Re: [PATCH bpf-next v3 1/2] bpf: add bpf_strcasecmp kfunc

[Rong Tao <rtoax@xxxxxxxxxxx>]

On 9/3/25 00:54, Yonghong Song wrote:
> On 9/2/25 2:19 AM, Rong Tao wrote:
> > From: Rong Tao <rongtao@xxxxxxxx>
> >
> > bpf_strcasecmp() function performs same like bpf_strcmp() except 
> > ignoring
> > the case of the characters.
> >
> > Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
> > ---
> >   kernel/bpf/helpers.c | 68 +++++++++++++++++++++++++++++++-------------
> >   1 file changed, 48 insertions(+), 20 deletions(-)
> >
> > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > index 401b4932cc49..238fd992c786 100644
> > --- a/kernel/bpf/helpers.c
> > +++ b/kernel/bpf/helpers.c
> > @@ -3349,45 +3349,72 @@ __bpf_kfunc void __bpf_trap(void)
> >    * __get_kernel_nofault instead of plain dereference to make them 
> > safe.
> >    */
> >   -/**
> > - * bpf_strcmp - Compare two strings
> > - * @s1__ign: One string
> > - * @s2__ign: Another string
> > - *
> > - * Return:
> > - * * %0       - Strings are equal
> > - * * %-1      - @s1__ign is smaller
> > - * * %1       - @s2__ign is smaller
> > - * * %-EFAULT - Cannot read one of the strings
> > - * * %-E2BIG  - One of strings is too large
> > - * * %-ERANGE - One of strings is outside of kernel address space
> > - */
> > -__bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
> > +int __bpf_strcasecmp(const char *s1, const char *s2, bool ignore_case)
>
> The function __bpf_strcasecmp should be a static function.

Thanks a lot, I just add 'static' and tested it, submit V4, please review.

Rong Tao

> >   {
> >       char c1, c2;
> >       int i;
> >   -    if (!copy_from_kernel_nofault_allowed(s1__ign, 1) ||
> > -        !copy_from_kernel_nofault_allowed(s2__ign, 1)) {
> > +    if (!copy_from_kernel_nofault_allowed(s1, 1) ||
> > +        !copy_from_kernel_nofault_allowed(s2, 1)) {
> >           return -ERANGE;
> >       }
> >         guard(pagefault)();
> >       for (i = 0; i < XATTR_SIZE_MAX; i++) {
> > -        __get_kernel_nofault(&c1, s1__ign, char, err_out);
> > -        __get_kernel_nofault(&c2, s2__ign, char, err_out);
> > +        __get_kernel_nofault(&c1, s1, char, err_out);
> > +        __get_kernel_nofault(&c2, s2, char, err_out);
> > +        if (ignore_case) {
> > +            c1 = tolower(c1);
> > +            c2 = tolower(c2);
> > +        }
> >           if (c1 != c2)
> >               return c1 < c2 ? -1 : 1;
> >           if (c1 == '\0')
> >               return 0;
> > -        s1__ign++;
> > -        s2__ign++;
> > +        s1++;
> > +        s2++;
> >       }
> >       return -E2BIG;
> >   err_out:
> >       return -EFAULT;
> >   }
> >   +/**
> > + * bpf_strcmp - Compare two strings
> > + * @s1__ign: One string
> > + * @s2__ign: Another string
> > + *
> > + * Return:
> > + * * %0       - Strings are equal
> > + * * %-1      - @s1__ign is smaller
> > + * * %1       - @s2__ign is smaller
> > + * * %-EFAULT - Cannot read one of the strings
> > + * * %-E2BIG  - One of strings is too large
> > + * * %-ERANGE - One of strings is outside of kernel address space
> > + */
> > +__bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
> > +{
> > +    return __bpf_strcasecmp(s1__ign, s2__ign, false);
> > +}
> > +
> > +/**
> > + * bpf_strcasecmp - Compare two strings, ignoring the case of the 
> > characters
> > + * @s1__ign: One string
> > + * @s2__ign: Another string
> > + *
> > + * Return:
> > + * * %0       - Strings are equal
> > + * * %-1      - @s1__ign is smaller
> > + * * %1       - @s2__ign is smaller
> > + * * %-EFAULT - Cannot read one of the strings
> > + * * %-E2BIG  - One of strings is too large
> > + * * %-ERANGE - One of strings is outside of kernel address space
> > + */
> > +__bpf_kfunc int bpf_strcasecmp(const char *s1__ign, const char 
> > *s2__ign)
> > +{
> > +    return __bpf_strcasecmp(s1__ign, s2__ign, true);
> > +}
> > +
> >   /**
> >    * bpf_strnchr - Find a character in a length limited string
> >    * @s__ign: The string to be searched
> > @@ -3832,6 +3859,7 @@ BTF_ID_FLAGS(func, bpf_iter_dmabuf_destroy, 
> > KF_ITER_DESTROY | KF_SLEEPABLE)
> >   #endif
> >   BTF_ID_FLAGS(func, __bpf_trap)
> >   BTF_ID_FLAGS(func, bpf_strcmp);
> > +BTF_ID_FLAGS(func, bpf_strcasecmp);
> >   BTF_ID_FLAGS(func, bpf_strchr);
> >   BTF_ID_FLAGS(func, bpf_strchrnul);
> >   BTF_ID_FLAGS(func, bpf_strnchr);