[llvm] [hwasan] Allow stack traces even when fixed shadow is used (PR #109344)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

Previously, fixed shadow implied !InTls, and !InTls implied no stack traces, but InTls implied it would not use a fixed shadow. This patch changes fixed shadow to be compatible with stack traces.

It maintains the legacy behavior for KHWAsan || InstrumentWithCalls.

---
Full diff: https://github.com/llvm/llvm-project/pull/109344.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp (+10-7) 


``````````diff
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 7a5c690c7ea512..4bdf5b97aeb704 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -1340,7 +1340,7 @@ Value *HWAddressSanitizer::getFrameRecordInfo(IRBuilder<> &IRB) {
 }
 
 void HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord) {
-  if (!Mapping.InTls)
+  if (!Mapping.InTls || (Mapping.Offset != 0 && Mapping.Offset != kDynamicShadowSentinel))
     ShadowBase = getShadowNonTls(IRB);
   else if (!WithFrameRecord && TargetTriple.isAndroid())
     ShadowBase = getDynamicShadowIfunc(IRB);
@@ -1897,16 +1897,19 @@ void HWAddressSanitizer::ShadowMapping::init(Triple &TargetTriple,
     InTls = false;
     Offset = 0;
     WithFrameRecord = true;
-  } else if (ClMappingOffset.getNumOccurrences() > 0) {
-    InGlobal = false;
-    InTls = false;
-    Offset = ClMappingOffset;
-    WithFrameRecord = false;
   } else if (ClEnableKhwasan || InstrumentWithCalls) {
     InGlobal = false;
     InTls = false;
-    Offset = 0;
+    if (ClMappingOffset.getNumOccurrences() > 0)
+      Offset = ClMappingOffset;
+    else
+      Offset = 0;
     WithFrameRecord = false;
+  } else if (ClMappingOffset.getNumOccurrences() > 0) {
+    InGlobal = false;
+    InTls = true;
+    Offset = ClMappingOffset;
+    WithFrameRecord = true;
   } else if (ClWithIfunc) {
     InGlobal = true;
     InTls = false;

``````````

</details>


https://github.com/llvm/llvm-project/pull/109344