[PATCH] D150742: [HWASan] Ignore shortgranules for global tag selection

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka added a comment.

Can you update some test?
Maybe it will trigger some test without ClUseShortGranules



================
Comment at: llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp:1588-1600
   for (GlobalVariable *GV : Globals) {
     Tag &= TagMaskByte;
-    // Skip tag 0 in order to avoid collisions with untagged memory.
-    if (Tag == 0)
+    if (ClUseShortGranules && Tag < 16) {
+      // Don't allow globals to be tagged with something that looks like a
+      // short-granule tag, otherwise we lose inter-granule overflow detection,
+      // as the fast path shadow-vs-address check succeeds.
+      Tag = 16;
----------------



================
Comment at: llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp:1590
     Tag &= TagMaskByte;
-    // Skip tag 0 in order to avoid collisions with untagged memory.
-    if (Tag == 0)
+    if (ClUseShortGranules && Tag < 16) {
+      // Don't allow globals to be tagged with something that looks like a
----------------
Tag &= TagMaskByte;
is effectively
Tag = Tag % (TagMaskByte + 1);

so to map them above 15:
Tag = 16 + Tag % (TagMaskByte + 1 - 16);




================
Comment at: llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp:1595
+      Tag = 16;
+    } else if (Tag == 0) {
+      // Skip tag 0 in order to avoid collisions with untagged memory.
----------------
let's remove conditions and do that all the time



Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D150742/new/

https://reviews.llvm.org/D150742