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a=openpgp-sha256; l=8506; i=aliceryhl@google.com; h=from:subject:message-id; bh=B20XPkbS2BldO1VNXORVIshLvelvNfCPEDgTJEytqJk=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBm+/lyTWXV0qt+2jySV7mW4g92htG/ndvQ8HqpA dk6PB1Bf0yJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZvv5cgAKCRAEWL7uWMY5 RkGpEACtKcH0XvxL+nqPbUO1qDZYBp7bMUnck3VQWyZKLA989Zc7bnXqY74U0cmqeyfj/XoMJ5Z lnQ5jogYpeKqs3goYSkOH+M4p4ej9Ie95XbXHIMRYWpPojVgq4djGHfYMtRJrD3hjvEO6RlaQMc AeL+nbrCeI1NUFAMheXguFI4z5YgMNFrkdJ3LujbqXfax5LKBopJpR9sIf+2zmz5cC56fRIAyop p2Br8NEWvvZd37qk9WAK8Bb8SQTqhS5MslcMU6ATBjPTChXJVV9Zw0Yu9EVkparyOh+lILISo6l nj3W1hFE4wA765Q6mxAlnKubwjV5oWtEyPu5Ju6wnL0gXlHvr+c7DmEA0wnBLV37vuy0Vp/6Kpt hF041c9wo0ehSoZObI95FnGdJsjNLcm3CdNagGhlWLDqT/juXtplimiVk4Yru1uEtsAKIncI0Kh 2vBc9thKTWi4uiKDUgoR80YNDNo/khAorOcLybKN7XOXe6XWuZvSsb/Q9vJwO3Rz6PJjFK1/szN VWquccbjzSPl3/zsb1gR1lEcyEUuJg9/oIAi7qCT9l7ArCrWTOwyeReOGled4NdKqDou3bXF3fL 1CoH3B2NyClyJ50UDrVa4jHNW/AwmSHJp8dqwKeIqLeYIpyIxb72ihi3ukO1m3EOe7JWuBRc626 8ofGkmyjOxUAWFQ== X-Mailer: b4 0.13.0 Message-ID: <20241001-tracepoint-v9-5-1ad3b7d78acb@google.com> Subject: [PATCH v9 5/5] rust: add arch_static_branch 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, Arnd Bergmann , linux-arch@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Sean Christopherson , Uros Bizjak , Catalin Marinas , Will Deacon , Marc Zyngier , Oliver Upton , Mark Rutland , Ryan Roberts , Fuad Tabba , linux-arm-kernel@lists.infradead.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , Anup Patel , Andrew Jones , Alexandre Ghiti , Conor Dooley , Samuel Holland , linux-riscv@lists.infradead.org, Huacai Chen , WANG Xuerui , Bibo Mao , Tiezhu Yang , Andrew Morton , Tianrui Zhao , loongarch@lists.linux.dev, Alice Ryhl Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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. Suggested-by: Peter Zijlstra (Intel) Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda Signed-off-by: Alice Ryhl --- rust/Makefile | 5 ++- rust/kernel/.gitignore | 3 ++ rust/kernel/arch_static_branch_asm.rs.S | 7 ++++ rust/kernel/jump_label.rs | 64 +++++++++++++++++++++++++++++= +++- rust/kernel/lib.rs | 35 ++++++++++++++++++ scripts/Makefile.build | 9 ++++- 6 files changed, 120 insertions(+), 3 deletions(-) diff --git a/rust/Makefile b/rust/Makefile index b5e0a73b78f3..09ea07cc4001 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -36,6 +36,8 @@ always-$(CONFIG_RUST_KERNEL_DOCTESTS) +=3D doctests_kerne= l_generated_kunit.c obj-$(CONFIG_RUST_KERNEL_DOCTESTS) +=3D doctests_kernel_generated.o obj-$(CONFIG_RUST_KERNEL_DOCTESTS) +=3D doctests_kernel_generated_kunit.o =20 +always-$(subst y,$(CONFIG_RUST),$(CONFIG_JUMP_LABEL)) +=3D kernel/arch_sta= tic_branch_asm.rs + # Avoids running `$(RUSTC)` for the sysroot when it may not be available. ifdef CONFIG_RUST =20 @@ -421,7 +423,8 @@ $(obj)/uapi.o: $(src)/uapi/lib.rs \ $(obj)/kernel.o: private rustc_target_flags =3D --extern alloc \ --extern build_error --extern macros --extern bindings --extern uapi $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \ - $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE + $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o \ + $(obj)/kernel/arch_static_branch_asm.rs FORCE +$(call if_changed_rule,rustc_library) =20 endif # CONFIG_RUST diff --git a/rust/kernel/.gitignore b/rust/kernel/.gitignore new file mode 100644 index 000000000000..d082731007c6 --- /dev/null +++ b/rust/kernel/.gitignore @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0 + +/arch_static_branch_asm.rs diff --git a/rust/kernel/arch_static_branch_asm.rs.S b/rust/kernel/arch_sta= tic_branch_asm.rs.S new file mode 100644 index 000000000000..9e373d4f7567 --- /dev/null +++ b/rust/kernel/arch_static_branch_asm.rs.S @@ -0,0 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +// Cut here. + +::kernel::concat_literals!(ARCH_STATIC_BRANCH_ASM("{symb} + {off} + {branc= h}", "{l_yes}")) diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs index 011e1fc1d19a..ccfd20589c21 100644 --- a/rust/kernel/jump_label.rs +++ b/rust/kernel/jump_label.rs @@ -23,7 +23,69 @@ macro_rules! static_key_false { let _key: *const $keytyp =3D ::core::ptr::addr_of!($key); let _key: *const $crate::bindings::static_key =3D ::core::ptr::add= r_of!((*_key).$field); =20 - $crate::bindings::static_key_count(_key.cast_mut()) > 0 + #[cfg(not(CONFIG_JUMP_LABEL))] + { + $crate::bindings::static_key_count(_key.cast_mut()) > 0 + } + + #[cfg(CONFIG_JUMP_LABEL)] + $crate::jump_label::arch_static_branch! { $key, $keytyp, $field, f= alse } }}; } pub use static_key_false; + +/// Assert that the assembly block evaluates to a string literal. +#[cfg(CONFIG_JUMP_LABEL)] +const _: &str =3D include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_sta= tic_branch_asm.rs")); + +#[macro_export] +#[doc(hidden)] +#[cfg(CONFIG_JUMP_LABEL)] +#[cfg(not(CONFIG_HAVE_JUMP_LABEL_HACK))] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) =3D> {'my_label: { + $crate::asm!( + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_br= anch_asm.rs")); + l_yes =3D label { + break 'my_label true; + }, + symb =3D sym $key, + off =3D const ::core::mem::offset_of!($keytyp, $field), + branch =3D const $crate::jump_label::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +#[macro_export] +#[doc(hidden)] +#[cfg(CONFIG_JUMP_LABEL)] +#[cfg(CONFIG_HAVE_JUMP_LABEL_HACK)] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) =3D> {'my_label: { + $crate::asm!( + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_br= anch_asm.rs")); + l_yes =3D label { + break 'my_label true; + }, + symb =3D sym $key, + off =3D const ::core::mem::offset_of!($keytyp, $field), + branch =3D const 2 | $crate::jump_label::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +#[cfg(CONFIG_JUMP_LABEL)] +pub use arch_static_branch; + +/// A helper used by inline assembly to pass a boolean to as a `const` par= ameter. +/// +/// Using this function instead of a cast lets you assert that the input i= s a boolean, and not some +/// other type that can also be cast to an integer. +#[doc(hidden)] +pub const fn bool_to_int(b: bool) -> i32 { + b as i32 +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 77610e19df96..448af0880785 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -148,3 +148,38 @@ macro_rules! container_of { ptr.sub(offset) as *const $type }} } + +/// Helper for `.rs.S` files. +#[doc(hidden)] +#[macro_export] +macro_rules! concat_literals { + ($( $asm:literal )* ) =3D> { + ::core::concat!($($asm),*) + }; +} + +/// Wrapper around `asm!` configured for use in the kernel. +/// +/// Uses a semicolon to avoid parsing ambiguities, even though this does n= ot match native `asm!` +/// syntax. +// For x86, `asm!` uses intel syntax by default, but we want to use at&t s= yntax in the kernel. +#[cfg(target_arch =3D "x86_64")] +#[macro_export] +macro_rules! asm { + ($($asm:expr),* ; $($rest:tt)*) =3D> { + ::core::arch::asm!( $($asm)*, options(att_syntax), $($rest)* ) + }; +} + +/// Wrapper around `asm!` configured for use in the kernel. +/// +/// Uses a semicolon to avoid parsing ambiguities, even though this does n= ot match native `asm!` +/// syntax. +// For non-x86 arches we just pass through to `asm!`. +#[cfg(not(target_arch =3D "x86_64"))] +#[macro_export] +macro_rules! asm { + ($($asm:expr),* ; $($rest:tt)*) =3D> { + ::core::arch::asm!( $($asm)*, $($rest)* ) + }; +} diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 8f423a1faf50..03ee558fcd4d 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -248,12 +248,13 @@ $(obj)/%.lst: $(obj)/%.c FORCE # Compile Rust sources (.rs) # ------------------------------------------------------------------------= --- =20 -rust_allowed_features :=3D new_uninit +rust_allowed_features :=3D asm_const,asm_goto,new_uninit =20 # `--out-dir` is required to avoid temporaries being created by `rustc` in= the # current working directory, which may be not accessible in the out-of-tree # modules case. rust_common_cmd =3D \ + OBJTREE=3D$(abspath $(objtree)) \ RUST_MODFILE=3D$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \ -Zallow-features=3D$(rust_allowed_features) \ -Zcrate-attr=3Dno_std \ @@ -303,6 +304,12 @@ quiet_cmd_rustc_ll_rs =3D $(RUSTC_OR_CLIPPY_QUIET) $(q= uiet_modtag) $@ $(obj)/%.ll: $(obj)/%.rs FORCE +$(call if_changed_dep,rustc_ll_rs) =20 +quiet_cmd_rustc_rs_rs_S =3D RSCPP $(quiet_modtag) $@ + cmd_rustc_rs_rs_S =3D $(CPP) $(c_flags) -xc -C -P $< | sed '1,/^\/\/= Cut here.$$/d' >$@ + +$(obj)/%.rs: $(obj)/%.rs.S FORCE + +$(call if_changed_dep,rustc_rs_rs_S) + # Compile assembler sources (.S) # ------------------------------------------------------------------------= --- =20 --=20 2.46.1.824.gd892dcdcdd-goog