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Mon, 7 Dec 2020 11:34:31 -0500 From: Lorenzo Bianconi Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, shayagr@amazon.com, sameehj@amazon.com, john.fastabend@gmail.com, dsahern@kernel.org, brouer@redhat.com, echaudro@redhat.com, lorenzo.bianconi@redhat.com, jasowang@redhat.com Subject: [PATCH v5 bpf-next 13/14] bpf: add new frame_length field to the XDP ctx Date: Mon, 7 Dec 2020 17:32:42 +0100 Message-Id: <0547d6f752e325f56a8e5f6466b50e81ff29d65f.1607349924.git.lorenzo@kernel.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eelco Chaudron This patch adds a new field to the XDP context called frame_length, which will hold the full length of the packet, including fragments if existing. eBPF programs can determine if fragments are present using something like: if (ctx->data_end - ctx->data < ctx->frame_length) { /* Fragements exists. /* } Signed-off-by: Eelco Chaudron Signed-off-by: Lorenzo Bianconi --- include/net/xdp.h | 22 +++++++++ include/uapi/linux/bpf.h | 1 + kernel/bpf/verifier.c | 2 +- net/core/filter.c | 83 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 1 + 5 files changed, 108 insertions(+), 1 deletion(-) diff --git a/include/net/xdp.h b/include/net/xdp.h index 09078ab6644c..e54d733c90ed 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -73,8 +73,30 @@ struct xdp_buff { void *data_hard_start; struct xdp_rxq_info *rxq; struct xdp_txq_info *txq; + /* If any of the bitfield lengths for frame_sz or mb below change, + * make sure the defines here are also updated! + */ +#ifdef __BIG_ENDIAN_BITFIELD +#define MB_SHIFT 0 +#define MB_MASK 0x00000001 +#define FRAME_SZ_SHIFT 1 +#define FRAME_SZ_MASK 0xfffffffe +#else +#define MB_SHIFT 31 +#define MB_MASK 0x80000000 +#define FRAME_SZ_SHIFT 0 +#define FRAME_SZ_MASK 0x7fffffff +#endif +#define FRAME_SZ_OFFSET() offsetof(struct xdp_buff, __u32_bit_fields_offset) +#define MB_OFFSET() offsetof(struct xdp_buff, __u32_bit_fields_offset) + /* private: */ + u32 __u32_bit_fields_offset[0]; + /* public: */ u32 frame_sz:31; /* frame size to deduce data_hard_end/reserved tailroom*/ u32 mb:1; /* xdp non-linear buffer */ + + /* Temporary registers to make conditional access/stores possible. */ + u64 tmp_reg[2]; }; /* Reserve memory area at end-of data area. diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 30b477a26482..62c50ab28ea9 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4380,6 +4380,7 @@ struct xdp_md { __u32 rx_queue_index; /* rxq->queue_index */ __u32 egress_ifindex; /* txq->dev->ifindex */ + __u32 frame_length; }; /* DEVMAP map-value layout diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 93def76cf32b..c50caea29fa2 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10526,7 +10526,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) const struct bpf_verifier_ops *ops = env->ops; int i, cnt, size, ctx_field_size, delta = 0; const int insn_cnt = env->prog->len; - struct bpf_insn insn_buf[16], *insn; + struct bpf_insn insn_buf[32], *insn; u32 target_size, size_default, off; struct bpf_prog *new_prog; enum bpf_access_type type; diff --git a/net/core/filter.c b/net/core/filter.c index 4c4882d4d92c..278640db9e0a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8908,6 +8908,7 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, struct bpf_insn *insn_buf, struct bpf_prog *prog, u32 *target_size) { + int ctx_reg, dst_reg, scratch_reg; struct bpf_insn *insn = insn_buf; switch (si->off) { @@ -8954,6 +8955,88 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg, offsetof(struct net_device, ifindex)); break; + case offsetof(struct xdp_md, frame_length): + /* Need tmp storage for src_reg in case src_reg == dst_reg, + * and a scratch reg */ + scratch_reg = BPF_REG_9; + dst_reg = si->dst_reg; + + if (dst_reg == scratch_reg) + scratch_reg--; + + ctx_reg = (si->src_reg == si->dst_reg) ? scratch_reg - 1 : si->src_reg; + while (dst_reg == ctx_reg || scratch_reg == ctx_reg) + ctx_reg--; + + /* Save scratch registers */ + if (ctx_reg != si->src_reg) { + *insn++ = BPF_STX_MEM(BPF_DW, si->src_reg, ctx_reg, + offsetof(struct xdp_buff, + tmp_reg[1])); + + *insn++ = BPF_MOV64_REG(ctx_reg, si->src_reg); + } + + *insn++ = BPF_STX_MEM(BPF_DW, ctx_reg, scratch_reg, + offsetof(struct xdp_buff, tmp_reg[0])); + + /* What does this code do? + * dst_reg = 0 + * + * if (!ctx_reg->mb) + * goto no_mb: + * + * dst_reg = (struct xdp_shared_info *)xdp_data_hard_end(xdp) + * dst_reg = dst_reg->data_length + * + * NOTE: xdp_data_hard_end() is xdp->hard_start + + * xdp->frame_sz - sizeof(shared_info) + * + * no_mb: + * dst_reg += ctx_reg->data_end - ctx_reg->data + */ + *insn++ = BPF_MOV64_IMM(dst_reg, 0); + + *insn++ = BPF_LDX_MEM(BPF_W, scratch_reg, ctx_reg, MB_OFFSET()); + *insn++ = BPF_ALU32_IMM(BPF_AND, scratch_reg, MB_MASK); + *insn++ = BPF_JMP_IMM(BPF_JEQ, scratch_reg, 0, 7); /*goto no_mb; */ + + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, + data_hard_start), + dst_reg, ctx_reg, + offsetof(struct xdp_buff, data_hard_start)); + *insn++ = BPF_LDX_MEM(BPF_W, scratch_reg, ctx_reg, + FRAME_SZ_OFFSET()); + *insn++ = BPF_ALU32_IMM(BPF_AND, scratch_reg, FRAME_SZ_MASK); + *insn++ = BPF_ALU32_IMM(BPF_RSH, scratch_reg, FRAME_SZ_SHIFT); + *insn++ = BPF_ALU64_REG(BPF_ADD, dst_reg, scratch_reg); + *insn++ = BPF_ALU64_IMM(BPF_SUB, dst_reg, + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_shared_info, + data_length), + dst_reg, dst_reg, + offsetof(struct xdp_shared_info, + data_length)); + + /* no_mb: */ + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, data_end), + scratch_reg, ctx_reg, + offsetof(struct xdp_buff, data_end)); + *insn++ = BPF_ALU64_REG(BPF_ADD, dst_reg, scratch_reg); + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, data), + scratch_reg, ctx_reg, + offsetof(struct xdp_buff, data)); + *insn++ = BPF_ALU64_REG(BPF_SUB, dst_reg, scratch_reg); + + /* Restore scratch registers */ + *insn++ = BPF_LDX_MEM(BPF_DW, scratch_reg, ctx_reg, + offsetof(struct xdp_buff, tmp_reg[0])); + + if (ctx_reg != si->src_reg) + *insn++ = BPF_LDX_MEM(BPF_DW, ctx_reg, ctx_reg, + offsetof(struct xdp_buff, + tmp_reg[1])); + break; } return insn - insn_buf; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 30b477a26482..62c50ab28ea9 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4380,6 +4380,7 @@ struct xdp_md { __u32 rx_queue_index; /* rxq->queue_index */ __u32 egress_ifindex; /* txq->dev->ifindex */ + __u32 frame_length; }; /* DEVMAP map-value layout -- 2.28.0