diff --git a/pkgs/development/compilers/llvm/4/llvm.nix b/pkgs/development/compilers/llvm/4/llvm.nix
index 1fe79d9300a..33147b07599 100644
--- a/pkgs/development/compilers/llvm/4/llvm.nix
+++ b/pkgs/development/compilers/llvm/4/llvm.nix
@@ -24,11 +24,6 @@
 let
   src = fetch "llvm" "0l9bf7kdwhlj0kq1hawpyxhna1062z3h7qcz2y8nfl9dz2qksy6s";
 
-  aarch64Patch = fetchpatch {
-    url = https://reviews.llvm.org/file/data/2oqw5rhhklsapbjrhlpd/PHID-FILE-lvo4fcs6hjvkxb5wneg2/D40423.diff;
-    sha256 = "0b0h7n7lxw33pn2j061hm9050zn263gmiig937g5cmcvjimxlybb";
-  };
-
   # Used when creating a version-suffixed symlink of libLLVM.dylib
   shortVersion = with stdenv.lib;
     concatStringsSep "." (take 2 (splitString "." release_version));
@@ -87,7 +82,7 @@ in stdenv.mkDerivation rec {
         --replace 'struct sigaltstack' 'stack_t'
     )
   '' + stdenv.lib.optionalString stdenv.isAarch64 ''
-    patch -p0 < ${aarch64Patch}
+    patch -p0 < ${../aarch64.patch}
   '';
 
   # hacky fix: created binaries need to be run before installation
diff --git a/pkgs/development/compilers/llvm/5/llvm.nix b/pkgs/development/compilers/llvm/5/llvm.nix
index 20b0f4b20c6..8358b6b18c3 100644
--- a/pkgs/development/compilers/llvm/5/llvm.nix
+++ b/pkgs/development/compilers/llvm/5/llvm.nix
@@ -24,11 +24,6 @@
 let
   src = fetch "llvm" "1nin64vz21hyng6jr19knxipvggaqlkl2l9jpd5czbc4c2pcnpg3";
 
-  aarch64Patch = fetchpatch {
-    url = https://reviews.llvm.org/file/data/2oqw5rhhklsapbjrhlpd/PHID-FILE-lvo4fcs6hjvkxb5wneg2/D40423.diff;
-    sha256 = "0b0h7n7lxw33pn2j061hm9050zn263gmiig937g5cmcvjimxlybb";
-  };
-
   # Used when creating a version-suffixed symlink of libLLVM.dylib
   shortVersion = with stdenv.lib;
     concatStringsSep "." (take 2 (splitString "." release_version));
@@ -81,7 +76,7 @@ in stdenv.mkDerivation rec {
     # Revert compiler-rt commit that makes codesign mandatory
     patch -p1 -i ${./compiler-rt-codesign.patch} -d projects/compiler-rt
   '' + stdenv.lib.optionalString stdenv.isAarch64 ''
-    patch -p0 < ${aarch64Patch}
+    patch -p0 < ${../aarch64.patch}
   '';
 
   # hacky fix: created binaries need to be run before installation
diff --git a/pkgs/development/compilers/llvm/aarch64.patch b/pkgs/development/compilers/llvm/aarch64.patch
new file mode 100644
index 00000000000..205074e48e4
--- /dev/null
+++ b/pkgs/development/compilers/llvm/aarch64.patch
@@ -0,0 +1,51 @@
+--- lib/Support/Unix/Memory.inc
++++ lib/Support/Unix/Memory.inc
+@@ -126,8 +126,12 @@
+   Result.Address = Addr;
+   Result.Size = NumPages*PageSize;
+ 
+-  if (PFlags & MF_EXEC)
+-    Memory::InvalidateInstructionCache(Result.Address, Result.Size);
++  // Rely on protectMappedMemory to invalidate instruction cache.
++  if (PFlags & MF_EXEC) {
++    EC = Memory::protectMappedMemory (Result, PFlags);
++    if (EC != std::error_code())
++      return MemoryBlock();
++  }
+ 
+   return Result;
+ }
+@@ -156,15 +160,31 @@
+     return std::error_code(EINVAL, std::generic_category());
+ 
+   int Protect = getPosixProtectionFlags(Flags);
+-
+   uintptr_t Start = alignAddr((uint8_t *)M.Address - PageSize + 1, PageSize);
+   uintptr_t End = alignAddr((uint8_t *)M.Address + M.Size, PageSize);
++
++  bool InvalidateCache = (Flags & MF_EXEC);
++
++#if defined(__arm__) || defined(__aarch64__)
++  // Certain ARM implementations treat icache clear instruction as a memory read,
++  // and CPU segfaults on trying to clear cache on !PROT_READ page.  Therefore we need
++  // to temporarily add PROT_READ for the sake of flushing the instruction caches.
++  if (InvalidateCache && !(Protect & PROT_READ)) {
++    int Result = ::mprotect((void *)Start, End - Start, Protect | PROT_READ);
++    if (Result != 0)
++      return std::error_code(errno, std::generic_category());
++
++    Memory::InvalidateInstructionCache(M.Address, M.Size);
++    InvalidateCache = false;
++  }
++#endif
++
+   int Result = ::mprotect((void *)Start, End - Start, Protect);
+ 
+   if (Result != 0)
+     return std::error_code(errno, std::generic_category());
+ 
+-  if (Flags & MF_EXEC)
++  if (InvalidateCache)
+     Memory::InvalidateInstructionCache(M.Address, M.Size);
+ 
+   return std::error_code();