Re: [PATCH v5 6/9] contrib/plugins/uftrace: generate additional files for uftrace

[Manos Pitsidianakis <manos.pitsidianakis@linaro.org>]

On Fri, 08 Aug 2025 05:06, Pierrick Bouvier <pierrick.bouvier@linaro.org> wrote:
>Beyond traces per cpu, uftrace expect to find some specific files.
>- info: contains information about machine/program run
>  those values are not impacting uftrace behaviour, and we simply copied
>  a random example to keep things simple.
>- memory mapping: how every binary is mapped in memory. For system mode,
>  we generate an empty mapping (uftrace_symbols.py, coming in future
>  commit, will take care of that). For user mode, we copy current
>  /proc/self/maps. We don't need to do any special filtering, as
>  reported addresses will necessarily concern guest program, and not
>  QEMU and its libraries.
>- task: list of tasks. We present every vcpu/privilege level as a
>  separate process, as it's the best view we can have when generating a
>  (visual) chrome trace. Using threads is less convenient in terms of
>  UI.
>
>Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
>---
> contrib/plugins/uftrace.c | 130 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 129 insertions(+), 1 deletion(-)
>
>diff --git a/contrib/plugins/uftrace.c b/contrib/plugins/uftrace.c
>index 7737626da2f..6628b4256fd 100644
>--- a/contrib/plugins/uftrace.c
>+++ b/contrib/plugins/uftrace.c
>@@ -115,6 +115,126 @@ static uint64_t gettime_ns(void)
>     return now_ns;
> }
> 
>+static void uftrace_write_map(bool system_emulation)
>+{
>+    const char *path = "./uftrace.data/sid-0.map";
>+
>+    if (system_emulation && access(path, F_OK) == 0) {
>+        /* do not erase existing map in system emulation, as a custom one might
>+         * already have been generated by uftrace_symbols.py */
>+        return;
>+    }
>+
>+    FILE *sid_map = fopen(path, "w");
>+    g_assert(sid_map);
>+
>+    if (system_emulation) {
>+        fprintf(sid_map,
>+                "# map stack on highest address possible, to prevent uftrace\n"
>+                "# from considering any kernel address\n");
>+        fprintf(sid_map,
>+          "ffffffffffff-ffffffffffff rw-p 00000000 00:00 0 [stack]\n");
>+    } else {
>+        /* in user mode, copy /proc/self/maps instead */
>+        FILE *self_map = fopen("/proc/self/maps", "r");
>+        g_assert(self_map);
>+        for (;;) {
>+            int c = fgetc(self_map);
>+            if (c == EOF) {
>+                break;
>+            }
>+            fputc(c, sid_map);
>+        }
>+        fclose(self_map);
>+    }
>+    fclose(sid_map);
>+}
>+
>+static void uftrace_write_task(const GArray *traces)
>+{
>+    FILE *task = fopen("./uftrace.data/task.txt", "w");
>+    g_assert(task);
>+    for (int i = 0; i < traces->len; ++i) {
>+        Trace *t = g_array_index(traces, Trace*, i);
>+        fprintf(task, "SESS timestamp=0.0 pid=%"PRIu32" sid=0 exename=\"%s\"\n",
>+                t->id, t->name->str);
>+        fprintf(task, "TASK timestamp=0.0 tid=%"PRIu32" pid=%"PRIu32"\n",
>+                t->id, t->id);
>+    }
>+    fclose(task);
>+}
>+
>+static void uftrace_write_info(const GArray *traces)
>+{
>+    g_autoptr(GString) taskinfo_tids = g_string_new("taskinfo:tids=");
>+    for (int i = 0; i < traces->len; ++i) {
>+        Trace *t = g_array_index(traces, Trace*, i);
>+        const char *delim = i > 0 ? "," : "";
>+        g_string_append_printf(taskinfo_tids, "%s%"PRIu32, delim, t->id);
>+    }
>+
>+    g_autoptr(GString) taskinfo_nr_tid = g_string_new("taskinfo:nr_tid=");
>+    g_string_append_printf(taskinfo_nr_tid, "%d", traces->len);
>+
>+    FILE *info = fopen("./uftrace.data/info", "w");
>+    g_assert(info);
>+    /*
>+     * $ uftrace dump --debug
>+     * uftrace file header: magic         = 4674726163652100
>+     * uftrace file header: version       = 4
>+     * uftrace file header: header size   = 40
>+     * uftrace file header: endian        = 1 (little)
>+     * uftrace file header: class          = 2 (64 bit)
>+     * uftrace file header: features      = 0x1263 (PLTHOOK | ...
>+     * uftrace file header: info          = 0x7bff (EXE_NAME | ...
>+     *  <0000000000000000>: 46 74 72 61 63 65 21 00  04 00 00 00 28 00 01 02
>+     *  <0000000000000010>: 63 12 00 00 00 00 00 00  ff 7b 00 00 00 00 00 00
>+     *  <0000000000000020>: 00 04 00 00 00 00 00 00
>+     */
>+    const uint8_t header[] = {0x46, 0x74, 0x72, 0x61, 0x63, 0x65, 0x21, 0x00,
>+                              0x04, 0x00, 0x00, 0x00, 0x28, 0x00, 0x01, 0x02,
>+                              0x63, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
>+                              0xff, 0x7b, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
>+                              0x00, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
>+    fwrite(header, sizeof(header), 1, info);
>+    const char *info_data[] = {
>+        "exename:from_qemu",
>+        "build_id:0123456789abcdef0123456789abcdef01234567",
>+        "exit_status:0",
>+        "cmdline:uftrace record qemu",
>+        "cpuinfo:lines=2",
>+        "cpuinfo:nr_cpus=1 / 1 (online/possible)",
>+        "cpuinfo:desc=Intel 8086",

Haha what :D

>+        "meminfo:1.0 / 1.0 GB (free / total)",
>+        "osinfo:lines=3",
>+        "osinfo:kernel=Linux 6.12.33",
>+        "osinfo:hostname=pc",
>+        "osinfo:distro=\"Debian GNU/Linux 13 (trixie)\"",

So I assume these strings can be anything, why not make them blank?

>+        "taskinfo:lines=2",
>+        taskinfo_nr_tid->str,
>+        taskinfo_tids->str,
>+        "usageinfo:lines=6",
>+        "usageinfo:systime=0.000000",
>+        "usageinfo:usrtime=0.000000",
>+        "usageinfo:ctxsw=0 / 0 (voluntary / involuntary)",
>+        "usageinfo:maxrss=8016",
>+        "usageinfo:pagefault=0 / 0 (major / minor)",
>+        "usageinfo:iops=0 / 0 (read / write)",
>+        "loadinfo:0.0 / 0.0 / 0.0",
>+        "record_date:Mon Jan  1 00:00:00 2025",
>+        "elapsed_time:1000000000000.0 sec",
>+        "pattern_type:regex",
>+        "uftrace_version:v0.17 ( x86_64 dwarf python3 luajit tui perf sched dynamic kernel )",
>+        "utc_offset:1751552954",
>+        0};
>+    const char **info_data_it = info_data;
>+    while (*(info_data_it)) {
>+        fprintf(info, "%s\n", *info_data_it);
>+        ++info_data_it;
>+    }
>+    fclose(info);
>+}
>+
> static Callstack *callstack_new(void)
> {
>     Callstack *cs = g_new0(Callstack, 1);
>@@ -607,14 +727,22 @@ static void vcpu_end(unsigned int vcpu_index)
> 
> static void at_exit(qemu_plugin_id_t id, void *data)
> {
>+    bool system_emulation = (bool) data;
>+    g_autoptr(GArray) traces = g_array_new(0, 0, sizeof(Trace *));
>+
>     for (size_t i = 0; i < qemu_plugin_num_vcpus(); ++i) {
>         Cpu *cpu = qemu_plugin_scoreboard_find(score, i);
>         for (size_t j = 0; j < cpu->traces->len; ++j) {
>             Trace *t = g_array_index(cpu->traces, Trace*, j);
>             trace_flush(t, true);
>+            g_array_append_val(traces, t);
>         }
>     }
> 
>+    uftrace_write_map(system_emulation);
>+    uftrace_write_info(traces);
>+    uftrace_write_task(traces);
>+
>     for (size_t i = 0; i < qemu_plugin_num_vcpus(); ++i) {
>         vcpu_end(i);
>     }
>@@ -651,7 +779,7 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
> 
>     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_atexit_cb(id, at_exit, (void *) info->system_emulation);
>     qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
> 
>     return 0;
>-- 
>2.47.2
>

LGTM,

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>