On Fri, 24 Apr 2015 11:44:05 +0900
AKASHI Takahiro [off-list ref] 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.
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.
You need to be extremely careful about this. I don't know what arm does
with mcount but on x86 without -fentry, it sets up the stack frame
before calling mcount. That is, if mcount returns to a different
function, it doesn't mean that the registers will match the parameters.
I have to look at what arm64 does when compiled with -pg. Because, if
it moves registers around before the mcount, you will have a disaster
on your hands if it returns to a different function that moved the
registers around differently.
Also, you need to be careful about how link registers are handled.
-- Steve
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@goodmis.org>
To: Ingo Molnar <mingo@kernel.org>
To: Josh Poimboeuf <redacted>
To: Seth Jennings <redacted>
To: Jiri Kosina <redacted>
To: Vojtech Pavlik <redacted>
To: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <redacted>
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