Update FEAT_PAuth_LR behaviour for AArch64 #90614
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@llvm/pr-subscribers-clang-driver @llvm/pr-subscribers-backend-aarch64 Author: Jack Styles (Stylie777) ChangesCurrently, LLVM enables Full diff: https://github.com/llvm/llvm-project/pull/90614.diff 8 Files Affected:
diff --git a/clang/lib/Basic/Targets/AArch64.cpp b/clang/lib/Basic/Targets/AArch64.cpp
index c8d243a8fb7aea..5a46a3e6c6fd3e 100644
--- a/clang/lib/Basic/Targets/AArch64.cpp
+++ b/clang/lib/Basic/Targets/AArch64.cpp
@@ -224,7 +224,7 @@ bool AArch64TargetInfo::validateBranchProtection(StringRef Spec, StringRef,
BranchProtectionInfo &BPI,
StringRef &Err) const {
llvm::ARM::ParsedBranchProtection PBP;
- if (!llvm::ARM::parseBranchProtection(Spec, PBP, Err))
+ if (!llvm::ARM::parseBranchProtection(Spec, PBP, Err, HasPAuthLR))
return false;
BPI.SignReturnAddr =
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 1988a90a48ae6b..057a0d850ed9b3 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -1511,7 +1511,23 @@ static void CollectARMPACBTIOptions(const ToolChain &TC, const ArgList &Args,
} else {
StringRef DiagMsg;
llvm::ARM::ParsedBranchProtection PBP;
- if (!llvm::ARM::parseBranchProtection(A->getValue(), PBP, DiagMsg))
+
+ // To know if we need to enable PAuth-LR As part of the standard branch
+ // protection option, it needs to be determined if the feature has been
+ // activated in the `march` argument. This information is stored within the
+ // CmdArgs variable and can be found using a search.
+ if (isAArch64) {
+ auto isPAuthLR = [](const char *member) {
+ llvm::AArch64::ExtensionInfo pauthlr_extension =
+ llvm::AArch64::getExtensionByID(llvm::AArch64::AEK_PAUTHLR);
+ return (pauthlr_extension.Feature.compare(member) == 0);
+ };
+
+ if (std::any_of(CmdArgs.begin(), CmdArgs.end(), isPAuthLR))
+ EnablePAuthLR = true;
+ }
+ if (!llvm::ARM::parseBranchProtection(A->getValue(), PBP, DiagMsg,
+ EnablePAuthLR))
D.Diag(diag::err_drv_unsupported_option_argument)
<< A->getSpelling() << DiagMsg;
if (!isAArch64 && PBP.Key == "b_key")
diff --git a/clang/test/Preprocessor/aarch64-target-features.c b/clang/test/Preprocessor/aarch64-target-features.c
index 85762b7fed4d71..31af14f748b765 100644
--- a/clang/test/Preprocessor/aarch64-target-features.c
+++ b/clang/test/Preprocessor/aarch64-target-features.c
@@ -616,6 +616,9 @@
// ================== Check Armv9.5-A Pointer Authentication Enhancements(PAuth_LR).
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-LR-OFF %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv9.5-a -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-LR-OFF %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv9.5-a -mbranch-protection=standard -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR-OFF,CHECK-BRANCH-PROTECTION-NO-PC %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv9.5-a+pauth-lr -mbranch-protection=standard -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR,CHECK-BRANCH-PROTECTION-PC %s
+// RUN: %clang -target arm64-none-linux-gnu -march=armv9.5-a+nopauth-lr -mbranch-protection=standard -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR-OFF,CHECK-BRANCH-PROTECTION-NO-PC %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth -mbranch-protection=none -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-LR-OFF %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth-lr -mbranch-protection=none -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-LR %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth-lr -mbranch-protection=bti -x c -E -dM %s -o - | FileCheck -check-prefix=CHECK-PAUTH-LR %s
@@ -636,6 +639,7 @@
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth-lr -mbranch-protection=pac-ret+pc+b-key -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR,CHECK-BRANCH-PROTECTION-PC-BKEY %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth-lr -mbranch-protection=pac-ret+pc+leaf -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR,CHECK-BRANCH-PROTECTION-PC-LEAF %s
// RUN: %clang -target arm64-none-linux-gnu -march=armv8-a+pauth-lr -mbranch-protection=pac-ret+pc+leaf+b-key -x c -E -dM %s -o - | FileCheck -check-prefixes=CHECK-PAUTH-LR,CHECK-BRANCH-PROTECTION-PC-LEAF-BKEY %s
+// CHECK-BRANCH-PROTECTION-NO-PC: #define __ARM_FEATURE_PAC_DEFAULT 1
// CHECK-BRANCH-PROTECTION-PC: #define __ARM_FEATURE_PAC_DEFAULT 9
// CHECK-BRANCH-PROTECTION-PC-BKEY: #define __ARM_FEATURE_PAC_DEFAULT 10
// CHECK-BRANCH-PROTECTION-PC-LEAF: #define __ARM_FEATURE_PAC_DEFAULT 13
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index 46d79d6c5822b1..e98d31694046c8 100644
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -76,6 +76,11 @@ Changes to the AArch64 Backend
* Added support for Cortex-A78AE, Cortex-A520AE, Cortex-A720AE,
Neoverse-N3, Neoverse-V3 and Neoverse-V3AE CPUs.
+* `-mbranch-protection=standard` now enables FEAT_PAuth_LR by
+default when the feature is enabled. The new behaviour results
+in `standard` being equal to `bti+pac-ret+pc` when `+pauth-lr`
+is passed as part of `-mcpu=`options.
+
Changes to the AMDGPU Backend
-----------------------------
diff --git a/llvm/include/llvm/TargetParser/AArch64TargetParser.h b/llvm/include/llvm/TargetParser/AArch64TargetParser.h
index 0d1cfd152151aa..d39fc5667358a0 100644
--- a/llvm/include/llvm/TargetParser/AArch64TargetParser.h
+++ b/llvm/include/llvm/TargetParser/AArch64TargetParser.h
@@ -853,6 +853,8 @@ inline constexpr Alias CpuAliases[] = {{"cobalt-100", "neoverse-n2"},
inline constexpr Alias ExtAliases[] = {{"rdma", "rdm"}};
+const ExtensionInfo &getExtensionByID(ArchExtKind(ExtID));
+
bool getExtensionFeatures(
const AArch64::ExtensionBitset &Extensions,
std::vector<StringRef> &Features);
diff --git a/llvm/include/llvm/TargetParser/ARMTargetParserCommon.h b/llvm/include/llvm/TargetParser/ARMTargetParserCommon.h
index 8ae553ca80ddc3..f6115718e9f5fd 100644
--- a/llvm/include/llvm/TargetParser/ARMTargetParserCommon.h
+++ b/llvm/include/llvm/TargetParser/ARMTargetParserCommon.h
@@ -46,7 +46,7 @@ struct ParsedBranchProtection {
};
bool parseBranchProtection(StringRef Spec, ParsedBranchProtection &PBP,
- StringRef &Err);
+ StringRef &Err, bool EnablePAuthLR = false);
} // namespace ARM
} // namespace llvm
diff --git a/llvm/lib/TargetParser/AArch64TargetParser.cpp b/llvm/lib/TargetParser/AArch64TargetParser.cpp
index 71099462d5ecff..026214e7e2eac5 100644
--- a/llvm/lib/TargetParser/AArch64TargetParser.cpp
+++ b/llvm/lib/TargetParser/AArch64TargetParser.cpp
@@ -280,3 +280,8 @@ bool AArch64::ExtensionSet::parseModifier(StringRef Modifier) {
}
return false;
}
+
+const AArch64::ExtensionInfo &
+AArch64::getExtensionByID(AArch64::ArchExtKind ExtID) {
+ return lookupExtensionByID(ExtID);
+}
diff --git a/llvm/lib/TargetParser/ARMTargetParserCommon.cpp b/llvm/lib/TargetParser/ARMTargetParserCommon.cpp
index 45d04f9bcbfb6a..d6ce6581bb1a92 100644
--- a/llvm/lib/TargetParser/ARMTargetParserCommon.cpp
+++ b/llvm/lib/TargetParser/ARMTargetParserCommon.cpp
@@ -139,7 +139,7 @@ ARM::EndianKind ARM::parseArchEndian(StringRef Arch) {
// returned in `PBP`. Returns false in error, with `Err` containing
// an erroneous part of the spec.
bool ARM::parseBranchProtection(StringRef Spec, ParsedBranchProtection &PBP,
- StringRef &Err) {
+ StringRef &Err, bool EnablePAuthLR) {
PBP = {"none", "a_key", false, false, false};
if (Spec == "none")
return true; // defaults are ok
@@ -148,6 +148,7 @@ bool ARM::parseBranchProtection(StringRef Spec, ParsedBranchProtection &PBP,
PBP.Scope = "non-leaf";
PBP.BranchTargetEnforcement = true;
PBP.GuardedControlStack = true;
+ PBP.BranchProtectionPAuthLR = EnablePAuthLR;
return true;
}
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Currently, an extension cannot be found using the ExtID. To address this, the function `lookupExtensionByID` has been added to the `ExtensionSet` Class so it can be targeted from outside the function. This will allow for the Extensions Information to be searched for and stored externally to the ExtensionSet Class. This enables being able to search for if Architecture Features have been enabled by the user in the command line.
branch protection when the feature is available Currently, LLVM implements the `standard` option as `bti+pac-ret` for ARM and AArch64. Following discussions with the GNU developemnt team within Arm it was decided to align the behaviour of `standard` to match across the different compilers. To ensure the behaviour is aligned. LLVM has been updated to implement `standard` as `bti+pac-ret+pc` by default when `+pauth-lr` is passed as part of the `-march` argument.
This was causing a build failure due to using the incorrect syntax for quoting.
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Currently, LLVM enables
-mbranch-protection=standardasbti+pac-ret. To align LLVM with the behaviour in GNU, this has been updated tobti+pac-ret+pcwhen FEAT_PAuth_LR is enabled as an optional feature via the-mcpu=options. If this is not enabled, then this will revert to the existing behaviour.