[all-commits] [llvm/llvm-project] 81360e: [CFI] Fix Direct Call Issues in CFI Dispatch Table...

[Oskar Wirga via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 81360ec58217c42b288d1267aba4836f880b19ba
      https://github.com/llvm/llvm-project/commit/81360ec58217c42b288d1267aba4836f880b19ba
  Author: Oskar Wirga <10386631+oskarwirga at users.noreply.github.com>
  Date:   2023-12-06 (Wed, 06 Dec 2023)

  Changed paths:
    M llvm/lib/Transforms/IPO/LowerTypeTests.cpp
    M llvm/test/Transforms/LowerTypeTests/aarch64-jumptable.ll
    A llvm/test/Transforms/LowerTypeTests/cfi-nounwind-direct-call.ll
    A llvm/test/Transforms/LowerTypeTests/cfi-unwind-direct-call.ll
    M llvm/test/Transforms/LowerTypeTests/function-arm-thumb.ll
    M llvm/test/Transforms/LowerTypeTests/function-thumb-bti.ll
    M llvm/test/Transforms/LowerTypeTests/function.ll
    M llvm/test/Transforms/LowerTypeTests/x86-jumptable.ll

  Log Message:
  -----------
  [CFI] Fix Direct Call Issues in CFI Dispatch Table (#69663)

I discovered two issues for when a CFI dispatch table entry is used as a
direct call.
# Inlining
There is the possibility that the dispatch table entry contains only a
single function pointer:
```
; Function Attrs: naked nocf_check
define private void @.cfi.jumptable() #6 align 8 { entry:
  call void asm sideeffect "jmp ${0:c}@plt\0Aint3\0Aint3\0Aint3\0A", "s"(ptr @_Z7throw_ei)
  unreachable
}
```
If this function is inlined, the unreachable follows and ruins the
containing function.
# Exception Handling
The dispatch table is always marked NoUnwind. This is fine if the
entries are never used directly, but if a direct call is used which the
containing function expects to throw, it will no longer throw and the
exception handling code will be lost.