This patch allows bitfield access as a scalar. It currently limits
the access to sizeof(u64) and upto the end of the struct. It is needed
in a later bpf-tcp-cc example that reads bitfield from
inet_connection_sock and tcp_sock.
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
kernel/bpf/btf.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6e652643849b..011194831499 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3744,10 +3744,6 @@ int btf_struct_access(struct bpf_verifier_log *log,
}
for_each_member(i, t, member) {
- if (btf_member_bitfield_size(t, member))
- /* bitfields are not supported yet */
- continue;
-
/* offset of the field in bytes */
moff = btf_member_bit_offset(t, member) / 8;
if (off + size <= moff)
@@ -3757,6 +3753,15 @@ int btf_struct_access(struct bpf_verifier_log *log,
if (off < moff)
continue;
+ if (btf_member_bitfield_size(t, member)) {
+ if (off == moff &&
+ !(btf_member_bit_offset(t, member) % 8) &&
+ size <= sizeof(u64) &&
+ off + size <= t->size)
+ return SCALAR_VALUE;
+ continue;
+ }
+
/* type of the field */
mtype = btf_type_by_id(btf_vmlinux, member->type);
mname = __btf_name_by_offset(btf_vmlinux, member->name_off);
--
2.17.1
