[PATCH] D77477: tsan: don't instrument __attribute__((naked)) functions

[Anton Bikineev via Phabricator via llvm-commits]

AntonBikineev created this revision.
AntonBikineev added reviewers: kcc, dvyukov.
AntonBikineev added a project: LLVM.
Herald added a subscriber: hiraditya.

Naked functions must not have compiler generated prologues/epilogues, hence no instrumentation is needed for them.

I was not sure whether to disable instrumentation for an entire function or only for prologues/epilogues (__tsan_func_entry/__tsan_func_exit), but I assumed that the latter would probably be incorrect. Please let me if you think this is wrong.

FWIW, from the C/C++ frontend point of view, naked functions can only contain inline assembly.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77477

Files:
  llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
  llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll


Index: llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll
===================================================================
--- llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll
+++ llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll
@@ -78,5 +78,18 @@
   call void @SwiftError(i8** %0)
   ret void
 }
+
+; CHECK-LABEL: @NakedTest(i32* %a)
+; CHECK-NEXT:   call void @foo()
+; CHECK-NEXT:   %tmp1 = load i32, i32* %a, align 4
+; CHECK-NEXT:   ret i32 %tmp1
+define i32 @NakedTest(i32* %a) naked sanitize_thread {
+  call void @foo()
+  %tmp1 = load i32, i32* %a, align 4
+  ret i32 %tmp1
+}
+
+declare void @foo() nounwind
+
 ; CHECK: define internal void @tsan.module_ctor()
 ; CHECK: call void @__tsan_init()
Index: llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -441,6 +441,11 @@
   // the module constructor.
   if (F.getName() == kTsanModuleCtorName)
     return false;
+  // Naked functions can not have prologue/epilogue
+  // (__tsan_func_entry/__tsan_func_exit) generated, so don't instrument them at
+  // all.
+  if (F.hasFnAttribute(Attribute::Naked))
+    return false;
   initialize(*F.getParent());
   SmallVector<Instruction*, 8> AllLoadsAndStores;
   SmallVector<Instruction*, 8> LocalLoadsAndStores;


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