Merge pull request #645 from mihalicyn/runtime_dir_override

Allow overriding RUNTIME_DIR with a cli flag #2

Author: stgraber

meson.build

@@ -57,7 +57,7 @@ lxcmandir = join_paths(datadir, 'man')
 conf.set_quoted('BINDIR', bindir)
 conf.set_quoted('LIBDIR', libdir)
 conf.set_quoted('LOCALSTATEDIR', localstatedir)
-conf.set_quoted('RUNTIME_PATH', runtimepath)
+conf.set_quoted('DEFAULT_RUNTIME_PATH', runtimepath)
 conf.set_quoted('SYSCONFDIR', sysconfdir)
 
 conf.set_quoted('LXCCONFDIR', lxcconfdir)

src/bindings.c

@@ -7,6 +7,7 @@
 #include <fcntl.h>
 #include <inttypes.h>
 #include <libgen.h>
+#include <linux/limits.h>
 #include <linux/magic.h>
 #include <linux/sched.h>
 #include <pthread.h>
@@ -40,15 +41,32 @@
 #include "syscall_numbers.h"
 #include "utils.h"
 
+/* directory under which we mount the controllers - /run/lxcfs/controllers */
+#define BASEDIR "/lxcfs/controllers"
+#define ROOTDIR "/lxcfs/root"
+
 static bool can_use_pidfd;
 static bool can_use_swap;
 static bool can_use_sys_cpu;
 static bool has_versioned_opts;
 static bool memory_is_cgroupv2;
 static __u32 host_personality;
+static char runtime_path[PATH_MAX] = DEFAULT_RUNTIME_PATH;
+
 
 static volatile sig_atomic_t reload_successful;
 
+
+static char *get_base_dir(void)
+{
+	return must_make_path(runtime_path, BASEDIR, NULL);
+}
+
+static char *get_root_dir(void)
+{
+	return must_make_path(runtime_path, ROOTDIR, NULL);
+}
+
 bool liblxcfs_functional(void)
 {
 	return reload_successful != 0;
@@ -580,8 +598,9 @@ pid_t lookup_initpid_in_store(pid_t pid)
 
 static bool umount_if_mounted(void)
 {
-	if (umount2(BASEDIR, MNT_DETACH) < 0 && errno != EINVAL) {
-		lxcfs_error("Failed to unmount %s: %s.\n", BASEDIR, strerror(errno));
+	__do_free char *base_dir = get_base_dir();
+	if (umount2(base_dir, MNT_DETACH) < 0 && errno != EINVAL) {
+		lxcfs_error("Failed to unmount %s: %s.\n", base_dir, strerror(errno));
 		return false;
 	}
 	return true;
@@ -639,13 +658,14 @@ static bool is_on_ramfs(void)
 static int pivot_enter(void)
 {
 	__do_close int oldroot = -EBADF, newroot = -EBADF;
+	__do_free char *root_dir = get_root_dir();
 
 	oldroot = open("/", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
 	if (oldroot < 0)
 		return log_error_errno(-1, errno,
 				       "Failed to open old root for fchdir");
 
-	newroot = open(ROOTDIR, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+	newroot = open(root_dir, O_DIRECTORY | O_RDONLY | O_CLOEXEC);
 	if (newroot < 0)
 		return log_error_errno(-1, errno,
 				       "Failed to open new root for fchdir");
@@ -654,7 +674,7 @@ static int pivot_enter(void)
 	if (fchdir(newroot) < 0)
 		return log_error_errno(-1,
 				       errno, "Failed to change directory to new rootfs: %s",
-				       ROOTDIR);
+				       root_dir);
 
 	/* pivot_root into our new root fs */
 	if (pivot_root(".", ".") < 0)
@@ -681,8 +701,10 @@ static int pivot_enter(void)
 
 static int chroot_enter(void)
 {
-	if (mount(ROOTDIR, "/", NULL, MS_REC | MS_BIND, NULL)) {
-		lxcfs_error("Failed to recursively bind-mount %s into /.", ROOTDIR);
+	__do_free char *root_dir = get_root_dir();
+
+	if (mount(root_dir, "/", NULL, MS_REC | MS_BIND, NULL)) {
+		lxcfs_error("Failed to recursively bind-mount %s into /.", root_dir);
 		return -1;
 	}
 
@@ -725,23 +747,33 @@ static int permute_and_enter(void)
 /* Prepare our new clean root. */
 static int permute_prepare(void)
 {
-	if (mkdir(ROOTDIR, 0700) < 0 && errno != EEXIST) {
+	__do_free char *base_dir = get_base_dir();
+	__do_free char *root_dir = get_root_dir();
+	__do_free char *new_runtime = must_make_path(root_dir, runtime_path, NULL);
+	__do_free char *new_base_dir = must_make_path(root_dir, base_dir, NULL);
+
+	if (mkdir(root_dir, 0700) < 0 && errno != EEXIST) {
 		lxcfs_error("%s\n", "Failed to create directory for new root.");
 		return -1;
 	}
 
-	if (mount("/", ROOTDIR, NULL, MS_BIND, 0) < 0) {
+	if (mount("/", root_dir, NULL, MS_BIND, 0) < 0) {
 		lxcfs_error("Failed to bind-mount / for new root: %s.\n", strerror(errno));
 		return -1;
 	}
 
-	if (mount(RUNTIME_PATH, ROOTDIR RUNTIME_PATH, NULL, MS_BIND, 0) < 0) {
-		lxcfs_error("Failed to bind-mount /run into new root: %s.\n", strerror(errno));
+	if (!mkdir_p(new_runtime, 0700)) {
+		lxcfs_error("Failed to create dir %s\n", new_runtime);
+		return -1;
+	}
+
+	if (mount(runtime_path, new_runtime, NULL, MS_BIND, 0) < 0) {
+		lxcfs_error("Failed to bind-mount %s into new root: %s.\n", runtime_path, strerror(errno));
 		return -1;
 	}
 
-	if (mount(BASEDIR, ROOTDIR BASEDIR, NULL, MS_REC | MS_MOVE, 0) < 0) {
-		printf("Failed to move " BASEDIR " into new root: %s.\n", strerror(errno));
+	if (mount(base_dir, new_base_dir, NULL, MS_REC | MS_MOVE, 0) < 0) {
+		printf("Failed to move %s into new root: %s.\n", base_dir, strerror(errno));
 		return -1;
 	}
 
@@ -764,7 +796,9 @@ static bool permute_root(void)
 
 static bool cgfs_prepare_mounts(void)
 {
-	if (!mkdir_p(BASEDIR, 0700)) {
+	__do_free char *base_dir = get_base_dir();
+
+	if (!mkdir_p(base_dir, 0700)) {
 		lxcfs_error("%s\n", "Failed to create lxcfs cgroup mountpoint.");
 		return false;
 	}
@@ -790,7 +824,7 @@ static bool cgfs_prepare_mounts(void)
 		return false;
 	}
 
-	if (mount("tmpfs", BASEDIR, "tmpfs", 0, "size=100000,mode=700") < 0) {
+	if (mount("tmpfs", base_dir, "tmpfs", 0, "size=100000,mode=700") < 0) {
 		lxcfs_error("%s\n", "Failed to mount tmpfs over lxcfs cgroup mountpoint.");
 		return false;
 	}
@@ -800,14 +834,17 @@ static bool cgfs_prepare_mounts(void)
 
 static bool cgfs_mount_hierarchies(void)
 {
-	if (!mkdir_p(BASEDIR DEFAULT_CGROUP_MOUNTPOINT, 0755))
+	__do_free char *base_dir = get_base_dir();
+	__do_free char *base_dir_cgroup_mount = must_make_path(base_dir, DEFAULT_CGROUP_MOUNTPOINT, NULL);
+
+	if (!mkdir_p(base_dir_cgroup_mount, 0700))
 		return false;
 
-	if (!cgroup_ops->mount(cgroup_ops, BASEDIR))
+	if (!cgroup_ops->mount(cgroup_ops, base_dir))
 		return false;
 
 	for (struct hierarchy **h = cgroup_ops->hierarchies; h && *h; h++) {
-		__do_free char *path = must_make_path(BASEDIR, (*h)->mountpoint, NULL);
+		__do_free char *path = must_make_path(base_dir, (*h)->mountpoint, NULL);
 		(*h)->fd = open(path, O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
 		if ((*h)->fd < 0)
 			return false;
@@ -862,7 +899,19 @@ static void sigusr2_toggle_virtualization(int signo, siginfo_t *info, void *extr
 	return;
 }
 
-static void __attribute__((constructor)) lxcfs_init(void)
+bool set_runtime_path(const char* new_path)
+{
+	if (new_path && strlen(new_path) < PATH_MAX) {
+		strcpy(runtime_path, new_path);
+		lxcfs_info("Using runtime path %s", runtime_path);
+		return true;
+	} else {
+		lxcfs_error("%s\n", "Failed to overwrite the runtime path");
+		return false;
+	}
+}
+
+void lxcfslib_init(void)
 {
 	__do_close int init_ns = -EBADF, root_fd = -EBADF,
 				  pidfd = -EBADF;
@@ -871,7 +920,7 @@ static void __attribute__((constructor)) lxcfs_init(void)
 	pid_t pid;
 	struct hierarchy *hierarchy;
 
-	lxcfs_info("Running constructor %s to reload liblxcfs", __func__);
+	lxcfs_info("Running %s to reload liblxcfs", __func__);
 
 	cgroup_ops = cgroup_init();
 	if (!cgroup_ops) {
@@ -971,9 +1020,20 @@ static void __attribute__((destructor)) lxcfs_exit(void)
 void *lxcfs_fuse_init(struct fuse_conn_info *conn, void *data)
 {
 	struct fuse_context *fc = fuse_get_context();
+	struct lxcfs_opts *opts = fc ? fc->private_data : NULL;
+
 #if HAVE_FUSE_RETURNS_DT_TYPE
 	can_use_sys_cpu = true;
 #endif
 	has_versioned_opts = true;
-	return fc ? fc->private_data : NULL;
+
+	// We can read runtime_path as of opts version 2.
+	if (opts && opts->version >= 2) {
+		set_runtime_path(opts->runtime_path);
+	}
+
+	/* initialize the library */
+	lxcfslib_init();
+
+	return opts;
 }

src/bindings.h

@@ -23,10 +23,6 @@
 #include "proc_loadavg.h"
 #include "sysfs_fuse.h"
 
-/* directory under which we mount the controllers - /run/lxcfs/controllers */
-#define BASEDIR RUNTIME_PATH "/lxcfs/controllers"
-#define ROOTDIR RUNTIME_PATH "/lxcfs/root"
-
 /* Maximum number for 64 bit integer is a string with 21 digits: 2^64 - 1 = 21 */
 #define LXCFS_NUMSTRLEN64 21
 
@@ -116,6 +112,8 @@ struct lxcfs_opts {
 	 * and the use of bool instead of explicited __u32 and __u64 we can't.
 	 */
 	__u32 version;
+        // As of opts version 2.
+        char runtime_path[PATH_MAX];
 };
 
 typedef enum lxcfs_opt_t {

src/lxcfs.c

@@ -32,7 +32,11 @@
 #include "macro.h"
 #include "memory_utils.h"
 
+#define PID_FILE "/lxcfs.pid"
+
 void *dlopen_handle;
+static char runtime_path[PATH_MAX] = DEFAULT_RUNTIME_PATH;
+
 
 /* Functions to keep track of number of threads using the library */
 
@@ -146,7 +150,7 @@ static int stop_loadavg(void)
 
 static volatile sig_atomic_t need_reload;
 
-static int lxcfs_init_library(void)
+static int do_lxcfs_fuse_init(void)
 {
 	char *error;
 	void *(*__lxcfs_fuse_init)(struct fuse_conn_info * conn, void * cfg);
@@ -199,13 +203,12 @@ static void do_reload(bool reinit)
 
         dlopen_handle = dlopen(lxcfs_lib_path, RTLD_LAZY);
 	if (!dlopen_handle)
-		log_exit("%s - Failed to open liblxcfs.so", dlerror());
+		log_exit("%s - Failed to open liblxcfs.so at %s", dlerror(), lxcfs_lib_path);
 	else
 		lxcfs_debug("Opened %s", lxcfs_lib_path);
 
 good:
-	/* initialize the library */
-	if (reinit && lxcfs_init_library() < 0) {
+	if (reinit && do_lxcfs_fuse_init() < 0) {
 		log_exit("Failed to initialize liblxcfs.so");
 	}
 
@@ -1119,7 +1122,7 @@ static void *lxcfs_init(struct fuse_conn_info *conn, struct fuse_config *cfg)
 static void *lxcfs_init(struct fuse_conn_info *conn)
 #endif
 {
-	if (lxcfs_init_library() < 0)
+	if (do_lxcfs_fuse_init() < 0)
 		return NULL;
 
 #if HAVE_FUSE3
@@ -1187,12 +1190,14 @@ static void usage(void)
 	lxcfs_info("  -l, --enable-loadavg Enable loadavg virtualization");
 	lxcfs_info("  -o                   Options to pass directly through fuse");
 	lxcfs_info("  -p, --pidfile=FILE   Path to use for storing lxcfs pid");
-	lxcfs_info("                       Default pidfile is %s/lxcfs.pid", RUNTIME_PATH);
+	lxcfs_info("                       Default pidfile is %s/lxcfs.pid", DEFAULT_RUNTIME_PATH);
 	lxcfs_info("  -u, --disable-swap   Disable swap virtualization");
 	lxcfs_info("  -v, --version        Print lxcfs version");
 	lxcfs_info("  --enable-cfs         Enable CPU virtualization via CPU shares");
 	lxcfs_info("  --enable-pidfd       Use pidfd for process tracking");
 	lxcfs_info("  --enable-cgroup      Enable cgroup emulation code");
+	lxcfs_info("  --runtime-dir=DIR    Path to use as the runtime directory.");
+	lxcfs_info("                       Default is %s", DEFAULT_RUNTIME_PATH);
 	exit(EXIT_FAILURE);
 }
 
@@ -1244,6 +1249,7 @@ static const struct option long_options[] = {
 	{"enable-cgroup",	no_argument,		0,	  0	},
 
 	{"pidfile",		required_argument,	0,	'p'	},
+	{"runtime-dir",		required_argument,	0,	  0	},
 	{								},
 };
 
@@ -1286,7 +1292,7 @@ int main(int argc, char *argv[])
 	int pidfile_fd = -EBADF;
 	int ret = EXIT_FAILURE;
 	char *pidfile = NULL, *token = NULL;
-	char pidfile_buf[STRLITERALLEN(RUNTIME_PATH) + STRLITERALLEN("/lxcfs.pid") + 1] = {};
+	char pidfile_buf[PATH_MAX + sizeof(PID_FILE)] = {};
 	bool debug = false, foreground = false;
 #if !HAVE_FUSE3
 	bool nonempty = false;
@@ -1303,6 +1309,7 @@ int main(int argc, char *argv[])
 	char *new_fuse_opts = NULL;
 	char *const *new_argv;
 	struct lxcfs_opts *opts;
+	char *runtime_path_arg = NULL;
 
 	opts = malloc(sizeof(struct lxcfs_opts));
 	if (opts == NULL) {
@@ -1313,7 +1320,7 @@ int main(int argc, char *argv[])
 	opts->swap_off = false;
 	opts->use_pidfd = false;
 	opts->use_cfs = false;
-	opts->version = 1;
+	opts->version = 2;
 
 	while ((c = getopt_long(argc, argv, "dulfhvso:p:", long_options, &idx)) != -1) {
 		switch (c) {
@@ -1324,6 +1331,8 @@ int main(int argc, char *argv[])
 				opts->use_cfs = true;
 			else if (strcmp(long_options[idx].name, "enable-cgroup") == 0)
 				cgroup_is_enabled = true;
+			else if (strcmp(long_options[idx].name, "runtime-dir") == 0)
+				runtime_path_arg = optarg;
 			else
 				usage();
 			break;
@@ -1376,6 +1385,12 @@ int main(int argc, char *argv[])
 		goto out;
 	}
 
+	if (runtime_path_arg) {
+		strcpy(runtime_path, runtime_path_arg);
+		lxcfs_info("runtime path set to %s", runtime_path);
+	}
+	strcpy(opts->runtime_path, runtime_path);
+
 	fuse_argv[fuse_argc++] = argv[0];
 	if (debug)
 		fuse_argv[fuse_argc++] = "-d";
@@ -1467,6 +1482,7 @@ int main(int argc, char *argv[])
 	lxcfs_info("Starting LXCFS at %s", argv[0]);
 
 	do_reload(false);
+
 	if (install_signal_handler(SIGUSR1, sigusr1_reload)) {
 		lxcfs_error("%s - Failed to install SIGUSR1 signal handler", strerror(errno));
 		goto out;
@@ -1480,7 +1496,7 @@ int main(int argc, char *argv[])
 #endif
 
 	if (!pidfile) {
-		snprintf(pidfile_buf, sizeof(pidfile_buf), "%s/lxcfs.pid", RUNTIME_PATH);
+		snprintf(pidfile_buf, sizeof(pidfile_buf), "%s%s", runtime_path, PID_FILE);
 		pidfile = pidfile_buf;
 	}
 

tests/main.sh.in

@@ -49,7 +49,7 @@ if [ -x ${lxcfs} ]; then
 	LXCFSPID=$!
 else
 	UNSHARE=0
-	LXCFSPID=$(cat "{{RUNTIME_PATH}}/lxcfs.pid")
+	LXCFSPID=$(cat "{{DEFAULT_RUNTIME_PATH}}/lxcfs.pid")
 	echo "=> Re-using host lxcfs"
 	rmdir $LXCFSDIR
 	export LXCFSDIR=/var/lib/lxcfs