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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>
This commit is contained in:
Hannes Frederic Sowa 2014-09-12 14:04:43 +02:00 committed by David S. Miller
parent ac7a04c33d
commit 233577a220
4 changed files with 14 additions and 89 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
arch/mips/net/bpf_jit.c
View File

@ -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 @@ static int build_body(struct jit_ctx *ctx)
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

35
arch/s390/net/bpf_jit_comp.c
View File

@ -227,37 +227,6 @@ static void bpf_jit_epilogue(struct bpf_jit *jit)
EMIT2(0x07fe);
}
/* Helper to find the offset of pkt_type in sk_buff
* Make sure its still a 3bit field starting at the MSBs within a byte.
*/
#define PKT_TYPE_MAX 0xe0
static int pkt_type_offset;
static int __init bpf_pkt_type_offset_init(void)
{
struct sk_buff skb_probe = {
.pkt_type = ~0,
};
char *ct = (char *)&skb_probe;
int off;
pkt_type_offset = -1;
for (off = 0; off < sizeof(struct sk_buff); off++) {
if (!ct[off])
continue;
if (ct[off] == PKT_TYPE_MAX)
pkt_type_offset = off;
else {
/* Found non matching bit pattern, fix needed. */
WARN_ON_ONCE(1);
pkt_type_offset = -1;
return -1;
}
}
return 0;
}
device_initcall(bpf_pkt_type_offset_init);
/*
* make sure we dont leak kernel information to user
*/
@ -757,12 +726,10 @@ load_abs: if ((int) K < 0)
}
break;
case BPF_ANC | SKF_AD_PKTTYPE:
if (pkt_type_offset < 0)
goto out;
/* lhi %r5,0 */
EMIT4(0xa7580000);
/* ic %r5,<d(pkt_type_offset)>(%r2) */
EMIT4_DISP(0x43502000, pkt_type_offset);
EMIT4_DISP(0x43502000, PKT_TYPE_OFFSET());
/* srl %r5,5 */
EMIT4_DISP(0x88500000, 5);
break;

10
include/linux/skbuff.h
View File

@ -548,6 +548,16 @@ struct sk_buff {
ip_summed:2,
nohdr:1,
nfctinfo:3;
/* if you move pkt_type around you also must adapt those constants */
#ifdef __BIG_ENDIAN_BITFIELD
#define PKT_TYPE_MAX (7 << 5)
#else
#define PKT_TYPE_MAX 7
#endif
#define PKT_TYPE_OFFSET() offsetof(struct sk_buff, __pkt_type_offset)
__u8 __pkt_type_offset[0];
__u8 pkt_type:3,
fclone:2,
ipvs_property:1,

31
net/core/filter.c
View File

@ -87,30 +87,6 @@ int sk_filter(struct sock *sk, struct sk_buff *skb)
}
EXPORT_SYMBOL(sk_filter);
/* Helper to find the offset of pkt_type in sk_buff structure. We want
* to make sure its still a 3bit field starting at a byte boundary;
* taken from arch/x86/net/bpf_jit_comp.c.
*/
#ifdef __BIG_ENDIAN_BITFIELD
#define PKT_TYPE_MAX (7 << 5)
#else
#define PKT_TYPE_MAX 7
#endif
static unsigned 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 %s, as pkt_type couldn't be found!\n", __func__);
return -1;
}
static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
return skb_get_poff((struct sk_buff *)(unsigned long) ctx);
@ -190,11 +166,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
break;
case SKF_AD_OFF + SKF_AD_PKTTYPE:
*insn = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,
pkt_type_offset());
if (insn->off < 0)
return false;
insn++;
*insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,
PKT_TYPE_OFFSET());
*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
insn++;