bpf_load

static int bpf_prog_load(union bpf_attr *attr)
{
    enum bpf_prog_type type = attr->prog_type;
    struct bpf_prog *prog;
    int err;
    char license[128];
    bool is_gpl;

    if (CHECK_ATTR(BPF_PROG_LOAD))   //check attr中不用的字段是否全零
        return -EINVAL;

    if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)  //只支持BPF_F_STRICT_ALIGNMENT
        return -EINVAL;

    /* copy eBPF program license from user space */
    if (strncpy_from_user(license, u64_to_user_ptr(attr->license),
                  sizeof(license) - 1) < 0)
        return -EFAULT;
    license[sizeof(license) - 1] = 0;   //从用户态内存copy license字符串

    /* eBPF programs must be GPL compatible to use GPL-ed functions */
    is_gpl = license_is_gpl_compatible(license);   //不是gpl 有些helper fn不能使用  verify时校验

    if (attr->insn_cnt == 0 || attr->insn_cnt > BPF_MAXINSNS)  //指令数校验
        return -E2BIG;

    if (type == BPF_PROG_TYPE_KPROBE &&
        attr->kern_version != LINUX_VERSION_CODE)   //kprobe类型的  要和内核版本一致
        return -EINVAL;

    if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
        type != BPF_PROG_TYPE_CGROUP_SKB &&        //两种不查权限的类型
        !capable(CAP_SYS_ADMIN))
        return -EPERM;

    bpf_prog_load_fixup_attach_type(attr);   //加了expected_attach_type字段  向后兼容
    if (bpf_prog_load_check_attach_type(type, attr->expected_attach_type))  //check expected_attach_type
        return -EINVAL;

    /* plain bpf_prog allocation */
    prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);   //申请bpf_prog内存 用户空间内存 详解
    if (!prog)
        return -ENOMEM;

    prog->expected_attach_type = attr->expected_attach_type;

    prog->aux->offload_requested = !!attr->prog_ifindex;

    err = security_bpf_prog_alloc(prog->aux);  //LSM相关
    if (err)
        goto free_prog_nouncharge;

    err = bpf_prog_charge_memlock(prog);   //bpf_prog的内存锁定到当前用户
    if (err)
        goto free_prog_sec;

    prog->len = attr->insn_cnt;

    err = -EFAULT;
    if (copy_from_user(prog->insns, u64_to_user_ptr(attr->insns),
               bpf_prog_insn_size(prog)) != 0)       //copy指令 用户态内存到内核态内存
        goto free_prog;

    prog->orig_prog = NULL;
    prog->jited = 0;

    atomic_set(&prog->aux->refcnt, 1);   //引用计数
    prog->gpl_compatible = is_gpl ? 1 : 0;

    if (bpf_prog_is_dev_bound(prog->aux)) {
        err = bpf_prog_offload_init(prog, attr);  //绑定接口的需要初始化offload
        if (err)
            goto free_prog;
    }

    /* find program type: socket_filter vs tracing_filter */
    err = find_prog_type(type, prog);  //按类型 绑定bpf_prog_ops
    if (err < 0)
        goto free_prog;

    prog->aux->load_time = ktime_get_boot_ns();
    err = bpf_obj_name_cpy(prog->aux->name, attr->prog_name);
    if (err)
        goto free_prog;

    /* run eBPF verifier */
    err = bpf_check(&prog, attr);
    if (err < 0)
        goto free_used_maps;

    prog = bpf_prog_select_runtime(prog, &err);     //选择执行器
    if (err < 0)
        goto free_used_maps;

    err = bpf_prog_alloc_id(prog);              //分配id
    if (err)
        goto free_used_maps;

    err = bpf_prog_new_fd(prog);                   //分配fd
    if (err < 0) {
        /* failed to allocate fd.
         * bpf_prog_put() is needed because the above
         * bpf_prog_alloc_id() has published the prog
         * to the userspace and the userspace may
         * have refcnt-ed it through BPF_PROG_GET_FD_BY_ID.
         */
        bpf_prog_put(prog);
        return err;
    }

    bpf_prog_kallsyms_add(prog);
    return err;

free_used_maps:
    bpf_prog_kallsyms_del_subprogs(prog);
    free_used_maps(prog->aux);
free_prog:
    bpf_prog_uncharge_memlock(prog);
free_prog_sec:
    security_bpf_prog_free(prog->aux);
free_prog_nouncharge:
    bpf_prog_free(prog);
    return err;
}


struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
{
    gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | gfp_extra_flags;
    struct bpf_prog_aux *aux;
    struct bpf_prog *fp;

    size = round_up(size, PAGE_SIZE);
    fp = __vmalloc(size, gfp_flags, PAGE_KERNEL);  //页粒度 存size个指令
    if (fp == NULL)
        return NULL;

    aux = kzalloc(sizeof(*aux), GFP_KERNEL | gfp_extra_flags);  //其他信息
    if (aux == NULL) {
        vfree(fp);
        return NULL;
    }

    fp->pages = size / PAGE_SIZE;    
    fp->aux = aux;
    fp->aux->prog = fp;
    fp->jit_requested = ebpf_jit_enabled();

    INIT_LIST_HEAD_RCU(&fp->aux->ksym_lnode);

    return fp;
}