From: Longjun Tang <tanglongjun@kylinos.cn>

Add functional tests for equality, ordering, zero-size, and null-byte
handling. Add negative tests for NULL, user-space, and invalid kernel
pointer arguments.

Signed-off-by: Longjun Tang <tanglongjun@kylinos.cn>
---
 .../bpf/progs/string_kfuncs_failure1.c          |  9 +++++++++
 .../selftests/bpf/progs/string_kfuncs_success.c | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
index bddc4e8579d2..a85d64605d0e 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
@@ -9,6 +9,9 @@
 char *user_ptr = (char *)1;
 char *invalid_kern_ptr = (char *)-1;
 
+extern int bpf_memcmp(const void *ptr1__ign, const void *ptr2__ign,
+		      size_t size) __ksym;
+
 /*
  * When passing userspace pointers, the error code differs based on arch:
  *   -ERANGE on arches with non-overlapping address spaces
@@ -53,6 +56,8 @@ 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_memcmp_null1(void *ctx) { return bpf_memcmp(NULL, "x", 1); }
+SEC("syscall")  __retval(USER_PTR_ERR)int test_memcmp_null2(void *ctx) { return bpf_memcmp("x", NULL, 1); }
 
 /* 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 +84,8 @@ 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_memcmp_user_ptr1(void *ctx) { return bpf_memcmp(user_ptr, "x", 1); }
+SEC("syscall") __retval(USER_PTR_ERR) int test_memcmp_user_ptr2(void *ctx) { return bpf_memcmp("x", user_ptr, 1); }
 
 #endif /* __TARGET_ARCH_s390 */
 
@@ -107,5 +114,7 @@ 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_memcmp_pagefault1(void *ctx) { return bpf_memcmp(invalid_kern_ptr, "x", 1); }
+SEC("syscall") __retval(-EFAULT) int test_memcmp_pagefault2(void *ctx) { return bpf_memcmp("x", invalid_kern_ptr, 1); }
 
 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..c2be9edcd282 100644
--- a/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
+++ b/tools/testing/selftests/bpf/progs/string_kfuncs_success.c
@@ -7,6 +7,9 @@
 
 char str[] = "hello world";
 
+extern int bpf_memcmp(const void *ptr1__ign, const void *ptr2__ign,
+		      size_t size) __ksym;
+
 #define __test(retval) SEC("syscall") __success __retval(retval)
 
 /* Functional tests */
@@ -60,4 +63,18 @@ __test(-ENOENT) int test_strncasestr_notfound2(void *ctx) { return bpf_strncases
 __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); }
 
+/* bpf_memcmp - functional tests */
+char data1[] = "hello world";
+char data2[] = "hello world";
+char data3[] = "hello worle";
+__test(0) int test_memcmp_eq(void *ctx) { return bpf_memcmp(data1, data2, sizeof(data1)); }
+__test(-1) int test_memcmp_neq_less(void *ctx) { return bpf_memcmp(data1, data3, sizeof(data1)); }
+__test(1) int test_memcmp_neq_greater(void *ctx) { return bpf_memcmp(data3, data1, sizeof(data1)); }
+__test(0) int test_memcmp_size_zero(void *ctx) { return bpf_memcmp(data1, data3, 0); }
+/* memcmp should NOT stop at null byte - compare past '\0' */
+char bin1[] = { 'a', '\0', 'c' };
+char bin2[] = { 'a', '\0', 'd' };
+__test(0) int test_memcmp_null_byte_eq(void *ctx) { return bpf_memcmp(bin1, bin1, sizeof(bin1)); }
+__test(-1) int test_memcmp_null_byte_neq(void *ctx) { return bpf_memcmp(bin1, bin2, sizeof(bin1)); }
+
 char _license[] SEC("license") = "GPL";
-- 
2.25.1