rust/kernel/tracepoint.rs

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 // Copyright (C) 2024 Google LLC.
   4
   5 //! Logic for tracepoints.
   6
   7 /// Declare the Rust entry point for a tracepoint.
   8 ///
   9 /// This macro generates an unsafe function that calls into C, and its safety requirements will be
  10 /// whatever the relevant C code requires. To document these safety requirements, you may add
  11 /// doc-comments when invoking the macro.
  12 #[macro_export]
  13 macro_rules! declare_trace {
  14     ($($(#[$attr:meta])* $pub:vis unsafe fn $name:ident($($argname:ident : $argtyp:ty),* $(,)?);)*) => {$(
  15         $( #[$attr] )*
  16         #[inline(always)]
  17         $pub unsafe fn $name($($argname : $argtyp),*) {
  18             #[cfg(CONFIG_TRACEPOINTS)]
  19             {
  20                 // SAFETY: It's always okay to query the static key for a tracepoint.
  21                 let should_trace = unsafe {
  22                     $crate::macros::paste! {
  23                         $crate::jump_label::static_branch_unlikely!(
  24                             $crate::bindings::[< __tracepoint_ $name >],
  25                             $crate::bindings::tracepoint,
  26                             key
  27                         )
  28                     }
  29                 };
  30
  31                 if should_trace {
  32                     $crate::macros::paste! {
  33                         // SAFETY: The caller guarantees that it is okay to call this tracepoint.
  34                         unsafe { $crate::bindings::[< rust_do_trace_ $name >]($($argname),*) };
  35                     }
  36                 }
  37             }
  38
  39             #[cfg(not(CONFIG_TRACEPOINTS))]
  40             {
  41                 // If tracepoints are disabled, insert a trivial use of each argument
  42                 // to avoid unused argument warnings.
  43                 $( let _unused = $argname; )*
  44             }
  45         }
  46     )*}
  47 }
  48
  49 pub use declare_trace;