[llvm-branch-commits] [WIP] LowerTypeTests: Start using !elf_section_properties metadata to mark CFI jump table sections. (PR #149261)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Peter Collingbourne (pcc)

<details>
<summary>Changes</summary>

TODO:
- Update tests.


---
Full diff: https://github.com/llvm/llvm-project/pull/149261.diff


2 Files Affected:

- (modified) compiler-rt/test/cfi/mfcall.cpp (+2-2) 
- (modified) llvm/lib/Transforms/IPO/LowerTypeTests.cpp (+21-9) 


``````````diff
diff --git a/compiler-rt/test/cfi/mfcall.cpp b/compiler-rt/test/cfi/mfcall.cpp
index d4666df8d5333..f95251f5adb44 100644
--- a/compiler-rt/test/cfi/mfcall.cpp
+++ b/compiler-rt/test/cfi/mfcall.cpp
@@ -63,12 +63,12 @@ int main(int argc, char **argv) {
   switch (argv[1][0]) {
     case 'a':
       // A: runtime error: control flow integrity check for type 'int (S::*)()' failed during non-virtual pointer to member function call
-      // A: note: S::f1() defined here
+      // A: note: S::f1() {{.*}}defined here
       (s.*bitcast<S_int>(&S::f1))();
       break;
     case 'b':
       // B: runtime error: control flow integrity check for type 'int (T::*)()' failed during non-virtual pointer to member function call
-      // B: note: S::f2() defined here
+      // B: note: S::f2() {{.*}}defined here
       (t.*bitcast<T_int>(&S::f2))();
       break;
     case 'c':
diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index 86e1ebf937dbe..8b21d81bc9678 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -30,6 +30,8 @@
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/TypeMetadataUtils.h"
 #include "llvm/Analysis/ValueTracking.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/DebugInfo/CodeView/CodeView.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
@@ -73,6 +75,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/TargetParser/Triple.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/IPO/CrossDSOCFI.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/ModuleUtils.h"
 #include <algorithm>
@@ -498,6 +501,10 @@ class LowerTypeTestsModule {
   GlobalVariable *GlobalAnnotation;
   DenseSet<Value *> FunctionAnnotations;
 
+  // Cross-DSO CFI emits jumptable entries for exported functions as well as
+  // address taken functions in case they are address taken in other modules.
+  bool CrossDsoCfi = M.getModuleFlag("Cross-DSO CFI") != nullptr;
+
   bool shouldExportConstantsAsAbsoluteSymbols();
   uint8_t *exportTypeId(StringRef TypeId, const TypeIdLowering &TIL);
   TypeIdLowering importTypeId(StringRef TypeId);
@@ -1527,10 +1534,19 @@ Triple::ArchType LowerTypeTestsModule::selectJumpTableArmEncoding(
 void LowerTypeTestsModule::createJumpTable(
     Function *F, ArrayRef<GlobalTypeMember *> Functions,
     Triple::ArchType JumpTableArch) {
-  std::string AsmStr, ConstraintStr;
-  raw_string_ostream AsmOS(AsmStr), ConstraintOS(ConstraintStr);
-  SmallVector<Value *, 16> AsmArgs;
-  AsmArgs.reserve(Functions.size() * 2);
+  unsigned JumpTableEntrySize = getJumpTableEntrySize(JumpTableArch);
+  // Give the jumptable section this type in order to enable jumptable
+  // relaxation. Only do this if cross-DSO CFI is disabled because jumptable
+  // relaxation violates cross-DSO CFI's restrictions on the ordering of the
+  // jumptable relative to other sections.
+  if (!CrossDsoCfi)
+    F->setMetadata(LLVMContext::MD_elf_section_properties,
+                   MDNode::get(F->getContext(),
+                               ArrayRef<Metadata *>{
+                                   ConstantAsMetadata::get(ConstantInt::get(
+                                       Int64Ty, ELF::SHT_LLVM_CFI_JUMP_TABLE)),
+                                   ConstantAsMetadata::get(ConstantInt::get(
+                                       Int64Ty, JumpTableEntrySize))}));
 
   BasicBlock *BB = BasicBlock::Create(M.getContext(), "entry", F);
   IRBuilder<> IRB(BB);
@@ -1552,7 +1568,7 @@ void LowerTypeTestsModule::createJumpTable(
   IRB.CreateUnreachable();
 
   // Align the whole table by entry size.
-  F->setAlignment(Align(getJumpTableEntrySize(JumpTableArch)));
+  F->setAlignment(Align(JumpTableEntrySize));
   // Skip prologue.
   // Disabled on win32 due to https://llvm.org/bugs/show_bug.cgi?id=28641#c3.
   // Luckily, this function does not get any prologue even without the
@@ -2119,10 +2135,6 @@ bool LowerTypeTestsModule::lower() {
   unsigned CurUniqueId = 0;
   SmallVector<MDNode *, 2> Types;
 
-  // Cross-DSO CFI emits jumptable entries for exported functions as well as
-  // address taken functions in case they are address taken in other modules.
-  const bool CrossDsoCfi = M.getModuleFlag("Cross-DSO CFI") != nullptr;
-
   struct ExportedFunctionInfo {
     CfiFunctionLinkage Linkage;
     MDNode *FuncMD; // {name, linkage, type[, type...]}

``````````

</details>


https://github.com/llvm/llvm-project/pull/149261