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Message-Id: <3e68956a7e5b8bb9de226bfcc09092c6852a0a0a.1410523297.git.hannes@stressinduktion.org>
Date: Fri, 12 Sep 2014 14:04:43 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: netdev@...r.kernel.org
Cc: Eric Dumazet <eric.dumazet@...il.com>,
Markos Chandras <markos.chandras@...tec.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Daniel Borkmann <dborkman@...hat.com>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
Denis Kirjanov <kda@...ux-powerpc.org>
Subject: [PATCH net-next v2] 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@...il.com>
Cc: Markos Chandras <markos.chandras@...tec.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Daniel Borkmann <dborkman@...hat.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
v2) Incorporated Daniel's feedback. I first misinterpreted the feedback
as something not related to pkt_type_offset.
arch/mips/net/bpf_jit.c | 27 +--------------------------
arch/s390/net/bpf_jit_comp.c | 35 +----------------------------------
include/linux/skbuff.h | 10 ++++++++++
net/core/filter.c | 31 ++-----------------------------
4 files changed, 14 insertions(+), 89 deletions(-)
diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 0e97ccd..7edc083 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
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 555f5c7..c52ac77 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -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 @@ call_fn: /* lg %r1,<d(function)>(%r13) */
}
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;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 07c9fdd..756e3d0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -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,
diff --git a/net/core/filter.c b/net/core/filter.c
index dfc716f..601f28d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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++;
--
1.9.3
--
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