Re: [PATCH 3/3] efi: Make efi virtual runtime map passing more robust

From: Matt Fleming
Date: Tue Dec 17 2013 - 07:10:35 EST


On Tue, 17 Dec, at 12:36:37AM, Borislav Petkov wrote:
> From: Borislav Petkov <bp@xxxxxxx>
>
> Currently, running SetVirtualAddressMap() and passing the physical
> address of the virtual map array was working only by a lucky coincidence
> because the memory was present in the EFI page table too. Until Toshi
> went and booted this on a big HP box - the krealloc() manner of resizing
> the memmap we're doing did allocate from such physical addresses which
> were not mapped anymore and boom:
>
> http://lkml.kernel.org/r/1386806463.1791.295.camel@xxxxxxxxxxxxxxxx
>
> One way to take care of that issue is to reimplement the krealloc thing
> but with pages. We start with contiguous pages of order 1, i.e. 2 pages,
> and when we deplete that memory (shouldn't happen all that often but you
> know firmware) we realloc the next power-of-two pages.
>
> Having the pages, it is much more handy and easy to map them into the
> EFI page table with the already existing mapping code which we're using
> for building the virtual mappings.
>
> And, it doesn't matter all that much how much pages we've used as we're
> freeing them right after they've fulfilled their purpose at the end of
> the function anyway.
>
> Reported-by: Toshi Kani <toshi.kani@xxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> ---
> arch/x86/platform/efi/efi.c | 57 ++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 48 insertions(+), 9 deletions(-)

[...]

> @@ -794,12 +814,13 @@ void __init old_map_region(efi_memory_desc_t *md)
> */
> void __init efi_enter_virtual_mode(void)
> {
> + pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
> + unsigned long size, new_memmap_left = 0;
> efi_memory_desc_t *md, *prev_md = NULL;
> + int count = 0, new_memmap_shift = 0;
> void *p, *new_memmap = NULL;
> - unsigned long size;
> efi_status_t status;
> u64 end, systab;
> - int count = 0;
>
> efi.systab = NULL;

You sunk my i386 battleship,

/home/build/git/efi/arch/x86/platform/efi/efi.c:824:24: error: âstruct real_mode_headerâ has no member named âtrampoline_pgdâ
make[4]: *** [arch/x86/platform/efi/efi.o] Error 1
make[3]: *** [arch/x86/platform/efi] Error 2

--
Matt Fleming, Intel Open Source Technology Center
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