linux-kernel - [PATCH v2 4/6] x86/rust: support MITIGATION

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Message-ID: <20240724161501.1319115-5-ojeda@kernel.org>
Date: Wed, 24 Jul 2024 18:14:57 +0200
From: Miguel Ojeda <ojeda@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Masahiro Yamada <masahiroy@...nel.org>
Cc: x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	Miguel Ojeda <ojeda@...nel.org>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev
Subject: [PATCH v2 4/6] x86/rust: support MITIGATION_SLS

Support `MITIGATION_SLS` by enabling the target features that Clang does.

Without this, `objtool` would complain if enabled for Rust, e.g.:

    rust/core.o: warning: objtool:
    _R...next_up+0x44: missing int3 after ret

These should be eventually enabled via `-Ctarget-feature` when `rustc`
starts recognizing them (or via a new dedicated flag) [1].

Link: https://github.com/rust-lang/rust/issues/116851 [1]
Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
---
 scripts/generate_rust_target.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs
index 44952f0a3aac..ba1bd455e160 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -173,6 +173,14 @@ fn main() {
             features += ",+retpoline-indirect-branches";
             features += ",+retpoline-indirect-calls";
         }
+        if cfg.has("MITIGATION_SLS") {
+            // The kernel uses `-mharden-sls=all`, which Clang maps to both these target features in
+            // `clang/lib/Driver/ToolChains/Arch/X86.cpp`. These should be eventually enabled via
+            // `-Ctarget-feature` when `rustc` starts recognizing them (or via a new dedicated
+            // flag); see https://github.com/rust-lang/rust/issues/116851.
+            features += ",+harden-sls-ijmp";
+            features += ",+harden-sls-ret";
+        }
         ts.push("features", features);
         ts.push("llvm-target", "x86_64-linux-gnu");
         ts.push("target-pointer-width", "64");
--
2.45.2