lkml.org 
[lkml]   [2015]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC][PATCH v2 3/7] trace_events_filter.c: switch to memcmp() and memmem() for matching
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;
> }



\
 
 \ /
  Last update: 2015-02-06 17:41    [W:0.154 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site