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d86ff3333c
When writing EFI variables, one might get errors with no other message on why it fails. Being able to see how much is used by EFI variables helps analyzing such issues. Since this is not a conventional filesystem, block size is intentionally set to 1 instead of PAGE_SIZE. x86 quirks of reserved size are taken into account; so that available and free size can be different, further helping debugging space issues. With this patch, one can see the remaining space in EFI variable storage via efivarfs, like this: $ df -h /sys/firmware/efi/efivars/ Filesystem Size Used Avail Use% Mounted on efivarfs 176K 106K 66K 62% /sys/firmware/efi/efivars Signed-off-by: Anisse Astier <an.astier@criteo.com> [ardb: - rename efi_reserved_space() to efivar_reserved_space() - whitespace/coding style tweaks] Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
317 lines
7.4 KiB
C
317 lines
7.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2012 Red Hat, Inc.
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* Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
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*/
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#include <linux/ctype.h>
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#include <linux/efi.h>
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#include <linux/fs.h>
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#include <linux/fs_context.h>
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#include <linux/module.h>
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#include <linux/pagemap.h>
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#include <linux/ucs2_string.h>
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#include <linux/slab.h>
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#include <linux/magic.h>
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#include <linux/statfs.h>
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#include "internal.h"
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LIST_HEAD(efivarfs_list);
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static void efivarfs_evict_inode(struct inode *inode)
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{
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clear_inode(inode);
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}
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static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
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{
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const u32 attr = EFI_VARIABLE_NON_VOLATILE |
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EFI_VARIABLE_BOOTSERVICE_ACCESS |
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EFI_VARIABLE_RUNTIME_ACCESS;
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u64 storage_space, remaining_space, max_variable_size;
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efi_status_t status;
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status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
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&max_variable_size);
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if (status != EFI_SUCCESS)
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return efi_status_to_err(status);
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/*
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* This is not a normal filesystem, so no point in pretending it has a block
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* size; we declare f_bsize to 1, so that we can then report the exact value
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* sent by EFI QueryVariableInfo in f_blocks and f_bfree
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*/
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buf->f_bsize = 1;
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buf->f_namelen = NAME_MAX;
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buf->f_blocks = storage_space;
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buf->f_bfree = remaining_space;
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buf->f_type = dentry->d_sb->s_magic;
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/*
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* In f_bavail we declare the free space that the kernel will allow writing
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* when the storage_paranoia x86 quirk is active. To use more, users
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* should boot the kernel with efi_no_storage_paranoia.
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*/
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if (remaining_space > efivar_reserved_space())
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buf->f_bavail = remaining_space - efivar_reserved_space();
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else
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buf->f_bavail = 0;
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return 0;
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}
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static const struct super_operations efivarfs_ops = {
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.statfs = efivarfs_statfs,
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.drop_inode = generic_delete_inode,
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.evict_inode = efivarfs_evict_inode,
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};
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/*
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* Compare two efivarfs file names.
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*
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* An efivarfs filename is composed of two parts,
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*
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* 1. A case-sensitive variable name
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* 2. A case-insensitive GUID
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*
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* So we need to perform a case-sensitive match on part 1 and a
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* case-insensitive match on part 2.
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*/
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static int efivarfs_d_compare(const struct dentry *dentry,
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unsigned int len, const char *str,
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const struct qstr *name)
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{
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int guid = len - EFI_VARIABLE_GUID_LEN;
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if (name->len != len)
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return 1;
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/* Case-sensitive compare for the variable name */
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if (memcmp(str, name->name, guid))
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return 1;
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/* Case-insensitive compare for the GUID */
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return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
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}
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static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
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{
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unsigned long hash = init_name_hash(dentry);
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const unsigned char *s = qstr->name;
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unsigned int len = qstr->len;
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if (!efivarfs_valid_name(s, len))
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return -EINVAL;
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while (len-- > EFI_VARIABLE_GUID_LEN)
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hash = partial_name_hash(*s++, hash);
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/* GUID is case-insensitive. */
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while (len--)
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hash = partial_name_hash(tolower(*s++), hash);
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qstr->hash = end_name_hash(hash);
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return 0;
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}
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static const struct dentry_operations efivarfs_d_ops = {
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.d_compare = efivarfs_d_compare,
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.d_hash = efivarfs_d_hash,
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.d_delete = always_delete_dentry,
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};
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static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
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{
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struct dentry *d;
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struct qstr q;
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int err;
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q.name = name;
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q.len = strlen(name);
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err = efivarfs_d_hash(parent, &q);
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if (err)
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return ERR_PTR(err);
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d = d_alloc(parent, &q);
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if (d)
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return d;
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return ERR_PTR(-ENOMEM);
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}
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static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
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unsigned long name_size, void *data)
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{
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struct super_block *sb = (struct super_block *)data;
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struct efivar_entry *entry;
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struct inode *inode = NULL;
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struct dentry *dentry, *root = sb->s_root;
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unsigned long size = 0;
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char *name;
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int len;
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int err = -ENOMEM;
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bool is_removable = false;
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if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
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return 0;
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entry = kzalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry)
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return err;
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memcpy(entry->var.VariableName, name16, name_size);
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memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
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len = ucs2_utf8size(entry->var.VariableName);
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/* name, plus '-', plus GUID, plus NUL*/
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name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
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if (!name)
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goto fail;
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ucs2_as_utf8(name, entry->var.VariableName, len);
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if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
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is_removable = true;
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name[len] = '-';
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efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
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name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
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/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
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strreplace(name, '/', '!');
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inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
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is_removable);
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if (!inode)
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goto fail_name;
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dentry = efivarfs_alloc_dentry(root, name);
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if (IS_ERR(dentry)) {
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err = PTR_ERR(dentry);
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goto fail_inode;
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}
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__efivar_entry_get(entry, NULL, &size, NULL);
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__efivar_entry_add(entry, &efivarfs_list);
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/* copied by the above to local storage in the dentry. */
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kfree(name);
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inode_lock(inode);
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inode->i_private = entry;
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i_size_write(inode, size + sizeof(entry->var.Attributes));
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inode_unlock(inode);
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d_add(dentry, inode);
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return 0;
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fail_inode:
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iput(inode);
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fail_name:
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kfree(name);
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fail:
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kfree(entry);
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return err;
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}
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static int efivarfs_destroy(struct efivar_entry *entry, void *data)
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{
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efivar_entry_remove(entry);
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kfree(entry);
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return 0;
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}
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static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
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{
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struct inode *inode = NULL;
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struct dentry *root;
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int err;
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if (!efivar_is_available())
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return -EOPNOTSUPP;
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sb->s_maxbytes = MAX_LFS_FILESIZE;
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sb->s_blocksize = PAGE_SIZE;
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sb->s_blocksize_bits = PAGE_SHIFT;
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sb->s_magic = EFIVARFS_MAGIC;
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sb->s_op = &efivarfs_ops;
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sb->s_d_op = &efivarfs_d_ops;
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sb->s_time_gran = 1;
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if (!efivar_supports_writes())
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sb->s_flags |= SB_RDONLY;
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inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
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if (!inode)
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return -ENOMEM;
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inode->i_op = &efivarfs_dir_inode_operations;
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root = d_make_root(inode);
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sb->s_root = root;
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if (!root)
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return -ENOMEM;
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INIT_LIST_HEAD(&efivarfs_list);
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err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
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if (err)
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efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
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return err;
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}
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static int efivarfs_get_tree(struct fs_context *fc)
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{
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return get_tree_single(fc, efivarfs_fill_super);
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}
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static const struct fs_context_operations efivarfs_context_ops = {
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.get_tree = efivarfs_get_tree,
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};
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static int efivarfs_init_fs_context(struct fs_context *fc)
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{
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fc->ops = &efivarfs_context_ops;
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return 0;
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}
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static void efivarfs_kill_sb(struct super_block *sb)
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{
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kill_litter_super(sb);
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if (!efivar_is_available())
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return;
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/* Remove all entries and destroy */
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efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
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}
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static struct file_system_type efivarfs_type = {
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.owner = THIS_MODULE,
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.name = "efivarfs",
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.init_fs_context = efivarfs_init_fs_context,
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.kill_sb = efivarfs_kill_sb,
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};
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static __init int efivarfs_init(void)
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{
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return register_filesystem(&efivarfs_type);
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}
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static __exit void efivarfs_exit(void)
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{
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unregister_filesystem(&efivarfs_type);
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}
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MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
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MODULE_DESCRIPTION("EFI Variable Filesystem");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_FS("efivarfs");
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module_init(efivarfs_init);
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module_exit(efivarfs_exit);
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