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. One disadvantage of this patch is that it introduces a fair amount of duplicated inline assembly. However, this is a limited and temporary situation: 1. Most inline assembly has no reason to be duplicated like this. It is only needed here due to the use of 'i' parameters. 2. Alice will submit a patch along the lines of [1] that removes the duplication. This will happen as a follow-up to this patch series. Comments are added to the C side as a reminder to change the asm on the Rust side in case the C side is changed. For simplicity, the x86 asm uses the forced 5 byte version. This will be fixed together with the upcoming removal of the duplication. Reviewed-by: Gary Guo <gary@xxxxxxxxxxx> Tested-by: WANG Rui <wangrui@xxxxxxxxxxx> Link: https://lore.kernel.org/rust-for-linux/20240801102804.GQ33588@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ [1] Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> --- arch/arm64/include/asm/jump_label.h | 1 + arch/loongarch/include/asm/jump_label.h | 1 + arch/riscv/include/asm/jump_label.h | 1 + arch/x86/include/asm/jump_label.h | 1 + rust/kernel/arch/arm64/jump_label.rs | 34 ++++++++++++++++++++++++++++ rust/kernel/arch/loongarch/jump_label.rs | 35 +++++++++++++++++++++++++++++ rust/kernel/arch/mod.rs | 24 ++++++++++++++++++++ rust/kernel/arch/riscv/jump_label.rs | 38 ++++++++++++++++++++++++++++++++ rust/kernel/arch/x86/jump_label.rs | 35 +++++++++++++++++++++++++++++ rust/kernel/lib.rs | 2 ++ rust/kernel/static_key.rs | 32 +++++++++++++++++++++++++++ scripts/Makefile.build | 2 +- 12 files changed, 205 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/jump_label.h b/arch/arm64/include/asm/jump_label.h index 4e753908b801..56c106669f99 100644 --- a/arch/arm64/include/asm/jump_label.h +++ b/arch/arm64/include/asm/jump_label.h @@ -15,6 +15,7 @@ #define JUMP_LABEL_NOP_SIZE AARCH64_INSN_SIZE +/* Changes to this asm must be reflected in `rust/kernel/arch/arm64/jump_label.rs` */ #define JUMP_TABLE_ENTRY(key, label) \ ".pushsection __jump_table, \"aw\"\n\t" \ ".align 3\n\t" \ diff --git a/arch/loongarch/include/asm/jump_label.h b/arch/loongarch/include/asm/jump_label.h index 29acfe3de3fa..3bdf0d834e8c 100644 --- a/arch/loongarch/include/asm/jump_label.h +++ b/arch/loongarch/include/asm/jump_label.h @@ -13,6 +13,7 @@ #define JUMP_LABEL_NOP_SIZE 4 +/* Changes to this asm must be reflected in `rust/kernel/arch/loongarch/jump_label.rs` */ #define JUMP_TABLE_ENTRY \ ".pushsection __jump_table, \"aw\" \n\t" \ ".align 3 \n\t" \ diff --git a/arch/riscv/include/asm/jump_label.h b/arch/riscv/include/asm/jump_label.h index 1c768d02bd0c..8ed63f588243 100644 --- a/arch/riscv/include/asm/jump_label.h +++ b/arch/riscv/include/asm/jump_label.h @@ -16,6 +16,7 @@ #define JUMP_LABEL_NOP_SIZE 4 +/* Changes to this asm must be reflected in `rust/kernel/arch/riscv/jump_label.rs` */ static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch) { diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index cbbef32517f0..687fff131afe 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -12,6 +12,7 @@ #include <linux/stringify.h> #include <linux/types.h> +/* Changes to this asm must be reflected in `rust/kernel/arch/x86/jump_label.rs` */ #define JUMP_TABLE_ENTRY \ ".pushsection __jump_table, \"aw\" \n\t" \ _ASM_ALIGN "\n\t" \ diff --git a/rust/kernel/arch/arm64/jump_label.rs b/rust/kernel/arch/arm64/jump_label.rs new file mode 100644 index 000000000000..5eede2245718 --- /dev/null +++ b/rust/kernel/arch/arm64/jump_label.rs @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Arm64 Rust implementation of jump_label.h + +/// arm64 implementation of arch_static_branch +#[macro_export] +#[cfg(target_arch = "aarch64")] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: { + core::arch::asm!( + r#" + 1: nop + + .pushsection __jump_table, "aw" + .align 3 + .long 1b - ., {0} - . + .quad {1} + {2} + {3} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + const $crate::arch::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +pub use arch_static_branch; diff --git a/rust/kernel/arch/loongarch/jump_label.rs b/rust/kernel/arch/loongarch/jump_label.rs new file mode 100644 index 000000000000..8d31318aeb11 --- /dev/null +++ b/rust/kernel/arch/loongarch/jump_label.rs @@ -0,0 +1,35 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Loongarch Rust implementation of jump_label.h + +/// loongarch implementation of arch_static_branch +#[doc(hidden)] +#[macro_export] +#[cfg(target_arch = "loongarch64")] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: { + core::arch::asm!( + r#" + 1: nop + + .pushsection __jump_table, "aw" + .align 3 + .long 1b - ., {0} - . + .quad {1} + {2} + {3} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + const $crate::arch::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +pub use arch_static_branch; diff --git a/rust/kernel/arch/mod.rs b/rust/kernel/arch/mod.rs new file mode 100644 index 000000000000..14271d2530e9 --- /dev/null +++ b/rust/kernel/arch/mod.rs @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Architecture specific code. + +#[cfg_attr(target_arch = "aarch64", path = "arm64")] +#[cfg_attr(target_arch = "x86_64", path = "x86")] +#[cfg_attr(target_arch = "loongarch64", path = "loongarch")] +#[cfg_attr(target_arch = "riscv64", path = "riscv")] +mod inner { + pub mod jump_label; +} + +pub use self::inner::*; + +/// A helper used by inline assembly to pass a boolean to as a `const` parameter. +/// +/// Using this function instead of a cast lets you assert that the input is a boolean, rather than +/// some other type that can be cast to an integer. +#[doc(hidden)] +pub const fn bool_to_int(b: bool) -> i32 { + b as i32 +} diff --git a/rust/kernel/arch/riscv/jump_label.rs b/rust/kernel/arch/riscv/jump_label.rs new file mode 100644 index 000000000000..2672e0c6f033 --- /dev/null +++ b/rust/kernel/arch/riscv/jump_label.rs @@ -0,0 +1,38 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! RiscV Rust implementation of jump_label.h + +/// riscv implementation of arch_static_branch +#[macro_export] +#[cfg(target_arch = "riscv64")] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: { + core::arch::asm!( + r#" + .align 2 + .option push + .option norelax + .option norvc + 1: nop + .option pop + .pushsection __jump_table, "aw" + .align 3 + .long 1b - ., {0} - . + .dword {1} + {2} + {3} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + const $crate::arch::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +pub use arch_static_branch; diff --git a/rust/kernel/arch/x86/jump_label.rs b/rust/kernel/arch/x86/jump_label.rs new file mode 100644 index 000000000000..383bed273c50 --- /dev/null +++ b/rust/kernel/arch/x86/jump_label.rs @@ -0,0 +1,35 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! X86 Rust implementation of jump_label.h + +/// x86 implementation of arch_static_branch +#[macro_export] +#[cfg(target_arch = "x86_64")] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'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} + {3} - . + .popsection + "#, + label { + break 'my_label true; + }, + sym $key, + const ::core::mem::offset_of!($keytyp, $field), + const $crate::arch::bool_to_int($branch), + ); + + break 'my_label false; + }}; +} + +pub use arch_static_branch; diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 274bdc1b0a82..da1f69868d0d 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -27,6 +27,7 @@ extern crate self as kernel; pub mod alloc; +pub mod arch; #[cfg(CONFIG_BLOCK)] pub mod block; mod build_assert; @@ -44,6 +45,7 @@ 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..32cf027ef091 --- /dev/null +++ b/rust/kernel/static_key.rs @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2024 Google LLC. + +//! Logic for static keys. + +use crate::bindings::*; + +/// 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 { + ($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::arch::jump_label::arch_static_branch! { $key, $keytyp, $field, false } + }}; +} + +pub use 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 -- 2.46.0.rc2.264.g509ed76dc8-goog
