1 files changed, 14 insertions, 1 deletions
diff --git a/libc/bionic/mmap.cpp b/libc/bionic/mmap.cpp
index 75bea588f..651bfd0e5 100644
--- a/libc/bionic/mmap.cpp
+++ b/libc/bionic/mmap.cpp
@@ -55,5 +55,18 @@ void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offse
 }
 
 void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) {
-  return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset));
+  if (offset & ((1UL << MMAP2_SHIFT)-1)) {
+    errno = EINVAL;
+    return MAP_FAILED;
+  }
+
+  size_t unsigned_offset = static_cast<size_t>(offset); // To avoid sign extension.
+  void* result = __mmap2(addr, size, prot, flags, fd, unsigned_offset >> MMAP2_SHIFT);
+
+  if (result != MAP_FAILED && (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) != 0) {
+    ErrnoRestorer errno_restorer;
+    madvise(result, size, MADV_MERGEABLE);
+  }
+
+  return result;
 }