[PATCH] D143915: [llvm][AArch64] Fix an interaction of SLS and BTI after a returns twice call

[David Spickett via Phabricator via llvm-commits]

DavidSpickett created this revision.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: All.
DavidSpickett requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This fixes the combination of two things:

- Placing a BTI after calls to a returns twice function like setjmp. This allows the setjmp to return with a br instead of a ret.
- Straight line speculation mitigations that replace BLR with a BL to a thunk that does the mitigation, and then goes to the original target.

Originally I marked AArch64call_bti as requiring that SLS mitigation
be disabled. This caused a crash when you tried to codegen with both.
Since CALL_BTI tried to match with AArch64call_bti but could not.

This change does 2 things:

- Follow the pattern set by AArch64call and add 2 patterns for AArch64call_bti. One with no IP (interprocedural) registers, and one with. For SLS mitigation off and on respectively.
- Modify the sls hardening pass to iterate through bundled instructions, as the AArch64 KCFI pass does.

Since there is a 1:1 replacement of the BLR with a BL,
the bundle remains intact. This is checked with an MIR test.

The ir -> asm testing is updated to add runs with the sls
mitigation enabled.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D143915

Files:
  llvm/lib/Target/AArch64/AArch64InstrInfo.td
  llvm/lib/Target/AArch64/AArch64SLSHardening.cpp
  llvm/test/CodeGen/AArch64/setjmp-bti.ll
  llvm/test/CodeGen/AArch64/speculation-hardening-sls-blr-bti.mir

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D143915.496978.patch
Type: text/x-patch
Size: 6926 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20230213/0515a4f9/attachment.bin>