[RFC bpf-next 5/9] selftests/bpf: Add __srcptr kfunc arguments test

[Jiri Olsa <jolsa@kernel.org>]

Add positive kfunc tests for read-only global and writable stack sources
annotated with __srcptr. Also verify that a read-only source is rejected
when passed to a writable mem_len argument.

Assisted-by: Codex:GPT-6
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/testing/selftests/bpf/prog_tests/kfunc_call.c  |  2 ++
 tools/testing/selftests/bpf/progs/kfunc_call_fail.c  | 10 ++++++++++
 tools/testing/selftests/bpf/progs/kfunc_call_test.c  | 12 ++++++++++++
 tools/testing/selftests/bpf/test_kmods/bpf_testmod.c |  5 +++++
 .../selftests/bpf/test_kmods/bpf_testmod_kfunc.h     |  1 +
 5 files changed, 30 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
index 0063e60d6f2f..9b832c5961f5 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
@@ -63,6 +63,7 @@ static struct kfunc_test_params kfunc_tests[] = {
 	 */
 	SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_fail, -EINVAL, "processed 4 insns"),
 	SYSCALL_NULL_CTX_FAIL(kfunc_syscall_test_null_fail, -EINVAL, "processed 4 insns"),
+	TC_FAIL(kfunc_call_test_mem_len_fail_readonly, 0, "write into map forbidden"),
 	TC_FAIL(kfunc_call_test_get_mem_fail_rdonly, 0, "R0 cannot write into rdonly_mem"),
 	TC_FAIL(kfunc_call_test_get_mem_fail_use_after_free, 0, "invalid mem access 'scalar'"),
 	TC_FAIL(kfunc_call_test_get_mem_fail_oob, 0, "min value is outside of the allowed memory range"),
@@ -82,6 +83,7 @@ static struct kfunc_test_params kfunc_tests[] = {
 	TC_TEST(kfunc_call_test5_asm, 0),
 	TC_TEST(kfunc_call_test_ref_btf_id, 0),
 	TC_TEST(kfunc_call_test_get_mem, 42),
+	TC_TEST(kfunc_call_test_srcptr, 0),
 	SYSCALL_TEST(kfunc_syscall_test, 0),
 	SYSCALL_NULL_CTX_TEST(kfunc_syscall_test_null, 0),
 	TC_TEST(kfunc_call_test_static_unused_arg, 0),
diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_fail.c b/tools/testing/selftests/bpf/progs/kfunc_call_fail.c
index 7e93f7fb1329..1ab85faaf8db 100644
--- a/tools/testing/selftests/bpf/progs/kfunc_call_fail.c
+++ b/tools/testing/selftests/bpf/progs/kfunc_call_fail.c
@@ -4,6 +4,8 @@
 #include <bpf/bpf_helpers.h>
 #include "../test_kmods/bpf_testmod_kfunc.h"
 
+static const char mem_len_rodata[] = "read-only data";
+
 static struct bpf_spin_lock kfunc_call_lock SEC(".data.A");
 
 SEC("?tc")
@@ -47,6 +49,14 @@ int kfunc_syscall_test_null_fail(struct syscall_test_args *args)
 	return 0;
 }
 
+SEC("?tc")
+int kfunc_call_test_mem_len_fail_readonly(struct __sk_buff *skb)
+{
+	bpf_kfunc_call_test_mem_len_pass1((void *)mem_len_rodata,
+					  sizeof(mem_len_rodata));
+	return 0;
+}
+
 SEC("?tc")
 int kfunc_call_test_get_mem_fail_rdonly(struct __sk_buff *skb)
 {
diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
index 8e6560c31e78..b944e2e186b6 100644
--- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c
+++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
@@ -5,6 +5,8 @@
 #include "bpf_misc.h"
 #include "../test_kmods/bpf_testmod_kfunc.h"
 
+static const char srcptr_rodata[] = "read-only source";
+
 static struct bpf_spin_lock kfunc_call_lock SEC(".data.A");
 
 SEC("tc")
@@ -208,6 +210,16 @@ int kfunc_call_test_pass(struct __sk_buff *skb)
 	return 0;
 }
 
+SEC("tc")
+int kfunc_call_test_srcptr(struct __sk_buff *skb)
+{
+	char stack_data[] = "read-write source";
+
+	bpf_kfunc_call_test_srcptr(srcptr_rodata, sizeof(srcptr_rodata));
+	bpf_kfunc_call_test_srcptr(stack_data, sizeof(stack_data));
+	return 0;
+}
+
 struct syscall_test_args {
 	__u8 data[16];
 	size_t size;
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index 6380f52f4dd2..5d72f94a8912 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -1024,6 +1024,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_arena_args5_test)
 BTF_ID_FLAGS(func, bpf_kfunc_arena_stack_arg_test)
 BTF_ID_FLAGS(func, bpf_kfunc_arena_mixed_test)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_pass1)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_srcptr)
 BTF_ID_FLAGS(func, bpf_kfunc_dynptr_test)
 BTF_ID_FLAGS(func, bpf_kfunc_nested_acquire_nonzero_offset_test, KF_ACQUIRE)
 BTF_ID_FLAGS(func, bpf_kfunc_nested_acquire_zero_offset_test, KF_ACQUIRE)
@@ -1527,6 +1528,10 @@ __bpf_kfunc void bpf_kfunc_call_test_mem_len_pass1(void *mem, int mem__sz)
 {
 }
 
+__bpf_kfunc void bpf_kfunc_call_test_srcptr(const void *src__srcptr, int src__sz)
+{
+}
+
 __bpf_kfunc void bpf_kfunc_call_test_mem_len_fail1(void *mem, int len)
 {
 }
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
index 3b810f1e438f..919c4c450ef1 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
@@ -198,6 +198,7 @@ void bpf_kfunc_call_test_release(struct prog_test_ref_kfunc *p) __ksym;
 void bpf_kfunc_call_test_ref(struct prog_test_ref_kfunc *p) __ksym;
 
 void bpf_kfunc_call_test_mem_len_pass1(void *mem, int len) __ksym;
+void bpf_kfunc_call_test_srcptr(const void *src__srcptr, int src__sz) __ksym;
 __u64 bpf_kfunc_arena_arg_test(__u64 *val__arena) __ksym;
 __u64 bpf_kfunc_arena_cap_test(__u64 *val__arena) __ksym;
 __u64 bpf_kfunc_arena_cap_nullable_test(__u64 *val__arena__nullable) __ksym;
-- 
2.54.0