[RFC 0/4] arm64: add livepatch support
huawei.libin at huawei.com
Wed May 27 22:40:26 PDT 2015
On 2015/4/24 14:05, 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.
Yes, but the method "store link register to stack" will break the arm64 ABI rules,
and memory operations may bring performance cost.
We have a gcc -mfentry implementation strategy for arm64, and based on this we
implement the livepatch for arm64.
I will post the patchset for review soon.
> Thank you,
>> 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 <rostedt at goodmis.org>
>>> To: Ingo Molnar <mingo at kernel.org>
>>> To: Josh Poimboeuf <jpoimboe at redhat.com>
>>> To: Seth Jennings <sjenning at redhat.com>
>>> To: Jiri Kosina <jkosina at suse.cz>
>>> To: Vojtech Pavlik <vojtech at suse.cz>
>>> To: Catalin Marinas <catalin.marinas at arm.com>
>>> To: Will Deacon <will.deacon at arm.com>
>>> 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
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