Modify UEFI anti-bricking code

[pandora-kernel.git] / arch / x86 / platform / efi / efi.c

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 07ef7e8..8ea99d8 100644 (file)
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -49,6 +49,13 @@
 #define EFI_DEBUG      1
 #define PFX            "EFI: "
 
+#define EFI_MIN_RESERVE 5120
+
+#define EFI_DUMMY_GUID \
+       EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9)
+
+static efi_char16_t efi_dummy_name[6] = { 'D', 'U', 'M', 'M', 'Y', 0 };
+
 struct efi __read_mostly efi = {
        .mps        = EFI_INVALID_TABLE_ADDR,
        .acpi       = EFI_INVALID_TABLE_ADDR,
@@ -787,6 +794,13 @@ void __init efi_enter_virtual_mode(void)
        early_iounmap(memmap.map, memmap.nr_map * memmap.desc_size);
        memmap.map = NULL;
        kfree(new_memmap);
+
+       /* clean DUMMY object */
+       efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
+                        EFI_VARIABLE_NON_VOLATILE |
+                        EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                        EFI_VARIABLE_RUNTIME_ACCESS,
+                        0, NULL);
 }
 
 /*
@@ -838,22 +852,65 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
        efi_status_t status;
        u64 storage_size, remaining_size, max_size;
 
+       if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
+               return 0;
+
        status = efi.query_variable_info(attributes, &storage_size,
                                         &remaining_size, &max_size);
        if (status != EFI_SUCCESS)
                return status;
 
-       if (!max_size && remaining_size > size)
-               printk_once(KERN_ERR FW_BUG "Broken EFI implementation"
-                           " is returning MaxVariableSize=0\n");
+       /*
+        * Some firmware implementations refuse to boot if there's insufficient
+        * space in the variable store. We account for that by refusing the
+        * write if permitting it would reduce the available space to under
+        * 5KB. This figure was provided by Samsung, so should be safe.
+        */
+       if ((remaining_size - size < EFI_MIN_RESERVE) &&
+               !efi_no_storage_paranoia) {
+
+               /*
+                * Triggering garbage collection may require that the firmware
+                * generate a real EFI_OUT_OF_RESOURCES error. We can force
+                * that by attempting to use more space than is available.
+                */
+               unsigned long dummy_size = remaining_size + 1024;
+               void *dummy = kmalloc(dummy_size, GFP_ATOMIC);
+
+               status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
+                                         EFI_VARIABLE_NON_VOLATILE |
+                                         EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                                         EFI_VARIABLE_RUNTIME_ACCESS,
+                                         dummy_size, dummy);
 
-       if (!storage_size || size > remaining_size ||
-           (max_size && size > max_size))
-               return EFI_OUT_OF_RESOURCES;
+               if (status == EFI_SUCCESS) {
+                       /*
+                        * This should have failed, so if it didn't make sure
+                        * that we delete it...
+                        */
+                       efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
+                                        EFI_VARIABLE_NON_VOLATILE |
+                                        EFI_VARIABLE_BOOTSERVICE_ACCESS |
+                                        EFI_VARIABLE_RUNTIME_ACCESS,
+                                        0, dummy);
+               }
 
-       if (!efi_no_storage_paranoia &&
-           (remaining_size - size) < (storage_size / 2))
-               return EFI_OUT_OF_RESOURCES;
+               /*
+                * The runtime code may now have triggered a garbage collection
+                * run, so check the variable info again
+                */
+               status = efi.query_variable_info(attributes, &storage_size,
+                                                &remaining_size, &max_size);
+
+               if (status != EFI_SUCCESS)
+                       return status;
+
+               /*
+                * There still isn't enough room, so return an error
+                */
+               if (remaining_size - size < EFI_MIN_RESERVE)
+                       return EFI_OUT_OF_RESOURCES;
+       }
 
        return EFI_SUCCESS;
 }