From: Matt Fleming <matt.fleming@xxxxxxxxx> Some firmware appears to enable interrupts during boot service calls, even if we've explicitly disabled them prior to the call. This is actually allowed per the UEFI spec because boottime services expect to be called with interrupts enabled. So that's fine, we just need to ensure that we disable them again in efi_enter32() before switching to a 64-bit GDT, otherwise an interrupt may fire causing a 32-bit IRQ handler to run after we've left compatibility mode. Despite efi_enter32() being called both for boottime and runtime services, this really only affects boottime because the runtime services callchain is executed with interrupts disabled. See efi_thunk(). Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx> --- arch/x86/platform/efi/efi_stub_64.S | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S index e811514beeac..65b787a9fc4e 100644 --- a/arch/x86/platform/efi/efi_stub_64.S +++ b/arch/x86/platform/efi/efi_stub_64.S @@ -261,6 +261,12 @@ ENTRY(efi_enter32) /* We must preserve return value */ movl %eax, %edi + /* + * Some firmware will return with interrupts enabled. Be sure to + * disable them before we switch GDTs. + */ + cli + movl 44(%esp), %eax movl %eax, 2(%eax) lgdtl (%eax) -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
