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]
13macro_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
49pub use declare_trace;