Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1307,6 +1307,12 @@
   let Documentation = [Undocumented];
 }
 
+def MIGServerRoutine : InheritableAttr {
+  let Spellings = [Clang<"mig_server_routine">];
+  let Subjects = SubjectList<[Function, ObjCMethod, Block]>;
+  let Documentation = [MIGConventionDocs];
+}
+
 def MSABI : DeclOrTypeAttr {
   let Spellings = [GCC<"ms_abi">];
 //  let Subjects = [Function, ObjCMethod];
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4028,3 +4028,24 @@
 
 When compiled without ``-fobjc-arc``, this attribute is ignored.
 }]; }
+
+def MIGConventionDocs : Documentation {
+  let Category = DocCatType;
+  let Content = [{
+  The Mach Interface Generator release-on-success convention dictates
+functions that follow it to only release arguments passed to them when they
+return "success" (a ``kern_return_t`` error code that indicates that
+no errors have occured). Otherwise the release is performed by the MIG client
+that called the function. The annotation ``__attribute__((mig_server_routine))``
+is applied in order to specify which functions are expected to follow the
+convention. This allows the Static Analyzer to find bugs caused by violations of
+that convention. The attribute would normally appear on the forward declaration
+of the actual server routine in the MIG server header, but it may also be
+added to arbitrary functions that need to follow the same convention - for
+example, a user can add them to auxiliary functions called by the server routine
+that have their return value of type ``kern_return_t`` unconditionally returned
+from the routine. The attribute can be applied to C++ methods, and in this case
+it will be automatically applied to overrides if the method is virtual. The
+attribute can be written using C++11 syntax: ``[[mig::server_routine]]``.
+}];
+}
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -8696,6 +8696,11 @@
 def ext_opencl_ext_vector_type_rgba_selector: ExtWarn<
   "vector component name '%0' is an OpenCL version 2.2 feature">,
   InGroup<OpenCLUnsupportedRGBA>;
+
+// MIG routine annotations.
+def warn_mig_server_routine_does_not_return_kern_return_t : Warning<
+  "'mig_server_routine' attribute only applies to routines that return a kern_return_t">,
+  InGroup<IgnoredAttributes>;
 } // end of sema category
 
 let CategoryName = "OpenMP Issue" in {
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Analysis/AnyCall.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTMutationListener.h"
@@ -6396,6 +6397,29 @@
   handleSimpleAttribute<ObjCExternallyRetainedAttr>(S, D, AL);
 }
 
+static void handleMIGServerRoutineAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  // Check that the return type is a `typedef int kern_return_t` or a typedef
+  // around it, because otherwise MIG convention checks make no sense.
+  // BlockDecl doesn't store a return type, so it's annoying to check,
+  // so let's skip it for now.
+  if (!isa<BlockDecl>(D)) {
+    ASTContext &ACtx = S.getASTContext();
+    QualType T = AnyCall::forDecl(D)->getReturnType(ACtx);
+    bool IsKernReturnT = false;
+    while (const auto *TT = T->getAs<TypedefType>()) {
+      IsKernReturnT = (TT->getDecl()->getName() == "kern_return_t");
+      T = TT->desugar();
+    }
+    if (!IsKernReturnT || T.getCanonicalType() != ACtx.IntTy) {
+      S.Diag(D->getBeginLoc(),
+             diag::warn_mig_server_routine_does_not_return_kern_return_t);
+      return;
+    }
+  }
+
+  handleSimpleAttribute<MIGServerRoutineAttr>(S, D, AL);
+}
+
 //===----------------------------------------------------------------------===//
 // Top Level Sema Entry Points
 //===----------------------------------------------------------------------===//
@@ -7119,6 +7143,10 @@
   case ParsedAttr::AT_ObjCExternallyRetained:
     handleObjCExternallyRetainedAttr(S, D, AL);
     break;
+
+  case ParsedAttr::AT_MIGServerRoutine:
+    handleMIGServerRoutineAttr(S, D, AL);
+    break;
   }
 }
 
Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===================================================================
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -60,6 +60,7 @@
 // CHECK-NEXT: InternalLinkage (SubjectMatchRule_variable, SubjectMatchRule_function, SubjectMatchRule_record)
 // CHECK-NEXT: LTOVisibilityPublic (SubjectMatchRule_record)
 // CHECK-NEXT: Lockable (SubjectMatchRule_record)
+// CHECK-NEXT: MIGServerRoutine (SubjectMatchRule_function)
 // CHECK-NEXT: MSStruct (SubjectMatchRule_record)
 // CHECK-NEXT: MicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: MinSize (SubjectMatchRule_function, SubjectMatchRule_objc_method)
Index: clang/test/Sema/attr-mig.c
===================================================================
--- /dev/null
+++ clang/test/Sema/attr-mig.c
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+typedef int kern_return_t;
+#define KERN_SUCCESS 0
+
+__attribute__((mig_server_routine)) kern_return_t var = KERN_SUCCESS; // expected-warning-re{{'mig_server_routine' attribute only applies to functions, Objective-C methods, and blocks{{$}}}}
+
+__attribute__((mig_server_routine)) void foo_void(); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+__attribute__((mig_server_routine)) int foo_int(); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+
+__attribute__((mig_server_routine)) kern_return_t bar_extern(); // no-warning
+__attribute__((mig_server_routine)) kern_return_t bar_forward(); // no-warning
+
+__attribute__((mig_server_routine)) kern_return_t bar_definition() { // no-warning
+  return KERN_SUCCESS;
+}
+
+kern_return_t bar_forward() { // no-warning
+  return KERN_SUCCESS;
+}
+
+__attribute__((mig_server_routine(123))) kern_return_t bar_with_argument(); // expected-error{{'mig_server_routine' attribute takes no arguments}}
Index: clang/test/Sema/attr-mig.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/attr-mig.cpp
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+typedef int kern_return_t;
+typedef kern_return_t IOReturn;
+#define KERN_SUCCESS 0
+#define kIOReturnSuccess KERN_SUCCESS
+
+class MyServer {
+public:
+  virtual __attribute__((mig_server_routine)) IOReturn externalMethod();
+  virtual __attribute__((mig_server_routine)) void anotherMethod(); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+  virtual __attribute__((mig_server_routine)) int yetAnotherMethod(); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+  [[clang::mig_server_routine]] virtual IOReturn cppAnnotatedMethod();
+  [[clang::mig_server_routine("arg")]] virtual IOReturn cppAnnotatedMethodWithInvalidArgs(); // expected-error{{'mig_server_routine' attribute takes no arguments}}
+  [[clang::mig_server_routine]] virtual int cppInvalidAnnotatedMethod(); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+};
+
+IOReturn MyServer::externalMethod() {
+  return kIOReturnSuccess;
+}
Index: clang/test/Sema/attr-mig.m
===================================================================
--- /dev/null
+++ clang/test/Sema/attr-mig.m
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -fsyntax-only -fblocks -verify %s
+
+typedef int kern_return_t;
+#define KERN_SUCCESS 0
+
+@interface NSObject
+@end
+
+@interface I: NSObject
+- (kern_return_t)foo __attribute__((mig_server_routine)); // no-warning
+- (void) bar_void __attribute__((mig_server_routine)); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+- (int) bar_int __attribute__((mig_server_routine)); // expected-warning{{'mig_server_routine' attribute only applies to routines that return a kern_return_t}}
+@end
+
+@implementation I
+- (kern_return_t)foo {
+  kern_return_t (^block)() = ^ __attribute__((mig_server_routine)) { // no-warning
+    return KERN_SUCCESS;
+  };
+
+  // TODO: Warn that this block doesn't return a kern_return_t.
+  void (^invalid_block)() = ^ __attribute__((mig_server_routine)) {};
+
+  return block();
+}
+- (void)bar_void {
+}
+- (int)bar_int {
+  return 0;
+}
+@end