================
@@ -612,6 +612,48 @@ void getAddressSanitizerParams(const Triple &TargetTriple,
int LongSize,
*OrShadowOffset = Mapping.OrShadowOffset;
}
+void removeASanIncompatibleFnAttributes(Function &F, bool RemoveWriteOnly) {
+ // Remove memory attributes that are invalid with ASan and HWSan.
+ // ASan checks read from shadow, which invalidates memory(argmem: *)
+ // Short granule checks on function arguments read from the argument memory
+ // (last byte of the granule), which invalidates writeonly.
+ //
+ // This is not only true for sanitized functions, because AttrInfer can
+ // infer those attributes on libc functions, which is not true if those
+ // are instrumented (Android) or intercepted.
+ //
+ // We might want to model ASan shadow memory more opaquely to get rid of
+ // this problem altogether, by hiding the shadow memory write in an
+ // intrinsic, essentially like in the AArch64StackTagging pass. But that's
+ // for another day.
+
+ // The API is weird. `onlyReadsMemory` actually means "does not write", and
+ // `onlyWritesMemory` actually means "does not read". So we reconstruct
+ // "accesses memory" && "does not read" <=> "writes".
+ bool Changed = false;
+ if (!F.doesNotAccessMemory()) {
+ bool WritesMemory = !F.onlyReadsMemory();
+ bool ReadsMemory = !F.onlyWritesMemory();
+ if ((WritesMemory && !ReadsMemory) || F.onlyAccessesArgMemory()) {
+ F.removeFnAttr(Attribute::Memory);
+ Changed = true;
+ }
+ }
+ if (RemoveWriteOnly) {
+ for (Argument &A : F.args()) {
+ if (A.hasAttribute(Attribute::WriteOnly)) {
+ A.removeAttr(Attribute::WriteOnly);
+ Changed = true;
+ }
+ }
+ }
+ if (Changed) {
+ // nobuiltin makes sure later passes don't restore assumptions about
+ // the function.
+ F.addFnAttr(Attribute::NoBuiltin);
+ }
+}
----------------
guy-david wrote:
I'm not completely following, can you explain what it means to "operate in
terms of Memory"?
https://github.com/llvm/llvm-project/pull/130495
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