Commit 88ee9d57 authored by Jan (janneke) Nieuwenhuizen's avatar Jan (janneke) Nieuwenhuizen Committed by Theodore Ts'o
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ext4: support xattr gnu.* namespace for the Hurd 

The Hurd gained[0] support for moving the translator and author
fields out of the inode and into the "gnu.*" xattr namespace.

In anticipation of that, an xattr INDEX was reserved[1].  The Hurd has
now been brought into compliance[2] with that.

This patch adds support for reading and writing such attributes from
Linux; you can now do something like

    mkdir -p hurd-root/servers/socket
    touch hurd-root/servers/socket/1
    setfattr --name=gnu.translator --value='"/hurd/pflocal\0"' \
        hurd-root/servers/socket/1
    getfattr --name=gnu.translator hurd-root/servers/socket/1
    # file: 1
    gnu.translator="/hurd/pflocal"

to setup a pipe translator, which is being used to create[3] a
vm-image for the Hurd from GNU Guix.

[0] https://summerofcode.withgoogle.com/projects/#5869799859027968
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3980bd3b406addb327d858aebd19e229ea340b9a
[2] https://git.savannah.gnu.org/cgit/hurd/hurd.git/commit/?id=a04c7bf83172faa7cb080fbe3b6c04a8415ca645
[3] https://git.savannah.gnu.org/cgit/guix.git/log/?h=wip-hurd-vm



Signed-off-by: default avatarJan Nieuwenhuizen <janneke@gnu.org>
Link: https://lore.kernel.org/r/20200525193940.878-1-janneke@gnu.org


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 81198536

fs/ext4/Makefile

+2 −1
Original line number Diff line number Diff line
@@ -9,7 +9,8 @@ ext4-y := balloc.o bitmap.o block_validity.o dir.o ext4_jbd2.o extents.o \ 
		extents_status.o file.o fsmap.o fsync.o hash.o ialloc.o \

		indirect.o inline.o inode.o ioctl.o mballoc.o migrate.o \

		mmp.o move_extent.o namei.o page-io.o readpage.o resize.o \

		super.o symlink.o sysfs.o xattr.o xattr_trusted.o xattr_user.o

		super.o symlink.o sysfs.o xattr.o xattr_hurd.o xattr_trusted.o \

		xattr_user.o



ext4-$(CONFIG_EXT4_FS_POSIX_ACL)	+= acl.o

ext4-$(CONFIG_EXT4_FS_SECURITY)		+= xattr_security.o

fs/ext4/xattr.c

+2 −0
Original line number Diff line number Diff line
@@ -93,6 +93,7 @@ static const struct xattr_handler * const ext4_xattr_handler_map[] = { 
#ifdef CONFIG_EXT4_FS_SECURITY

	[EXT4_XATTR_INDEX_SECURITY]	     = &ext4_xattr_security_handler,

#endif

	[EXT4_XATTR_INDEX_HURD]		     = &ext4_xattr_hurd_handler,

};



const struct xattr_handler *ext4_xattr_handlers[] = {
@@ -105,6 +106,7 @@ const struct xattr_handler *ext4_xattr_handlers[] = { 
#ifdef CONFIG_EXT4_FS_SECURITY

	&ext4_xattr_security_handler,

#endif

	&ext4_xattr_hurd_handler,

	NULL

};

fs/ext4/xattr.h

+1 −0
Original line number Diff line number Diff line
@@ -124,6 +124,7 @@ struct ext4_xattr_inode_array { 
extern const struct xattr_handler ext4_xattr_user_handler;

extern const struct xattr_handler ext4_xattr_trusted_handler;

extern const struct xattr_handler ext4_xattr_security_handler;

extern const struct xattr_handler ext4_xattr_hurd_handler;



#define EXT4_XATTR_NAME_ENCRYPTION_CONTEXT "c"

fs/ext4/xattr_hurd.c

0 → 100644
+51 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * linux/fs/ext4/xattr_hurd.c

 * Handler for extended gnu attributes for the Hurd.

 *

 * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>

 * Copyright (C) 2020 by Jan (janneke) Nieuwenhuizen, <janneke@gnu.org>

 */



#include <linux/init.h>

#include <linux/string.h>

#include "ext4.h"

#include "xattr.h"



static bool

ext4_xattr_hurd_list(struct dentry *dentry)

{

	return test_opt(dentry->d_sb, XATTR_USER);

}



static int

ext4_xattr_hurd_get(const struct xattr_handler *handler,

		    struct dentry *unused, struct inode *inode,

		    const char *name, void *buffer, size_t size)

{

	if (!test_opt(inode->i_sb, XATTR_USER))

		return -EOPNOTSUPP;



	return ext4_xattr_get(inode, EXT4_XATTR_INDEX_HURD,

			      name, buffer, size);

}



static int

ext4_xattr_hurd_set(const struct xattr_handler *handler,

		    struct dentry *unused, struct inode *inode,

		    const char *name, const void *value,

		    size_t size, int flags)

{

	if (!test_opt(inode->i_sb, XATTR_USER))

		return -EOPNOTSUPP;



	return ext4_xattr_set(inode, EXT4_XATTR_INDEX_HURD,

			      name, value, size, flags);

}



const struct xattr_handler ext4_xattr_hurd_handler = {

	.prefix	= XATTR_HURD_PREFIX,

	.list	= ext4_xattr_hurd_list,

	.get	= ext4_xattr_hurd_get,

	.set	= ext4_xattr_hurd_set,

};

include/uapi/linux/xattr.h

+4 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>

  Copyright (c) 2001-2002 Silicon Graphics, Inc.  All Rights Reserved.

  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>

  Copyright (c) 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>

*/



#include <linux/libc-compat.h>
@@ -31,6 +32,9 @@ 
#define XATTR_BTRFS_PREFIX "btrfs."

#define XATTR_BTRFS_PREFIX_LEN (sizeof(XATTR_BTRFS_PREFIX) - 1)



#define XATTR_HURD_PREFIX "gnu."

#define XATTR_HURD_PREFIX_LEN (sizeof(XATTR_HURD_PREFIX) - 1)



#define XATTR_SECURITY_PREFIX	"security."

#define XATTR_SECURITY_PREFIX_LEN (sizeof(XATTR_SECURITY_PREFIX) - 1)

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