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a=openpgp-sha256; l=6823; i=aliceryhl@google.com; h=from:subject:message-id; bh=ScFhXqb37Sff9tROWdFZiuOFbIagmHmjk+412o40cBM=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBmtP8bKBJQzPdHrRNULXgDOiP9J4adZ8/RL3zY1 TwE9qCPENyJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZrT/GwAKCRAEWL7uWMY5 RpH0D/0fxo5D4TfrvpMcRHlO64Kfv3c4LOEheRcCbCJugkos8/63GXm2Ocfb5W+ClDXQlJh8jg+ CJoPzQ7zfhn3wnmY4DDPtSb9WTwzasXXKrxPrs7tibbH/yCofkcvnXzuABlu0Ul6hlGnvSTZBNu GD/JWO4+baZG7hvNMr7vNpdVGX5VsHTGNm6DnsD+DWo6XRd+bPE70COn2MccXdzlDWYBeuCYT3g tM0a39nhMhqUnSdcBoAc6zRbtKxM8zk7dki9AhpTF0gYVEeeuxj6xsS1IZ/SknH6ozZtAP9eb56 4TB4YELJXs4K5JoJxd54kTOBQK+uPoC9HJ2ZbE6QSzZv7VIKFDibIBK+BFndK3rueR0gwLqNjZ1 wAOVBb5Zgvj4RG5DJJeAWMOFDxSHWulkNkiCm6t9nmFIgTUos8MFCYy4Tq3ZxZSZg5hAjiCGN7U micU59j4FQnI1hxZQxN4FbPi5KV2vbxxeFQl6iM8r8/bLNaOKICvTyuf6BrNka3+S//V26PBU/d Uu66oMpFnNWc8/R7thO/icIUF75gwBC6Ix6rfueypp/75MuWQZGNMsRpwYCTpho62Nw2Bj5vsy0 nHEjgNgs+M1/4bf3Vw4JDpFGforqASjYFzvsMstM5fWUQI0nvzWxKxs8NaB28r4Q7myo+j8A1pF YsISQxO7z82a0LQ== X-Mailer: b4 0.13.0 Message-ID: <20240808-tracepoint-v6-2-a23f800f1189@google.com> Subject: [PATCH v6 2/5] rust: add tracepoint support From: Alice Ryhl To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Josh Poimboeuf , Jason Baron , Ard Biesheuvel , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Andreas Hindborg Cc: linux-trace-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann , linux-arch@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Sean Christopherson , Uros Bizjak , Catalin Marinas , Will Deacon , Marc Zyngier , Oliver Upton , Mark Rutland , Ryan Roberts , Fuad Tabba , linux-arm-kernel@lists.infradead.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , Anup Patel , Andrew Jones , Alexandre Ghiti , Conor Dooley , Samuel Holland , linux-riscv@lists.infradead.org, Huacai Chen , WANG Xuerui , Bibo Mao , Tiezhu Yang , Andrew Morton , Tianrui Zhao , loongarch@lists.linux.dev, Alice Ryhl , Carlos Llamas Content-Type: text/plain; charset="utf-8" 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. Reviewed-by: Carlos Llamas Signed-off-by: Alice Ryhl --- include/linux/tracepoint.h | 22 +++++++++++++++++- 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, 84 insertions(+), 1 deletion(-) diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 6be396bb4297..5042ca588e41 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -237,6 +237,18 @@ 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(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 @@ -252,6 +264,13 @@ 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 __rust_do_trace_##name(proto) \ + { \ + __DO_TRACE(name, \ + TP_ARGS(args), \ + TP_CONDITION(cond), 0); \ + } \ static inline void trace_##name(proto) \ { \ if (static_key_false(&__tracepoint_##name.key)) \ @@ -336,7 +355,8 @@ 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..8159294c2041 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(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 8fd092e1b809..fc6f94729789 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -20,6 +20,7 @@ #include #include #include +#include #include #include diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 91af9f75d121..d00a44b000b6 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -51,6 +51,7 @@ 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 000000000000..cf2d9ad15912 --- /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_key_false!( + $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; -- 2.46.0.76.ge559c4bf1a-goog