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

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Message-ID: <20240724204223.114a1a73.gary@garyguo.net>
Date: Wed, 24 Jul 2024 20:42:23 +0100
From: Gary Guo <gary@...yguo.net>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: 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>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Nathan Chancellor
 <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Wedson Almeida
 Filho <wedsonaf@...il.com>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng
 <boqun.feng@...il.com>, 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: Re: [PATCH v2 4/6] x86/rust: support MITIGATION_SLS

On Wed, 24 Jul 2024 18:14:57 +0200
Miguel Ojeda <ojeda@...nel.org> wrote:

> 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>

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
>  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