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

[Thurston Dang via llvm-commits]

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@@ -107,6 +144,31 @@ void __asan_poison_memory_region(void const volatile *addr, uptr size) {
   uptr end_addr = beg_addr + size;
   VPrintf(3, "Trying to poison memory region [%p, %p)\n", (void *)beg_addr,
           (void *)end_addr);
+
+  u32 poison_magic = kAsanUserPoisonedMemoryMagic;
+
+  GET_CALLER_PC_BP;
+  GET_STORE_STACK_TRACE_PC_BP(pc, bp);
+  // TODO: garbage collect stacks once they fall off the ring buffer?
+  // StackDepot doesn't currently have a way to delete stacks.
+  u32 stack_id = StackDepotPut(stack);
+
+  if (flags()->track_poison > 0) {
+    u32 current_tid = GetCurrentTidOrInvalid();
+    u32 poison_index = ((stack_id * 151157) ^ (current_tid * 733123)) %
+                       NumPoisonTrackingMagicValues;
+    poison_magic = PoisonTrackingIndexToMagic[poison_index];
+    PoisonRecord record{.stack_id = stack_id,
+                        .thread_id = current_tid,
+                        .begin = beg_addr,
+                        .end = end_addr};
+    // This is racy: with concurrent writes, some records may be lost,
+    // but it's a sacrifice I am willing to make for speed.
+    // The sharding across PoisonRecords reduces the likelihood of
+    // concurrent writes.
+    PoisonRecords[poison_index]->push(record);
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thurstond wrote:

Changed to use a mutex

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