[PATCH bpf-next v1 04/12] bpf: Check subprog scalar arguments in the common path

[Amery Hung <ameryhung@gmail.com>]

BPF subprogram scalar arguments are checked separately even though the
common argument checker enforces the same SCALAR_VALUE requirement.
Start the migration by routing the scalar branch through check_func_arg()
and update the verifier-log expectation.

Use the BTF parameter index for metadata and the ABI slot index for
register lookup. Route extra slots of by-value aggregates through
check_arg_extra_slot() so every occupied slot follows the common path.

Following patches can extend this guarded common-check branch as each
remaining BPF-subprogram-specific implementation is removed.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 kernel/bpf/verifier.c                         | 19 ++++++-------------
 .../selftests/bpf/progs/aggregate_arg_func.c  |  2 +-
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 65a1245e4edb..a84143285b3f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10871,10 +10871,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 		nslots = btf_arg_slots(t);
 
 		if (arg_type == ARG_SCALAR) {
-			if (reg->type != SCALAR_VALUE) {
-				bpf_log(log, "%s is not a scalar\n", reg_arg_name(env, argno));
-				return -EINVAL;
-			}
+			ret = check_func_arg(env, arg, slot, 0, &meta, env->insn_idx);
+			if (ret)
+				return ret;
 		} else if (arg_type & PTR_UNTRUSTED) {
 			/*
 			 * Anything is allowed for untrusted arguments, as these are
@@ -10964,15 +10963,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 		}
 
 		for (k = 1; k < nslots; k++) {
-			argno_t extra_argno = argno_from_arg(slot + k + 1);
-			struct bpf_reg_state *extra_reg;
-
-			extra_reg = get_func_arg_reg(caller, regs, slot + k);
-			if (extra_reg->type != SCALAR_VALUE) {
-				bpf_log(log, "%s is not a scalar\n",
-					reg_arg_name(env, extra_argno));
-				return -EINVAL;
-			}
+			ret = check_arg_extra_slot(env, caller, slot + k, &meta);
+			if (ret)
+				return ret;
 		}
 	}
 
diff --git a/tools/testing/selftests/bpf/progs/aggregate_arg_func.c b/tools/testing/selftests/bpf/progs/aggregate_arg_func.c
index d0a4f84a6fbf..2132b926a8f0 100644
--- a/tools/testing/selftests/bpf/progs/aggregate_arg_func.c
+++ b/tools/testing/selftests/bpf/progs/aggregate_arg_func.c
@@ -43,7 +43,7 @@ __naked int aggregate_arg_pair_asm(void)
 }
 
 SEC("tc")
-__failure __msg("R2 is not a scalar")
+__failure __msg("R2 type=fp expected=scalar")
 __naked int aggregate_arg_pair_ptr_fail(void)
 {
 	asm volatile (
-- 
2.52.0