[PATCH bpf-next v3 2/2] selftests/bpf: Test bpf_strcat,bpf_strncat kfuncs

From: Rong Tao

Date: Thu Jul 16 2026 - 05:37:35 EST


From: Rong Tao <rongtao@xxxxxxxx>

Add tests for new kfuncs bpf_strcat() and bpf_strncat().

Signed-off-by: Rong Tao <rongtao@xxxxxxxx>
---
.../testing/selftests/bpf/prog_tests/string_kfuncs.c | 2 ++
.../selftests/bpf/progs/string_kfuncs_failure1.c | 11 +++++++++++
.../selftests/bpf/progs/string_kfuncs_failure2.c | 2 ++
.../selftests/bpf/progs/string_kfuncs_success.c | 4 ++++
4 files changed, 19 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
index 300032a19445..460567ef622a 100644
--- a/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
+++ b/tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
@@ -24,6 +24,8 @@ static const char * const test_cases[] = {
"strcasestr",
"strnstr",
"strncasestr",
+ "strcat",
+ "strncat",
};

void run_too_long_tests(void)
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
index bddc4e8579d2..973a6ba643d4 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
@@ -8,6 +8,7 @@

char *user_ptr = (char *)1;
char *invalid_kern_ptr = (char *)-1;
+char kern_buf[32] = { "hello" };

/*
* When passing userspace pointers, the error code differs based on arch:
@@ -53,6 +54,8 @@ SEC("syscall") __retval(USER_PTR_ERR)int test_strnstr_null1(void *ctx) { return
SEC("syscall") __retval(USER_PTR_ERR)int test_strnstr_null2(void *ctx) { return bpf_strnstr("hello", NULL, 1); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strncasestr_null1(void *ctx) { return bpf_strncasestr(NULL, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strncasestr_null2(void *ctx) { return bpf_strncasestr("hello", NULL, 1); }
+SEC("syscall") __retval(USER_PTR_ERR)int test_strcat_null1(void *ctx) { return bpf_strcat(kern_buf, sizeof(kern_buf), NULL); }
+SEC("syscall") __retval(USER_PTR_ERR)int test_strncat_null1(void *ctx) { return bpf_strncat(kern_buf, sizeof(kern_buf), NULL, 2); }

/* Passing userspace ptr to string kfuncs */
SEC("syscall") __retval(USER_PTR_ERR) int test_strcmp_user_ptr1(void *ctx) { return bpf_strcmp(user_ptr, "hello"); }
@@ -79,6 +82,10 @@ SEC("syscall") __retval(USER_PTR_ERR) int test_strnstr_user_ptr1(void *ctx) { re
SEC("syscall") __retval(USER_PTR_ERR) int test_strnstr_user_ptr2(void *ctx) { return bpf_strnstr("hello", user_ptr, 1); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strncasestr_user_ptr1(void *ctx) { return bpf_strncasestr(user_ptr, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strncasestr_user_ptr2(void *ctx) { return bpf_strncasestr("hello", user_ptr, 1); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strcat_user_ptr1(void *ctx) { return bpf_strcat(user_ptr, 1, "hello"); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strcat_user_ptr2(void *ctx) { return bpf_strcat(kern_buf, sizeof(kern_buf), user_ptr); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strncat_user_ptr1(void *ctx) { return bpf_strncat(user_ptr, 1, "hello", 2); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_strncat_user_ptr2(void *ctx) { return bpf_strncat(kern_buf, sizeof(kern_buf), user_ptr, 1); }

#endif /* __TARGET_ARCH_s390 */

@@ -107,5 +114,9 @@ SEC("syscall") __retval(-EFAULT) int test_strnstr_pagefault1(void *ctx) { return
SEC("syscall") __retval(-EFAULT) int test_strnstr_pagefault2(void *ctx) { return bpf_strnstr("hello", invalid_kern_ptr, 1); }
SEC("syscall") __retval(-EFAULT) int test_strncasestr_pagefault1(void *ctx) { return bpf_strncasestr(invalid_kern_ptr, "hello", 1); }
SEC("syscall") __retval(-EFAULT) int test_strncasestr_pagefault2(void *ctx) { return bpf_strncasestr("hello", invalid_kern_ptr, 1); }
+SEC("syscall") __retval(-EFAULT) int test_strcat_pagefault1(void *ctx) { return bpf_strcat(invalid_kern_ptr, 1, "hello"); }
+SEC("syscall") __retval(-EFAULT) int test_strcat_pagefault2(void *ctx) { return bpf_strcat(kern_buf, sizeof(kern_buf), invalid_kern_ptr); }
+SEC("syscall") __retval(-EFAULT) int test_strncat_pagefault1(void *ctx) { return bpf_strncat(invalid_kern_ptr, 1, "hello", 2); }
+SEC("syscall") __retval(-EFAULT) int test_strncat_pagefault2(void *ctx) { return bpf_strncat(kern_buf, sizeof(kern_buf), invalid_kern_ptr, 2); }

char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c b/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
index 412c53b87b18..38f0a5f326b5 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
@@ -23,5 +23,7 @@ SEC("syscall") int test_strstr_too_long(void *ctx) { return bpf_strstr(long_str,
SEC("syscall") int test_strcasestr_too_long(void *ctx) { return bpf_strcasestr(long_str, "hello"); }
SEC("syscall") int test_strnstr_too_long(void *ctx) { return bpf_strnstr(long_str, "hello", sizeof(long_str)); }
SEC("syscall") int test_strncasestr_too_long(void *ctx) { return bpf_strncasestr(long_str, "hello", sizeof(long_str)); }
+SEC("syscall") int test_strcat_too_long(void *ctx) { return bpf_strcat(long_str, sizeof(long_str), "hello"); }
+SEC("syscall") int test_strncat_too_long(void *ctx) { return bpf_strncat(long_str, sizeof(long_str), "hello", 3); }

char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_success.c b/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
index f65b1226a81a..b24456ad3d43 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
@@ -6,6 +6,8 @@
#include "errno.h"

char str[] = "hello world";
+char buf1[32] = "hello";
+char buf2[32] = "hello";

#define __test(retval) SEC("syscall") __success __retval(retval)

@@ -59,5 +61,7 @@ __test(-ENOENT) int test_strncasestr_notfound1(void *ctx) { return bpf_strncases
__test(-ENOENT) int test_strncasestr_notfound2(void *ctx) { return bpf_strncasestr(str, "hello", 4); }
__test(-ENOENT) int test_strncasestr_notfound3(void *ctx) { return bpf_strncasestr("", "a", 0); }
__test(0) int test_strncasestr_empty(void *ctx) { return bpf_strncasestr(str, "", 1); }
+__test(10) int test_strcat_success(void *ctx) { return bpf_strcat(buf1, sizeof(buf1), "world"); }
+__test(8) int test_strncat_success(void *ctx) { return bpf_strncat(buf2, sizeof(buf2), "world", 3); }

char _license[] SEC("license") = "GPL";
--
2.55.0