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Message-ID: <20230117152235.856323729@goodmis.org>
Date: Tue, 17 Jan 2023 10:21:27 -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>,
Tom Zanussi <zanussi@...nel.org>,
Ross Zwisler <zwisler@...gle.com>,
Ching-lin Yu <chinglinyu@...gle.com>
Subject: [PATCH 2/6 v2] tracing: Allow stacktraces to be saved as histogram variables
From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
Allow to save stacktraces into a histogram variable. This will be used by
synthetic events to allow a stacktrace from one event to be passed and
displayed by another event.
The special keyword "stacktrace" is to be used to trigger a stack
trace for the event that the histogram trigger is attached to.
echo 'hist:keys=pid:st=stacktrace" > events/sched/sched_waking/trigger
Currently nothing can get access to the "$st" variable above that contains
the stack trace, but that will soon change.
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
kernel/trace/trace_events_hist.c | 52 ++++++++++++++++++++++++++------
1 file changed, 42 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index fcaf226b7744..bd67e7c3f258 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1360,6 +1360,8 @@ static const char *hist_field_name(struct hist_field *field,
field_name = field->name;
} else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
field_name = "common_timestamp";
+ else if (field->flags & HIST_FIELD_FL_STACKTRACE)
+ field_name = "stacktrace";
else if (field->flags & HIST_FIELD_FL_HITCOUNT)
field_name = "hitcount";
@@ -1980,6 +1982,10 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
if (flags & HIST_FIELD_FL_STACKTRACE) {
hist_field->fn_num = HIST_FIELD_FN_NOP;
+ hist_field->size = HIST_STACKTRACE_SIZE;
+ hist_field->type = kstrdup_const("unsigned long[]", GFP_KERNEL);
+ if (!hist_field->type)
+ goto free;
goto out;
}
@@ -2349,6 +2355,8 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
hist_data->enable_timestamps = true;
if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
hist_data->attrs->ts_in_usecs = true;
+ } else if (strcmp(field_name, "stacktrace") == 0) {
+ *flags |= HIST_FIELD_FL_STACKTRACE;
} else if (strcmp(field_name, "common_cpu") == 0)
*flags |= HIST_FIELD_FL_CPU;
else if (strcmp(field_name, "hitcount") == 0)
@@ -3117,13 +3125,24 @@ static inline void __update_field_vars(struct tracing_map_elt *elt,
var_val = hist_fn_call(val, elt, buffer, rbe, rec);
var_idx = var->var.idx;
- if (val->flags & HIST_FIELD_FL_STRING) {
+ if (val->flags & (HIST_FIELD_FL_STRING |
+ HIST_FIELD_FL_STACKTRACE)) {
char *str = elt_data->field_var_str[j++];
char *val_str = (char *)(uintptr_t)var_val;
unsigned int size;
- size = min(val->size, STR_VAR_LEN_MAX);
- strscpy(str, val_str, size);
+ if (val->flags & HIST_FIELD_FL_STRING) {
+ size = min(val->size, STR_VAR_LEN_MAX);
+ strscpy(str, val_str, size);
+ } else {
+ int e;
+
+ e = stack_trace_save((void *)str,
+ HIST_STACKTRACE_DEPTH,
+ HIST_STACKTRACE_SKIP);
+ if (e < HIST_STACKTRACE_DEPTH - 1)
+ ((unsigned long *)str)[e] = 0;
+ }
var_val = (u64)(uintptr_t)str;
}
tracing_map_set_var(elt, var_idx, var_val);
@@ -3822,7 +3841,8 @@ static void save_field_var(struct hist_trigger_data *hist_data,
{
hist_data->field_vars[hist_data->n_field_vars++] = field_var;
- if (field_var->val->flags & HIST_FIELD_FL_STRING)
+ /* Stack traces are saved in the string storage too */
+ if (field_var->val->flags & (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
hist_data->n_field_var_str++;
}
@@ -4101,7 +4121,8 @@ static int action_create(struct hist_trigger_data *hist_data,
}
hist_data->save_vars[hist_data->n_save_vars++] = field_var;
- if (field_var->val->flags & HIST_FIELD_FL_STRING)
+ if (field_var->val->flags &
+ (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
hist_data->n_save_var_str++;
kfree(param);
}
@@ -4349,7 +4370,8 @@ static int create_var_field(struct hist_trigger_data *hist_data,
if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME)
update_var_execname(hist_data->fields[val_idx]);
- if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_STRING)
+ if (!ret && hist_data->fields[val_idx]->flags &
+ (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE))
hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++;
return ret;
@@ -5090,7 +5112,8 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
if (hist_field->flags & HIST_FIELD_FL_VAR) {
var_idx = hist_field->var.idx;
- if (hist_field->flags & HIST_FIELD_FL_STRING) {
+ if (hist_field->flags &
+ (HIST_FIELD_FL_STRING | HIST_FIELD_FL_STACKTRACE)) {
unsigned int str_start, var_str_idx, idx;
char *str, *val_str;
unsigned int size;
@@ -5103,9 +5126,18 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
str = elt_data->field_var_str[idx];
val_str = (char *)(uintptr_t)hist_val;
- size = min(hist_field->size, STR_VAR_LEN_MAX);
- strscpy(str, val_str, size);
-
+ if (hist_field->flags & HIST_FIELD_FL_STRING) {
+ size = min(hist_field->size, STR_VAR_LEN_MAX);
+ strscpy(str, val_str, size);
+ } else {
+ int e;
+
+ e = stack_trace_save((void *)str,
+ HIST_STACKTRACE_DEPTH,
+ HIST_STACKTRACE_SKIP);
+ if (e < HIST_STACKTRACE_DEPTH - 1)
+ ((unsigned long *)str)[e] = 0;
+ }
hist_val = (u64)(uintptr_t)str;
}
tracing_map_set_var(elt, var_idx, hist_val);
--
2.39.0
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