linux-kernel - Re: [PATCH bpf-next 1/2] bpf: add bpf

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Message-ID: <f0194235-19ae-43de-b73d-b2d8b7f77035@redhat.com>
Date: Tue, 2 Sep 2025 09:08:42 +0200
From: Viktor Malik <vmalik@...hat.com>
To: Rong Tao <rtoax@...mail.com>, andrii@...nel.org, ast@...nel.org
Cc: Rong Tao <rongtao@...tc.cn>, Daniel Borkmann <daniel@...earbox.net>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
 Shuah Khan <shuah@...nel.org>,
 "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)"
 <bpf@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>,
 "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/2] bpf: add bpf_strcasecmp kfunc

On 9/2/25 08:17, Rong Tao wrote:
> From: Rong Tao <rongtao@...tc.cn>
> 
> bpf_strcasecmp() function performs same like bpf_strcmp() except ignoring
> the case of the characters.
> 
> Signed-off-by: Rong Tao <rongtao@...tc.cn>
> ---
>  kernel/bpf/helpers.c | 56 +++++++++++++++++++++++++++++++++-----------
>  1 file changed, 42 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 401b4932cc49..e807a708e5fc 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -3349,20 +3349,7 @@ __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__ign, const char *s2__ign, bool ignore_case)

No need to use the `__ign` suffix here.

Otherwise LGTM. I guess that it could be useful in some applications.

Viktor

>  {
>  	char c1, c2;
>  	int i;
> @@ -3376,6 +3363,10 @@ __bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
>  	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);
> +		if (ignore_case) {
> +			c1 = tolower(c1);
> +			c2 = tolower(c2);
> +		}
>  		if (c1 != c2)
>  			return c1 < c2 ? -1 : 1;
>  		if (c1 == '\0')
> @@ -3388,6 +3379,42 @@ __bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
>  	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);