rust: add trace crate

The trace crate is a minimal container for dependencies of tracepoints
(so that they do not have to be imported in all the crates that use
tracepoints); it also contains a macro called "include_trace!" that is
able to find the right include file from the trace/ directory.

[Write commit message, add #[allow()]. - Paolo]

Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-10-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

rust/Cargo.lock

@@ -258,6 +258,10 @@ dependencies = [
  "util",
 ]
 
+[[package]]
+name = "trace"
+version = "0.1.0"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.12"

rust/Cargo.toml

@@ -11,6 +11,7 @@ members = [
     "hw/core",
     "hw/char/pl011",
     "hw/timer/hpet",
+    "trace",
     "util",
     "tests",
 ]

rust/meson.build

@@ -34,7 +34,7 @@ subdir('system')
 subdir('chardev')
 subdir('hw/core')
 subdir('tests')
-
+subdir('trace')
 subdir('hw')
 
 cargo = find_program('cargo', required: false)

rust/trace/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "trace"
+version = "0.1.0"
+authors = ["Tanish Desai <tanishdesai37@gmail.com>"]
+description = "QEMU tracing infrastructure support"
+resolver = "2"
+publish = false
+
+edition.workspace = true
+homepage.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[lints]
+workspace = true

rust/trace/meson.build

@@ -0,0 +1,19 @@
+rust = import('rust')
+
+lib_rs = configure_file(
+  input: 'src/lib.rs',
+  output: 'lib.rs',
+  configuration: {
+    'MESON_BUILD_ROOT': meson.project_build_root(),
+  })
+
+_trace_rs = static_library(
+  'trace',             # Library name,
+  lib_rs,
+  trace_rs_targets,         # List of generated `.rs` custom targets
+  override_options: ['rust_std=2021', 'build.rust_std=2021'],
+  dependencies: [libc_rs],
+  rust_abi: 'rust',
+)
+
+trace_rs = declare_dependency(link_with: _trace_rs)

rust/trace/src/lib.rs

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! This crate provides macros that aid in using QEMU's tracepoint
+//! functionality.
+
+#[macro_export]
+/// Define the trace-points from the named directory (which should have slashes
+/// replaced by underscore characters) as functions in a module called `trace`.
+///
+/// ```ignore
+/// ::trace::include_trace!("hw_char");
+/// // ...
+/// trace::trace_pl011_read_fifo_rx_full();
+/// ```
+macro_rules! include_trace {
+    ($name:literal) => {
+        #[allow(
+            clippy::ptr_as_ptr,
+            clippy::cast_lossless,
+            clippy::used_underscore_binding
+        )]
+        mod trace {
+            #[cfg(not(MESON))]
+            include!(concat!(
+                env!("MESON_BUILD_ROOT"),
+                "/trace/trace-",
+                $name,
+                ".rs"
+            ));
+
+            #[cfg(MESON)]
+            include!(concat!("@MESON_BUILD_ROOT@/trace/trace-", $name, ".rs"));
+        }
+    };
+}

trace/meson.build

@@ -1,5 +1,5 @@
 system_ss.add(files('control-target.c', 'trace-hmp-cmds.c'))
-
+trace_rs_targets = []
 trace_events_files = []
 foreach item : [ '.' ] + trace_events_subdirs + qapi_trace_events
   if item in qapi_trace_events
@@ -24,6 +24,11 @@ foreach item : [ '.' ] + trace_events_subdirs + qapi_trace_events
                           input: trace_events_file,
                           command: [ tracetool, group, '--format=c', '@INPUT@', '@OUTPUT@' ],
                           depend_files: tracetool_depends)
+  trace_rs = custom_target(fmt.format('trace', 'rs'),
+                          output: fmt.format('trace', 'rs'),
+                          input: trace_events_file,
+                          command: [ tracetool, group, '--format=rs', '@INPUT@', '@OUTPUT@' ],
+                          depend_files: tracetool_depends)
   if 'ust' in get_option('trace_backends')
     trace_ust_h = custom_target(fmt.format('trace-ust', 'h'),
                                 output: fmt.format('trace-ust', 'h'),
@@ -34,6 +39,7 @@ foreach item : [ '.' ] + trace_events_subdirs + qapi_trace_events
     genh += trace_ust_h
   endif
   trace_ss.add(trace_h, trace_c)
+  trace_rs_targets += trace_rs
   if 'dtrace' in get_option('trace_backends')
     trace_dtrace = custom_target(fmt.format('trace-dtrace', 'dtrace'),
                                  output: fmt.format('trace-dtrace', 'dtrace'),