[PATCH bpf] bpf: fix configuration-dependent BTF function references

[Thomas Weißschuh <linux@xxxxxxxxxxxxxx>]

These BTF functions are not available unconditionally,
only reference them when they are available.

Avoid the following build warnings:

  BTF     .tmp_vmlinux1.btf.o
btf_encoder__tag_kfunc: failed to find kfunc 'bpf_send_signal_task' in BTF
btf_encoder__tag_kfuncs: failed to tag kfunc 'bpf_send_signal_task'
  NM      .tmp_vmlinux1.syms
  KSYMS   .tmp_vmlinux1.kallsyms.S
  AS      .tmp_vmlinux1.kallsyms.o
  LD      .tmp_vmlinux2
  NM      .tmp_vmlinux2.syms
  KSYMS   .tmp_vmlinux2.kallsyms.S
  AS      .tmp_vmlinux2.kallsyms.o
  LD      vmlinux
  BTFIDS  vmlinux
WARN: resolve_btfids: unresolved symbol prog_test_ref_kfunc
WARN: resolve_btfids: unresolved symbol bpf_crypto_ctx
WARN: resolve_btfids: unresolved symbol bpf_send_signal_task
WARN: resolve_btfids: unresolved symbol bpf_modify_return_test_tp
WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_xdp
WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_skb

Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
 kernel/bpf/helpers.c  | 4 ++++
 kernel/bpf/verifier.c | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 751c150f9e1cd7f56e6a2b68a7ebb4ae89a30d2d..5edf5436a7804816b7dcf1bbef2624d71a985f20 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -3089,7 +3089,9 @@ BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_task_from_vpid, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_throw)
+#ifdef CONFIG_BPF_EVENTS
 BTF_ID_FLAGS(func, bpf_send_signal_task, KF_TRUSTED_ARGS)
+#endif
 BTF_KFUNCS_END(generic_btf_ids)
 
 static const struct btf_kfunc_id_set generic_kfunc_set = {
@@ -3135,7 +3137,9 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null)
 BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
 BTF_ID_FLAGS(func, bpf_dynptr_size)
 BTF_ID_FLAGS(func, bpf_dynptr_clone)
+#ifdef CONFIG_NET
 BTF_ID_FLAGS(func, bpf_modify_return_test_tp)
+#endif
 BTF_ID_FLAGS(func, bpf_wq_init)
 BTF_ID_FLAGS(func, bpf_wq_set_callback_impl)
 BTF_ID_FLAGS(func, bpf_wq_start)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5e541339b2f6d1870561033fd55cca7144db14bc..77bbf58418fee7533bce539c8e005d2342ee1a48 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5526,7 +5526,9 @@ static bool in_rcu_cs(struct bpf_verifier_env *env)
 
 /* Once GCC supports btf_type_tag the following mechanism will be replaced with tag check */
 BTF_SET_START(rcu_protected_types)
+#ifdef CONFIG_NET
 BTF_ID(struct, prog_test_ref_kfunc)
+#endif
 #ifdef CONFIG_CGROUPS
 BTF_ID(struct, cgroup)
 #endif
@@ -5534,7 +5536,9 @@ BTF_ID(struct, cgroup)
 BTF_ID(struct, bpf_cpumask)
 #endif
 BTF_ID(struct, task_struct)
+#ifdef CONFIG_CRYPTO
 BTF_ID(struct, bpf_crypto_ctx)
+#endif
 BTF_SET_END(rcu_protected_types)
 
 static bool rcu_protected_object(const struct btf *btf, u32 btf_id)
@@ -11529,8 +11533,10 @@ BTF_ID(func, bpf_rdonly_cast)
 BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add_impl)
 BTF_ID(func, bpf_rbtree_first)
+#ifdef CONFIG_NET
 BTF_ID(func, bpf_dynptr_from_skb)
 BTF_ID(func, bpf_dynptr_from_xdp)
+#endif
 BTF_ID(func, bpf_dynptr_slice)
 BTF_ID(func, bpf_dynptr_slice_rdwr)
 BTF_ID(func, bpf_dynptr_clone)
@@ -11558,8 +11564,10 @@ BTF_ID(func, bpf_rcu_read_unlock)
 BTF_ID(func, bpf_rbtree_remove)
 BTF_ID(func, bpf_rbtree_add_impl)
 BTF_ID(func, bpf_rbtree_first)
+#ifdef CONFIG_NET
 BTF_ID(func, bpf_dynptr_from_skb)
 BTF_ID(func, bpf_dynptr_from_xdp)
+#endif
 BTF_ID(func, bpf_dynptr_slice)
 BTF_ID(func, bpf_dynptr_slice_rdwr)
 BTF_ID(func, bpf_dynptr_clone)

---
base-commit: 5d287a7de3c95b78946e71d17d15ec9c87fffe7f
change-id: 20241212-bpf-cond-ids-9bfbc64dd77b

Best regards,
-- 
Thomas Weißschuh <linux@xxxxxxxxxxxxxx>