From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E606921340; Mon, 23 Oct 2023 17:45:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="q5sZlBXB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 754EBC433C8; Mon, 23 Oct 2023 17:45:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698083125; bh=X2EiXljEqLgjkMvgVksP7BUN5cbAO2JI6oZUqCn5eWA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q5sZlBXBs5Iog9qQoDZ2/bLkWFr3eeiiWVLVSZ+sI7fj7xIIRbHUoWbq2iHyPy76w wc88r56+X9avGXu+OMTWHjzXYfpfBL610QgzkF899uZdDPH7s7n1846Siq42LNgHNH vJ+SgFDeIwPuHFNF4crhAnR5vLxKHOehoGgUTLp6Ja1E7VJiFSt9/iLj5WBEFWolsw OUnXCYwblWnSwgnFRinkG5ce/hAaLYppdnsCtd+OQDe06609TMIIaLOC7MhP13nMhH dQFc2UqAd5c8HVXPZNRrL2nzk4IS30mWZuAOICUKr9QnFaCkWw4YU+IQ30qXUph4r9 t5Sa6AK8jlnMQ== From: Miguel Ojeda To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Peter Zijlstra , Josh Poimboeuf Cc: Miguel Ojeda , Wedson Almeida Filho , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , x86@kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev Subject: [PATCH 3/4] x86/rust: depend on !RETHUNK Date: Mon, 23 Oct 2023 19:44:47 +0200 Message-ID: <20231023174449.251550-3-ojeda@kernel.org> In-Reply-To: <20231023174449.251550-1-ojeda@kernel.org> References: <20231023174449.251550-1-ojeda@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The Rust compiler does not support the equivalent of `-mfunction-return=thunk-extern` yet [1]. Thus, currently, `objtool` warns about it, e.g.: samples/rust/rust_print.o: warning: objtool: _R...init+0xa5c: 'naked' return found in RETHUNK build The support in `rustc` for `-Zfunction-return` has been submitted and is being reviewed [2]. It adds the needed LLVM function attributes and, with it, I got a RETHUNK kernel build with Rust enabled that does not print the `objtool` related warnings, boots in QEMU and can load a kernel loadable module. In any case, until proper/complete support is added to `rustc`, make it a hard restriction until the mitigation is in place. This may have an impact for developers that may not need/care about the mitigation in the Rust side (e.g. Ubuntu offers Rust as a "technology preview" [3]), but given we are getting closer to having the first actual in-tree Rust kernel users, it seems like the right time to disallow it. This should also avoid confusion [4]. Link: https://github.com/rust-lang/rust/issues/116853 [1] Link: https://github.com/rust-lang/rust/pull/116892 [2] Link: https://lore.kernel.org/rust-for-linux/ZSQXqX2%2Flhf5ICZP@gpd/ [3] Link: https://lore.kernel.org/rust-for-linux/CANiq72n6DMeXQrgOzS_+3VdgNYAmpcnneAHJnZERUQhMExg+0A@mail.gmail.com/ [4] Signed-off-by: Miguel Ojeda --- init/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/init/Kconfig b/init/Kconfig index 6d35728b94b2..9452b4102b99 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1889,6 +1889,7 @@ config RUST depends on !GCC_PLUGINS depends on !RANDSTRUCT depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE + depends on !RETHUNK select CONSTRUCTORS help Enables Rust support in the kernel. -- 2.42.0