[PATCH v2 bpf-next 2/4] bpf: consider CONST_PTR_TO_MAP as trusted pointer to struct bpf_map

[Anton Protopopov]

Add the BTF id of struct bpf_map to the reg2btf_ids array. This makes the
values of the CONST_PTR_TO_MAP type to be considered as trusted by kfuncs.
This, in turn, allows users to execute trusted kfuncs which accept `struct
bpf_map *` arguments from non-tracing programs.

While exporting the btf_bpf_map_id variable, save some bytes by defining
it as BTF_ID_LIST_GLOBAL_SINGLE (which is u32[1]) and not as BTF_ID_LIST
(which is u32[64]).

Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
---
 include/linux/btf_ids.h | 1 +
 kernel/bpf/map_iter.c   | 3 +--
 kernel/bpf/verifier.c   | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index 00950cc03bff..a3462a9b8e18 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE,
 extern u32 btf_tracing_ids[];
 extern u32 bpf_cgroup_btf_id[];
 extern u32 bpf_local_storage_map_btf_id[];
+extern u32 btf_bpf_map_id[];
 
 #endif
diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index d06d3b7150e5..b67996147895 100644
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = {
 	.show	= bpf_map_seq_show,
 };
 
-BTF_ID_LIST(btf_bpf_map_id)
-BTF_ID(struct, bpf_map)
+BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
 
 static const struct bpf_iter_seq_info bpf_map_seq_info = {
 	.seq_ops		= &bpf_map_seq_ops,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 05123feab378..803b91135ca0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5419,6 +5419,7 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
 	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
 #endif
+	[CONST_PTR_TO_MAP] = btf_bpf_map_id,
 };
 
 static bool is_trusted_reg(const struct bpf_reg_state *reg)
-- 
2.34.1