From 4e10df9a60d96ced321dd2af71da558c6b750078 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Mon, 20 Jul 2015 20:34:18 -0700 Subject: bpf: introduce bpf_skb_vlan_push/pop() helpers Allow eBPF programs attached to TC qdiscs call skb_vlan_push/pop via helper functions. These functions may change skb->data/hlen which are cached by some JITs to improve performance of ld_abs/ld_ind instructions. Therefore JITs need to recognize bpf_skb_vlan_push/pop() calls, re-compute header len and re-cache skb->data/hlen back into cpu registers. Note, skb->data/hlen are not directly accessible from the programs, so any changes to skb->data done either by these helpers or by other TC actions are safe. eBPF JIT supported by three architectures: - arm64 JIT is using bpf_load_pointer() without caching, so it's ok as-is. - x64 JIT re-caches skb->data/hlen unconditionally after vlan_push/pop calls (experiments showed that conditional re-caching is slower). - s390 JIT falls back to interpreter for now when bpf_skb_vlan_push() is present in the program (re-caching is tbd). These helpers allow more scalable handling of vlan from the programs. Instead of creating thousands of vlan netdevs on top of eth0 and attaching TC+ingress+bpf to all of them, the program can be attached to eth0 directly and manipulate vlans as necessary. Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller --- arch/s390/net/bpf_jit_comp.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/s390/net') diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index fee782acc2ee..79c731e8d178 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -973,6 +973,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i */ const u64 func = (u64)__bpf_call_base + imm; + if (bpf_helper_changes_skb_data((void *)func)) + /* TODO reload skb->data, hlen */ + return -1; + REG_SET_SEEN(BPF_REG_5); jit->seen |= SEEN_FUNC; /* lg %w1,(%l) */ -- cgit v1.2.3