scudo: Move getChunkFromBlock() allocated check into caller. NFCI.

With tag-on-free we will need to get the chunk of a deallocated block. Change
getChunkFromBlock() so that it doesn't check that the chunk is allocated,
and move the check into the caller, so that it can be reused for this purpose.

Differential Revision: https://reviews.llvm.org/D71291

1 files changed, 9 insertions, 17 deletions

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index b355a4746fa..02c998e666d 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -418,10 +418,11 @@ public:
     auto Lambda = [this, From, To, Callback, Arg](uptr Block) {
       if (Block < From || Block >= To)
         return;
-      uptr ChunkSize;
-      const uptr ChunkBase = getChunkFromBlock(Block, &ChunkSize);
-      if (ChunkBase != InvalidChunk)
-        Callback(ChunkBase, ChunkSize, Arg);
+      uptr Chunk;
+      Chunk::UnpackedHeader Header;
+      if (getChunkFromBlock(Block, &Chunk, &Header) &&
+          Header.State == Chunk::State::Allocated)
+        Callback(Chunk, getSize(reinterpret_cast<void *>(Chunk), &Header), Arg);
     };
     Primary.iterateOverBlocks(Lambda);
     Secondary.iterateOverBlocks(Lambda);
@@ -483,9 +484,7 @@ private:
   static_assert(MinAlignment >= sizeof(Chunk::PackedHeader),
                 "Minimal alignment must at least cover a chunk header.");
 
-  // Constants used by the chunk iteration mechanism.
   static const u32 BlockMarker = 0x44554353U;
-  static const uptr InvalidChunk = ~static_cast<uptr>(0);
 
   GlobalStats Stats;
   TSDRegistryT TSDRegistry;
@@ -593,20 +592,13 @@ private:
     }
   }
 
-  // This only cares about valid busy chunks. This might change in the future.
-  uptr getChunkFromBlock(uptr Block, uptr *Size) {
+  bool getChunkFromBlock(uptr Block, uptr *Chunk,
+                         Chunk::UnpackedHeader *Header) {
     u32 Offset = 0;
     if (reinterpret_cast<u32 *>(Block)[0] == BlockMarker)
       Offset = reinterpret_cast<u32 *>(Block)[1];
-    const uptr P = Block + Offset + Chunk::getHeaderSize();
-    const void *Ptr = reinterpret_cast<const void *>(P);
-    Chunk::UnpackedHeader Header;
-    if (!Chunk::isValid(Cookie, Ptr, &Header) ||
-        Header.State != Chunk::State::Allocated)
-      return InvalidChunk;
-    if (Size)
-      *Size = getSize(Ptr, &Header);
-    return P;
+    *Chunk = Block + Offset + Chunk::getHeaderSize();
+    return Chunk::isValid(Cookie, reinterpret_cast<void *>(*Chunk), Header);
   }
 
   uptr getStats(ScopedString *Str) {