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From: Steven Rostedt <rostedt@goodmis.org>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Al Viro <viro@ZenIV.linux.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH v2 2/7] implement memmem()
Date: Fri, 6 Feb 2015 17:55:49 -0500	[thread overview]
Message-ID: <20150206175549.117804c2@gandalf.local.home> (raw)
In-Reply-To: <87zj8qoepw.fsf@rasmusvillemoes.dk>

On Fri, 06 Feb 2015 23:30:19 +0100
Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> On Fri, Feb 06 2015, Al Viro <viro@ZenIV.linux.org.uk> wrote:
> 
> > +/**
> > + * strnstr - Find the first substring in a length-limited string
> > + * @s1: The string to be searched
> > + * @s2: The string to search for
> > + * @len: the maximum number of characters to search
> > + */
> > +char *strnstr(const char *s1, const char *s2, size_t len)
> > +{
> > +	return memmem(s1, len, s2, strlen(s2));
> > +}
> 
> Most strn* interfaces don't require the n to be at most the actual
> string length, but it seems that this would happily search past the '\0'
> of s1 if len is large enough, e.g.
> 
> strnstr("abc\0def", "def", 1000)
> 
> will not return NULL (unlike what the libbsd version does). So either
> that restriction should be documented or len should be replaced by
> min(len, strlen(s1)).

The version that is currently in the kernel will do exactly what the
patched version will do. Although it may be different than what libbsd
might do, we don't really care. The kernel doc states that @len will be
the maximum number of characters to search, and that's exactly what
this does.

The functionality of strnstr() does not change with this patch, so it
does not need to address your concern.

Feel free to submit a patch that states the difference of the kernel
version of strnstr with whatever version is out in the wild. But that
is out of scope with this series.

-- Steve

  reply	other threads:[~2015-02-06 22:55 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-05 19:49 [RFC][PATCHES] constifying ftrace globs Al Viro
2015-02-05 19:56 ` [RFC][PATCH 1/7] trace: fix the glob match in __unregister_ftrace_function_probe() Al Viro
2015-02-05 20:43   ` Steven Rostedt
2015-02-05 22:30     ` Al Viro
2015-02-05 22:52       ` Steven Rostedt
2015-02-05 19:56 ` [RFC][PATCH 2/7] implement memmem() Al Viro
2015-02-05 19:56 ` [RFC][PATCH 3/7] trace_events_filter.c: switch to memcmp() and memmem() for matching Al Viro
2015-02-05 19:56 ` [RFC][PATCH 4/7] ftrace: switch matching to memcmp() and memmem() Al Viro
2015-02-05 19:56 ` [RFC][PATCH 5/7] trace: make filter_parse_regex() provide the length of substring to compare with Al Viro
2015-02-05 21:29   ` Steven Rostedt
2015-02-05 21:44     ` Al Viro
2015-02-05 22:07       ` Steven Rostedt
2015-02-05 22:46         ` Al Viro
2015-02-06  4:00           ` [RFC][PATCH v2 1/7] trace: fix the glob match in __unregister_ftrace_function_probe() Al Viro
2015-02-06  4:00           ` [RFC][PATCH v2 2/7] implement memmem() Al Viro
2015-02-06 16:19             ` Steven Rostedt
2015-02-06 22:30             ` Rasmus Villemoes
2015-02-06 22:55               ` Steven Rostedt [this message]
2015-02-06 23:14                 ` Rasmus Villemoes
2015-02-06  4:00           ` [RFC][PATCH v2 3/7] trace_events_filter.c: switch to memcmp() and memmem() for matching Al Viro
2015-02-06 16:24             ` Steven Rostedt
2015-02-06  4:00           ` [RFC][PATCH v2 4/7] ftrace: switch matching to memcmp() and memmem() Al Viro
2015-02-06  4:00           ` [RFC][PATCH v2 5/7] trace: make filter_parse_regex() provide the length of substring to compare with Al Viro
2015-02-06 18:55             ` Steven Rostedt
2015-02-06  4:00           ` [RFC][PATCH v2 6/7] trace: constify filter_parse_regex(), match_records(), ftrace_match() and ftrace_match_record() Al Viro
2015-02-06 18:56             ` Steven Rostedt
2015-02-06  4:00           ` [RFC][PATCH v2 7/7] trace: constify glob arguments all way up to ftrace_function_set_regexp() Al Viro
2015-02-05 19:56 ` [RFC][PATCH 6/7] trace: constify filter_parse_regex(), match_records(), ftrace_match() and ftrace_match_record() Al Viro
2015-02-05 21:31   ` Steven Rostedt
2015-02-05 19:56 ` [RFC][PATCH 7/7] trace: constify glob arguments all way up to ftrace_function_set_regexp() Al Viro
2020-01-24 23:45 ` [RFC][PATCHES] constifying ftrace globs Steven Rostedt

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