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![Ard Biesheuvel](/assets/img/avatar_default.png)
Commitbf67fad19e
("efi: Use more granular check for availability for variable services") introduced a check into the efivarfs, efi-pstore and other drivers that aborts loading of the module if not all three variable runtime services (GetVariable, SetVariable and GetNextVariable) are supported. However, this results in efivarfs being unavailable entirely if only SetVariable support is missing, which is only needed if you want to make any modifications. Also, efi-pstore and the sysfs EFI variable interface could be backed by another implementation of the 'efivars' abstraction, in which case it is completely irrelevant which services are supported by the EFI firmware. So make the generic 'efivars' abstraction dependent on the availibility of the GetVariable and GetNextVariable EFI runtime services, and add a helper 'efivar_supports_writes()' to find out whether the currently active efivars abstraction supports writes (and wire it up to the availability of SetVariable for the generic one). Then, use the efivar_supports_writes() helper to decide whether to permit efivarfs to be mounted read-write, and whether to enable efi-pstore or the sysfs EFI variable interface altogether. Fixes:bf67fad19e
("efi: Use more granular check for availability for variable services") Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de> Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
711 lines
17 KiB
C
711 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Originally from efivars.c,
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*
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* Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
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* Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
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*
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* This code takes all variables accessible from EFI runtime and
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* exports them via sysfs
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*/
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#include <linux/efi.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/ucs2_string.h>
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#include <linux/compat.h>
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#define EFIVARS_VERSION "0.08"
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#define EFIVARS_DATE "2004-May-17"
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MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
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MODULE_DESCRIPTION("sysfs interface to EFI Variables");
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MODULE_LICENSE("GPL");
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MODULE_VERSION(EFIVARS_VERSION);
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MODULE_ALIAS("platform:efivars");
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LIST_HEAD(efivar_sysfs_list);
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EXPORT_SYMBOL_GPL(efivar_sysfs_list);
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static struct kset *efivars_kset;
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static struct bin_attribute *efivars_new_var;
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static struct bin_attribute *efivars_del_var;
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struct compat_efi_variable {
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efi_char16_t VariableName[EFI_VAR_NAME_LEN/sizeof(efi_char16_t)];
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efi_guid_t VendorGuid;
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__u32 DataSize;
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__u8 Data[1024];
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__u32 Status;
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__u32 Attributes;
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} __packed;
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struct efivar_attribute {
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struct attribute attr;
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ssize_t (*show) (struct efivar_entry *entry, char *buf);
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ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
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};
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#define EFIVAR_ATTR(_name, _mode, _show, _store) \
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struct efivar_attribute efivar_attr_##_name = { \
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.attr = {.name = __stringify(_name), .mode = _mode}, \
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.show = _show, \
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.store = _store, \
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};
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#define to_efivar_attr(_attr) container_of(_attr, struct efivar_attribute, attr)
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#define to_efivar_entry(obj) container_of(obj, struct efivar_entry, kobj)
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/*
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* Prototype for sysfs creation function
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*/
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static int
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efivar_create_sysfs_entry(struct efivar_entry *new_var);
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static ssize_t
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efivar_guid_read(struct efivar_entry *entry, char *buf)
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{
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struct efi_variable *var = &entry->var;
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char *str = buf;
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if (!entry || !buf)
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return 0;
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efi_guid_to_str(&var->VendorGuid, str);
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str += strlen(str);
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str += sprintf(str, "\n");
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return str - buf;
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}
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static ssize_t
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efivar_attr_read(struct efivar_entry *entry, char *buf)
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{
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struct efi_variable *var = &entry->var;
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unsigned long size = sizeof(var->Data);
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char *str = buf;
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int ret;
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if (!entry || !buf)
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return -EINVAL;
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ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
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var->DataSize = size;
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if (ret)
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return -EIO;
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if (var->Attributes & EFI_VARIABLE_NON_VOLATILE)
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str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
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if (var->Attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)
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str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
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if (var->Attributes & EFI_VARIABLE_RUNTIME_ACCESS)
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str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\n");
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if (var->Attributes & EFI_VARIABLE_HARDWARE_ERROR_RECORD)
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str += sprintf(str, "EFI_VARIABLE_HARDWARE_ERROR_RECORD\n");
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if (var->Attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS)
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str += sprintf(str,
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"EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS\n");
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if (var->Attributes &
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EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS)
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str += sprintf(str,
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"EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS\n");
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if (var->Attributes & EFI_VARIABLE_APPEND_WRITE)
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str += sprintf(str, "EFI_VARIABLE_APPEND_WRITE\n");
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return str - buf;
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}
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static ssize_t
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efivar_size_read(struct efivar_entry *entry, char *buf)
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{
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struct efi_variable *var = &entry->var;
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unsigned long size = sizeof(var->Data);
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char *str = buf;
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int ret;
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if (!entry || !buf)
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return -EINVAL;
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ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
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var->DataSize = size;
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if (ret)
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return -EIO;
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str += sprintf(str, "0x%lx\n", var->DataSize);
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return str - buf;
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}
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static ssize_t
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efivar_data_read(struct efivar_entry *entry, char *buf)
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{
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struct efi_variable *var = &entry->var;
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unsigned long size = sizeof(var->Data);
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int ret;
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if (!entry || !buf)
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return -EINVAL;
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ret = efivar_entry_get(entry, &var->Attributes, &size, var->Data);
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var->DataSize = size;
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if (ret)
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return -EIO;
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memcpy(buf, var->Data, var->DataSize);
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return var->DataSize;
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}
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static inline int
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sanity_check(struct efi_variable *var, efi_char16_t *name, efi_guid_t vendor,
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unsigned long size, u32 attributes, u8 *data)
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{
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/*
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* If only updating the variable data, then the name
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* and guid should remain the same
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*/
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if (memcmp(name, var->VariableName, sizeof(var->VariableName)) ||
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efi_guidcmp(vendor, var->VendorGuid)) {
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printk(KERN_ERR "efivars: Cannot edit the wrong variable!\n");
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return -EINVAL;
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}
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if ((size <= 0) || (attributes == 0)){
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printk(KERN_ERR "efivars: DataSize & Attributes must be valid!\n");
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return -EINVAL;
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}
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if ((attributes & ~EFI_VARIABLE_MASK) != 0 ||
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efivar_validate(vendor, name, data, size) == false) {
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printk(KERN_ERR "efivars: Malformed variable content\n");
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return -EINVAL;
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}
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return 0;
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}
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static void
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copy_out_compat(struct efi_variable *dst, struct compat_efi_variable *src)
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{
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memcpy(dst->VariableName, src->VariableName, EFI_VAR_NAME_LEN);
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memcpy(dst->Data, src->Data, sizeof(src->Data));
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dst->VendorGuid = src->VendorGuid;
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dst->DataSize = src->DataSize;
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dst->Attributes = src->Attributes;
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}
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/*
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* We allow each variable to be edited via rewriting the
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* entire efi variable structure.
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*/
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static ssize_t
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efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
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{
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struct efi_variable *new_var, *var = &entry->var;
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efi_char16_t *name;
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unsigned long size;
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efi_guid_t vendor;
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u32 attributes;
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u8 *data;
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int err;
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if (!entry || !buf)
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return -EINVAL;
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if (in_compat_syscall()) {
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struct compat_efi_variable *compat;
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if (count != sizeof(*compat))
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return -EINVAL;
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compat = (struct compat_efi_variable *)buf;
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attributes = compat->Attributes;
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vendor = compat->VendorGuid;
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name = compat->VariableName;
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size = compat->DataSize;
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data = compat->Data;
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err = sanity_check(var, name, vendor, size, attributes, data);
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if (err)
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return err;
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copy_out_compat(&entry->var, compat);
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} else {
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if (count != sizeof(struct efi_variable))
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return -EINVAL;
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new_var = (struct efi_variable *)buf;
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attributes = new_var->Attributes;
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vendor = new_var->VendorGuid;
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name = new_var->VariableName;
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size = new_var->DataSize;
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data = new_var->Data;
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err = sanity_check(var, name, vendor, size, attributes, data);
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if (err)
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return err;
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memcpy(&entry->var, new_var, count);
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}
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err = efivar_entry_set(entry, attributes, size, data, NULL);
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if (err) {
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printk(KERN_WARNING "efivars: set_variable() failed: status=%d\n", err);
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return -EIO;
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}
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return count;
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}
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static ssize_t
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efivar_show_raw(struct efivar_entry *entry, char *buf)
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{
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struct efi_variable *var = &entry->var;
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struct compat_efi_variable *compat;
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unsigned long datasize = sizeof(var->Data);
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size_t size;
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int ret;
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if (!entry || !buf)
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return 0;
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ret = efivar_entry_get(entry, &var->Attributes, &datasize, var->Data);
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var->DataSize = datasize;
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if (ret)
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return -EIO;
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if (in_compat_syscall()) {
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compat = (struct compat_efi_variable *)buf;
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size = sizeof(*compat);
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memcpy(compat->VariableName, var->VariableName,
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EFI_VAR_NAME_LEN);
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memcpy(compat->Data, var->Data, sizeof(compat->Data));
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compat->VendorGuid = var->VendorGuid;
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compat->DataSize = var->DataSize;
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compat->Attributes = var->Attributes;
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} else {
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size = sizeof(*var);
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memcpy(buf, var, size);
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}
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return size;
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}
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/*
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* Generic read/write functions that call the specific functions of
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* the attributes...
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*/
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static ssize_t efivar_attr_show(struct kobject *kobj, struct attribute *attr,
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char *buf)
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{
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struct efivar_entry *var = to_efivar_entry(kobj);
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struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
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ssize_t ret = -EIO;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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if (efivar_attr->show) {
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ret = efivar_attr->show(var, buf);
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}
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return ret;
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}
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static ssize_t efivar_attr_store(struct kobject *kobj, struct attribute *attr,
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const char *buf, size_t count)
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{
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struct efivar_entry *var = to_efivar_entry(kobj);
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struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
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ssize_t ret = -EIO;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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if (efivar_attr->store)
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ret = efivar_attr->store(var, buf, count);
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return ret;
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}
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static const struct sysfs_ops efivar_attr_ops = {
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.show = efivar_attr_show,
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.store = efivar_attr_store,
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};
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static void efivar_release(struct kobject *kobj)
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{
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struct efivar_entry *var = to_efivar_entry(kobj);
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kfree(var);
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}
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static EFIVAR_ATTR(guid, 0400, efivar_guid_read, NULL);
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static EFIVAR_ATTR(attributes, 0400, efivar_attr_read, NULL);
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static EFIVAR_ATTR(size, 0400, efivar_size_read, NULL);
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static EFIVAR_ATTR(data, 0400, efivar_data_read, NULL);
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static EFIVAR_ATTR(raw_var, 0600, efivar_show_raw, efivar_store_raw);
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static struct attribute *def_attrs[] = {
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&efivar_attr_guid.attr,
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&efivar_attr_size.attr,
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&efivar_attr_attributes.attr,
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&efivar_attr_data.attr,
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&efivar_attr_raw_var.attr,
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NULL,
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};
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static struct kobj_type efivar_ktype = {
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.release = efivar_release,
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.sysfs_ops = &efivar_attr_ops,
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.default_attrs = def_attrs,
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};
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static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buf, loff_t pos, size_t count)
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{
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struct compat_efi_variable *compat = (struct compat_efi_variable *)buf;
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struct efi_variable *new_var = (struct efi_variable *)buf;
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struct efivar_entry *new_entry;
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bool need_compat = in_compat_syscall();
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efi_char16_t *name;
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unsigned long size;
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u32 attributes;
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u8 *data;
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int err;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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if (need_compat) {
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if (count != sizeof(*compat))
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return -EINVAL;
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attributes = compat->Attributes;
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name = compat->VariableName;
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size = compat->DataSize;
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data = compat->Data;
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} else {
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if (count != sizeof(*new_var))
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return -EINVAL;
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attributes = new_var->Attributes;
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name = new_var->VariableName;
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size = new_var->DataSize;
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data = new_var->Data;
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}
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if ((attributes & ~EFI_VARIABLE_MASK) != 0 ||
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efivar_validate(new_var->VendorGuid, name, data,
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size) == false) {
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printk(KERN_ERR "efivars: Malformed variable content\n");
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return -EINVAL;
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}
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new_entry = kzalloc(sizeof(*new_entry), GFP_KERNEL);
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if (!new_entry)
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return -ENOMEM;
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if (need_compat)
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copy_out_compat(&new_entry->var, compat);
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else
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memcpy(&new_entry->var, new_var, sizeof(*new_var));
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err = efivar_entry_set(new_entry, attributes, size,
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data, &efivar_sysfs_list);
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if (err) {
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if (err == -EEXIST)
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err = -EINVAL;
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goto out;
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}
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if (efivar_create_sysfs_entry(new_entry)) {
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printk(KERN_WARNING "efivars: failed to create sysfs entry.\n");
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kfree(new_entry);
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}
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return count;
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out:
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kfree(new_entry);
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return err;
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}
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static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
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struct bin_attribute *bin_attr,
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char *buf, loff_t pos, size_t count)
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{
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struct efi_variable *del_var = (struct efi_variable *)buf;
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struct compat_efi_variable *compat;
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struct efivar_entry *entry;
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efi_char16_t *name;
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efi_guid_t vendor;
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int err = 0;
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if (!capable(CAP_SYS_ADMIN))
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return -EACCES;
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if (in_compat_syscall()) {
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if (count != sizeof(*compat))
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return -EINVAL;
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compat = (struct compat_efi_variable *)buf;
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name = compat->VariableName;
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vendor = compat->VendorGuid;
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} else {
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if (count != sizeof(*del_var))
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return -EINVAL;
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name = del_var->VariableName;
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vendor = del_var->VendorGuid;
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}
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if (efivar_entry_iter_begin())
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return -EINTR;
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entry = efivar_entry_find(name, vendor, &efivar_sysfs_list, true);
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if (!entry)
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err = -EINVAL;
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else if (__efivar_entry_delete(entry))
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err = -EIO;
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if (err) {
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efivar_entry_iter_end();
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return err;
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}
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if (!entry->scanning) {
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efivar_entry_iter_end();
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efivar_unregister(entry);
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} else
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efivar_entry_iter_end();
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/* It's dead Jim.... */
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return count;
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}
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/**
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* efivar_create_sysfs_entry - create a new entry in sysfs
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* @new_var: efivar entry to create
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*
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* Returns 0 on success, negative error code on failure
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*/
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static int
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efivar_create_sysfs_entry(struct efivar_entry *new_var)
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{
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int short_name_size;
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char *short_name;
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unsigned long utf8_name_size;
|
|
efi_char16_t *variable_name = new_var->var.VariableName;
|
|
int ret;
|
|
|
|
/*
|
|
* Length of the variable bytes in UTF8, plus the '-' separator,
|
|
* plus the GUID, plus trailing NUL
|
|
*/
|
|
utf8_name_size = ucs2_utf8size(variable_name);
|
|
short_name_size = utf8_name_size + 1 + EFI_VARIABLE_GUID_LEN + 1;
|
|
|
|
short_name = kmalloc(short_name_size, GFP_KERNEL);
|
|
if (!short_name)
|
|
return -ENOMEM;
|
|
|
|
ucs2_as_utf8(short_name, variable_name, short_name_size);
|
|
|
|
/* This is ugly, but necessary to separate one vendor's
|
|
private variables from another's. */
|
|
short_name[utf8_name_size] = '-';
|
|
efi_guid_to_str(&new_var->var.VendorGuid,
|
|
short_name + utf8_name_size + 1);
|
|
|
|
new_var->kobj.kset = efivars_kset;
|
|
|
|
ret = kobject_init_and_add(&new_var->kobj, &efivar_ktype,
|
|
NULL, "%s", short_name);
|
|
kfree(short_name);
|
|
if (ret) {
|
|
kobject_put(&new_var->kobj);
|
|
return ret;
|
|
}
|
|
|
|
kobject_uevent(&new_var->kobj, KOBJ_ADD);
|
|
if (efivar_entry_add(new_var, &efivar_sysfs_list)) {
|
|
efivar_unregister(new_var);
|
|
return -EINTR;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int
|
|
create_efivars_bin_attributes(void)
|
|
{
|
|
struct bin_attribute *attr;
|
|
int error;
|
|
|
|
/* new_var */
|
|
attr = kzalloc(sizeof(*attr), GFP_KERNEL);
|
|
if (!attr)
|
|
return -ENOMEM;
|
|
|
|
attr->attr.name = "new_var";
|
|
attr->attr.mode = 0200;
|
|
attr->write = efivar_create;
|
|
efivars_new_var = attr;
|
|
|
|
/* del_var */
|
|
attr = kzalloc(sizeof(*attr), GFP_KERNEL);
|
|
if (!attr) {
|
|
error = -ENOMEM;
|
|
goto out_free;
|
|
}
|
|
attr->attr.name = "del_var";
|
|
attr->attr.mode = 0200;
|
|
attr->write = efivar_delete;
|
|
efivars_del_var = attr;
|
|
|
|
sysfs_bin_attr_init(efivars_new_var);
|
|
sysfs_bin_attr_init(efivars_del_var);
|
|
|
|
/* Register */
|
|
error = sysfs_create_bin_file(&efivars_kset->kobj, efivars_new_var);
|
|
if (error) {
|
|
printk(KERN_ERR "efivars: unable to create new_var sysfs file"
|
|
" due to error %d\n", error);
|
|
goto out_free;
|
|
}
|
|
|
|
error = sysfs_create_bin_file(&efivars_kset->kobj, efivars_del_var);
|
|
if (error) {
|
|
printk(KERN_ERR "efivars: unable to create del_var sysfs file"
|
|
" due to error %d\n", error);
|
|
sysfs_remove_bin_file(&efivars_kset->kobj, efivars_new_var);
|
|
goto out_free;
|
|
}
|
|
|
|
return 0;
|
|
out_free:
|
|
kfree(efivars_del_var);
|
|
efivars_del_var = NULL;
|
|
kfree(efivars_new_var);
|
|
efivars_new_var = NULL;
|
|
return error;
|
|
}
|
|
|
|
static int efivar_update_sysfs_entry(efi_char16_t *name, efi_guid_t vendor,
|
|
unsigned long name_size, void *data)
|
|
{
|
|
struct efivar_entry *entry = data;
|
|
|
|
if (efivar_entry_find(name, vendor, &efivar_sysfs_list, false))
|
|
return 0;
|
|
|
|
memcpy(entry->var.VariableName, name, name_size);
|
|
memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
|
|
|
|
return 1;
|
|
}
|
|
|
|
static void efivar_update_sysfs_entries(struct work_struct *work)
|
|
{
|
|
struct efivar_entry *entry;
|
|
int err;
|
|
|
|
/* Add new sysfs entries */
|
|
while (1) {
|
|
entry = kzalloc(sizeof(*entry), GFP_KERNEL);
|
|
if (!entry)
|
|
return;
|
|
|
|
err = efivar_init(efivar_update_sysfs_entry, entry,
|
|
false, &efivar_sysfs_list);
|
|
if (!err)
|
|
break;
|
|
|
|
efivar_create_sysfs_entry(entry);
|
|
}
|
|
|
|
kfree(entry);
|
|
}
|
|
|
|
static int efivars_sysfs_callback(efi_char16_t *name, efi_guid_t vendor,
|
|
unsigned long name_size, void *data)
|
|
{
|
|
struct efivar_entry *entry;
|
|
|
|
entry = kzalloc(sizeof(*entry), GFP_KERNEL);
|
|
if (!entry)
|
|
return -ENOMEM;
|
|
|
|
memcpy(entry->var.VariableName, name, name_size);
|
|
memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
|
|
|
|
efivar_create_sysfs_entry(entry);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
|
|
{
|
|
int err = efivar_entry_remove(entry);
|
|
|
|
if (err)
|
|
return err;
|
|
efivar_unregister(entry);
|
|
return 0;
|
|
}
|
|
|
|
static void efivars_sysfs_exit(void)
|
|
{
|
|
/* Remove all entries and destroy */
|
|
int err;
|
|
|
|
err = __efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list,
|
|
NULL, NULL);
|
|
if (err) {
|
|
pr_err("efivars: Failed to destroy sysfs entries\n");
|
|
return;
|
|
}
|
|
|
|
if (efivars_new_var)
|
|
sysfs_remove_bin_file(&efivars_kset->kobj, efivars_new_var);
|
|
if (efivars_del_var)
|
|
sysfs_remove_bin_file(&efivars_kset->kobj, efivars_del_var);
|
|
kfree(efivars_new_var);
|
|
kfree(efivars_del_var);
|
|
kset_unregister(efivars_kset);
|
|
}
|
|
|
|
int efivars_sysfs_init(void)
|
|
{
|
|
struct kobject *parent_kobj = efivars_kobject();
|
|
int error = 0;
|
|
|
|
/* No efivars has been registered yet */
|
|
if (!parent_kobj || !efivar_supports_writes())
|
|
return 0;
|
|
|
|
printk(KERN_INFO "EFI Variables Facility v%s %s\n", EFIVARS_VERSION,
|
|
EFIVARS_DATE);
|
|
|
|
efivars_kset = kset_create_and_add("vars", NULL, parent_kobj);
|
|
if (!efivars_kset) {
|
|
printk(KERN_ERR "efivars: Subsystem registration failed.\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
efivar_init(efivars_sysfs_callback, NULL, true, &efivar_sysfs_list);
|
|
|
|
error = create_efivars_bin_attributes();
|
|
if (error) {
|
|
efivars_sysfs_exit();
|
|
return error;
|
|
}
|
|
|
|
INIT_WORK(&efivar_work, efivar_update_sysfs_entries);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(efivars_sysfs_init);
|
|
|
|
module_init(efivars_sysfs_init);
|
|
module_exit(efivars_sysfs_exit);
|