From ad37bcd965fda43f34cf5cc051f5d310880bd1e7 Mon Sep 17 00:00:00 2001
From: Alice Ryhl <aliceryhl@google.com>
Date: Wed, 30 Oct 2024 16:04:25 +0000
Subject: [PATCH] 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: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/linux/tracepoint.h | 28 ++++++++++++++++++-
include/trace/define_trace.h | 12 ++++++++
rust/bindings/bindings_helper.h | 1 +
rust/kernel/lib.rs | 1 +
rust/kernel/tracepoint.rs | 49 +++++++++++++++++++++++++++++++++
5 files changed, 90 insertions(+), 1 deletion(-)
create mode 100644 rust/kernel/tracepoint.rs
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 0dc67fad706c6..84c4924e499f0 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -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));
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index ff5fa17a62591..0557626b6f6a4 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -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
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index e0846e7e93e6e..752572e638a67 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -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>
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 708ff817ccc3b..55f81f49024e0 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -54,6 +54,7 @@ pub mod str;
pub mod sync;
pub mod task;
pub mod time;
+pub mod tracepoint;
pub mod types;
pub mod uaccess;
pub mod workqueue;
diff --git a/rust/kernel/tracepoint.rs b/rust/kernel/tracepoint.rs
new file mode 100644
index 0000000000000..c6e80aa99e8e1
--- /dev/null
+++ b/rust/kernel/tracepoint.rs
@@ -0,0 +1,49 @@
+// 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;
--
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