| Message ID | 20240621-tracepoint-v3-1-9e44eeea2b85@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Tracepoints and static branch in Rust | expand |
Hi Alice, On Fri, Jun 21, 2024 at 10:35:26AM +0000, Alice Ryhl wrote: > 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 <aliceryhl@google.com> [Add linux-arch, and related arch maintainers Cced] Since inline asms are touched here, please consider copying linux-arch and arch maintainers next time ;-) > --- > rust/kernel/lib.rs | 1 + > rust/kernel/static_key.rs | 143 ++++++++++++++++++++++++++++++++++++++++++++++ > scripts/Makefile.build | 2 +- > 3 files changed, 145 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..9c844fe3e3a3 > --- /dev/null > +++ b/rust/kernel/static_key.rs > @@ -0,0 +1,143 @@ > +// 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, $field), > + ); > + > + break 'my_label false; > + }}; > +} > + For x86_64 and arm64 bits: Acked-by: Boqun Feng <boqun.feng@gmail.com> One thing though, we should split the arch-specific impls into different files, for example: rust/kernel/arch/arm64.rs or rust/arch/arm64.rs. That'll be easier for arch maintainers to watch the Rust changes related to a particular architecture. Another thought is that, could you implement an arch_static_branch!() (instead of _static_key_false!()) and use it for static_key_false!() similar to what we have in C? The benefit is that at least for myself it'll be easier to compare the implementation between C and Rust. Regards, Boqun > +#[doc(hidden)] > +#[macro_export] > +#[cfg(target_arch = "loongarch64")] > +macro_rules! _static_key_false { > + ($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, $field), > + ); > + > + break 'my_label false; > + }}; > +} > + > +#[doc(hidden)] > +#[macro_export] > +#[cfg(target_arch = "riscv64")] > +macro_rules! _static_key_false { > + ($key:path, $keytyp:ty, $field:ident) => {'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} - . > + .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_false! { $key, $keytyp, $field } > + }}; > +} > + > +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 > > -- > 2.45.2.741.gdbec12cfda-goog >
On Tue, Jun 25, 2024 at 6:18 PM Boqun Feng <boqun.feng@gmail.com> wrote: > > Hi Alice, > > On Fri, Jun 21, 2024 at 10:35:26AM +0000, Alice Ryhl wrote: > > 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 <aliceryhl@google.com> > > [Add linux-arch, and related arch maintainers Cced] > > Since inline asms are touched here, please consider copying linux-arch > and arch maintainers next time ;-) Will do. > For x86_64 and arm64 bits: > > Acked-by: Boqun Feng <boqun.feng@gmail.com> > > One thing though, we should split the arch-specific impls into different > files, for example: rust/kernel/arch/arm64.rs or rust/arch/arm64.rs. > That'll be easier for arch maintainers to watch the Rust changes related > to a particular architecture. Is that how you would prefer to name these files? You don't want static_key somewhere in the filename? > Another thought is that, could you implement an arch_static_branch!() > (instead of _static_key_false!()) and use it for static_key_false!() > similar to what we have in C? The benefit is that at least for myself > it'll be easier to compare the implementation between C and Rust. I can try to include that. Alice
On Thu, Jun 27, 2024 at 10:34:39AM +0200, Alice Ryhl wrote: > On Tue, Jun 25, 2024 at 6:18 PM Boqun Feng <boqun.feng@gmail.com> wrote: > > > > Hi Alice, > > > > On Fri, Jun 21, 2024 at 10:35:26AM +0000, Alice Ryhl wrote: > > > 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 <aliceryhl@google.com> > > > > [Add linux-arch, and related arch maintainers Cced] > > > > Since inline asms are touched here, please consider copying linux-arch > > and arch maintainers next time ;-) > > Will do. > > > For x86_64 and arm64 bits: > > > > Acked-by: Boqun Feng <boqun.feng@gmail.com> > > > > One thing though, we should split the arch-specific impls into different > > files, for example: rust/kernel/arch/arm64.rs or rust/arch/arm64.rs. > > That'll be easier for arch maintainers to watch the Rust changes related > > to a particular architecture. > > Is that how you would prefer to name these files? You don't want > static_key somewhere in the filename? > I could have been more explicit. My preference is (for example ARM64) * we have a rust/kernel/arch.rs, where we do: #[cfg(CONFIG_ARM64)] mod arm64::*; #[cfg(CONFIG_ARM64)] pub use arm64::*; * we have a rust/kernel/arch/arm64.rs: pub(crate) mod jump_label; * we have a rust/kernel/arch/arm64/jump_label.rs, where we put ARM64 arch_static_branch() there. (or static_key.rs and arch_static_key_false()). Then linux-arch can watch: rust/kernel/arch.rs rust/kernel/arch/ And ARM64 maintainers can watch: rust/kernel/arch/arm64.rs rust/kernel/arch/arm64 This is similar to how <asm/*.h> are organized today. Does this make sense? Regards, Boqun > > Another thought is that, could you implement an arch_static_branch!() > > (instead of _static_key_false!()) and use it for static_key_false!() > > similar to what we have in C? The benefit is that at least for myself > > it'll be easier to compare the implementation between C and Rust. > > I can try to include that. > > Alice
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..9c844fe3e3a3 --- /dev/null +++ b/rust/kernel/static_key.rs @@ -0,0 +1,143 @@ +// 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, $field), + ); + + break 'my_label false; + }}; +} + +#[doc(hidden)] +#[macro_export] +#[cfg(target_arch = "loongarch64")] +macro_rules! _static_key_false { + ($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, $field), + ); + + break 'my_label false; + }}; +} + +#[doc(hidden)] +#[macro_export] +#[cfg(target_arch = "riscv64")] +macro_rules! _static_key_false { + ($key:path, $keytyp:ty, $field:ident) => {'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} - . + .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_false! { $key, $keytyp, $field } + }}; +} + +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
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 <aliceryhl@google.com> --- rust/kernel/lib.rs | 1 + rust/kernel/static_key.rs | 143 ++++++++++++++++++++++++++++++++++++++++++++++ scripts/Makefile.build | 2 +- 3 files changed, 145 insertions(+), 1 deletion(-)