[PATCH v4 01/10] string: provide strends()

[Bartosz Golaszewski]

On Mon, Nov 17, 2025 at 9:33 PM Kees Cook <kees at kernel.org> wrote:
>
> On Wed, Nov 12, 2025 at 02:55:30PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>
> >
> > Implement a function for checking if a string ends with a different
> > string and add its kunit test cases.
> >
> > Acked-by: Linus Walleij <linus.walleij at linaro.org>
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski at linaro.org>
> > ---

Hi Kees!

Thanks for the review. I already queued this for v6.19, so let me
address the issues in a follow-up.

> >  include/linux/string.h   | 18 ++++++++++++++++++
> >  lib/tests/string_kunit.c | 13 +++++++++++++
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index fdd3442c6bcbd786e177b6e87358e1065a0ffafc..929d05d1247c76eb9011fe34250b487834b2d3c9 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -562,4 +562,22 @@ static inline bool strstarts(const char *str, const char *prefix)
> >       return strncmp(str, prefix, strlen(prefix)) == 0;
> >  }
> >
> > +/**
> > + * strends - Check if a string ends with another string.
> > + * @str - NULL-terminated string to check against @suffix
> > + * @suffix - NULL-terminated string defining the suffix to look for in @str
> > + *
> > + * Returns:
> > + * True if @str ends with @suffix. False in all other cases.
>
> Maybe added "empty strings never match"?
>

But they do, please see the test.

> > + */
> > +static inline bool strends(const char *str, const char *suffix)
>
> These are required to be non-NULL, so we might want to consider marking
> them as such with the "nonnull" attribute. We don't use it much in Linux
> yet, but I do see a few places.
>
> e.g.:
>
> static inline bool __attribute__((nonnull(1,2)))
> strends(const char *str, const char *suffix)
>

Ok.

> > +{
> > +     unsigned int str_len = strlen(str), suffix_len = strlen(suffix);
> > +
> > +     if (str_len < suffix_len)
> > +             return false;
> > +
> > +     return !(strcmp(str + str_len - suffix_len, suffix));
> > +}
>
> We should probably add it to strlen and strcmp as well. :)
>

Sure but that's outside of the scope of this.

Bart