On Wed, Nov 26, 2014 at 09:25:37AM -0500, Steven Rostedt wrote:
> On Wed, 26 Nov 2014 17:06:21 +0300
> Dan Carpenter <dan.carpenter@xxxxxxxxxx> 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;".
> >
> > My other concern here was that a few lines later we do:
> >
> > entry->buf[len] = '\0';
> >
> > I worried that maybe we were putting the NUL char past the end of the
> > array but I wasn't smart enough to figure out the size of entry->buf[].
>
> entry is of type struct print_entry *, which is defined by macro magic
> (sorry),
I figure this bit out using make devel/kernel/trace/trace.i.
> and would look like this:
>
> struct print_entry {
> unsigned long ip;
> char buf[];
> };
>
> But then it is allocated like so:
>
> size = sizeof(*entry) + len + 1;
> event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
> flags, pc);
>
> entry = ring_buffer_event_data(event);
I was so close to figuring this out on my own... Let me send a v2 with
an amended changelog.
regards,
dan carpenter
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