bpf: reuse btf_prepare_func_args() check for main program BTF validation

Instead of btf_check_subprog_arg_match(), use btf_prepare_func_args()
logic to validate "trustworthiness" of main BPF program's BTF information,
if it is present.

We ignored results of original BTF check anyway, often times producing
confusing and ominously-sounding "reg type unsupported for arg#0
function" message, which has no apparent effect on program correctness
and verification process.

All the -EFAULT returning sanity checks are already performed in
check_btf_info_early(), so there is zero reason to have this duplication
of logic between btf_check_subprog_call() and btf_check_subprog_arg_match().
Dropping btf_check_subprog_arg_match() simplifies
btf_check_func_arg_match() further removing `bool processing_call` flag.

One subtle bit that was done by btf_check_subprog_arg_match() was
potentially marking main program's BTF as unreliable. We do this
explicitly now with a dedicated simple check, preserving the original
behavior, but now based on well factored btf_prepare_func_args() logic.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231215011334.2307144-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 4 insertions, 4 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/log_fixup.c b/tools/testing/selftests/bpf/prog_tests/log_fixup.c
index effd78b2a657..7a3fa2ff567b 100644
--- a/tools/testing/selftests/bpf/prog_tests/log_fixup.c
+++ b/tools/testing/selftests/bpf/prog_tests/log_fixup.c
@@ -169,9 +169,9 @@ void test_log_fixup(void)
 	if (test__start_subtest("bad_core_relo_trunc_none"))
 		bad_core_relo(0, TRUNC_NONE /* full buf */);
 	if (test__start_subtest("bad_core_relo_trunc_partial"))
-		bad_core_relo(300, TRUNC_PARTIAL /* truncate original log a bit */);
+		bad_core_relo(280, TRUNC_PARTIAL /* truncate original log a bit */);
 	if (test__start_subtest("bad_core_relo_trunc_full"))
-		bad_core_relo(210, TRUNC_FULL  /* truncate also libbpf's message patch */);
+		bad_core_relo(220, TRUNC_FULL  /* truncate also libbpf's message patch */);
 	if (test__start_subtest("bad_core_relo_subprog"))
 		bad_core_relo_subprog();
 	if (test__start_subtest("missing_map"))
diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
index 0fa564a5cc5b..9fe9c4a4e8f6 100644
--- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
@@ -78,7 +78,7 @@ int BPF_PROG(cgrp_kfunc_acquire_fp, struct cgroup *cgrp, const char *path)
 }
 
 SEC("kretprobe/cgroup_destroy_locked")
-__failure __msg("reg type unsupported for arg#0 function")
+__failure __msg("calling kernel function bpf_cgroup_acquire is not allowed")
 int BPF_PROG(cgrp_kfunc_acquire_unsafe_kretprobe, struct cgroup *cgrp)
 {
 	struct cgroup *acquired;
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index dcdea3127086..ad88a3796ddf 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -248,7 +248,7 @@ int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 cl
 }
 
 SEC("lsm/task_free")
-__failure __msg("reg type unsupported for arg#0 function")
+__failure __msg("R1 must be a rcu pointer")
 int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
 {
 	struct task_struct *acquired;