Messages in this thread Patch in this message | | | Date | Fri, 6 Feb 2015 11:24:29 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC][PATCH v2 3/7] trace_events_filter.c: switch to memcmp() and memmem() for matching |
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On Fri, 6 Feb 2015 04:00:11 +0000 Al Viro <viro@ZenIV.linux.org.uk> wrote:
> From: Al Viro <viro@zeniv.linux.org.uk> > > we know the lengths in advance... > > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> > --- > kernel/trace/trace_events_filter.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c > index ced69da..6c4a96b 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -271,21 +271,25 @@ static int filter_pred_none(struct filter_pred *pred, void *event) > > static int regex_match_full(char *str, struct regex *r, int len) > { > - if (strncmp(str, r->pattern, len) == 0) > + if (len - 1 != r->len) > + return 0; > + if (memcmp(str, r->pattern, r->len) == 0) > return 1; > return 0; > } > > static int regex_match_front(char *str, struct regex *r, int len) > { > - if (strncmp(str, r->pattern, r->len) == 0) > + if (len - 1 < r->len) > + return 0; > + if (memcmp(str, r->pattern, r->len) == 0) > return 1; > return 0; > } > > static int regex_match_middle(char *str, struct regex *r, int len) > { > - if (strnstr(str, r->pattern, len)) > + if (memmem(str, len, r->pattern, r->len))
Since len includes '\0', shouldn't this be:
if (memmem(str, len - 1, r->pattern, r->len);
It doesn't break the code either way, the algorithm still works, and the original code did not pass in len-1 either. But if this is optimizing the code, might as well eliminate one extra loop.
-- Steve
> return 1; > return 0; > }
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