Re: [PATCH 4/4] x86, efi: Map runtime services 1:1

["H. Peter Anvin" <hpa@zytor.com>]

On 06/06/2013 08:58 AM, Borislav Petkov wrote:
> --
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 654be4ae3047..7a6129afdff1 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1021,6 +1021,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code)
>  	/* Get the faulting address: */
>  	address = read_cr2();
>  
> +	if (read_cr3() == (unsigned long)real_mode_header->trampoline_pgd)
> +		pr_err("%s: #PF addr: 0x%lx\n", __func__, address);
> +
>  	/*
>  	 * Detect and handle instructions that would cause a page fault for
>  	 * both a tracked kernel page and a userspace page.
> 

Or we could materialize mappings for this specific PGD.  However, adding
a read of %cr3 in __do_page_fault sounds expensive.

	-hpa