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From:   Miguel Ojeda <ojeda@kernel.org>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        Alice Ryhl <aliceryhl@google.com>, x86@kernel.org,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
Subject: [PATCH 2/4] x86/rust: support SLS
Date:   Mon, 23 Oct 2023 19:44:46 +0200
Message-ID: <20231023174449.251550-2-ojeda@kernel.org>
In-Reply-To: <20231023174449.251550-1-ojeda@kernel.org>
References: <20231023174449.251550-1-ojeda@kernel.org>
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Support the `SLS` speculation mitigation by enabling the target features
that Clang does.

Without this, `objtool` would complain if enabled for individual object
files (like it is planned in the future), e.g.

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

Signed-off-by: Miguel Ojeda <ojeda@kernel.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 163089ae13ba..7e374369afca 100644
--- a/scripts/generate_rust_target.rs
+++ b/scripts/generate_rust_target.rs
@@ -165,6 +165,14 @@ fn main() {
             features += ",+retpoline-indirect-branches";
             features += ",+retpoline-indirect-calls";
         }
+        if cfg.has("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");
-- 
2.42.0