[PATCH] tracing: Record trace_clock in last_boot_info
From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Date: 2025-04-16 14:46:41
Also in:
lkml
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> Record trace_clock information in the trace_scratch area and show it via `last_boot_info` so that reader can docode the timestamp correctly. With this change, the first line of the last_boot_info becomes trace_clock which is used when the trace was recorded. E.g. /sys/kernel/tracing/instances/boot_mapped # cat last_boot_info trace_clock: mono ffffffff81000000 [kernel] Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- include/linux/trace_clock.h | 2 ++ kernel/trace/trace.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h
index 00e8f98c940f..2245848270d2 100644
--- a/include/linux/trace_clock.h
+++ b/include/linux/trace_clock.h@@ -15,6 +15,8 @@ #include <asm/trace_clock.h> +#define TRACE_CLOCK_NAME_MAX 16 + extern u64 notrace trace_clock_local(void); extern u64 notrace trace_clock(void); extern u64 notrace trace_clock_jiffies(void);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8ddf6b17215c..e59826fa4cb3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c@@ -6004,6 +6004,7 @@ struct trace_mod_entry { }; struct trace_scratch { + char clock[TRACE_CLOCK_NAME_MAX]; unsigned long text_addr; unsigned long nr_entries; struct trace_mod_entry entries[];
@@ -6114,6 +6115,8 @@ static void update_last_data(struct trace_array *tr) if (tr->scratch) { struct trace_scratch *tscratch = tr->scratch; + strscpy(tscratch->clock, trace_clocks[tr->clock_id].name, + TRACE_CLOCK_NAME_MAX); memset(tscratch->entries, 0, flex_array_size(tscratch, entries, tscratch->nr_entries)); tscratch->nr_entries = 0;
@@ -7000,9 +7003,10 @@ static void show_last_boot_header(struct seq_file *m, struct trace_array *tr) * Otherwise it shows the KASLR address from the previous boot which * should not be the same as the current boot. */ - if (tscratch && (tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) + if (tscratch && (tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) { + seq_printf(m, "trace_clock: %s\n", tscratch->clock); seq_printf(m, "%lx\t[kernel]\n", tscratch->text_addr); - else + } else seq_puts(m, "# Current\n"); }
@@ -7289,6 +7293,12 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr) tracing_reset_online_cpus(&tr->max_buffer); #endif + if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) { + struct trace_scratch *tscratch = tr->scratch; + + strscpy(tscratch->clock, trace_clocks[i].name, TRACE_CLOCK_NAME_MAX); + } + mutex_unlock(&trace_types_lock); return 0;