1 files changed, 313 insertions, 83 deletions

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index 65303664417e..958e92acca8e 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 /* Copyright (C) 2017-2018 Netronome Systems, Inc. */
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -13,16 +15,21 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <linux/limits.h>
-#include <linux/magic.h>
 #include <net/if.h>
 #include <sys/mount.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/vfs.h>
 
+#include <linux/filter.h>
+#include <linux/limits.h>
+#include <linux/magic.h>
+#include <linux/unistd.h>
+
 #include <bpf/bpf.h>
+#include <bpf/hashmap.h>
 #include <bpf/libbpf.h> /* libbpf_num_possible_cpus */
+#include <bpf/btf.h>
 
 #include "main.h"
 
@@ -30,44 +37,6 @@
 #define BPF_FS_MAGIC		0xcafe4a11
 #endif
 
-const char * const attach_type_name[__MAX_BPF_ATTACH_TYPE] = {
-	[BPF_CGROUP_INET_INGRESS]	= "ingress",
-	[BPF_CGROUP_INET_EGRESS]	= "egress",
-	[BPF_CGROUP_INET_SOCK_CREATE]	= "sock_create",
-	[BPF_CGROUP_INET_SOCK_RELEASE]	= "sock_release",
-	[BPF_CGROUP_SOCK_OPS]		= "sock_ops",
-	[BPF_CGROUP_DEVICE]		= "device",
-	[BPF_CGROUP_INET4_BIND]		= "bind4",
-	[BPF_CGROUP_INET6_BIND]		= "bind6",
-	[BPF_CGROUP_INET4_CONNECT]	= "connect4",
-	[BPF_CGROUP_INET6_CONNECT]	= "connect6",
-	[BPF_CGROUP_INET4_POST_BIND]	= "post_bind4",
-	[BPF_CGROUP_INET6_POST_BIND]	= "post_bind6",
-	[BPF_CGROUP_INET4_GETPEERNAME]	= "getpeername4",
-	[BPF_CGROUP_INET6_GETPEERNAME]	= "getpeername6",
-	[BPF_CGROUP_INET4_GETSOCKNAME]	= "getsockname4",
-	[BPF_CGROUP_INET6_GETSOCKNAME]	= "getsockname6",
-	[BPF_CGROUP_UDP4_SENDMSG]	= "sendmsg4",
-	[BPF_CGROUP_UDP6_SENDMSG]	= "sendmsg6",
-	[BPF_CGROUP_SYSCTL]		= "sysctl",
-	[BPF_CGROUP_UDP4_RECVMSG]	= "recvmsg4",
-	[BPF_CGROUP_UDP6_RECVMSG]	= "recvmsg6",
-	[BPF_CGROUP_GETSOCKOPT]		= "getsockopt",
-	[BPF_CGROUP_SETSOCKOPT]		= "setsockopt",
-
-	[BPF_SK_SKB_STREAM_PARSER]	= "sk_skb_stream_parser",
-	[BPF_SK_SKB_STREAM_VERDICT]	= "sk_skb_stream_verdict",
-	[BPF_SK_MSG_VERDICT]		= "sk_msg_verdict",
-	[BPF_LIRC_MODE2]		= "lirc_mode2",
-	[BPF_FLOW_DISSECTOR]		= "flow_dissector",
-	[BPF_TRACE_RAW_TP]		= "raw_tp",
-	[BPF_TRACE_FENTRY]		= "fentry",
-	[BPF_TRACE_FEXIT]		= "fexit",
-	[BPF_MODIFY_RETURN]		= "mod_ret",
-	[BPF_LSM_MAC]			= "lsm_mac",
-	[BPF_SK_LOOKUP]			= "sk_lookup",
-};
-
 void p_err(const char *fmt, ...)
 {
 	va_list ap;
@@ -99,7 +68,7 @@ void p_info(const char *fmt, ...)
 	va_end(ap);
 }
 
-static bool is_bpffs(char *path)
+static bool is_bpffs(const char *path)
 {
 	struct statfs st_fs;
 
@@ -109,11 +78,73 @@ static bool is_bpffs(char *path)
 	return (unsigned long)st_fs.f_type == BPF_FS_MAGIC;
 }
 
+/* Probe whether kernel switched from memlock-based (RLIMIT_MEMLOCK) to
+ * memcg-based memory accounting for BPF maps and programs. This was done in
+ * commit 97306be45fbe ("Merge branch 'switch to memcg-based memory
+ * accounting'"), in Linux 5.11.
+ *
+ * Libbpf also offers to probe for memcg-based accounting vs rlimit, but does
+ * so by checking for the availability of a given BPF helper and this has
+ * failed on some kernels with backports in the past, see commit 6b4384ff1088
+ * ("Revert "bpftool: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK"").
+ * Instead, we can probe by lowering the process-based rlimit to 0, trying to
+ * load a BPF object, and resetting the rlimit. If the load succeeds then
+ * memcg-based accounting is supported.
+ *
+ * This would be too dangerous to do in the library, because multithreaded
+ * applications might attempt to load items while the rlimit is at 0. Given
+ * that bpftool is single-threaded, this is fine to do here.
+ */
+static bool known_to_need_rlimit(void)
+{
+	struct rlimit rlim_init, rlim_cur_zero = {};
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	size_t insn_cnt = ARRAY_SIZE(insns);
+	union bpf_attr attr;
+	int prog_fd, err;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	attr.insns = ptr_to_u64(insns);
+	attr.insn_cnt = insn_cnt;
+	attr.license = ptr_to_u64("GPL");
+
+	if (getrlimit(RLIMIT_MEMLOCK, &rlim_init))
+		return false;
+
+	/* Drop the soft limit to zero. We maintain the hard limit to its
+	 * current value, because lowering it would be a permanent operation
+	 * for unprivileged users.
+	 */
+	rlim_cur_zero.rlim_max = rlim_init.rlim_max;
+	if (setrlimit(RLIMIT_MEMLOCK, &rlim_cur_zero))
+		return false;
+
+	/* Do not use bpf_prog_load() from libbpf here, because it calls
+	 * bump_rlimit_memlock(), interfering with the current probe.
+	 */
+	prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
+	err = errno;
+
+	/* reset soft rlimit to its initial value */
+	setrlimit(RLIMIT_MEMLOCK, &rlim_init);
+
+	if (prog_fd < 0)
+		return err == EPERM;
+
+	close(prog_fd);
+	return false;
+}
+
 void set_max_rlimit(void)
 {
 	struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
 
-	setrlimit(RLIMIT_MEMLOCK, &rinf);
+	if (known_to_need_rlimit())
+		setrlimit(RLIMIT_MEMLOCK, &rinf);
 }
 
 static int
@@ -213,21 +244,101 @@ int open_obj_pinned_any(const char *path, enum bpf_obj_type exp_type)
 	return fd;
 }
 
-int mount_bpffs_for_pin(const char *name)
+int create_and_mount_bpffs_dir(const char *dir_name)
+{
+	char err_str[ERR_MAX_LEN];
+	bool dir_exists;
+	int err = 0;
+
+	if (is_bpffs(dir_name))
+		return err;
+
+	dir_exists = access(dir_name, F_OK) == 0;
+
+	if (!dir_exists) {
+		char *temp_name;
+		char *parent_name;
+
+		temp_name = strdup(dir_name);
+		if (!temp_name) {
+			p_err("mem alloc failed");
+			return -1;
+		}
+
+		parent_name = dirname(temp_name);
+
+		if (is_bpffs(parent_name)) {
+			/* nothing to do if already mounted */
+			free(temp_name);
+			return err;
+		}
+
+		if (access(parent_name, F_OK) == -1) {
+			p_err("can't create dir '%s' to pin BPF object: parent dir '%s' doesn't exist",
+			      dir_name, parent_name);
+			free(temp_name);
+			return -1;
+		}
+
+		free(temp_name);
+	}
+
+	if (block_mount) {
+		p_err("no BPF file system found, not mounting it due to --nomount option");
+		return -1;
+	}
+
+	if (!dir_exists) {
+		err = mkdir(dir_name, S_IRWXU);
+		if (err) {
+			p_err("failed to create dir '%s': %s", dir_name, strerror(errno));
+			return err;
+		}
+	}
+
+	err = mnt_fs(dir_name, "bpf", err_str, ERR_MAX_LEN);
+	if (err) {
+		err_str[ERR_MAX_LEN - 1] = '\0';
+		p_err("can't mount BPF file system on given dir '%s': %s",
+		      dir_name, err_str);
+
+		if (!dir_exists)
+			rmdir(dir_name);
+	}
+
+	return err;
+}
+
+int mount_bpffs_for_file(const char *file_name)
 {
 	char err_str[ERR_MAX_LEN];
-	char *file;
+	char *temp_name;
 	char *dir;
 	int err = 0;
 
-	file = malloc(strlen(name) + 1);
-	strcpy(file, name);
-	dir = dirname(file);
+	if (access(file_name, F_OK) != -1) {
+		p_err("can't pin BPF object: path '%s' already exists", file_name);
+		return -1;
+	}
+
+	temp_name = strdup(file_name);
+	if (!temp_name) {
+		p_err("mem alloc failed");
+		return -1;
+	}
+
+	dir = dirname(temp_name);
 
 	if (is_bpffs(dir))
 		/* nothing to do if already mounted */
 		goto out_free;
 
+	if (access(dir, F_OK) == -1) {
+		p_err("can't pin BPF object: dir '%s' doesn't exist", dir);
+		err = -1;
+		goto out_free;
+	}
+
 	if (block_mount) {
 		p_err("no BPF file system found, not mounting it due to --nomount option");
 		err = -1;
@@ -237,12 +348,12 @@ int mount_bpffs_for_pin(const char *name)
 	err = mnt_fs(dir, "bpf", err_str, ERR_MAX_LEN);
 	if (err) {
 		err_str[ERR_MAX_LEN - 1] = '\0';
-		p_err("can't mount BPF file system to pin the object (%s): %s",
-		      name, err_str);
+		p_err("can't mount BPF file system to pin the object '%s': %s",
+		      file_name, err_str);
 	}
 
 out_free:
-	free(file);
+	free(temp_name);
 	return err;
 }
 
@@ -250,7 +361,7 @@ int do_pin_fd(int fd, const char *name)
 {
 	int err;
 
-	err = mount_bpffs_for_pin(name);
+	err = mount_bpffs_for_file(name);
 	if (err)
 		return err;
 
@@ -266,6 +377,9 @@ int do_pin_any(int argc, char **argv, int (*get_fd)(int *, char ***))
 	int err;
 	int fd;
 
+	if (!REQ_ARGS(3))
+		return -EINVAL;
+
 	fd = get_fd(&argc, &argv);
 	if (fd < 0)
 		return fd;
@@ -282,6 +396,7 @@ const char *get_fd_type_name(enum bpf_obj_type type)
 		[BPF_OBJ_UNKNOWN]	= "unknown",
 		[BPF_OBJ_PROG]		= "prog",
 		[BPF_OBJ_MAP]		= "map",
+		[BPF_OBJ_LINK]		= "link",
 	};
 
 	if (type < 0 || type >= ARRAY_SIZE(names) || !names[type])
@@ -290,6 +405,49 @@ const char *get_fd_type_name(enum bpf_obj_type type)
 	return names[type];
 }
 
+void get_prog_full_name(const struct bpf_prog_info *prog_info, int prog_fd,
+			char *name_buff, size_t buff_len)
+{
+	const char *prog_name = prog_info->name;
+	const struct btf_type *func_type;
+	const struct bpf_func_info finfo = {};
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
+	struct btf *prog_btf = NULL;
+
+	if (buff_len <= BPF_OBJ_NAME_LEN ||
+	    strlen(prog_info->name) < BPF_OBJ_NAME_LEN - 1)
+		goto copy_name;
+
+	if (!prog_info->btf_id || prog_info->nr_func_info == 0)
+		goto copy_name;
+
+	info.nr_func_info = 1;
+	info.func_info_rec_size = prog_info->func_info_rec_size;
+	if (info.func_info_rec_size > sizeof(finfo))
+		info.func_info_rec_size = sizeof(finfo);
+	info.func_info = ptr_to_u64(&finfo);
+
+	if (bpf_prog_get_info_by_fd(prog_fd, &info, &info_len))
+		goto copy_name;
+
+	prog_btf = btf__load_from_kernel_by_id(info.btf_id);
+	if (!prog_btf)
+		goto copy_name;
+
+	func_type = btf__type_by_id(prog_btf, finfo.type_id);
+	if (!func_type || !btf_is_func(func_type))
+		goto copy_name;
+
+	prog_name = btf__name_by_offset(prog_btf, func_type->name_off);
+
+copy_name:
+	snprintf(name_buff, buff_len, "%s", prog_name);
+
+	if (prog_btf)
+		btf__free(prog_btf);
+}
+
 int get_fd_type(int fd)
 {
 	char path[PATH_MAX];
@@ -381,7 +539,7 @@ void print_hex_data_json(uint8_t *data, size_t len)
 }
 
 /* extra params for nftw cb */
-static struct pinned_obj_table *build_fn_table;
+static struct hashmap *build_fn_table;
 static enum bpf_obj_type build_fn_type;
 
 static int do_build_table_cb(const char *fpath, const struct stat *sb,
@@ -389,9 +547,9 @@ static int do_build_table_cb(const char *fpath, const struct stat *sb,
 {
 	struct bpf_prog_info pinned_info;
 	__u32 len = sizeof(pinned_info);
-	struct pinned_obj *obj_node;
 	enum bpf_obj_type objtype;
 	int fd, err = 0;
+	char *path;
 
 	if (typeflag != FTW_F)
 		goto out_ret;
@@ -405,31 +563,30 @@ static int do_build_table_cb(const char *fpath, const struct stat *sb,
 		goto out_close;
 
 	memset(&pinned_info, 0, sizeof(pinned_info));
-	if (bpf_obj_get_info_by_fd(fd, &pinned_info, &len))
+	if (bpf_prog_get_info_by_fd(fd, &pinned_info, &len))
 		goto out_close;
 
-	obj_node = calloc(1, sizeof(*obj_node));
-	if (!obj_node) {
+	path = strdup(fpath);
+	if (!path) {
 		err = -1;
 		goto out_close;
 	}
 
-	obj_node->id = pinned_info.id;
-	obj_node->path = strdup(fpath);
-	if (!obj_node->path) {
-		err = -1;
-		free(obj_node);
+	err = hashmap__append(build_fn_table, pinned_info.id, path);
+	if (err) {
+		p_err("failed to append entry to hashmap for ID %u, path '%s': %s",
+		      pinned_info.id, path, strerror(errno));
+		free(path);
 		goto out_close;
 	}
 
-	hash_add(build_fn_table->table, &obj_node->hash, obj_node->id);
 out_close:
 	close(fd);
 out_ret:
 	return err;
 }
 
-int build_pinned_obj_table(struct pinned_obj_table *tab,
+int build_pinned_obj_table(struct hashmap *tab,
 			   enum bpf_obj_type type)
 {
 	struct mntent *mntent = NULL;
@@ -458,17 +615,18 @@ int build_pinned_obj_table(struct pinned_obj_table *tab,
 	return err;
 }
 
-void delete_pinned_obj_table(struct pinned_obj_table *tab)
+void delete_pinned_obj_table(struct hashmap *map)
 {
-	struct pinned_obj *obj;
-	struct hlist_node *tmp;
-	unsigned int bkt;
+	struct hashmap_entry *entry;
+	size_t bkt;
 
-	hash_for_each_safe(tab->table, bkt, tmp, obj, hash) {
-		hash_del(&obj->hash);
-		free(obj->path);
-		free(obj);
-	}
+	if (!map)
+		return;
+
+	hashmap__for_each_entry(map, entry, bkt)
+		free(entry->pvalue);
+
+	hashmap__free(map);
 }
 
 unsigned int get_page_size(void)
@@ -548,12 +706,11 @@ static int read_sysfs_netdev_hex_int(char *devname, const char *entry_name)
 }
 
 const char *
-ifindex_to_bfd_params(__u32 ifindex, __u64 ns_dev, __u64 ns_ino,
-		      const char **opt)
+ifindex_to_arch(__u32 ifindex, __u64 ns_dev, __u64 ns_ino, const char **opt)
 {
+	__maybe_unused int device_id;
 	char devname[IF_NAMESIZE];
 	int vendor_id;
-	int device_id;
 
 	if (!ifindex_to_name_ns(ifindex, ns_dev, ns_ino, devname)) {
 		p_err("Can't get net device name for ifindex %d: %s", ifindex,
@@ -568,6 +725,7 @@ ifindex_to_bfd_params(__u32 ifindex, __u64 ns_dev, __u64 ns_ino,
 	}
 
 	switch (vendor_id) {
+#ifdef HAVE_LIBBFD_SUPPORT
 	case 0x19ee:
 		device_id = read_sysfs_netdev_hex_int(devname, "device");
 		if (device_id != 0x4000 &&
@@ -576,8 +734,10 @@ ifindex_to_bfd_params(__u32 ifindex, __u64 ns_dev, __u64 ns_ino,
 			p_info("Unknown NFP device ID, assuming it is NFP-6xxx arch");
 		*opt = "ctx4";
 		return "NFP-6xxx";
+#endif /* HAVE_LIBBFD_SUPPORT */
+	/* No NFP support in LLVM, we have no valid triple to return. */
 	default:
-		p_err("Can't get bfd arch name for device vendor id 0x%04x",
+		p_err("Can't get arch name for device vendor id 0x%04x",
 		      vendor_id);
 		return NULL;
 	}
@@ -645,6 +805,7 @@ print_all_levels(__maybe_unused enum libbpf_print_level level,
 
 static int prog_fd_by_nametag(void *nametag, int **fds, bool tag)
 {
+	char prog_name[MAX_PROG_FULL_NAME];
 	unsigned int id = 0;
 	int fd, nb_fds = 0;
 	void *tmp;
@@ -670,19 +831,27 @@ static int prog_fd_by_nametag(void *nametag, int **fds, bool tag)
 			goto err_close_fds;
 		}
 
-		err = bpf_obj_get_info_by_fd(fd, &info, &len);
+		err = bpf_prog_get_info_by_fd(fd, &info, &len);
 		if (err) {
 			p_err("can't get prog info (%u): %s",
 			      id, strerror(errno));
 			goto err_close_fd;
 		}
 
-		if ((tag && memcmp(nametag, info.tag, BPF_TAG_SIZE)) ||
-		    (!tag && strncmp(nametag, info.name, BPF_OBJ_NAME_LEN))) {
+		if (tag && memcmp(nametag, info.tag, BPF_TAG_SIZE)) {
 			close(fd);
 			continue;
 		}
 
+		if (!tag) {
+			get_prog_full_name(&info, fd, prog_name,
+					   sizeof(prog_name));
+			if (strncmp(nametag, prog_name, sizeof(prog_name))) {
+				close(fd);
+				continue;
+			}
+		}
+
 		if (nb_fds > 0) {
 			tmp = realloc(*fds, (nb_fds + 1) * sizeof(int));
 			if (!tmp) {
@@ -743,7 +912,7 @@ int prog_parse_fds(int *argc, char ***argv, int **fds)
 		NEXT_ARGP();
 
 		name = **argv;
-		if (strlen(name) > BPF_OBJ_NAME_LEN - 1) {
+		if (strlen(name) > MAX_PROG_FULL_NAME - 1) {
 			p_err("can't parse name");
 			return -1;
 		}
@@ -822,7 +991,7 @@ static int map_fd_by_name(char *name, int **fds)
 			goto err_close_fds;
 		}
 
-		err = bpf_obj_get_info_by_fd(fd, &info, &len);
+		err = bpf_map_get_info_by_fd(fd, &info, &len);
 		if (err) {
 			p_err("can't get map info (%u): %s",
 			      id, strerror(errno));
@@ -932,7 +1101,8 @@ exit_free:
 	return fd;
 }
 
-int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
+int map_parse_fd_and_info(int *argc, char ***argv, struct bpf_map_info *info,
+			  __u32 *info_len)
 {
 	int err;
 	int fd;
@@ -941,7 +1111,7 @@ int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
 	if (fd < 0)
 		return -1;
 
-	err = bpf_obj_get_info_by_fd(fd, info, info_len);
+	err = bpf_map_get_info_by_fd(fd, info, info_len);
 	if (err) {
 		p_err("can't get map info: %s", strerror(errno));
 		close(fd);
@@ -950,3 +1120,63 @@ int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len)
 
 	return fd;
 }
+
+size_t hash_fn_for_key_as_id(long key, void *ctx)
+{
+	return key;
+}
+
+bool equal_fn_for_key_as_id(long k1, long k2, void *ctx)
+{
+	return k1 == k2;
+}
+
+const char *bpf_attach_type_input_str(enum bpf_attach_type t)
+{
+	switch (t) {
+	case BPF_CGROUP_INET_INGRESS:		return "ingress";
+	case BPF_CGROUP_INET_EGRESS:		return "egress";
+	case BPF_CGROUP_INET_SOCK_CREATE:	return "sock_create";
+	case BPF_CGROUP_INET_SOCK_RELEASE:	return "sock_release";
+	case BPF_CGROUP_SOCK_OPS:		return "sock_ops";
+	case BPF_CGROUP_DEVICE:			return "device";
+	case BPF_CGROUP_INET4_BIND:		return "bind4";
+	case BPF_CGROUP_INET6_BIND:		return "bind6";
+	case BPF_CGROUP_INET4_CONNECT:		return "connect4";
+	case BPF_CGROUP_INET6_CONNECT:		return "connect6";
+	case BPF_CGROUP_INET4_POST_BIND:	return "post_bind4";
+	case BPF_CGROUP_INET6_POST_BIND:	return "post_bind6";
+	case BPF_CGROUP_INET4_GETPEERNAME:	return "getpeername4";
+	case BPF_CGROUP_INET6_GETPEERNAME:	return "getpeername6";
+	case BPF_CGROUP_INET4_GETSOCKNAME:	return "getsockname4";
+	case BPF_CGROUP_INET6_GETSOCKNAME:	return "getsockname6";
+	case BPF_CGROUP_UDP4_SENDMSG:		return "sendmsg4";
+	case BPF_CGROUP_UDP6_SENDMSG:		return "sendmsg6";
+	case BPF_CGROUP_SYSCTL:			return "sysctl";
+	case BPF_CGROUP_UDP4_RECVMSG:		return "recvmsg4";
+	case BPF_CGROUP_UDP6_RECVMSG:		return "recvmsg6";
+	case BPF_CGROUP_GETSOCKOPT:		return "getsockopt";
+	case BPF_CGROUP_SETSOCKOPT:		return "setsockopt";
+	case BPF_TRACE_RAW_TP:			return "raw_tp";
+	case BPF_TRACE_FENTRY:			return "fentry";
+	case BPF_TRACE_FEXIT:			return "fexit";
+	case BPF_MODIFY_RETURN:			return "mod_ret";
+	case BPF_SK_REUSEPORT_SELECT:		return "sk_skb_reuseport_select";
+	case BPF_SK_REUSEPORT_SELECT_OR_MIGRATE:	return "sk_skb_reuseport_select_or_migrate";
+	default:	return libbpf_bpf_attach_type_str(t);
+	}
+}
+
+int pathname_concat(char *buf, int buf_sz, const char *path,
+		    const char *name)
+{
+	int len;
+
+	len = snprintf(buf, buf_sz, "%s/%s", path, name);
+	if (len < 0)
+		return -EINVAL;
+	if (len >= buf_sz)
+		return -ENAMETOOLONG;
+
+	return 0;
+}