[SanitizerBinaryMetadata] Make constructors/destructors hidden

[melver]

Summary

By switching them to external with default visibility, DSOs may not call
their own constructor/destructor. This is incorrect, because they pass
different parameters.

Fix it by marking the ctors/dtors as external linkage but with hidden
visibility.

llvm/lib/Transforms/Instrumentation/SanitizerBinaryMetadata.cpp

Function *Ctor =
             /*VersionCheckName=*/StringRef(), /*Weak=*/ClWeakCallbacks)
             .first;
     Function *Dtor =
         createSanitizerCtorAndInitFunctions(
             Mod, (MI->FunctionPrefix + ".module_dtor").str(),
             (MI->FunctionPrefix + "_del").str(), InitTypes, InitArgs,
             /*VersionCheckName=*/StringRef(), /*Weak=*/ClWeakCallbacks)
             .first;
-    Constant *CtorData = nullptr;
-    Constant *DtorData = nullptr;
+    Constant *CtorComdatKey = nullptr;
+    Constant *DtorComdatKey = nullptr;
     if (TargetTriple.supportsCOMDAT()) {
       // Use COMDAT to deduplicate constructor/destructor function. The COMDAT
       // key needs to be a non-local linkage.
       Ctor->setComdat(Mod.getOrInsertComdat(Ctor->getName()));
       Dtor->setComdat(Mod.getOrInsertComdat(Dtor->getName()));
       Ctor->setLinkage(GlobalValue::ExternalLinkage);
       Dtor->setLinkage(GlobalValue::ExternalLinkage);
-      CtorData = Ctor;
-      DtorData = Dtor;
+      // DSOs should _not_ call another constructor/destructor!
+      Ctor->setVisibility(GlobalValue::HiddenVisibility);
+      Dtor->setVisibility(GlobalValue::HiddenVisibility);
+      CtorComdatKey = Ctor;
+      DtorComdatKey = Dtor;
     }
-    appendToGlobalCtors(Mod, Ctor, kCtorDtorPriority, CtorData);
-    appendToGlobalDtors(Mod, Dtor, kCtorDtorPriority, DtorData);
+    appendToGlobalCtors(Mod, Ctor, kCtorDtorPriority, CtorComdatKey);
+    appendToGlobalDtors(Mod, Dtor, kCtorDtorPriority, DtorComdatKey);
   }
 
   return true;
 }
 
 void SanitizerBinaryMetadata::runOn(Function &F, MetadataInfoSet &MIS) {
   if (F.empty())
     return;

llvm/test/Instrumentation/SanitizerBinaryMetadata/ctor.ll

 ; RUN: opt < %s -passes='module(sanmd-module)' -sanitizer-metadata-atomics -S | FileCheck %s
 
 ; CHECK: $__sanitizer_metadata_atomics.module_ctor = comdat any
 ; CHECK: $__sanitizer_metadata_atomics.module_dtor = comdat any
 ; CHECK: $__sanitizer_metadata_covered.module_ctor = comdat any
 ; CHECK: $__sanitizer_metadata_covered.module_dtor = comdat any
 
 ; CHECK: @llvm.used = appending global [4 x ptr] [ptr @__sanitizer_metadata_atomics.module_ctor, ptr @__sanitizer_metadata_atomics.module_dtor, ptr @__sanitizer_metadata_covered.module_ctor, ptr @__sanitizer_metadata_covered.module_dtor], section "llvm.metadata"
 ; CHECK: @llvm.global_ctors = appending global [2 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 2, ptr @__sanitizer_metadata_atomics.module_ctor, ptr @__sanitizer_metadata_atomics.module_ctor }, { i32, ptr, ptr } { i32 2, ptr @__sanitizer_metadata_covered.module_ctor, ptr @__sanitizer_metadata_covered.module_ctor }]
 ; CHECK: @llvm.global_dtors = appending global [2 x { i32, ptr, ptr }] [{ i32, ptr, ptr } { i32 2, ptr @__sanitizer_metadata_atomics.module_dtor, ptr @__sanitizer_metadata_atomics.module_dtor }, { i32, ptr, ptr } { i32 2, ptr @__sanitizer_metadata_covered.module_dtor, ptr @__sanitizer_metadata_covered.module_dtor }]
 
-; CHECK: define dso_local void @__sanitizer_metadata_covered.module_ctor() #1 comdat {
-; CHECK: define dso_local void @__sanitizer_metadata_covered.module_dtor() #1 comdat {
+; CHECK: define hidden void @__sanitizer_metadata_covered.module_ctor() #1 comdat {
+; CHECK: define hidden void @__sanitizer_metadata_covered.module_dtor() #1 comdat {
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define i8 @foo(ptr %a) nounwind uwtable {
 entry:
   %0 = load atomic i8, ptr %a unordered, align 1
   ret i8 %0
 }