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KCFI: Add KCFI arity indicator support
Adds KCFI arity indicator support to the Rust compiler (see rust-lang#138311, llvm/llvm-project#121070, and https://lore.kernel.org/lkml/CANiq72=3ghFxy8E=AU9p+0imFxKr5iU3sd0hVUXed5BA+KjdNQ@mail.gmail.com/).
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‎compiler/rustc_codegen_llvm/messages.ftl‎

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@@ -56,6 +56,8 @@ codegen_llvm_prepare_thin_lto_module_with_llvm_err = failed to prepare thin LTO
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codegen_llvm_run_passes = failed to run LLVM passes
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codegen_llvm_run_passes_with_llvm_err = failed to run LLVM passes: {$llvm_err}
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codegen_llvm_sanitizer_kcfi_arity_requires_llvm_21_0_0 = `-Zsanitizer-kcfi-arity` requires LLVM 21.0.0 or later.
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codegen_llvm_sanitizer_memtag_requires_mte =
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`-Zsanitizer=memtag` requires `-Ctarget-feature=+mte`
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‎compiler/rustc_codegen_llvm/src/context.rs‎

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@@ -328,6 +328,17 @@ pub(crate) unsafe fn create_module<'ll>(
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}
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}
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// Add "kcfi-arity" module flag if KCFI arity indicator is enabled. (See
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// https://github.com/llvm/llvm-project/pull/117121.)
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if sess.is_sanitizer_kcfi_arity_enabled() && sess.is_sanitizer_kcfi_enabled() {
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// KCFI arity requires LLVM 21.0.0 or later.
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if llvm_version < (21, 0, 0) {
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tcx.dcx().emit_err(crate::errors::SanitizerKcfiArityRequiresLLVM2100);
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}
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llvm::add_module_flag_u32(llmod, llvm::ModuleFlagMergeBehavior::Override, "kcfi-arity", 1);
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}
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// Control Flow Guard is currently only supported by MSVC and LLVM on Windows.
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if sess.target.is_like_msvc
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|| (sess.target.options.os == "windows"

‎compiler/rustc_codegen_llvm/src/errors.rs‎

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@@ -217,3 +217,7 @@ pub(crate) struct MismatchedDataLayout<'a> {
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pub(crate) struct FixedX18InvalidArch<'a> {
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pub arch: &'a str,
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}
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#[derive(Diagnostic)]
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#[diag(codegen_llvm_sanitizer_kcfi_arity_requires_llvm_21_0_0)]
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pub(crate) struct SanitizerKcfiArityRequiresLLVM2100;

‎compiler/rustc_interface/src/tests.rs‎

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@@ -852,6 +852,7 @@ fn test_unstable_options_tracking_hash() {
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tracked!(sanitizer_cfi_generalize_pointers, Some(true));
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tracked!(sanitizer_cfi_normalize_integers, Some(true));
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tracked!(sanitizer_dataflow_abilist, vec![String::from("/rustc/abc")]);
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tracked!(sanitizer_kcfi_arity, Some(true));
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tracked!(sanitizer_memory_track_origins, 2);
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tracked!(sanitizer_recover, SanitizerSet::ADDRESS);
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tracked!(saturating_float_casts, Some(true));

‎compiler/rustc_session/messages.ftl‎

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@@ -94,6 +94,8 @@ session_sanitizer_cfi_requires_lto = `-Zsanitizer=cfi` requires `-Clto` or `-Cli
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session_sanitizer_cfi_requires_single_codegen_unit = `-Zsanitizer=cfi` with `-Clto` requires `-Ccodegen-units=1`
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session_sanitizer_kcfi_arity_requires_kcfi = `-Zsanitizer-kcfi-arity` requires `-Zsanitizer=kcfi`
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session_sanitizer_kcfi_requires_panic_abort = `-Z sanitizer=kcfi` requires `-C panic=abort`
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session_sanitizer_not_supported = {$us} sanitizer is not supported for this target

‎compiler/rustc_session/src/errors.rs‎

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@@ -147,6 +147,10 @@ pub(crate) struct SanitizerCfiGeneralizePointersRequiresCfi;
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#[diag(session_sanitizer_cfi_normalize_integers_requires_cfi)]
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pub(crate) struct SanitizerCfiNormalizeIntegersRequiresCfi;
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#[derive(Diagnostic)]
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#[diag(session_sanitizer_kcfi_arity_requires_kcfi)]
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pub(crate) struct SanitizerKcfiArityRequiresKcfi;
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#[derive(Diagnostic)]
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#[diag(session_sanitizer_kcfi_requires_panic_abort)]
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pub(crate) struct SanitizerKcfiRequiresPanicAbort;

‎compiler/rustc_session/src/options.rs‎

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@@ -2433,6 +2433,8 @@ written to standard error output)"),
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"enable normalizing integer types (default: no)"),
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sanitizer_dataflow_abilist: Vec<String> = (Vec::new(), parse_comma_list, [TRACKED],
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"additional ABI list files that control how shadow parameters are passed (comma separated)"),
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sanitizer_kcfi_arity: Option<bool> = (None, parse_opt_bool, [TRACKED],
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"enable KCFI arity indicator (default: no)"),
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sanitizer_memory_track_origins: usize = (0, parse_sanitizer_memory_track_origins, [TRACKED],
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"enable origins tracking in MemorySanitizer"),
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sanitizer_recover: SanitizerSet = (SanitizerSet::empty(), parse_sanitizers, [TRACKED],

‎compiler/rustc_session/src/session.rs‎

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@@ -382,6 +382,10 @@ impl Session {
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self.opts.unstable_opts.sanitizer_cfi_normalize_integers == Some(true)
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}
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pub fn is_sanitizer_kcfi_arity_enabled(&self) -> bool {
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self.opts.unstable_opts.sanitizer_kcfi_arity == Some(true)
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}
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pub fn is_sanitizer_kcfi_enabled(&self) -> bool {
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self.opts.unstable_opts.sanitizer.contains(SanitizerSet::KCFI)
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}
@@ -1204,6 +1208,11 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
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}
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}
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// KCFI arity indicator requires KCFI.
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if sess.is_sanitizer_kcfi_arity_enabled() && !sess.is_sanitizer_kcfi_enabled() {
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sess.dcx().emit_err(errors::SanitizerKcfiArityRequiresKcfi);
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}
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// LLVM CFI pointer generalization requires CFI or KCFI.
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if sess.is_sanitizer_cfi_generalize_pointers_enabled() {
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if !(sess.is_sanitizer_cfi_enabled() || sess.is_sanitizer_kcfi_enabled()) {

‎tests/assembly/sanitizer/kcfi/emit-arity-indicator.rs‎

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@@ -0,0 +1,61 @@
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// Verifies that KCFI arity indicator is emitted.
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//
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//@ add-core-stubs
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//@ revisions: x86_64
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//@ assembly-output: emit-asm
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//@[x86_64] compile-flags: --target x86_64-unknown-linux-gnu -Cllvm-args=-x86-asm-syntax=intel -Ctarget-feature=-crt-static -Cpanic=abort -Zsanitizer=kcfi -Zsanitizer-kcfi-arity -Copt-level=0
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//@ [x86_64] needs-llvm-components: x86
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//@ min-llvm-version: 21.0.0
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#![crate_type = "lib"]
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pub fn add_one(x: i32) -> i32 {
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// CHECK-LABEL: __cfi__{{.*}}7add_one{{.*}}:
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: mov ecx, 2628068948
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x + 1
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}
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pub fn add_two(x: i32, _y: i32) -> i32 {
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// CHECK-LABEL: __cfi__{{.*}}7add_two{{.*}}:
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: mov edx, 2505940310
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x + 2
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}
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pub fn do_twice(f: fn(i32) -> i32, arg: i32) -> i32 {
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// CHECK-LABEL: __cfi__{{.*}}8do_twice{{.*}}:
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: nop
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// CHECK-NEXT: mov edx, 653723426
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f(arg) + f(arg)
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}

‎tests/codegen/sanitizer/kcfi/add-kcfi-arity-flag.rs‎

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@@ -0,0 +1,18 @@
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// Verifies that "kcfi-arity" module flag is added.
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//
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//@ add-core-stubs
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//@ revisions: x86_64
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//@ [x86_64] compile-flags: --target x86_64-unknown-none
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//@ [x86_64] needs-llvm-components: x86
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//@ compile-flags: -Ctarget-feature=-crt-static -Cpanic=abort -Zsanitizer=kcfi -Zsanitizer-kcfi-arity
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#![feature(no_core, lang_items)]
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#![crate_type = "lib"]
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#![no_core]
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extern crate minicore;
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use minicore::*;
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pub fn foo() {}
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// CHECK: !{{[0-9]+}} = !{i32 4, !"kcfi-arity", i32 1}

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