[PATCH bpf-next v2 08/11] bpf: Enable and verify btf_field arrays.

[Kui-Feng Lee <thinker.li@gmail.com>]

Set the value of "nelems" of a btf_field with the length of the flattened
array if the btf_field represents an array. The "size" is the size of the
entire array rather than the size of an individual element.

Once "nelems" and "size" reflects the length and size of arrays
respectively, it allows BPF programs to easily declare multiple kptr,
btf_rb_root, or btf_list_head in a global array.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
 kernel/bpf/btf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6fb482789f8e..ae17d3996843 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3835,7 +3835,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 	rec->timer_off = -EINVAL;
 	rec->refcount_off = -EINVAL;
 	for (i = 0; i < cnt; i++) {
-		field_type_size = btf_field_type_size(info_arr[i].type);
+		field_type_size = btf_field_type_size(info_arr[i].type) * info_arr[i].nelems;
 		if (info_arr[i].off + field_type_size > value_size) {
 			WARN_ONCE(1, "verifier bug off %d size %d", info_arr[i].off, value_size);
 			ret = -EFAULT;
@@ -3851,7 +3851,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
 		rec->fields[i].offset = info_arr[i].off;
 		rec->fields[i].type = info_arr[i].type;
 		rec->fields[i].size = field_type_size;
-		rec->fields[i].nelems = 1;
+		rec->fields[i].nelems = info_arr[i].nelems;
 
 		switch (info_arr[i].type) {
 		case BPF_SPIN_LOCK:
-- 
2.34.1