// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2022 Red Hat, Inc. */
#include <linux/bpf.h>
#include <linux/fs.h>
#include <linux/filter.h>
#include <linux/kernel.h>
#include <linux/btf_ids.h>

struct bpf_iter_seq_link_info {
        u32 link_id;
};

static void *bpf_link_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct bpf_iter_seq_link_info *info = seq->private;
        struct bpf_link *link;

        link = bpf_link_get_curr_or_next(&info->link_id);
        if (!link)
                return NULL;

        if (*pos == 0)
                ++*pos;
        return link;
}

static void *bpf_link_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct bpf_iter_seq_link_info *info = seq->private;

        ++*pos;
        ++info->link_id;
        bpf_link_put((struct bpf_link *)v);
        return bpf_link_get_curr_or_next(&info->link_id);
}

struct bpf_iter__bpf_link {
        __bpf_md_ptr(struct bpf_iter_meta *, meta);
        __bpf_md_ptr(struct bpf_link *, link);
};

DEFINE_BPF_ITER_FUNC(bpf_link, struct bpf_iter_meta *meta, struct bpf_link *link)

static int __bpf_link_seq_show(struct seq_file *seq, void *v, bool in_stop)
{
        struct bpf_iter__bpf_link ctx;
        struct bpf_iter_meta meta;
        struct bpf_prog *prog;
        int ret = 0;

        ctx.meta = &meta;
        ctx.link = v;
        meta.seq = seq;
        prog = bpf_iter_get_info(&meta, in_stop);
        if (prog)
                ret = bpf_iter_run_prog(prog, &ctx);

        return ret;
}

static int bpf_link_seq_show(struct seq_file *seq, void *v)
{
        return __bpf_link_seq_show(seq, v, false);
}

static void bpf_link_seq_stop(struct seq_file *seq, void *v)
{
        if (!v)
                (void)__bpf_link_seq_show(seq, v, true);
        else
                bpf_link_put((struct bpf_link *)v);
}

static const struct seq_operations bpf_link_seq_ops = {
        .start  = bpf_link_seq_start,
        .next   = bpf_link_seq_next,
        .stop   = bpf_link_seq_stop,
        .show   = bpf_link_seq_show,
};

BTF_ID_LIST_SINGLE(btf_bpf_link_id, struct, bpf_link)

static const struct bpf_iter_seq_info bpf_link_seq_info = {
        .seq_ops                = &bpf_link_seq_ops,
        .init_seq_private       = NULL,
        .fini_seq_private       = NULL,
        .seq_priv_size          = sizeof(struct bpf_iter_seq_link_info),
};

static struct bpf_iter_reg bpf_link_reg_info = {
        .target                 = "bpf_link",
        .ctx_arg_info_size      = 1,
        .ctx_arg_info           = {
                { offsetof(struct bpf_iter__bpf_link, link),
                  PTR_TO_BTF_ID_OR_NULL },
        },
        .seq_info               = &bpf_link_seq_info,
};

static int __init bpf_link_iter_init(void)
{
        bpf_link_reg_info.ctx_arg_info[0].btf_id = *btf_bpf_link_id;
        return bpf_iter_reg_target(&bpf_link_reg_info);
}

late_initcall(bpf_link_iter_init);