// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (C) 2016-2018 Netronome Systems, Inc. */

#include <linux/bpf.h>
#include <linux/bpf_verifier.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/pkt_cls.h>

#include "../nfp_app.h"
#include "../nfp_main.h"
#include "../nfp_net.h"
#include "fw.h"
#include "main.h"

#define pr_vlog(env, fmt, ...)  \
        bpf_verifier_log_write(env, "[nfp] " fmt, ##__VA_ARGS__)

struct nfp_insn_meta *
nfp_bpf_goto_meta(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
                  unsigned int insn_idx)
{
        unsigned int forward, backward, i;

        backward = meta->n - insn_idx;
        forward = insn_idx - meta->n;

        if (min(forward, backward) > nfp_prog->n_insns - insn_idx - 1) {
                backward = nfp_prog->n_insns - insn_idx - 1;
                meta = nfp_prog_last_meta(nfp_prog);
        }
        if (min(forward, backward) > insn_idx && backward > insn_idx) {
                forward = insn_idx;
                meta = nfp_prog_first_meta(nfp_prog);
        }

        if (forward < backward)
                for (i = 0; i < forward; i++)
                        meta = nfp_meta_next(meta);
        else
                for (i = 0; i < backward; i++)
                        meta = nfp_meta_prev(meta);

        return meta;
}

static void
nfp_record_adjust_head(struct nfp_app_bpf *bpf, struct nfp_prog *nfp_prog,
                       struct nfp_insn_meta *meta,
                       const struct bpf_reg_state *reg2)
{
        unsigned int location = UINT_MAX;
        int imm;

        /* Datapath usually can give us guarantees on how much adjust head
         * can be done without the need for any checks.  Optimize the simple
         * case where there is only one adjust head by a constant.
         */
        if (reg2->type != SCALAR_VALUE || !tnum_is_const(reg2->var_off))
                goto exit_set_location;
        imm = reg2->var_off.value;
        /* Translator will skip all checks, we need to guarantee min pkt len */
        if (imm > ETH_ZLEN - ETH_HLEN)
                goto exit_set_location;
        if (imm > (int)bpf->adjust_head.guaranteed_add ||
            imm < -bpf->adjust_head.guaranteed_sub)
                goto exit_set_location;

        if (nfp_prog->adjust_head_location) {
                /* Only one call per program allowed */
                if (nfp_prog->adjust_head_location != meta->n)
                        goto exit_set_location;

                if (meta->arg2.reg.var_off.value != imm)
                        goto exit_set_location;
        }

        location = meta->n;
exit_set_location:
        nfp_prog->adjust_head_location = location;
}

static bool nfp_bpf_map_update_value_ok(struct bpf_verifier_env *env)
{
        const struct bpf_reg_state *reg1 = cur_regs(env) + BPF_REG_1;
        const struct bpf_reg_state *reg3 = cur_regs(env) + BPF_REG_3;
        struct bpf_offloaded_map *offmap;
        struct bpf_func_state *state;
        struct nfp_bpf_map *nfp_map;
        int off, i;

        state = env->cur_state->frame[reg3->frameno];

        /* We need to record each time update happens with non-zero words,
         * in case such word is used in atomic operations.
         * Implicitly depend on nfp_bpf_stack_arg_ok(reg3) being run before.
         */

        offmap = map_to_offmap(reg1->map_ptr);
        nfp_map = offmap->dev_priv;
        off = reg3->off + reg3->var_off.value;

        for (i = 0; i < offmap->map.value_size; i++) {
                struct bpf_stack_state *stack_entry;
                unsigned int soff;

                soff = -(off + i) - 1;
                stack_entry = &state->stack[soff / BPF_REG_SIZE];
                if (stack_entry->slot_type[soff % BPF_REG_SIZE] == STACK_ZERO)
                        continue;

                if (nfp_map->use_map[i / 4].type == NFP_MAP_USE_ATOMIC_CNT) {
                        pr_vlog(env, "value at offset %d/%d may be non-zero, bpf_map_update_elem() is required to initialize atomic counters to zero to avoid offload endian issues\n",
                                i, soff);
                        return false;
                }
                nfp_map->use_map[i / 4].non_zero_update = 1;
        }

        return true;
}

static int
nfp_bpf_stack_arg_ok(const char *fname, struct bpf_verifier_env *env,
                     const struct bpf_reg_state *reg,
                     struct nfp_bpf_reg_state *old_arg)
{
        s64 off, old_off;

        if (reg->type != PTR_TO_STACK) {
                pr_vlog(env, "%s: unsupported ptr type %d\n",
                        fname, reg->type);
                return false;
        }
        if (!tnum_is_const(reg->var_off)) {
                pr_vlog(env, "%s: variable pointer\n", fname);
                return false;
        }

        off = reg->var_off.value + reg->off;
        if (-off % 4) {
                pr_vlog(env, "%s: unaligned stack pointer %lld\n", fname, -off);
                return false;
        }

        /* Rest of the checks is only if we re-parse the same insn */
        if (!old_arg)
                return true;

        old_off = old_arg->reg.var_off.value + old_arg->reg.off;
        old_arg->var_off |= off != old_off;

        return true;
}

static bool
nfp_bpf_map_call_ok(const char *fname, struct bpf_verifier_env *env,
                    struct nfp_insn_meta *meta,
                    u32 helper_tgt, const struct bpf_reg_state *reg1)
{
        if (!helper_tgt) {
                pr_vlog(env, "%s: not supported by FW\n", fname);
                return false;
        }

        return true;
}

static int
nfp_bpf_check_helper_call(struct nfp_prog *nfp_prog,
                          struct bpf_verifier_env *env,
                          struct nfp_insn_meta *meta)
{
        const struct bpf_reg_state *reg1 = cur_regs(env) + BPF_REG_1;
        const struct bpf_reg_state *reg2 = cur_regs(env) + BPF_REG_2;
        const struct bpf_reg_state *reg3 = cur_regs(env) + BPF_REG_3;
        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_vlog(env, "adjust_head not supported by FW\n");
                        return -EOPNOTSUPP;
                }
                if (!(bpf->adjust_head.flags & NFP_BPF_ADJUST_HEAD_NO_META)) {
                        pr_vlog(env, "adjust_head: FW requires shifting metadata, not supported by the driver\n");
                        return -EOPNOTSUPP;
                }

                nfp_record_adjust_head(bpf, nfp_prog, meta, reg2);
                break;

        case BPF_FUNC_xdp_adjust_tail:
                if (!bpf->adjust_tail) {
                        pr_vlog(env, "adjust_tail not supported by FW\n");
                        return -EOPNOTSUPP;
                }
                break;

        case BPF_FUNC_map_lookup_elem:
                if (!nfp_bpf_map_call_ok("map_lookup", env, meta,
                                         bpf->helpers.map_lookup, reg1) ||
                    !nfp_bpf_stack_arg_ok("map_lookup", env, reg2,
                                          meta->func_id ? &meta->arg2 : NULL))
                        return -EOPNOTSUPP;
                break;

        case BPF_FUNC_map_update_elem:
                if (!nfp_bpf_map_call_ok("map_update", env, meta,
                                         bpf->helpers.map_update, reg1) ||
                    !nfp_bpf_stack_arg_ok("map_update", env, reg2,
                                          meta->func_id ? &meta->arg2 : NULL) ||
                    !nfp_bpf_stack_arg_ok("map_update", env, reg3, NULL) ||
                    !nfp_bpf_map_update_value_ok(env))
                        return -EOPNOTSUPP;
                break;

        case BPF_FUNC_map_delete_elem:
                if (!nfp_bpf_map_call_ok("map_delete", env, meta,
                                         bpf->helpers.map_delete, reg1) ||
                    !nfp_bpf_stack_arg_ok("map_delete", env, reg2,
                                          meta->func_id ? &meta->arg2 : NULL))
                        return -EOPNOTSUPP;
                break;

        case BPF_FUNC_get_prandom_u32:
                if (bpf->pseudo_random)
                        break;
                pr_vlog(env, "bpf_get_prandom_u32(): FW doesn't support random number generation\n");
                return -EOPNOTSUPP;

        case BPF_FUNC_perf_event_output:
                BUILD_BUG_ON(NFP_BPF_SCALAR_VALUE != SCALAR_VALUE ||
                             NFP_BPF_MAP_VALUE != PTR_TO_MAP_VALUE ||
                             NFP_BPF_STACK != PTR_TO_STACK ||
                             NFP_BPF_PACKET_DATA != PTR_TO_PACKET);

                if (!bpf->helpers.perf_event_output) {
                        pr_vlog(env, "event_output: not supported by FW\n");
                        return -EOPNOTSUPP;
                }

                /* Force current CPU to make sure we can report the event
                 * wherever we get the control message from FW.
                 */
                if (reg3->var_off.mask & BPF_F_INDEX_MASK ||
                    (reg3->var_off.value & BPF_F_INDEX_MASK) !=
                    BPF_F_CURRENT_CPU) {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg3->var_off);
                        pr_vlog(env, "event_output: must use BPF_F_CURRENT_CPU, var_off: %s\n",
                                tn_buf);
                        return -EOPNOTSUPP;
                }

                /* Save space in meta, we don't care about arguments other
                 * than 4th meta, shove it into arg1.
                 */
                reg1 = cur_regs(env) + BPF_REG_4;

                if (reg1->type != SCALAR_VALUE /* NULL ptr */ &&
                    reg1->type != PTR_TO_STACK &&
                    reg1->type != PTR_TO_MAP_VALUE &&
                    reg1->type != PTR_TO_PACKET) {
                        pr_vlog(env, "event_output: unsupported ptr type: %d\n",
                                reg1->type);
                        return -EOPNOTSUPP;
                }

                if (reg1->type == PTR_TO_STACK &&
                    !nfp_bpf_stack_arg_ok("event_output", env, reg1, NULL))
                        return -EOPNOTSUPP;

                /* Warn user that on offload NFP may return success even if map
                 * is not going to accept the event, since the event output is
                 * fully async and device won't know the state of the map.
                 * There is also FW limitation on the event length.
                 *
                 * Lost events will not show up on the perf ring, driver
                 * won't see them at all.  Events may also get reordered.
                 */
                dev_warn_once(&nfp_prog->bpf->app->pf->pdev->dev,
                              "bpf: note: return codes and behavior of bpf_event_output() helper differs for offloaded programs!\n");
                pr_vlog(env, "warning: return codes and behavior of event_output helper differ for offload!\n");

                if (!meta->func_id)
                        break;

                if (reg1->type != meta->arg1.type) {
                        pr_vlog(env, "event_output: ptr type changed: %d %d\n",
                                meta->arg1.type, reg1->type);
                        return -EINVAL;
                }
                break;

        default:
                pr_vlog(env, "unsupported function id: %d\n", func_id);
                return -EOPNOTSUPP;
        }

        meta->func_id = func_id;
        meta->arg1 = *reg1;
        meta->arg2.reg = *reg2;

        return 0;
}

static int
nfp_bpf_check_exit(struct nfp_prog *nfp_prog,
                   struct bpf_verifier_env *env)
{
        const struct bpf_reg_state *reg0 = cur_regs(env) + BPF_REG_0;
        u64 imm;

        if (nfp_prog->type == BPF_PROG_TYPE_XDP)
                return 0;

        if (!(reg0->type == SCALAR_VALUE && tnum_is_const(reg0->var_off))) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg0->var_off);
                pr_vlog(env, "unsupported exit state: %d, var_off: %s\n",
                        reg0->type, tn_buf);
                return -EINVAL;
        }

        imm = reg0->var_off.value;
        if (nfp_prog->type == BPF_PROG_TYPE_SCHED_CLS &&
            imm <= TC_ACT_REDIRECT &&
            imm != TC_ACT_SHOT && imm != TC_ACT_STOLEN &&
            imm != TC_ACT_QUEUED) {
                pr_vlog(env, "unsupported exit state: %d, imm: %llx\n",
                        reg0->type, imm);
                return -EINVAL;
        }

        return 0;
}

static int
nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
                           struct nfp_insn_meta *meta,
                           const struct bpf_reg_state *reg,
                           struct bpf_verifier_env *env)
{
        s32 old_off, new_off;

        if (reg->frameno != env->cur_state->curframe)
                meta->flags |= FLAG_INSN_PTR_CALLER_STACK_FRAME;

        if (!tnum_is_const(reg->var_off)) {
                pr_vlog(env, "variable ptr stack access\n");
                return -EINVAL;
        }

        if (meta->ptr.type == NOT_INIT)
                return 0;

        old_off = meta->ptr.off + meta->ptr.var_off.value;
        new_off = reg->off + reg->var_off.value;

        meta->ptr_not_const |= old_off != new_off;

        if (!meta->ptr_not_const)
                return 0;

        if (old_off % 4 == new_off % 4)
                return 0;

        pr_vlog(env, "stack access changed location was:%d is:%d\n",
                old_off, new_off);
        return -EINVAL;
}

static const char *nfp_bpf_map_use_name(enum nfp_bpf_map_use use)
{
        static const char * const names[] = {
                [NFP_MAP_UNUSED]        = "unused",
                [NFP_MAP_USE_READ]      = "read",
                [NFP_MAP_USE_WRITE]     = "write",
                [NFP_MAP_USE_ATOMIC_CNT] = "atomic",
        };

        if (use >= ARRAY_SIZE(names) || !names[use])
                return "unknown";
        return names[use];
}

static int
nfp_bpf_map_mark_used_one(struct bpf_verifier_env *env,
                          struct nfp_bpf_map *nfp_map,
                          unsigned int off, enum nfp_bpf_map_use use)
{
        if (nfp_map->use_map[off / 4].type != NFP_MAP_UNUSED &&
            nfp_map->use_map[off / 4].type != use) {
                pr_vlog(env, "map value use type conflict %s vs %s off: %u\n",
                        nfp_bpf_map_use_name(nfp_map->use_map[off / 4].type),
                        nfp_bpf_map_use_name(use), off);
                return -EOPNOTSUPP;
        }

        if (nfp_map->use_map[off / 4].non_zero_update &&
            use == NFP_MAP_USE_ATOMIC_CNT) {
                pr_vlog(env, "atomic counter in map value may already be initialized to non-zero value off: %u\n",
                        off);
                return -EOPNOTSUPP;
        }

        nfp_map->use_map[off / 4].type = use;

        return 0;
}

static int
nfp_bpf_map_mark_used(struct bpf_verifier_env *env, struct nfp_insn_meta *meta,
                      const struct bpf_reg_state *reg,
                      enum nfp_bpf_map_use use)
{
        struct bpf_offloaded_map *offmap;
        struct nfp_bpf_map *nfp_map;
        unsigned int size, off;
        int i, err;

        if (!tnum_is_const(reg->var_off)) {
                pr_vlog(env, "map value offset is variable\n");
                return -EOPNOTSUPP;
        }

        off = reg->var_off.value + meta->insn.off + reg->off;
        size = BPF_LDST_BYTES(&meta->insn);
        offmap = map_to_offmap(reg->map_ptr);
        nfp_map = offmap->dev_priv;

        if (off + size > offmap->map.value_size) {
                pr_vlog(env, "map value access out-of-bounds\n");
                return -EINVAL;
        }

        for (i = 0; i < size; i += 4 - (off + i) % 4) {
                err = nfp_bpf_map_mark_used_one(env, nfp_map, off + i, use);
                if (err)
                        return err;
        }

        return 0;
}

static int
nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
                  struct bpf_verifier_env *env, u8 reg_no)
{
        const struct bpf_reg_state *reg = cur_regs(env) + reg_no;
        int err;

        if (reg->type != PTR_TO_CTX &&
            reg->type != PTR_TO_STACK &&
            reg->type != PTR_TO_MAP_VALUE &&
            reg->type != PTR_TO_PACKET) {
                pr_vlog(env, "unsupported ptr type: %d\n", reg->type);
                return -EINVAL;
        }

        if (reg->type == PTR_TO_STACK) {
                err = nfp_bpf_check_stack_access(nfp_prog, meta, reg, env);
                if (err)
                        return err;
        }

        if (reg->type == PTR_TO_MAP_VALUE) {
                if (is_mbpf_load(meta)) {
                        err = nfp_bpf_map_mark_used(env, meta, reg,
                                                    NFP_MAP_USE_READ);
                        if (err)
                                return err;
                }
                if (is_mbpf_store(meta)) {
                        pr_vlog(env, "map writes not supported\n");
                        return -EOPNOTSUPP;
                }
                if (is_mbpf_atomic(meta)) {
                        err = nfp_bpf_map_mark_used(env, meta, reg,
                                                    NFP_MAP_USE_ATOMIC_CNT);
                        if (err)
                                return err;
                }
        }

        if (meta->ptr.type != NOT_INIT && meta->ptr.type != reg->type) {
                pr_vlog(env, "ptr type changed for instruction %d -> %d\n",
                        meta->ptr.type, reg->type);
                return -EINVAL;
        }

        meta->ptr = *reg;

        return 0;
}

static int
nfp_bpf_check_store(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
                    struct bpf_verifier_env *env)
{
        const struct bpf_reg_state *reg = cur_regs(env) + meta->insn.dst_reg;

        if (reg->type == PTR_TO_CTX) {
                if (nfp_prog->type == BPF_PROG_TYPE_XDP) {
                        /* XDP ctx accesses must be 4B in size */
                        switch (meta->insn.off) {
                        case offsetof(struct xdp_md, rx_queue_index):
                                if (nfp_prog->bpf->queue_select)
                                        goto exit_check_ptr;
                                pr_vlog(env, "queue selection not supported by FW\n");
                                return -EOPNOTSUPP;
                        }
                }
                pr_vlog(env, "unsupported store to context field\n");
                return -EOPNOTSUPP;
        }
exit_check_ptr:
        return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
}

static int
nfp_bpf_check_atomic(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
                     struct bpf_verifier_env *env)
{
        const struct bpf_reg_state *sreg = cur_regs(env) + meta->insn.src_reg;
        const struct bpf_reg_state *dreg = cur_regs(env) + meta->insn.dst_reg;

        if (meta->insn.imm != BPF_ADD) {
                pr_vlog(env, "atomic op not implemented: %d\n", meta->insn.imm);
                return -EOPNOTSUPP;
        }

        if (dreg->type != PTR_TO_MAP_VALUE) {
                pr_vlog(env, "atomic add not to a map value pointer: %d\n",
                        dreg->type);
                return -EOPNOTSUPP;
        }
        if (sreg->type != SCALAR_VALUE) {
                pr_vlog(env, "atomic add not of a scalar: %d\n", sreg->type);
                return -EOPNOTSUPP;
        }

        meta->xadd_over_16bit |=
                sreg->var_off.value > 0xffff || sreg->var_off.mask > 0xffff;
        meta->xadd_maybe_16bit |=
                (sreg->var_off.value & ~sreg->var_off.mask) <= 0xffff;

        return nfp_bpf_check_ptr(nfp_prog, meta, env, meta->insn.dst_reg);
}

static int
nfp_bpf_check_alu(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
                  struct bpf_verifier_env *env)
{
        const struct bpf_reg_state *sreg =
                cur_regs(env) + meta->insn.src_reg;
        const struct bpf_reg_state *dreg =
                cur_regs(env) + meta->insn.dst_reg;

        meta->umin_src = min(meta->umin_src, sreg->umin_value);
        meta->umax_src = max(meta->umax_src, sreg->umax_value);
        meta->umin_dst = min(meta->umin_dst, dreg->umin_value);
        meta->umax_dst = max(meta->umax_dst, dreg->umax_value);

        /* NFP supports u16 and u32 multiplication.
         *
         * For ALU64, if either operand is beyond u32's value range, we reject
         * it. One thing to note, if the source operand is BPF_K, then we need
         * to check "imm" field directly, and we'd reject it if it is negative.
         * Because for ALU64, "imm" (with s32 type) is expected to be sign
         * extended to s64 which NFP mul doesn't support.
         *
         * For ALU32, it is fine for "imm" be negative though, because the
         * result is 32-bits and there is no difference on the low halve of
         * the result for signed/unsigned mul, so we will get correct result.
         */
        if (is_mbpf_mul(meta)) {
                if (meta->umax_dst > U32_MAX) {
                        pr_vlog(env, "multiplier is not within u32 value range\n");
                        return -EINVAL;
                }
                if (mbpf_src(meta) == BPF_X && meta->umax_src > U32_MAX) {
                        pr_vlog(env, "multiplicand is not within u32 value range\n");
                        return -EINVAL;
                }
                if (mbpf_class(meta) == BPF_ALU64 &&
                    mbpf_src(meta) == BPF_K && meta->insn.imm < 0) {
                        pr_vlog(env, "sign extended multiplicand won't be within u32 value range\n");
                        return -EINVAL;
                }
        }

        /* NFP doesn't have divide instructions, we support divide by constant
         * through reciprocal multiplication. Given NFP support multiplication
         * no bigger than u32, we'd require divisor and dividend no bigger than
         * that as well.
         *
         * Also eBPF doesn't support signed divide and has enforced this on C
         * language level by failing compilation. However LLVM assembler hasn't
         * enforced this, so it is possible for negative constant to leak in as
         * a BPF_K operand through assembly code, we reject such cases as well.
         */
        if (is_mbpf_div(meta)) {
                if (meta->umax_dst > U32_MAX) {
                        pr_vlog(env, "dividend is not within u32 value range\n");
                        return -EINVAL;
                }
                if (mbpf_src(meta) == BPF_X) {
                        if (meta->umin_src != meta->umax_src) {
                                pr_vlog(env, "divisor is not constant\n");
                                return -EINVAL;
                        }
                        if (meta->umax_src > U32_MAX) {
                                pr_vlog(env, "divisor is not within u32 value range\n");
                                return -EINVAL;
                        }
                }
                if (mbpf_src(meta) == BPF_K && meta->insn.imm < 0) {
                        pr_vlog(env, "divide by negative constant is not supported\n");
                        return -EINVAL;
                }
        }

        return 0;
}

int nfp_verify_insn(struct bpf_verifier_env *env, int insn_idx,
                    int prev_insn_idx)
{
        struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
        struct nfp_insn_meta *meta = nfp_prog->verifier_meta;

        meta = nfp_bpf_goto_meta(nfp_prog, meta, insn_idx);
        nfp_prog->verifier_meta = meta;

        if (!nfp_bpf_supported_opcode(meta->insn.code)) {
                pr_vlog(env, "instruction %#02x not supported\n",
                        meta->insn.code);
                return -EINVAL;
        }

        if (meta->insn.src_reg >= MAX_BPF_REG ||
            meta->insn.dst_reg >= MAX_BPF_REG) {
                pr_vlog(env, "program uses extended registers - jit hardening?\n");
                return -EINVAL;
        }

        if (is_mbpf_helper_call(meta))
                return nfp_bpf_check_helper_call(nfp_prog, env, meta);
        if (meta->insn.code == (BPF_JMP | BPF_EXIT))
                return nfp_bpf_check_exit(nfp_prog, env);

        if (is_mbpf_load(meta))
                return nfp_bpf_check_ptr(nfp_prog, meta, env,
                                         meta->insn.src_reg);
        if (is_mbpf_store(meta))
                return nfp_bpf_check_store(nfp_prog, meta, env);

        if (is_mbpf_atomic(meta))
                return nfp_bpf_check_atomic(nfp_prog, meta, env);

        if (is_mbpf_alu(meta))
                return nfp_bpf_check_alu(nfp_prog, meta, env);

        return 0;
}

static int
nfp_assign_subprog_idx_and_regs(struct bpf_verifier_env *env,
                                struct nfp_prog *nfp_prog)
{
        struct nfp_insn_meta *meta;
        int index = 0;

        list_for_each_entry(meta, &nfp_prog->insns, l) {
                if (nfp_is_subprog_start(meta))
                        index++;
                meta->subprog_idx = index;

                if (meta->insn.dst_reg >= BPF_REG_6 &&
                    meta->insn.dst_reg <= BPF_REG_9)
                        nfp_prog->subprog[index].needs_reg_push = 1;
        }

        if (index + 1 != nfp_prog->subprog_cnt) {
                pr_vlog(env, "BUG: number of processed BPF functions is not consistent (processed %d, expected %d)\n",
                        index + 1, nfp_prog->subprog_cnt);
                return -EFAULT;
        }

        return 0;
}

static unsigned int nfp_bpf_get_stack_usage(struct nfp_prog *nfp_prog)
{
        struct nfp_insn_meta *meta = nfp_prog_first_meta(nfp_prog);
        unsigned int max_depth = 0, depth = 0, frame = 0;
        struct nfp_insn_meta *ret_insn[MAX_CALL_FRAMES];
        unsigned short frame_depths[MAX_CALL_FRAMES];
        unsigned short ret_prog[MAX_CALL_FRAMES];
        unsigned short idx = meta->subprog_idx;

        /* Inspired from check_max_stack_depth() from kernel verifier.
         * Starting from main subprogram, walk all instructions and recursively
         * walk all callees that given subprogram can call. Since recursion is
         * prevented by the kernel verifier, this algorithm only needs a local
         * stack of MAX_CALL_FRAMES to remember callsites.
         */
process_subprog:
        frame_depths[frame] = nfp_prog->subprog[idx].stack_depth;
        frame_depths[frame] = round_up(frame_depths[frame], STACK_FRAME_ALIGN);
        depth += frame_depths[frame];
        max_depth = max(max_depth, depth);

continue_subprog:
        for (; meta != nfp_prog_last_meta(nfp_prog) && meta->subprog_idx == idx;
             meta = nfp_meta_next(meta)) {
                if (!is_mbpf_pseudo_call(meta))
                        continue;

                /* We found a call to a subprogram. Remember instruction to
                 * return to and subprog id.
                 */
                ret_insn[frame] = nfp_meta_next(meta);
                ret_prog[frame] = idx;

                /* Find the callee and start processing it. */
                meta = nfp_bpf_goto_meta(nfp_prog, meta,
                                         meta->n + 1 + meta->insn.imm);
                idx = meta->subprog_idx;
                frame++;
                goto process_subprog;
        }
        /* End of for() loop means the last instruction of the subprog was
         * reached. If we popped all stack frames, return; otherwise, go on
         * processing remaining instructions from the caller.
         */
        if (frame == 0)
                return max_depth;

        depth -= frame_depths[frame];
        frame--;
        meta = ret_insn[frame];
        idx = ret_prog[frame];
        goto continue_subprog;
}

static void nfp_bpf_insn_flag_zext(struct nfp_prog *nfp_prog,
                                   struct bpf_insn_aux_data *aux)
{
        struct nfp_insn_meta *meta;

        list_for_each_entry(meta, &nfp_prog->insns, l) {
                if (aux[meta->n].zext_dst)
                        meta->flags |= FLAG_INSN_DO_ZEXT;
        }
}

int nfp_bpf_finalize(struct bpf_verifier_env *env)
{
        struct bpf_subprog_info *info;
        struct nfp_prog *nfp_prog;
        unsigned int max_stack;
        struct nfp_net *nn;
        int i;

        nfp_prog = env->prog->aux->offload->dev_priv;
        nfp_prog->subprog_cnt = env->subprog_cnt;
        nfp_prog->subprog = kzalloc_objs(nfp_prog->subprog[0],
                                         nfp_prog->subprog_cnt);
        if (!nfp_prog->subprog)
                return -ENOMEM;

        nfp_assign_subprog_idx_and_regs(env, nfp_prog);

        info = env->subprog_info;
        for (i = 0; i < nfp_prog->subprog_cnt; i++) {
                nfp_prog->subprog[i].stack_depth = info[i].stack_depth;

                if (i == 0)
                        continue;

                /* Account for size of return address. */
                nfp_prog->subprog[i].stack_depth += REG_WIDTH;
                /* Account for size of saved registers, if necessary. */
                if (nfp_prog->subprog[i].needs_reg_push)
                        nfp_prog->subprog[i].stack_depth += BPF_REG_SIZE * 4;
        }

        nn = netdev_priv(env->prog->aux->offload->netdev);
        max_stack = nn_readb(nn, NFP_NET_CFG_BPF_STACK_SZ) * 64;
        nfp_prog->stack_size = nfp_bpf_get_stack_usage(nfp_prog);
        if (nfp_prog->stack_size > max_stack) {
                pr_vlog(env, "stack too large: program %dB > FW stack %dB\n",
                        nfp_prog->stack_size, max_stack);
                return -EOPNOTSUPP;
        }

        nfp_bpf_insn_flag_zext(nfp_prog, env->insn_aux_data);
        return 0;
}

int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
                             struct bpf_insn *insn)
{
        struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        struct nfp_insn_meta *meta = nfp_prog->verifier_meta;

        meta = nfp_bpf_goto_meta(nfp_prog, meta, aux_data[off].orig_idx);
        nfp_prog->verifier_meta = meta;

        /* conditional jump to jump conversion */
        if (is_mbpf_cond_jump(meta) &&
            insn->code == (BPF_JMP | BPF_JA | BPF_K)) {
                unsigned int tgt_off;

                tgt_off = off + insn->off + 1;

                if (!insn->off) {
                        meta->jmp_dst = list_next_entry(meta, l);
                        meta->jump_neg_op = false;
                } else if (meta->jmp_dst->n != aux_data[tgt_off].orig_idx) {
                        pr_vlog(env, "branch hard wire at %d changes target %d -> %d\n",
                                off, meta->jmp_dst->n,
                                aux_data[tgt_off].orig_idx);
                        return -EINVAL;
                }
                return 0;
        }

        pr_vlog(env, "unsupported instruction replacement %hhx -> %hhx\n",
                meta->insn.code, insn->code);
        return -EINVAL;
}

int nfp_bpf_opt_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
{
        struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        struct nfp_insn_meta *meta = nfp_prog->verifier_meta;
        unsigned int i;

        meta = nfp_bpf_goto_meta(nfp_prog, meta, aux_data[off].orig_idx);

        for (i = 0; i < cnt; i++) {
                if (WARN_ON_ONCE(&meta->l == &nfp_prog->insns))
                        return -EINVAL;

                /* doesn't count if it already has the flag */
                if (meta->flags & FLAG_INSN_SKIP_VERIFIER_OPT)
                        i--;

                meta->flags |= FLAG_INSN_SKIP_VERIFIER_OPT;
                meta = list_next_entry(meta, l);
        }

        return 0;
}