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

[Rong Tao <rtoax@foxmail.com>]

On 9/2/25 15:08, Viktor Malik wrote:
> On 9/2/25 08:17, Rong Tao wrote:
>> From: Rong Tao <rongtao@cestc.cn>
>>
>> bpf_strcasecmp() function performs same like bpf_strcmp() except ignoring
>> the case of the characters.
>>
>> Signed-off-by: Rong Tao <rongtao@cestc.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.

Viktor, Thanks for your review, i'll submit v2 soon.

Rong Tao

>
> 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);