On 5/9/20 5:50 PM, Alexei Starovoitov wrote:
On Sat, May 09, 2020 at 10:59:12AM -0700, Yonghong Song wrote:
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index a2cfba89a8e1..c490fbde22d4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3790,7 +3790,10 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
return true;
/* this is a pointer to another type */
- info->reg_type = PTR_TO_BTF_ID;
+ if (off != 0 && prog->aux->btf_id_or_null_non0_off)
+ info->reg_type = PTR_TO_BTF_ID_OR_NULL;
+ else
+ info->reg_type = PTR_TO_BTF_ID;
I think the verifier should be smarter than this.
It's too specific and inflexible. All ctx fields of bpf_iter execpt first
will be such ? let's figure out a different way to tell verifier about this.
How about using typedef with specific suffix? Like:
typedef struct bpf_map *bpf_map_or_null;
struct bpf_iter__bpf_map {
struct bpf_iter_meta *meta;
bpf_map_or_null map;
};
or use a union with specific second member? Like:
struct bpf_iter__bpf_map {
struct bpf_iter_meta *meta;
union {
struct bpf_map *map;
long null;
};
};
I have an alternative approach to refactor this for future
support for map elements as well.
For example, for bpf_map_elements iterator the prog context type
can be
struct bpf_iter_bpf_map_elem {
struct bpf_iter_meta *meta;
strruct bpf_map *map;
<key type> *key;
<value type> *val;
};
target will pass the following information to bpf_iter registration:
arg 1: PTR_TO_BTF_ID
arg 2: PTR_TO_BTF_ID_OR_NULL
arg 3: PTR_TO_BUFFER
arg 4: PTR_TO_BUFFER
verifier will retrieve the reg_type from target.
