Commit 784bd084 authored Feb 14, 2020 by Tom Zanussi Committed by Steven Rostedt (VMware) Feb 20, 2020

tracing: Fix number printing bug in print_synth_event()

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>

parent 38430837

kernel/trace/trace_events_hist.c

+29 −3

Original line number	Diff line number	Diff line
		@@ -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,
		print_synth_event_num_val(s, print_fmt,
		se->fields[i]->name,
		se->fields[i]->size,
		entry->fields[n_u64],
		i == se->n_fields - 1 ? "" : " ");
		space);

		if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
		trace_seq_puts(s, " (");

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