Date:	Fri, 16 Oct 2015 03:09:24 +0200
From:	Daniel Borkmann <daniel@...earbox.net>
To:	davem@...emloft.net
Cc:	ast@...mgrid.com, viro@...IV.linux.org.uk, ebiederm@...ssion.com,
	tgraf@...g.ch, hannes@...essinduktion.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>,
	Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH net-next 3/4] bpf: add support for persistent maps/progs

This work adds support for "persistent" eBPF maps/programs. The term
"persistent" is to be understood that maps/programs have a facility
that lets them survive process termination. This is desired by various
eBPF subsystem users.

Just to name one example: tc classifier/action. Whenever tc parses
the ELF object, extracts and loads maps/progs into the kernel, these
file descriptors will be out of reach after the tc instance exits.
So a subsequent tc invocation won't be able to access/relocate on this
resource, and therefore maps cannot easily be shared, f.e. between the
ingress and egress networking data path.

The current workaround is that Unix domain sockets (UDS) need to be
instrumented in order to pass the created eBPF map/program file
descriptors to a third party management daemon through UDS' socket
passing facility. This makes it a bit complicated to deploy shared
eBPF maps or programs (programs f.e. for tail calls) among various
processes.

We've been brainstorming on how we could tackle this issue and various
approches have been tried out so far:

The first idea was to implement a fuse backend that proxies bpf(2)
syscalls that create/load maps and programs, where the fuse
implementation would hold these fds internally and pass them to
things like tc via UDS socket passing. There could be various fuse
implementations tailored to a particular eBPF subsystem's needs. The
advantage is that this would shift the complexity entirely into user
space, but with a couple of drawbacks along the way. One being that
fuse needs extra library dependencies and it also doesn't resolve the
issue that an extra daemon needs to run in the background. At Linux
Plumbers 2015, we've all concluded eventually that using fuse is not
an option and an in-kernel solution is needed.

The next idea I've tried out was an extension to the bpf(2) syscall
that works roughly in a way we bind(2)/connect(2) to paths backed
by special inodes in case of UDS. This works on top of any file system
that allows to create special files, where the newly created inode
operations are similar to those of S_IFSOCK inodes. The inode would
be instrumented as a lookup key in an rhashtable backend with the
prog/map stored as value. We found that there are a couple of
disadvantages on this approach. Since the underlying implementation
of the inode can differ among file systems, we need a periodic garbage
collection for dropping the rhashtable entry and the references to
the maps/progs held with it (it could be done by piggybacking into
the rhashtable's rehashing, though). The other issue is that this
requires to add something like S_IFBPF (to clearly identify this inode
as special to eBPF), where the available space in the S_IFMT is already
severly limited and could possibly clash with future POSIX values being
allocated there. Moreover, this approach might not be flexible enough
from a functionality point of view, f.e. things like future debugging
facilities, etc could be added that really wouldn't fit into bpf(2)
syscall (however, the bpf(2) syscall strictly stays the central place
to manage eBPF things).

This eventually leads us to this patch, which implements a minimal
eBPF file system. The idea is a bit similar, but to the point that
these inodes reside at one or multiple mount points. A directory
hierarchy can be tailored to a specific application use-case from the
various subsystem users and maps/progs pinned inside it. Two new eBPF
commands (BPF_PIN_FD, BPF_NEW_FD) have been added to the syscall in
order to create one or multiple special inodes from an existing file
descriptor that points to a map/program (we call it eBPF fd pinning),
or to create a new file descriptor from an existing special inode.
BPF_PIN_FD requires CAP_SYS_ADMIN capabilities, whereas BPF_NEW_FD
can also be done unpriviledged when having appropriate permissions
to the path.

The next step I'm working on is to add dump eBPF map/prog commands
to bpf(2), so that a specification from a given file descriptor can
be retrieved. This can be used by things like CRIU but also applications
can inspect the meta data after calling BPF_NEW_FD.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 include/linux/bpf.h        |  21 ++
 include/uapi/linux/bpf.h   |  45 +---
 include/uapi/linux/magic.h |   1 +
 include/uapi/linux/xattr.h |   3 +
 kernel/bpf/Makefile        |   4 +-
 kernel/bpf/inode.c         | 614 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c       | 108 ++++++++
 7 files changed, 758 insertions(+), 38 deletions(-)
 create mode 100644 kernel/bpf/inode.c

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0ae6f77..bb82764 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -8,8 +8,10 @@
 #define _LINUX_BPF_H 1
 
 #include <uapi/linux/bpf.h>
+
 #include <linux/workqueue.h>
 #include <linux/file.h>
+#include <linux/fs.h>
 
 struct bpf_map;
 
@@ -137,6 +139,17 @@ struct bpf_prog_aux {
 	};
 };
 
+enum bpf_fd_type {
+	BPF_FD_TYPE_PROG,
+	BPF_FD_TYPE_MAP,
+};
+
+union bpf_any {
+	struct bpf_map *map;
+	struct bpf_prog *prog;
+	void *raw_ptr;
+};
+
 struct bpf_array {
 	struct bpf_map map;
 	u32 elem_size;
@@ -172,6 +185,14 @@ void bpf_map_put(struct bpf_map *map);
 
 extern int sysctl_unprivileged_bpf_disabled;
 
+void bpf_any_get(union bpf_any raw, enum bpf_fd_type type);
+void bpf_any_put(union bpf_any raw, enum bpf_fd_type type);
+
+int bpf_fd_inode_add(const struct filename *pathname,
+		     union bpf_any raw, enum bpf_fd_type type);
+union bpf_any bpf_fd_inode_get(const struct filename *pathname,
+			       enum bpf_fd_type *type);
+
 /* verify correctness of eBPF program */
 int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
 #else
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 564f1f0..f9b412c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -63,50 +63,16 @@ struct bpf_insn {
 	__s32	imm;		/* signed immediate constant */
 };
 
-/* BPF syscall commands */
+/* BPF syscall commands, see bpf(2) man-page for details. */
 enum bpf_cmd {
-	/* create a map with given type and attributes
-	 * fd = bpf(BPF_MAP_CREATE, union bpf_attr *, u32 size)
-	 * returns fd or negative error
-	 * map is deleted when fd is closed
-	 */
 	BPF_MAP_CREATE,
-
-	/* lookup key in a given map
-	 * err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
-	 * Using attr->map_fd, attr->key, attr->value
-	 * returns zero and stores found elem into value
-	 * or negative error
-	 */
 	BPF_MAP_LOOKUP_ELEM,
-
-	/* create or update key/value pair in a given map
-	 * err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
-	 * Using attr->map_fd, attr->key, attr->value, attr->flags
-	 * returns zero or negative error
-	 */
 	BPF_MAP_UPDATE_ELEM,
-
-	/* find and delete elem by key in a given map
-	 * err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
-	 * Using attr->map_fd, attr->key
-	 * returns zero or negative error
-	 */
 	BPF_MAP_DELETE_ELEM,
-
-	/* lookup key in a given map and return next key
-	 * err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
-	 * Using attr->map_fd, attr->key, attr->next_key
-	 * returns zero and stores next key or negative error
-	 */
 	BPF_MAP_GET_NEXT_KEY,
-
-	/* verify and load eBPF program
-	 * prog_fd = bpf(BPF_PROG_LOAD, union bpf_attr *attr, u32 size)
-	 * Using attr->prog_type, attr->insns, attr->license
-	 * returns fd or negative error
-	 */
 	BPF_PROG_LOAD,
+	BPF_PIN_FD,
+	BPF_NEW_FD,
 };
 
 enum bpf_map_type {
@@ -160,6 +126,11 @@ union bpf_attr {
 		__aligned_u64	log_buf;	/* user supplied buffer */
 		__u32		kern_version;	/* checked when prog_type=kprobe */
 	};
+
+	struct { /* anonymous struct used by BPF_{PIN,NEW}_FD command */
+		__u32		fd;
+		__aligned_u64	pathname;
+	};
 } __attribute__((aligned(8)));
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 7b1425a..c1c5cf7 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -75,5 +75,6 @@
 #define ANON_INODE_FS_MAGIC	0x09041934
 #define BTRFS_TEST_MAGIC	0x73727279
 #define NSFS_MAGIC		0x6e736673
+#define BPFFS_MAGIC		0xcafe4a11
 
 #endif /* __LINUX_MAGIC_H__ */
diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h
index 1590c49..3586d28 100644
--- a/include/uapi/linux/xattr.h
+++ b/include/uapi/linux/xattr.h
@@ -42,6 +42,9 @@
 #define XATTR_USER_PREFIX "user."
 #define XATTR_USER_PREFIX_LEN (sizeof(XATTR_USER_PREFIX) - 1)
 
+#define XATTR_BPF_PREFIX "bpf."
+#define XATTR_BPF_PREFIX_LEN (sizeof(XATTR_BPF_PREFIX) - 1)
+
 /* Security namespace */
 #define XATTR_EVM_SUFFIX "evm"
 #define XATTR_NAME_EVM XATTR_SECURITY_PREFIX XATTR_EVM_SUFFIX
diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index e6983be..1327258 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -1,2 +1,4 @@
 obj-y := core.o
-obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o helpers.o
+
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o
+obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
new file mode 100644
index 0000000..5cef673
--- /dev/null
+++ b/kernel/bpf/inode.c
@@ -0,0 +1,614 @@
+/*
+ * Minimal file system backend for special inodes holding eBPF maps and
+ * programs, used by eBPF fd pinning.
+ *
+ * (C) 2015 Daniel Borkmann <daniel@...earbox.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/parser.h>
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/seq_file.h>
+#include <linux/fsnotify.h>
+#include <linux/filter.h>
+#include <linux/bpf.h>
+#include <linux/security.h>
+#include <linux/xattr.h>
+
+#define BPFFS_DEFAULT_MODE 0700
+
+enum {
+	BPF_OPT_UID,
+	BPF_OPT_GID,
+	BPF_OPT_MODE,
+	BPF_OPT_ERR,
+};
+
+struct bpf_mnt_opts {
+	kuid_t uid;
+	kgid_t gid;
+	umode_t mode;
+};
+
+struct bpf_fs_info {
+	struct bpf_mnt_opts mnt_opts;
+};
+
+struct bpf_dir_state {
+	unsigned long flags;
+};
+
+static const match_table_t bpf_tokens = {
+	{ BPF_OPT_UID, "uid=%u" },
+	{ BPF_OPT_GID, "gid=%u" },
+	{ BPF_OPT_MODE, "mode=%o" },
+	{ BPF_OPT_ERR, NULL },
+};
+
+static const struct inode_operations bpf_dir_iops;
+static const struct inode_operations bpf_prog_iops;
+static const struct inode_operations bpf_map_iops;
+
+static struct inode *bpf_get_inode(struct super_block *sb,
+				   const struct inode *dir,
+				   umode_t mode)
+{
+	struct inode *inode = new_inode(sb);
+
+	if (!inode)
+		return ERR_PTR(-ENOSPC);
+
+	inode->i_ino = get_next_ino();
+	inode->i_atime = CURRENT_TIME;
+	inode->i_mtime = inode->i_atime;
+	inode->i_ctime = inode->i_atime;
+	inode_init_owner(inode, dir, mode);
+
+	return inode;
+}
+
+static struct inode *bpf_mknod(struct inode *dir, umode_t mode)
+{
+	return bpf_get_inode(dir->i_sb, dir, mode);
+}
+
+static bool bpf_dentry_name_reserved(const struct dentry *dentry)
+{
+	return strchr(dentry->d_name.name, '.');
+}
+
+enum {
+	/* Directory state is 'terminating', so no subdirectories
+	 * are allowed anymore in this directory. This is being
+	 * reserved so that in future, auto-generated directories
+	 * could be added along with the special map/prog inodes.
+	 */
+	BPF_DSTATE_TERM_BIT,
+};
+
+static bool bpf_inode_is_term(struct inode *dir)
+{
+	struct bpf_dir_state *state = dir->i_private;
+
+	return test_bit(BPF_DSTATE_TERM_BIT, &state->flags);
+}
+
+static bool bpf_inode_make_term(struct inode *dir)
+{
+	struct bpf_dir_state *state = dir->i_private;
+
+	return dir->i_nlink != 2 ||
+	       test_and_set_bit(BPF_DSTATE_TERM_BIT, &state->flags);
+}
+
+static void bpf_inode_undo_term(struct inode *dir)
+{
+	struct bpf_dir_state *state = dir->i_private;
+
+	clear_bit(BPF_DSTATE_TERM_BIT, &state->flags);
+}
+
+static int bpf_inode_type(const struct inode *inode, enum bpf_fd_type *i_type)
+{
+	if (inode->i_op == &bpf_prog_iops)
+		*i_type = BPF_FD_TYPE_PROG;
+	else if (inode->i_op == &bpf_map_iops)
+		*i_type = BPF_FD_TYPE_MAP;
+	else
+		return -EACCES;
+
+	return 0;
+}
+
+static int bpf_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	void *i_private = inode->i_private;
+	enum bpf_fd_type type;
+	bool is_fd, drop_ref;
+	int ret;
+
+	is_fd = bpf_inode_type(inode, &type) == 0;
+	drop_ref = inode->i_nlink == 1;
+
+	ret = simple_unlink(dir, dentry);
+	if (!ret && is_fd && drop_ref) {
+		union bpf_any raw;
+
+		raw.raw_ptr = i_private;
+		bpf_any_put(raw, type);
+		bpf_inode_undo_term(dir);
+	}
+
+	return ret;
+}
+
+static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	struct bpf_dir_state *state;
+	struct inode *inode;
+
+	if (bpf_inode_is_term(dir))
+		return -EPERM;
+	if (bpf_dentry_name_reserved(dentry))
+		return -EPERM;
+
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOSPC;
+
+	inode = bpf_mknod(dir, dir->i_mode);
+	if (IS_ERR(inode)) {
+		kfree(state);
+		return PTR_ERR(inode);
+	}
+
+	inode->i_private = state;
+	inode->i_op = &bpf_dir_iops;
+	inode->i_fop = &simple_dir_operations;
+
+	inc_nlink(inode);
+	inc_nlink(dir);
+
+	d_instantiate(dentry, inode);
+	dget(dentry);
+
+	return 0;
+}
+
+static int bpf_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	void *i_private = inode->i_private;
+	int ret;
+
+	ret = simple_rmdir(dir, dentry);
+	if (!ret)
+		kfree(i_private);
+
+	return ret;
+}
+
+static const struct inode_operations bpf_dir_iops = {
+	.lookup		= simple_lookup,
+	.mkdir		= bpf_mkdir,
+	.rmdir		= bpf_rmdir,
+	.unlink		= bpf_unlink,
+};
+
+#define XATTR_TYPE_SUFFIX "type"
+
+#define XATTR_NAME_BPF_TYPE (XATTR_BPF_PREFIX XATTR_TYPE_SUFFIX)
+#define XATTR_NAME_BPF_TYPE_LEN (sizeof(XATTR_NAME_BPF_TYPE) - 1)
+
+#define XATTR_VALUE_MAP "map"
+#define XATTR_VALUE_PROG "prog"
+
+static ssize_t bpf_getxattr(struct dentry *dentry, const char *name,
+			    void *buffer, size_t size)
+{
+	enum bpf_fd_type type;
+	ssize_t ret;
+
+	if (strncmp(name, XATTR_NAME_BPF_TYPE, XATTR_NAME_BPF_TYPE_LEN))
+		return -ENODATA;
+
+	if (bpf_inode_type(d_inode(dentry), &type))
+		return -ENODATA;
+
+	switch (type) {
+	case BPF_FD_TYPE_PROG:
+		ret = sizeof(XATTR_VALUE_PROG);
+		break;
+	case BPF_FD_TYPE_MAP:
+		ret = sizeof(XATTR_VALUE_MAP);
+		break;
+	}
+
+	if (buffer) {
+		if (size < ret)
+			return -ERANGE;
+
+		switch (type) {
+		case BPF_FD_TYPE_PROG:
+			strncpy(buffer, XATTR_VALUE_PROG, ret);
+			break;
+		case BPF_FD_TYPE_MAP:
+			strncpy(buffer, XATTR_VALUE_MAP, ret);
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static ssize_t bpf_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+	ssize_t len, used = 0;
+
+	len = security_inode_listsecurity(d_inode(dentry), buffer, size);
+	if (len < 0)
+		return len;
+
+	used += len;
+	if (buffer) {
+		if (size < used)
+			return -ERANGE;
+
+		buffer += len;
+	}
+
+	len = XATTR_NAME_BPF_TYPE_LEN + 1;
+	used += len;
+	if (buffer) {
+		if (size < used)
+			return -ERANGE;
+
+		memcpy(buffer, XATTR_NAME_BPF_TYPE, len);
+		buffer += len;
+	}
+
+	return used;
+}
+
+/* Special inodes handling map/progs currently don't allow for syscalls
+ * such as open/read/write/etc. We use the same bpf_{map,prog}_new_fd()
+ * facility for installing an fd to the user as we do on BPF_MAP_CREATE
+ * and BPF_PROG_LOAD, so an applications using bpf(2) don't see any
+ * change in behaviour. In future, the set of open/read/write/etc could
+ * be used f.e. for implementing things like debugging facilities on the
+ * underlying map/prog that would work with non-bpf(2) aware tooling.
+ */
+static const struct inode_operations bpf_prog_iops = {
+	.getxattr	= bpf_getxattr,
+	.listxattr	= bpf_listxattr,
+};
+
+static const struct inode_operations bpf_map_iops = {
+	.getxattr	= bpf_getxattr,
+	.listxattr	= bpf_listxattr,
+};
+
+static int bpf_mkmap(struct inode *dir, struct dentry *dentry,
+		     struct bpf_map *map, umode_t i_mode)
+{
+	struct inode *inode;
+
+	if (bpf_dentry_name_reserved(dentry))
+		return -EPERM;
+	if (bpf_inode_make_term(dir))
+		return -EBUSY;
+
+	inode = bpf_mknod(dir, i_mode);
+	if (IS_ERR(inode)) {
+		bpf_inode_undo_term(dir);
+		return PTR_ERR(inode);
+	}
+
+	inode->i_private = map;
+	inode->i_op = &bpf_map_iops;
+
+	d_instantiate(dentry, inode);
+	dget(dentry);
+
+	return 0;
+}
+
+static int bpf_mkprog(struct inode *dir, struct dentry *dentry,
+		      struct bpf_prog *prog, umode_t i_mode)
+{
+	struct inode *inode;
+
+	if (bpf_dentry_name_reserved(dentry))
+		return -EPERM;
+	if (bpf_inode_make_term(dir))
+		return -EBUSY;
+
+	inode = bpf_mknod(dir, i_mode);
+	if (IS_ERR(inode)) {
+		bpf_inode_undo_term(dir);
+		return PTR_ERR(inode);
+	}
+
+	inode->i_private = prog;
+	inode->i_op = &bpf_prog_iops;
+
+	d_instantiate(dentry, inode);
+	dget(dentry);
+
+	return 0;
+}
+
+static const struct bpf_mnt_opts *bpf_sb_mnt_opts(const struct super_block *sb)
+{
+	const struct bpf_fs_info *bfi = sb->s_fs_info;
+
+	return &bfi->mnt_opts;
+}
+
+static int bpf_parse_options(char *opt_data, struct bpf_mnt_opts *opts)
+{
+	substring_t args[MAX_OPT_ARGS];
+	unsigned int opt_val, token;
+	char *opt_ptr;
+	kuid_t uid;
+	kgid_t gid;
+
+	opts->mode = BPFFS_DEFAULT_MODE;
+
+	while ((opt_ptr = strsep(&opt_data, ",")) != NULL) {
+		if (!*opt_ptr)
+			continue;
+
+		token = match_token(opt_ptr, bpf_tokens, args);
+		switch (token) {
+		case BPF_OPT_UID:
+			if (match_int(&args[0], &opt_val))
+				return -EINVAL;
+
+			uid = make_kuid(current_user_ns(), opt_val);
+			if (!uid_valid(uid))
+				return -EINVAL;
+
+			opts->uid = uid;
+			break;
+		case BPF_OPT_GID:
+			if (match_int(&args[0], &opt_val))
+				return -EINVAL;
+
+			gid = make_kgid(current_user_ns(), opt_val);
+			if (!gid_valid(gid))
+				return -EINVAL;
+
+			opts->gid = gid;
+			break;
+		case BPF_OPT_MODE:
+			if (match_octal(&args[0], &opt_val))
+				return -EINVAL;
+
+			opts->mode = opt_val & S_IALLUGO;
+			break;
+		default:
+			return -EINVAL;
+		};
+	}
+
+	return 0;
+}
+
+static int bpf_apply_options(struct super_block *sb)
+{
+	const struct bpf_mnt_opts *opts = bpf_sb_mnt_opts(sb);
+	struct inode *inode = sb->s_root->d_inode;
+
+	inode->i_mode &= ~S_IALLUGO;
+	inode->i_mode |= opts->mode;
+
+	inode->i_uid = opts->uid;
+	inode->i_gid = opts->gid;
+
+	return 0;
+}
+
+static int bpf_show_options(struct seq_file *m, struct dentry *root)
+{
+	const struct bpf_mnt_opts *opts = bpf_sb_mnt_opts(root->d_sb);
+
+	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
+		seq_printf(m, ",uid=%u",
+			   from_kuid_munged(&init_user_ns, opts->uid));
+
+	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
+		seq_printf(m, ",gid=%u",
+			   from_kgid_munged(&init_user_ns, opts->gid));
+
+	if (opts->mode != BPFFS_DEFAULT_MODE)
+		seq_printf(m, ",mode=%o", opts->mode);
+
+	return 0;
+}
+
+static int bpf_remount(struct super_block *sb, int *flags, char *opt_data)
+{
+	struct bpf_fs_info *bfi = sb->s_fs_info;
+	int ret;
+
+	sync_filesystem(sb);
+
+	ret = bpf_parse_options(opt_data, &bfi->mnt_opts);
+	if (ret)
+		return ret;
+
+	bpf_apply_options(sb);
+	return 0;
+}
+
+static const struct super_operations bpf_super_ops = {
+	.statfs		= simple_statfs,
+	.remount_fs	= bpf_remount,
+	.show_options	= bpf_show_options,
+};
+
+static int bpf_fill_super(struct super_block *sb, void *opt_data, int silent)
+{
+	static struct tree_descr bpf_files[] = { { "" } };
+	struct bpf_dir_state *state;
+	struct bpf_fs_info *bfi;
+	struct inode *inode;
+	int ret = -ENOMEM;
+
+	bfi = kzalloc(sizeof(*bfi), GFP_KERNEL);
+	if (!bfi)
+		return ret;
+
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		goto err_bfi;
+
+	save_mount_options(sb, opt_data);
+	sb->s_fs_info = bfi;
+
+	ret = bpf_parse_options(opt_data, &bfi->mnt_opts);
+	if (ret)
+		goto err_state;
+
+	ret = simple_fill_super(sb, BPFFS_MAGIC, bpf_files);
+	if (ret)
+		goto err_state;
+
+	sb->s_op = &bpf_super_ops;
+
+	inode = sb->s_root->d_inode;
+	inode->i_op = &bpf_dir_iops;
+	inode->i_private = state;
+
+	bpf_apply_options(sb);
+
+	return 0;
+err_state:
+	kfree(state);
+err_bfi:
+	kfree(bfi);
+	return ret;
+}
+
+static void bpf_kill_super(struct super_block *sb)
+{
+	kfree(sb->s_root->d_inode->i_private);
+	kfree(sb->s_fs_info);
+	kill_litter_super(sb);
+}
+
+static struct dentry *bpf_mount(struct file_system_type *type,
+				int flags, const char *dev_name,
+				void *opt_data)
+{
+	return mount_nodev(type, flags, opt_data, bpf_fill_super);
+}
+
+static struct file_system_type bpf_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "bpf",
+	.mount		= bpf_mount,
+	.kill_sb	= bpf_kill_super,
+	.fs_flags	= FS_USERNS_MOUNT,
+};
+
+MODULE_ALIAS_FS("bpf");
+MODULE_ALIAS_FS("bpffs");
+
+static int __init bpf_init(void)
+{
+	return register_filesystem(&bpf_fs_type);
+}
+fs_initcall(bpf_init);
+
+int bpf_fd_inode_add(const struct filename *pathname,
+		     union bpf_any raw, enum bpf_fd_type type)
+{
+	umode_t i_mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct inode *dir_inode;
+	struct dentry *dentry;
+	struct path path;
+	int ret;
+
+	dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
+	if (IS_ERR(dentry)) {
+		ret = PTR_ERR(dentry);
+		return ret;
+	}
+
+	ret = security_path_mknod(&path, dentry, i_mode, 0);
+	if (ret)
+		goto out;
+
+	dir_inode = d_inode(path.dentry);
+	if (dir_inode->i_op != &bpf_dir_iops) {
+		ret = -EACCES;
+		goto out;
+	}
+
+	ret = security_inode_mknod(dir_inode, dentry, i_mode, 0);
+	if (ret)
+		goto out;
+
+	switch (type) {
+	case BPF_FD_TYPE_PROG:
+		ret = bpf_mkprog(dir_inode, dentry, raw.prog, i_mode);
+		break;
+	case BPF_FD_TYPE_MAP:
+		ret = bpf_mkmap(dir_inode, dentry, raw.map, i_mode);
+		break;
+	}
+out:
+	done_path_create(&path, dentry);
+	return ret;
+}
+
+union bpf_any bpf_fd_inode_get(const struct filename *pathname,
+			       enum bpf_fd_type *type)
+{
+	struct inode *inode;
+	union bpf_any raw;
+	struct path path;
+	int ret;
+
+	ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
+	if (ret)
+		goto out;
+
+	inode = d_backing_inode(path.dentry);
+	ret = inode_permission(inode, MAY_WRITE);
+	if (ret)
+		goto out_path;
+
+	ret = bpf_inode_type(inode, type);
+	if (ret)
+		goto out_path;
+
+	raw.raw_ptr = inode->i_private;
+	if (!raw.raw_ptr) {
+		ret = -EACCES;
+		goto out_path;
+	}
+
+	bpf_any_get(raw, *type);
+	touch_atime(&path);
+	path_put(&path);
+
+	return raw;
+out_path:
+	path_put(&path);
+out:
+	raw.raw_ptr = ERR_PTR(ret);
+	return raw;
+}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3fff82c..b4a93b8 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -679,6 +679,108 @@ free_prog_nouncharge:
 	return err;
 }
 
+void bpf_any_get(union bpf_any raw, enum bpf_fd_type type)
+{
+	switch (type) {
+	case BPF_FD_TYPE_PROG:
+		atomic_inc(&raw.prog->aux->refcnt);
+		break;
+	case BPF_FD_TYPE_MAP:
+		atomic_inc(&raw.map->refcnt);
+		break;
+	}
+}
+
+void bpf_any_put(union bpf_any raw, enum bpf_fd_type type)
+{
+	switch (type) {
+	case BPF_FD_TYPE_PROG:
+		bpf_prog_put(raw.prog);
+		break;
+	case BPF_FD_TYPE_MAP:
+		bpf_map_put(raw.map);
+		break;
+	}
+}
+
+#define BPF_PIN_FD_LAST_FIELD	pathname
+#define BPF_NEW_FD_LAST_FIELD	BPF_PIN_FD_LAST_FIELD
+
+static int bpf_pin_fd(const union bpf_attr *attr)
+{
+	struct filename *pathname;
+	enum bpf_fd_type type;
+	union bpf_any raw;
+	int ret;
+
+	if (CHECK_ATTR(BPF_PIN_FD))
+		return -EINVAL;
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	pathname = getname(u64_to_ptr(attr->pathname));
+	if (IS_ERR(pathname))
+		return PTR_ERR(pathname);
+
+	type = BPF_FD_TYPE_MAP;
+	raw.map = bpf_map_get(attr->fd);
+	if (IS_ERR(raw.map)) {
+		type = BPF_FD_TYPE_PROG;
+		raw.prog = bpf_prog_get(attr->fd);
+		if (IS_ERR(raw.prog)) {
+			ret = PTR_ERR(raw.raw_ptr);
+			goto out;
+		}
+	}
+
+	ret = bpf_fd_inode_add(pathname, raw, type);
+	if (ret != 0)
+		bpf_any_put(raw, type);
+out:
+	putname(pathname);
+	return ret;
+}
+
+static int bpf_new_fd(const union bpf_attr *attr)
+{
+	struct filename *pathname;
+	enum bpf_fd_type type;
+	union bpf_any raw;
+	int ret;
+
+	if ((CHECK_ATTR(BPF_NEW_FD)) || attr->fd != 0)
+		return -EINVAL;
+
+	pathname = getname(u64_to_ptr(attr->pathname));
+	if (IS_ERR(pathname))
+		return PTR_ERR(pathname);
+
+	raw = bpf_fd_inode_get(pathname, &type);
+	if (IS_ERR(raw.raw_ptr)) {
+		ret = PTR_ERR(raw.raw_ptr);
+		goto out;
+	}
+
+	switch (type) {
+	case BPF_FD_TYPE_PROG:
+		ret = bpf_prog_new_fd(raw.prog);
+		break;
+	case BPF_FD_TYPE_MAP:
+		ret = bpf_map_new_fd(raw.map);
+		break;
+	default:
+		/* Shut up gcc. */
+		ret = -ENOENT;
+		break;
+	}
+
+	if (ret < 0)
+		bpf_any_put(raw, type);
+out:
+	putname(pathname);
+	return ret;
+}
+
 SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
 {
 	union bpf_attr attr = {};
@@ -739,6 +841,12 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
 	case BPF_PROG_LOAD:
 		err = bpf_prog_load(&attr);
 		break;
+	case BPF_PIN_FD:
+		err = bpf_pin_fd(&attr);
+		break;
+	case BPF_NEW_FD:
+		err = bpf_new_fd(&attr);
+		break;
 	default:
 		err = -EINVAL;
 		break;
-- 
1.9.3

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