On Sat, 02 Dec 2023 14:05:24 +0100
Christian Schoenebeck <[email protected]> wrote:
> > > --- a/include/trace/events/9p.h
> > > +++ b/include/trace/events/9p.h
> > > @@ -185,7 +185,8 @@ TRACE_EVENT(9p_protocol_dump,
> > > __entry->clnt = clnt;
> > > __entry->type = pdu->id;
> > > __entry->tag = pdu->tag;
> > > - memcpy(__entry->line, pdu->sdata, P9_PROTO_DUMP_SZ);
> > > + memcpy(__entry->line, pdu->sdata,
> > > + min(pdu->capacity, P9_PROTO_DUMP_SZ));
> > > ),
> > > TP_printk("clnt %lu %s(tag = %d)\n%.3x: %16ph\n%.3x: %16ph\n",
> > > (unsigned long)__entry->clnt, show_9p_op(__entry->type),
>
> AFAICS __entry is a local variable on stack, and array __entry->line not
> intialized with zeros, i.e. the dump would contain trash at the end. Maybe
> prepending memset() before memcpy()?
__entry is a macro that points into the ring buffer that gets allocated
before this is called. TRACE_EVENT() has a __dynamic_array() field that
can handle variable length arrays. What you can do is turn this into
something like:
TRACE_EVENT(9p_protocol_dump,
TP_PROTO(struct p9_client *clnt, struct p9_fcall *pdu),
TP_ARGS(clnt, pdu),
TP_STRUCT__entry(
__field( void *, clnt
)
__field( __u8, type
)
__field( __u16, tag
)
__dynamic_array(unsigned char, line, min(pdu->capacity,
P9_PROTO_DUMP_SZ) )
),
TP_fast_assign(
__entry->clnt = clnt;
__entry->type = pdu->id;
__entry->tag = pdu->tag;
memcpy(__get_dynamic_array(line), pdu->sdata,
min(pdu->capacity, P9_PROTO_DUMP_SZ));
),
TP_printk("clnt %lu %s(tag = %d)\n%.3x: %16ph\n%.3x: %16ph\n",
(unsigned long)__entry->clnt, show_9p_op(__entry->type),
__entry->tag, 0, __get_dynamic_array(line), 16,
__get_dynamic_array(line) + 16)
);
-- Steve
