efivars: Allow disabling use as a pstore backend

Add a new option, CONFIG_EFI_VARS_PSTORE, which can be set to N to
avoid using efivars as a backend to pstore, as some users may want to
compile out the code completely.

Set the default to Y to maintain backwards compatability, since this
feature has always been enabled until now.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

2 files changed, 29 insertions, 44 deletions

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 9b00072a020f..898023d8e486 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -53,6 +53,15 @@ config EFI_VARS
           Subsequent efibootmgr releases may be found at:
           <http://linux.dell.com/efibootmgr>
 
+config EFI_VARS_PSTORE
+        bool "Register efivars backend for pstore"
+        depends on EFI_VARS && PSTORE
+        default y
+        help
+          Say Y here to enable use efivars as a backend to pstore. This
+          will allow writing console messages, crash dumps, or anything
+          else supported by pstore to EFI variables.
+
 config EFI_PCDP
         bool "Console device selection via EFI PCDP or HCDP table"
         depends on ACPI && EFI && IA64
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index fe62aa392239..37b6f247399e 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -1309,9 +1309,7 @@ static const struct inode_operations efivarfs_dir_inode_operations = {
         .create = efivarfs_create,
 };
 
-static struct pstore_info efi_pstore_info;
-
-#ifdef CONFIG_PSTORE
+#ifdef CONFIG_EFI_VARS_PSTORE
 
 static int efi_pstore_open(struct pstore_info *psi)
 {
@@ -1514,38 +1512,6 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 
         return 0;
 }
-#else
-static int efi_pstore_open(struct pstore_info *psi)
-{
-        return 0;
-}
-
-static int efi_pstore_close(struct pstore_info *psi)
-{
-        return 0;
-}
-
-static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type, int *count,
-                               struct timespec *timespec,
-                               char **buf, struct pstore_info *psi)
-{
-        return -1;
-}
-
-static int efi_pstore_write(enum pstore_type_id type,
-                enum kmsg_dump_reason reason, u64 *id,
-                unsigned int part, int count, size_t size,
-                struct pstore_info *psi)
-{
-        return 0;
-}
-
-static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
-                            struct timespec time, struct pstore_info *psi)
-{
-        return 0;
-}
-#endif
 
 static struct pstore_info efi_pstore_info = {
         .owner          = THIS_MODULE,
@@ -1557,6 +1523,24 @@ static struct pstore_info efi_pstore_info = {
         .erase          = efi_pstore_erase,
 };
 
+static void efivar_pstore_register(struct efivars *efivars)
+{
+        efivars->efi_pstore_info = efi_pstore_info;
+        efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
+        if (efivars->efi_pstore_info.buf) {
+                efivars->efi_pstore_info.bufsize = 1024;
+                efivars->efi_pstore_info.data = efivars;
+                spin_lock_init(&efivars->efi_pstore_info.buf_lock);
+                pstore_register(&efivars->efi_pstore_info);
+        }
+}
+#else
+static void efivar_pstore_register(struct efivars *efivars)
+{
+        return;
+}
+#endif
+
 static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
                              struct bin_attribute *bin_attr,
                              char *buf, loff_t pos, size_t count)
@@ -2025,15 +2009,7 @@ int register_efivars(struct efivars *efivars,
         if (error)
                 unregister_efivars(efivars);
 
-        efivars->efi_pstore_info = efi_pstore_info;
-
-        efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
-        if (efivars->efi_pstore_info.buf) {
-                efivars->efi_pstore_info.bufsize = 1024;
-                efivars->efi_pstore_info.data = efivars;
-                spin_lock_init(&efivars->efi_pstore_info.buf_lock);
-                pstore_register(&efivars->efi_pstore_info);
-        }
+        efivar_pstore_register(efivars);
 
         register_filesystem(&efivarfs_type);