[PATCH] D108478: [llvm][IR] Add no_cfi constant

[Sami Tolvanen via Phabricator via llvm-commits]

samitolvanen created this revision.
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With Control-Flow Integrity (CFI), the LowerTypeTests pass replaces
function references with CFI jump table references, which is a problem
for low-level code that needs the address of the actual function body.

For example, in the Linux kernel, the code that sets up interrupt
handlers needs to take the address of the interrupt handler function
instead of the CFI jump table, as the jump table may not even be mapped
into memory when an interrupt is triggered.

This change adds the no_cfi constant type, which wraps function
references in a value that LowerTypeTestsModule::replaceCfiUses does not
replace.

Link: https://github.com/ClangBuiltLinux/linux/issues/1353


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108478

Files:
  llvm/docs/LangRef.rst
  llvm/include/llvm/AsmParser/LLParser.h
  llvm/include/llvm/AsmParser/LLToken.h
  llvm/include/llvm/Bitcode/LLVMBitCodes.h
  llvm/include/llvm/IR/Constants.h
  llvm/include/llvm/IR/Value.def
  llvm/lib/AsmParser/LLLexer.cpp
  llvm/lib/AsmParser/LLParser.cpp
  llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
  llvm/lib/Bitcode/Reader/BitcodeReader.cpp
  llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
  llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/IR/AsmWriter.cpp
  llvm/lib/IR/Constants.cpp
  llvm/lib/IR/LLVMContextImpl.h
  llvm/lib/Transforms/IPO/LowerTypeTests.cpp
  llvm/lib/Transforms/Utils/ValueMapper.cpp
  llvm/test/Bitcode/nocfivalue.ll
  llvm/test/CodeGen/X86/nocfivalue.ll
  llvm/test/Transforms/LowerTypeTests/nocfivalue.ll

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