Hi, This series enables objtool to start doing stack validation on arm64 kernel builds. It relies on the previous series I sent, refactoring the arm64 decoder [1].
First, the aarch64 instruction decoder needed to be made available to code under tools/. This is done in a similar manner to x86 instruction decoded. One limitation I encountered there is that most of aarch64 instruction decoder is __kprobe annotated. To bypass that it remove the kprobe include and had to add an empty __kprobe definition, but I'd welcome a proper solution to that. Then instruction semantics are progressively added so objtool can track the stack state through the execution flow. There are a few things that needed consideration: - Generation of constants within executable sections, these either caused objtool to fail decoding or to wrongly decode constants as jumps or other instructions affecting execution flow and causing confusion. To solve this, tracking locations referenced by instructions using literals was needed. - Jump tables from switch statements in aarch64 don't have enough information to link branches with the branch instruction leading to them. Following suggestions, I've dropped the previously used GCC plugin and instead disabled the generation of jump tables by the compiler. I've not noticed performance deterioration nor concerning Image size increase after doing so. This approach has the benefit of working for both GCC and clang. With those changes, there are still some errors when building with objtool. A number of cleanups/annotations are needed on the arm64, as well as handling SYM_DATA objects in objtool. Those changes can be found on top of this branch here: git clone https://github.com/julien-thierry/linux.git -b objtoolxarm64-latest Changes since v1[2]: - Drop gcc plugin in favor of -fno-jump-tables - miscelaneous fixes and cleanups [1] https://lkml.org/lkml/2021/1/20/791 [2] https://lkml.org/lkml/2021/1/20/923 Thanks, Julien --> Julien Thierry (12): tools: Add some generic functions and headers tools: arm64: Make aarch64 instruction decoder available to tools tools: bug: Remove duplicate definition objtool: arm64: Add base definition for arm64 backend objtool: arm64: Decode add/sub instructions objtool: arm64: Decode jump and call related instructions objtool: arm64: Decode other system instructions objtool: arm64: Decode load/store instructions objtool: arm64: Decode LDR instructions objtool: arm64: Accept padding in code sections objtool: arm64: Handle supported relocations in alternatives objtool: arm64: Ignore replacement section for alternative callback Raphael Gault (1): objtool: arm64: Enable stack validation for arm64 arch/arm64/Kconfig | 1 + arch/arm64/Makefile | 4 + tools/arch/arm64/include/asm/insn.h | 565 +++++++ tools/arch/arm64/lib/insn.c | 1456 +++++++++++++++++ tools/include/asm-generic/bitops/__ffs.h | 11 + tools/include/linux/bug.h | 6 +- tools/include/linux/kernel.h | 21 + tools/include/linux/printk.h | 40 + tools/objtool/Makefile | 5 + tools/objtool/arch/arm64/Build | 8 + tools/objtool/arch/arm64/decode.c | 502 ++++++ .../arch/arm64/include/arch/cfi_regs.h | 14 + tools/objtool/arch/arm64/include/arch/elf.h | 6 + .../arch/arm64/include/arch/endianness.h | 9 + .../objtool/arch/arm64/include/arch/special.h | 21 + tools/objtool/arch/arm64/special.c | 37 + tools/objtool/arch/x86/decode.c | 5 + tools/objtool/check.c | 6 + tools/objtool/include/objtool/arch.h | 3 + tools/objtool/sync-check.sh | 5 + 20 files changed, 2720 insertions(+), 5 deletions(-) create mode 100644 tools/arch/arm64/include/asm/insn.h create mode 100644 tools/arch/arm64/lib/insn.c create mode 100644 tools/include/linux/printk.h create mode 100644 tools/objtool/arch/arm64/Build create mode 100644 tools/objtool/arch/arm64/decode.c create mode 100644 tools/objtool/arch/arm64/include/arch/cfi_regs.h create mode 100644 tools/objtool/arch/arm64/include/arch/elf.h create mode 100644 tools/objtool/arch/arm64/include/arch/endianness.h create mode 100644 tools/objtool/arch/arm64/include/arch/special.h create mode 100644 tools/objtool/arch/arm64/special.c -- 2.25.4
