[PATCH bpf-next v2 04/12] bpf: Support __int128 as a by-value function argument

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

A 128-bit integer follows the same calling convention as a 16-byte
by-value struct: LLVM emits it as a 16-byte BTF_KIND_INT and passes it in
two consecutive argument registers. So a __int128 gets its two slots.

The test added at the start of the series, which recorded the wrong
register map as an R4 !read_ok rejection, now passes and is flipped to
__success.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 kernel/bpf/btf.c                                        | 9 +++------
 tools/testing/selftests/bpf/progs/verifier_int128_arg.c | 7 +------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4502b888b668..baa370f3f331 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8252,11 +8252,7 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
 			bpf_log(log, "arg#%d has pointer tag, but is not a pointer type\n", i);
 			return -EINVAL;
 		}
-		if (btf_type_is_int(t) || btf_is_any_enum(t)) {
-			sub->args[slots_used++].arg_type = ARG_ANYTHING;
-			continue;
-		}
-		if (btf_type_is_struct(t)) {
+		if (btf_type_is_int(t) || btf_is_any_enum(t) || btf_type_is_struct(t)) {
 			u32 nslots;
 
 			if (!t->size || t->size > 2 * BPF_REG_SIZE) {
@@ -8268,7 +8264,8 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog)
 					i, btf_type_str(t), tname, t->size, 2 * BPF_REG_SIZE);
 				return -EINVAL;
 			}
-			if (!btf_struct_is_composed_of(env, btf, t, BTF_MEMBER_SCALAR)) {
+			if (btf_type_is_struct(t) &&
+			    !btf_struct_is_composed_of(env, btf, t, BTF_MEMBER_SCALAR)) {
 				if (!is_global)
 					return -EINVAL;
 				bpf_log(log, "Arg#%d type %s in %s() is not composed of scalars\n",
diff --git a/tools/testing/selftests/bpf/progs/verifier_int128_arg.c b/tools/testing/selftests/bpf/progs/verifier_int128_arg.c
index 419851f2d8d0..044fc4a80055 100644
--- a/tools/testing/selftests/bpf/progs/verifier_int128_arg.c
+++ b/tools/testing/selftests/bpf/progs/verifier_int128_arg.c
@@ -15,12 +15,7 @@ __noinline __u64 take_i128_global(int a, u128 v, int c)
 }
 
 SEC("tc")
-/*
- * The verifier counts one argument register for the __int128 and marks only
- * R1 through R3 at the entry of take_i128_global(), while the compiler passed
- * a in R1, v in R2:R3 and c in R4.
- */
-__failure __msg("R4 !read_ok")
+__success __retval(0)
 int aggregate_arg_int128_c_test(struct __sk_buff *skb)
 {
 	__u64 a = skb->len ^ MIX_A;
-- 
2.53.0-Meta