Hi Trond, On 24/02/15 13:36, Trond Myklebust wrote: > On Tue, Feb 24, 2015 at 6:47 AM, James Hogan <[email protected]> wrote: >> Commit 83a712e0afef ("sunrpc: add some tracepoints around enqueue and >> dequeue of svc_xprt") merged in v3.19-rc1 added some new trace events, >> however a couple of them printed data from dereferenced pointers rather >> than storing the data in the struct. In general this isn't safe as the >> print may not happen until later when the data may have changed or been >> freed, and nor is it portable as userland won't have access to that >> other data in order to interpret the trace data itself. >> >> Fix by copying the data into the struct and printing from there. >> >> Fixes: 83a712e0afef ("sunrpc: add some tracepoints around enqueue ...") >> Signed-off-by: James Hogan <[email protected]> >> Cc: Jeff Layton <[email protected]> >> Cc: J. Bruce Fields <[email protected]> >> Cc: Trond Myklebust <[email protected]> >> Cc: Steven Rostedt <[email protected]> >> Cc: Ingo Molnar <[email protected]> >> Cc: <[email protected]> # v3.19+ >> --- >> Build tested only. Perhaps somebody familiar with the code could give it >> a spin to sanity check the trace output. >> --- >> include/trace/events/sunrpc.h | 22 +++++++++++++++------- >> 1 file changed, 15 insertions(+), 7 deletions(-) >> >> diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h >> index b9c1dc6c825a..47dfcaebfaaf 100644 >> --- a/include/trace/events/sunrpc.h >> +++ b/include/trace/events/sunrpc.h >> @@ -503,18 +503,22 @@ TRACE_EVENT(svc_xprt_do_enqueue, >> >> TP_STRUCT__entry( >> __field(struct svc_xprt *, xprt) >> - __field(struct svc_rqst *, rqst) >> + __field_struct(struct sockaddr_storage, ss) >> + __field(unsigned long, flags); >> + __field(int, pid) >> ), >> >> TP_fast_assign( >> __entry->xprt = xprt; >> - __entry->rqst = rqst; >> + xprt ? memcpy(&__entry->ss, &xprt->xpt_remote, >> sizeof(__entry->ss)) : memset(&__entry->ss, 0, sizeof(__entry->ss)); > > How could xprt ever be NULL here, and even if it was, why the esoteric > C instead of a simple 'if' statement?
Yeh, I had a straight forward unconditional assignment before, but I
changed it purely for consistency with the svc_xprt_dequeue trace event.
I don't pretend to understand the details of what is being traced
though, so I'm happy to change it if required.
Thanks
James
>
>> + __entry->flags = xprt ? xprt->xpt_flags : 0;
>> + __entry->pid = rqst ? rqst->rq_task->pid : 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))
>> + (struct sockaddr *)&__entry->ss,
>> + __entry->pid,
>> + show_svc_xprt_flags(__entry->flags))
>> );
>>
>> TRACE_EVENT(svc_xprt_dequeue,
>> @@ -562,17 +566,21 @@ TRACE_EVENT(svc_handle_xprt,
>>
>> TP_STRUCT__entry(
>> __field(struct svc_xprt *, xprt)
>> + __field_struct(struct sockaddr_storage, ss)
>> + __field(unsigned long, flags);
>> __field(int, len)
>> ),
>>
>> TP_fast_assign(
>> __entry->xprt = xprt;
>> + xprt ? memcpy(&__entry->ss, &xprt->xpt_remote,
>> sizeof(__entry->ss)) : memset(&__entry->ss, 0, sizeof(__entry->ss));
>
> Ditto.
>
>> + __entry->flags = xprt ? xprt->xpt_flags : 0;
>> __entry->len = len;
>> ),
>>
>> 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))
>> + (struct sockaddr *)&__entry->ss, __entry->len,
>> + show_svc_xprt_flags(__entry->flags))
>> );
>> #endif /* _TRACE_SUNRPC_H */
>>
>> --
>> 2.0.5
>>
>
>
>
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