[Arm][AArch64][Clang] Respect function's branch protection attributes. (

llvm#101978) Default attributes assigned to all functions according to the command line parameters. Some functions might have their own attributes and we need to set or remove attributes accordingly. Tests are updated to test this scenarios too.
bwendling · Aug 15, 2024 · 5b1be9e · 5b1be9e
1 parent 2de1039
commit 5b1be9e
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Showing 5 changed files with 52 additions and 8 deletions.
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
@@ -2010,7 +2010,7 @@ static void getTrivialDefaultFunctionAttributes(
   }
 
   TargetInfo::BranchProtectionInfo BPI(LangOpts);
-  TargetCodeGenInfo::setBranchProtectionFnAttributes(BPI, FuncAttrs);
+  TargetCodeGenInfo::initBranchProtectionFnAttributes(BPI, FuncAttrs);
 }
 
 /// Merges `target-features` from \TargetOpts and \F, and sets the result in

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
@@ -209,13 +209,37 @@ llvm::Value *TargetCodeGenInfo::createEnqueuedBlockKernel(
 
 void TargetCodeGenInfo::setBranchProtectionFnAttributes(
     const TargetInfo::BranchProtectionInfo &BPI, llvm::Function &F) {
-  llvm::AttrBuilder FuncAttrs(F.getContext());
-  setBranchProtectionFnAttributes(BPI, FuncAttrs);
-  F.addFnAttrs(FuncAttrs);
+  // Called on already created and initialized function where attributes already
+  // set from command line attributes but some might need to be removed as the
+  // actual BPI is different.
+  if (BPI.SignReturnAddr != LangOptions::SignReturnAddressScopeKind::None) {
+    F.addFnAttr("sign-return-address", BPI.getSignReturnAddrStr());
+    F.addFnAttr("sign-return-address-key", BPI.getSignKeyStr());
+  } else {
+    if (F.hasFnAttribute("sign-return-address"))
+      F.removeFnAttr("sign-return-address");
+    if (F.hasFnAttribute("sign-return-address-key"))
+      F.removeFnAttr("sign-return-address-key");
+  }
+
+  auto AddRemoveAttributeAsSet = [&](bool Set, const StringRef &ModAttr) {
+    if (Set)
+      F.addFnAttr(ModAttr);
+    else if (F.hasFnAttribute(ModAttr))
+      F.removeFnAttr(ModAttr);
+  };
+
+  AddRemoveAttributeAsSet(BPI.BranchTargetEnforcement,
+                          "branch-target-enforcement");
+  AddRemoveAttributeAsSet(BPI.BranchProtectionPAuthLR,
+                          "branch-protection-pauth-lr");
+  AddRemoveAttributeAsSet(BPI.GuardedControlStack, "guarded-control-stack");
 }
 
-void TargetCodeGenInfo::setBranchProtectionFnAttributes(
+void TargetCodeGenInfo::initBranchProtectionFnAttributes(
     const TargetInfo::BranchProtectionInfo &BPI, llvm::AttrBuilder &FuncAttrs) {
+  // Only used for initializing attributes in the AttrBuilder, which will not
+  // contain any of these attributes so no need to remove anything.
   if (BPI.SignReturnAddr != LangOptions::SignReturnAddressScopeKind::None) {
     FuncAttrs.addAttribute("sign-return-address", BPI.getSignReturnAddrStr());
     FuncAttrs.addAttribute("sign-return-address-key", BPI.getSignKeyStr());

diff --git a/clang/lib/CodeGen/TargetInfo.h b/clang/lib/CodeGen/TargetInfo.h
@@ -423,13 +423,16 @@ class TargetCodeGenInfo {
     return nullptr;
   }
 
+  // Set the Branch Protection Attributes of the Function accordingly to the
+  // BPI. Remove attributes that contradict with current BPI.
   static void
   setBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
                                   llvm::Function &F);
 
+  // Add the Branch Protection Attributes of the FuncAttrs.
   static void
-  setBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
-                                  llvm::AttrBuilder &FuncAttrs);
+  initBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
+                                   llvm::AttrBuilder &FuncAttrs);
 
 protected:
   static std::string qualifyWindowsLibrary(StringRef Lib);

diff --git a/clang/test/CodeGen/aarch64-branch-protection-attr.c b/clang/test/CodeGen/aarch64-branch-protection-attr.c
@@ -1,6 +1,18 @@
 // REQUIRES: aarch64-registered-target
 // RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a %s -o - \
 // RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -mbranch-target-enforce %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -mguarded-control-stack %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -msign-return-address=non-leaf -msign-return-address-key=a_key %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -msign-return-address=all -msign-return-address-key=b_key %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -mbranch-protection-pauth-lr -msign-return-address=all -msign-return-address-key=a_key %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple aarch64 -emit-llvm  -target-cpu generic -target-feature +v8.5a -mguarded-control-stack -mbranch-target-enforce -mbranch-protection-pauth-lr -msign-return-address=all -msign-return-address-key=a_key %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
 
 __attribute__ ((target("branch-protection=none")))
 void none() {}
@@ -83,7 +95,6 @@ void gcs() {}
 
 // CHECK-DAG: attributes #[[#BTIPACLEAF]] = { {{.*}} "branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"
 
-
 // CHECK-DAG: attributes #[[#PAUTHLR]] = { {{.*}} "branch-protection-pauth-lr" {{.*}}"sign-return-address"="non-leaf" "sign-return-address-key"="a_key"
 
 // CHECK-DAG: attributes #[[#PAUTHLR_BKEY]] = { {{.*}} "branch-protection-pauth-lr" {{.*}}"sign-return-address"="non-leaf" "sign-return-address-key"="b_key"

diff --git a/clang/test/CodeGen/arm-branch-protection-attr-1.c b/clang/test/CodeGen/arm-branch-protection-attr-1.c
@@ -1,6 +1,12 @@
 // REQUIRES: arm-registered-target
 // RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -emit-llvm %s -o - \
 // RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -mbranch-target-enforce -emit-llvm %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -msign-return-address=all -emit-llvm %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
+// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -mbranch-target-enforce -msign-return-address=all -emit-llvm %s -o - \
+// RUN:                               | FileCheck %s --check-prefix=CHECK
 
 __attribute__((target("branch-protection=none"))) void none() {}
 // CHECK: define{{.*}} void @none() #[[#NONE:]]