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=-16.2 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_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 EE740C433E0 for ; Tue, 23 Mar 2021 00:05:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8862619AE for ; Tue, 23 Mar 2021 00:05:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230520AbhCWAFJ (ORCPT ); Mon, 22 Mar 2021 20:05:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:59114 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231193AbhCWAEf (ORCPT ); Mon, 22 Mar 2021 20:04:35 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 68F11619A3; Tue, 23 Mar 2021 00:04:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616457873; bh=OHo+vflUXrll9v/rTKEgd/KJdrtb/YspGpJNGL7VLQE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NBgaXuGQo7HTAuPy5mjlDYjF33dYGEWYE+IGtP41/3SJJL1o+OlCzwquSv08024K2 Uj568H3nV42Rm/zpaGxRWk7qrwUNzl/wFr7x6hAio2NAv3pQt2SiNGI7OVPYclBiXP hwCszuVvEupNYZAGMCYIIg3p940tSU0BkGXfzK/X5Tf7pFprFiDZX25GatbgHEnYzx U2f4OG3z/XUqWVhayFE1ahAAbagNETfbdcXdWQrK/UwKKi9quQO1KfSKMrsO1uxE7z MMXtMG4/yDjV4bYHW1V+OIN7TTfWUnG5NU8FPZrGk8ZlmtoLnR7yirYgQoSummOBLP gQfZNwEr9RcNQ== Date: Tue, 23 Mar 2021 09:04:29 +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, Abhishek Sagar Subject: Re: [PATCH -tip v4 08/12] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Message-Id: <20210323090429.da18461654ef9907581dab95@kernel.org> In-Reply-To: <161639527851.895304.14313883616251450754.stgit@devnote2> References: <161639518354.895304.15627519393073806809.stgit@devnote2> <161639527851.895304.14313883616251450754.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: bpf@vger.kernel.org On Mon, 22 Mar 2021 15:41:18 +0900 Masami Hiramatsu wrote: > Change kretprobe_trampoline to make a space for regs->ARM_pc so that > kretprobe_trampoline_handler can call instruction_pointer_set() > safely. BTW, if kretprobe_trampoline is replaced with the assembly code, I think it should fill all the regs as much as possible, because originally it is written by a software break. Thus the regs->sp should point the stack address at the entry of kretprobe_trampoline, and also regs->lr and regs->pc will be kretprobe_trampoline, so that user handler can access caller stack. Thanks, > > Signed-off-by: Masami Hiramatsu > --- > arch/arm/probes/kprobes/core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c > index 1782b41df095..5f3c2b42787f 100644 > --- a/arch/arm/probes/kprobes/core.c > +++ b/arch/arm/probes/kprobes/core.c > @@ -397,11 +397,13 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, > void __naked __kprobes kretprobe_trampoline(void) > { > __asm__ __volatile__ ( > + "sub sp, sp, #16 \n\t" > "stmdb sp!, {r0 - r11} \n\t" > "mov r0, sp \n\t" > "bl trampoline_handler \n\t" > "mov lr, r0 \n\t" > "ldmia sp!, {r0 - r11} \n\t" > + "add sp, sp, #16 \n\t" > #ifdef CONFIG_THUMB2_KERNEL > "bx lr \n\t" > #else > -- Masami Hiramatsu