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tracing: Fix number printing bug in print_synth_event()

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Fix a varargs-related bug in print_synth_event() which resulted in
strange output and oopses on 32-bit x86 systems. The problem is that
trace_seq_printf() expects the varargs to match the format string, but
print_synth_event() was always passing u64 values regardless.  This
results in unspecified behavior when unpacking with va_arg() in
trace_seq_printf().

Add a function that takes the size into account when calling
trace_seq_printf().

Before:

  modprobe-1731  [003] ....   919.039758: gen_synth_test: next_pid_field=777(null)next_comm_field=hula hoops ts_ns=1000000 ts_ms=1000 cpu=3(null)my_string_field=thneed my_int_field=598(null)

After:

 insmod-1136  [001] ....    36.634590: gen_synth_test: next_pid_field=777 next_comm_field=hula hoops ts_ns=1000000 ts_ms=1000 cpu=1 my_string_field=thneed my_int_field=598

Link: http://lkml.kernel.org/r/a9b59eb515dbbd7d4abe53b347dccf7a8e285657.1581720155.git.zanussi@kernel.org

Reported-by: Steven Rostedt (VMware) <rostedt@goodmis.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 2020-02-14 16:56:41 -06:00 committed by Steven Rostedt (VMware)
parent 3843083772
commit 784bd0847e
1 changed files with 29 additions and 3 deletions
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32
kernel/trace/trace_events_hist.c
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@ -820,6 +820,29 @@ static const char *synth_field_fmt(char *type)
return fmt;
}
static void print_synth_event_num_val(struct trace_seq *s,
char *print_fmt, char *name,
int size, u64 val, char *space)
{
switch (size) {
case 1:
trace_seq_printf(s, print_fmt, name, (u8)val, space);
break;
case 2:
trace_seq_printf(s, print_fmt, name, (u16)val, space);
break;
case 4:
trace_seq_printf(s, print_fmt, name, (u32)val, space);
break;
default:
trace_seq_printf(s, print_fmt, name, val, space);
break;
}
}
static enum print_line_t print_synth_event(struct trace_iterator *iter,
int flags,
struct trace_event *event)
@ -858,10 +881,13 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
} else {
struct trace_print_flags __flags[] = {
__def_gfpflag_names, {-1, NULL} };
char *space = (i == se->n_fields - 1 ? "" : " ");
trace_seq_printf(s, print_fmt, se->fields[i]->name,
entry->fields[n_u64],
i == se->n_fields - 1 ? "" : " ");
print_synth_event_num_val(s, print_fmt,
se->fields[i]->name,
se->fields[i]->size,
entry->fields[n_u64],
space);
if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
trace_seq_puts(s, " (");