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169484ab66
To allow the Rust implementation of static_key_false to use runtime code patching instead of the generic implementation, pull in the relevant inline assembly from the jump_label.h header by running the C preprocessor on a .rs.S file. Build rules are added for .rs.S files. Since the relevant inline asm has been adjusted to export the inline asm via the ARCH_STATIC_BRANCH_ASM macro in a consistent way, the Rust side does not need architecture specific code to pull in the asm. It is not possible to use the existing C implementation of arch_static_branch via a Rust helper because it passes the argument `key` to inline assembly as an 'i' parameter. 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. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Josh Poimboeuf <jpoimboe@kernel.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Alex Gaynor <alex.gaynor@gmail.com> Cc: Wedson Almeida Filho <wedsonaf@gmail.com> Cc: Gary Guo <gary@garyguo.net> Cc: " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " <bjorn3_gh@protonmail.com> Cc: Benno Lossin <benno.lossin@proton.me> Cc: Andreas Hindborg <a.hindborg@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oliver.upton@linux.dev> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Fuad Tabba <tabba@google.com> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Anup Patel <apatel@ventanamicro.com> Cc: Andrew Jones <ajones@ventanamicro.com> Cc: Alexandre Ghiti <alexghiti@rivosinc.com> Cc: Conor Dooley <conor.dooley@microchip.com> Cc: Samuel Holland <samuel.holland@sifive.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Bibo Mao <maobibo@loongson.cn> Cc: Tiezhu Yang <yangtiezhu@loongson.cn> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Tianrui Zhao <zhaotianrui@loongson.cn> Link: https://lore.kernel.org/20241030-tracepoint-v12-5-eec7f0f8ad22@google.com Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Co-developed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
74 lines
2.2 KiB
Rust
74 lines
2.2 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2024 Google LLC.
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//! Logic for static keys.
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//!
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//! C header: [`include/linux/jump_label.h`](srctree/include/linux/jump_label.h).
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/// Branch based on a static key.
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///
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/// Takes three arguments:
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///
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/// * `key` - the path to the static variable containing the `static_key`.
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/// * `keytyp` - the type of `key`.
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/// * `field` - the name of the field of `key` that contains the `static_key`.
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///
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/// # Safety
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///
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/// The macro must be used with a real static key defined by C.
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#[macro_export]
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macro_rules! static_branch_unlikely {
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($key:path, $keytyp:ty, $field:ident) => {{
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let _key: *const $keytyp = ::core::ptr::addr_of!($key);
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let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field);
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let _key: *const $crate::bindings::static_key = _key.cast();
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#[cfg(not(CONFIG_JUMP_LABEL))]
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{
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$crate::bindings::static_key_count(_key) > 0
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}
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#[cfg(CONFIG_JUMP_LABEL)]
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$crate::jump_label::arch_static_branch! { $key, $keytyp, $field, false }
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}};
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}
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pub use static_branch_unlikely;
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/// Assert that the assembly block evaluates to a string literal.
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#[cfg(CONFIG_JUMP_LABEL)]
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const _: &str = include!(concat!(
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env!("OBJTREE"),
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"/rust/kernel/arch_static_branch_asm.rs"
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));
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#[macro_export]
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#[doc(hidden)]
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#[cfg(CONFIG_JUMP_LABEL)]
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macro_rules! arch_static_branch {
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($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: {
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$crate::asm!(
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include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs"));
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l_yes = label {
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break 'my_label true;
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},
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symb = sym $key,
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off = const ::core::mem::offset_of!($keytyp, $field),
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branch = const $crate::jump_label::bool_to_int($branch),
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);
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break 'my_label false;
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}};
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}
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#[cfg(CONFIG_JUMP_LABEL)]
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pub use arch_static_branch;
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/// A helper used by inline assembly to pass a boolean to as a `const` parameter.
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///
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/// Using this function instead of a cast lets you assert that the input is a boolean, and not some
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/// other type that can also be cast to an integer.
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#[doc(hidden)]
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pub const fn bool_to_int(b: bool) -> i32 {
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b as i32
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}
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