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tracing: Add synth_event_trace() and related functions
Add an exported function named synth_event_trace(), allowing modules or other kernel code to trace synthetic events. Also added are several functions that allow the same functionality to be broken out in a piecewise fashion, which are useful in situations where tracing an event from a full array of values would be cumbersome. Those functions are synth_event_trace_start/end() and synth_event_add_(next)_val(). Link: http://lkml.kernel.org/r/7a84de5f1854acf4144b57efe835ca645afa764f.1580323897.git.zanussi@kernel.org Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Tom Zanussi <zanussi@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi
Steven Rostedt (VMware)
parent
35ca5207c2
commit
8dcc53ad95
@ -416,6 +416,32 @@ extern int synth_event_add_fields(struct dynevent_cmd *cmd,
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#define synth_event_gen_cmd_end(cmd) \
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dynevent_create(cmd)
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struct synth_event;
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struct synth_event_trace_state {
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struct trace_event_buffer fbuffer;
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struct synth_trace_event *entry;
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struct trace_buffer *buffer;
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struct synth_event *event;
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unsigned int cur_field;
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unsigned int n_u64;
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bool enabled;
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bool add_next;
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bool add_name;
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};
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extern int synth_event_trace(struct trace_event_file *file,
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unsigned int n_vals, ...);
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extern int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
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unsigned int n_vals);
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extern int synth_event_trace_start(struct trace_event_file *file,
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struct synth_event_trace_state *trace_state);
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extern int synth_event_add_next_val(u64 val,
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struct synth_event_trace_state *trace_state);
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extern int synth_event_add_val(const char *field_name, u64 val,
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struct synth_event_trace_state *trace_state);
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extern int synth_event_trace_end(struct synth_event_trace_state *trace_state);
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/*
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* Event file flags:
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* ENABLED - The event is enabled
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@ -398,6 +398,7 @@ struct synth_field {
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char *type;
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char *name;
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size_t size;
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unsigned int offset;
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bool is_signed;
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bool is_string;
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};
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@ -668,6 +669,8 @@ static int synth_event_define_fields(struct trace_event_call *call)
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if (ret)
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break;
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event->fields[i]->offset = n_u64;
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if (event->fields[i]->is_string) {
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offset += STR_VAR_LEN_MAX;
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n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
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@ -1791,6 +1794,466 @@ void synth_event_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen)
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}
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EXPORT_SYMBOL_GPL(synth_event_cmd_init);
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/**
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* synth_event_trace - Trace a synthetic event
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* @file: The trace_event_file representing the synthetic event
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* @n_vals: The number of values in vals
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* @args: Variable number of args containing the event values
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*
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* Trace a synthetic event using the values passed in the variable
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* argument list.
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*
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* The argument list should be a list 'n_vals' u64 values. The number
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* of vals must match the number of field in the synthetic event, and
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* must be in the same order as the synthetic event fields.
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*
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* All vals should be cast to u64, and string vals are just pointers
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* to strings, cast to u64. Strings will be copied into space
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* reserved in the event for the string, using these pointers.
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*
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* Return: 0 on success, err otherwise.
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*/
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int synth_event_trace(struct trace_event_file *file, unsigned int n_vals, ...)
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{
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struct trace_event_buffer fbuffer;
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struct synth_trace_event *entry;
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struct trace_buffer *buffer;
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struct synth_event *event;
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unsigned int i, n_u64;
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int fields_size = 0;
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va_list args;
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int ret = 0;
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/*
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* Normal event generation doesn't get called at all unless
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* the ENABLED bit is set (which attaches the probe thus
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* allowing this code to be called, etc). Because this is
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* called directly by the user, we don't have that but we
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* still need to honor not logging when disabled.
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*/
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if (!(file->flags & EVENT_FILE_FL_ENABLED))
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return 0;
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event = file->event_call->data;
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if (n_vals != event->n_fields)
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return -EINVAL;
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if (trace_trigger_soft_disabled(file))
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return -EINVAL;
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fields_size = event->n_u64 * sizeof(u64);
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/*
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* Avoid ring buffer recursion detection, as this event
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* is being performed within another event.
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*/
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buffer = file->tr->array_buffer.buffer;
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ring_buffer_nest_start(buffer);
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entry = trace_event_buffer_reserve(&fbuffer, file,
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sizeof(*entry) + fields_size);
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if (!entry) {
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ret = -EINVAL;
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goto out;
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}
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va_start(args, n_vals);
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for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
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u64 val;
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val = va_arg(args, u64);
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if (event->fields[i]->is_string) {
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char *str_val = (char *)(long)val;
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char *str_field = (char *)&entry->fields[n_u64];
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strscpy(str_field, str_val, STR_VAR_LEN_MAX);
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n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
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} else {
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entry->fields[n_u64] = val;
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n_u64++;
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}
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}
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va_end(args);
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trace_event_buffer_commit(&fbuffer);
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out:
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ring_buffer_nest_end(buffer);
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return ret;
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}
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EXPORT_SYMBOL_GPL(synth_event_trace);
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/**
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* synth_event_trace_array - Trace a synthetic event from an array
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* @file: The trace_event_file representing the synthetic event
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* @vals: Array of values
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* @n_vals: The number of values in vals
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*
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* Trace a synthetic event using the values passed in as 'vals'.
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*
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* The 'vals' array is just an array of 'n_vals' u64. The number of
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* vals must match the number of field in the synthetic event, and
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* must be in the same order as the synthetic event fields.
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*
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* All vals should be cast to u64, and string vals are just pointers
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* to strings, cast to u64. Strings will be copied into space
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* reserved in the event for the string, using these pointers.
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*
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* Return: 0 on success, err otherwise.
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*/
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int synth_event_trace_array(struct trace_event_file *file, u64 *vals,
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unsigned int n_vals)
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{
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struct trace_event_buffer fbuffer;
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struct synth_trace_event *entry;
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struct trace_buffer *buffer;
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struct synth_event *event;
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unsigned int i, n_u64;
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int fields_size = 0;
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int ret = 0;
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/*
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* Normal event generation doesn't get called at all unless
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* the ENABLED bit is set (which attaches the probe thus
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* allowing this code to be called, etc). Because this is
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* called directly by the user, we don't have that but we
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* still need to honor not logging when disabled.
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*/
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if (!(file->flags & EVENT_FILE_FL_ENABLED))
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return 0;
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event = file->event_call->data;
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if (n_vals != event->n_fields)
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return -EINVAL;
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if (trace_trigger_soft_disabled(file))
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return -EINVAL;
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fields_size = event->n_u64 * sizeof(u64);
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/*
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* Avoid ring buffer recursion detection, as this event
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* is being performed within another event.
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*/
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buffer = file->tr->array_buffer.buffer;
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ring_buffer_nest_start(buffer);
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entry = trace_event_buffer_reserve(&fbuffer, file,
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sizeof(*entry) + fields_size);
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if (!entry) {
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ret = -EINVAL;
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goto out;
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}
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for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
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if (event->fields[i]->is_string) {
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char *str_val = (char *)(long)vals[i];
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char *str_field = (char *)&entry->fields[n_u64];
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strscpy(str_field, str_val, STR_VAR_LEN_MAX);
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n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
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} else {
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entry->fields[n_u64] = vals[i];
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n_u64++;
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}
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}
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trace_event_buffer_commit(&fbuffer);
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out:
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ring_buffer_nest_end(buffer);
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return ret;
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}
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EXPORT_SYMBOL_GPL(synth_event_trace_array);
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/**
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* synth_event_trace_start - Start piecewise synthetic event trace
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* @file: The trace_event_file representing the synthetic event
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* @trace_state: A pointer to object tracking the piecewise trace state
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*
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* Start the trace of a synthetic event field-by-field rather than all
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* at once.
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*
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* This function 'opens' an event trace, which means space is reserved
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* for the event in the trace buffer, after which the event's
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* individual field values can be set through either
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* synth_event_add_next_val() or synth_event_add_val().
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*
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* A pointer to a trace_state object is passed in, which will keep
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* track of the current event trace state until the event trace is
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* closed (and the event finally traced) using
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* synth_event_trace_end().
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*
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* Note that synth_event_trace_end() must be called after all values
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* have been added for each event trace, regardless of whether adding
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* all field values succeeded or not.
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*
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* Note also that for a given event trace, all fields must be added
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* using either synth_event_add_next_val() or synth_event_add_val()
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* but not both together or interleaved.
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*
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* Return: 0 on success, err otherwise.
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*/
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int synth_event_trace_start(struct trace_event_file *file,
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struct synth_event_trace_state *trace_state)
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{
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struct synth_trace_event *entry;
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int fields_size = 0;
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int ret = 0;
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if (!trace_state) {
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ret = -EINVAL;
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goto out;
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}
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memset(trace_state, '\0', sizeof(*trace_state));
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/*
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* Normal event tracing doesn't get called at all unless the
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* ENABLED bit is set (which attaches the probe thus allowing
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* this code to be called, etc). Because this is called
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* directly by the user, we don't have that but we still need
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* to honor not logging when disabled. For the the iterated
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* trace case, we save the enabed state upon start and just
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* ignore the following data calls.
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*/
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if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
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trace_state->enabled = false;
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goto out;
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}
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trace_state->enabled = true;
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trace_state->event = file->event_call->data;
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if (trace_trigger_soft_disabled(file)) {
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ret = -EINVAL;
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goto out;
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}
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fields_size = trace_state->event->n_u64 * sizeof(u64);
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/*
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* Avoid ring buffer recursion detection, as this event
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* is being performed within another event.
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*/
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trace_state->buffer = file->tr->array_buffer.buffer;
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ring_buffer_nest_start(trace_state->buffer);
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entry = trace_event_buffer_reserve(&trace_state->fbuffer, file,
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sizeof(*entry) + fields_size);
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if (!entry) {
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ret = -EINVAL;
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goto out;
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}
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trace_state->entry = entry;
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out:
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return ret;
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}
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EXPORT_SYMBOL_GPL(synth_event_trace_start);
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static int save_synth_val(struct synth_field *field, u64 val,
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struct synth_event_trace_state *trace_state)
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{
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struct synth_trace_event *entry = trace_state->entry;
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if (field->is_string) {
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char *str_val = (char *)(long)val;
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char *str_field;
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if (!str_val)
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return -EINVAL;
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str_field = (char *)&entry->fields[field->offset];
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strscpy(str_field, str_val, STR_VAR_LEN_MAX);
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} else
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entry->fields[field->offset] = val;
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return 0;
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}
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/**
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* synth_event_add_next_val - Add the next field's value to an open synth trace
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* @val: The value to set the next field to
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* @trace_state: A pointer to object tracking the piecewise trace state
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*
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* Set the value of the next field in an event that's been opened by
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* synth_event_trace_start().
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*
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* The val param should be the value cast to u64. If the value points
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* to a string, the val param should be a char * cast to u64.
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*
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* This function assumes all the fields in an event are to be set one
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* after another - successive calls to this function are made, one for
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* each field, in the order of the fields in the event, until all
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* fields have been set. If you'd rather set each field individually
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* without regard to ordering, synth_event_add_val() can be used
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* instead.
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*
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* Note however that synth_event_add_next_val() and
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* synth_event_add_val() can't be intermixed for a given event trace -
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* one or the other but not both can be used at the same time.
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*
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* Note also that synth_event_trace_end() must be called after all
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* values have been added for each event trace, regardless of whether
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* adding all field values succeeded or not.
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*
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* Return: 0 on success, err otherwise.
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*/
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int synth_event_add_next_val(u64 val,
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struct synth_event_trace_state *trace_state)
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{
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struct synth_field *field;
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struct synth_event *event;
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int ret = 0;
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if (!trace_state) {
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ret = -EINVAL;
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goto out;
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}
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/* can't mix add_next_synth_val() with add_synth_val() */
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if (trace_state->add_name) {
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ret = -EINVAL;
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goto out;
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}
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trace_state->add_next = true;
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if (!trace_state->enabled)
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goto out;
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event = trace_state->event;
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if (trace_state->cur_field >= event->n_fields) {
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ret = -EINVAL;
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goto out;
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}
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field = event->fields[trace_state->cur_field++];
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ret = save_synth_val(field, val, trace_state);
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out:
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return ret;
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}
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EXPORT_SYMBOL_GPL(synth_event_add_next_val);
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static struct synth_field *find_synth_field(struct synth_event *event,
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const char *field_name)
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{
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struct synth_field *field = NULL;
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unsigned int i;
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for (i = 0; i < event->n_fields; i++) {
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field = event->fields[i];
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if (strcmp(field->name, field_name) == 0)
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return field;
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}
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return NULL;
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}
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/**
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* synth_event_add_val - Add a named field's value to an open synth trace
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* @field_name: The name of the synthetic event field value to set
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* @val: The value to set the next field to
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* @trace_state: A pointer to object tracking the piecewise trace state
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*
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* Set the value of the named field in an event that's been opened by
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* synth_event_trace_start().
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*
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* The val param should be the value cast to u64. If the value points
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* to a string, the val param should be a char * cast to u64.
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*
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* This function looks up the field name, and if found, sets the field
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* to the specified value. This lookup makes this function more
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* expensive than synth_event_add_next_val(), so use that or the
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* none-piecewise synth_event_trace() instead if efficiency is more
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* important.
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*
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* Note however that synth_event_add_next_val() and
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* synth_event_add_val() can't be intermixed for a given event trace -
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* one or the other but not both can be used at the same time.
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*
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* Note also that synth_event_trace_end() must be called after all
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* values have been added for each event trace, regardless of whether
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* adding all field values succeeded or not.
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*
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* Return: 0 on success, err otherwise.
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*/
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int synth_event_add_val(const char *field_name, u64 val,
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struct synth_event_trace_state *trace_state)
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{
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struct synth_trace_event *entry;
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struct synth_event *event;
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struct synth_field *field;
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int ret = 0;
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if (!trace_state) {
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ret = -EINVAL;
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goto out;
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}
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/* can't mix add_next_synth_val() with add_synth_val() */
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if (trace_state->add_next) {
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ret = -EINVAL;
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goto out;
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}
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trace_state->add_name = true;
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if (!trace_state->enabled)
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goto out;
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event = trace_state->event;
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entry = trace_state->entry;
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field = find_synth_field(event, field_name);
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if (!field) {
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ret = -EINVAL;
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goto out;
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}
|
||||
|
||||
ret = save_synth_val(field, val, trace_state);
|
||||
out:
|
||||
return ret;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synth_event_add_val);
|
||||
|
||||
/**
|
||||
* synth_event_trace_end - End piecewise synthetic event trace
|
||||
* @trace_state: A pointer to object tracking the piecewise trace state
|
||||
*
|
||||
* End the trace of a synthetic event opened by
|
||||
* synth_event_trace__start().
|
||||
*
|
||||
* This function 'closes' an event trace, which basically means that
|
||||
* it commits the reserved event and cleans up other loose ends.
|
||||
*
|
||||
* A pointer to a trace_state object is passed in, which will keep
|
||||
* track of the current event trace state opened with
|
||||
* synth_event_trace_start().
|
||||
*
|
||||
* Note that this function must be called after all values have been
|
||||
* added for each event trace, regardless of whether adding all field
|
||||
* values succeeded or not.
|
||||
*
|
||||
* Return: 0 on success, err otherwise.
|
||||
*/
|
||||
int synth_event_trace_end(struct synth_event_trace_state *trace_state)
|
||||
{
|
||||
if (!trace_state)
|
||||
return -EINVAL;
|
||||
|
||||
trace_event_buffer_commit(&trace_state->fbuffer);
|
||||
|
||||
ring_buffer_nest_end(trace_state->buffer);
|
||||
|
||||
return 0;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synth_event_trace_end);
|
||||
|
||||
static int create_synth_event(int argc, const char **argv)
|
||||
{
|
||||
const char *name = argv[0];
|
||||
|
||||
Loading…
Reference in New Issue
Block a user