[compiler-rt] [asan] Add experimental 'track_poison' flag (PR #133175)

[Thurston Dang via llvm-commits]

================
@@ -600,6 +602,43 @@ static void PrintShadowMemoryForAddress(uptr addr) {
   Printf("%s", str.data());
 }
 
+static void CheckPoisonRecords(uptr addr) {
+  if (!AddrIsInMem(addr))
+    return;
+  uptr shadow_addr = MemToShadow(addr);
+  unsigned char poison_magic = *(reinterpret_cast<u8 *>(shadow_addr));
+
+  if (poison_magic != kAsanUserPoisonedMemoryMagic)
+    return;
+
+  PoisonRecordRingBuffer *PoisonRecord = AcquirePoisonRecords();
+  if (PoisonRecord) {
+    bool FoundMatch = false;
+
+    for (unsigned int i = 0; i < PoisonRecord->size(); i++) {
+      struct PoisonRecord Record = (*PoisonRecord)[i];
+      if (Record.begin <= addr && addr <= Record.end) {
+        FoundMatch = true;
+
+        StackTrace poison_stack = StackDepotGet(Record.stack_id);
+
+        Printf("\n");
+        Printf("Memory was manually poisoned by thread T%u:\n",
+               Record.thread_id);
+        poison_stack.Print();
+
+        break;
+      }
+    }
+
+    if (!FoundMatch) {
+      Printf("ERROR: no matching poison tracking record found.\n");
+      Printf("Try setting a larger track_poison value.\n");
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thurstond wrote:

Done

https://github.com/llvm/llvm-project/pull/133175