tracetool: Add Rust format support

Generating .rs files makes it possible to support tracing in rust.
This support comprises a new format, and common code that converts
the C expressions in trace-events to Rust.  In particular, types
need to be converted, and PRI macros expanded.

As of this commit no backend generates Rust code, but it is already
possible to use tracetool to generate Rust sources; they are not
functional but they compile and contain tracepoint functions.

[Move Rust argument conversion from Event to Arguments; string
 support. - Paolo]

Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-9-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

scripts/tracetool/format/rs.py

@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+"""
+trace-DIR.rs
+"""
+
+__author__     = "Tanish Desai <tanishdesai37@gmail.com>"
+__copyright__  = "Copyright 2025, Tanish Desai <tanishdesai37@gmail.com>"
+__license__    = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Stefan Hajnoczi"
+__email__      = "stefanha@redhat.com"
+
+
+from tracetool import out
+
+
+def generate(events, backend, group):
+    out('// SPDX-License-Identifier: GPL-2.0-or-later',
+        '// This file is @generated by tracetool, do not edit.',
+        '',
+        '#[allow(unused_imports)]',
+        'use std::ffi::c_char;',
+        '#[allow(unused_imports)]',
+        'use util::bindings;',
+        '',
+        '#[inline(always)]',
+        'fn trace_event_state_is_enabled(dstate: u16) -> bool {',
+        '    (unsafe { trace_events_enabled_count }) != 0 && dstate != 0',
+        '}',
+        '',
+        'extern "C" {',
+        '    static mut trace_events_enabled_count: u32;',
+        '}',)
+
+    out('extern "C" {')
+
+    for e in events:
+        out('    static mut %s: u16;' % e.api(e.QEMU_DSTATE))
+    out('}')
+
+    backend.generate_begin(events, group)
+
+    for e in events:
+        out('',
+            '#[inline(always)]',
+            '#[allow(dead_code)]',
+            'pub fn %(api)s(%(args)s)',
+            '{',
+            api=e.api(e.QEMU_TRACE),
+            args=e.args.rust_decl())
+
+        if "disable" not in e.properties:
+            backend.generate(e, group, check_trace_event_get_state=False)
+            if backend.check_trace_event_get_state:
+                event_id = 'TRACE_' + e.name.upper()
+                out('    if trace_event_state_is_enabled(unsafe { _%(event_id)s_DSTATE}) {',
+                    event_id = event_id,
+                    api=e.api())
+                backend.generate(e, group, check_trace_event_get_state=True)
+                out('    }')
+        out('}')
+
+    backend.generate_end(events, group)