On Tue, 25 Aug 2015 11:34:19 +0530
Pratyush Anand <panand@xxxxxxxxxx> wrote:
> `perf stat -e sunrpc:svc_xprt_do_enqueue true` results in
>
> Warning: unknown op '->'
> Warning: [sunrpc:svc_xprt_do_enqueue] unknown op '->'
>
> Similar warning for svc_handle_xprt as well.
>
> Actually TP_printk() should never dereference an address saved in the ring
> buffer that points somewhere in the kernel. There's no guarantee that that
> object still exists (with the exception of static strings).
Right, that is very dangerous. It has caused kernel panics in the past.
>
> Therefore change all the arguments for TP_printk(), so that it references
> values existing in the ring buffer only.
>
> While doing that, also fix another possible bug when argument xprt could be
> NULL and TP_fast_assign() tries to access it's elements.
>
> Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
-- Steve
> ---
> include/trace/events/sunrpc.h | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
> index fd1a02cb3c82..937e482d80e9 100644
> --- a/include/trace/events/sunrpc.h
> +++ b/include/trace/events/sunrpc.h
> @@ -529,18 +529,24 @@ TRACE_EVENT(svc_xprt_do_enqueue,
>
> TP_STRUCT__entry(
> __field(struct svc_xprt *, xprt)
> + __field(struct sockaddr *, addr)
> __field(struct svc_rqst *, rqst)
> + __field(int, pid)
> + __field(unsigned long, flags)
> ),
>
> TP_fast_assign(
> __entry->xprt = xprt;
> + __entry->addr =
> + xprt ? (struct sockaddr *)&xprt->xpt_remote : NULL;
> __entry->rqst = rqst;
> + __entry->pid = rqst? rqst->rq_task->pid : 0;
> + __entry->flags = xprt ? xprt->xpt_flags : 0;
> ),
>
> TP_printk("xprt=0x%p addr=%pIScp pid=%d flags=%s", __entry->xprt,
> - (struct sockaddr *)&__entry->xprt->xpt_remote,
> - __entry->rqst ? __entry->rqst->rq_task->pid : 0,
> - show_svc_xprt_flags(__entry->xprt->xpt_flags))
> + __entry->addr, __entry->pid,
> + show_svc_xprt_flags(__entry->flags))
> );
>
> TRACE_EVENT(svc_xprt_dequeue,
> @@ -589,16 +595,21 @@ TRACE_EVENT(svc_handle_xprt,
> TP_STRUCT__entry(
> __field(struct svc_xprt *, xprt)
> __field(int, len)
> + __field(struct sockaddr *, addr)
> + __field(unsigned long, flags)
> ),
>
> TP_fast_assign(
> __entry->xprt = xprt;
> + __entry->addr =
> + xprt ? (struct sockaddr *)&xprt->xpt_remote : NULL;
> __entry->len = len;
> + __entry->flags = xprt ? xprt->xpt_flags : 0;
> ),
>
> TP_printk("xprt=0x%p addr=%pIScp len=%d flags=%s", __entry->xprt,
> - (struct sockaddr *)&__entry->xprt->xpt_remote, __entry->len,
> - show_svc_xprt_flags(__entry->xprt->xpt_flags))
> + __entry->addr, __entry->len,
> + show_svc_xprt_flags(__entry->flags))
> );
> #endif /* _TRACE_SUNRPC_H */
>
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