fs, fscrypt: move uapi definitions to new header <linux/fscrypt.h>

More fscrypt definitions are being added, and we shouldn't use a
disproportionate amount of space in <linux/fs.h> for fscrypt stuff.
So move the fscrypt definitions to a new header <linux/fscrypt.h>.

For source compatibility with existing userspace programs, <linux/fs.h>
still includes the new header.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>

MAINTAINERS

@@ -6603,6 +6603,7 @@ T:	git git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git
 S:	Supported
 F:	fs/crypto/
 F:	include/linux/fscrypt*.h
+F:	include/uapi/linux/fscrypt.h
 F:	Documentation/filesystems/fscrypt.rst
 
 FSI SUBSYSTEM

include/linux/fscrypt.h

@@ -16,6 +16,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <uapi/linux/fscrypt.h>
 
 #define FS_CRYPTO_BLOCK_SIZE		16
 

include/uapi/linux/fs.h

@@ -13,6 +13,9 @@
 #include <linux/limits.h>
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#ifndef __KERNEL__
+#include <linux/fscrypt.h>
+#endif
 
 /* Use of MS_* flags within the kernel is restricted to core mount(2) code. */
 #if !defined(__KERNEL__)
@@ -212,57 +215,6 @@ struct fsxattr {
 #define FS_IOC_GETFSLABEL		_IOR(0x94, 49, char[FSLABEL_MAX])
 #define FS_IOC_SETFSLABEL		_IOW(0x94, 50, char[FSLABEL_MAX])
 
-/*
- * File system encryption support
- */
-/* Policy provided via an ioctl on the topmost directory */
-#define FS_KEY_DESCRIPTOR_SIZE	8
-
-#define FS_POLICY_FLAGS_PAD_4		0x00
-#define FS_POLICY_FLAGS_PAD_8		0x01
-#define FS_POLICY_FLAGS_PAD_16		0x02
-#define FS_POLICY_FLAGS_PAD_32		0x03
-#define FS_POLICY_FLAGS_PAD_MASK	0x03
-#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
-#define FS_POLICY_FLAGS_VALID		0x07
-
-/* Encryption algorithms */
-#define FS_ENCRYPTION_MODE_INVALID		0
-#define FS_ENCRYPTION_MODE_AES_256_XTS		1
-#define FS_ENCRYPTION_MODE_AES_256_GCM		2
-#define FS_ENCRYPTION_MODE_AES_256_CBC		3
-#define FS_ENCRYPTION_MODE_AES_256_CTS		4
-#define FS_ENCRYPTION_MODE_AES_128_CBC		5
-#define FS_ENCRYPTION_MODE_AES_128_CTS		6
-#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_ADIANTUM		9
-
-struct fscrypt_policy {
-	__u8 version;
-	__u8 contents_encryption_mode;
-	__u8 filenames_encryption_mode;
-	__u8 flags;
-	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-};
-
-#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
-#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
-#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
-
-/* Parameters for passing an encryption key into the kernel keyring */
-#define FS_KEY_DESC_PREFIX		"fscrypt:"
-#define FS_KEY_DESC_PREFIX_SIZE		8
-
-/* Structure that userspace passes to the kernel keyring */
-#define FS_MAX_KEY_SIZE			64
-
-struct fscrypt_key {
-	__u32 mode;
-	__u8 raw[FS_MAX_KEY_SIZE];
-	__u32 size;
-};
-
 /*
  * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
  *

include/uapi/linux/fscrypt.h

@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * fscrypt user API
+ *
+ * These ioctls can be used on filesystems that support fscrypt.  See the
+ * "User API" section of Documentation/filesystems/fscrypt.rst.
+ */
+#ifndef _UAPI_LINUX_FSCRYPT_H
+#define _UAPI_LINUX_FSCRYPT_H
+
+#include <linux/types.h>
+
+#define FS_KEY_DESCRIPTOR_SIZE	8
+
+/* Encryption policy flags */
+#define FS_POLICY_FLAGS_PAD_4		0x00
+#define FS_POLICY_FLAGS_PAD_8		0x01
+#define FS_POLICY_FLAGS_PAD_16		0x02
+#define FS_POLICY_FLAGS_PAD_32		0x03
+#define FS_POLICY_FLAGS_PAD_MASK	0x03
+#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
+#define FS_POLICY_FLAGS_VALID		0x07
+
+/* Encryption algorithms */
+#define FS_ENCRYPTION_MODE_INVALID		0
+#define FS_ENCRYPTION_MODE_AES_256_XTS		1
+#define FS_ENCRYPTION_MODE_AES_256_GCM		2
+#define FS_ENCRYPTION_MODE_AES_256_CBC		3
+#define FS_ENCRYPTION_MODE_AES_256_CTS		4
+#define FS_ENCRYPTION_MODE_AES_128_CBC		5
+#define FS_ENCRYPTION_MODE_AES_128_CTS		6
+#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
+#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
+#define FS_ENCRYPTION_MODE_ADIANTUM		9
+
+struct fscrypt_policy {
+	__u8 version;
+	__u8 contents_encryption_mode;
+	__u8 filenames_encryption_mode;
+	__u8 flags;
+	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+};
+
+#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
+#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
+
+/* Parameters for passing an encryption key into the kernel keyring */
+#define FS_KEY_DESC_PREFIX		"fscrypt:"
+#define FS_KEY_DESC_PREFIX_SIZE		8
+
+/* Structure that userspace passes to the kernel keyring */
+#define FS_MAX_KEY_SIZE			64
+
+struct fscrypt_key {
+	__u32 mode;
+	__u8 raw[FS_MAX_KEY_SIZE];
+	__u32 size;
+};
+
+#endif /* _UAPI_LINUX_FSCRYPT_H */