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

[Rong Tao]

On 9/2/25 15:08, Viktor Malik wrote:

On 9/2/25 08:17, Rong Tao wrote:

From: Rong Tao <rong...@cestc.cn>

bpf_strcasecmp() function performs same like bpf_strcmp() except ignoring
the case of the characters.

Signed-off-by: Rong Tao <rong...@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);