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tracing: Fix endianness bug in histogram trigger 

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: 4b147936fa ("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>
This commit is contained in:
Sven Schnelle 2019-12-18 08:44:27 +01:00 committed by Steven Rostedt (VMware)
parent 01f36a554e
commit fe6e096a5b
1 changed files with 20 additions and 1 deletions
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21
kernel/trace/trace_events_hist.c
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@ -911,7 +911,26 @@ 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++;
}
}