diff --git a/compiler-rt/lib/msan/msan.cc b/compiler-rt/lib/msan/msan.cc
index e0d1b6cef8cf..e0bff8203120 100644
--- a/compiler-rt/lib/msan/msan.cc
+++ b/compiler-rt/lib/msan/msan.cc
@@ -240,8 +240,10 @@ void __msan_init() {
   if (!InitShadow(/* prot1 */false, /* prot2 */true, /* map_shadow */true,
                   __msan_track_origins)) {
     // FIXME: prot1 = false is only required when running under DR.
-    Printf("FATAL: MemorySanitizer can not mmap the shadow memory\n");
+    Printf("FATAL: MemorySanitizer can not mmap the shadow memory.\n");
     Printf("FATAL: Make sure to compile with -fPIE and to link with -pie.\n");
+    Printf("FATAL: Disabling ASLR is known to cause this error.\n");
+    Printf("FATAL: If running under GDB, try 'set disable-randomization off'.\n");
     DumpProcessMap();
     Die();
   }
diff --git a/compiler-rt/lib/msan/msan_linux.cc b/compiler-rt/lib/msan/msan_linux.cc
index aea29453c321..b51f63633108 100644
--- a/compiler-rt/lib/msan/msan_linux.cc
+++ b/compiler-rt/lib/msan/msan_linux.cc
@@ -51,6 +51,12 @@ bool InitShadow(bool prot1, bool prot2, bool map_shadow, bool init_origins) {
     Printf("Bad1     : %p %p\n", kBad1Beg, kBad1End);
   }
 
+  if (!MemoryRangeIsAvailable(kShadowBeg,
+                              init_origins ? kOriginsEnd : kShadowEnd)) {
+    Printf("FATAL: Shadow memory range is not available.\n");
+    return false;
+  }
+
   if (prot1 && !Mprotect(kBad1Beg, kBad1End - kBad1Beg))
     return false;
   if (prot2 && !Mprotect(kBad2Beg, kBad2End - kBad2Beg))