[AArch64][FMV] Enable PAuth and BTI hardening of resolver functions

[atrosinenko]

No description provided.

[llvmbot]

@llvm/pr-subscribers-clang-codegen

@llvm/pr-subscribers-clang

Author: Anatoly Trosinenko (atrosinenko)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/141573.diff

2 Files Affected:

• (modified) clang/lib/CodeGen/CodeGenModule.cpp (+9)
• (added) clang/test/CodeGen/ptrauth-resolver-attributes.c (+25)

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 16e010adbeb5f..af8d4cc60de57 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4638,6 +4638,13 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
   if (FD->isTargetMultiVersion() || FD->isTargetClonesMultiVersion())
     AddDeferredMultiVersionResolverToEmit(GD);
 
+  auto SetResolverAttrs = [&](llvm::Function &Resolver) {
+    TargetInfo::BranchProtectionInfo BPI(getLangOpts());
+    TargetCodeGenInfo::setBranchProtectionFnAttributes(BPI, Resolver);
+    TargetCodeGenInfo::setPointerAuthFnAttributes(CodeGenOpts.PointerAuth,
+                                                  Resolver);
+  };
+
   // For cpu_specific, don't create an ifunc yet because we don't know if the
   // cpu_dispatch will be emitted in this translation unit.
   if (ShouldReturnIFunc) {
@@ -4652,6 +4659,7 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
                                   "", Resolver, &getModule());
     GIF->setName(ResolverName);
     SetCommonAttributes(FD, GIF);
+    SetResolverAttrs(cast<llvm::Function>(*Resolver));
     if (ResolverGV)
       replaceDeclarationWith(ResolverGV, GIF);
     return GIF;
@@ -4662,6 +4670,7 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
   assert(isa<llvm::GlobalValue>(Resolver) && !ResolverGV &&
          "Resolver should be created for the first time");
   SetCommonAttributes(FD, cast<llvm::GlobalValue>(Resolver));
+  SetResolverAttrs(cast<llvm::Function>(*Resolver));
   return Resolver;
 }
 
diff --git a/clang/test/CodeGen/ptrauth-resolver-attributes.c b/clang/test/CodeGen/ptrauth-resolver-attributes.c
new file mode 100644
index 0000000000000..8bdedd2c549be
--- /dev/null
+++ b/clang/test/CodeGen/ptrauth-resolver-attributes.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -mbranch-target-enforce -msign-return-address=all      -emit-llvm %s -o - | FileCheck --check-prefixes=CHECK,BTI-SIGNRA %s
+// RUN: %clang_cc1 -triple arm64-apple-ios   -mbranch-target-enforce -msign-return-address=all      -emit-llvm %s -o - | FileCheck --check-prefixes=CHECK,BTI-SIGNRA %s
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-returns -fptrauth-auth-traps -emit-llvm %s -o - | FileCheck --check-prefixes=CHECK,PAUTHTEST %s
+// RUN: %clang_cc1 -triple arm64-apple-ios   -fptrauth-calls -fptrauth-returns -fptrauth-auth-traps -emit-llvm %s -o - | FileCheck --check-prefixes=CHECK,PAUTHTEST %s
+
+// Check that resolver functions generated by clang have the correct attributes.
+
+int __attribute__((target_clones("crc", "default"))) ftc(void) { return 0; }
+
+int __attribute__((target_version("crc")))     fmv(void) { return 0; }
+int __attribute__((target_version("default"))) fmv(void) { return 0; }
+
+// CHECK: define{{.*}} i32 @ftc._Mcrc() #0
+// CHECK: define{{.*}} ptr @ftc.resolver() #1
+// CHECK: define{{.*}} i32 @fmv._Mcrc() #0
+// CHECK: define{{.*}} i32 @fmv.default() #2
+// CHECK: define{{.*}} i32 @ftc.default() #2
+// CHECK: define{{.*}} ptr @fmv.resolver() #1
+
+// BTI-SIGNRA: attributes #0 = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
+// BTI-SIGNRA: attributes #1 = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
+// BTI-SIGNRA: attributes #2 = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
+// PAUTHTEST: attributes #0 = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }
+// PAUTHTEST: attributes #1 = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }
+// PAUTHTEST: attributes #2 = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }

[efriedma-quic]

Maybe setNonAliasAttributes? Or setTargetAttributes?

[atrosinenko]

Reused setTargetAttributes, thank you! If I understand it correctly, it should be safer not to pass any Decl to setTargetAttributes, as otherwise the implementation might inspect target-specific function attributes and use them for the resolver (which can correspond to one or multiple declarations), and we want to only set the bare minimum attributes instead.

[efriedma-quic]

That's fine.

[labrinea]

Seems somewhat related to #84704. @jroelofs mind taking a look?

[efriedma-quic]

Is Resolver actually guaranteed to be a function? GetOrCreateLLVMFunction can return other kinds of GlobalValues in some cases.

Should we be calling SetCommonAttributes/setGVProperties to set the linkage/visibility of the resolver?

[jroelofs]

GlobalIFunc instructions in the IR currently require that the resolver be a Function with a definition.

[labrinea]

Can we move this file under the AArch64 directory?

[ojhunt]

none of the other ptrauth tests are in a subdirectory, are you wanting all the ptrauth tests to be moved?

[labrinea]

No, I am not asking existing tests to be moved, but when we add new ones they ought to be in the right place. An attempt to move existing CodeGen tests under the AArch64 folder was here #115818