efi: Export more EFI table variables to sysfs

Export fw_vendor, runtime and config table physical addresses to
/sys/firmware/efi/{fw_vendor,runtime,config_table} because kexec kernels
need them.

From EFI spec these 3 variables will be updated to virtual address after
entering virtual mode. But kernel startup code will need the physical
address.

Signed-off-by: Dave Young <dyoung@redhat.com>
Tested-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 2e2fbdec0845..72533af72b98 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -32,6 +32,9 @@ struct efi __read_mostly efi = {
         .hcdp       = EFI_INVALID_TABLE_ADDR,
         .uga        = EFI_INVALID_TABLE_ADDR,
         .uv_systab  = EFI_INVALID_TABLE_ADDR,
+        .fw_vendor  = EFI_INVALID_TABLE_ADDR,
+        .runtime    = EFI_INVALID_TABLE_ADDR,
+        .config_table  = EFI_INVALID_TABLE_ADDR,
 };
 EXPORT_SYMBOL(efi);
 
@@ -71,13 +74,49 @@ static ssize_t systab_show(struct kobject *kobj,
 static struct kobj_attribute efi_attr_systab =
                         __ATTR(systab, 0400, systab_show, NULL);
 
+#define EFI_FIELD(var) efi.var
+
+#define EFI_ATTR_SHOW(name) \
+static ssize_t name##_show(struct kobject *kobj, \
+                                struct kobj_attribute *attr, char *buf) \
+{ \
+        return sprintf(buf, "0x%lx\n", EFI_FIELD(name)); \
+}
+
+EFI_ATTR_SHOW(fw_vendor);
+EFI_ATTR_SHOW(runtime);
+EFI_ATTR_SHOW(config_table);
+
+static struct kobj_attribute efi_attr_fw_vendor = __ATTR_RO(fw_vendor);
+static struct kobj_attribute efi_attr_runtime = __ATTR_RO(runtime);
+static struct kobj_attribute efi_attr_config_table = __ATTR_RO(config_table);
+
 static struct attribute *efi_subsys_attrs[] = {
         &efi_attr_systab.attr,
-        NULL,   /* maybe more in the future? */
+        &efi_attr_fw_vendor.attr,
+        &efi_attr_runtime.attr,
+        &efi_attr_config_table.attr,
+        NULL,
 };
 
+static umode_t efi_attr_is_visible(struct kobject *kobj,
+                                   struct attribute *attr, int n)
+{
+        umode_t mode = attr->mode;
+
+        if (attr == &efi_attr_fw_vendor.attr)
+                return (efi.fw_vendor == EFI_INVALID_TABLE_ADDR) ? 0 : mode;
+        else if (attr == &efi_attr_runtime.attr)
+                return (efi.runtime == EFI_INVALID_TABLE_ADDR) ? 0 : mode;
+        else if (attr == &efi_attr_config_table.attr)
+                return (efi.config_table == EFI_INVALID_TABLE_ADDR) ? 0 : mode;
+
+        return mode;
+}
+
 static struct attribute_group efi_subsys_attr_group = {
         .attrs = efi_subsys_attrs,
+        .is_visible = efi_attr_is_visible,
 };
 
 static struct efivars generic_efivars;