lkml.org 
[lkml]   [2020]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] tracing: Add support for dynamic strings to synthetic events
On Tue, 29 Sep 2020 15:01:59 -0700
Axel Rasmussen <axelrasmussen@google.com> wrote:

> > event->fields[i]->offset = n_u64;
> >
> > - if (event->fields[i]->is_string) {
> > + if (event->fields[i]->is_string && !event->fields[i]->is_dynamic) {
> > offset += STR_VAR_LEN_MAX;
> > n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
> > } else {
> > @@ -139,6 +139,9 @@ static int synth_field_string_size(char *type)
> > if (len > 3)
> > return -EINVAL;
> >
> > + if (len == 0)
> > + return 0; /* variable-length string */
> > +
> > strncpy(buf, start, len);
> > buf[len] = '\0';
> >
> > @@ -290,10 +293,25 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
> >
> > /* parameter values */
> > if (se->fields[i]->is_string) {
> > - trace_seq_printf(s, print_fmt, se->fields[i]->name,
> > - (char *)&entry->fields[n_u64],
> > - i == se->n_fields - 1 ? "" : " ");
> > - n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
> > + if (se->fields[i]->is_dynamic) {
> > + u32 offset, data_offset;
> > + char *str_field;
> > +
> > + offset = (u32)entry->fields[n_u64];
> > + data_offset = offset & 0xffff;
> > +
> > + str_field = (char *)entry + data_offset;
>
> Is it better to re-use __get_str from include/trace/trace_events.h
> instead of writing this out directly?
>
> > +
> > + trace_seq_printf(s, print_fmt, se->fields[i]->name,
> > + str_field,
> > + i == se->n_fields - 1 ? "" : " ");
> > + n_u64++;
> > + } else {
> > + trace_seq_printf(s, print_fmt, se->fields[i]->name,
> > + (char *)&entry->fields[n_u64],
> > + i == se->n_fields - 1 ? "" : " ");
> > + n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
> > + }
> > } else {
> > struct trace_print_flags __flags[] = {
> > __def_gfpflag_names, {-1, NULL} };
> > @@ -325,16 +343,52 @@ static struct trace_event_functions synth_event_funcs = {
> > .trace = print_synth_event
> > };
> >
> > +static unsigned int trace_string(struct synth_trace_event *entry,
> > + struct synth_event *event,
> > + char *str_val,
> > + bool is_dynamic,
> > + unsigned int data_size,
> > + unsigned int *n_u64)
> > +{
> > + unsigned int len = 0;
> > + char *str_field;
> > +
> > + if (is_dynamic) {
> > + u32 data_offset;
> > +
> > + data_offset = offsetof(typeof(*entry), fields);
> > + data_offset += event->n_u64 * sizeof(u64);
> > + data_offset += data_size;
> > +
> > + str_field = (char *)entry + data_offset;
> > +
> > + len = strlen(str_val) + 1;
> > + strscpy(str_field, str_val, len);
> > +
> > + data_offset |= len << 16;
> > + *(u32 *)&entry->fields[*n_u64] = data_offset;
>
> Similar thing here, is it possible to reuse __dynamic_array or __string?

Interesting idea.

I'd prefer to keep it broken out for this patch set, and then we could look
at incorporating this file to use the macros of <trace/trace_event.h>.

But I much rather have that be a separate patch that does that as an
enhancement than to include it in this file doing more work.

-- Steve


>
> > +
> > + (*n_u64)++;
> > + } else {
> > + str_field = (char *)&entry->fields[*n_u64];
> > +
> > + strscpy(str_field, str_val, STR_VAR_LEN_MAX);
> > + (*n_u64) += STR_VAR_LEN_MAX / sizeof(u64);
> > + }
> > +
> > + return len;
> > +}
> > +
> > static n

\
 
 \ /
  Last update: 2020-09-30 00:10    [W:0.071 / U:0.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site