Rollup merge of #156712 - jchlanda:jakub/pac_config, r=davidtwco

Pointer authentication config and user facing options

This patch brings:
* unified handling of pointer authentication options through:
  `-Zpointer-authentication`, with possible values:
  `aarch64-jump-table-hardening`, `auth-traps`, `calls`, `elf-got`,
  `function-pointer-type-discrimination`, `indirect-gotos`, `init-fini`,
  `init-fini-address-discrimination`, `return-addresses`. Toggled with
  `+`/`-`.
* centralized handling of pointer authentication features. Session holds
  `pointer_auth_config: Option<PointerAuthConfig>`
* encapsulation of schema for function pointers and init/fini through
  `PointerAuthSchema`. This allowed for retiring of `PacMetadata`.
* refactor enabling of pointer authentication in code, instead of
  relying on the target (`pauthtest`) use the session

Author: jhpratt

compiler/rustc_codegen_gcc/src/common.rs

@@ -2,12 +2,12 @@ use gccjit::{LValue, RValue, ToRValue, Type};
 use rustc_abi::Primitive::Pointer;
 use rustc_abi::{self as abi, HasDataLayout};
 use rustc_codegen_ssa::traits::{
-    BaseTypeCodegenMethods, ConstCodegenMethods, MiscCodegenMethods, PacMetadata,
-    StaticCodegenMethods,
+    BaseTypeCodegenMethods, ConstCodegenMethods, MiscCodegenMethods, StaticCodegenMethods,
 };
 use rustc_middle::mir::Mutability;
 use rustc_middle::mir::interpret::{GlobalAlloc, PointerArithmetic, Scalar};
 use rustc_middle::ty::layout::LayoutOf;
+use rustc_session::PointerAuthSchema;
 
 use crate::consts::const_alloc_to_gcc;
 use crate::context::{CodegenCx, new_array_type};
@@ -247,7 +247,7 @@ impl<'gcc, 'tcx> ConstCodegenMethods for CodegenCx<'gcc, 'tcx> {
         cv: Scalar,
         layout: abi::Scalar,
         ty: Type<'gcc>,
-        _pac: Option<PacMetadata>,
+        _schema: Option<&PointerAuthSchema>,
     ) -> RValue<'gcc> {
         let bitsize = if layout.is_bool() { 1 } else { layout.size(self).bits() };
         match cv {

compiler/rustc_codegen_gcc/src/context.rs

@@ -5,9 +5,7 @@ use gccjit::{Block, CType, Context, Function, FunctionType, LValue, Location, RV
 use rustc_abi::{Align, HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_codegen_ssa::base::wants_msvc_seh;
 use rustc_codegen_ssa::errors as ssa_errors;
-use rustc_codegen_ssa::traits::{
-    BackendTypes, BaseTypeCodegenMethods, MiscCodegenMethods, PacMetadata,
-};
+use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeCodegenMethods, MiscCodegenMethods};
 use rustc_data_structures::base_n::{ALPHANUMERIC_ONLY, ToBaseN};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_middle::mir::interpret::Allocation;
@@ -18,9 +16,9 @@ use rustc_middle::ty::layout::{
     LayoutOfHelpers,
 };
 use rustc_middle::ty::{self, ExistentialTraitRef, Instance, Ty, TyCtxt};
-use rustc_session::Session;
 #[cfg(feature = "master")]
 use rustc_session::config::DebugInfo;
+use rustc_session::{PointerAuthSchema, Session};
 use rustc_span::{DUMMY_SP, Span, Symbol, respan};
 use rustc_target::spec::{HasTargetSpec, HasX86AbiOpt, Target, TlsModel, X86Abi};
 
@@ -400,7 +398,11 @@ impl<'gcc, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         get_fn(self, instance)
     }
 
-    fn get_fn_addr(&self, instance: Instance<'tcx>, _pac: Option<PacMetadata>) -> RValue<'gcc> {
+    fn get_fn_addr(
+        &self,
+        instance: Instance<'tcx>,
+        _pointer_auth_schema: Option<&PointerAuthSchema>,
+    ) -> RValue<'gcc> {
         let func_name = self.tcx.symbol_name(instance).name;
 
         let func = if let Some(variable) = self.get_declared_value(func_name) {

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -12,12 +12,9 @@ use rustc_session::config::{
 };
 use rustc_span::sym;
 use rustc_symbol_mangling::mangle_internal_symbol;
-use rustc_target::spec::{
-    Arch, FramePointer, LlvmAbi, SanitizerSet, StackProbeType, StackProtector,
-};
+use rustc_target::spec::{Arch, FramePointer, SanitizerSet, StackProbeType, StackProtector};
 use smallvec::SmallVec;
 
-use crate::common::pauth_fn_attrs;
 use crate::context::SimpleCx;
 use crate::errors::{PackedStackBackchainNeedsSoftfloat, SanitizerMemtagRequiresMte};
 use crate::llvm::AttributePlace::Function;
@@ -668,8 +665,9 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         }
     }
 
-    if sess.target.llvm_abiname == LlvmAbi::Pauthtest {
-        for &ptrauth_attr in pauth_fn_attrs() {
+    if sess.pointer_authentication() {
+        let cfg = sess.pointer_auth_config.as_ref().unwrap();
+        for ptrauth_attr in cfg.fn_attrs() {
             to_add.push(llvm::CreateAttrString(cx.llcx, ptrauth_attr));
         }
     }

compiler/rustc_codegen_llvm/src/base.rs

@@ -25,13 +25,12 @@ use rustc_middle::mono::Visibility;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{DebugInfo, Offload};
 use rustc_span::Symbol;
-use rustc_target::spec::{LlvmAbi, SanitizerSet};
+use rustc_target::spec::SanitizerSet;
 
 use super::ModuleLlvm;
 use crate::attributes;
 use crate::builder::Builder;
 use crate::builder::gpu_offload::OffloadGlobals;
-use crate::common::pauth_fn_attrs;
 use crate::context::CodegenCx;
 use crate::llvm::{self, Value};
 
@@ -137,8 +136,9 @@ pub(crate) fn compile_codegen_unit(
                 // FIXME(jchlanda) If it ever becomes necessary to ensure that all compiler
                 // generated functions receive the ptrauth-* attributes, `declare_fn` or
                 // `declare_raw_fn` could be used to provide those.
-                if cx.sess().target.llvm_abiname == LlvmAbi::Pauthtest {
-                    for &ptrauth_attr in pauth_fn_attrs() {
+                if cx.sess().pointer_authentication() {
+                    let cfg = cx.sess().pointer_auth_config.as_ref().unwrap();
+                    for ptrauth_attr in cfg.fn_attrs() {
                         attrs.push(llvm::CreateAttrString(cx.llcx, ptrauth_attr));
                     }
                 }
@@ -158,28 +158,22 @@ pub(crate) fn compile_codegen_unit(
                 cx.add_objc_module_flags();
             }
 
-            if cx.sess().target.llvm_abiname == LlvmAbi::Pauthtest {
-                // FIXME(jchlanda): In LLVM/Clang, there are also `aarch64-elf-pauthabi-platform`
-                // and `aarch64-elf-pauthabi-version` module flags. These are emitted into the
-                // PAuth core info section of the resulting ELF, which the linker uses to enforce
-                // binary compatibility.
-                //
-                // We intentionally do not emit these flags now, since only a subset of features
-                // included in clang's pauthtest is currently supported. By default, the absence of
-                // this info is treated as compatible with any binary.
-                //
-                // Please note, that this would cause compatibility issues, specifically runtime
-                // crashes due to authentication failures (while compiling and linking
-                // successfully) when linking against binaries that support larger set of features
-                // (for example, signing of C++ member function pointers, virtual function
-                // pointers, virtual table pointers).
-                //
-                // Link to PAuth core info documentation:
-                // <https://github.com/ARM-software/abi-aa/blob/2025Q4/pauthabielf64/pauthabielf64.rst#core-information>
-                if cx.sess().opts.unstable_opts.ptrauth_elf_got {
+            if cx.sess().pointer_authentication() {
+                let cfg = cx.sess().pointer_auth_config.as_ref().unwrap();
+
+                let aarch64_elf_pauthabi_version =
+                    cfg.calculate_pauth_abi_version(&cx.sess().target);
+                if aarch64_elf_pauthabi_version != 0 {
+                    cx.add_ptrauth_pauthabi_version_and_platform_flags(
+                        aarch64_elf_pauthabi_version,
+                    );
+                }
+                if cfg.elf_got {
                     cx.add_ptrauth_elf_got_flag();
                 }
-                cx.add_ptrauth_sign_personality_flag();
+                if cx.sess().pointer_authentication_functions().is_some() {
+                    cx.add_ptrauth_sign_personality_flag();
+                }
             }
 
             // Finalize code coverage by injecting the coverage map. Note, the coverage map will

compiler/rustc_codegen_llvm/src/builder.rs

@@ -26,7 +26,7 @@ use rustc_sanitizers::{cfi, kcfi};
 use rustc_session::config::OptLevel;
 use rustc_span::Span;
 use rustc_target::callconv::{FnAbi, PassMode};
-use rustc_target::spec::{Arch, HasTargetSpec, LlvmAbi, SanitizerSet, Target};
+use rustc_target::spec::{Arch, HasTargetSpec, SanitizerSet, Target};
 use smallvec::SmallVec;
 use tracing::{debug, instrument};
 
@@ -2039,7 +2039,7 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
         llfn: &'ll Value,
         fn_abi: Option<&FnAbi<'tcx, Ty<'tcx>>>,
     ) -> Option<llvm::OperandBundleBox<'ll>> {
-        if self.sess().target.llvm_abiname != LlvmAbi::Pauthtest {
+        if self.sess().pointer_authentication_functions().is_none() {
             return None;
         }
         // Pointer authentication support is currently limited to extern "C" calls; filter out other

compiler/rustc_codegen_llvm/src/common.rs

@@ -16,7 +16,7 @@ use rustc_middle::bug;
 use rustc_middle::mir::interpret::{GlobalAlloc, PointerArithmetic, Scalar};
 use rustc_middle::ty::{Instance, TyCtxt};
 use rustc_session::cstore::DllImport;
-use rustc_target::spec::LlvmAbi;
+use rustc_session::{PointerAuthAddressDiscriminator, PointerAuthSchema};
 use tracing::debug;
 
 use crate::consts::{IsInitOrFini, IsStatic, const_alloc_to_llvm};
@@ -26,27 +26,13 @@ use crate::llvm::{
     self, BasicBlock, ConstantInt, FALSE, TRUE, ToLlvmBool, Type, Value, const_ptr_auth,
 };
 
-#[inline]
-pub(crate) fn pauth_fn_attrs() -> &'static [&'static str] {
-    // FIXME(jchlanda) This is not an exhaustive list of all `ptrauth`-related attributes, but only
-    // those currently supported. The list is expected to grow as additional functionality is
-    // implemented, particularly for C++ interoperability.
-    &[
-        "aarch64-jump-table-hardening",
-        "ptrauth-indirect-gotos",
-        "ptrauth-calls",
-        "ptrauth-returns",
-        "ptrauth-auth-traps",
-    ]
-}
-
 pub(crate) fn maybe_sign_fn_ptr<'ll, 'tcx>(
     cx: &CodegenCx<'ll, '_>,
     instance: Instance<'tcx>,
     llfn: &'ll llvm::Value,
-    pac: PacMetadata,
+    schema: &PointerAuthSchema,
 ) -> &'ll llvm::Value {
-    if cx.sess().target.llvm_abiname != LlvmAbi::Pauthtest {
+    if cx.tcx.sess.pointer_authentication_functions().is_none() {
         return llfn;
     }
 
@@ -68,16 +54,16 @@ pub(crate) fn maybe_sign_fn_ptr<'ll, 'tcx>(
         return llfn;
     }
 
-    let addr_diversity = match pac.addr_diversity {
-        AddressDiversity::None => None,
-        AddressDiversity::Real => Some(llfn),
-        AddressDiversity::Synthetic(val) => {
+    let addr_diversity = match schema.is_address_discriminated {
+        PointerAuthAddressDiscriminator::HardwareAddress(true) => Some(llfn),
+        PointerAuthAddressDiscriminator::HardwareAddress(false) => None,
+        PointerAuthAddressDiscriminator::Synthetic(val) => {
             let llval = cx.const_u64(val);
             let llty = cx.val_ty(llfn);
             Some(unsafe { llvm::LLVMConstIntToPtr(llval, llty) })
         }
     };
-    const_ptr_auth(llfn, pac.key, pac.disc, addr_diversity)
+    const_ptr_auth(llfn, schema.key as u32, schema.constant_discriminator as u64, addr_diversity)
 }
 
 /*
@@ -331,7 +317,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
         cv: Scalar,
         layout: abi::Scalar,
         llty: &'ll Type,
-        pac: Option<PacMetadata>,
+        schema: Option<&PointerAuthSchema>,
     ) -> &'ll Value {
         let bitsize = if layout.is_bool() { 1 } else { layout.size(self).bits() };
         match cv {
@@ -387,7 +373,7 @@ impl<'ll, 'tcx> ConstCodegenMethods for CodegenCx<'ll, 'tcx> {
                             value
                         }
                     }
-                    GlobalAlloc::Function { instance, .. } => self.get_fn_addr(instance, pac),
+                    GlobalAlloc::Function { instance, .. } => self.get_fn_addr(instance, schema),
                     GlobalAlloc::VTable(ty, dyn_ty) => {
                         let alloc = self
                             .tcx

compiler/rustc_codegen_llvm/src/consts.rs

@@ -17,7 +17,7 @@ use rustc_middle::ty::layout::{HasTypingEnv, LayoutOf};
 use rustc_middle::ty::{self, Instance};
 use rustc_middle::{bug, span_bug};
 use rustc_span::Symbol;
-use rustc_target::spec::{Arch, LlvmAbi};
+use rustc_target::spec::Arch;
 use tracing::{debug, instrument, trace};
 
 use crate::common::CodegenCx;
@@ -32,6 +32,7 @@ pub(crate) enum IsStatic {
     No,
 }
 /// Indicates whether a symbol is part of `.init_array` or `.fini_array`.
+#[derive(PartialEq)]
 pub(crate) enum IsInitOrFini {
     Yes,
     No,
@@ -120,31 +121,22 @@ pub(crate) fn const_alloc_to_llvm<'ll>(
             as u64;
 
         let address_space = cx.tcx.global_alloc(prov.alloc_id()).address_space(cx);
-        // Under pointer authentication, function pointers stored in init/fini arrays need special
-        // handling.
-        let pac_metadata = Some(
-            if cx.sess().target.llvm_abiname == LlvmAbi::Pauthtest
-                && matches!(is_init_fini, IsInitOrFini::Yes)
-            {
-                PacMetadata {
-                    // Must correspond to ptrauth_key_init_fini_pointer from `ptrauth.h`.
-                    key: 0,
-                    // ptrauth_string_discriminator("init_fini")
-                    disc: 0xd9d4,
-                    addr_diversity: AddressDiversity::Synthetic(1),
-                }
-            } else {
-                PacMetadata::default()
-            },
-        );
+        let schema = if cx.sess().pointer_authentication() {
+            match is_init_fini {
+                IsInitOrFini::Yes => cx.sess().pointer_authentication_init_fini(),
+                IsInitOrFini::No => cx.sess().pointer_authentication_functions(),
+            }
+        } else {
+            None
+        };
         llvals.push(cx.scalar_to_backend_with_pac(
             InterpScalar::from_pointer(Pointer::new(prov, Size::from_bytes(ptr_offset)), &cx.tcx),
             Scalar::Initialized {
                 value: Primitive::Pointer(address_space),
                 valid_range: WrappingRange::full(pointer_size),
             },
             cx.type_ptr_ext(address_space),
-            pac_metadata,
+            schema,
         ));
         next_offset = offset + pointer_size_bytes;
     }
@@ -221,7 +213,7 @@ fn check_and_apply_linkage<'ll, 'tcx>(
                 let fn_sig = sig.with(*header);
                 let fn_abi = cx.fn_abi_of_fn_ptr(fn_sig, ty::List::empty());
                 // Decide if the initializer needs to be signed
-                if cx.sess().target.llvm_abiname == LlvmAbi::Pauthtest
+                if cx.sess().pointer_authentication()
                     && matches!(fn_sig.abi(), ExternAbi::C { .. } | ExternAbi::System { .. })
                 {
                     should_sign = true;

compiler/rustc_codegen_llvm/src/context.rs

@@ -20,10 +20,10 @@ use rustc_middle::ty::layout::{
 };
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
-use rustc_session::Session;
 use rustc_session::config::{
     BranchProtection, CFGuard, CFProtection, CrateType, DebugInfo, FunctionReturn, PAuthKey, PacRet,
 };
+use rustc_session::{PointerAuthSchema, Session};
 use rustc_span::{DUMMY_SP, Span, Spanned, Symbol, sym};
 use rustc_target::spec::{
     Arch, CfgAbi, Env, FramePointer, HasTargetSpec, Os, RelocModel, SmallDataThresholdSupport,
@@ -743,6 +743,29 @@ impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
         );
     }
 
+    pub(crate) fn add_ptrauth_pauthabi_version_and_platform_flags(
+        &self,
+        aarch64_elf_pauthabi_version: u32,
+    ) {
+        // NOTE: This must correspond to llvm's AARCH64_PAUTH_PLATFORM_LLVM_LINUX, as defined in
+        // <llvm_root>/llvm/include/llvm/BinaryFormat/ELF.h.
+        // FIXME (jchlanda) extend possible values once we start supporting other platforms (for
+        // example: AARCH64_PAUTH_PLATFORM_BAREMETAL = 0x1);
+        const AARCH64_PAUTH_PLATFORM_LLVM_LINUX: u32 = 0x10000002;
+        llvm::add_module_flag_u32(
+            self.llmod,
+            llvm::ModuleFlagMergeBehavior::Error,
+            "aarch64-elf-pauthabi-platform",
+            AARCH64_PAUTH_PLATFORM_LLVM_LINUX,
+        );
+        llvm::add_module_flag_u32(
+            self.llmod,
+            llvm::ModuleFlagMergeBehavior::Error,
+            "aarch64-elf-pauthabi-version",
+            aarch64_elf_pauthabi_version,
+        );
+    }
+
     // We do our best here to match what Clang does when compiling Objective-C natively.
     // See Clang's `CGObjCCommonMac::EmitImageInfo`:
     // https://github.com/llvm/llvm-project/blob/llvmorg-20.1.8/clang/lib/CodeGen/CGObjCMac.cpp#L5085
@@ -887,7 +910,11 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         get_fn(self, instance)
     }
 
-    fn get_fn_addr(&self, instance: Instance<'tcx>, pac: Option<PacMetadata>) -> &'ll Value {
+    fn get_fn_addr(
+        &self,
+        instance: Instance<'tcx>,
+        pointer_auth_schema: Option<&PointerAuthSchema>,
+    ) -> &'ll Value {
         // When pointer authentication metadata is provided, `get_fn_addr` will
         // attempt to sign the pointer using LLVM's `ConstPtrAuth` constant
         // expression.
@@ -901,8 +928,8 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         // <https://github.com/rust-lang/rust/issues/152532>, and comment in
         // builder's `ptrauth_operand_bundle`.
         let llfn = get_fn(self, instance);
-        match pac {
-            Some(pac) => common::maybe_sign_fn_ptr(self, instance, llfn, pac),
+        match pointer_auth_schema {
+            Some(schema) => common::maybe_sign_fn_ptr(self, instance, llfn, schema),
             None => llfn,
         }
     }
@@ -954,7 +981,7 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                     ty::List::empty(),
                     DUMMY_SP,
                 ),
-                Some(PacMetadata::default()),
+                tcx.sess.pointer_authentication_functions(),
             ),
             _ => {
                 let name = name.unwrap_or("rust_eh_personality");