[asan] Fix size/alignment issues with non-default shadow scale

[waltl]

Summary

Fix a couple places where the minimum alignment/size should be a
function of the shadow granularity:

• alignment of AllGlobals
• the minimum left redzone size on the stack

Added a test to verify that the metadata_array is properly aligned
for shadow scale of 5, to be enabled when we add build support
for testing shadow scale of 5.

[waltl]

Miscellaneous cleanups.

[vitalybuka]

oh, could you please extend some test to cover this case?

[waltl]

Add test to verify metadata_array alignment

[waltl]

In D39470#922023, @vitalybuka wrote:

oh, could you please extend some test to cover this case?

Done.

[vitalybuka]

In D39470#923564, @waltl wrote:

Done.

Not sure how the recent patch tests --asan-mapping-scale=5

New tests could be additional "// RUN: opt... --asan-mapping-scale=5", with new CHECK prefixes
or just new files, maybe copied from existing tests. Potential candidates: instrument-stack.ll, adaptive_global_redzones.ll

[waltl]

In D39470#926732, @vitalybuka wrote:

Not sure how the recent patch tests --asan-mapping-scale=5

New tests could be additional "// RUN: opt... --asan-mapping-scale=5", with new CHECK prefixes
or just new files, maybe copied from existing tests. Potential candidates: instrument-stack.ll, adaptive_global_redzones.ll

Yes this patch doesn't test -asan-mapping-scale=5. That testing is added in https://reviews.llvm.org/D39775. Most of the instrumentation tests directly under llvm/test/Instrumentation/AddressSanitizer will be enabled for shadow scale 5, including the ones that you mentioned.

The most recent change here adds a test to verify that the metadata_array is properly aligned for shadow scale 5, and it will be automatically enabled once https://reviews.llvm.org/D39775 is submitted.

llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp

void AddressSanitizerModule::InstrumentGlobalsWithMetadataArray(
 
   // On platforms that don't have a custom metadata section, we emit an array
   // of global metadata structures.
   ArrayType *ArrayOfGlobalStructTy =
       ArrayType::get(MetadataInitializers[0]->getType(), N);
   auto AllGlobals = new GlobalVariable(
       M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
       ConstantArray::get(ArrayOfGlobalStructTy, MetadataInitializers), "");
+  if (Mapping.Scale > 3)
+    AllGlobals->setAlignment(1ULL << Mapping.Scale);
 
   IRB.CreateCall(AsanRegisterGlobals,
                  {IRB.CreatePointerCast(AllGlobals, IntptrTy),
                   ConstantInt::get(IntptrTy, N)});
 
   // We also need to unregister globals at the end, e.g., when a shared library
   // gets closed.
   IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
ASanStackVariableDescription D = {AI->getName().data(),
                                       AI,
                                       0,
                                       0};
     SVD.push_back(D);
   }
 
   // Minimal header size (left redzone) is 4 pointers,
   // i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
-  size_t MinHeaderSize = ASan.LongSize / 2;
+  size_t Granularity = 1ULL << Mapping.Scale;
+  size_t MinHeaderSize = std::max((size_t)ASan.LongSize / 2, Granularity);
   const ASanStackFrameLayout &L =
-      ComputeASanStackFrameLayout(SVD, 1ULL << Mapping.Scale, MinHeaderSize);
+      ComputeASanStackFrameLayout(SVD, Granularity, MinHeaderSize);
 
   // Build AllocaToSVDMap for ASanStackVariableDescription lookup.
   DenseMap<const AllocaInst *, ASanStackVariableDescription *> AllocaToSVDMap;
   for (auto &Desc : SVD)
     AllocaToSVDMap[Desc.AI] = &Desc;
 
   // Update SVD with information from lifetime intrinsics.
   for (const auto &APC : StaticAllocaPoisonCallVec) {

llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll

 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
 ; CHECK: [[FILENAME:@__asan_gen_.[0-9]+]] = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
 ; CHECK: [[LOCDESCR:@__asan_gen_.[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
 
 ; Check that location descriptors and global names were passed into __asan_register_globals:
 ; CHECK: i64 ptrtoint ([7 x i8]* [[VARNAME]] to i64)
 ; CHECK: i64 ptrtoint ({ [22 x i8]*, i32, i32 }* [[LOCDESCR]] to i64)
+; Check alignment of metadata_array.
+; CHECK-S5-SAME: {{align 32$}}
 
 ; Function Attrs: nounwind sanitize_address
 define internal void @__cxx_global_var_init() #0 section ".text.startup" {
 entry:
   %0 = load i32, i32* @global, align 4
   store i32 %0, i32* @dyn_init_global, align 4
   ret void
 }