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

[Vitaly Buka via llvm-commits]

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@@ -600,6 +602,42 @@ 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;
+
+  Printf("\n");
+
+  if (flags()->poison_history_size <= 0) {
+    Printf(
+        "NOTE: the stack trace above identifies the code that *accessed* "
+        "the poisoned memory.\n");
+    Printf(
+        "To identify the code that *poisoned* the memory, try the "
+        "experimental setting ASAN_OPTIONS=poison_history_size=<size>.\n");
+    return;
+  }
+
+  struct PoisonRecord record;
+  if (FindPoisonRecord(addr, record)) {
+    StackTrace poison_stack = StackDepotGet(record.stack_id);
+    if (poison_stack.size == 0) {
+      Printf("ERROR: stack depot did not have a matching stack.\n");
----------------
vitalybuka wrote:

> "ERROR: stack depot did not have a matching stack.\n"

I would not consider this an error. Information is just not avalible.
I'd just quietly print nothing,

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