nfp: bpf: add basic support for adjust head call

Support bpf_xdp_adjust_head().  We need to check whether the
packet offset after adjustment is within datapath's limits.
We also check if the frame is at least ETH_HLEN long (similar
to the kernel implementation).
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/netronome/nfp/bpf/fw.h

+/*
+ * Copyright (C) 2017 Netronome Systems, Inc.
+ *
+ * This software is dual licensed under the GNU General License Version 2,
+ * June 1991 as shown in the file COPYING in the top-level directory of this
+ * source tree or the BSD 2-Clause License provided below.  You have the
+ * option to license this software under the complete terms of either license.
+ *
+ * The BSD 2-Clause License:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      1. Redistributions of source code must retain the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer.
+ *
+ *      2. Redistributions in binary form must reproduce the above
+ *         copyright notice, this list of conditions and the following
+ *         disclaimer in the documentation and/or other materials
+ *         provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef NFP_BPF_FW_H
+#define NFP_BPF_FW_H 1
+
+#include <linux/bitops.h>
+#include <linux/types.h>
+
+enum bpf_cap_tlv_type {
+	NFP_BPF_CAP_TYPE_ADJUST_HEAD	= 2,
+};
+
+struct nfp_bpf_cap_tlv_adjust_head {
+	__le32 flags;
+	__le32 off_min;
+	__le32 off_max;
+	__le32 guaranteed_sub;
+	__le32 guaranteed_add;
+};
+
+#define NFP_BPF_ADJUST_HEAD_NO_META	BIT(0)
+
+#endif

drivers/net/ethernet/netronome/nfp/bpf/jit.c

@@ -33,6 +33,7 @@
 
 #define pr_fmt(fmt)	"NFP net bpf: " fmt
 
+#include <linux/bug.h>
 #include <linux/kernel.h>
 #include <linux/bpf.h>
 #include <linux/filter.h>
@@ -87,6 +88,18 @@ static unsigned int nfp_prog_current_offset(struct nfp_prog *nfp_prog)
 	return nfp_prog->start_off + nfp_prog->prog_len;
 }
 
+static bool
+nfp_prog_confirm_current_offset(struct nfp_prog *nfp_prog, unsigned int off)
+{
+	/* If there is a recorded error we may have dropped instructions;
+	 * that doesn't have to be due to translator bug, and the translation
+	 * will fail anyway, so just return OK.
+	 */
+	if (nfp_prog->error)
+		return true;
+	return !WARN_ON_ONCE(nfp_prog_current_offset(nfp_prog) != off);
+}
+
 static unsigned int
 nfp_prog_offset_to_index(struct nfp_prog *nfp_prog, unsigned int offset)
 {
@@ -1196,6 +1209,64 @@ static void wrp_end32(struct nfp_prog *nfp_prog, swreg reg_in, u8 gpr_out)
 		      SHF_SC_R_ROT, 16);
 }
 
+static int adjust_head(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
+{
+	swreg tmp = imm_a(nfp_prog), tmp_len = imm_b(nfp_prog);
+	struct nfp_bpf_cap_adjust_head *adjust_head;
+	u32 ret_einval, end;
+
+	adjust_head = &nfp_prog->bpf->adjust_head;
+
+	ret_einval = nfp_prog_current_offset(nfp_prog) + 14;
+	end = ret_einval + 2;
+
+	/* We need to use a temp because offset is just a part of the pkt ptr */
+	emit_alu(nfp_prog, tmp,
+		 reg_a(2 * 2), ALU_OP_ADD_2B, pptr_reg(nfp_prog));
+
+	/* Validate result will fit within FW datapath constraints */
+	emit_alu(nfp_prog, reg_none(),
+		 tmp, ALU_OP_SUB, reg_imm(adjust_head->off_min));
+	emit_br(nfp_prog, BR_BLO, ret_einval, 0);
+	emit_alu(nfp_prog, reg_none(),
+		 reg_imm(adjust_head->off_max), ALU_OP_SUB, tmp);
+	emit_br(nfp_prog, BR_BLO, ret_einval, 0);
+
+	/* Validate the length is at least ETH_HLEN */
+	emit_alu(nfp_prog, tmp_len,
+		 plen_reg(nfp_prog), ALU_OP_SUB, reg_a(2 * 2));
+	emit_alu(nfp_prog, reg_none(),
+		 tmp_len, ALU_OP_SUB, reg_imm(ETH_HLEN));
+	emit_br(nfp_prog, BR_BMI, ret_einval, 0);
+
+	/* Load the ret code */
+	wrp_immed(nfp_prog, reg_both(0), 0);
+	wrp_immed(nfp_prog, reg_both(1), 0);
+
+	/* Modify the packet metadata */
+	emit_ld_field(nfp_prog, pptr_reg(nfp_prog), 0x3, tmp, SHF_SC_NONE, 0);
+
+	/* Skip over the -EINVAL ret code (defer 2) */
+	emit_br_def(nfp_prog, end, 2);
+
+	emit_alu(nfp_prog, plen_reg(nfp_prog),
+		 plen_reg(nfp_prog), ALU_OP_SUB, reg_a(2 * 2));
+	emit_alu(nfp_prog, pv_len(nfp_prog),
+		 pv_len(nfp_prog), ALU_OP_SUB, reg_a(2 * 2));
+
+	/* return -EINVAL target */
+	if (!nfp_prog_confirm_current_offset(nfp_prog, ret_einval))
+		return -EINVAL;
+
+	wrp_immed(nfp_prog, reg_both(0), -22);
+	wrp_immed(nfp_prog, reg_both(1), ~0);
+
+	if (!nfp_prog_confirm_current_offset(nfp_prog, end))
+		return -EINVAL;
+
+	return 0;
+}
+
 /* --- Callbacks --- */
 static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
@@ -1933,6 +2004,8 @@ static int jne_reg(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 static int call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
 	switch (meta->insn.imm) {
+	case BPF_FUNC_xdp_adjust_head:
+		return adjust_head(nfp_prog, meta);
 	default:
 		WARN_ONCE(1, "verifier allowed unsupported function\n");
 		return -EOPNOTSUPP;

drivers/net/ethernet/netronome/nfp/bpf/main.c

@@ -39,6 +39,7 @@
 #include "../nfp_main.h"
 #include "../nfp_net.h"
 #include "../nfp_port.h"
+#include "fw.h"
 #include "main.h"
 
 static bool nfp_net_ebpf_capable(struct nfp_net *nn)
@@ -156,6 +157,36 @@ static bool nfp_bpf_tc_busy(struct nfp_app *app, struct nfp_net *nn)
 	return nn->dp.ctrl & NFP_NET_CFG_CTRL_BPF;
 }
 
+static int
+nfp_bpf_parse_cap_adjust_head(struct nfp_app_bpf *bpf, void __iomem *value,
+			      u32 length)
+{
+	struct nfp_bpf_cap_tlv_adjust_head __iomem *cap = value;
+	struct nfp_cpp *cpp = bpf->app->pf->cpp;
+
+	if (length < sizeof(*cap)) {
+		nfp_err(cpp, "truncated adjust_head TLV: %d\n", length);
+		return -EINVAL;
+	}
+
+	bpf->adjust_head.flags = readl(&cap->flags);
+	bpf->adjust_head.off_min = readl(&cap->off_min);
+	bpf->adjust_head.off_max = readl(&cap->off_max);
+
+	if (bpf->adjust_head.off_min > bpf->adjust_head.off_max) {
+		nfp_err(cpp, "invalid adjust_head TLV: min > max\n");
+		return -EINVAL;
+	}
+	if (!FIELD_FIT(UR_REG_IMM_MAX, bpf->adjust_head.off_min) ||
+	    !FIELD_FIT(UR_REG_IMM_MAX, bpf->adjust_head.off_max)) {
+		nfp_warn(cpp, "disabling adjust_head - driver expects min/max to fit in as immediates\n");
+		memset(&bpf->adjust_head, 0, sizeof(bpf->adjust_head));
+		return 0;
+	}
+
+	return 0;
+}
+
 static int nfp_bpf_parse_capabilities(struct nfp_app *app)
 {
 	struct nfp_cpp *cpp = app->pf->cpp;
@@ -169,16 +200,23 @@ static int nfp_bpf_parse_capabilities(struct nfp_app *app)
 
 	start = mem;
 	while (mem - start + 8 < nfp_cpp_area_size(area)) {
+		u8 __iomem *value;
 		u32 type, length;
 
 		type = readl(mem);
 		length = readl(mem + 4);
+		value = mem + 8;
 
 		mem += 8 + length;
 		if (mem - start > nfp_cpp_area_size(area))
 			goto err_release_free;
 
 		switch (type) {
+		case NFP_BPF_CAP_TYPE_ADJUST_HEAD:
+			if (nfp_bpf_parse_cap_adjust_head(app->priv, value,
+							  length))
+				goto err_release_free;
+			break;
 		default:
 			nfp_dbg(cpp, "unknown BPF capability: %d\n", type);
 			break;

drivers/net/ethernet/netronome/nfp/bpf/main.h

@@ -81,9 +81,20 @@ enum pkt_vec {
 /**
  * struct nfp_app_bpf - bpf app priv structure
  * @app:		backpointer to the app
+ *
+ * @adjust_head:	adjust head capability
+ * @flags:		extra flags for adjust head
+ * @off_min:		minimal packet offset within buffer required
+ * @off_max:		maximum packet offset within buffer required
  */
 struct nfp_app_bpf {
 	struct nfp_app *app;
+
+	struct nfp_bpf_cap_adjust_head {
+		u32 flags;
+		int off_min;
+		int off_max;
+	} adjust_head;
 };
 
 struct nfp_prog;

drivers/net/ethernet/netronome/nfp/bpf/verifier.c

@@ -38,6 +38,7 @@
 #include <linux/kernel.h>
 #include <linux/pkt_cls.h>
 
+#include "fw.h"
 #include "main.h"
 
 struct nfp_insn_meta *
@@ -71,9 +72,20 @@ nfp_bpf_goto_meta(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 static int
 nfp_bpf_check_call(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
 {
+	struct nfp_app_bpf *bpf = nfp_prog->bpf;
 	u32 func_id = meta->insn.imm;
 
 	switch (func_id) {
+	case BPF_FUNC_xdp_adjust_head:
+		if (!bpf->adjust_head.off_max) {
+			pr_warn("adjust_head not supported by FW\n");
+			return -EOPNOTSUPP;
+		}
+		if (!(bpf->adjust_head.flags & NFP_BPF_ADJUST_HEAD_NO_META)) {
+			pr_warn("adjust_head: FW requires shifting metadata, not supported by the driver\n");
+			return -EOPNOTSUPP;
+		}
+		break;
 	default:
 		pr_warn("unsupported function id: %d\n", func_id);
 		return -EOPNOTSUPP;

drivers/net/ethernet/netronome/nfp/nfp_asm.h

@@ -77,6 +77,7 @@
 enum br_mask {
 	BR_BEQ = 0x00,
 	BR_BNE = 0x01,
+	BR_BMI = 0x02,
 	BR_BHS = 0x04,
 	BR_BLO = 0x05,
 	BR_BGE = 0x08,
@@ -175,6 +176,7 @@ enum alu_op {
 	ALU_OP_NONE	= 0x00,
 	ALU_OP_ADD	= 0x01,
 	ALU_OP_NOT	= 0x04,
+	ALU_OP_ADD_2B	= 0x05,
 	ALU_OP_AND	= 0x08,
 	ALU_OP_SUB_C	= 0x0d,
 	ALU_OP_ADD_C	= 0x11,