Index: compiler-rt/test/asan/TestCases/Helpers/underflow.cc
===================================================================
--- /dev/null
+++ compiler-rt/test/asan/TestCases/Helpers/underflow.cc
@@ -0,0 +1 @@
+int YYY[3]={1,2,3};
Index: compiler-rt/test/asan/TestCases/global-underflow.cc
===================================================================
--- /dev/null
+++ compiler-rt/test/asan/TestCases/global-underflow.cc
@@ -0,0 +1,17 @@
+// RUN: %clangxx_asan -O0 -mllvm -asan-meta-separate-section %s %p/Helpers/underflow.cc -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O1 -mllvm -asan-meta-separate-section %s %p/Helpers/underflow.cc -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O2 -mllvm -asan-meta-separate-section %s %p/Helpers/underflow.cc -o %t && not %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_asan -O3 -mllvm -asan-meta-separate-section %s %p/Helpers/underflow.cc -o %t && not %run %t 2>&1 | FileCheck %s
+
+int XXX[2] = {2, 3};
+extern int YYY[];
+#include <string.h>
+int main(int argc, char **argv) {
+  memset(XXX, 0, 2*sizeof(int));
+  // CHECK: {{READ of size 4 at 0x.* thread T0}}
+  // CHECK: {{    #0 0x.* in main .*global-underflow.cc:}}[[@LINE+3]]
+  // CHECK: {{0x.* is located 4 bytes to the left of global variable}}
+  // CHECK:   {{.*YYY.* of size 12}}
+  int res = YYY[-1];
+  return res;
+}
Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -176,6 +176,11 @@
     "asan-force-dynamic-shadow",
     cl::desc("Load shadow address into a local variable for each function"),
     cl::Hidden, cl::init(false));
+static cl::opt<bool> ClMetaInSeparateSection(
+    "asan-meta-separate-section",
+    cl::desc("Place ASan global metadata into a separate section"),
+    cl::Hidden, cl::init(false));
+
 
 // This flag limits the number of instructions to be instrumented
 // in any given BB. Normally, this should be set to unlimited (INT_MAX),
@@ -1876,6 +1881,13 @@
       M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
       ConstantArray::get(ArrayOfGlobalStructTy, MetadataInitializers), "");
 
+  // Place ASan metadata into a separate section similarly to how it's done
+  // for -fdata-sections (see InstrumentGlobalsELF() or InstrumentGlobalsMachO())
+  // to avoid stepping into it on global underflow in first symbols of data
+  // sections.
+  if (ClMetaInSeparateSection)
+    AllGlobals->setSection(getGlobalMetadataSection());
+
   IRB.CreateCall(AsanRegisterGlobals,
                  {IRB.CreatePointerCast(AllGlobals, IntptrTy),
                   ConstantInt::get(IntptrTy, N)});