[compiler-rt] DO_NOT_MERGE (PR #66682)

[Vitaly Buka via llvm-commits]

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@@ -427,74 +429,128 @@ class BaseReport {
     bool from_small_heap = false;
     bool is_allocated = false;
   } heap;
+
+  struct {
+    uptr untagged_addr = 0;
+    bool after = false;
+    bool is_close = false;
+
+    struct {
+      uptr begin = 0;
+      uptr end = 0;
+      u32 thread_id = 0;
+      u32 stack_id = 0;
+      bool is_allocated = false;
+    } heap;
+  } candidate;
 };
 
-void BaseReport::PrintHeapOrGlobalCandidate(tag_t *candidate, tag_t *left,
-                                            tag_t *right) const {
+void BaseReport::FindBufferOverflowCandidate() {
+  // Check if this looks like a heap buffer overflow by scanning
+  // the shadow left and right and looking for the first adjacent
+  // object with a different memory tag. If that tag matches ptr_tag,
+  // check the allocator if it has a live chunk there.
+  tag_t *tag_ptr = reinterpret_cast<tag_t *>(MemToShadow(untagged_addr));
+  tag_t *candidate_tag_ptr = nullptr, *left = tag_ptr, *right = tag_ptr;
+  uptr candidate_distance = 0;
+  for (; candidate_distance < 1000; candidate_distance++) {
+    if (MemIsShadow(reinterpret_cast<uptr>(left)) && TagsEqual(ptr_tag, left)) {
+      candidate_tag_ptr = left;
+      break;
+    }
+    --left;
+    if (MemIsShadow(reinterpret_cast<uptr>(right)) &&
+        TagsEqual(ptr_tag, right)) {
+      candidate_tag_ptr = right;
+      break;
+    }
+    ++right;
+  }
+
+  constexpr auto kCloseCandidateDistance = 1;
+  candidate.is_close = candidate_distance <= kCloseCandidateDistance;
+
+  {
+    candidate.after = candidate_tag_ptr == left;
+    candidate.untagged_addr =
+        ShadowToMem(reinterpret_cast<uptr>(candidate_tag_ptr));
+    HwasanChunkView chunk = FindHeapChunkByAddress(candidate.untagged_addr);
+    if (chunk.IsAllocated()) {
+      candidate.heap.is_allocated = chunk.IsAllocated();
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vitalybuka wrote:

done

https://github.com/llvm/llvm-project/pull/66682