[PATCH 17/25] contrib/plugins/uftrace: skeleton file

["Alex Bennée" <alex.bennee@linaro.org>]

From: Pierrick Bouvier <pierrick.bouvier@linaro.org>

We define a scoreboard that will hold our data per cpu. As well, we
define a buffer per cpu that will be used to read registers and memories
in a thread-safe way.

For now, we just instrument all instructions with an empty callback.

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-ID: <20250902075042.223990-2-pierrick.bouvier@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 contrib/plugins/uftrace.c   | 73 +++++++++++++++++++++++++++++++++++++
 contrib/plugins/meson.build |  3 +-
 2 files changed, 75 insertions(+), 1 deletion(-)
 create mode 100644 contrib/plugins/uftrace.c

diff --git a/contrib/plugins/uftrace.c b/contrib/plugins/uftrace.c
new file mode 100644
index 00000000000..4af0130b159
--- /dev/null
+++ b/contrib/plugins/uftrace.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2025, Pierrick Bouvier <pierrick.bouvier@linaro.org>
+ *
+ * Generates a trace compatible with uftrace (similar to uftrace record).
+ * https://github.com/namhyung/uftrace
+ *
+ * See docs/about/emulation.rst|Uftrace for details and examples.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <qemu-plugin.h>
+#include <glib.h>
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+typedef struct Cpu {
+    GByteArray *buf;
+} Cpu;
+
+static struct qemu_plugin_scoreboard *score;
+
+static void track_callstack(unsigned int cpu_index, void *udata)
+{
+}
+
+static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
+{
+    size_t n_insns = qemu_plugin_tb_n_insns(tb);
+
+    for (size_t i = 0; i < n_insns; i++) {
+        struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
+
+        uintptr_t pc = qemu_plugin_insn_vaddr(insn);
+        qemu_plugin_register_vcpu_insn_exec_cb(insn, track_callstack,
+                                               QEMU_PLUGIN_CB_R_REGS,
+                                               (void *) pc);
+    }
+}
+
+static void vcpu_init(qemu_plugin_id_t id, unsigned int vcpu_index)
+{
+    Cpu *cpu = qemu_plugin_scoreboard_find(score, vcpu_index);
+    cpu->buf = g_byte_array_new();
+}
+
+static void vcpu_end(unsigned int vcpu_index)
+{
+    Cpu *cpu = qemu_plugin_scoreboard_find(score, vcpu_index);
+    g_byte_array_free(cpu->buf, true);
+    memset(cpu, 0, sizeof(Cpu));
+}
+
+static void at_exit(qemu_plugin_id_t id, void *data)
+{
+    for (size_t i = 0; i < qemu_plugin_num_vcpus(); ++i) {
+        vcpu_end(i);
+    }
+
+    qemu_plugin_scoreboard_free(score);
+}
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
+                                           const qemu_info_t *info,
+                                           int argc, char **argv)
+{
+    score = qemu_plugin_scoreboard_new(sizeof(Cpu));
+    qemu_plugin_register_vcpu_init_cb(id, vcpu_init);
+    qemu_plugin_register_atexit_cb(id, at_exit, NULL);
+    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
+
+    return 0;
+}
diff --git a/contrib/plugins/meson.build b/contrib/plugins/meson.build
index 1876bc78438..7eb3629c95d 100644
--- a/contrib/plugins/meson.build
+++ b/contrib/plugins/meson.build
@@ -1,5 +1,6 @@
 contrib_plugins = ['bbv', 'cache', 'cflow', 'drcov', 'execlog', 'hotblocks',
-                   'hotpages', 'howvec', 'hwprofile', 'ips', 'stoptrigger']
+                   'hotpages', 'howvec', 'hwprofile', 'ips', 'stoptrigger',
+                   'uftrace']
 if host_os != 'windows'
   # lockstep uses socket.h
   contrib_plugins += 'lockstep'
-- 
2.47.3