efivars: Keep a private global pointer to efivars

Some machines have an EFI variable interface that does not conform to
the UEFI specification, e.g. CONFIG_GOOGLE_SMI. Add the necessary code
so that it's only possible to use one implementation of EFI variable
operations at runtime. This allows us to keep a single (file-scope)
global pointer 'struct efivars', which simplifies access. This will
hopefully dissuade developers from accessing the generic operations
struct directly in the future, as was done in the efivarfs and pstore
code, thereby allowing future code to work with both the generic efivar
ops and the google SMI ops.

This may seem like a step backwards in terms of modularity, but we don't
need to track more than one 'struct efivars' at one time. There is no
synchronisation done between multiple EFI variable operations, and
according to Mike no one is using both the generic EFI var ops and
CONFIG_GOOGLE_SMI simultaneously, though a single kernel build _does_
need to able to support both. It also helps to clearly highlight which
functions form the core of the efivars interface - those that require
access to __efivars.
Reviewed-by: NTom Gundersen <teg@jklm.no>
Tested-by: NTom Gundersen <teg@jklm.no>
Acked-by: NMike Waychison <mikew@google.com>
Signed-off-by: NMatt Fleming <matt.fleming@intel.com>

drivers/firmware/efivars.c

@@ -125,7 +125,6 @@ struct efi_variable {
 } __attribute__((packed));
 
 struct efivar_entry {
-	struct efivars *efivars;
 	struct efi_variable var;
 	struct list_head list;
 	struct kobject kobj;
@@ -137,8 +136,8 @@ struct efivar_attribute {
 	ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
 };
 
-static struct efivars __efivars;
-static struct efivar_operations ops;
+/* Private pointer to registered efivars */
+static struct efivars *__efivars;
 
 #define PSTORE_EFI_ATTRIBUTES \
 	(EFI_VARIABLE_NON_VOLATILE | \
@@ -479,7 +478,7 @@ efivar_attr_read(struct efivar_entry *entry, char *buf)
 	if (!entry || !buf)
 		return -EINVAL;
 
-	status = get_var_data(entry->efivars, var);
+	status = get_var_data(__efivars, var);
 	if (status != EFI_SUCCESS)
 		return -EIO;
 
@@ -513,7 +512,7 @@ efivar_size_read(struct efivar_entry *entry, char *buf)
 	if (!entry || !buf)
 		return -EINVAL;
 
-	status = get_var_data(entry->efivars, var);
+	status = get_var_data(__efivars, var);
 	if (status != EFI_SUCCESS)
 		return -EIO;
 
@@ -530,7 +529,7 @@ efivar_data_read(struct efivar_entry *entry, char *buf)
 	if (!entry || !buf)
 		return -EINVAL;
 
-	status = get_var_data(entry->efivars, var);
+	status = get_var_data(__efivars, var);
 	if (status != EFI_SUCCESS)
 		return -EIO;
 
@@ -545,7 +544,7 @@ static ssize_t
 efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
 {
 	struct efi_variable *new_var, *var = &entry->var;
-	struct efivars *efivars = entry->efivars;
+	struct efivars *efivars = __efivars;
 	efi_status_t status = EFI_NOT_FOUND;
 
 	if (count != sizeof(struct efi_variable))
@@ -606,7 +605,7 @@ efivar_show_raw(struct efivar_entry *entry, char *buf)
 	if (!entry || !buf)
 		return 0;
 
-	status = get_var_data(entry->efivars, var);
+	status = get_var_data(__efivars, var);
 	if (status != EFI_SUCCESS)
 		return -EIO;
 
@@ -728,7 +727,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 		const char __user *userbuf, size_t count, loff_t *ppos)
 {
 	struct efivar_entry *var = file->private_data;
-	struct efivars *efivars;
+	struct efivars *efivars = __efivars;
 	efi_status_t status;
 	void *data;
 	u32 attributes;
@@ -746,8 +745,6 @@ static ssize_t efivarfs_file_write(struct file *file,
 	if (attributes & ~(EFI_VARIABLE_MASK))
 		return -EINVAL;
 
-	efivars = var->efivars;
-
 	/*
 	 * Ensure that the user can't allocate arbitrarily large
 	 * amounts of memory. Pick a default size of 64K if
@@ -855,7 +852,7 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
 		size_t count, loff_t *ppos)
 {
 	struct efivar_entry *var = file->private_data;
-	struct efivars *efivars = var->efivars;
+	struct efivars *efivars = __efivars;
 	efi_status_t status;
 	unsigned long datasize = 0;
 	u32 attributes;
@@ -1009,7 +1006,7 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
 			  umode_t mode, bool excl)
 {
 	struct inode *inode;
-	struct efivars *efivars = &__efivars;
+	struct efivars *efivars = __efivars;
 	struct efivar_entry *var;
 	int namelen, i = 0, err = 0;
 
@@ -1038,7 +1035,6 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
 	var->var.VariableName[i] = '\0';
 
 	inode->i_private = var;
-	var->efivars = efivars;
 	var->kobj.kset = efivars->kset;
 
 	err = kobject_init_and_add(&var->kobj, &efivar_ktype, NULL, "%s",
@@ -1063,7 +1059,7 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct efivar_entry *var = dentry->d_inode->i_private;
-	struct efivars *efivars = var->efivars;
+	struct efivars *efivars = __efivars;
 	efi_status_t status;
 
 	spin_lock_irq(&efivars->lock);
@@ -1175,7 +1171,7 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
 	struct inode *inode = NULL;
 	struct dentry *root;
 	struct efivar_entry *entry, *n;
-	struct efivars *efivars = &__efivars;
+	struct efivars *efivars = __efivars;
 	char *name;
 	int err = -ENOMEM;
 
@@ -1302,7 +1298,7 @@ static const struct inode_operations efivarfs_dir_inode_operations = {
 
 static int efi_pstore_open(struct pstore_info *psi)
 {
-	struct efivars *efivars = psi->data;
+	struct efivars *efivars = __efivars;
 
 	spin_lock_irq(&efivars->lock);
 	efivars->walk_entry = list_first_entry(&efivars->list,
@@ -1312,7 +1308,7 @@ static int efi_pstore_open(struct pstore_info *psi)
 
 static int efi_pstore_close(struct pstore_info *psi)
 {
-	struct efivars *efivars = psi->data;
+	struct efivars *efivars = __efivars;
 
 	spin_unlock_irq(&efivars->lock);
 	return 0;
@@ -1323,7 +1319,7 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
 			       char **buf, struct pstore_info *psi)
 {
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
-	struct efivars *efivars = psi->data;
+	struct efivars *efivars = __efivars;
 	char name[DUMP_NAME_LEN];
 	int i;
 	int cnt;
@@ -1386,7 +1382,7 @@ static int efi_pstore_write(enum pstore_type_id type,
 	char name[DUMP_NAME_LEN];
 	efi_char16_t efi_name[DUMP_NAME_LEN];
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
-	struct efivars *efivars = psi->data;
+	struct efivars *efivars = __efivars;
 	int i, ret = 0;
 	efi_status_t status = EFI_NOT_FOUND;
 	unsigned long flags;
@@ -1443,7 +1439,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 	char name_old[DUMP_NAME_LEN];
 	efi_char16_t efi_name_old[DUMP_NAME_LEN];
 	efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
-	struct efivars *efivars = psi->data;
+	struct efivars *efivars = __efivars;
 	struct efivar_entry *entry, *found = NULL;
 	int i;
 
@@ -1535,7 +1531,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 			     char *buf, loff_t pos, size_t count)
 {
 	struct efi_variable *new_var = (struct efi_variable *)buf;
-	struct efivars *efivars = bin_attr->private;
+	struct efivars *efivars = __efivars;
 	struct efivar_entry *search_efivar, *n;
 	unsigned long strsize1, strsize2;
 	efi_status_t status = EFI_NOT_FOUND;
@@ -1612,7 +1608,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 			     char *buf, loff_t pos, size_t count)
 {
 	struct efi_variable *del_var = (struct efi_variable *)buf;
-	struct efivars *efivars = bin_attr->private;
+	struct efivars *efivars = __efivars;
 	struct efivar_entry *search_efivar, *n;
 	unsigned long strsize1, strsize2;
 	efi_status_t status = EFI_NOT_FOUND;
@@ -1670,7 +1666,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
 {
 	struct efivar_entry *entry, *n;
-	struct efivars *efivars = &__efivars;
+	struct efivars *efivars = __efivars;
 	unsigned long strsize1, strsize2;
 	bool found = false;
 
@@ -1716,7 +1712,7 @@ static unsigned long var_name_strnsize(efi_char16_t *variable_name,
 
 static void efivar_update_sysfs_entries(struct work_struct *work)
 {
-	struct efivars *efivars = &__efivars;
+	struct efivars *efivars = __efivars;
 	efi_guid_t vendor;
 	efi_char16_t *variable_name;
 	unsigned long variable_name_size = 1024;
@@ -1843,7 +1839,6 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 		return 1;
 	}
 
-	new_efivar->efivars = efivars;
 	memcpy(new_efivar->var.VariableName, variable_name,
 		variable_name_size);
 	memcpy(&(new_efivar->var.VendorGuid), vendor_guid, sizeof(efi_guid_t));
@@ -1942,6 +1937,8 @@ void unregister_efivars(struct efivars *efivars)
 {
 	struct efivar_entry *entry, *n;
 
+	__efivars = NULL;
+
 	list_for_each_entry_safe(entry, n, &efivars->list, list) {
 		spin_lock_irq(&efivars->lock);
 		list_del(&entry->list);
@@ -1998,6 +1995,8 @@ int register_efivars(struct efivars *efivars,
 	unsigned long variable_name_size = 1024;
 	int error = 0;
 
+	__efivars = efivars;
+
 	variable_name = kzalloc(variable_name_size, GFP_KERNEL);
 	if (!variable_name) {
 		printk(KERN_ERR "efivars: Memory allocation failed.\n");
@@ -2085,6 +2084,24 @@ int register_efivars(struct efivars *efivars,
 }
 EXPORT_SYMBOL_GPL(register_efivars);
 
+static struct efivars generic_efivars;
+static struct efivar_operations generic_ops;
+
+static int generic_ops_register(void)
+{
+	generic_ops.get_variable = efi.get_variable;
+	generic_ops.set_variable = efi.set_variable;
+	generic_ops.get_next_variable = efi.get_next_variable;
+	generic_ops.query_variable_info = efi.query_variable_info;
+
+	return register_efivars(&generic_efivars, &generic_ops, efi_kobj);
+}
+
+static void generic_ops_unregister(void)
+{
+	unregister_efivars(&generic_efivars);
+}
+
 /*
  * For now we register the efi subsystem with the firmware subsystem
  * and the vars subsystem with the efi subsystem.  In the future, it
@@ -2111,12 +2128,7 @@ efivars_init(void)
 		return -ENOMEM;
 	}
 
-	ops.get_variable = efi.get_variable;
-	ops.set_variable = efi.set_variable;
-	ops.get_next_variable = efi.get_next_variable;
-	ops.query_variable_info = efi.query_variable_info;
-
-	error = register_efivars(&__efivars, &ops, efi_kobj);
+	error = generic_ops_register();
 	if (error)
 		goto err_put;
 
@@ -2132,7 +2144,7 @@ efivars_init(void)
 	return 0;
 
 err_unregister:
-	unregister_efivars(&__efivars);
+	generic_ops_unregister();
 err_put:
 	kobject_put(efi_kobj);
 	return error;
@@ -2144,7 +2156,7 @@ efivars_exit(void)
 	cancel_work_sync(&efivar_work);
 
 	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
-		unregister_efivars(&__efivars);
+		generic_ops_unregister();
 		kobject_put(efi_kobj);
 	}
 }