152b6..651f337dc880 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -760,6 +760,10 @@ int kprobe_int3_handler(struct pt_regs *regs) } NOKPROBE_SYMBOL(kprobe_int3_handler); +#ifdef CONFIG_FRAME_POINTER +#undef UNWIND_HINT_FUNC +#define UNWIND_HINT_FUNC +#endif /* * When a retprobed function returns, this code saves registers and * calls trampoline_handler() runs, which calls the kretprobe's handler. @@ -797,7 +801,14 @@ asm( ".size kretprobe_trampoline, .-kretprobe_trampoline\n" ); NOKPROBE_SYMBOL(kretprobe_trampoline); - +#ifdef CONFIG_FRAME_POINTER +/* + * kretprobe_trampoline skips updating frame pointer. The frame pointer + * saved in trampoline_handler points to the real caller function's + * frame pointer. + */ +STACK_FRAME_NON_STANDARD(kretprobe_trampoline); +#endif /* * Called from kretprobe_trampoline -- Masami Hiramatsu