[PATCH] D100251: [IR][sanitizer] Set nounwind on module ctor/dtor, additionally set uwtable if -fasynchronous-unwind-tables

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: Sanitizers, jdoerfert, joerg, nickdesaulniers, rnk.
Herald added subscribers: dexonsmith, hiraditya.
MaskRay requested review of this revision.
Herald added projects: clang, LLVM.
Herald added subscribers: llvm-commits, cfe-commits.

On ELF targets, if a function has uwtable or personality, or does not have
nounwind (`needsUnwindTableEntry`), it marks that `.eh_frame` is needed in the module.

Then, a function gets `.eh_frame` if `needsUnwindTableEntry` or `-g[123]` is specified.
(i.e. If -g[123], every function gets `.eh_frame`.
This behavior is strange but that is the status quo on GCC and Clang.)

Let's take asan as an example. Other sanitizers are similar.
`asan.module_[cd]tor` has no attribute. `needsUnwindTableEntry` returns true,
so every function gets `.eh_frame` if `-g[123]` is specified.
This is the root cause that
`-fno-exceptions -fno-asynchronous-unwind-tables -g` produces .debug_frame
while
`-fno-exceptions -fno-asynchronous-unwind-tables -g -fsanitize=address` produces .eh_frame.

This patch

- sets the nounwind attribute on sanitizer module ctor/dtor.
- let Clang emit a module flag metadata "uwtable" for -fasynchronous-unwind-tables. If "uwtable" is set, sanitizer module ctor/dtor additionally get the uwtable attribute.

The "uwtable" mechanism is generic: synthesized functions not cloned/specialized
from existing ones should consider `Function::createWithDefaultAttr` instead of
`Function::create` if they want to get some default attributes which
have more of module semantics.

Other candidates: "frame-pointer" (https://github.com/ClangBuiltLinux/linux/issues/955
https://github.com/ClangBuiltLinux/linux/issues/1238), dso_local, etc.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100251

Files:
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/asan-globals.cpp
  clang/test/CodeGen/asan-new-pm.ll
  clang/test/CodeGen/asan-no-globals-no-comdat.cpp
  llvm/include/llvm/IR/Function.h
  llvm/include/llvm/IR/Module.h
  llvm/lib/IR/Function.cpp
  llvm/lib/IR/Module.cpp
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
  llvm/lib/Transforms/Utils/ModuleUtils.cpp
  llvm/test/Instrumentation/AddressSanitizer/basic.ll
  llvm/test/Instrumentation/AddressSanitizer/no-globals.ll
  llvm/test/Instrumentation/AddressSanitizer/uwtable.ll
  llvm/test/Instrumentation/HWAddressSanitizer/basic.ll
  llvm/test/Instrumentation/HWAddressSanitizer/with-calls.ll
  llvm/test/Instrumentation/MemorySanitizer/msan_basic.ll
  llvm/test/Instrumentation/SanitizerCoverage/trace-pc-guard-inline-8bit-counters.ll
  llvm/test/Instrumentation/SanitizerCoverage/trace-pc-guard-inline-bool-flag.ll
  llvm/test/Instrumentation/SanitizerCoverage/trace-pc-guard.ll

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