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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F894C433EF for ; Fri, 15 Oct 2021 12:52:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC940611C8 for ; Fri, 15 Oct 2021 12:52:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239128AbhJOMyO (ORCPT ); Fri, 15 Oct 2021 08:54:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:53720 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239258AbhJOMyF (ORCPT ); Fri, 15 Oct 2021 08:54:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A57886108E; Fri, 15 Oct 2021 12:51:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634302319; bh=lMfZZP/tcQBNE+YtsSJsSIaa1mi/f3aqAfbOhPMBTwU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VinROdbI2nOQEwbz1Bbr8uLxnMs6z2HkeNogB0M9aJsvxmpPXojOh/Ok3QcltLx4x rosRgtidldui2bVynfYGTcxW9L4QzOVkEilqPPC5v+upmHxl1/xQM7hJXhKa+mTAZv UBVeeaz9sAX6U4dq7C1QaqZYJ4TDOdMJPk2v/1PW8fYOtSgEpW5VoBLjLSRKfzdHXl LGdIWax8OFUtfaWi751ASKQ54ZlXB3oqBilFbaI/vSW/Ygi6ZFTxa4F8/8UQoh2O/4 +telTfkMb0UeeKqxoBMikS+VqSGVz6jX5RJhmujoharUU4lXe+DLeh3MD/lF07giR+ awEpdluZHPIZQ== From: Masami Hiramatsu To: Steven Rostedt Cc: "Naveen N . Rao" , Ananth N Mavinakayanahalli , Ingo Molnar , linux-kernel@vger.kernel.org, mhiramat@kernel.org, Sven Schnelle , Catalin Marinas , Will Deacon , Russell King , Nathan Chancellor , Nick Desaulniers , linux-arm-kernel@lists.infradead.org Subject: [PATCH 08/10] ARM: kprobes: Make a frame pointer on __kretprobe_trampoline Date: Fri, 15 Oct 2021 21:51:56 +0900 Message-Id: <163430231601.459050.8640625926942332950.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <163430224341.459050.2369208860773018092.stgit@devnote2> References: <163430224341.459050.2369208860773018092.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently kretprobe on ARM just fills r0-r11 of pt_regs, but that is not enough for the stacktrace. Moreover, from the user kretprobe handler, stacktrace needs a frame pointer on the __kretprobe_trampoline. This adds a frame pointer on __kretprobe_trampoline for both gcc and clang case. Those have different frame pointer so we need different but similar stack on pt_regs. Gcc makes the frame pointer (fp) to point the 'pc' address of the {fp, ip (=sp), lr, pc}, this means {r11, r13, r14, r15}. Thus if we save the r11 (fp) on pt_regs->r12, we can make this set on the end of pt_regs. On the other hand, Clang makes the frame pointer to point the 'fp' address of {fp, lr} on stack. Since the next to the pt_regs->lr is pt_regs->sp, I reused the pair of pt_regs->fp and pt_regs->ip. So this stores the 'lr' on pt_regs->ip and make the fp to point pt_regs->fp. For both cases, saves __kretprobe_trampoline address to pt_regs->lr, so that the stack tracer can identify this frame pointer has been made by the __kretprobe_trampoline. Note that if the CONFIG_FRAME_POINTER is not set, this keeps fp as is. Signed-off-by: Masami Hiramatsu Reviewed-by: Nick Desaulniers --- arch/arm/probes/kprobes/core.c | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-) diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c index 95f23b47ba27..7cbd65a22769 100644 --- a/arch/arm/probes/kprobes/core.c +++ b/arch/arm/probes/kprobes/core.c @@ -368,16 +368,35 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, /* * When a retprobed function returns, trampoline_handler() is called, * calling the kretprobe's handler. We construct a struct pt_regs to - * give a view of registers r0-r11 to the user return-handler. This is - * not a complete pt_regs structure, but that should be plenty sufficient - * for kretprobe handlers which should normally be interested in r0 only - * anyway. + * give a view of registers r0-r11, sp, lr, and pc to the user + * return-handler. This is not a complete pt_regs structure, but that + * should be enough for stacktrace from the return handler with or + * without pt_regs. */ void __naked __kprobes __kretprobe_trampoline(void) { __asm__ __volatile__ ( - "sub sp, sp, #16 \n\t" + "ldr lr, =__kretprobe_trampoline \n\t" + "stmdb sp!, {sp, lr, pc} \n\t" +#ifdef CONFIG_FRAME_POINTER + /* __kretprobe_trampoline makes a framepointer on pt_regs. */ +#ifdef CONFIG_CC_IS_CLANG + /* In clang case, pt_regs->ip = lr. */ + "stmdb sp!, {lr} \n\t" "stmdb sp!, {r0 - r11} \n\t" + /* fp points regs->r11 (fp) */ + "add fp, sp, #44 \n\t" +#else /* !CONFIG_CC_IS_CLANG */ + /* In gcc case, pt_regs->ip = fp. */ + "stmdb sp!, {fp} \n\t" + "stmdb sp!, {r0 - r11} \n\t" + /* fp points regs->r15 (pc) */ + "add fp, sp, #60 \n\t" +#endif /* CONFIG_CC_IS_CLANG */ +#else /* !CONFIG_FRAME_POINTER */ + "sub sp, sp, #4 \n\t" + "stmdb sp!, {r0 - r11} \n\t" +#endif /* CONFIG_FRAME_POINTER */ "mov r0, sp \n\t" "bl trampoline_handler \n\t" "mov lr, r0 \n\t"