Commit ad37bcd9 authored by Alice Ryhl's avatar Alice Ryhl Committed by Steven Rostedt (Google)
Browse files

rust: add tracepoint support 

Make it possible to have Rust code call into tracepoints defined by C
code. It is still required that the tracepoint is declared in a C
header, and that this header is included in the input to bindgen.

Instead of calling __DO_TRACE directly, the exported rust_do_trace_
function calls an inline helper function. This is because the `cond`
argument does not exist at the callsite of DEFINE_RUST_DO_TRACE.

__DECLARE_TRACE always emits an inline static and an extern declaration
that is only used when CREATE_RUST_TRACE_POINTS is set. These should not
end up in the final binary so it is not a problem that they sometimes
are emitted without a user.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Cc: " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " <bjorn3_gh@protonmail.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Fuad Tabba <tabba@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Anup Patel <apatel@ventanamicro.com>
Cc: Andrew Jones <ajones@ventanamicro.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Conor Dooley <conor.dooley@microchip.com>
Cc: Samuel Holland <samuel.holland@sifive.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Bibo Mao <maobibo@loongson.cn>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tianrui Zhao <zhaotianrui@loongson.cn>
Link: https://lore.kernel.org/20241030-tracepoint-v12-2-eec7f0f8ad22@google.com


Reviewed-by: default avatarCarlos Llamas <cmllamas@google.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 6e59bcc9

include/linux/tracepoint.h

+27 −1
Original line number Diff line number Diff line
@@ -225,6 +225,18 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
			preempt_enable_notrace();			\

	} while (0)



/*

 * Declare an exported function that Rust code can call to trigger this

 * tracepoint. This function does not include the static branch; that is done

 * in Rust to avoid a function call when the tracepoint is disabled.

 */

#define DEFINE_RUST_DO_TRACE(name, proto, args)

#define __DEFINE_RUST_DO_TRACE(name, proto, args)			\

	notrace void rust_do_trace_##name(proto)			\

	{								\

		__rust_do_trace_##name(args);				\

	}



/*

 * Make sure the alignment of the structure in the __tracepoints section will

 * not add unwanted padding between the beginning of the section and the
@@ -240,6 +252,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
	extern int __traceiter_##name(data_proto);			\

	DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name);	\

	extern struct tracepoint __tracepoint_##name;			\

	extern void rust_do_trace_##name(proto);			\

	static inline int						\

	register_trace_##name(void (*probe)(data_proto), void *data)	\

	{								\
@@ -271,6 +284,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 


#define __DECLARE_TRACE(name, proto, args, cond, data_proto)		\

	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \

	static inline void __rust_do_trace_##name(proto)		\

	{								\

		__DO_TRACE(name,					\

			TP_ARGS(args),					\

			TP_CONDITION(cond), 0);				\

	}								\

	static inline void trace_##name(proto)				\

	{								\

		if (static_branch_unlikely(&__tracepoint_##name.key))	\
@@ -285,6 +304,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 


#define __DECLARE_TRACE_SYSCALL(name, proto, args, cond, data_proto)	\

	__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \

	static inline void __rust_do_trace_##name(proto)		\

	{								\

		__DO_TRACE(name,					\

			TP_ARGS(args),					\

			TP_CONDITION(cond), 1);				\

	}								\

	static inline void trace_##name(proto)				\

	{								\

		if (static_branch_unlikely(&__tracepoint_##name.key))	\
@@ -339,7 +364,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) 
	void __probestub_##_name(void *__data, proto)			\

	{								\

	}								\

	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);

	DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);	\

	DEFINE_RUST_DO_TRACE(_name, TP_PROTO(proto), TP_ARGS(args))



#define DEFINE_TRACE(name, proto, args)		\

	DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));

include/trace/define_trace.h

+12 −0
Original line number Diff line number Diff line
@@ -76,6 +76,13 @@ 
#define DECLARE_TRACE(name, proto, args)	\

	DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))



/* If requested, create helpers for calling these tracepoints from Rust. */

#ifdef CREATE_RUST_TRACE_POINTS

#undef DEFINE_RUST_DO_TRACE

#define DEFINE_RUST_DO_TRACE(name, proto, args)	\

	__DEFINE_RUST_DO_TRACE(name, PARAMS(proto), PARAMS(args))

#endif



#undef TRACE_INCLUDE

#undef __TRACE_INCLUDE
@@ -134,6 +141,11 @@ 
# undef UNDEF_TRACE_INCLUDE_PATH

#endif



#ifdef CREATE_RUST_TRACE_POINTS

# undef DEFINE_RUST_DO_TRACE

# define DEFINE_RUST_DO_TRACE(name, proto, args)

#endif



/* We may be processing more files */

#define CREATE_TRACE_POINTS

rust/bindings/bindings_helper.h

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/refcount.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/tracepoint.h>

#include <linux/wait.h>

#include <linux/workqueue.h>

rust/kernel/lib.rs

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ 
pub mod sync;

pub mod task;

pub mod time;

pub mod tracepoint;

pub mod types;

pub mod uaccess;

pub mod workqueue;

rust/kernel/tracepoint.rs

0 → 100644
+49 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



// Copyright (C) 2024 Google LLC.



//! Logic for tracepoints.



/// Declare the Rust entry point for a tracepoint.

///

/// This macro generates an unsafe function that calls into C, and its safety requirements will be

/// whatever the relevant C code requires. To document these safety requirements, you may add

/// doc-comments when invoking the macro.

#[macro_export]

macro_rules! declare_trace {

    ($($(#[$attr:meta])* $pub:vis unsafe fn $name:ident($($argname:ident : $argtyp:ty),* $(,)?);)*) => {$(

        $( #[$attr] )*

        #[inline(always)]

        $pub unsafe fn $name($($argname : $argtyp),*) {

            #[cfg(CONFIG_TRACEPOINTS)]

            {

                // SAFETY: It's always okay to query the static key for a tracepoint.

                let should_trace = unsafe {

                    $crate::macros::paste! {

                        $crate::jump_label::static_branch_unlikely!(

                            $crate::bindings::[< __tracepoint_ $name >],

                            $crate::bindings::tracepoint,

                            key

                        )

                    }

                };



                if should_trace {

                    $crate::macros::paste! {

                        // SAFETY: The caller guarantees that it is okay to call this tracepoint.

                        unsafe { $crate::bindings::[< rust_do_trace_ $name >]($($argname),*) };

                    }

                }

            }



            #[cfg(not(CONFIG_TRACEPOINTS))]

            {

                // If tracepoints are disabled, insert a trivial use of each argument

                // to avoid unused argument warnings.

                $( let _unused = $argname; )*

            }

        }

    )*}

}



pub use declare_trace;