[RFC PATCH v2 00/13] objtool: add base support for arm64

[Julien Thierry <jthierry@redhat.com>]

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