On Fri, 24 Apr 2015 11:44:05 +0900 AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> 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@xxxxxxxxxxx> > To: Ingo Molnar <mingo@xxxxxxxxxx> > To: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> > To: Seth Jennings <sjenning@xxxxxxxxxx> > To: Jiri Kosina <jkosina@xxxxxxx> > To: Vojtech Pavlik <vojtech@xxxxxxx> > To: Catalin Marinas <catalin.marinas@xxxxxxx> > To: Will Deacon <will.deacon@xxxxxxx> > > 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 live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
