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Mon, 10 Jun 2024 07:01:48 -0700 (PDT) Date: Mon, 10 Jun 2024 14:01:04 +0000 In-Reply-To: <20240610-tracepoint-v2-0-faebad81b355@google.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240610-tracepoint-v2-0-faebad81b355@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=4510; i=aliceryhl@google.com; h=from:subject:message-id; bh=9vYGSS2BmEd2xDDj2+LOFjdqN6wry32Wd02DytPyAGM=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBmZwdEPykOiap15c/fLpyNtrxN5Tig8vcli+THt 9+Kjoo82q2JAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZmcHRAAKCRAEWL7uWMY5 RlZUEACvE9nXD8ucFeS4gyrBRW8aiQYMALTJ1gxduY1c5sqM8XqcB25c0eZu5m4HDkU9MMyAtfX BPiuO8DHV2wO93rAEKZsGjPU/ocSKwt/LD1YmSEp3xfklG1nT6q9DOzn74sfaRH/+ILuhU6Tg6s BJ31tjZqbOAo2R0n+jMvA5tNFhf4j98gye+pEYcVI+aEzYyVampkt0KzHI3wEYB53cKM6D0QEr3 Nq3xp6IwHcX1bQ05dXpT9MXn48BEmb9yHoNEIjiKahN9o1vqbXD4fWOyLDPDkbaZYx0Dp/JJOW9 gz1K+7w12sKb+yj3Q0A5jLnWiEU/VmerzhYJvoqR5mEpSBP/WGvpob2+d1qJOhAvpJMKg1jvteX p4YlFkMfoPP6FSnfoUPVaOxgfXuseC9QXqLt90fw+Z8A7CeA+CLDgyGLrt9SFj8UXcRSPoA8wi+ g4/jdnVsTekzD4hHWr24ydThH/JdyyyiP5LgQy4ceSTrPbCkPabKJ6cezKzCJRhAXTCCCjIUpP9 5wIyWYSFIRw8xm1+LAwOIt5EAKDunrE8YI6vmqE3fSAsDpd5atJAeINpoW/eKfcw0TSm1+KLquB JOab7zCkOrc+KSH2ge1ekNNNGb2nXLvTHitXnCTkMf7jr6Sk2e18J/lf3Q9XCSwHQXvIamfGBm/ LuGEn3Xmspv2gnA== X-Mailer: b4 0.13-dev-26615 Message-ID: <20240610-tracepoint-v2-1-faebad81b355@google.com> Subject: [PATCH v2 1/2] rust: add static_key_false From: Alice Ryhl To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Josh Poimboeuf , Jason Baron , Ard Biesheuvel , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg Cc: linux-trace-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Alice Ryhl Add just enough support for static key so that we can use it from tracepoints. Tracepoints rely on `static_key_false` even though it is deprecated, so we add the same functionality to Rust. It is not possible to use the existing C implementation of arch_static_branch because it passes the argument `key` to inline assembly as an 'i' parameter, so any attempt to add a C helper for this function will fail to compile because the value of `key` must be known at compile-time. Signed-off-by: Alice Ryhl --- rust/kernel/lib.rs | 1 + rust/kernel/static_key.rs | 87 +++++++++++++++++++++++++++++++++++++++++++++++ scripts/Makefile.build | 2 +- 3 files changed, 89 insertions(+), 1 deletion(-) diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index fbd91a48ff8b..a0be9544996d 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -38,6 +38,7 @@ pub mod prelude; pub mod print; mod static_assert; +pub mod static_key; #[doc(hidden)] pub mod std_vendor; pub mod str; diff --git a/rust/kernel/static_key.rs b/rust/kernel/static_key.rs new file mode 100644 index 000000000000..6c3dbe14c98a --- /dev/null +++ b/rust/kernel/static_key.rs @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Logic for static keys. + +use crate::bindings::*; + +#[doc(hidden)] +#[macro_export] +#[cfg(target_arch = "x86_64")] +macro_rules! _static_key_false { + ($key:path, $keytyp:ty, $field:ident) => {'my_label: { + core::arch::asm!( + r#" + 1: .byte 0x0f,0x1f,0x44,0x00,0x00 + + .pushsection __jump_table, "aw" + .balign 8 + .long 1b - . + .long {0} - . + .quad {1} + {2} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + ); + + break 'my_label false; + }}; +} + +#[doc(hidden)] +#[macro_export] +#[cfg(target_arch = "aarch64")] +macro_rules! _static_key_false { + ($key:path, $keytyp:ty, $field:ident) => {'my_label: { + core::arch::asm!( + r#" + 1: nop + + .pushsection __jump_table, "aw" + .align 3 + .long 1b - ., {0} - . + .quad {1} + {2} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + ); + + break 'my_label false; + }}; +} + +/// Branch based on a static key. +/// +/// Takes three arguments: +/// +/// * `key` - the path to the static variable containing the `static_key`. +/// * `keytyp` - the type of `key`. +/// * `field` - the name of the field of `key` that contains the `static_key`. +#[macro_export] +macro_rules! static_key_false { + // Forward to the real implementation. Separated like this so that we don't have to duplicate + // the documentation. + ($key:path, $keytyp:ty, $field:ident) => {{ + // Assert that `$key` has type `$keytyp` and that `$key.$field` has type `static_key`. + // + // SAFETY: We know that `$key` is a static because otherwise the inline assembly will not + // compile. The raw pointers created in this block are in-bounds of `$key`. + static _TY_ASSERT: () = unsafe { + let key: *const $keytyp = ::core::ptr::addr_of!($key); + let _: *const $crate::bindings::static_key = ::core::ptr::addr_of!((*key).$field); + }; + + $crate::static_key::_static_key_false! { $key, $keytyp, $field } + }}; +} + +pub use {_static_key_false, static_key_false}; diff --git a/scripts/Makefile.build b/scripts/Makefile.build index efacca63c897..60197c1c063f 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -263,7 +263,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE # Compile Rust sources (.rs) # --------------------------------------------------------------------------- -rust_allowed_features := new_uninit +rust_allowed_features := asm_const,asm_goto,new_uninit # `--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