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 CDA8E2EAB69; Tue, 22 Jul 2025 14:16:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753193779; cv=none; b=B2XrJCH7UFq3LPhtfUDXj9IOmRVaP+YD5ZKn1PSFJYNnvgeBHxb+Iw/QAJSqNeFnNXYH62boKcTND9Hfb9ULmUx+Ix1qV4UFPF8l1dy0tK7GbVUTWyzWLuBLPrbry1t1QsOru4pMqwsZe1v7zejtkpr2vNxbc4kCOwqP1Pce3Vs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753193779; c=relaxed/simple; bh=TSzan+PDCy02PuGG+Crw22/WUiL9v2cJkzvw1Xc2mLI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=VICDnjrJfXgPVPcZP2L82TI0nXLl3fqj61uaK05RPTIeZxLbes44wI7vZX1ViWJyL/4SXsVpF1ihfe1bV4jYFbeXLeOkLHuWQ88Tv9RHo4L5hRqpM4K7xl3xVrCFwLftSAAErsAbATwfk45vb1gnryE+MWbPYJV0Ip43oSFGujM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NxD78bKi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NxD78bKi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D2A9C4CEEB; Tue, 22 Jul 2025 14:16:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1753193779; bh=TSzan+PDCy02PuGG+Crw22/WUiL9v2cJkzvw1Xc2mLI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NxD78bKiC5dtgDCZA66g4isqJwxz/PznrLtX6wWd/JTNSzRg6dOBdE0YRokpPvzXF NMK/BaVd5gtWSt9oNdXd9fgxonebijGEqUa2GbNkPOSEb0GxoXO3UW7av2O7LoqJWE e4QhdUMhrMMzDtSFh6crB+FgPSsXW/3UPnzOChWg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, David Wood , Wesley Wiser , Alice Ryhl , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Miguel Ojeda Subject: [PATCH 6.15 173/187] rust: use `#[used(compiler)]` to fix build and `modpost` with Rust >= 1.89.0 Date: Tue, 22 Jul 2025 15:45:43 +0200 Message-ID: <20250722134352.214605714@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250722134345.761035548@linuxfoundation.org> References: <20250722134345.761035548@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miguel Ojeda commit 7498159226772d66f150dd406be462d75964a366 upstream. Starting with Rust 1.89.0 (expected 2025-08-07), the Rust compiler fails to build the `rusttest` target due to undefined references such as: kernel...-cgu.0:(.text....+0x116): undefined reference to `rust_helper_kunit_get_current_test' Moreover, tooling like `modpost` gets confused: WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpu/drm/nova/nova.o ERROR: modpost: missing MODULE_LICENSE() in drivers/gpu/nova-core/nova_core.o The reason behind both issues is that the Rust compiler will now [1] treat `#[used]` as `#[used(linker)]` instead of `#[used(compiler)]` for our targets. This means that the retain section flag (`R`, `SHF_GNU_RETAIN`) will be used and that they will be marked as `unique` too, with different IDs. In turn, that means we end up with undefined references that did not get discarded in `rusttest` and that multiple `.modinfo` sections are generated, which confuse tooling like `modpost` because they only expect one. Thus start using `#[used(compiler)]` to keep the previous behavior and to be explicit about what we want. Sadly, it is an unstable feature (`used_with_arg`) [2] -- we will talk to upstream Rust about it. The good news is that it has been available for a long time (Rust >= 1.60) [3]. The changes should also be fine for previous Rust versions, since they behave the same way as before [4]. Alternatively, we could use `#[no_mangle]` or `#[export_name = ...]` since those still behave like `#[used(compiler)]`, but of course it is not really what we want to express, and it requires other changes to avoid symbol conflicts. Cc: David Wood Cc: Wesley Wiser Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Link: https://github.com/rust-lang/rust/pull/140872 [1] Link: https://github.com/rust-lang/rust/issues/93798 [2] Link: https://github.com/rust-lang/rust/pull/91504 [3] Link: https://godbolt.org/z/sxzWTMfzW [4] Reviewed-by: Alice Ryhl Acked-by: Björn Roy Baron Link: https://lore.kernel.org/r/20250712160103.1244945-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman --- rust/Makefile | 1 + rust/kernel/firmware.rs | 2 +- rust/kernel/kunit.rs | 2 +- rust/kernel/lib.rs | 2 ++ rust/macros/module.rs | 10 +++++----- scripts/Makefile.build | 2 +- 6 files changed, 11 insertions(+), 8 deletions(-) --- a/rust/Makefile +++ b/rust/Makefile @@ -194,6 +194,7 @@ quiet_cmd_rustdoc_test = RUSTDOC T $< RUST_MODFILE=test.rs \ OBJTREE=$(abspath $(objtree)) \ $(RUSTDOC) --test $(rust_common_flags) \ + -Zcrate-attr='feature(used_with_arg)' \ @$(objtree)/include/generated/rustc_cfg \ $(rustc_target_flags) $(rustdoc_test_target_flags) \ $(rustdoc_test_quiet) \ --- a/rust/kernel/firmware.rs +++ b/rust/kernel/firmware.rs @@ -202,7 +202,7 @@ macro_rules! module_firmware { }; #[link_section = ".modinfo"] - #[used] + #[used(compiler)] static __MODULE_FIRMWARE: [u8; $($builder)*::create(__MODULE_FIRMWARE_PREFIX) .build_length()] = $($builder)*::create(__MODULE_FIRMWARE_PREFIX).build(); }; --- a/rust/kernel/kunit.rs +++ b/rust/kernel/kunit.rs @@ -278,7 +278,7 @@ macro_rules! kunit_unsafe_test_suite { is_init: false, }; - #[used] + #[used(compiler)] #[allow(unused_unsafe)] #[cfg_attr(not(target_os = "macos"), link_section = ".kunit_test_suites")] static mut KUNIT_TEST_SUITE_ENTRY: *const ::kernel::bindings::kunit_suite = --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -26,6 +26,8 @@ #![feature(const_mut_refs)] #![feature(const_ptr_write)] #![feature(const_refs_to_cell)] +// To be determined. +#![feature(used_with_arg)] // Ensure conditional compilation based on the kernel configuration works; // otherwise we may silently break things like initcall handling. --- a/rust/macros/module.rs +++ b/rust/macros/module.rs @@ -57,7 +57,7 @@ impl<'a> ModInfoBuilder<'a> { {cfg} #[doc(hidden)] #[cfg_attr(not(target_os = \"macos\"), link_section = \".modinfo\")] - #[used] + #[used(compiler)] pub static __{module}_{counter}: [u8; {length}] = *{string}; ", cfg = if builtin { @@ -247,7 +247,7 @@ pub(crate) fn module(ts: TokenStream) -> // key or a new section. For the moment, keep it simple. #[cfg(MODULE)] #[doc(hidden)] - #[used] + #[used(compiler)] static __IS_RUST_MODULE: () = (); static mut __MOD: core::mem::MaybeUninit<{type_}> = @@ -271,7 +271,7 @@ pub(crate) fn module(ts: TokenStream) -> #[cfg(MODULE)] #[doc(hidden)] - #[used] + #[used(compiler)] #[link_section = \".init.data\"] static __UNIQUE_ID___addressable_init_module: unsafe extern \"C\" fn() -> i32 = init_module; @@ -291,7 +291,7 @@ pub(crate) fn module(ts: TokenStream) -> #[cfg(MODULE)] #[doc(hidden)] - #[used] + #[used(compiler)] #[link_section = \".exit.data\"] static __UNIQUE_ID___addressable_cleanup_module: extern \"C\" fn() = cleanup_module; @@ -301,7 +301,7 @@ pub(crate) fn module(ts: TokenStream) -> #[cfg(not(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS))] #[doc(hidden)] #[link_section = \"{initcall_section}\"] - #[used] + #[used(compiler)] pub static __{name}_initcall: extern \"C\" fn() -> kernel::ffi::c_int = __{name}_init; #[cfg(not(MODULE))] --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -222,7 +222,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE # Compile Rust sources (.rs) # --------------------------------------------------------------------------- -rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,raw_ref_op +rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,raw_ref_op,used_with_arg # `--out-dir` is required to avoid temporaries being created by `rustc` in the # current working directory, which may be not accessible in the out-of-tree