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authorEric Dumazet <edumazet@google.com>2013-01-30 17:51:44 -0800
committerDavid S. Miller <davem@davemloft.net>2013-01-30 22:38:34 -0500
commit3b58908a92e00840bcd9050808f3dc86fd547029 (patch)
tree3d3a2f97da69a5681a83cebf46e816e40670e34b
parent45acd3a0a18c5692b34ee9091858c6f6c7b5d4a8 (diff)
downloadlinux-3b58908a92e00840bcd9050808f3dc86fd547029.tar.bz2
x86: bpf_jit_comp: add pkt_type support
Supporting access to skb->pkt_type is a bit tricky if we want to have a generic code, allowing pkt_type to be moved in struct sk_buff pkt_type is a bit field, so compiler cannot really help us to find its offset. Let's use a helper for this : It will throw a one time message if pkt_type no longer starts at a byte boundary or is no longer a 3bit field. Reported-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Maciej Żenczykowski <maze@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--arch/x86/net/bpf_jit_comp.c40
1 files changed, 39 insertions, 1 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index d11a47099d33..3cbe45381bbb 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1,6 +1,6 @@
/* bpf_jit_comp.c : BPF JIT compiler
*
- * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com)
+ * Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -124,6 +124,26 @@ static inline void bpf_flush_icache(void *start, void *end)
#define CHOOSE_LOAD_FUNC(K, func) \
((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
+/* Helper to find the offset of pkt_type in sk_buff
+ * We want to make sure its still a 3bit field starting at a byte boundary.
+ */
+#define PKT_TYPE_MAX 7
+static int pkt_type_offset(void)
+{
+ struct sk_buff skb_probe = {
+ .pkt_type = ~0,
+ };
+ char *ct = (char *)&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;
+}
+
void bpf_jit_compile(struct sk_filter *fp)
{
u8 temp[64];
@@ -216,6 +236,7 @@ void bpf_jit_compile(struct sk_filter *fp)
case BPF_S_ANC_VLAN_TAG:
case BPF_S_ANC_VLAN_TAG_PRESENT:
case BPF_S_ANC_QUEUE:
+ case BPF_S_ANC_PKTTYPE:
case BPF_S_LD_W_ABS:
case BPF_S_LD_H_ABS:
case BPF_S_LD_B_ABS:
@@ -536,6 +557,23 @@ void bpf_jit_compile(struct sk_filter *fp)
EMIT3(0x83, 0xe0, 0x01); /* and $0x1,%eax */
}
break;
+ case BPF_S_ANC_PKTTYPE:
+ {
+ int off = pkt_type_offset();
+
+ if (off < 0)
+ goto out;
+ if (is_imm8(off)) {
+ /* movzbl off8(%rdi),%eax */
+ EMIT4(0x0f, 0xb6, 0x47, off);
+ } else {
+ /* movbl off32(%rdi),%eax */
+ EMIT3(0x0f, 0xb6, 0x87);
+ EMIT(off, 4);
+ }
+ EMIT3(0x83, 0xe0, PKT_TYPE_MAX); /* and $0x7,%eax */
+ break;
+ }
case BPF_S_LD_W_ABS:
func = CHOOSE_LOAD_FUNC(K, sk_load_word);
common_load: seen |= SEEN_DATAREF;