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tracing: Allow stacktraces to be saved as histogram variables

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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.

Link: https://lkml.kernel.org/r/20230117152235.856323729@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Ching-lin Yu <chinglinyu@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-01-17 10:21:27 -05:00
parent 19ff804964
commit 288709c9f3
1 changed files with 41 additions and 9 deletions
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50
kernel/trace/trace_events_hist.c
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@ -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;
}
@ -2351,6 +2357,8 @@ 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)
@ -3119,13 +3127,24 @@ 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);
@ -3824,7 +3843,8 @@ 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++;
}
@ -4103,7 +4123,8 @@ 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);
}
@ -4351,7 +4372,8 @@ 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;
@ -5092,7 +5114,8 @@ 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;
@ -5105,9 +5128,18 @@ 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);