| Message ID | 20240628-tracepoint-v4-1-353d523a9c15@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Tracepoints and static branch in Rust | expand |
Hi Alice On Fri, Jun 28, 2024 at 9:24 PM Alice Ryhl <aliceryhl@google.com> 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> > --- > 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 +- > 8 files changed, 201 insertions(+), 1 deletion(-) > > 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; > + }}; > +} I have tested these patches on LoongArch and it works as expected. Tested-by: WANG Rui <wangrui@loongson.cn> Thanks, -Rui > + > +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 fbd91a48ff8b..fffd4e1dd1c1 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; > mod build_assert; > pub mod error; > pub mod init; > @@ -38,6 +39,7 @@ > 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 > > -- > 2.45.2.803.g4e1b14247a-goog > >
On Fri, 28 Jun 2024 13:23:31 +0000 Alice Ryhl <aliceryhl@google.com> 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> Reviewed-by: Gary Guo <gary@garyguo.net> > --- > 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 +- > 8 files changed, 201 insertions(+), 1 deletion(-)
On Fri, Jun 28, 2024 at 01:23:31PM +0000, Alice Ryhl wrote: > 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 +- > 8 files changed, 201 insertions(+), 1 deletion(-) So I really find the amount of duplicated asm offensive. Is is far too easy for any of this to get out of sync. > 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; > + }}; > +} Note that this uses the forced 5 byte version, and not the dynamic sized one. On top of that it hard-codes the nop5 string :/ Please work harder to not have to duplicate stuff like this. NAK.
On Wed, Jul 31, 2024 at 7:05 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Fri, Jun 28, 2024 at 01:23:31PM +0000, Alice Ryhl wrote: > > > 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 +- > > 8 files changed, 201 insertions(+), 1 deletion(-) > > So I really find the amount of duplicated asm offensive. Is is far too > easy for any of this to get out of sync. > > > 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; > > + }}; > > +} > > Note that this uses the forced 5 byte version, and not the dynamic sized > one. On top of that it hard-codes the nop5 string :/ > > Please work harder to not have to duplicate stuff like this. I really didn't want to duplicate it, but it's very hard to find a performant alternative. Is there any way we could accept duplication only in the cases where an 'i' parameter is used? I don't have the choice of using a Rust helper for 'i' parameters. Perhaps one option could be to put the Rust code inside jump_label.h and have the header file evaluate to either C or Rust depending on the value of some #ifdefs? #ifndef RUST_ASM /* existing C code goes here */ #endif #ifdef RUST_ASM // rust code goes here #endif That way the duplication is all in a single file. It would also avoid the need for duplicating the nop5 string, as the Rust case is still going through the C preprocessor and can use the existing #define. I'm also open to other alternatives. But I don't have infinite resources to drive major language changes. Alice
On Wed, Jul 31, 2024 at 11:34:13PM +0200, Alice Ryhl wrote: > > Please work harder to not have to duplicate stuff like this. > > I really didn't want to duplicate it, but it's very hard to find a > performant alternative. Is there any way we could accept duplication > only in the cases where an 'i' parameter is used? I don't have the > choice of using a Rust helper for 'i' parameters. > > Perhaps one option could be to put the Rust code inside jump_label.h > and have the header file evaluate to either C or Rust depending on the > value of some #ifdefs? > > #ifndef RUST_ASM > /* existing C code goes here */ > #endif > #ifdef RUST_ASM > // rust code goes here > #endif > > That way the duplication is all in a single file. It would also avoid > the need for duplicating the nop5 string, as the Rust case is still > going through the C preprocessor and can use the existing #define. I suppose that is slightly better, but ideally you generate the whole of the Rust thing from the C version. After all, Clang can already parse this. That said, with the below patch, I think you should be able to reuse the JUMP_TABLE_ENTRY macro like: JUMP_TABLE_ENTRY({0}, {1}, {2} + {3}) > I'm also open to other alternatives. But I don't have infinite > resources to drive major language changes. Yes, well, you all picked this terrible language full well knowing it hated C/C++ and had not a single effort put into integration with existing code bases. I find it very hard to care for the problems you've created for yourself. --- diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index cbbef32517f0..6cff7bf5e779 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -12,12 +12,12 @@ #include <linux/stringify.h> #include <linux/types.h> -#define JUMP_TABLE_ENTRY \ - ".pushsection __jump_table, \"aw\" \n\t" \ - _ASM_ALIGN "\n\t" \ - ".long 1b - . \n\t" \ - ".long %l[l_yes] - . \n\t" \ - _ASM_PTR "%c0 + %c1 - .\n\t" \ +#define JUMP_TABLE_ENTRY(l_yes, key, branch) \ + ".pushsection __jump_table, \"aw\" \n\t" \ + _ASM_ALIGN "\n\t" \ + ".long 1b - . \n\t" \ + ".long " __stringify(l_yes) "- . \n\t" \ + _ASM_PTR " " __stringify(key) " + " __stringify(branch) " - . \n\t" \ ".popsection \n\t" #ifdef CONFIG_HAVE_JUMP_LABEL_HACK @@ -26,7 +26,7 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran { asm goto("1:" "jmp %l[l_yes] # objtool NOPs this \n\t" - JUMP_TABLE_ENTRY + JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1) : : "i" (key), "i" (2 | branch) : : l_yes); return false; @@ -40,7 +40,7 @@ static __always_inline bool arch_static_branch(struct static_key * const key, co { asm goto("1:" ".byte " __stringify(BYTES_NOP5) "\n\t" - JUMP_TABLE_ENTRY + JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1) : : "i" (key), "i" (branch) : : l_yes); return false; @@ -54,7 +54,7 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke { asm goto("1:" "jmp %l[l_yes]\n\t" - JUMP_TABLE_ENTRY + JUMP_TABLE_ENTRY(%[l_yes], %c0, %c1) : : "i" (key), "i" (branch) : : l_yes); return false;
On Thu, Aug 1, 2024 at 12:28 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Wed, Jul 31, 2024 at 11:34:13PM +0200, Alice Ryhl wrote: > > > > Please work harder to not have to duplicate stuff like this. > > > > I really didn't want to duplicate it, but it's very hard to find a > > performant alternative. Is there any way we could accept duplication > > only in the cases where an 'i' parameter is used? I don't have the > > choice of using a Rust helper for 'i' parameters. > > > > Perhaps one option could be to put the Rust code inside jump_label.h > > and have the header file evaluate to either C or Rust depending on the > > value of some #ifdefs? > > > > #ifndef RUST_ASM > > /* existing C code goes here */ > > #endif > > #ifdef RUST_ASM > > // rust code goes here > > #endif > > > > That way the duplication is all in a single file. It would also avoid > > the need for duplicating the nop5 string, as the Rust case is still > > going through the C preprocessor and can use the existing #define. > > I suppose that is slightly better, but ideally you generate the whole of > the Rust thing from the C version. After all, Clang can already parse > this. > > That said, with the below patch, I think you should be able to reuse the > JUMP_TABLE_ENTRY macro like: > > JUMP_TABLE_ENTRY({0}, {1}, {2} + {3}) Yeah, I think this can work. I will submit a follow-up patch that removes the duplication soon. Alice
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 fbd91a48ff8b..fffd4e1dd1c1 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; mod build_assert; pub mod error; pub mod init; @@ -38,6 +39,7 @@ 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
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/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 +- 8 files changed, 201 insertions(+), 1 deletion(-)