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Message-ID: <20240802-tracepoint-v5-1-faa164494dcb@google.com>
Date: Fri, 02 Aug 2024 09:31:27 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...nel.org>, Jason Baron <jbaron@...mai.com>,
Ard Biesheuvel <ardb@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...sung.com>
Cc: linux-trace-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>, Sean Christopherson <seanjc@...gle.com>, Uros Bizjak <ubizjak@...il.com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>, Mark Rutland <mark.rutland@....com>,
Ryan Roberts <ryan.roberts@....com>, Fuad Tabba <tabba@...gle.com>,
linux-arm-kernel@...ts.infradead.org,
Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>, Anup Patel <apatel@...tanamicro.com>,
Andrew Jones <ajones@...tanamicro.com>, Alexandre Ghiti <alexghiti@...osinc.com>,
Conor Dooley <conor.dooley@...rochip.com>, Samuel Holland <samuel.holland@...ive.com>,
linux-riscv@...ts.infradead.org, Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>, Bibo Mao <maobibo@...ngson.cn>,
Tiezhu Yang <yangtiezhu@...ngson.cn>, Andrew Morton <akpm@...ux-foundation.org>,
Tianrui Zhao <zhaotianrui@...ngson.cn>, loongarch@...ts.linux.dev,
Alice Ryhl <aliceryhl@...gle.com>, WANG Rui <wangrui@...ngson.cn>
Subject: [PATCH v5 1/2] rust: add static_key_false
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@...yguo.net>
Tested-by: WANG Rui <wangrui@...ngson.cn>
Link: https://lore.kernel.org/rust-for-linux/20240801102804.GQ33588@noisy.programming.kicks-ass.net/ [1]
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
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
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