// SPDX-License-Identifier: GPL-2.0-or-later
// Copyright (c) 2024 Christian Brauner <brauner@kernel.org>

#define _GNU_SOURCE
#include <errno.h>
#include <limits.h>
#include <linux/types.h>
#include <inttypes.h>
#include <stdio.h>

#include "../../tools/testing/selftests/pidfd/pidfd.h"
#include "samples-vfs.h"

static int __statmount(__u64 mnt_id, __u64 mnt_ns_id, __u64 mask,
                       struct statmount *stmnt, size_t bufsize,
                       unsigned int flags)
{
        struct mnt_id_req req = {
                .size           = MNT_ID_REQ_SIZE_VER1,
                .mnt_id         = mnt_id,
                .param          = mask,
                .mnt_ns_id      = mnt_ns_id,
        };

        return syscall(__NR_statmount, &req, stmnt, bufsize, flags);
}

static struct statmount *sys_statmount(__u64 mnt_id, __u64 mnt_ns_id,
                                       __u64 mask, unsigned int flags)
{
        size_t bufsize = 1 << 15;
        struct statmount *stmnt = NULL, *tmp = NULL;
        int ret;

        for (;;) {
                tmp = realloc(stmnt, bufsize);
                if (!tmp)
                        goto out;

                stmnt = tmp;
                ret = __statmount(mnt_id, mnt_ns_id, mask, stmnt, bufsize, flags);
                if (!ret)
                        return stmnt;

                if (errno != EOVERFLOW)
                        goto out;

                bufsize <<= 1;
                if (bufsize >= UINT_MAX / 2)
                        goto out;
        }

out:
        free(stmnt);
        return NULL;
}

static ssize_t sys_listmount(__u64 mnt_id, __u64 last_mnt_id, __u64 mnt_ns_id,
                             __u64 list[], size_t num, unsigned int flags)
{
        struct mnt_id_req req = {
                .size           = MNT_ID_REQ_SIZE_VER1,
                .mnt_id         = mnt_id,
                .param          = last_mnt_id,
                .mnt_ns_id      = mnt_ns_id,
        };

        return syscall(__NR_listmount, &req, list, num, flags);
}

int main(int argc, char *argv[])
{
#define LISTMNT_BUFFER 10
        __u64 list[LISTMNT_BUFFER], last_mnt_id = 0;
        int ret, pidfd, fd_mntns;
        struct mnt_ns_info info = {};

        pidfd = sys_pidfd_open(getpid(), 0);
        if (pidfd < 0)
                die_errno("pidfd_open failed");

        fd_mntns = ioctl(pidfd, PIDFD_GET_MNT_NAMESPACE, 0);
        if (fd_mntns < 0)
                die_errno("ioctl(PIDFD_GET_MNT_NAMESPACE) failed");

        ret = ioctl(fd_mntns, NS_MNT_GET_INFO, &info);
        if (ret < 0)
                die_errno("ioctl(NS_GET_MNTNS_ID) failed");

        printf("Listing %u mounts for mount namespace %" PRIu64 "\n",
               info.nr_mounts, (uint64_t)info.mnt_ns_id);
        for (;;) {
                ssize_t nr_mounts;
next:
                nr_mounts = sys_listmount(LSMT_ROOT, last_mnt_id,
                                          info.mnt_ns_id, list, LISTMNT_BUFFER,
                                          0);
                if (nr_mounts <= 0) {
                        int fd_mntns_next;

                        printf("Finished listing %u mounts for mount namespace %" PRIu64 "\n\n",
                               info.nr_mounts, (uint64_t)info.mnt_ns_id);
                        fd_mntns_next = ioctl(fd_mntns, NS_MNT_GET_NEXT, &info);
                        if (fd_mntns_next < 0) {
                                if (errno == ENOENT) {
                                        printf("Finished listing all mount namespaces\n");
                                        exit(0);
                                }
                                die_errno("ioctl(NS_MNT_GET_NEXT) failed");
                        }
                        close(fd_mntns);
                        fd_mntns = fd_mntns_next;
                        last_mnt_id = 0;
                        printf("Listing %u mounts for mount namespace %" PRIu64 "\n",
                               info.nr_mounts, (uint64_t)info.mnt_ns_id);
                        goto next;
                }

                for (size_t cur = 0; cur < nr_mounts; cur++) {
                        struct statmount *stmnt;

                        last_mnt_id = list[cur];

                        stmnt = sys_statmount(last_mnt_id, info.mnt_ns_id,
                                              STATMOUNT_SB_BASIC |
                                              STATMOUNT_MNT_BASIC |
                                              STATMOUNT_MNT_ROOT |
                                              STATMOUNT_MNT_POINT |
                                              STATMOUNT_MNT_NS_ID |
                                              STATMOUNT_MNT_OPTS |
                                              STATMOUNT_FS_TYPE |
                                              STATMOUNT_MNT_UIDMAP |
                                              STATMOUNT_MNT_GIDMAP, 0);
                        if (!stmnt) {
                                printf("Failed to statmount(%" PRIu64 ") in mount namespace(%" PRIu64 ")\n",
                                       (uint64_t)last_mnt_id, (uint64_t)info.mnt_ns_id);
                                continue;
                        }

                        printf("mnt_id:\t\t%" PRIu64 "\nmnt_parent_id:\t%" PRIu64 "\nfs_type:\t%s\nmnt_root:\t%s\nmnt_point:\t%s\nmnt_opts:\t%s\n",
                               (uint64_t)stmnt->mnt_id,
                               (uint64_t)stmnt->mnt_parent_id,
                               (stmnt->mask & STATMOUNT_FS_TYPE)   ? stmnt->str + stmnt->fs_type   : "",
                               (stmnt->mask & STATMOUNT_MNT_ROOT)  ? stmnt->str + stmnt->mnt_root  : "",
                               (stmnt->mask & STATMOUNT_MNT_POINT) ? stmnt->str + stmnt->mnt_point : "",
                               (stmnt->mask & STATMOUNT_MNT_OPTS)  ? stmnt->str + stmnt->mnt_opts  : "");

                        if (stmnt->mask & STATMOUNT_MNT_UIDMAP) {
                                const char *idmap = stmnt->str + stmnt->mnt_uidmap;

                                for (size_t idx = 0; idx < stmnt->mnt_uidmap_num; idx++) {
                                        printf("mnt_uidmap[%zu]:\t%s\n", idx, idmap);
                                        idmap += strlen(idmap) + 1;
                                }
                        }

                        if (stmnt->mask & STATMOUNT_MNT_GIDMAP) {
                                const char *idmap = stmnt->str + stmnt->mnt_gidmap;

                                for (size_t idx = 0; idx < stmnt->mnt_gidmap_num; idx++) {
                                        printf("mnt_gidmap[%zu]:\t%s\n", idx, idmap);
                                        idmap += strlen(idmap) + 1;
                                }
                        }

                        printf("\n");

                        free(stmnt);
                }
        }

        exit(0);
}