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Message-ID: <20230207173026.792774721@goodmis.org>
Date: Tue, 07 Feb 2023 12:28:53 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ross Zwisler <zwisler@...gle.com>
Subject: [PATCH v2 4/4] tracing: Allow boot instances to have snapshot buffers
From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
Add to ftrace_boot_snapshot, "=<instance>" name, where the instance will
get a snapshot buffer, and will take a snapshot at the end of boot (which
will save the boot traces).
Reviewed-by: Ross Zwisler <zwisler@...gle.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes since v1: https://lkml.kernel.org/r/20230111145842.847715402@goodmis.org
- Make stub function for do_allocate_snapshot() for !CONFIG_TRACER_MAX_TRACE (kernel test robot)
- Compare strstr() to NULL and not zero (kernel test robot)
- Use sizeof(boot_snapshot_info) instead of COMMAND_LINE_SIZE (Ross Zwisler)
.../admin-guide/kernel-parameters.txt | 9 +++
kernel/trace/trace.c | 79 +++++++++++++++++--
2 files changed, 81 insertions(+), 7 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 40304dc3d319..7fa1ee4ba910 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1532,6 +1532,15 @@
boot up that is likely to be overridden by user space
start up functionality.
+ Optionally, the snapshot can also be defined for a tracing
+ instance that was created by the trace_instance= command
+ line parameter.
+
+ trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
+
+ The above will cause the "foo" tracing instance to trigger
+ a snapshot at the end of boot up.
+
ftrace_dump_on_oops[=orig_cpu]
[FTRACE] will dump the trace buffers on oops.
If no parameter is passed, ftrace will dump
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9918bf7441ed..97c88711f270 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -191,6 +191,9 @@ static bool snapshot_at_boot;
static char boot_instance_info[COMMAND_LINE_SIZE] __initdata;
static int boot_instance_index;
+static char boot_snapshot_info[COMMAND_LINE_SIZE] __initdata;
+static int boot_snapshot_index;
+
static int __init set_cmdline_ftrace(char *str)
{
strlcpy(bootup_tracer_buf, str, MAX_TRACER_SIZE);
@@ -227,9 +230,22 @@ __setup("traceoff_on_warning", stop_trace_on_warning);
static int __init boot_alloc_snapshot(char *str)
{
- allocate_snapshot = true;
- /* We also need the main ring buffer expanded */
- ring_buffer_expanded = true;
+ char *slot = boot_snapshot_info + boot_snapshot_index;
+ int left = sizeof(boot_snapshot_info) - boot_snapshot_index;
+ int ret;
+
+ if (str[0] == '=') {
+ str++;
+ if (strlen(str) >= left)
+ return -1;
+
+ ret = snprintf(slot, left, "%s\t", str);
+ boot_snapshot_index += ret;
+ } else {
+ allocate_snapshot = true;
+ /* We also need the main ring buffer expanded */
+ ring_buffer_expanded = true;
+ }
return 1;
}
__setup("alloc_snapshot", boot_alloc_snapshot);
@@ -9254,10 +9270,6 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
}
tr->allocated_snapshot = allocate_snapshot;
- /*
- * Only the top level trace array gets its snapshot allocated
- * from the kernel command line.
- */
allocate_snapshot = false;
#endif
@@ -10173,6 +10185,47 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer,
return ret;
}
+#ifdef CONFIG_TRACER_MAX_TRACE
+__init static bool tr_needs_alloc_snapshot(const char *name)
+{
+ char *test;
+ int len = strlen(name);
+ bool ret;
+
+ if (!boot_snapshot_index)
+ return false;
+
+ if (strncmp(name, boot_snapshot_info, len) == 0 &&
+ boot_snapshot_info[len] == '\t')
+ return true;
+
+ test = kmalloc(strlen(name) + 3, GFP_KERNEL);
+ if (!test)
+ return false;
+
+ sprintf(test, "\t%s\t", name);
+ ret = strstr(boot_snapshot_info, test) == NULL;
+ kfree(test);
+ return ret;
+}
+
+__init static void do_allocate_snapshot(const char *name)
+{
+ if (!tr_needs_alloc_snapshot(name))
+ return;
+
+ /*
+ * When allocate_snapshot is set, the next call to
+ * allocate_trace_buffers() (called by trace_array_get_by_name())
+ * will allocate the snapshot buffer. That will alse clear
+ * this flag.
+ */
+ allocate_snapshot = true;
+}
+#else
+static inline void do_allocate_snapshot(const char *name) { }
+#endif
+
__init static void enable_instances(void)
{
struct trace_array *tr;
@@ -10188,6 +10241,9 @@ __init static void enable_instances(void)
tok = strsep(&curr_str, ",");
+ if (IS_ENABLED(CONFIG_TRACER_MAX_TRACE))
+ do_allocate_snapshot(tok);
+
tr = trace_array_get_by_name(tok);
if (!tr) {
pr_warn("Failed to create instance buffer %s\n", curr_str);
@@ -10335,10 +10391,19 @@ __init static int tracer_alloc_buffers(void)
void __init ftrace_boot_snapshot(void)
{
+ struct trace_array *tr;
+
if (snapshot_at_boot) {
tracing_snapshot();
internal_trace_puts("** Boot snapshot taken **\n");
}
+
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+ if (tr == &global_trace)
+ continue;
+ trace_array_puts(tr, "** Boot snapshot taken **\n");
+ tracing_snapshot_instance(tr);
+ }
}
void __init early_trace_init(void)
--
2.39.1
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