// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2021. Huawei Technologies Co., Ltd
 */
#include <linux/kernel.h>
#include <linux/bpf_verifier.h>
#include <linux/bpf.h>
#include <linux/btf.h>

static struct bpf_struct_ops bpf_bpf_dummy_ops;

/* A common type for test_N with return value in bpf_dummy_ops */
typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);

static int dummy_ops_test_ret_function(struct bpf_dummy_ops_state *state, ...)
{
        return 0;
}

struct bpf_dummy_ops_test_args {
        u64 args[MAX_BPF_FUNC_ARGS];
        struct bpf_dummy_ops_state state;
};

static struct btf *bpf_dummy_ops_btf;

static struct bpf_dummy_ops_test_args *
dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
{
        __u32 size_in;
        struct bpf_dummy_ops_test_args *args;
        void __user *ctx_in;
        void __user *u_state;

        size_in = kattr->test.ctx_size_in;
        if (size_in != sizeof(u64) * nr)
                return ERR_PTR(-EINVAL);

        args = kzalloc_obj(*args);
        if (!args)
                return ERR_PTR(-ENOMEM);

        ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
        if (copy_from_user(args->args, ctx_in, size_in))
                goto out;

        /* args[0] is 0 means state argument of test_N will be NULL */
        u_state = u64_to_user_ptr(args->args[0]);
        if (u_state && copy_from_user(&args->state, u_state,
                                      sizeof(args->state)))
                goto out;

        return args;
out:
        kfree(args);
        return ERR_PTR(-EFAULT);
}

static int dummy_ops_copy_args(struct bpf_dummy_ops_test_args *args)
{
        void __user *u_state;

        u_state = u64_to_user_ptr(args->args[0]);
        if (u_state && copy_to_user(u_state, &args->state, sizeof(args->state)))
                return -EFAULT;

        return 0;
}

static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
{
        dummy_ops_test_ret_fn test = (void *)image + cfi_get_offset();
        struct bpf_dummy_ops_state *state = NULL;

        /* state needs to be NULL if args[0] is 0 */
        if (args->args[0])
                state = &args->state;
        return test(state, args->args[1], args->args[2],
                    args->args[3], args->args[4]);
}

static const struct bpf_ctx_arg_aux *find_ctx_arg_info(struct bpf_prog_aux *aux, int offset)
{
        int i;

        for (i = 0; i < aux->ctx_arg_info_size; i++)
                if (aux->ctx_arg_info[i].offset == offset)
                        return &aux->ctx_arg_info[i];

        return NULL;
}

/* There is only one check at the moment:
 * - zero should not be passed for pointer parameters not marked as nullable.
 */
static int check_test_run_args(struct bpf_prog *prog, struct bpf_dummy_ops_test_args *args)
{
        const struct btf_type *func_proto = prog->aux->attach_func_proto;

        for (u32 arg_no = 0; arg_no < btf_type_vlen(func_proto) ; ++arg_no) {
                const struct btf_param *param = &btf_params(func_proto)[arg_no];
                const struct bpf_ctx_arg_aux *info;
                const struct btf_type *t;
                int offset;

                if (args->args[arg_no] != 0)
                        continue;

                /* Program is validated already, so there is no need
                 * to check if t is NULL.
                 */
                t = btf_type_skip_modifiers(bpf_dummy_ops_btf, param->type, NULL);
                if (!btf_type_is_ptr(t))
                        continue;

                offset = btf_ctx_arg_offset(bpf_dummy_ops_btf, func_proto, arg_no);
                info = find_ctx_arg_info(prog->aux, offset);
                if (info && type_may_be_null(info->reg_type))
                        continue;

                return -EINVAL;
        }

        return 0;
}

extern const struct bpf_link_ops bpf_struct_ops_link_lops;

int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
                            union bpf_attr __user *uattr)
{
        const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
        const struct btf_type *func_proto;
        struct bpf_dummy_ops_test_args *args;
        struct bpf_tramp_links *tlinks = NULL;
        struct bpf_tramp_link *link = NULL;
        void *image = NULL;
        unsigned int op_idx;
        u32 image_off = 0;
        int prog_ret;
        s32 type_id;
        int err;

        type_id = btf_find_by_name_kind(bpf_dummy_ops_btf,
                                        bpf_bpf_dummy_ops.name,
                                        BTF_KIND_STRUCT);
        if (type_id < 0)
                return -EINVAL;
        if (prog->aux->attach_btf_id != type_id)
                return -EOPNOTSUPP;

        func_proto = prog->aux->attach_func_proto;
        args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
        if (IS_ERR(args))
                return PTR_ERR(args);

        err = check_test_run_args(prog, args);
        if (err)
                goto out;

        tlinks = kzalloc_objs(*tlinks, BPF_TRAMP_MAX);
        if (!tlinks) {
                err = -ENOMEM;
                goto out;
        }

        link = kzalloc_obj(*link, GFP_USER);
        if (!link) {
                err = -ENOMEM;
                goto out;
        }
        /* prog doesn't take the ownership of the reference from caller */
        bpf_prog_inc(prog);
        bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_link_lops, prog,
                      prog->expected_attach_type);

        op_idx = prog->expected_attach_type;
        err = bpf_struct_ops_prepare_trampoline(tlinks, link,
                                                &st_ops->func_models[op_idx],
                                                &dummy_ops_test_ret_function,
                                                &image, &image_off,
                                                true);
        if (err < 0)
                goto out;

        err = arch_protect_bpf_trampoline(image, PAGE_SIZE);
        if (err)
                goto out;
        prog_ret = dummy_ops_call_op(image, args);

        err = dummy_ops_copy_args(args);
        if (err)
                goto out;
        if (put_user(prog_ret, &uattr->test.retval))
                err = -EFAULT;
out:
        kfree(args);
        bpf_struct_ops_image_free(image);
        if (link)
                bpf_link_put(&link->link);
        kfree(tlinks);
        return err;
}

static int bpf_dummy_init(struct btf *btf)
{
        bpf_dummy_ops_btf = btf;
        return 0;
}

static bool bpf_dummy_ops_is_valid_access(int off, int size,
                                          enum bpf_access_type type,
                                          const struct bpf_prog *prog,
                                          struct bpf_insn_access_aux *info)
{
        return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
}

static int bpf_dummy_ops_check_member(const struct btf_type *t,
                                      const struct btf_member *member,
                                      const struct bpf_prog *prog)
{
        u32 moff = __btf_member_bit_offset(t, member) / 8;

        switch (moff) {
        case offsetof(struct bpf_dummy_ops, test_sleepable):
                break;
        default:
                if (prog->sleepable)
                        return -EINVAL;
        }

        return 0;
}

static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
                                           const struct bpf_reg_state *reg,
                                           int off, int size)
{
        const struct btf_type *state;
        const struct btf_type *t;
        s32 type_id;

        type_id = btf_find_by_name_kind(reg->btf, "bpf_dummy_ops_state",
                                        BTF_KIND_STRUCT);
        if (type_id < 0)
                return -EINVAL;

        t = btf_type_by_id(reg->btf, reg->btf_id);
        state = btf_type_by_id(reg->btf, type_id);
        if (t != state) {
                bpf_log(log, "only access to bpf_dummy_ops_state is supported\n");
                return -EACCES;
        }

        if (off + size > sizeof(struct bpf_dummy_ops_state)) {
                bpf_log(log, "write access at off %d with size %d\n", off, size);
                return -EACCES;
        }

        return NOT_INIT;
}

static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
        .is_valid_access = bpf_dummy_ops_is_valid_access,
        .btf_struct_access = bpf_dummy_ops_btf_struct_access,
};

static int bpf_dummy_init_member(const struct btf_type *t,
                                 const struct btf_member *member,
                                 void *kdata, const void *udata)
{
        return -EOPNOTSUPP;
}

static int bpf_dummy_reg(void *kdata, struct bpf_link *link)
{
        return -EOPNOTSUPP;
}

static void bpf_dummy_unreg(void *kdata, struct bpf_link *link)
{
}

static int bpf_dummy_ops__test_1(struct bpf_dummy_ops_state *cb__nullable)
{
        return 0;
}

static int bpf_dummy_test_2(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
                            char a3, unsigned long a4)
{
        return 0;
}

static int bpf_dummy_test_sleepable(struct bpf_dummy_ops_state *cb)
{
        return 0;
}

static struct bpf_dummy_ops __bpf_bpf_dummy_ops = {
        .test_1 = bpf_dummy_ops__test_1,
        .test_2 = bpf_dummy_test_2,
        .test_sleepable = bpf_dummy_test_sleepable,
};

static struct bpf_struct_ops bpf_bpf_dummy_ops = {
        .verifier_ops = &bpf_dummy_verifier_ops,
        .init = bpf_dummy_init,
        .check_member = bpf_dummy_ops_check_member,
        .init_member = bpf_dummy_init_member,
        .reg = bpf_dummy_reg,
        .unreg = bpf_dummy_unreg,
        .name = "bpf_dummy_ops",
        .cfi_stubs = &__bpf_bpf_dummy_ops,
        .owner = THIS_MODULE,
};

static int __init bpf_dummy_struct_ops_init(void)
{
        return register_bpf_struct_ops(&bpf_bpf_dummy_ops, bpf_dummy_ops);
}
late_initcall(bpf_dummy_struct_ops_init);