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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 24DD6C004C9 for ; Wed, 8 May 2019 02:00:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE9C821479 for ; Wed, 8 May 2019 02:00:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726572AbfEHCAD (ORCPT ); Tue, 7 May 2019 22:00:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:38108 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726495AbfEHCAC (ORCPT ); Tue, 7 May 2019 22:00:02 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A46452173C; Wed, 8 May 2019 02:00:01 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.92) (envelope-from ) id 1hOBsG-0005rW-Mw; Tue, 07 May 2019 22:00:00 -0400 Message-Id: <20190508020000.595360124@goodmis.org> User-Agent: quilt/0.65 Date: Tue, 07 May 2019 21:56:01 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Peter Zijlstra , Andy Lutomirski , Ingo Molnar , Andrew Morton , Andy Lutomirski , Nicolai Stange , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "the arch/x86 maintainers" , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Konrad Rzeszutek Wilk , Tim Chen , Sebastian Andrzej Siewior , Mimi Zohar , Juergen Gross , Nick Desaulniers , Nayna Jain , Masahiro Yamada , Joerg Roedel , "open list:KERNEL SELFTEST FRAMEWORK" , stable , Masami Hiramatsu Subject: [PATCH 2/3] x86_64: Allow breakpoints to emulate call instructions References: <20190508015559.767152678@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski Cc: Nicolai Stange Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: the arch/x86 maintainers Cc: Josh Poimboeuf Cc: Jiri Kosina Cc: Miroslav Benes Cc: Petr Mladek Cc: Joe Lawrence Cc: Shuah Khan Cc: Konrad Rzeszutek Wilk Cc: Tim Chen Cc: Sebastian Andrzej Siewior Cc: Mimi Zohar Cc: Juergen Gross Cc: Nick Desaulniers Cc: Nayna Jain Cc: Masahiro Yamada Cc: Joerg Roedel Cc: "open list:KERNEL SELFTEST FRAMEWORK" Cc: stable@vger.kernel.org Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Signed-off-by: Peter Zijlstra (Intel) [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) --- arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index e85ff65c43c3..05861cc08787 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); extern int after_bootmem; +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */ -- 2.20.1