[PATCH] D19909: [Attr] Add support for the `ms_hook_prologue` attribute.

[Charles Davis via cfe-commits]

cdavis5x created this revision.
cdavis5x added reviewers: aaron.ballman, rnk.
cdavis5x added a subscriber: cfe-commits.
cdavis5x added a dependency: D19908: [X86] Support the "ms-hotpatch" attribute..

Based on a patch by Michael Mueller.

This attribute specifies that a function can be hooked or patched. This
mechanism was originally devised by Microsoft for hotpatching their
binaries (which they're constantly updating to stay ahead of crackers,
script kiddies, and other ne'er-do-wells on the Internet), but it's now
commonly abused by Windows programs that want to hook API functions. It
is for this reason that this attribute was added to GCC--hence the name,
`ms_hook_prologue`.

Depends on D19908.

http://reviews.llvm.org/D19909

Files:
  include/clang/Basic/Attr.td
  lib/CodeGen/TargetInfo.cpp
  lib/Sema/SemaDeclAttr.cpp
  test/CodeGen/function-attributes.c

Index: test/CodeGen/function-attributes.c
===================================================================
--- test/CodeGen/function-attributes.c
+++ test/CodeGen/function-attributes.c
@@ -108,11 +108,18 @@
   _setjmp(0);
 }
 
+// CHECK-LABEL: define void @f21
+// CHECK: [[HOTPATCH:#[0-9]+]]
+// CHECK: {
+void __attribute__((ms_hook_prologue)) f21(void) {
+}
+
 // CHECK: attributes [[NUW]] = { nounwind optsize{{.*}} }
 // CHECK: attributes [[AI]] = { alwaysinline nounwind optsize{{.*}} }
 // CHECK: attributes [[NUW_OS_RN]] = { nounwind optsize readnone{{.*}} }
 // CHECK: attributes [[ALIGN]] = { nounwind optsize alignstack=16{{.*}} }
 // CHECK: attributes [[RT]] = { nounwind optsize returns_twice{{.*}} }
+// CHECK: attributes [[HOTPATCH]] = { nounwind optsize{{.*}}"ms-hotpatch"{{.*}} }
 // CHECK: attributes [[NR]] = { noreturn optsize }
 // CHECK: attributes [[NUW_RN]] = { nounwind optsize readnone }
 // CHECK: attributes [[RT_CALL]] = { optsize returns_twice }
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp
+++ lib/Sema/SemaDeclAttr.cpp
@@ -5742,6 +5742,9 @@
     break;
 
   // Microsoft attributes:
+  case AttributeList::AT_MSHookPrologue:
+    handleSimpleAttribute<MSHookPrologueAttr>(S, D, Attr);
+    break;
   case AttributeList::AT_MSNoVTable:
     handleSimpleAttribute<MSNoVTableAttr>(S, D, Attr);
     break;
Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -1743,6 +1743,10 @@
       llvm::Function *Fn = cast<llvm::Function>(GV);
       Fn->setCallingConv(llvm::CallingConv::X86_INTR);
     }
+    if (FD->hasAttr<MSHookPrologueAttr>()) {
+      llvm::Function *Fn = cast<llvm::Function>(GV);
+      Fn->addFnAttr("ms-hotpatch");
+    }
   }
 }
 
@@ -2073,6 +2077,10 @@
         llvm::Function *Fn = cast<llvm::Function>(GV);
         Fn->setCallingConv(llvm::CallingConv::X86_INTR);
       }
+      if (FD->hasAttr<MSHookPrologueAttr>()) {
+        llvm::Function *Fn = cast<llvm::Function>(GV);
+        Fn->addFnAttr("ms-hotpatch");
+      }
     }
   }
 };
Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -2029,6 +2029,12 @@
 
 // Microsoft-related attributes
 
+def MSHookPrologue : InheritableAttr {
+  let Spellings = [GCC<"ms_hook_prologue">];
+  let Subjects = SubjectList<[Function]>;
+  let Documentation = [Undocumented];
+}
+
 def MSNoVTable : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
   let Spellings = [Declspec<"novtable">];
   let Subjects = SubjectList<[CXXRecord]>;


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