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Message-ID: <20240628-tracepoint-v4-2-353d523a9c15@google.com>
Date: Fri, 28 Jun 2024 13:23:32 +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>, "Peter Zijlstra (Intel)" <peterz@...radaed.org>, 
	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>
Subject: [PATCH v4 2/2] 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.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 include/linux/tracepoint.h      | 18 +++++++++++++++-
 include/trace/define_trace.h    | 12 +++++++++++
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/lib.rs              |  1 +
 rust/kernel/tracepoint.rs       | 47 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 78 insertions(+), 1 deletion(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 689b6d71590e..d82af4d77c9f 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -238,6 +238,20 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 #define __DECLARE_TRACE_RCU(name, proto, args, cond)
 #endif
 
+/*
+ * 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_REAL(name, proto, args)			\
+	notrace void rust_do_trace_##name(proto)			\
+	{								\
+		__DO_TRACE(name,					\
+			TP_ARGS(args),					\
+			cpu_online(raw_smp_processor_id()), 0);		\
+	}
+
 /*
  * Make sure the alignment of the structure in the __tracepoints section will
  * not add unwanted padding between the beginning of the section and the
@@ -253,6 +267,7 @@ 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 void trace_##name(proto)				\
 	{								\
 		if (static_key_false(&__tracepoint_##name.key))		\
@@ -337,7 +352,8 @@ 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));
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index 00723935dcc7..08ed5ce63a96 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -72,6 +72,13 @@
 #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_REAL(name, PARAMS(proto), PARAMS(args))
+#endif
+
 #undef TRACE_INCLUDE
 #undef __TRACE_INCLUDE
 
@@ -129,6 +136,11 @@
 # 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
 
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index ddb5644d4fd9..d442f9ccfc2c 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -15,6 +15,7 @@
 #include <linux/refcount.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/tracepoint.h>
 #include <linux/wait.h>
 #include <linux/workqueue.h>
 
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index fffd4e1dd1c1..9ae90eb69020 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -46,6 +46,7 @@
 pub mod sync;
 pub mod task;
 pub mod time;
+pub mod tracepoint;
 pub mod types;
 pub mod workqueue;
 
diff --git a/rust/kernel/tracepoint.rs b/rust/kernel/tracepoint.rs
new file mode 100644
index 000000000000..1005f09e0330
--- /dev/null
+++ b/rust/kernel/tracepoint.rs
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Logic for tracepoints.
+
+/// Declare the Rust entry point for a tracepoint.
+#[macro_export]
+macro_rules! declare_trace {
+    ($($(#[$attr:meta])* $pub:vis fn $name:ident($($argname:ident : $argtyp:ty),* $(,)?);)*) => {$(
+        $( #[$attr] )*
+        #[inline(always)]
+        $pub unsafe fn $name($($argname : $argtyp),*) {
+            #[cfg(CONFIG_TRACEPOINTS)]
+            {
+                use $crate::bindings::*;
+
+                // SAFETY: It's always okay to query the static key for a tracepoint.
+                let should_trace = unsafe {
+                    $crate::macros::paste! {
+                        $crate::static_key::static_key_false!(
+                            [< __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 { [< 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;

-- 
2.45.2.803.g4e1b14247a-goog


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