net: filter: constify detection of pkt_type_offset

Currently we have 2 pkt_type_offset functions doing the same thing and
spread across the architecture files. Remove those and replace them
with a PKT_TYPE_OFFSET macro helper which gets the constant value from a
zero sized sk_buff member right in front of the bitfield with offsetof.
This new offset marker does not change size of struct sk_buff.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 26 deletions

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 0e97ccd29fe3..7edc08398c4a 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -765,27 +765,6 @@ static u64 jit_get_skb_w(struct sk_buff *skb, unsigned offset)
         return (u64)err << 32 | ntohl(ret);
 }
 
-#ifdef __BIG_ENDIAN_BITFIELD
-#define PKT_TYPE_MAX    (7 << 5)
-#else
-#define PKT_TYPE_MAX    7
-#endif
-static int pkt_type_offset(void)
-{
-        struct sk_buff skb_probe = {
-                .pkt_type = ~0,
-        };
-        u8 *ct = (u8 *)&skb_probe;
-        unsigned int off;
-
-        for (off = 0; off < sizeof(struct sk_buff); off++) {
-                if (ct[off] == PKT_TYPE_MAX)
-                        return off;
-        }
-        pr_err_once("Please fix pkt_type_offset(), as pkt_type couldn't be found\n");
-        return -1;
-}
-
 static int build_body(struct jit_ctx *ctx)
 {
         void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w};
@@ -1332,11 +1311,7 @@ jmp_cmp:
                 case BPF_ANC | SKF_AD_PKTTYPE:
                         ctx->flags |= SEEN_SKB;
 
-                        off = pkt_type_offset();
-
-                        if (off < 0)
-                                return -1;
-                        emit_load_byte(r_tmp, r_skb, off, ctx);
+                        emit_load_byte(r_tmp, r_skb, PKT_TYPE_OFFSET(), ctx);
                         /* Keep only the last 3 bits */
                         emit_andi(r_A, r_tmp, PKT_TYPE_MAX, ctx);
 #ifdef __BIG_ENDIAN_BITFIELD