diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -417,6 +417,14 @@
   0x01000000000,   // OriginBase
 };
 
+// aarch64 FreeBSD
+static const MemoryMapParams FreeBSD_AArch64_MemoryMapParams = {
+  0x1800000000000,  // AndMask
+  0x0400000000000,  // XorMask
+  0x0200000000000,  // ShadowBase
+  0x0700000000000,  // OriginBase
+};
+
 // i386 FreeBSD
 static const MemoryMapParams FreeBSD_I386_MemoryMapParams = {
   0x000180000000,  // AndMask
@@ -466,6 +474,11 @@
   &Linux_AArch64_MemoryMapParams,
 };
 
+static const PlatformMemoryMapParams FreeBSD_ARM_MemoryMapParams = {
+  nullptr,
+  &FreeBSD_AArch64_MemoryMapParams,
+};
+
 static const PlatformMemoryMapParams FreeBSD_X86_MemoryMapParams = {
   &FreeBSD_I386_MemoryMapParams,
   &FreeBSD_X86_64_MemoryMapParams,
@@ -894,6 +907,9 @@
     switch (TargetTriple.getOS()) {
       case Triple::FreeBSD:
         switch (TargetTriple.getArch()) {
+          case Triple::aarch64:
+            MapParams = FreeBSD_ARM_MemoryMapParams.bits64;
+            break;
           case Triple::x86_64:
             MapParams = FreeBSD_X86_MemoryMapParams.bits64;
             break;