EFI updates for v6.5

Although some more stuff is brewing, the EFI changes that are ready for
 mainline are few, so not a lot to pull this cycle:
 
 - improve the PCI DMA paranoia logic in the EFI stub
 - some constification changes
 - add statfs support to efivarfs
 - allow user space to enumerate updatable firmware resources without
   CAP_SYS_ADMIN
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Merge tag 'efi-next-for-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi

Pull EFI updates from Ard Biesheuvel:
 "Although some more stuff is brewing, the EFI changes that are ready
  for mainline are few this cycle:

   - improve the PCI DMA paranoia logic in the EFI stub

   - some constification changes

   - add statfs support to efivarfs

   - allow user space to enumerate updatable firmware resources without
     CAP_SYS_ADMIN"

* tag 'efi-next-for-v6.5' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
  efi/libstub: Disable PCI DMA before grabbing the EFI memory map
  efi/esrt: Allow ESRT access without CAP_SYS_ADMIN
  efivarfs: expose used and total size
  efi: make kobj_type structure constant
  efi: x86: make kobj_type structure constant

arch/x86/platform/efi/quirks.c

@@ -114,6 +114,14 @@ void efi_delete_dummy_variable(void)
 				     EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL);
 }
 
+u64 efivar_reserved_space(void)
+{
+	if (efi_no_storage_paranoia)
+		return 0;
+	return EFI_MIN_RESERVE;
+}
+EXPORT_SYMBOL_GPL(efivar_reserved_space);
+
 /*
  * In the nonblocking case we do not attempt to perform garbage
  * collection if we do not have enough free space. Rather, we do the

arch/x86/platform/efi/runtime-map.c

@@ -93,7 +93,7 @@ static void map_release(struct kobject *kobj)
 	kfree(entry);
 }
 
-static struct kobj_type __refdata map_ktype = {
+static const struct kobj_type __refconst map_ktype = {
 	.sysfs_ops	= &map_attr_ops,
 	.default_groups	= def_groups,
 	.release	= map_release,

drivers/firmware/efi/efi.c

@@ -214,6 +214,7 @@ static int generic_ops_register(void)
 	generic_ops.get_variable = efi.get_variable;
 	generic_ops.get_next_variable = efi.get_next_variable;
 	generic_ops.query_variable_store = efi_query_variable_store;
+	generic_ops.query_variable_info = efi.query_variable_info;
 
 	if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE)) {
 		generic_ops.set_variable = efi.set_variable;

drivers/firmware/efi/esrt.c

@@ -95,10 +95,6 @@ static ssize_t esre_attr_show(struct kobject *kobj,
 	struct esre_entry *entry = to_entry(kobj);
 	struct esre_attribute *attr = to_attr(_attr);
 
-	/* Don't tell normal users what firmware versions we've got... */
-	if (!capable(CAP_SYS_ADMIN))
-		return -EACCES;
-
 	return attr->show(entry, buf);
 }
 
@@ -156,7 +152,7 @@ static void esre_release(struct kobject *kobj)
 	kfree(entry);
 }
 
-static struct kobj_type esre1_ktype = {
+static const struct kobj_type esre1_ktype = {
 	.release = esre_release,
 	.sysfs_ops = &esre_attr_ops,
 	.default_groups = esre1_groups,

drivers/firmware/efi/libstub/efi-stub-helper.c

@@ -378,6 +378,9 @@ efi_status_t efi_exit_boot_services(void *handle, void *priv,
 	struct efi_boot_memmap *map;
 	efi_status_t status;
 
+	if (efi_disable_pci_dma)
+		efi_pci_disable_bridge_busmaster();
+
 	status = efi_get_memory_map(&map, true);
 	if (status != EFI_SUCCESS)
 		return status;
@@ -388,9 +391,6 @@ efi_status_t efi_exit_boot_services(void *handle, void *priv,
 		return status;
 	}
 
-	if (efi_disable_pci_dma)
-		efi_pci_disable_bridge_busmaster();
-
 	status = efi_bs_call(exit_boot_services, handle, map->map_key);
 
 	if (status == EFI_INVALID_PARAMETER) {

drivers/firmware/efi/vars.c

@@ -245,3 +245,15 @@ efi_status_t efivar_set_variable(efi_char16_t *name, efi_guid_t *vendor,
 	return status;
 }
 EXPORT_SYMBOL_NS_GPL(efivar_set_variable, EFIVAR);
+
+efi_status_t efivar_query_variable_info(u32 attr,
+					u64 *storage_space,
+					u64 *remaining_space,
+					u64 *max_variable_size)
+{
+	if (!__efivars->ops->query_variable_info)
+		return EFI_UNSUPPORTED;
+	return __efivars->ops->query_variable_info(attr, storage_space,
+			remaining_space, max_variable_size);
+}
+EXPORT_SYMBOL_NS_GPL(efivar_query_variable_info, EFIVAR);

fs/efivarfs/super.c

@@ -13,6 +13,7 @@
 #include <linux/ucs2_string.h>
 #include <linux/slab.h>
 #include <linux/magic.h>
+#include <linux/statfs.h>
 
 #include "internal.h"
 
@@ -23,8 +24,44 @@ static void efivarfs_evict_inode(struct inode *inode)
 	clear_inode(inode);
 }
 
+static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
+			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
+			 EFI_VARIABLE_RUNTIME_ACCESS;
+	u64 storage_space, remaining_space, max_variable_size;
+	efi_status_t status;
+
+	status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
+					    &max_variable_size);
+	if (status != EFI_SUCCESS)
+		return efi_status_to_err(status);
+
+	/*
+	 * This is not a normal filesystem, so no point in pretending it has a block
+	 * size; we declare f_bsize to 1, so that we can then report the exact value
+	 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
+	 */
+	buf->f_bsize	= 1;
+	buf->f_namelen	= NAME_MAX;
+	buf->f_blocks	= storage_space;
+	buf->f_bfree	= remaining_space;
+	buf->f_type	= dentry->d_sb->s_magic;
+
+	/*
+	 * In f_bavail we declare the free space that the kernel will allow writing
+	 * when the storage_paranoia x86 quirk is active. To use more, users
+	 * should boot the kernel with efi_no_storage_paranoia.
+	 */
+	if (remaining_space > efivar_reserved_space())
+		buf->f_bavail = remaining_space - efivar_reserved_space();
+	else
+		buf->f_bavail = 0;
+
+	return 0;
+}
 static const struct super_operations efivarfs_ops = {
-	.statfs = simple_statfs,
+	.statfs = efivarfs_statfs,
 	.drop_inode = generic_delete_inode,
 	.evict_inode = efivarfs_evict_inode,
 };

include/linux/efi.h

@@ -1056,6 +1056,7 @@ struct efivar_operations {
 	efi_set_variable_t *set_variable;
 	efi_set_variable_t *set_variable_nonblocking;
 	efi_query_variable_store_t *query_variable_store;
+	efi_query_variable_info_t *query_variable_info;
 };
 
 struct efivars {
@@ -1063,6 +1064,12 @@ struct efivars {
 	const struct efivar_operations *ops;
 };
 
+#ifdef CONFIG_X86
+u64 __attribute_const__ efivar_reserved_space(void);
+#else
+static inline u64 efivar_reserved_space(void) { return 0; }
+#endif
+
 /*
  * The maximum size of VariableName + Data = 1024
  * Therefore, it's reasonable to save that much
@@ -1101,6 +1108,10 @@ efi_status_t efivar_set_variable_locked(efi_char16_t *name, efi_guid_t *vendor,
 efi_status_t efivar_set_variable(efi_char16_t *name, efi_guid_t *vendor,
 				 u32 attr, unsigned long data_size, void *data);
 
+efi_status_t efivar_query_variable_info(u32 attr, u64 *storage_space,
+					u64 *remaining_space,
+					u64 *max_variable_size);
+
 #if IS_ENABLED(CONFIG_EFI_CAPSULE_LOADER)
 extern bool efi_capsule_pending(int *reset_type);