[PATCH] D104266: [DFSan] Handle landingpad inst explicitly as zero shadow.

[Andrew via Phabricator via llvm-commits]

browneee updated this revision to Diff 352310.
browneee marked 2 inline comments as done.
browneee added a comment.

Updated comments.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D104266/new/

https://reviews.llvm.org/D104266

Files:
  llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
  llvm/test/Instrumentation/DataFlowSanitizer/call.ll


Index: llvm/test/Instrumentation/DataFlowSanitizer/call.ll
===================================================================
--- llvm/test/Instrumentation/DataFlowSanitizer/call.ll
+++ llvm/test/Instrumentation/DataFlowSanitizer/call.ll
@@ -48,7 +48,7 @@
           catch i8* null
   %1 = extractvalue { i8*, i32 } %0, 0
 
-  ; CHECK: store {{.*}} @__dfsan_arg_tls
+  ; CHECK: store i8 0,{{.*}} @__dfsan_arg_tls
   ; CHECK: call {{.*}} @"dfs$__cxa_begin_catch"
   ; CHECK: load {{.*}} @__dfsan_retval_tls
   %2 = tail call i8* @__cxa_begin_catch(i8* %1)
Index: llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -721,6 +721,7 @@
   void visitBitCastInst(BitCastInst &BCI);
   void visitCastInst(CastInst &CI);
   void visitCmpInst(CmpInst &CI);
+  void visitLandingPadInst(LandingPadInst &LPI);
   void visitGetElementPtrInst(GetElementPtrInst &GEPI);
   void visitLoadInst(LoadInst &LI);
   void visitStoreInst(StoreInst &SI);
@@ -2561,6 +2562,22 @@
   }
 }
 
+void DFSanVisitor::visitLandingPadInst(LandingPadInst &LPI) {
+  // We do not need to track data through LandingPadInst.
+  //
+  // For the C++ exceptions, if a value is thrown, this value will be stored
+  // in a memory location provided by __cxa_allocate_exception(...) (on the
+  // throw side) or  __cxa_begin_catch(...) (on the catch side).
+  // This memory will have a shadow, so with the loads and stores we will be
+  // able to propagate labels on data thrown through exceptions, without any
+  // special handling of the LandingPadInst.
+  //
+  // The second element in the pair result of the LandingPadInst is a
+  // register value, but it is for a type ID and should never be tainted.
+  DFSF.setShadow(&LPI, DFSF.DFS.getZeroShadow(&LPI));
+  DFSF.setOrigin(&LPI, DFSF.DFS.ZeroOrigin);
+}
+
 void DFSanVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
   if (ClCombineOffsetLabelsOnGEP) {
     visitInstOperands(GEPI);


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