linux-kernel - Re: [PATCH bpf-next v3 1/2] bpf: add bpf

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Message-ID: <tencent_C34BE7725EE5E7556B540B91C3A05E083D05@qq.com>
Date: Wed, 3 Sep 2025 07:49:09 +0800
From: Rong Tao <rtoax@...mail.com>
To: Yonghong Song <yonghong.song@...ux.dev>, andrii@...nel.org,
 ast@...nel.org, vmalik@...hat.com
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>,
 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 v3 1/2] bpf: add bpf_strcasecmp kfunc


On 9/3/25 00:54, Yonghong Song wrote:
>
>
> On 9/2/25 2:19 AM, 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 | 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);
>