// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
#define _GNU_SOURCE
#include <test_progs.h>
#include <bpf/btf.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/unistd.h>
#include <linux/mount.h>
#include <sys/syscall.h>
#include "bpf/libbpf_internal.h"
static inline int sys_fsopen(const char *fsname, unsigned flags)
{
return syscall(__NR_fsopen, fsname, flags);
}
static inline int sys_fsconfig(int fs_fd, unsigned cmd, const char *key, const void *val, int aux)
{
return syscall(__NR_fsconfig, fs_fd, cmd, key, val, aux);
}
static inline int sys_fsmount(int fs_fd, unsigned flags, unsigned ms_flags)
{
return syscall(__NR_fsmount, fs_fd, flags, ms_flags);
}
__attribute__((unused))
static inline int sys_move_mount(int from_dfd, const char *from_path,
int to_dfd, const char *to_path,
unsigned int ms_flags)
{
return syscall(__NR_move_mount, from_dfd, from_path, to_dfd, to_path, ms_flags);
}
static void bpf_obj_pinning_detached(void)
{
LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
int fs_fd = -1, mnt_fd = -1;
int map_fd = -1, map_fd2 = -1;
int zero = 0, src_value, dst_value, err;
const char *map_name = "fsmount_map";
/* A bunch of below UAPI calls are constructed based on reading:
* https://brauner.io/2023/02/28/mounting-into-mount-namespaces.html
*/
/* create VFS context */
fs_fd = sys_fsopen("bpf", 0);
if (!ASSERT_GE(fs_fd, 0, "fs_fd"))
goto cleanup;
/* instantiate FS object */
err = sys_fsconfig(fs_fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
if (!ASSERT_OK(err, "fs_create"))
goto cleanup;
/* create O_PATH fd for detached mount */
mnt_fd = sys_fsmount(fs_fd, 0, 0);
if (!ASSERT_GE(mnt_fd, 0, "mnt_fd"))
goto cleanup;
/* If we wanted to expose detached mount in the file system, we'd do
* something like below. But the whole point is that we actually don't
* even have to expose BPF FS in the file system to be able to work
* (pin/get objects) with it.
*
* err = sys_move_mount(mnt_fd, "", -EBADF, mnt_path, MOVE_MOUNT_F_EMPTY_PATH);
* if (!ASSERT_OK(err, "move_mount"))
* goto cleanup;
*/
/* create BPF map to pin */
map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
if (!ASSERT_GE(map_fd, 0, "map_fd"))
goto cleanup;
/* pin BPF map into detached BPF FS through mnt_fd */
pin_opts.file_flags = BPF_F_PATH_FD;
pin_opts.path_fd = mnt_fd;
err = bpf_obj_pin_opts(map_fd, map_name, &pin_opts);
if (!ASSERT_OK(err, "map_pin"))
goto cleanup;
/* get BPF map from detached BPF FS through mnt_fd */
get_opts.file_flags = BPF_F_PATH_FD;
get_opts.path_fd = mnt_fd;
map_fd2 = bpf_obj_get_opts(map_name, &get_opts);
if (!ASSERT_GE(map_fd2, 0, "map_get"))
goto cleanup;
/* update map through one FD */
src_value = 0xcafebeef;
err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
ASSERT_OK(err, "map_update");
/* check values written/read through different FDs do match */
dst_value = 0;
err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
ASSERT_OK(err, "map_lookup");
ASSERT_EQ(dst_value, src_value, "map_value_eq1");
ASSERT_EQ(dst_value, 0xcafebeef, "map_value_eq2");
cleanup:
if (map_fd >= 0)
ASSERT_OK(close(map_fd), "close_map_fd");
if (map_fd2 >= 0)
ASSERT_OK(close(map_fd2), "close_map_fd2");
if (fs_fd >= 0)
ASSERT_OK(close(fs_fd), "close_fs_fd");
if (mnt_fd >= 0)
ASSERT_OK(close(mnt_fd), "close_mnt_fd");
}
enum path_kind
{
PATH_STR_ABS,
PATH_STR_REL,
PATH_FD_REL,
};
static void validate_pin(int map_fd, const char *map_name, int src_value,
enum path_kind path_kind)
{
LIBBPF_OPTS(bpf_obj_pin_opts, pin_opts);
char abs_path[PATH_MAX], old_cwd[PATH_MAX];
const char *pin_path = NULL;
int zero = 0, dst_value, map_fd2, err;
snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
old_cwd[0] = '\0';
switch (path_kind) {
case PATH_STR_ABS:
/* absolute path */
pin_path = abs_path;
break;
case PATH_STR_REL:
/* cwd + relative path */
ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
pin_path = map_name;
break;
case PATH_FD_REL:
/* dir fd + relative path */
pin_opts.file_flags = BPF_F_PATH_FD;
pin_opts.path_fd = open("/sys/fs/bpf", O_PATH);
ASSERT_GE(pin_opts.path_fd, 0, "path_fd");
pin_path = map_name;
break;
}
/* pin BPF map using specified path definition */
err = bpf_obj_pin_opts(map_fd, pin_path, &pin_opts);
ASSERT_OK(err, "obj_pin");
/* cleanup */
if (path_kind == PATH_FD_REL && pin_opts.path_fd >= 0)
close(pin_opts.path_fd);
if (old_cwd[0])
ASSERT_OK(chdir(old_cwd), "restore_cwd");
map_fd2 = bpf_obj_get(abs_path);
if (!ASSERT_GE(map_fd2, 0, "map_get"))
goto cleanup;
/* update map through one FD */
err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
ASSERT_OK(err, "map_update");
/* check values written/read through different FDs do match */
dst_value = 0;
err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
ASSERT_OK(err, "map_lookup");
ASSERT_EQ(dst_value, src_value, "map_value_eq");
cleanup:
if (map_fd2 >= 0)
ASSERT_OK(close(map_fd2), "close_map_fd2");
unlink(abs_path);
}
static void validate_get(int map_fd, const char *map_name, int src_value,
enum path_kind path_kind)
{
LIBBPF_OPTS(bpf_obj_get_opts, get_opts);
char abs_path[PATH_MAX], old_cwd[PATH_MAX];
const char *pin_path = NULL;
int zero = 0, dst_value, map_fd2, err;
snprintf(abs_path, sizeof(abs_path), "/sys/fs/bpf/%s", map_name);
/* pin BPF map using specified path definition */
err = bpf_obj_pin(map_fd, abs_path);
if (!ASSERT_OK(err, "pin_map"))
return;
old_cwd[0] = '\0';
switch (path_kind) {
case PATH_STR_ABS:
/* absolute path */
pin_path = abs_path;
break;
case PATH_STR_REL:
/* cwd + relative path */
ASSERT_OK_PTR(getcwd(old_cwd, sizeof(old_cwd)), "getcwd");
ASSERT_OK(chdir("/sys/fs/bpf"), "chdir");
pin_path = map_name;
break;
case PATH_FD_REL:
/* dir fd + relative path */
get_opts.file_flags = BPF_F_PATH_FD;
get_opts.path_fd = open("/sys/fs/bpf", O_PATH);
ASSERT_GE(get_opts.path_fd, 0, "path_fd");
pin_path = map_name;
break;
}
map_fd2 = bpf_obj_get_opts(pin_path, &get_opts);
if (!ASSERT_GE(map_fd2, 0, "map_get"))
goto cleanup;
/* cleanup */
if (path_kind == PATH_FD_REL && get_opts.path_fd >= 0)
close(get_opts.path_fd);
if (old_cwd[0])
ASSERT_OK(chdir(old_cwd), "restore_cwd");
/* update map through one FD */
err = bpf_map_update_elem(map_fd, &zero, &src_value, 0);
ASSERT_OK(err, "map_update");
/* check values written/read through different FDs do match */
dst_value = 0;
err = bpf_map_lookup_elem(map_fd2, &zero, &dst_value);
ASSERT_OK(err, "map_lookup");
ASSERT_EQ(dst_value, src_value, "map_value_eq");
cleanup:
if (map_fd2 >= 0)
ASSERT_OK(close(map_fd2), "close_map_fd2");
unlink(abs_path);
}
static void bpf_obj_pinning_mounted(enum path_kind path_kind)
{
const char *map_name = "mounted_map";
int map_fd;
/* create BPF map to pin */
map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, map_name, 4, 4, 1, NULL);
if (!ASSERT_GE(map_fd, 0, "map_fd"))
return;
validate_pin(map_fd, map_name, 100 + (int)path_kind, path_kind);
validate_get(map_fd, map_name, 200 + (int)path_kind, path_kind);
ASSERT_OK(close(map_fd), "close_map_fd");
}
void test_bpf_obj_pinning()
{
if (test__start_subtest("detached"))
bpf_obj_pinning_detached();
if (test__start_subtest("mounted-str-abs"))
bpf_obj_pinning_mounted(PATH_STR_ABS);
if (test__start_subtest("mounted-str-rel"))
bpf_obj_pinning_mounted(PATH_STR_REL);
if (test__start_subtest("mounted-fd-rel"))
bpf_obj_pinning_mounted(PATH_FD_REL);
}
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