[Asan] Unpoison red zones even if use-after-scope was disabled with runtime flag

[vitalybuka]

Summary

PR27453

[eugenis]

LGTM with a test

[vitalybuka]

tests

[eugenis]

test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll

32

I thought the syntax is "CHECK-UAS-NEXT" ?

[vitalybuka]

test

lib/Transforms/Instrumentation/AddressSanitizer.cpp

Value *BasePlus2 = IRB.CreateIntToPtr(
       IntptrPtrTy);
   IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
 
   // Poison the stack redzones at the entry.
   Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
   poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true);
 
   auto UnpoisonStack = [&](IRBuilder<> &IRB) {
+    // Do this always as poisonAlloca can be disabled with
+    // detect_stack_use_after_scope=0.
+    poisonRedZones(L.ShadowBytes, IRB, ShadowBase, false);
     if (HavePoisonedStaticAllocas) {
       // If we poisoned some allocas in llvm.lifetime analysis,
       // unpoison whole stack frame now.
       poisonAlloca(LocalStackBase, LocalStackSize, IRB, false);
-    } else {
-      poisonRedZones(L.ShadowBytes, IRB, ShadowBase, false);
     }
   };
 
   // (Un)poison the stack before all ret instructions.
   for (auto Ret : RetVec) {
     IRBuilder<> IRBRet(Ret);
     // Mark the current frame as retired.
     IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),

test/Instrumentation/AddressSanitizer/lifetime-uar-uas.ll

entry:
   store volatile i32 0, i32* %retval
   store volatile i8 0, i8* %c, align 1
 
   call void @llvm.lifetime.end(i64 1, i8* %c)
   ; Memory is poisoned at llvm.lifetime.end
   ; CHECK-UAS: call void @__asan_poison_stack_memory(i64 %{{[^ ]+}}, i64 1)
 
   ; Unpoison memory at function exit in UAS mode.
-  ; CHECK-UAS: call void @__asan_unpoison_stack_memory(i64 %{{[^ ]+}}, i64 64)
-  ; CHECK-UAS: ret void
-
+  ; CHECK-UAS: store i64 0
+  ; CHECK-NEXT-UAS: call void @__asan_unpoison_stack_memory(i64 %{{[^ ]+}}, i64 64)
+  ; CHECK-NEXT-UAS: ret i32 0
   ret i32 0
 }
 
 ; No poisoning/poisoning at all in plain mode.
 ; CHECK-NOT: __asan_poison_stack_memory
 ; CHECK-NOT: __asan_unpoison_stack_memory

test/Instrumentation/AddressSanitizer/lifetime.ll

entry:
   ; CHECK: __asan_unpoison_stack_memory
 
   store i8* %0, i8** %d, align 8
 
   call void @llvm.lifetime.end(i64 1024, i8* %0)
   ; CHECK: __asan_poison_stack_memory
 
   ret void
-  ; CHECK: __asan_unpoison_stack_memory
+  ; CHECK: store i64 0
+  ; CHECK: store i64 0
+  ; CHECK: store i64 0
+  ; CHECK: store i32 0
+  ; CHECK-NEXT: __asan_unpoison_stack_memory
 }
 
 define void @zero_sized(i64 %a) #0 {
 ; CHECK-LABEL: define void @zero_sized(i64 %a)
 
 entry:
   %a.addr = alloca i64, align 8
   %b = alloca [0 x i8], align 1