[HWASan] Use new IR attribute for communicating unsanitized globals.

[hctim]

Summary

Globals that shouldn't be sanitized are currently communicated to HWASan
through the use of the llvm.asan.globals IR metadata. Now that we have
an on-GV attribute, use it.

[hctim]

FYI - if you want to check that the attribute is being emitted correctly for sanitizer ignorelists, one uses the test in the parent patch: https://reviews.llvm.org/D126929#change-pnXipICIxofc

If you want to check that the attribute is being emitted correctly for __attribute__((no_sanitize('hwaddress'))), you'll have to check the child patch, as that's not currently possible :).

[hctim]

(friendly ping @pcc)

[pcc]

LGTM

llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp

void HWAddressSanitizer::instrumentGlobal(GlobalVariable *GV, uint8_t Tag) {
   auto *Alias = GlobalAlias::create(GV->getValueType(), GV->getAddressSpace(),
                                     GV->getLinkage(), "", Aliasee, &M);
   Alias->setVisibility(GV->getVisibility());
   Alias->takeName(GV);
   GV->replaceAllUsesWith(Alias);
   GV->eraseFromParent();
 }
 
-static DenseSet<GlobalVariable *> getExcludedGlobals(Module &M) {
-  NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
-  if (!Globals)
-    return DenseSet<GlobalVariable *>();
-  DenseSet<GlobalVariable *> Excluded(Globals->getNumOperands());
-  for (auto MDN : Globals->operands()) {
-    // Metadata node contains the global and the fields of "Entry".
-    assert(MDN->getNumOperands() == 5);
-    auto *V = mdconst::extract_or_null<Constant>(MDN->getOperand(0));
-    // The optimizer may optimize away a global entirely.
-    if (!V)
-      continue;
-    auto *StrippedV = V->stripPointerCasts();
-    auto *GV = dyn_cast<GlobalVariable>(StrippedV);
-    if (!GV)
-      continue;
-    ConstantInt *IsExcluded = mdconst::extract<ConstantInt>(MDN->getOperand(4));
-    if (IsExcluded->isOne())
-      Excluded.insert(GV);
-  }
-  return Excluded;
-}
-
 void HWAddressSanitizer::instrumentGlobals() {
   std::vector<GlobalVariable *> Globals;
-  auto ExcludedGlobals = getExcludedGlobals(M);
   for (GlobalVariable &GV : M.globals()) {
-    if (ExcludedGlobals.count(&GV))
+    if (GV.hasSanitizerMetadata() && GV.getSanitizerMetadata().NoHWAddress)
       continue;
 
     if (GV.isDeclarationForLinker() || GV.getName().startswith("llvm.") ||
         GV.isThreadLocal())
       continue;
 
     // Common symbols can't have aliases point to them, so they can't be tagged.
     if (GV.hasCommonLinkage())

llvm/test/Instrumentation/HWAddressSanitizer/globals.ll

 ; RUN: opt < %s -S -passes=hwasan -mtriple=aarch64--linux-android29 | FileCheck --check-prefixes=CHECK,CHECK29 %s
 ; RUN: opt < %s -S -passes=hwasan -mtriple=aarch64--linux-android30 | FileCheck --check-prefixes=CHECK,CHECK30 %s
 
 ; CHECK29: @four = global
 
-; CHECK: @specialcaselisted = global i16 2
+; CHECK: @specialcaselisted = global i16 2, no_sanitize_hwaddress
 
 ; CHECK: @__start_hwasan_globals = external hidden constant [0 x i8]
 ; CHECK: @__stop_hwasan_globals = external hidden constant [0 x i8]
 
-; CHECK: @hwasan.note = private constant { i32, i32, i32, [8 x i8], i32, i32 } { i32 8, i32 8, i32 3, [8 x i8] c"LLVM\00\00\00\00", i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__start_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__stop_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32) }, section ".note.hwasan.globals", comdat($hwasan.module_ctor), align 4
+; CHECK: @hwasan.note = private constant { i32, i32, i32, [8 x i8], i32, i32 } { i32 8, i32 8, i32 3, [8 x i8] c"LLVM\00\00\00\00", i32 trunc (i64 sub (i64 ptrtoint (ptr @__start_hwasan_globals to i64), i64 ptrtoint (ptr @hwasan.note to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @__stop_hwasan_globals to i64), i64 ptrtoint (ptr @hwasan.note to i64)) to i32) }, section ".note.hwasan.globals", comdat($hwasan.module_ctor), align 4
 
 ; CHECK: @hwasan.dummy.global = private constant [0 x i8] zeroinitializer, section "hwasan_globals", comdat($hwasan.module_ctor), !associated [[NOTE:![0-9]+]]
 
 ; CHECK30: @four.hwasan = private global { i32, [12 x i8] } { i32 1, [12 x i8] c"\00\00\00\00\00\00\00\00\00\00\00\AC" }, align 16
-; CHECK30: @four.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint ({ i32, [12 x i8] }* @four.hwasan to i64), i64 ptrtoint ({ i32, i32 }* @four.hwasan.descriptor to i64)) to i32), i32 -1409286140 }, section "hwasan_globals", !associated [[FOUR:![0-9]+]]
+; CHECK30: @four.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint (ptr @four.hwasan to i64), i64 ptrtoint (ptr @four.hwasan.descriptor to i64)) to i32), i32 -1409286140 }, section "hwasan_globals", !associated [[FOUR:![0-9]+]]
 
 ; CHECK30: @sixteen.hwasan = private global [16 x i8] zeroinitializer, align 16
-; CHECK30: @sixteen.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint ([16 x i8]* @sixteen.hwasan to i64), i64 ptrtoint ({ i32, i32 }* @sixteen.hwasan.descriptor to i64)) to i32), i32 -1392508912 }, section "hwasan_globals", !associated [[SIXTEEN:![0-9]+]]
+; CHECK30: @sixteen.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint (ptr @sixteen.hwasan to i64), i64 ptrtoint (ptr @sixteen.hwasan.descriptor to i64)) to i32), i32 -1392508912 }, section "hwasan_globals", !associated [[SIXTEEN:![0-9]+]]
 
 ; CHECK30: @huge.hwasan = private global [16777232 x i8] zeroinitializer, align 16
-; CHECK30: @huge.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint ([16777232 x i8]* @huge.hwasan to i64), i64 ptrtoint ({ i32, i32 }* @huge.hwasan.descriptor to i64)) to i32), i32 -1358954512 }, section "hwasan_globals", !associated [[HUGE:![0-9]+]]
-; CHECK30: @huge.hwasan.descriptor.1 = private constant { i32, i32 } { i32 trunc (i64 add (i64 sub (i64 ptrtoint ([16777232 x i8]* @huge.hwasan to i64), i64 ptrtoint ({ i32, i32 }* @huge.hwasan.descriptor.1 to i64)), i64 16777200) to i32), i32 -1375731680 }, section "hwasan_globals", !associated [[HUGE]]
+; CHECK30: @huge.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint (ptr @huge.hwasan to i64), i64 ptrtoint (ptr @huge.hwasan.descriptor to i64)) to i32), i32 -1358954512 }, section "hwasan_globals", !associated [[HUGE:![0-9]+]]
+; CHECK30: @huge.hwasan.descriptor.1 = private constant { i32, i32 } { i32 trunc (i64 add (i64 sub (i64 ptrtoint (ptr @huge.hwasan to i64), i64 ptrtoint (ptr @huge.hwasan.descriptor.1 to i64)), i64 16777200) to i32), i32 -1375731680 }, section "hwasan_globals", !associated [[HUGE]]
 
-; CHECK30: @four = alias i32, inttoptr (i64 add (i64 ptrtoint ({ i32, [12 x i8] }* @four.hwasan to i64), i64 -6052837899185946624) to i32*)
-; CHECK30: @sixteen = alias [16 x i8], inttoptr (i64 add (i64 ptrtoint ([16 x i8]* @sixteen.hwasan to i64), i64 -5980780305148018688) to [16 x i8]*)
-; CHECK30: @huge = alias [16777232 x i8], inttoptr (i64 add (i64 ptrtoint ([16777232 x i8]* @huge.hwasan to i64), i64 -5908722711110090752) to [16777232 x i8]*)
-
-; CHECK: [[NOTE]] = !{{{{}} i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note}
-; CHECK30: [[FOUR]] = !{{{{}} i32, [12 x i8] }* @four.hwasan}
-; CHECK30: [[SIXTEEN]] = !{[16 x i8]* @sixteen.hwasan}
-; CHECK30: [[HUGE]] = !{[16777232 x i8]* @huge.hwasan}
+; CHECK30: @four = alias i32, inttoptr (i64 add (i64 ptrtoint (ptr @four.hwasan to i64), i64 -6052837899185946624) to ptr)
+; CHECK30: @sixteen = alias [16 x i8], inttoptr (i64 add (i64 ptrtoint (ptr @sixteen.hwasan to i64), i64 -5980780305148018688) to ptr)
+; CHECK30: @huge = alias [16777232 x i8], inttoptr (i64 add (i64 ptrtoint (ptr @huge.hwasan to i64), i64 -5908722711110090752) to ptr)
+
+; CHECK: [[NOTE]] = !{ptr @hwasan.note}
+; CHECK30: [[FOUR]] = !{ptr @four.hwasan}
+; CHECK30: [[SIXTEEN]] = !{ptr @sixteen.hwasan}
+; CHECK30: [[HUGE]] = !{ptr @huge.hwasan}
 
 source_filename = "foo"
 
 @four = global i32 1
 @sixteen = global [16 x i8] zeroinitializer
 @huge = global [16777232 x i8] zeroinitializer
-@specialcaselisted = global i16 2
-
-!llvm.asan.globals = !{!0}
-!0 = !{i16* @specialcaselisted, null, null, i1 false, i1 true}
+@specialcaselisted = global i16 2, no_sanitize_hwaddress