1 files changed, 12 insertions, 0 deletions
diff --git a/libc/stdlib/malloc-standard/malloc.h b/libc/stdlib/malloc-standard/malloc.h
index 44120d388..30a696e5a 100644
--- a/libc/stdlib/malloc-standard/malloc.h
+++ b/libc/stdlib/malloc-standard/malloc.h
@@ -839,6 +839,18 @@ typedef struct malloc_chunk* mfastbinptr;
 #define get_max_fast(M) \
   ((M)->max_fast & ~(FASTCHUNKS_BIT | ANYCHUNKS_BIT))
 
+/*
+  Safe-Linking:
+  Use randomness from ASLR (mmap_base) to protect single-linked lists
+  of fastbins. Together with allocation alignment checks, this mechanism
+  reduces the risk of pointer hijacking, as was done with Safe-Unlinking
+  in the double-linked lists of smallbins.
+*/
+#define PROTECT_PTR(pos, ptr)     ((mchunkptr)((((size_t)pos) >> PAGE_SHIFT) ^ ((size_t)ptr)))
+#define REVEAL_PTR(pos, ptr)      PROTECT_PTR(pos, ptr)
+#define CHECK_PTR(P)    \
+  if (!aligned_OK(P))   \
+      abort();
 
 /*
   morecore_properties is a status word holding dynamically discovered