// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (C) 2020 Facebook */

#include <errno.h>
#include <stdio.h>
#include <unistd.h>

#include <linux/err.h>

#include <bpf/bpf.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>

#include "json_writer.h"
#include "main.h"

#define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"

static const struct btf_type *map_info_type;
static __u32 map_info_alloc_len;
static struct btf *btf_vmlinux;
static __s32 map_info_type_id;

struct res {
        unsigned int nr_maps;
        unsigned int nr_errs;
};

static const struct btf *get_btf_vmlinux(void)
{
        if (btf_vmlinux)
                return btf_vmlinux;

        btf_vmlinux = libbpf_find_kernel_btf();
        if (IS_ERR(btf_vmlinux))
                p_err("struct_ops requires kernel CONFIG_DEBUG_INFO_BTF=y");

        return btf_vmlinux;
}

static const char *get_kern_struct_ops_name(const struct bpf_map_info *info)
{
        const struct btf *kern_btf;
        const struct btf_type *t;
        const char *st_ops_name;

        kern_btf = get_btf_vmlinux();
        if (IS_ERR(kern_btf))
                return "<btf_vmlinux_not_found>";

        t = btf__type_by_id(kern_btf, info->btf_vmlinux_value_type_id);
        st_ops_name = btf__name_by_offset(kern_btf, t->name_off);
        st_ops_name += strlen(STRUCT_OPS_VALUE_PREFIX);

        return st_ops_name;
}

static __s32 get_map_info_type_id(void)
{
        const struct btf *kern_btf;

        if (map_info_type_id)
                return map_info_type_id;

        kern_btf = get_btf_vmlinux();
        if (IS_ERR(kern_btf)) {
                map_info_type_id = PTR_ERR(kern_btf);
                return map_info_type_id;
        }

        map_info_type_id = btf__find_by_name_kind(kern_btf, "bpf_map_info",
                                                  BTF_KIND_STRUCT);
        if (map_info_type_id < 0) {
                p_err("can't find bpf_map_info from btf_vmlinux");
                return map_info_type_id;
        }
        map_info_type = btf__type_by_id(kern_btf, map_info_type_id);

        /* Ensure map_info_alloc() has at least what the bpftool needs */
        map_info_alloc_len = map_info_type->size;
        if (map_info_alloc_len < sizeof(struct bpf_map_info))
                map_info_alloc_len = sizeof(struct bpf_map_info);

        return map_info_type_id;
}

/* If the subcmd needs to print out the bpf_map_info,
 * it should always call map_info_alloc to allocate
 * a bpf_map_info object instead of allocating it
 * on the stack.
 *
 * map_info_alloc() will take the running kernel's btf
 * into account.  i.e. it will consider the
 * sizeof(struct bpf_map_info) of the running kernel.
 *
 * It will enable the "struct_ops" cmd to print the latest
 * "struct bpf_map_info".
 *
 * [ Recall that "struct_ops" requires the kernel's btf to
 *   be available ]
 */
static struct bpf_map_info *map_info_alloc(__u32 *alloc_len)
{
        struct bpf_map_info *info;

        if (get_map_info_type_id() < 0)
                return NULL;

        info = calloc(1, map_info_alloc_len);
        if (!info)
                p_err("mem alloc failed");
        else
                *alloc_len = map_info_alloc_len;

        return info;
}

/* It iterates all struct_ops maps of the system.
 * It returns the fd in "*res_fd" and map_info in "*info".
 * In the very first iteration, info->id should be 0.
 * An optional map "*name" filter can be specified.
 * The filter can be made more flexible in the future.
 * e.g. filter by kernel-struct-ops-name, regex-name, glob-name, ...etc.
 *
 * Return value:
 *     1: A struct_ops map found.  It is returned in "*res_fd" and "*info".
 *        The caller can continue to call get_next in the future.
 *     0: No struct_ops map is returned.
 *        All struct_ops map has been found.
 *    -1: Error and the caller should abort the iteration.
 */
static int get_next_struct_ops_map(const char *name, int *res_fd,
                                   struct bpf_map_info *info, __u32 info_len)
{
        __u32 id = info->id;
        int err, fd;

        while (true) {
                err = bpf_map_get_next_id(id, &id);
                if (err) {
                        if (errno == ENOENT)
                                return 0;
                        p_err("can't get next map: %s", strerror(errno));
                        return -1;
                }

                fd = bpf_map_get_fd_by_id(id);
                if (fd < 0) {
                        if (errno == ENOENT)
                                continue;
                        p_err("can't get map by id (%u): %s",
                              id, strerror(errno));
                        return -1;
                }

                err = bpf_obj_get_info_by_fd(fd, info, &info_len);
                if (err) {
                        p_err("can't get map info: %s", strerror(errno));
                        close(fd);
                        return -1;
                }

                if (info->type == BPF_MAP_TYPE_STRUCT_OPS &&
                    (!name || !strcmp(name, info->name))) {
                        *res_fd = fd;
                        return 1;
                }
                close(fd);
        }
}

static int cmd_retval(const struct res *res, bool must_have_one_map)
{
        if (res->nr_errs || (!res->nr_maps && must_have_one_map))
                return -1;

        return 0;
}

/* "data" is the work_func private storage */
typedef int (*work_func)(int fd, const struct bpf_map_info *info, void *data,
                         struct json_writer *wtr);

/* Find all struct_ops map in the system.
 * Filter out by "name" (if specified).
 * Then call "func(fd, info, data, wtr)" on each struct_ops map found.
 */
static struct res do_search(const char *name, work_func func, void *data,
                            struct json_writer *wtr)
{
        struct bpf_map_info *info;
        struct res res = {};
        __u32 info_len;
        int fd, err;

        info = map_info_alloc(&info_len);
        if (!info) {
                res.nr_errs++;
                return res;
        }

        if (wtr)
                jsonw_start_array(wtr);
        while ((err = get_next_struct_ops_map(name, &fd, info, info_len)) == 1) {
                res.nr_maps++;
                err = func(fd, info, data, wtr);
                if (err)
                        res.nr_errs++;
                close(fd);
        }
        if (wtr)
                jsonw_end_array(wtr);

        if (err)
                res.nr_errs++;

        if (!wtr && name && !res.nr_errs && !res.nr_maps)
                /* It is not printing empty [].
                 * Thus, needs to specifically say nothing found
                 * for "name" here.
                 */
                p_err("no struct_ops found for %s", name);
        else if (!wtr && json_output && !res.nr_errs)
                /* The "func()" above is not writing any json (i.e. !wtr
                 * test here).
                 *
                 * However, "-j" is enabled and there is no errs here,
                 * so call json_null() as the current convention of
                 * other cmds.
                 */
                jsonw_null(json_wtr);

        free(info);
        return res;
}

static struct res do_one_id(const char *id_str, work_func func, void *data,
                            struct json_writer *wtr)
{
        struct bpf_map_info *info;
        struct res res = {};
        unsigned long id;
        __u32 info_len;
        char *endptr;
        int fd;

        id = strtoul(id_str, &endptr, 0);
        if (*endptr || !id || id > UINT32_MAX) {
                p_err("invalid id %s", id_str);
                res.nr_errs++;
                return res;
        }

        fd = bpf_map_get_fd_by_id(id);
        if (fd == -1) {
                p_err("can't get map by id (%lu): %s", id, strerror(errno));
                res.nr_errs++;
                return res;
        }

        info = map_info_alloc(&info_len);
        if (!info) {
                res.nr_errs++;
                goto done;
        }

        if (bpf_obj_get_info_by_fd(fd, info, &info_len)) {
                p_err("can't get map info: %s", strerror(errno));
                res.nr_errs++;
                goto done;
        }

        if (info->type != BPF_MAP_TYPE_STRUCT_OPS) {
                p_err("%s id %u is not a struct_ops map", info->name, info->id);
                res.nr_errs++;
                goto done;
        }

        res.nr_maps++;

        if (func(fd, info, data, wtr))
                res.nr_errs++;
        else if (!wtr && json_output)
                /* The "func()" above is not writing any json (i.e. !wtr
                 * test here).
                 *
                 * However, "-j" is enabled and there is no errs here,
                 * so call json_null() as the current convention of
                 * other cmds.
                 */
                jsonw_null(json_wtr);

done:
        free(info);
        close(fd);

        return res;
}

static struct res do_work_on_struct_ops(const char *search_type,
                                        const char *search_term,
                                        work_func func, void *data,
                                        struct json_writer *wtr)
{
        if (search_type) {
                if (is_prefix(search_type, "id"))
                        return do_one_id(search_term, func, data, wtr);
                else if (!is_prefix(search_type, "name"))
                        usage();
        }

        return do_search(search_term, func, data, wtr);
}

static int __do_show(int fd, const struct bpf_map_info *info, void *data,
                     struct json_writer *wtr)
{
        if (wtr) {
                jsonw_start_object(wtr);
                jsonw_uint_field(wtr, "id", info->id);
                jsonw_string_field(wtr, "name", info->name);
                jsonw_string_field(wtr, "kernel_struct_ops",
                                   get_kern_struct_ops_name(info));
                jsonw_end_object(wtr);
        } else {
                printf("%u: %-15s %-32s\n", info->id, info->name,
                       get_kern_struct_ops_name(info));
        }

        return 0;
}

static int do_show(int argc, char **argv)
{
        const char *search_type = NULL, *search_term = NULL;
        struct res res;

        if (argc && argc != 2)
                usage();

        if (argc == 2) {
                search_type = GET_ARG();
                search_term = GET_ARG();
        }

        res = do_work_on_struct_ops(search_type, search_term, __do_show,
                                    NULL, json_wtr);

        return cmd_retval(&res, !!search_term);
}

static int __do_dump(int fd, const struct bpf_map_info *info, void *data,
                     struct json_writer *wtr)
{
        struct btf_dumper *d = (struct btf_dumper *)data;
        const struct btf_type *struct_ops_type;
        const struct btf *kern_btf = d->btf;
        const char *struct_ops_name;
        int zero = 0;
        void *value;

        /* note: d->jw == wtr */

        kern_btf = d->btf;

        /* The kernel supporting BPF_MAP_TYPE_STRUCT_OPS must have
         * btf_vmlinux_value_type_id.
         */
        struct_ops_type = btf__type_by_id(kern_btf,
                                          info->btf_vmlinux_value_type_id);
        struct_ops_name = btf__name_by_offset(kern_btf,
                                              struct_ops_type->name_off);
        value = calloc(1, info->value_size);
        if (!value) {
                p_err("mem alloc failed");
                return -1;
        }

        if (bpf_map_lookup_elem(fd, &zero, value)) {
                p_err("can't lookup struct_ops map %s id %u",
                      info->name, info->id);
                free(value);
                return -1;
        }

        jsonw_start_object(wtr);
        jsonw_name(wtr, "bpf_map_info");
        btf_dumper_type(d, map_info_type_id, (void *)info);
        jsonw_end_object(wtr);

        jsonw_start_object(wtr);
        jsonw_name(wtr, struct_ops_name);
        btf_dumper_type(d, info->btf_vmlinux_value_type_id, value);
        jsonw_end_object(wtr);

        free(value);

        return 0;
}

static int do_dump(int argc, char **argv)
{
        const char *search_type = NULL, *search_term = NULL;
        json_writer_t *wtr = json_wtr;
        const struct btf *kern_btf;
        struct btf_dumper d = {};
        struct res res;

        if (argc && argc != 2)
                usage();

        if (argc == 2) {
                search_type = GET_ARG();
                search_term = GET_ARG();
        }

        kern_btf = get_btf_vmlinux();
        if (IS_ERR(kern_btf))
                return -1;

        if (!json_output) {
                wtr = jsonw_new(stdout);
                if (!wtr) {
                        p_err("can't create json writer");
                        return -1;
                }
                jsonw_pretty(wtr, true);
        }

        d.btf = kern_btf;
        d.jw = wtr;
        d.is_plain_text = !json_output;
        d.prog_id_as_func_ptr = true;

        res = do_work_on_struct_ops(search_type, search_term, __do_dump, &d,
                                    wtr);

        if (!json_output)
                jsonw_destroy(&wtr);

        return cmd_retval(&res, !!search_term);
}

static int __do_unregister(int fd, const struct bpf_map_info *info, void *data,
                           struct json_writer *wtr)
{
        int zero = 0;

        if (bpf_map_delete_elem(fd, &zero)) {
                p_err("can't unload %s %s id %u: %s",
                      get_kern_struct_ops_name(info), info->name,
                      info->id, strerror(errno));
                return -1;
        }

        p_info("Unregistered %s %s id %u",
               get_kern_struct_ops_name(info), info->name,
               info->id);

        return 0;
}

static int do_unregister(int argc, char **argv)
{
        const char *search_type, *search_term;
        struct res res;

        if (argc != 2)
                usage();

        search_type = GET_ARG();
        search_term = GET_ARG();

        res = do_work_on_struct_ops(search_type, search_term,
                                    __do_unregister, NULL, NULL);

        return cmd_retval(&res, true);
}

static int do_register(int argc, char **argv)
{
        struct bpf_object_load_attr load_attr = {};
        const struct bpf_map_def *def;
        struct bpf_map_info info = {};
        __u32 info_len = sizeof(info);
        int nr_errs = 0, nr_maps = 0;
        struct bpf_object *obj;
        struct bpf_link *link;
        struct bpf_map *map;
        const char *file;

        if (argc != 1)
                usage();

        file = GET_ARG();

        obj = bpf_object__open(file);
        if (IS_ERR_OR_NULL(obj))
                return -1;

        set_max_rlimit();

        load_attr.obj = obj;
        if (verifier_logs)
                /* log_level1 + log_level2 + stats, but not stable UAPI */
                load_attr.log_level = 1 + 2 + 4;

        if (bpf_object__load_xattr(&load_attr)) {
                bpf_object__close(obj);
                return -1;
        }

        bpf_object__for_each_map(map, obj) {
                def = bpf_map__def(map);
                if (def->type != BPF_MAP_TYPE_STRUCT_OPS)
                        continue;

                link = bpf_map__attach_struct_ops(map);
                if (IS_ERR(link)) {
                        p_err("can't register struct_ops %s: %s",
                              bpf_map__name(map),
                              strerror(-PTR_ERR(link)));
                        nr_errs++;
                        continue;
                }
                nr_maps++;

                bpf_link__disconnect(link);
                bpf_link__destroy(link);

                if (!bpf_obj_get_info_by_fd(bpf_map__fd(map), &info,
                                            &info_len))
                        p_info("Registered %s %s id %u",
                               get_kern_struct_ops_name(&info),
                               bpf_map__name(map),
                               info.id);
                else
                        /* Not p_err.  The struct_ops was attached
                         * successfully.
                         */
                        p_info("Registered %s but can't find id: %s",
                               bpf_map__name(map), strerror(errno));
        }

        bpf_object__close(obj);

        if (nr_errs)
                return -1;

        if (!nr_maps) {
                p_err("no struct_ops found in %s", file);
                return -1;
        }

        if (json_output)
                jsonw_null(json_wtr);

        return 0;
}

static int do_help(int argc, char **argv)
{
        if (json_output) {
                jsonw_null(json_wtr);
                return 0;
        }

        fprintf(stderr,
                "Usage: %1$s %2$s { show | list } [STRUCT_OPS_MAP]\n"
                "       %1$s %2$s dump [STRUCT_OPS_MAP]\n"
                "       %1$s %2$s register OBJ\n"
                "       %1$s %2$s unregister STRUCT_OPS_MAP\n"
                "       %1$s %2$s help\n"
                "\n"
                "       STRUCT_OPS_MAP := [ id STRUCT_OPS_MAP_ID | name STRUCT_OPS_MAP_NAME ]\n"
                "       " HELP_SPEC_OPTIONS " }\n"
                "",
                bin_name, argv[-2]);

        return 0;
}

static const struct cmd cmds[] = {
        { "show",       do_show },
        { "list",       do_show },
        { "register",   do_register },
        { "unregister", do_unregister },
        { "dump",       do_dump },
        { "help",       do_help },
        { 0 }
};

int do_struct_ops(int argc, char **argv)
{
        int err;

        err = cmd_select(cmds, argc, argv, do_help);

        if (!IS_ERR(btf_vmlinux))
                btf__free(btf_vmlinux);

        return err;
}