Commit b4fe0ec8 authored Jun 23, 2014 by Markos Chandras Committed by Ralf Baechle Jun 26, 2014

MIPS: bpf: Fix PKT_TYPE case for big-endian cores



The skb->pkt_type field is defined as follows:

u8 pkt_type:3,
   fclone:2,
   ipvs_property:1,
   peeked:1,
   nf_trace:1

resulting to the following layout in big-endian systems

[pkt_type][fclone][ipvs_propery][peeked][nf_trace]
^                                                ^
|                                                |
LSB                                             MSB

As a result, the existing code did not work because it was trying to
match pkt_type == 7 whereas in reality it is 7<<5 on big-endian
systems.

This has been fixed in the interpreter in
0dcceabb
"net: filter: fix SKF_AD_PKTTYPE extension on big-endian"

The fix is to look for 7<<5 on big-endian systems for the pkt_type
field, and shift by 5 so the packet type will be at the lower 3 bits
of the A register.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7132/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

parent 95782bf4

arch/mips/net/bpf_jit.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -751,13 +751,17 @@ 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,
		};
		char ct = (char )&skb_probe;
		u8 ct = (u8 )&skb_probe;
		unsigned int off;

		for (off = 0; off < sizeof(struct sk_buff); off++) {
		@@ -1320,6 +1324,10 @@ jmp_cmp:
		emit_load_byte(r_tmp, r_skb, off, ctx);
		/* Keep only the last 3 bits */
		emit_andi(r_A, r_tmp, PKT_TYPE_MAX, ctx);
		#ifdef __BIG_ENDIAN_BITFIELD
		/* Get the actual packet type to the lower 3 bits */
		emit_srl(r_A, r_A, 5, ctx);
		#endif
		break;
		case BPF_ANC \| SKF_AD_QUEUE:
		ctx->flags \|= SEEN_SKB \| SEEN_A;

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