[PATCH v6 0/2] static call support for arm64

[Ard Biesheuvel]

This implements non-inline static calls for arm64. This is rather
straight-forward, as we don't rely on any tooling to look for static
call sites etc. The only minor complication is Clang CFI, which is
already in mainline for arm64, and requires a little tweak to ensure
that we don't end up patching the CFI jump table instead of the static
call trampoline itself.

Changes since v5:
- drop the patch that works around issues with references to symbols
  with static linkage from asm blocks; this is specific to Clang+ThinLTO
  in versions before 13, so we can just decide not to support that config.
- add a patch to use non-function type symbols for the trampolines, to
  ensure that taking the address gives us the trampoline itself rather
  than the address of a CFI jump table entry that branches to it.

Changes since v4:
- add preparatory patch to address generic CFI/LTO issues with static
  calls
- add comment to patch #2 describing the trampoline layout
- add handling of Clang CFI jump table entries
- add PeterZ's ack to patch #2

Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Quentin Perret <qperret@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>

Ard Biesheuvel (2):
  static_call: use non-function types to refer to the trampolines
  arm64: implement support for static call trampolines

 arch/arm64/Kconfig                   |  2 +
 arch/arm64/include/asm/static_call.h | 40 ++++++++++
 arch/arm64/kernel/patching.c         | 77 +++++++++++++++++++-
 arch/arm64/kernel/vmlinux.lds.S      |  1 +
 include/linux/static_call.h          |  4 +-
 include/linux/static_call_types.h    | 11 ++-
 6 files changed, 127 insertions(+), 8 deletions(-)
 create mode 100644 arch/arm64/include/asm/static_call.h

-- 
2.30.2