[rtsan][llvm][NFC] Rename sanitize_realtime_unsafe attr to sanitize_realtime_blocking (#113155)

# What

This PR renames the newly-introduced llvm attribute
`sanitize_realtime_unsafe` to `sanitize_realtime_blocking`. Likewise,
sibling variables such as `SanitizeRealtimeUnsafe` are renamed to
`SanitizeRealtimeBlocking` respectively. There are no other functional
changes.


# Why?

- There are a number of problems that can cause a function to be
real-time "unsafe",
- we wish to communicate what problems rtsan detects and *why* they're
unsafe, and
- a generic "unsafe" attribute is, in our opinion, too broad a net -
which may lead to future implementations that need extra contextual
information passed through them in order to communicate meaningful
reasons to users.
- We want to avoid this situation and make the runtime library boundary
API/ABI as simple as possible, and
- we believe that restricting the scope of attributes to names like
`sanitize_realtime_blocking` is an effective means of doing so.

We also feel that the symmetry between `[[clang::blocking]]` and
`sanitize_realtime_blocking` is easier to follow as a developer.

# Concerns

- I'm aware that the LLVM attribute `sanitize_realtime_unsafe` has been
part of the tree for a few weeks now (introduced here:
#106754). Given that it hasn't
been released in version 20 yet, am I correct in considering this to not
be a breaking change?

Author: davidtrevelyan

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -852,7 +852,7 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
         if (Fe.Effect.kind() == FunctionEffect::Kind::NonBlocking)
           Fn->addFnAttr(llvm::Attribute::SanitizeRealtime);
         else if (Fe.Effect.kind() == FunctionEffect::Kind::Blocking)
-          Fn->addFnAttr(llvm::Attribute::SanitizeRealtimeUnsafe);
+          Fn->addFnAttr(llvm::Attribute::SanitizeRealtimeBlocking);
       }
 
   // Apply fuzzing attribute to the function.

clang/test/CodeGen/rtsan_attribute_inserted.c

@@ -8,4 +8,4 @@ float process(float *a) [[clang::nonblocking]] { return *a; }
 int spinlock(int *a) [[clang::blocking]] { return *a; }
 // CHECK: @spinlock{{.*}} #1 {
 // CHECK: attributes #1 = {
-// CHECK-SAME: {{.*sanitize_realtime_unsafe .*}}
+// CHECK-SAME: {{.*sanitize_realtime_blocking .*}}

clang/test/CodeGen/rtsan_no_attribute_sanitizer_disabled.c

@@ -5,4 +5,4 @@ int spinlock(int *a) [[clang::blocking]] { return *a; }
 
 // Without the -fsanitize=realtime flag, we shouldn't attach the attributes.
 // CHECK-NOT: {{.*sanitize_realtime .*}}
-// CHECK-NOT: {{.*sanitize_realtime_unsafe .*}}
+// CHECK-NOT: {{.*sanitize_realtime_blocking .*}}

compiler-rt/lib/rtsan/tests/rtsan_test_functional.cpp

@@ -204,11 +204,11 @@ TEST(TestRtsan, ThrowingAnExceptionDiesWhenRealtime) {
 
 TEST(TestRtsan, DoesNotDieIfTurnedOff) {
   std::mutex mutex;
-  auto RealtimeUnsafeFunc = [&]() {
+  auto RealtimeBlockingFunc = [&]() {
     __rtsan_disable();
     mutex.lock();
     mutex.unlock();
     __rtsan_enable();
   };
-  RealtimeInvoke(RealtimeUnsafeFunc);
+  RealtimeInvoke(RealtimeBlockingFunc);
 }

llvm/docs/LangRef.rst

@@ -2334,7 +2334,7 @@ example:
     This attribute indicates that RealtimeSanitizer checks
     (realtime safety analysis - no allocations, syscalls or exceptions) are enabled
     for this function.
-``sanitize_realtime_unsafe``
+``sanitize_realtime_blocking``
     This attribute indicates that RealtimeSanitizer should error immediately
     if the attributed function is called during invocation of a function
     attributed with ``sanitize_realtime``.

llvm/include/llvm/Bitcode/LLVMBitCodes.h

@@ -768,7 +768,7 @@ enum AttributeKindCodes {
   ATTR_KIND_INITIALIZES = 94,
   ATTR_KIND_HYBRID_PATCHABLE = 95,
   ATTR_KIND_SANITIZE_REALTIME = 96,
-  ATTR_KIND_SANITIZE_REALTIME_UNSAFE = 97,
+  ATTR_KIND_SANITIZE_REALTIME_BLOCKING = 97,
   ATTR_KIND_CORO_ELIDE_SAFE = 98,
   ATTR_KIND_NO_EXT = 99,
   ATTR_KIND_NO_DIVERGENCE_SOURCE = 100,

llvm/include/llvm/IR/Attributes.td

@@ -334,7 +334,7 @@ def SanitizeRealtime : EnumAttr<"sanitize_realtime", IntersectPreserve, [FnAttr]
 
 /// RealtimeSanitizer should error if a real-time unsafe function is invoked
 /// during a real-time sanitized function (see `sanitize_realtime`).
-def SanitizeRealtimeUnsafe : EnumAttr<"sanitize_realtime_unsafe", IntersectPreserve, [FnAttr]>;
+def SanitizeRealtimeBlocking : EnumAttr<"sanitize_realtime_blocking", IntersectPreserve, [FnAttr]>;
 
 /// Speculative Load Hardening is enabled.
 ///
@@ -430,7 +430,7 @@ def : CompatRule<"isEqual<SanitizeHWAddressAttr>">;
 def : CompatRule<"isEqual<SanitizeMemTagAttr>">;
 def : CompatRule<"isEqual<SanitizeNumericalStabilityAttr>">;
 def : CompatRule<"isEqual<SanitizeRealtimeAttr>">;
-def : CompatRule<"isEqual<SanitizeRealtimeUnsafeAttr>">;
+def : CompatRule<"isEqual<SanitizeRealtimeBlockingAttr>">;
 def : CompatRule<"isEqual<SafeStackAttr>">;
 def : CompatRule<"isEqual<ShadowCallStackAttr>">;
 def : CompatRule<"isEqual<UseSampleProfileAttr>">;

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2165,8 +2165,8 @@ static Attribute::AttrKind getAttrFromCode(uint64_t Code) {
     return Attribute::SanitizeNumericalStability;
   case bitc::ATTR_KIND_SANITIZE_REALTIME:
     return Attribute::SanitizeRealtime;
-  case bitc::ATTR_KIND_SANITIZE_REALTIME_UNSAFE:
-    return Attribute::SanitizeRealtimeUnsafe;
+  case bitc::ATTR_KIND_SANITIZE_REALTIME_BLOCKING:
+    return Attribute::SanitizeRealtimeBlocking;
   case bitc::ATTR_KIND_SPECULATIVE_LOAD_HARDENING:
     return Attribute::SpeculativeLoadHardening;
   case bitc::ATTR_KIND_SWIFT_ERROR:

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -853,8 +853,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_SANITIZE_NUMERICAL_STABILITY;
   case Attribute::SanitizeRealtime:
     return bitc::ATTR_KIND_SANITIZE_REALTIME;
-  case Attribute::SanitizeRealtimeUnsafe:
-    return bitc::ATTR_KIND_SANITIZE_REALTIME_UNSAFE;
+  case Attribute::SanitizeRealtimeBlocking:
+    return bitc::ATTR_KIND_SANITIZE_REALTIME_BLOCKING;
   case Attribute::SpeculativeLoadHardening:
     return bitc::ATTR_KIND_SPECULATIVE_LOAD_HARDENING;
   case Attribute::SwiftError:

llvm/lib/IR/Verifier.cpp

@@ -2235,9 +2235,9 @@ void Verifier::verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
   }
 
   Check(!(Attrs.hasFnAttr(Attribute::SanitizeRealtime) &&
-          Attrs.hasFnAttr(Attribute::SanitizeRealtimeUnsafe)),
+          Attrs.hasFnAttr(Attribute::SanitizeRealtimeBlocking)),
         "Attributes "
-        "'sanitize_realtime and sanitize_realtime_unsafe' are incompatible!",
+        "'sanitize_realtime and sanitize_realtime_blocking' are incompatible!",
         V);
 
   if (Attrs.hasFnAttr(Attribute::OptimizeForDebugging)) {

llvm/lib/Transforms/Instrumentation/RealtimeSanitizer.cpp

@@ -69,7 +69,7 @@ static PreservedAnalyses runSanitizeRealtime(Function &Fn) {
   return rtsanPreservedCFGAnalyses();
 }
 
-static PreservedAnalyses runSanitizeRealtimeUnsafe(Function &Fn) {
+static PreservedAnalyses runSanitizeRealtimeBlocking(Function &Fn) {
   IRBuilder<> Builder(&Fn.front().front());
   Value *Name = Builder.CreateGlobalString(demangle(Fn.getName()));
   insertCallAtFunctionEntryPoint(Fn, "__rtsan_notify_blocking_call", {Name});
@@ -84,8 +84,8 @@ PreservedAnalyses RealtimeSanitizerPass::run(Function &Fn,
   if (Fn.hasFnAttribute(Attribute::SanitizeRealtime))
     return runSanitizeRealtime(Fn);
 
-  if (Fn.hasFnAttribute(Attribute::SanitizeRealtimeUnsafe))
-    return runSanitizeRealtimeUnsafe(Fn);
+  if (Fn.hasFnAttribute(Attribute::SanitizeRealtimeBlocking))
+    return runSanitizeRealtimeBlocking(Fn);
 
   return PreservedAnalyses::all();
 }

llvm/lib/Transforms/Utils/CodeExtractor.cpp

@@ -953,7 +953,7 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
       case Attribute::SanitizeHWAddress:
       case Attribute::SanitizeMemTag:
       case Attribute::SanitizeRealtime:
-      case Attribute::SanitizeRealtimeUnsafe:
+      case Attribute::SanitizeRealtimeBlocking:
       case Attribute::SpeculativeLoadHardening:
       case Attribute::StackProtect:
       case Attribute::StackProtectReq:

llvm/test/Bitcode/attributes.ll

@@ -512,7 +512,7 @@ define void @f92() sanitize_realtime
 }
 
 ; CHECK: define void @f93() #54
-define void @f93() sanitize_realtime_unsafe {
+define void @f93() sanitize_realtime_blocking {
         ret void;
 }
 
@@ -616,7 +616,7 @@ define void @initializes(ptr initializes((-4, 0), (4, 8)) %a) {
 ; CHECK: attributes #51 = { uwtable(sync) }
 ; CHECK: attributes #52 = { nosanitize_bounds }
 ; CHECK: attributes #53 = { sanitize_realtime }
-; CHECK: attributes #54 = { sanitize_realtime_unsafe }
+; CHECK: attributes #54 = { sanitize_realtime_blocking }
 ; CHECK: attributes [[FNRETTHUNKEXTERN]] = { fn_ret_thunk_extern }
 ; CHECK: attributes [[SKIPPROFILE]] = { skipprofile }
 ; CHECK: attributes [[OPTDEBUG]] = { optdebug }

llvm/test/Bitcode/compatibility.ll

@@ -2048,8 +2048,8 @@ declare void @f.sanitize_numerical_stability() sanitize_numerical_stability
 declare void @f.sanitize_realtime() sanitize_realtime
 ; CHECK: declare void @f.sanitize_realtime() #52
 
-declare void @f.sanitize_realtime_unsafe() sanitize_realtime_unsafe
-; CHECK: declare void @f.sanitize_realtime_unsafe() #53
+declare void @f.sanitize_realtime_blocking() sanitize_realtime_blocking
+; CHECK: declare void @f.sanitize_realtime_blocking() #53
 
 ; CHECK: declare nofpclass(snan) float @nofpclass_snan(float nofpclass(snan))
 declare nofpclass(snan) float @nofpclass_snan(float nofpclass(snan))
@@ -2183,7 +2183,7 @@ define float @nofpclass_callsites(float %arg, { float } %arg1) {
 ; CHECK: attributes #50 = { allockind("alloc,uninitialized") }
 ; CHECK: attributes #51 = { sanitize_numerical_stability }
 ; CHECK: attributes #52 = { sanitize_realtime }
-; CHECK: attributes #53 = { sanitize_realtime_unsafe }
+; CHECK: attributes #53 = { sanitize_realtime_blocking }
 ; CHECK: attributes #54 = { builtin }
 
 ;; Metadata

llvm/test/Instrumentation/RealtimeSanitizer/rtsan_unsafe.ll renamed to llvm/test/Instrumentation/RealtimeSanitizer/rtsan_blocking.ll

@@ -25,7 +25,7 @@ define noundef i32 @main() #2 {
   ret i32 0
 }
 
-attributes #0 = { mustprogress noinline sanitize_realtime_unsafe optnone ssp uwtable(sync) }
+attributes #0 = { mustprogress noinline sanitize_realtime_blocking optnone ssp uwtable(sync) }
 ;.
-; CHECK: attributes #[[ATTR0]] = { mustprogress noinline optnone sanitize_realtime_unsafe ssp uwtable(sync) }
+; CHECK: attributes #[[ATTR0]] = { mustprogress noinline optnone sanitize_realtime_blocking ssp uwtable(sync) }
 ;.

llvm/test/Verifier/rtsan-attrs.ll

@@ -1,9 +1,9 @@
 ; RUN: not llvm-as -disable-output %s 2>&1 | FileCheck %s
 
-; CHECK: Attributes 'sanitize_realtime and sanitize_realtime_unsafe' are incompatible!
+; CHECK: Attributes 'sanitize_realtime and sanitize_realtime_blocking' are incompatible!
 ; CHECK-NEXT: ptr @sanitize_unsafe
 define void @sanitize_unsafe() #0 {
   ret void
 }
 
-attributes #0 = { sanitize_realtime sanitize_realtime_unsafe }
+attributes #0 = { sanitize_realtime sanitize_realtime_blocking }