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[AArch64][FMV] Enable PAuth and BTI hardening of resolver functions #141573

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[AArch64][FMV] Enable PAuth and BTI hardening of resolver functions #141573

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3e62515
[AArch64][FMV] Enable PAuth and BTI hardening of resolver functions
atrosinenko May 26, 2025
6d63e7e
Use setTargetAttributes function
atrosinenko Jun 4, 2025
2d74565
test: accept functions and attribute groups in any order
atrosinenko Jun 4, 2025
23a5407
Move new test file to AArch64/ subdirectory
atrosinenko Jul 14, 2025
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9 changes: 9 additions & 0 deletions clang/lib/CodeGen/CodeGenModule.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4757,6 +4757,13 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
if (FD->isTargetMultiVersion() || FD->isTargetClonesMultiVersion())
AddDeferredMultiVersionResolverToEmit(GD);

auto SetResolverAttrs = [&](llvm::Function *Resolver) {
// Set the default target-specific attributes, such as PAC and BTI ones on
// AArch64. Not passing Decl to prevent setting unrelated attributes,
// as Resolver can be shared by multiple declarations.
getTargetCodeGenInfo().setTargetAttributes(/*D=*/nullptr, Resolver, *this);
};

// 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) {
Expand All @@ -4771,6 +4778,7 @@ llvm::Constant *CodeGenModule::GetOrCreateMultiVersionResolver(GlobalDecl GD) {
"", Resolver, &getModule());
GIF->setName(ResolverName);
SetCommonAttributes(FD, GIF);
SetResolverAttrs(cast<llvm::Function>(Resolver));
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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?

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

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I think the question "Should we be calling SetCommonAttributes/setGVProperties to set the linkage/visibility of the resolver?" was never answered.

if (ResolverGV)
replaceDeclarationWith(ResolverGV, GIF);
return GIF;
Expand All @@ -4781,6 +4789,7 @@ 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;
}

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25 changes: 25 additions & 0 deletions clang/test/CodeGen/AArch64/ptrauth-resolver-attributes.c
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@@ -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-DAG: define{{.*}} i32 @ftc._Mcrc() #[[ATTR_CRC:[0-9]+]]
// CHECK-DAG: define{{.*}} i32 @ftc.default() #[[ATTR_DEFAULT:[0-9]+]]
// CHECK-DAG: define{{.*}} ptr @ftc.resolver() #[[ATTR_RESOLVER:[0-9]+]]
// CHECK-DAG: define{{.*}} i32 @fmv._Mcrc() #[[ATTR_CRC]]
// CHECK-DAG: define{{.*}} i32 @fmv.default() #[[ATTR_DEFAULT]]
// CHECK-DAG: define{{.*}} ptr @fmv.resolver() #[[ATTR_RESOLVER]]

// BTI-SIGNRA-DAG: attributes #[[ATTR_CRC]] = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
// BTI-SIGNRA-DAG: attributes #[[ATTR_RESOLVER]] = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
// BTI-SIGNRA-DAG: attributes #[[ATTR_DEFAULT]] = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"{{.*}} }
// PAUTHTEST-DAG: attributes #[[ATTR_CRC]] = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }
// PAUTHTEST-DAG: attributes #[[ATTR_RESOLVER]] = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }
// PAUTHTEST-DAG: attributes #[[ATTR_DEFAULT]] = { {{.*}}"ptrauth-auth-traps" "ptrauth-calls" "ptrauth-returns"{{.*}} }
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