[PATCH bpf-next v2 08/10] selftests/bpf: Check the member named for an unsupported kfunc return type

[Yonghong Song <yonghong.song@linux.dev>]

Cover the member a rejected by-value kfunc return type is blamed on.
The existing case for a struct carrying a pointer now also checks that
the verifier names the member, and two cases are added: a pointer inside
a nested member struct, which has to be named by its path rather than by
its own name, and a type nested deeper than the walk descends, which has
no single member to blame and reports the depth instead.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 .../selftests/bpf/progs/aggregate_ret_kfunc.c | 34 +++++++++++++++++++
 .../selftests/bpf/test_kmods/bpf_testmod.c    | 16 +++++++++
 .../bpf/test_kmods/bpf_testmod_kfunc.h        | 21 ++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/aggregate_ret_kfunc.c b/tools/testing/selftests/bpf/progs/aggregate_ret_kfunc.c
index f10e5cf6fd89..e9c82df8efb2 100644
--- a/tools/testing/selftests/bpf/progs/aggregate_ret_kfunc.c
+++ b/tools/testing/selftests/bpf/progs/aggregate_ret_kfunc.c
@@ -18,6 +18,8 @@ void __kfunc_btf_root(void)
 	: "r"(&bpf_kfunc_call_test_i128),
 	  "r"(&bpf_kfunc_call_test_ret_fastcall),
 	  "r"(&bpf_kfunc_call_test_ret_ptr),
+	  "r"(&bpf_kfunc_call_test_ret_nested),
+	  "r"(&bpf_kfunc_call_test_ret_deep),
 	  "r"(&bpf_kfunc_call_test_ret_ii),
 	  "r"(&bpf_kfunc_call_test_ret_big));
 }
@@ -72,6 +74,7 @@ __naked int aggregate_ret_kfunc_fastcall_fail(void)
 SEC("tc")
 __arch_x86_64 __arch_arm64
 __failure __msg("is not composed of scalars or arena pointers")
+__msg("member 'p' has type PTR")
 __naked int aggregate_ret_kfunc_ptr_fail(void)
 {
 	asm volatile (
@@ -84,6 +87,37 @@ __naked int aggregate_ret_kfunc_ptr_fail(void)
 	: __clobber_all);
 }
 
+SEC("tc")
+__arch_x86_64 __arch_arm64
+__failure __msg("is not composed of scalars or arena pointers")
+__msg("member 'in.p' has type PTR")
+__naked int aggregate_ret_kfunc_nested_ptr_fail(void)
+{
+	asm volatile (
+	"r1 = 0;"
+	"call %[bpf_kfunc_call_test_ret_nested];"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm(bpf_kfunc_call_test_ret_nested)
+	: __clobber_all);
+}
+
+SEC("tc")
+__arch_x86_64 __arch_arm64
+__failure __msg("max struct nesting depth exceeded")
+__naked int aggregate_ret_kfunc_too_deep_fail(void)
+{
+	asm volatile (
+	"r1 = 0;"
+	"call %[bpf_kfunc_call_test_ret_deep];"
+	"r0 = 0;"
+	"exit;"
+	:
+	: __imm(bpf_kfunc_call_test_ret_deep)
+	: __clobber_all);
+}
+
 SEC("tc")
 __arch_x86_64 __arch_arm64
 __failure __msg("R2 !read_ok")
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index 850cf4f830c4..76acbe29054a 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -981,6 +981,20 @@ __bpf_kfunc struct prog_test_ret_ptr bpf_kfunc_call_test_ret_ptr(u64 tag)
 	return r;
 }
 
+__bpf_kfunc struct prog_test_ret_nested bpf_kfunc_call_test_ret_nested(u64 tag)
+{
+	struct prog_test_ret_nested r = { .in = { .p = NULL }, .tag = tag };
+
+	return r;
+}
+
+__bpf_kfunc struct prog_test_ret_deep bpf_kfunc_call_test_ret_deep(u64 v)
+{
+	struct prog_test_ret_deep r = { .l1 = { .l2 = { .l3 = { .l4 = { .v = v } } } } };
+
+	return r;
+}
+
 __bpf_kfunc struct prog_test_ret_ii bpf_kfunc_call_test_ret_ii(int a, int b)
 {
 	struct prog_test_ret_ii r = { .a = a, .b = b };
@@ -1539,6 +1553,8 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_i128)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_pair)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_fastcall, KF_FASTCALL)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_ptr)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_nested)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_deep)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_ii)
 #endif
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_ret_big)
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 65e693ada736..52227129a49e 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h
@@ -70,6 +70,25 @@ struct prog_test_ret_ptr {	/* 16 bytes: contains a pointer */
 	__u64 tag;
 };
 
+struct prog_test_ret_nested {	/* 16 bytes: the pointer hides one level down */
+	struct {
+		void *p;
+	} in;
+	__u64 tag;
+};
+
+struct prog_test_ret_deep {	/* 8 bytes, but nested past the 4-level walk limit */
+	struct {
+		struct {
+			struct {
+				struct {
+					__u64 v;
+				} l4;
+			} l3;
+		} l2;
+	} l1;
+};
+
 struct prog_test_ret_big {	/* 24 bytes: too large for R0:R2 */
 	__u64 a;
 	__u64 b;
@@ -159,6 +178,8 @@ struct prog_test_ret_pair bpf_kfunc_call_test_ret_pair(__u64 a, __u64 b) __ksym;
 struct prog_test_ret_pair bpf_kfunc_call_test_ret_fastcall(__u64 a, __u64 b) __ksym;
 struct prog_test_ret_ii bpf_kfunc_call_test_ret_ii(int a, int b) __ksym;
 struct prog_test_ret_ptr bpf_kfunc_call_test_ret_ptr(__u64 tag) __ksym;
+struct prog_test_ret_nested bpf_kfunc_call_test_ret_nested(__u64 tag) __ksym;
+struct prog_test_ret_deep bpf_kfunc_call_test_ret_deep(__u64 v) __ksym;
 struct prog_test_ret_big bpf_kfunc_call_test_ret_big(void) __ksym;
 __u64 bpf_kfunc_call_stack_arg(__u64 a, __u64 b, __u64 c, __u64 d,
 			       __u64 e, __u64 f, __u64 g, __u64 h,
-- 
2.53.0-Meta