On 05/30/2015 09:01 AM, Masami Hiramatsu wrote: > On 2015/05/28 14:51, Li Bin wrote: >> This patchset propose a method for gcc -mfentry feature(profile >> before prologue) implementation for arm64, and propose the livepatch >> implementation for arm64 based on this feature. >> The gcc implementation about this feature will be post to the gcc >> community soon. >> >> With this -mfentry feature, the entry of each function like: >> >> foo: >> mov x9, x30 >> bl __fentry__ >> mov x30, x9 >> [prologue] >> ... >> >> The x9 is a callee corruptible register, and the __fentry__ function >> is responsible to protect all registers, so it can be used to protect >> the x30. And the added two instructions which is register mov operation >> have ralatively small impact on performance. > > Hm, this implementation looks good to me :) > This also enables us to KPROBES_ON_FTRACE too. Even if x9 is a callee-saved register, there is no way to restore its original value in setting up a pt_regs in ftrace_reg_caller. It's not the right thing for KPROBES_ON_FTRACE, is it? Saving Link register in stack is not a big deal since the overhead of ftrace is much bigger. -Takahiro AKASHI > Thanks, > >> >> This patchset has been tested on arm64 platform. >> >> Li Bin (4): >> livepatch: ftrace: arm64: Add support for DYNAMIC_FTRACE_WITH_REGS >> livepatch: ftrace: add ftrace_function_stub_ip function >> livepatch: ftrace: arm64: Add support for -mfentry on arm64 >> livepatch: arm64: add support for livepatch on arm64 >> >> Xie XiuQi (1): >> livepatch: arm64: support relocation in a module >> >> arch/arm64/Kconfig | 5 + >> arch/arm64/include/asm/ftrace.h | 9 + >> arch/arm64/include/asm/livepatch.h | 45 +++++ >> arch/arm64/kernel/Makefile | 1 + >> arch/arm64/kernel/arm64ksyms.c | 4 + >> arch/arm64/kernel/entry-ftrace.S | 154 +++++++++++++++- >> arch/arm64/kernel/ftrace.c | 28 +++- >> arch/arm64/kernel/livepatch.c | 41 ++++ >> arch/arm64/kernel/module.c | 355 ++++++++++++++++++------------------ >> include/linux/ftrace.h | 1 + >> kernel/livepatch/core.c | 17 ++- >> kernel/trace/ftrace.c | 32 ++++ >> scripts/recordmcount.pl | 2 +- >> 13 files changed, 508 insertions(+), 186 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@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > > -- 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
