From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Fri, 24 Apr 2015 17:04:02 +0900 Subject: [RFC 0/4] arm64: add livepatch support In-Reply-To: <5539DD2B.3010603@hitachi.com> References: <1429843449-7388-1-git-send-email-takahiro.akashi@linaro.org> <5539B782.8060507@huawei.com> <5539DD2B.3010603@hitachi.com> Message-ID: <5539F8F2.4070005@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 >>> >> >> >> > >