Commit 1c662483 authored Dec 18, 2019 by Sven Schnelle Committed by Greg Kroah-Hartman Jan 09, 2020

tracing: Fix endianness bug in histogram trigger

commit fe6e096a5bbf73a142f09c72e7aa2835026eb1a3 upstream.

At least on PA-RISC and s390 synthetic histogram triggers are failing
selftests because trace_event_raw_event_synth() always writes a 64 bit
values, but the reader expects a field->size sized value. On little endian
machines this doesn't hurt, but on big endian this makes the reader always
read zero values.

Link: http://lore.kernel.org/linux-trace-devel/20191218074427.96184-4-svens@linux.ibm.com



Cc: stable@vger.kernel.org
Fixes: 4b147936 ("tracing: Add support for 'synthetic' events")
Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 0c815959

kernel/trace/trace_events_hist.c

+20 −1

Original line number	Diff line number	Diff line
		@@ -665,7 +665,26 @@ static notrace void trace_event_raw_event_synth(void *__data,
		strscpy(str_field, str_val, STR_VAR_LEN_MAX);
		n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
		} else {
		entry->fields[n_u64] = var_ref_vals[var_ref_idx + i];
		struct synth_field *field = event->fields[i];
		u64 val = var_ref_vals[var_ref_idx + i];

		switch (field->size) {
		case 1:
		(u8 )&entry->fields[n_u64] = (u8)val;
		break;

		case 2:
		(u16 )&entry->fields[n_u64] = (u16)val;
		break;

		case 4:
		(u32 )&entry->fields[n_u64] = (u32)val;
		break;

		default:
		entry->fields[n_u64] = val;
		break;
		}
		n_u64++;
		}
		}