netdev - [PATCH bpf-next v2 04/11] bpf: Support bitfield read access in btf_struct

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Date:   Fri, 20 Dec 2019 22:26:04 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     <bpf@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>, <kernel-team@...com>,
        <netdev@...r.kernel.org>
Subject: [PATCH bpf-next v2 04/11] bpf: Support bitfield read access in btf_struct_access

This patch allows bitfield access as a scalar.

Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/btf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6e652643849b..da73b63acfc5 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 +3753,12 @@ int btf_struct_access(struct bpf_verifier_log *log,
 		if (off < moff)
 			continue;
 
+		if (btf_member_bitfield_size(t, member)) {
+			if (off == moff && 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