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DanielKristofKisstru
DanielKristofKiss
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[Arm][AArch64][Clang] Respect function's branch protection attributes. (#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. (cherry picked from commit 9e9fa00)
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5 files changed

+52
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lines changed

‎clang/lib/CodeGen/CGCall.cpp

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2032,7 +2032,7 @@ static void getTrivialDefaultFunctionAttributes(
20322032
}
20332033

20342034
TargetInfo::BranchProtectionInfo BPI(LangOpts);
2035-
TargetCodeGenInfo::setBranchProtectionFnAttributes(BPI, FuncAttrs);
2035+
TargetCodeGenInfo::initBranchProtectionFnAttributes(BPI, FuncAttrs);
20362036
}
20372037

20382038
/// Merges `target-features` from \TargetOpts and \F, and sets the result in

‎clang/lib/CodeGen/TargetInfo.cpp

Lines changed: 28 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -209,13 +209,37 @@ llvm::Value *TargetCodeGenInfo::createEnqueuedBlockKernel(
209209

210210
void TargetCodeGenInfo::setBranchProtectionFnAttributes(
211211
const TargetInfo::BranchProtectionInfo &BPI, llvm::Function &F) {
212-
llvm::AttrBuilder FuncAttrs(F.getContext());
213-
setBranchProtectionFnAttributes(BPI, FuncAttrs);
214-
F.addFnAttrs(FuncAttrs);
212+
// Called on already created and initialized function where attributes already
213+
// set from command line attributes but some might need to be removed as the
214+
// actual BPI is different.
215+
if (BPI.SignReturnAddr != LangOptions::SignReturnAddressScopeKind::None) {
216+
F.addFnAttr("sign-return-address", BPI.getSignReturnAddrStr());
217+
F.addFnAttr("sign-return-address-key", BPI.getSignKeyStr());
218+
} else {
219+
if (F.hasFnAttribute("sign-return-address"))
220+
F.removeFnAttr("sign-return-address");
221+
if (F.hasFnAttribute("sign-return-address-key"))
222+
F.removeFnAttr("sign-return-address-key");
223+
}
224+
225+
auto AddRemoveAttributeAsSet = [&](bool Set, const StringRef &ModAttr) {
226+
if (Set)
227+
F.addFnAttr(ModAttr);
228+
else if (F.hasFnAttribute(ModAttr))
229+
F.removeFnAttr(ModAttr);
230+
};
231+
232+
AddRemoveAttributeAsSet(BPI.BranchTargetEnforcement,
233+
"branch-target-enforcement");
234+
AddRemoveAttributeAsSet(BPI.BranchProtectionPAuthLR,
235+
"branch-protection-pauth-lr");
236+
AddRemoveAttributeAsSet(BPI.GuardedControlStack, "guarded-control-stack");
215237
}
216238

217-
void TargetCodeGenInfo::setBranchProtectionFnAttributes(
239+
void TargetCodeGenInfo::initBranchProtectionFnAttributes(
218240
const TargetInfo::BranchProtectionInfo &BPI, llvm::AttrBuilder &FuncAttrs) {
241+
// Only used for initializing attributes in the AttrBuilder, which will not
242+
// contain any of these attributes so no need to remove anything.
219243
if (BPI.SignReturnAddr != LangOptions::SignReturnAddressScopeKind::None) {
220244
FuncAttrs.addAttribute("sign-return-address", BPI.getSignReturnAddrStr());
221245
FuncAttrs.addAttribute("sign-return-address-key", BPI.getSignKeyStr());

‎clang/lib/CodeGen/TargetInfo.h

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -414,13 +414,16 @@ class TargetCodeGenInfo {
414414
return nullptr;
415415
}
416416

417+
// Set the Branch Protection Attributes of the Function accordingly to the
418+
// BPI. Remove attributes that contradict with current BPI.
417419
static void
418420
setBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
419421
llvm::Function &F);
420422

423+
// Add the Branch Protection Attributes of the FuncAttrs.
421424
static void
422-
setBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
423-
llvm::AttrBuilder &FuncAttrs);
425+
initBranchProtectionFnAttributes(const TargetInfo::BranchProtectionInfo &BPI,
426+
llvm::AttrBuilder &FuncAttrs);
424427

425428
protected:
426429
static std::string qualifyWindowsLibrary(StringRef Lib);

‎clang/test/CodeGen/aarch64-branch-protection-attr.c

Lines changed: 12 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,18 @@
11
// REQUIRES: aarch64-registered-target
22
// RUN: %clang_cc1 -triple aarch64 -emit-llvm -target-cpu generic -target-feature +v8.5a %s -o - \
33
// RUN: | FileCheck %s --check-prefix=CHECK
4+
// RUN: %clang_cc1 -triple aarch64 -emit-llvm -target-cpu generic -target-feature +v8.5a -mbranch-target-enforce %s -o - \
5+
// RUN: | FileCheck %s --check-prefix=CHECK
6+
// RUN: %clang_cc1 -triple aarch64 -emit-llvm -target-cpu generic -target-feature +v8.5a -mguarded-control-stack %s -o - \
7+
// RUN: | FileCheck %s --check-prefix=CHECK
8+
// 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 - \
9+
// RUN: | FileCheck %s --check-prefix=CHECK
10+
// 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 - \
11+
// RUN: | FileCheck %s --check-prefix=CHECK
12+
// 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 - \
13+
// RUN: | FileCheck %s --check-prefix=CHECK
14+
// 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 - \
15+
// RUN: | FileCheck %s --check-prefix=CHECK
416

517
__attribute__ ((target("branch-protection=none")))
618
void none() {}
@@ -83,7 +95,6 @@ void gcs() {}
8395

8496
// CHECK-DAG: attributes #[[#BTIPACLEAF]] = { {{.*}} "branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"
8597

86-
8798
// CHECK-DAG: attributes #[[#PAUTHLR]] = { {{.*}} "branch-protection-pauth-lr" {{.*}}"sign-return-address"="non-leaf" "sign-return-address-key"="a_key"
8899

89100
// CHECK-DAG: attributes #[[#PAUTHLR_BKEY]] = { {{.*}} "branch-protection-pauth-lr" {{.*}}"sign-return-address"="non-leaf" "sign-return-address-key"="b_key"

‎clang/test/CodeGen/arm-branch-protection-attr-1.c

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,12 @@
11
// REQUIRES: arm-registered-target
22
// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -emit-llvm %s -o - \
33
// RUN: | FileCheck %s --check-prefix=CHECK
4+
// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -mbranch-target-enforce -emit-llvm %s -o - \
5+
// RUN: | FileCheck %s --check-prefix=CHECK
6+
// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -msign-return-address=all -emit-llvm %s -o - \
7+
// RUN: | FileCheck %s --check-prefix=CHECK
8+
// RUN: %clang_cc1 -triple thumbv7m-unknown-unknown-eabi -mbranch-target-enforce -msign-return-address=all -emit-llvm %s -o - \
9+
// RUN: | FileCheck %s --check-prefix=CHECK
410

511
__attribute__((target("branch-protection=none"))) void none() {}
612
// CHECK: define{{.*}} void @none() #[[#NONE:]]

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