efi: pstore: disentangle from deprecated efivars module

The EFI pstore implementation relies on the 'efivars' abstraction,
which encapsulates the EFI variable store in a way that can be
overridden by other backing stores, like the Google SMI one.

On top of that, the EFI pstore implementation also relies on the
efivars.ko module, which is a separate layer built on top of the
'efivars' abstraction that exposes the [deprecated] sysfs entries
for each variable that exists in the backing store.

Since the efivars.ko module is deprecated, and all users appear to
have moved to the efivarfs file system instead, let's prepare for
its removal, by removing EFI pstore's dependency on it.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: ardbiesheuvel

drivers/firmware/efi/Kconfig

@@ -26,7 +26,7 @@ config EFI_ESRT
 
 config EFI_VARS_PSTORE
 	tristate "Register efivars backend for pstore"
-	depends on EFI_VARS && PSTORE
+	depends on PSTORE
 	default y
 	help
 	  Say Y here to enable use efivars as a backend to pstore. This

drivers/firmware/efi/efi-pstore.c

@@ -8,6 +8,8 @@
 
 #define DUMP_NAME_LEN 66
 
+#define EFIVARS_DATA_SIZE_MAX 1024
+
 static bool efivars_pstore_disable =
 	IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);
 
@@ -18,6 +20,8 @@ module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
 	 EFI_VARIABLE_BOOTSERVICE_ACCESS | \
 	 EFI_VARIABLE_RUNTIME_ACCESS)
 
+static LIST_HEAD(efi_pstore_list);
+
 static int efi_pstore_open(struct pstore_info *psi)
 {
 	psi->data = NULL;
@@ -126,7 +130,7 @@ static inline int __efi_pstore_scan_sysfs_exit(struct efivar_entry *entry,
 	if (entry->deleting) {
 		list_del(&entry->list);
 		efivar_entry_iter_end();
-		efivar_unregister(entry);
+		kfree(entry);
 		if (efivar_entry_iter_begin())
 			return -EINTR;
 	} else if (turn_off_scanning)
@@ -169,7 +173,7 @@ static int efi_pstore_sysfs_entry_iter(struct pstore_record *record)
 {
 	struct efivar_entry **pos = (struct efivar_entry **)&record->psi->data;
 	struct efivar_entry *entry, *n;
-	struct list_head *head = &efivar_sysfs_list;
+	struct list_head *head = &efi_pstore_list;
 	int size = 0;
 	int ret;
 
@@ -314,12 +318,12 @@ static int efi_pstore_erase_name(const char *name)
 	if (efivar_entry_iter_begin())
 		return -EINTR;
 
-	found = __efivar_entry_iter(efi_pstore_erase_func, &efivar_sysfs_list,
+	found = __efivar_entry_iter(efi_pstore_erase_func, &efi_pstore_list,
 				    efi_name, &entry);
 	efivar_entry_iter_end();
 
 	if (found && !entry->scanning)
-		efivar_unregister(entry);
+		kfree(entry);
 
 	return found ? 0 : -ENOENT;
 }
@@ -354,14 +358,76 @@ static struct pstore_info efi_pstore_info = {
 	.erase		= efi_pstore_erase,
 };
 
+static int efi_pstore_callback(efi_char16_t *name, efi_guid_t vendor,
+			       unsigned long name_size, void *data)
+{
+	struct efivar_entry *entry;
+	int ret;
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	memcpy(entry->var.VariableName, name, name_size);
+	entry->var.VendorGuid = vendor;
+
+	ret = efivar_entry_add(entry, &efi_pstore_list);
+	if (ret)
+		kfree(entry);
+
+	return ret;
+}
+
+static int efi_pstore_update_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, &efi_pstore_list, false))
+		return 0;
+
+	memcpy(entry->var.VariableName, name, name_size);
+	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
+
+	return 1;
+}
+
+static void efi_pstore_update_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(efi_pstore_update_entry, entry,
+				  false, &efi_pstore_list);
+		if (!err)
+			break;
+
+		efivar_entry_add(entry, &efi_pstore_list);
+	}
+
+	kfree(entry);
+}
+
 static __init int efivars_pstore_init(void)
 {
+	int ret;
+
 	if (!efivars_kobject() || !efivar_supports_writes())
 		return 0;
 
 	if (efivars_pstore_disable)
 		return 0;
 
+	ret = efivar_init(efi_pstore_callback, NULL, true, &efi_pstore_list);
+	if (ret)
+		return ret;
+
 	efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
 	if (!efi_pstore_info.buf)
 		return -ENOMEM;
@@ -374,6 +440,8 @@ static __init int efivars_pstore_init(void)
 		efi_pstore_info.bufsize = 0;
 	}
 
+	INIT_WORK(&efivar_work, efi_pstore_update_entries);
+
 	return 0;
 }
 

drivers/firmware/efi/efivars.c

@@ -24,8 +24,7 @@ MODULE_LICENSE("GPL");
 MODULE_VERSION(EFIVARS_VERSION);
 MODULE_ALIAS("platform:efivars");
 
-LIST_HEAD(efivar_sysfs_list);
-EXPORT_SYMBOL_GPL(efivar_sysfs_list);
+static LIST_HEAD(efivar_sysfs_list);
 
 static struct kset *efivars_kset;
 
@@ -591,42 +590,6 @@ create_efivars_bin_attributes(void)
 	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)
 {
@@ -701,8 +664,6 @@ int efivars_sysfs_init(void)
 		return error;
 	}
 
-	INIT_WORK(&efivar_work, efivar_update_sysfs_entries);
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(efivars_sysfs_init);

include/linux/efi.h

@@ -986,8 +986,6 @@ struct efivar_entry {
 	bool deleting;
 };
 
-extern struct list_head efivar_sysfs_list;
-
 static inline void
 efivar_unregister(struct efivar_entry *var)
 {
@@ -1045,8 +1043,6 @@ void efivar_run_worker(void);
 #if defined(CONFIG_EFI_VARS) || defined(CONFIG_EFI_VARS_MODULE)
 int efivars_sysfs_init(void);
 
-#define EFIVARS_DATA_SIZE_MAX 1024
-
 #endif /* CONFIG_EFI_VARS */
 extern bool efi_capsule_pending(int *reset_type);