efi_loader: Add OS notifications for SetVariable at runtime

Previous patches enable SetVariable at runtime using a volatile storage
backend using EFI_RUNTIME_SERVICES_DATA allocared memory. Since there's
no recommendation from the spec on how to notify the OS, add a volatile
EFI variable that contains the filename relative to the ESP. OS'es
can use that file and update it at runtime

$~ efivar -p -n b2ac5fc9-92b7-4acd-aeac-11e818c3130c-RTStorageVolatile
GUID: b2ac5fc9-92b7-4acd-aeac-11e818c3130c
Name: "RTStorageVolatile"
Attributes:
	Boot Service Access
	Runtime Service Access
Value:
00000000  75 62 6f 6f 74 65 66 69  2e 76 61 72 00           |ubootefi.var.   |

Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

diff --git a/include/efi_loader.h b/include/efi_loader.h
index bb51c028177495b5fed3fed7bc636e8ee8642ca3..69442f4e58de8c0c4d4fe4a1fc186773e7f68535 100644 (file)
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -159,6 +159,10 @@ static inline void efi_set_bootdev(const char *dev, const char *devnr,
 #define EFICONFIG_AUTO_GENERATED_ENTRY_GUID \
        EFI_GUID(0x8108ac4e, 0x9f11, 0x4d59, \
                 0x85, 0x0e, 0xe2, 0x1a, 0x52, 0x2c, 0x59, 0xb2)
+#define U_BOOT_EFI_RT_VAR_FILE_GUID \
+       EFI_GUID(0xb2ac5fc9, 0x92b7, 0x4acd, \
+                0xae, 0xac, 0x11, 0xe8, 0x18, 0xc3, 0x13, 0x0c)
+
 
 /* Use internal device tree when starting UEFI application */
 #define EFI_FDT_USE_INTERNAL NULL

diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
index dde083b09665652503bdeac7b4369bd383527cd9..c8f7a88ba8dbaba256df64d867868a6a47ea6943 100644 (file)
--- a/lib/efi_loader/efi_runtime.c
+++ b/lib/efi_loader/efi_runtime.c
@@ -10,6 +10,7 @@
 #include <dm.h>
 #include <elf.h>
 #include <efi_loader.h>
+#include <efi_variable.h>
 #include <log.h>
 #include <malloc.h>
 #include <rtc.h>
@@ -110,6 +111,7 @@ static __efi_runtime_data efi_uintn_t efi_descriptor_size;
  */
 efi_status_t efi_init_runtime_supported(void)
 {
+       const efi_guid_t efi_guid_efi_rt_var_file = U_BOOT_EFI_RT_VAR_FILE_GUID;
        efi_status_t ret;
        struct efi_rt_properties_table *rt_table;
 
@@ -127,9 +129,20 @@ efi_status_t efi_init_runtime_supported(void)
                                EFI_RT_SUPPORTED_SET_VIRTUAL_ADDRESS_MAP |
                                EFI_RT_SUPPORTED_CONVERT_POINTER;
 
-       if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE))
-               rt_table->runtime_services_supported |=
-                       EFI_RT_SUPPORTED_SET_VARIABLE;
+       if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) {
+               ret = efi_set_variable_int(u"RTStorageVolatile",
+                                          &efi_guid_efi_rt_var_file,
+                                          EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                                          EFI_VARIABLE_RUNTIME_ACCESS |
+                                          EFI_VARIABLE_READ_ONLY,
+                                          sizeof(EFI_VAR_FILE_NAME),
+                                          EFI_VAR_FILE_NAME, false);
+               if (ret != EFI_SUCCESS) {
+                       log_err("Failed to set RTStorageVolatile\n");
+                       return ret;
+               }
+               rt_table->runtime_services_supported |= EFI_RT_SUPPORTED_SET_VARIABLE;
+       }
 
        /*
         * This value must be synced with efi_runtime_detach_list