efi: Add support for using efivars as a pstore backend

EFI provides an area of nonvolatile storage managed by the firmware. We
can use this as a pstore backend to maintain copies of oopses, aiding
diagnosis.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 189 insertions, 2 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 5f29aafd446..2bbb22670d2 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -78,6 +78,7 @@
 #include <linux/kobject.h>
 #include <linux/device.h>
 #include <linux/slab.h>
+#include <linux/pstore.h>
 
 #include <asm/uaccess.h>
 
@@ -89,6 +90,8 @@ MODULE_DESCRIPTION("sysfs interface to EFI Variables");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(EFIVARS_VERSION);
 
+#define DUMP_NAME_LEN 52
+
 /*
  * The maximum size of VariableName + Data = 1024
  * Therefore, it's reasonable to save that much
@@ -161,18 +164,28 @@ utf8_strsize(efi_char16_t *data, unsigned long maxlength)
 }
 
 static efi_status_t
-get_var_data(struct efivars *efivars, struct efi_variable *var)
+get_var_data_locked(struct efivars *efivars, struct efi_variable *var)
 {
         efi_status_t status;
 
-        spin_lock(&efivars->lock);
         var->DataSize = 1024;
         status = efivars->ops->get_variable(var->VariableName,
                                             &var->VendorGuid,
                                             &var->Attributes,
                                             &var->DataSize,
                                             var->Data);
+        return status;
+}
+
+static efi_status_t
+get_var_data(struct efivars *efivars, struct efi_variable *var)
+{
+        efi_status_t status;
+
+        spin_lock(&efivars->lock);
+        status = get_var_data_locked(efivars, var);
         spin_unlock(&efivars->lock);
+
         if (status != EFI_SUCCESS) {
                 printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
                         status);
@@ -387,12 +400,176 @@ static struct kobj_type efivar_ktype = {
         .default_attrs = def_attrs,
 };
 
+static struct pstore_info efi_pstore_info;
+
 static inline void
 efivar_unregister(struct efivar_entry *var)
 {
         kobject_put(&var->kobj);
 }
 
+#ifdef CONFIG_PSTORE
+
+static int efi_pstore_open(struct pstore_info *psi)
+{
+        struct efivars *efivars = psi->data;
+
+        spin_lock(&efivars->lock);
+        efivars->walk_entry = list_first_entry(&efivars->list,
+                                               struct efivar_entry, list);
+        return 0;
+}
+
+static int efi_pstore_close(struct pstore_info *psi)
+{
+        struct efivars *efivars = psi->data;
+
+        spin_unlock(&efivars->lock);
+        return 0;
+}
+
+static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
+                               struct timespec *timespec, struct pstore_info *psi)
+{
+        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
+        struct efivars *efivars = psi->data;
+        char name[DUMP_NAME_LEN];
+        int i;
+        unsigned int part, size;
+        unsigned long time;
+
+        while (&efivars->walk_entry->list != &efivars->list) {
+                if (!efi_guidcmp(efivars->walk_entry->var.VendorGuid,
+                                 vendor)) {
+                        for (i = 0; i < DUMP_NAME_LEN; i++) {
+                                name[i] = efivars->walk_entry->var.VariableName[i];
+                        }
+                        if (sscanf(name, "dump-type%u-%u-%lu", type, &part, &time) == 3) {
+                                *id = part;
+                                timespec->tv_sec = time;
+                                timespec->tv_nsec = 0;
+                                get_var_data_locked(efivars, &efivars->walk_entry->var);
+                                size = efivars->walk_entry->var.DataSize;
+                                memcpy(psi->buf, efivars->walk_entry->var.Data, size);
+                                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
+                                                   struct efivar_entry, list);
+                                return size;
+                        }
+                }
+                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
+                                                 struct efivar_entry, list);
+        }
+        return 0;
+}
+
+static u64 efi_pstore_write(enum pstore_type_id type, unsigned int part,
+                            size_t size, struct pstore_info *psi)
+{
+        char name[DUMP_NAME_LEN];
+        char stub_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 efivar_entry *entry, *found = NULL;
+        int i;
+
+        sprintf(stub_name, "dump-type%u-%u-", type, part);
+        sprintf(name, "%s%lu", stub_name, get_seconds());
+
+        spin_lock(&efivars->lock);
+
+        for (i = 0; i < DUMP_NAME_LEN; i++)
+                efi_name[i] = stub_name[i];
+
+        /*
+         * Clean up any entries with the same name
+         */
+
+        list_for_each_entry(entry, &efivars->list, list) {
+                get_var_data_locked(efivars, &entry->var);
+
+                for (i = 0; i < DUMP_NAME_LEN; i++) {
+                        if (efi_name[i] == 0) {
+                                found = entry;
+                                efivars->ops->set_variable(entry->var.VariableName,
+                                                           &entry->var.VendorGuid,
+                                                           EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                                                           0, NULL);
+                                break;
+                        } else if (efi_name[i] != entry->var.VariableName[i]) {
+                                break;
+                        }
+                }
+        }
+
+        if (found)
+                list_del(&found->list);
+
+        for (i = 0; i < DUMP_NAME_LEN; i++)
+                efi_name[i] = name[i];
+
+        efivars->ops->set_variable(efi_name, &vendor,
+                                   EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
+                                   size, psi->buf);
+
+        spin_unlock(&efivars->lock);
+
+        if (found)
+                efivar_unregister(found);
+
+        if (size)
+                efivar_create_sysfs_entry(efivars, utf8_strsize(efi_name, DUMP_NAME_LEN * 2),
+                                          efi_name, &vendor);
+
+        return part;
+};
+
+static int efi_pstore_erase(enum pstore_type_id type, u64 id,
+                            struct pstore_info *psi)
+{
+        efi_pstore_write(type, id, 0, psi);
+
+        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,
+                               struct timespec *time, struct pstore_info *psi)
+{
+        return -1;
+}
+
+static u64 efi_pstore_write(enum pstore_type_id type, int part, size_t size,
+                            struct pstore_info *psi)
+{
+        return 0;
+}
+
+static int efi_pstore_erase(enum pstore_type_id type, u64 id,
+                            struct pstore_info *psi)
+{
+        return 0;
+}
+#endif
+
+static struct pstore_info efi_pstore_info = {
+        .owner          = THIS_MODULE,
+        .name           = "efi",
+        .open           = efi_pstore_open,
+        .close          = efi_pstore_close,
+        .read           = efi_pstore_read,
+        .write          = efi_pstore_write,
+        .erase          = efi_pstore_erase,
+};
 
 static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
                              struct bin_attribute *bin_attr,
@@ -763,6 +940,16 @@ 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;
+                mutex_init(&efivars->efi_pstore_info.buf_mutex);
+                pstore_register(&efivars->efi_pstore_info);
+        }
+
 out:
         kfree(variable_name);