[PATCH AUTOSEL 6.1 1/3] efivarfs: expose used and total size
From: Sasha Levin
Date: Sun Jul 23 2023 - 21:36:19 EST
From: Anisse Astier <an.astier@xxxxxxxxxx>
[ Upstream commit d86ff3333cb1d5f42d8898fb5fdb304e143c0237 ]
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@xxxxxxxxxx>
[ardb: - rename efi_reserved_space() to efivar_reserved_space()
- whitespace/coding style tweaks]
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/x86/platform/efi/quirks.c | 8 +++++++
drivers/firmware/efi/efi.c | 1 +
drivers/firmware/efi/vars.c | 12 +++++++++++
fs/efivarfs/super.c | 39 +++++++++++++++++++++++++++++++++-
include/linux/efi.h | 11 ++++++++++
5 files changed, 70 insertions(+), 1 deletion(-)
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index b0b848d6933af..f0cc00032751d 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/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
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index b43e5e6ddaf6e..db3c0ce08e441 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -190,6 +190,7 @@ 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;
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 0ba9f18312f5b..de36d4e4bd95c 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -241,3 +241,15 @@ 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);
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 6780fc81cc11f..0994446a35442 100644
--- a/fs/efivarfs/super.c
+++ b/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,
};
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 4e1bfee9675d2..b8cd4db7a1bfc 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1045,6 +1045,7 @@ 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 {
@@ -1053,6 +1054,12 @@ 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
@@ -1087,6 +1094,10 @@ 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);
--
2.39.2