Merge branch 'bpf-add-kfunc-bpf_strncasecmp'

Yuzuki Ishiyama says:

====================
bpf: Add kfunc bpf_strncasecmp()

This patchset introduces bpf_strncasecmp to allow case-insensitive and
limited-length string comparison. This is useful for parsing protocol
headers like HTTP.
---

Changes in v5:
- Fixed the test function numbering

Changes in v4:
- Updated the loop variable to maintain style consistency

Changes in v3:
- Use ternary operator to maintain style consistency
- Reverted unnecessary doc comment about XATTR_SIZE_MAX

Changes in v2:
- Compute max_sz upfront and remove len check from the loop body
- Document that @len is limited by XATTR_SIZE_MAX
====================

Link: https://patch.msgid.link/20260121033328.1850010-1-ishiyama@hpc.is.uec.ac.jp
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

5 files changed, 40 insertions, 5 deletions

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 637677815365..b54ec0e945aa 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3413,7 +3413,7 @@ __bpf_kfunc void __bpf_trap(void)
  * __get_kernel_nofault instead of plain dereference to make them safe.
  */
 
-static int __bpf_strcasecmp(const char *s1, const char *s2, bool ignore_case)
+static int __bpf_strncasecmp(const char *s1, const char *s2, bool ignore_case, size_t len)
 {
 	char c1, c2;
 	int i;
@@ -3424,7 +3424,7 @@ static int __bpf_strcasecmp(const char *s1, const char *s2, bool ignore_case)
 	}
 
 	guard(pagefault)();
-	for (i = 0; i < XATTR_SIZE_MAX; i++) {
+	for (i = 0; i < len && i < XATTR_SIZE_MAX; i++) {
 		__get_kernel_nofault(&c1, s1, char, err_out);
 		__get_kernel_nofault(&c2, s2, char, err_out);
 		if (ignore_case) {
@@ -3438,7 +3438,7 @@ static int __bpf_strcasecmp(const char *s1, const char *s2, bool ignore_case)
 		s1++;
 		s2++;
 	}
-	return -E2BIG;
+	return i == XATTR_SIZE_MAX ? -E2BIG : 0;
 err_out:
 	return -EFAULT;
 }
@@ -3458,7 +3458,7 @@ err_out:
  */
 __bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
 {
-	return __bpf_strcasecmp(s1__ign, s2__ign, false);
+	return __bpf_strncasecmp(s1__ign, s2__ign, false, XATTR_SIZE_MAX);
 }
 
 /**
@@ -3476,7 +3476,26 @@ __bpf_kfunc int bpf_strcmp(const char *s1__ign, const char *s2__ign)
  */
 __bpf_kfunc int bpf_strcasecmp(const char *s1__ign, const char *s2__ign)
 {
-	return __bpf_strcasecmp(s1__ign, s2__ign, true);
+	return __bpf_strncasecmp(s1__ign, s2__ign, true, XATTR_SIZE_MAX);
+}
+
+/*
+ * bpf_strncasecmp - Compare two length-limited strings, ignoring case
+ * @s1__ign: One string
+ * @s2__ign: Another string
+ * @len: The maximum number of characters to compare
+ *
+ * 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_strncasecmp(const char *s1__ign, const char *s2__ign, size_t len)
+{
+	return __bpf_strncasecmp(s1__ign, s2__ign, true, len);
 }
 
 /**
@@ -4526,6 +4545,7 @@ BTF_ID_FLAGS(func, bpf_iter_dmabuf_destroy, KF_ITER_DESTROY | KF_SLEEPABLE)
 BTF_ID_FLAGS(func, __bpf_trap)
 BTF_ID_FLAGS(func, bpf_strcmp);
 BTF_ID_FLAGS(func, bpf_strcasecmp);
+BTF_ID_FLAGS(func, bpf_strncasecmp);
 BTF_ID_FLAGS(func, bpf_strchr);
 BTF_ID_FLAGS(func, bpf_strchrnul);
 BTF_ID_FLAGS(func, bpf_strnchr);
diff --git a/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
index 0f3bf594e7a5..300032a19445 100644
--- a/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
@@ -9,6 +9,7 @@
 static const char * const test_cases[] = {
 	"strcmp",
 	"strcasecmp",
+	"strncasecmp",
 	"strchr",
 	"strchrnul",
 	"strnchr",
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
index 826e6b6aff7e..bddc4e8579d2 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
@@ -33,6 +33,8 @@ SEC("syscall") __retval(USER_PTR_ERR) int test_strcmp_null1(void *ctx) { return
 SEC("syscall")  __retval(USER_PTR_ERR)int test_strcmp_null2(void *ctx) { return bpf_strcmp("hello", NULL); }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strcasecmp_null1(void *ctx) { return bpf_strcasecmp(NULL, "HELLO"); }
 SEC("syscall")  __retval(USER_PTR_ERR)int test_strcasecmp_null2(void *ctx) { return bpf_strcasecmp("HELLO", NULL); }
+SEC("syscall") __retval(USER_PTR_ERR)int test_strncasecmp_null1(void *ctx) { return bpf_strncasecmp(NULL, "HELLO", 5); }
+SEC("syscall")  __retval(USER_PTR_ERR)int test_strncasecmp_null2(void *ctx) { return bpf_strncasecmp("HELLO", NULL, 5);	 }
 SEC("syscall")  __retval(USER_PTR_ERR)int test_strchr_null(void *ctx) { return bpf_strchr(NULL, 'a'); }
 SEC("syscall")  __retval(USER_PTR_ERR)int test_strchrnul_null(void *ctx) { return bpf_strchrnul(NULL, 'a'); }
 SEC("syscall")  __retval(USER_PTR_ERR)int test_strnchr_null(void *ctx) { return bpf_strnchr(NULL, 1, 'a'); }
@@ -57,6 +59,8 @@ SEC("syscall") __retval(USER_PTR_ERR) int test_strcmp_user_ptr1(void *ctx) { ret
 SEC("syscall") __retval(USER_PTR_ERR) int test_strcmp_user_ptr2(void *ctx) { return bpf_strcmp("hello", user_ptr); }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strcasecmp_user_ptr1(void *ctx) { return bpf_strcasecmp(user_ptr, "HELLO"); }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strcasecmp_user_ptr2(void *ctx) { return bpf_strcasecmp("HELLO", user_ptr); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strncasecmp_user_ptr1(void *ctx) { return bpf_strncasecmp(user_ptr, "HELLO", 5); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strncasecmp_user_ptr2(void *ctx) { return bpf_strncasecmp("HELLO", user_ptr, 5);	 }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strchr_user_ptr(void *ctx) { return bpf_strchr(user_ptr, 'a'); }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strchrnul_user_ptr(void *ctx) { return bpf_strchrnul(user_ptr, 'a'); }
 SEC("syscall") __retval(USER_PTR_ERR) int test_strnchr_user_ptr(void *ctx) { return bpf_strnchr(user_ptr, 1, 'a'); }
@@ -83,6 +87,8 @@ SEC("syscall") __retval(-EFAULT) int test_strcmp_pagefault1(void *ctx) { return
 SEC("syscall") __retval(-EFAULT) int test_strcmp_pagefault2(void *ctx) { return bpf_strcmp("hello", invalid_kern_ptr); }
 SEC("syscall") __retval(-EFAULT) int test_strcasecmp_pagefault1(void *ctx) { return bpf_strcasecmp(invalid_kern_ptr, "HELLO"); }
 SEC("syscall") __retval(-EFAULT) int test_strcasecmp_pagefault2(void *ctx) { return bpf_strcasecmp("HELLO", invalid_kern_ptr); }
+SEC("syscall") __retval(-EFAULT) int test_strncasecmp_pagefault1(void *ctx) { return bpf_strncasecmp(invalid_kern_ptr, "HELLO", 5); }
+SEC("syscall") __retval(-EFAULT) int test_strncasecmp_pagefault2(void *ctx) { return bpf_strncasecmp("HELLO", invalid_kern_ptr, 5);	 }
 SEC("syscall") __retval(-EFAULT) int test_strchr_pagefault(void *ctx) { return bpf_strchr(invalid_kern_ptr, 'a'); }
 SEC("syscall") __retval(-EFAULT) int test_strchrnul_pagefault(void *ctx) { return bpf_strchrnul(invalid_kern_ptr, 'a'); }
 SEC("syscall") __retval(-EFAULT) int test_strnchr_pagefault(void *ctx) { return bpf_strnchr(invalid_kern_ptr, 1, 'a'); }
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c b/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
index 05e1da1f250f..412c53b87b18 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
@@ -8,6 +8,7 @@ char long_str[XATTR_SIZE_MAX + 1];
 
 SEC("syscall") int test_strcmp_too_long(void *ctx) { return bpf_strcmp(long_str, long_str); }
 SEC("syscall") int test_strcasecmp_too_long(void *ctx) { return bpf_strcasecmp(long_str, long_str); }
+SEC("syscall") int test_strncasecmp_too_long(void *ctx) { return bpf_strncasecmp(long_str, long_str, sizeof(long_str)); }
 SEC("syscall") int test_strchr_too_long(void *ctx) { return bpf_strchr(long_str, 'b'); }
 SEC("syscall") int test_strchrnul_too_long(void *ctx) { return bpf_strchrnul(long_str, 'b'); }
 SEC("syscall") int test_strnchr_too_long(void *ctx) { return bpf_strnchr(long_str, sizeof(long_str), 'b'); }
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_success.c b/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
index a8513964516b..f65b1226a81a 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
@@ -17,6 +17,13 @@ __test(0) int test_strcasecmp_eq2(void *ctx) { return bpf_strcasecmp(str, "HELLO
 __test(0) int test_strcasecmp_eq3(void *ctx) { return bpf_strcasecmp(str, "HELLO world"); }
 __test(1) int test_strcasecmp_neq1(void *ctx) { return bpf_strcasecmp(str, "hello"); }
 __test(1) int test_strcasecmp_neq2(void *ctx) { return bpf_strcasecmp(str, "HELLO"); }
+__test(0) int test_strncasecmp_eq1(void *ctx) { return bpf_strncasecmp(str, "hello world", 11); }
+__test(0) int test_strncasecmp_eq2(void *ctx) { return bpf_strncasecmp(str, "HELLO WORLD", 11); }
+__test(0) int test_strncasecmp_eq3(void *ctx) { return bpf_strncasecmp(str, "HELLO world", 11); }
+__test(0) int test_strncasecmp_eq4(void *ctx) { return bpf_strncasecmp(str, "hello", 5); }
+__test(0) int test_strncasecmp_eq5(void *ctx) { return bpf_strncasecmp(str, "hello world!", 11); }
+__test(-1) int test_strncasecmp_neq1(void *ctx) { return bpf_strncasecmp(str, "hello!", 6); }
+__test(1) int test_strncasecmp_neq2(void *ctx) { return bpf_strncasecmp(str, "abc", 3); }
 __test(1) int test_strchr_found(void *ctx) { return bpf_strchr(str, 'e'); }
 __test(11) int test_strchr_null(void *ctx) { return bpf_strchr(str, '\0'); }
 __test(-ENOENT) int test_strchr_notfound(void *ctx) { return bpf_strchr(str, 'x'); }