| Message ID | 20241015-tracepoint-v11-5-cceb65820089@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Steven Rostedt |
| Headers | show |
| Series | Tracepoints and static branch in Rust | expand |
On Tue, Oct 15, 2024 at 01:14:59PM +0000, Alice Ryhl wrote: > 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) <peterz@infradead.org> > Co-developed-by: Miguel Ojeda <ojeda@kernel.org> > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > --- > rust/Makefile | 6 +++++ > rust/kernel/.gitignore | 3 +++ > rust/kernel/arch_static_branch_asm.rs.S | 7 +++++ > rust/kernel/jump_label.rs | 46 ++++++++++++++++++++++++++++++++- > rust/kernel/lib.rs | 35 +++++++++++++++++++++++++ > scripts/Makefile.build | 9 ++++++- > 6 files changed, 104 insertions(+), 2 deletions(-) > > diff --git a/rust/Makefile b/rust/Makefile > index b5e0a73b78f3..c532f48b79de 100644 > --- a/rust/Makefile > +++ b/rust/Makefile > @@ -36,6 +36,8 @@ always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c > obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.o > obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o > > +always-$(subst y,$(CONFIG_RUST),$(CONFIG_JUMP_LABEL)) += kernel/arch_static_branch_asm.rs > + > # Avoids running `$(RUSTC)` for the sysroot when it may not be available. > ifdef CONFIG_RUST > > @@ -424,4 +426,8 @@ $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \ > $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE > +$(call if_changed_rule,rustc_library) > > +ifneq ($(CONFIG_JUMP_LABEL),) > +$(obj)/kernel.o: $(obj)/kernel/arch_static_branch_asm.rs > +endif > + > 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_static_branch_asm.rs.S > new file mode 100644 > index 000000000000..2afb638708db > --- /dev/null > +++ b/rust/kernel/arch_static_branch_asm.rs.S > @@ -0,0 +1,7 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > + > +#include <linux/jump_label.h> > + > +// Cut here. > + > +::kernel::concat_literals!(ARCH_STATIC_BRANCH_ASM("{symb} + {off} + {branch}", "{l_yes}")) > diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs > index 4b7655b2a022..2f2df03a3275 100644 > --- a/rust/kernel/jump_label.rs > +++ b/rust/kernel/jump_label.rs > @@ -24,7 +24,51 @@ macro_rules! static_branch_unlikely { > let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field); > let _key: *const $crate::bindings::static_key = _key.cast(); > > - $crate::bindings::static_key_count(_key.cast_mut()) > 0 > + #[cfg(not(CONFIG_JUMP_LABEL))] > + { > + $crate::bindings::static_key_count(_key) > 0 > + } > + > + #[cfg(CONFIG_JUMP_LABEL)] > + $crate::jump_label::arch_static_branch! { $key, $keytyp, $field, false } > }}; > } > pub use static_branch_unlikely; > + > +/// Assert that the assembly block evaluates to a string literal. > +#[cfg(CONFIG_JUMP_LABEL)] > +const _: &str = include!(concat!( > + env!("OBJTREE"), > + "/rust/kernel/arch_static_branch_asm.rs" > +)); > + > +#[macro_export] > +#[doc(hidden)] > +#[cfg(CONFIG_JUMP_LABEL)] > +macro_rules! arch_static_branch { > + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: { > + $crate::asm!( > + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs")); > + l_yes = label { > + break 'my_label true; > + }, > + symb = sym $key, > + off = const ::core::mem::offset_of!($keytyp, $field), > + branch = const $crate::jump_label::bool_to_int($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` parameter. > +/// > +/// Using this function instead of a cast lets you assert that the input is 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 55f81f49024e..c0ae9ddd9468 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -148,3 +148,38 @@ macro_rules! container_of { > ptr.sub(offset) as *const $type > }} > } > + > +/// Helper for `.rs.S` files. > +#[doc(hidden)] > +#[macro_export] > +macro_rules! concat_literals { > + ($( $asm:literal )* ) => { > + ::core::concat!($($asm),*) > + }; > +} > + > +/// Wrapper around `asm!` configured for use in the kernel. > +/// > +/// Uses a semicolon to avoid parsing ambiguities, even though this does not match native `asm!` > +/// syntax. > +// For x86, `asm!` uses intel syntax by default, but we want to use at&t syntax in the kernel. > +#[cfg(target_arch = "x86_64")] This should be: #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] for future proofing and um (usermode linux) support. > +#[macro_export] > +macro_rules! asm { > + ($($asm:expr),* ; $($rest:tt)*) => { > + ::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 not match native `asm!` > +/// syntax. > +// For non-x86 arches we just pass through to `asm!`. > +#[cfg(not(target_arch = "x86_64"))] Ditto. With these fixed, feel free to add: Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Regards, Boqun > +#[macro_export] > +macro_rules! asm { > + ($($asm:expr),* ; $($rest:tt)*) => { > + ::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: $(obj)/%.c FORCE > # Compile Rust sources (.rs) > # --------------------------------------------------------------------------- > > -rust_allowed_features := new_uninit > +rust_allowed_features := asm_const,asm_goto,new_uninit > > # `--out-dir` is required to avoid temporaries being created by `rustc` in the > # current working directory, which may be not accessible in the out-of-tree > # modules case. > rust_common_cmd = \ > + OBJTREE=$(abspath $(objtree)) \ > RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \ > -Zallow-features=$(rust_allowed_features) \ > -Zcrate-attr=no_std \ > @@ -303,6 +304,12 @@ quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ > $(obj)/%.ll: $(obj)/%.rs FORCE > +$(call if_changed_dep,rustc_ll_rs) > > +quiet_cmd_rustc_rs_rs_S = RSCPP $(quiet_modtag) $@ > + cmd_rustc_rs_rs_S = $(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) > # --------------------------------------------------------------------------- > > > -- > 2.47.0.rc1.288.g06298d1525-goog >
diff --git a/rust/Makefile b/rust/Makefile index b5e0a73b78f3..c532f48b79de 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -36,6 +36,8 @@ always-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.c obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated.o obj-$(CONFIG_RUST_KERNEL_DOCTESTS) += doctests_kernel_generated_kunit.o +always-$(subst y,$(CONFIG_RUST),$(CONFIG_JUMP_LABEL)) += kernel/arch_static_branch_asm.rs + # Avoids running `$(RUSTC)` for the sysroot when it may not be available. ifdef CONFIG_RUST @@ -424,4 +426,8 @@ $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \ $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE +$(call if_changed_rule,rustc_library) +ifneq ($(CONFIG_JUMP_LABEL),) +$(obj)/kernel.o: $(obj)/kernel/arch_static_branch_asm.rs +endif + 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_static_branch_asm.rs.S new file mode 100644 index 000000000000..2afb638708db --- /dev/null +++ b/rust/kernel/arch_static_branch_asm.rs.S @@ -0,0 +1,7 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include <linux/jump_label.h> + +// Cut here. + +::kernel::concat_literals!(ARCH_STATIC_BRANCH_ASM("{symb} + {off} + {branch}", "{l_yes}")) diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs index 4b7655b2a022..2f2df03a3275 100644 --- a/rust/kernel/jump_label.rs +++ b/rust/kernel/jump_label.rs @@ -24,7 +24,51 @@ macro_rules! static_branch_unlikely { let _key: *const $crate::bindings::static_key_false = ::core::ptr::addr_of!((*_key).$field); let _key: *const $crate::bindings::static_key = _key.cast(); - $crate::bindings::static_key_count(_key.cast_mut()) > 0 + #[cfg(not(CONFIG_JUMP_LABEL))] + { + $crate::bindings::static_key_count(_key) > 0 + } + + #[cfg(CONFIG_JUMP_LABEL)] + $crate::jump_label::arch_static_branch! { $key, $keytyp, $field, false } }}; } pub use static_branch_unlikely; + +/// Assert that the assembly block evaluates to a string literal. +#[cfg(CONFIG_JUMP_LABEL)] +const _: &str = include!(concat!( + env!("OBJTREE"), + "/rust/kernel/arch_static_branch_asm.rs" +)); + +#[macro_export] +#[doc(hidden)] +#[cfg(CONFIG_JUMP_LABEL)] +macro_rules! arch_static_branch { + ($key:path, $keytyp:ty, $field:ident, $branch:expr) => {'my_label: { + $crate::asm!( + include!(concat!(env!("OBJTREE"), "/rust/kernel/arch_static_branch_asm.rs")); + l_yes = label { + break 'my_label true; + }, + symb = sym $key, + off = const ::core::mem::offset_of!($keytyp, $field), + branch = const $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` parameter. +/// +/// Using this function instead of a cast lets you assert that the input is 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 55f81f49024e..c0ae9ddd9468 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 )* ) => { + ::core::concat!($($asm),*) + }; +} + +/// Wrapper around `asm!` configured for use in the kernel. +/// +/// Uses a semicolon to avoid parsing ambiguities, even though this does not match native `asm!` +/// syntax. +// For x86, `asm!` uses intel syntax by default, but we want to use at&t syntax in the kernel. +#[cfg(target_arch = "x86_64")] +#[macro_export] +macro_rules! asm { + ($($asm:expr),* ; $($rest:tt)*) => { + ::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 not match native `asm!` +/// syntax. +// For non-x86 arches we just pass through to `asm!`. +#[cfg(not(target_arch = "x86_64"))] +#[macro_export] +macro_rules! asm { + ($($asm:expr),* ; $($rest:tt)*) => { + ::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) # --------------------------------------------------------------------------- -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 # modules case. rust_common_cmd = \ + OBJTREE=$(abspath $(objtree)) \ RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \ -Zallow-features=$(rust_allowed_features) \ -Zcrate-attr=no_std \ @@ -303,6 +304,12 @@ quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@ $(obj)/%.ll: $(obj)/%.rs FORCE +$(call if_changed_dep,rustc_ll_rs) +quiet_cmd_rustc_rs_rs_S = RSCPP $(quiet_modtag) $@ + cmd_rustc_rs_rs_S = $(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) # ---------------------------------------------------------------------------