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SubjectRe: [patch] tracing: off by one in __trace_array_vprintk()
On Wed, Nov 26, 2014 at 09:27:06AM -0500, Steven Rostedt wrote:
> On Wed, 26 Nov 2014 17:06:21 +0300
> Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> > This check says "goto out;" if we had to truncate the string.
> >
> > The "tbuffer" buffer has TRACE_BUF_SIZE bytes. The vsnprintf() function
> > returns the number of characters (not counting the NUL char) which would
> > have been printed if there were space. If we we tried to print
> > TRACE_BUF_SIZE characters, the last character would have been truncated
> > to make space for the NUL character so we should "goto out;".
> >
>
> Oh, and the NUL character is never copied. We copy the string into the
> buffer with:
>
> memcpy(&entry->buf, tbuffer, len);
>
> Where len does not include NUL, and why we add it ourselves.

Yeah. I noticed that. Probably we should change the memcpy() to:

memcpy(&entry->buf, tbuffer, len + 1);

and remove separate NUL assignment? It's a speedup! I'll do it in v2.

regards,
dan carpenter



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