diff options
| author | Martin KaFai Lau <kafai@fb.com> | 2022-03-09 12:05:02 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-03-11 00:57:05 +0300 |
| commit | 9d90db97e4d4537c82a5ee476b1c13553e487f28 (patch) | |
| tree | 5272251f183d4a30a00f500ae407adce4319384e /net/core | |
| parent | 539de9328e3ab444efe51ddc7416ce2a3f0f23b2 (diff) | |
| download | linux-9d90db97e4d4537c82a5ee476b1c13553e487f28.tar.xz | |
bpf: Simplify insn rewrite on BPF_WRITE __sk_buff->tstamp
BPF_JMP32_IMM(BPF_JSET) is used to save a BPF_ALU32_IMM(BPF_AND).
The skb->tc_at_ingress and skb->mono_delivery_time are at the same
offset, so only one BPF_LDX_MEM(BPF_B) is needed.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220309090502.3711982-1-kafai@fb.com
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 26 |
1 files changed, 14 insertions, 12 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 2c83d1f38704..f914e4b13b18 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8990,25 +8990,27 @@ static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog, __u8 skb_reg = si->dst_reg; #ifdef CONFIG_NET_CLS_ACT + /* If the delivery_time_type is read, + * the bpf prog is aware the tstamp could have delivery time. + * Thus, write skb->tstamp as is if delivery_time_access is true. + * Otherwise, writing at ingress will have to clear the + * mono_delivery_time bit also. + */ if (!prog->delivery_time_access) { __u8 tmp_reg = BPF_REG_AX; *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, PKT_VLAN_PRESENT_OFFSET); - *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK); - *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3); - /* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp. - * Clear the skb->mono_delivery_time. - */ - *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, - PKT_VLAN_PRESENT_OFFSET); - *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, - ~SKB_MONO_DELIVERY_TIME_MASK); - *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, - PKT_VLAN_PRESENT_OFFSET); + /* Writing __sk_buff->tstamp as ingress, goto <clear> */ + *insn++ = BPF_JMP32_IMM(BPF_JSET, tmp_reg, TC_AT_INGRESS_MASK, 1); + /* goto <store> */ + *insn++ = BPF_JMP_A(2); + /* <clear>: mono_delivery_time */ + *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, ~SKB_MONO_DELIVERY_TIME_MASK); + *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg, PKT_VLAN_PRESENT_OFFSET); } #endif - /* skb->tstamp = tstamp */ + /* <store>: skb->tstamp = tstamp */ *insn++ = BPF_STX_MEM(BPF_DW, skb_reg, value_reg, offsetof(struct sk_buff, tstamp)); return insn; |