efi: Check EFI revision in setup_efi_vars [Linux 3.9]

This Linux kernel change "efi: Check EFI revision in setup_efi_vars" is included in the Linux 3.9 release. This change is authored by Josh Boyer <jwboyer [at] redhat.com> on Wed Apr 24 11:16:52 2013 -0400. The commit for this change in Linux stable tree is f697036 (patch).

efi: Check EFI revision in setup_efi_vars

We need to check the runtime sys_table for the EFI version the firmware
specifies instead of just checking for a NULL QueryVariableInfo.  Older
implementations of EFI don't have QueryVariableInfo but the runtime is
a smaller structure, so the pointer to it may be pointing off into garbage.

This is apparently the case with several Apple firmwares that support EFI
1.10, and the current check causes them to no longer boot.  Fix based on
a suggestion from Matthew Garrett.

Signed-off-by: Josh Boyer <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>

There are 2 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/x86/boot/compressed/eboot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 41de115..35ee62f 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -258,7 +258,7 @@ static efi_status_t setup_efi_vars(struct boot_params *params)
    u64 store_size, remaining_size, var_size;
    efi_status_t status;

-   if (!sys_table->runtime->query_variable_info)
+   if (sys_table->runtime->hdr.revision < EFI_2_00_SYSTEM_TABLE_REVISION)
        return EFI_UNSUPPORTED;

    data = (struct setup_data *)(unsigned long)params->hdr.setup_data;

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