// SPDX-License-Identifier: GPL-2.0
/*
 * Landlock filesystem benchmark
 *
 * This program benchmarks the time required for file access checks.  We use a
 * large number (-d flag) of nested directories where each directory inode has
 * an associated Landlock rule, and we repeatedly (-n flag) exercise a file
 * access for which Landlock has to walk the path all the way up to the root.
 *
 * With an increasing number of nested subdirectories, Landlock's portion of the
 * overall system call time increases, which makes the effects of Landlock
 * refactorings more measurable.
 *
 * This benchmark does *not* measure the building of the Landlock ruleset.  The
 * time required to add all these rules is not large enough to be easily
 * measurable.  A separate benchmark tool would be better to test that, and that
 * tool could then also use a simpler file system layout.
 *
 * Copyright © 2026 Google LLC
 */

#define _GNU_SOURCE
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/landlock.h>
#include <linux/prctl.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/times.h>
#include <time.h>
#include <unistd.h>

#include "wrappers.h"

static void usage(const char *const argv0)
{
        printf("Usage:\n");
        printf("  %s [OPTIONS]\n", argv0);
        printf("\n");
        printf("  Benchmark expensive Landlock checks for D nested dirs\n");
        printf("\n");
        printf("Options:\n");
        printf("  -h    help\n");
        printf("  -L    disable Landlock (as a baseline)\n");
        printf("  -d D  set directory depth to D\n");
        printf("  -n N  set number of benchmark iterations to N\n");
}

/*
 * Build a deep directory, enforce Landlock and return the FD to the
 * deepest dir.  On any failure, exit the process with an error.
 */
static int build_directory(size_t depth, const bool use_landlock)
{
        const char *path = "d"; /* directory name */
        int abi, ruleset_fd, curr, prev;

        if (use_landlock) {
                abi = landlock_create_ruleset(NULL, 0,
                                              LANDLOCK_CREATE_RULESET_VERSION);
                if (abi < 7)
                        err(1, "Landlock ABI too low: got %d, wanted 7+", abi);
        }

        ruleset_fd = -1;
        if (use_landlock) {
                struct landlock_ruleset_attr attr = {
                        .handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV |
                                             LANDLOCK_ACCESS_FS_WRITE_FILE |
                                             LANDLOCK_ACCESS_FS_MAKE_REG,
                };
                ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0U);
                if (ruleset_fd < 0)
                        err(1, "landlock_create_ruleset");
        }

        curr = open(".", O_PATH);
        if (curr < 0)
                err(1, "open(.)");

        while (depth--) {
                if (use_landlock) {
                        struct landlock_path_beneath_attr attr = {
                                .allowed_access = LANDLOCK_ACCESS_FS_IOCTL_DEV,
                                .parent_fd = curr,
                        };
                        if (landlock_add_rule(ruleset_fd,
                                              LANDLOCK_RULE_PATH_BENEATH, &attr,
                                              0) < 0)
                                err(1, "landlock_add_rule");
                }

                if (mkdirat(curr, path, 0700) < 0)
                        err(1, "mkdirat(%s)", path);

                prev = curr;
                curr = openat(curr, path, O_PATH);
                if (curr < 0)
                        err(1, "openat(%s)", path);

                close(prev);
        }

        if (use_landlock) {
                if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0)
                        err(1, "prctl");

                if (landlock_restrict_self(ruleset_fd, 0) < 0)
                        err(1, "landlock_restrict_self");
        }

        close(ruleset_fd);
        return curr;
}

static void remove_recursively(const size_t depth)
{
        const char *path = "d"; /* directory name */

        int fd = openat(AT_FDCWD, ".", O_PATH);

        if (fd < 0)
                err(1, "openat(.)");

        for (size_t i = 0; i < depth - 1; i++) {
                int oldfd = fd;

                fd = openat(fd, path, O_PATH);
                if (fd < 0)
                        err(1, "openat(%s)", path);
                close(oldfd);
        }

        for (size_t i = 0; i < depth; i++) {
                if (unlinkat(fd, path, AT_REMOVEDIR) < 0)
                        err(1, "unlinkat(%s)", path);
                int newfd = openat(fd, "..", O_PATH);

                close(fd);
                fd = newfd;
        }
        close(fd);
}

int main(int argc, char *argv[])
{
        bool use_landlock = true;
        size_t num_iterations = 100000;
        size_t num_subdirs = 10000;
        int c, curr, fd;
        struct tms start_time, end_time;

        setbuf(stdout, NULL);
        while ((c = getopt(argc, argv, "hLd:n:")) != -1) {
                switch (c) {
                case 'h':
                        usage(argv[0]);
                        return EXIT_SUCCESS;
                case 'L':
                        use_landlock = false;
                        break;
                case 'd':
                        num_subdirs = atoi(optarg);
                        break;
                case 'n':
                        num_iterations = atoi(optarg);
                        break;
                default:
                        usage(argv[0]);
                        return EXIT_FAILURE;
                }
        }

        printf("*** Benchmark ***\n");
        printf("%zu dirs, %zu iterations, %s Landlock\n", num_subdirs,
               num_iterations, use_landlock ? "with" : "without");

        if (times(&start_time) == -1)
                err(1, "times");

        curr = build_directory(num_subdirs, use_landlock);

        for (int i = 0; i < num_iterations; i++) {
                fd = openat(curr, "file.txt", O_CREAT | O_TRUNC | O_WRONLY,
                            0600);
                if (use_landlock) {
                        if (fd == 0)
                                errx(1, "openat succeeded, expected EACCES");
                        if (errno != EACCES)
                                err(1, "openat expected EACCES, but got");
                }
                if (fd != -1)
                        close(fd);
        }

        if (times(&end_time) == -1)
                err(1, "times");

        printf("*** Benchmark concluded ***\n");
        printf("System: %ld clocks\n",
               end_time.tms_stime - start_time.tms_stime);
        printf("User  : %ld clocks\n",
               end_time.tms_utime - start_time.tms_utime);
        printf("Clocks per second: %ld\n", CLOCKS_PER_SEC);

        close(curr);

        remove_recursively(num_subdirs);
}