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tracing: Add "fields" option to show raw trace event fields 

The hex, raw and bin formats come from the old PREEMPT_RT patch set
latency tracer. That actually gave real alternatives to reading the ascii
buffer. But they have started to bit rot and they do not give a good
representation of the tracing data.

Add "fields" option that will read the trace event fields and parse the
data from how the fields are defined:

With "fields" = 0 (default)

 echo 1 > events/sched/sched_switch/enable
 cat trace
         <idle>-0       [003] d..2.   540.078653: sched_switch: prev_comm=swapper/3 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/3:1 next_pid=83 next_prio=120
     kworker/3:1-83      [003] d..2.   540.078860: sched_switch: prev_comm=kworker/3:1 prev_pid=83 prev_prio=120 prev_state=I ==> next_comm=swapper/3 next_pid=0 next_prio=120
          <idle>-0       [003] d..2.   540.206423: sched_switch: prev_comm=swapper/3 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=sshd next_pid=807 next_prio=120
            sshd-807     [003] d..2.   540.206531: sched_switch: prev_comm=sshd prev_pid=807 prev_prio=120 prev_state=S ==> next_comm=swapper/3 next_pid=0 next_prio=120
          <idle>-0       [001] d..2.   540.206597: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/u16:4 next_pid=58 next_prio=120
   kworker/u16:4-58      [001] d..2.   540.206617: sched_switch: prev_comm=kworker/u16:4 prev_pid=58 prev_prio=120 prev_state=I ==> next_comm=bash next_pid=830 next_prio=120
            bash-830     [001] d..2.   540.206678: sched_switch: prev_comm=bash prev_pid=830 prev_prio=120 prev_state=R ==> next_comm=kworker/u16:4 next_pid=58 next_prio=120
   kworker/u16:4-58      [001] d..2.   540.206696: sched_switch: prev_comm=kworker/u16:4 prev_pid=58 prev_prio=120 prev_state=I ==> next_comm=bash next_pid=830 next_prio=120
            bash-830     [001] d..2.   540.206713: sched_switch: prev_comm=bash prev_pid=830 prev_prio=120 prev_state=R ==> next_comm=kworker/u16:4 next_pid=58 next_prio=120

 echo 1 > options/fields
           <...>-998     [002] d..2.   538.643732: sched_switch: next_prio=0x78 (120) next_pid=0x0 (0) next_comm=swapper/2 prev_state=0x20 (32) prev_prio=0x78 (120) prev_pid=0x3e6 (998) prev_comm=trace-cmd
          <idle>-0       [001] d..2.   538.643806: sched_switch: next_prio=0x78 (120) next_pid=0x33e (830) next_comm=bash prev_state=0x0 (0) prev_prio=0x78 (120) prev_pid=0x0 (0) prev_comm=swapper/1
            bash-830     [001] d..2.   538.644106: sched_switch: next_prio=0x78 (120) next_pid=0x3a (58) next_comm=kworker/u16:4 prev_state=0x0 (0) prev_prio=0x78 (120) prev_pid=0x33e (830) prev_comm=bash
   kworker/u16:4-58      [001] d..2.   538.644130: sched_switch: next_prio=0x78 (120) next_pid=0x33e (830) next_comm=bash prev_state=0x80 (128) prev_prio=0x78 (120) prev_pid=0x3a (58) prev_comm=kworker/u16:4
            bash-830     [001] d..2.   538.644180: sched_switch: next_prio=0x78 (120) next_pid=0x3a (58) next_comm=kworker/u16:4 prev_state=0x0 (0) prev_prio=0x78 (120) prev_pid=0x33e (830) prev_comm=bash
   kworker/u16:4-58      [001] d..2.   538.644185: sched_switch: next_prio=0x78 (120) next_pid=0x33e (830) next_comm=bash prev_state=0x80 (128) prev_prio=0x78 (120) prev_pid=0x3a (58) prev_comm=kworker/u16:4
            bash-830     [001] d..2.   538.644204: sched_switch: next_prio=0x78 (120) next_pid=0x0 (0) next_comm=swapper/1 prev_state=0x1 (1) prev_prio=0x78 (120) prev_pid=0x33e (830) prev_comm=bash
          <idle>-0       [003] d..2.   538.644211: sched_switch: next_prio=0x78 (120) next_pid=0x327 (807) next_comm=sshd prev_state=0x0 (0) prev_prio=0x78 (120) prev_pid=0x0 (0) prev_comm=swapper/3
            sshd-807     [003] d..2.   538.644340: sched_switch: next_prio=0x78 (120) next_pid=0x0 (0) next_comm=swapper/3 prev_state=0x1 (1) prev_prio=0x78 (120) prev_pid=0x327 (807) prev_comm=sshd

It traces the data safely without using the trace print formatting.

Link: https://lore.kernel.org/linux-trace-kernel/20230328145156.497651be@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-03-28 14:51:56 -04:00
parent c2f92e8b2d
commit 80a76994b2
5 changed files with 183 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/trace/ftrace.rst
View File

@ -1027,6 +1027,7 @@ To see what is available, simply cat the file::
nohex
nobin
noblock
nofields
trace_printk
annotate
nouserstacktrace
@ -1110,6 +1111,11 @@ Here are the available options:
block
When set, reading trace_pipe will not block when polled.
fields
Print the fields as described by their types. This is a better
option than using hex, bin or raw, as it gives a better parsing
of the content of the event.
trace_printk
Can disable trace_printk() from writing into the buffer.

7
kernel/trace/trace.c
View File

@ -3726,7 +3726,7 @@ __find_next_entry(struct trace_iterator *iter, int *ent_cpu,
#define STATIC_FMT_BUF_SIZE 128
static char static_fmt_buf[STATIC_FMT_BUF_SIZE];
static char *trace_iter_expand_format(struct trace_iterator *iter)
char *trace_iter_expand_format(struct trace_iterator *iter)
{
char *tmp;
@ -4446,8 +4446,11 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
if (trace_seq_has_overflowed(s))
return TRACE_TYPE_PARTIAL_LINE;
if (event)
if (event) {
if (tr->trace_flags & TRACE_ITER_FIELDS)
return print_event_fields(iter, event);
return event->funcs->trace(iter, sym_flags, event);
}
trace_seq_printf(s, "Unknown type %d\n", entry->type);

2
kernel/trace/trace.h
View File

@ -619,6 +619,7 @@ bool trace_is_tracepoint_string(const char *str);
const char *trace_event_format(struct trace_iterator *iter, const char *fmt);
void trace_check_vprintf(struct trace_iterator *iter, const char *fmt,
va_list ap) __printf(2, 0);
char *trace_iter_expand_format(struct trace_iterator *iter);
int trace_empty(struct trace_iterator *iter);
@ -1199,6 +1200,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
C(HEX, "hex"), \
C(BIN, "bin"), \
C(BLOCK, "block"), \
C(FIELDS, "fields"), \
C(PRINTK, "trace_printk"), \
C(ANNOTATE, "annotate"), \
C(USERSTACKTRACE, "userstacktrace"), \

168
kernel/trace/trace_output.c
View File

@ -808,6 +808,174 @@ EXPORT_SYMBOL_GPL(unregister_trace_event);
* Standard events
*/
static void print_array(struct trace_iterator *iter, void *pos,
struct ftrace_event_field *field)
{
int offset;
int len;
int i;
offset = *(int *)pos & 0xffff;
len = *(int *)pos >> 16;
if (field)
offset += field->offset;
if (offset + len >= iter->ent_size) {
trace_seq_puts(&iter->seq, "<OVERFLOW>");
return;
}
for (i = 0; i < len; i++, pos++) {
if (i)
trace_seq_putc(&iter->seq, ',');
trace_seq_printf(&iter->seq, "%02x", *(unsigned char *)pos);
}
}
static void print_fields(struct trace_iterator *iter, struct trace_event_call *call,
struct list_head *head)
{
struct ftrace_event_field *field;
int offset;
int len;
int ret;
void *pos;
list_for_each_entry(field, head, link) {
trace_seq_printf(&iter->seq, " %s=", field->name);
if (field->offset + field->size > iter->ent_size) {
trace_seq_puts(&iter->seq, "<OVERFLOW>");
continue;
}
pos = (void *)iter->ent + field->offset;
switch (field->filter_type) {
case FILTER_COMM:
case FILTER_STATIC_STRING:
trace_seq_printf(&iter->seq, "%.*s", field->size, (char *)pos);
break;
case FILTER_RDYN_STRING:
case FILTER_DYN_STRING:
offset = *(int *)pos & 0xffff;
len = *(int *)pos >> 16;
if (field->filter_type == FILTER_RDYN_STRING)
offset += field->offset;
if (offset + len >= iter->ent_size) {
trace_seq_puts(&iter->seq, "<OVERFLOW>");
break;
}
pos = (void *)iter->ent + offset;
trace_seq_printf(&iter->seq, "%.*s", len, (char *)pos);
break;
case FILTER_PTR_STRING:
if (!iter->fmt_size)
trace_iter_expand_format(iter);
pos = *(void **)pos;
ret = strncpy_from_kernel_nofault(iter->fmt, pos,
iter->fmt_size);
if (ret < 0)
trace_seq_printf(&iter->seq, "(0x%px)", pos);
else
trace_seq_printf(&iter->seq, "(0x%px:%s)",
pos, iter->fmt);
break;
case FILTER_TRACE_FN:
pos = *(void **)pos;
trace_seq_printf(&iter->seq, "%pS", pos);
break;
case FILTER_CPU:
case FILTER_OTHER:
switch (field->size) {
case 1:
if (isprint(*(char *)pos)) {
trace_seq_printf(&iter->seq, "'%c'",
*(unsigned char *)pos);
}
trace_seq_printf(&iter->seq, "(%d)",
*(unsigned char *)pos);
break;
case 2:
trace_seq_printf(&iter->seq, "0x%x (%d)",
*(unsigned short *)pos,
*(unsigned short *)pos);
break;
case 4:
/* dynamic array info is 4 bytes */
if (strstr(field->type, "__data_loc")) {
print_array(iter, pos, NULL);
break;
}
if (strstr(field->type, "__rel_loc")) {
print_array(iter, pos, field);
break;
}
trace_seq_printf(&iter->seq, "0x%x (%d)",
*(unsigned int *)pos,
*(unsigned int *)pos);
break;
case 8:
trace_seq_printf(&iter->seq, "0x%llx (%lld)",
*(unsigned long long *)pos,
*(unsigned long long *)pos);
break;
default:
trace_seq_puts(&iter->seq, "<INVALID-SIZE>");
break;
}
break;
default:
trace_seq_puts(&iter->seq, "<INVALID-TYPE>");
}
}
trace_seq_putc(&iter->seq, '\n');
}
enum print_line_t print_event_fields(struct trace_iterator *iter,
struct trace_event *event)
{
struct trace_event_call *call;
struct list_head *head;
/* ftrace defined events have separate call structures */
if (event->type <= __TRACE_LAST_TYPE) {
bool found = false;
down_read(&trace_event_sem);
list_for_each_entry(call, &ftrace_events, list) {
if (call->event.type == event->type) {
found = true;
break;
}
/* No need to search all events */
if (call->event.type > __TRACE_LAST_TYPE)
break;
}
up_read(&trace_event_sem);
if (!found) {
trace_seq_printf(&iter->seq, "UNKNOWN TYPE %d\n", event->type);
goto out;
}
} else {
call = container_of(event, struct trace_event_call, event);
}
head = trace_get_fields(call);
trace_seq_printf(&iter->seq, "%s:", trace_event_name(call));
if (head && !list_empty(head))
print_fields(iter, call, head);
else
trace_seq_puts(&iter->seq, "No fields found\n");
out:
return trace_handle_return(&iter->seq);
}
enum print_line_t trace_nop_print(struct trace_iterator *iter, int flags,
struct trace_event *event)
{

2
kernel/trace/trace_output.h
View File

@ -19,6 +19,8 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip,
extern void trace_seq_print_sym(struct trace_seq *s, unsigned long address, bool offset);
extern int trace_print_context(struct trace_iterator *iter);
extern int trace_print_lat_context(struct trace_iterator *iter);
extern enum print_line_t print_event_fields(struct trace_iterator *iter,
struct trace_event *event);
extern void trace_event_read_lock(void);
extern void trace_event_read_unlock(void);