Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755589AbbDXIEQ (ORCPT ); Fri, 24 Apr 2015 04:04:16 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:36385 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752631AbbDXIEM (ORCPT ); Fri, 24 Apr 2015 04:04:12 -0400 Message-ID: <5539F8F2.4070005@linaro.org> Date: Fri, 24 Apr 2015 17:04:02 +0900 From: AKASHI Takahiro User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Masami Hiramatsu , Li Bin CC: rostedt@goodmis.org, mingo@kernel.org, jpoimboe@redhat.com, sjenning@redhat.com, jkosina@suse.cz, vojtech@suse.cz, catalin.marinas@arm.com, will.deacon@arm.com, broonie@kernel.org, live-patching@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org, linux-kernel@vger.kernel.org Subject: Re: [RFC 0/4] arm64: add livepatch support References: <1429843449-7388-1-git-send-email-takahiro.akashi@linaro.org> <5539B782.8060507@huawei.com> <5539DD2B.3010603@hitachi.com> In-Reply-To: <5539DD2B.3010603@hitachi.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3266 Lines: 85 Steve, Li and Masami, Thank you for all your comments. You pointed out the cases that I didn't think of. Let me think how I can manage the issues for a while. Probably I will talk to gcc guys. -Takahiro AKASHI On 04/24/2015 03:05 PM, Masami Hiramatsu wrote: > (2015/04/24 12:24), Li Bin wrote: >> On 2015/4/24 10:44, AKASHI Takahiro wrote: >>> This patchset enables livepatch support on arm64. >>> >>> Livepatch was merged in v4.0, and allows replacying a function dynamically >>> based on ftrace framework, but it also requires -mfentry option of gcc. >>> Currently arm64 gcc doesn't support it, but by adding a helper function to >>> ftrace, we will be able to support livepatch on arch's which don't support >>> this option. >>> >> >> This is not correct for the case that the prologue of the old and new function >> is different. > > Hmm, is that possible to support -mfentry on arm64? > > Of course we can not call a function directly at the first > instruction of functions on arm, because it can overwrite > link register which stores caller address. However, we can > do "store link register to stack and branch with link" > on arm. That is actually almost same as -mfentry does :), > and that may not depend on the prologue. > > Thank you, > > >> Thanks, >> Li Bin >> >>> I submit this patchset as RFC since I'm not quite sure that I'm doing >>> in the right way, or we should definitely support -fentry instead. >>> >>> Please note that I tested the feature only with livepatch-sample, and >>> the code for DYNAMIC_TRACE_WITH_REGS is still rough-edged. >>> >>> To: Steven Rostedt >>> To: Ingo Molnar >>> To: Josh Poimboeuf >>> To: Seth Jennings >>> To: Jiri Kosina >>> To: Vojtech Pavlik >>> To: Catalin Marinas >>> To: Will Deacon >>> >>> AKASHI Takahiro (4): >>> ftrace: add a helper function for livepatch >>> livepatch: adjust a patched function's address >>> arm64: ftrace: add DYNAMIC_TRACE_WITH_REGS version >>> arm64: add livepatch support >>> >>> arch/arm64/Kconfig | 4 ++ >>> arch/arm64/include/asm/ftrace.h | 4 ++ >>> arch/arm64/include/asm/livepatch.h | 38 +++++++++++ >>> arch/arm64/kernel/Makefile | 1 + >>> arch/arm64/kernel/entry-ftrace.S | 124 ++++++++++++++++++++++++++++++++++++ >>> arch/arm64/kernel/ftrace.c | 24 ++++++- >>> arch/arm64/kernel/livepatch.c | 68 ++++++++++++++++++++ >>> arch/x86/include/asm/livepatch.h | 5 ++ >>> include/linux/ftrace.h | 2 + >>> include/linux/livepatch.h | 2 + >>> kernel/livepatch/core.c | 16 +++-- >>> kernel/trace/ftrace.c | 26 ++++++++ >>> 12 files changed, 309 insertions(+), 5 deletions(-) >>> create mode 100644 arch/arm64/include/asm/livepatch.h >>> create mode 100644 arch/arm64/kernel/livepatch.c >>> >> >> >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/