1. 根目录:
2. fs
3. ext4
4. xattr_trusted.c

/*
 * linux/fs/ext4/xattr_trusted.c
 * Handler for trusted extended attributes.
 *
 * Copyright (C) 2003 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
 */

#include <linux/string.h>
#include <linux/capability.h>
#include <linux/fs.h>
#include "ext4_jbd2.h"
#include "ext4.h"
#include "xattr.h"

static size_t
ext4_xattr_trusted_list(struct dentry *dentry, char *list, size_t list_size,
		const char *name, size_t name_len, int type)
{
	const size_t prefix_len = XATTR_TRUSTED_PREFIX_LEN;
	const size_t total_len = prefix_len + name_len + 1;

	if (!capable(CAP_SYS_ADMIN))
		return 0;

	if (list && total_len <= list_size) {
		memcpy(list, XATTR_TRUSTED_PREFIX, prefix_len);
		memcpy(list+prefix_len, name, name_len);
		list[prefix_len + name_len] = '\0';
	}
	return total_len;
}

static int
ext4_xattr_trusted_get(struct dentry *dentry, const char *name, void *buffer,
		size_t size, int type)
{
	if (strcmp(name, "") == 0)
		return -EINVAL;
	return ext4_xattr_get(dentry->d_inode, EXT4_XATTR_INDEX_TRUSTED,
			      name, buffer, size);
}

static int
ext4_xattr_trusted_set(struct dentry *dentry, const char *name,
		const void *value, size_t size, int flags, int type)
{
	if (strcmp(name, "") == 0)
		return -EINVAL;
	return ext4_xattr_set(dentry->d_inode, EXT4_XATTR_INDEX_TRUSTED,
			      name, value, size, flags);
}

const struct xattr_handler ext4_xattr_trusted_handler = {
	.prefix	= XATTR_TRUSTED_PREFIX,
	.list	= ext4_xattr_trusted_list,
	.get	= ext4_xattr_trusted_get,
	.set	= ext4_xattr_trusted_set,
};