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tracing: Allow boot instances to have snapshot buffers

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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).

Link: https://lkml.kernel.org/r/20230207173026.792774721@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-02-07 12:28:53 -05:00
parent d503b8f747
commit 9c1c251d67
2 changed files with 81 additions and 7 deletions
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9
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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

79
kernel/trace/trace.c
View File

@ -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 @@ out:
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 @@ out:
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)