On Mon, 22 Feb, at 04:56:57PM, Ard Biesheuvel wrote:
> On 22 February 2016 at 16:43, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> > On Mon, Feb 22, 2016 at 03:59:39PM +0100, Ard Biesheuvel wrote:
> >> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> >> index 848ede1587dc..6ce13d6b7122 100644
> >> --- a/drivers/firmware/efi/arm-runtime.c
> >> +++ b/drivers/firmware/efi/arm-runtime.c
> >> @@ -64,6 +64,16 @@ static bool __init efi_virtmap_init(void)
> >> &phys, ret);
> >> return false;
> >> }
> >> + /*
> >> + * If this entry covers the address of the UEFI system table,
> >> + * calculate and record its virtual address.
> >> + */
> >> + if (efi_system_table >= phys &&
> >> + efi_system_table < phys + (md->num_pages * EFI_PAGE_SIZE)) {
> >> + efi.systab = (void *)(efi_system_table - phys +
> >> + md->virt_addr);
> >> + set_bit(EFI_SYSTEM_TABLES, &efi.flags);
> >> + }
> >
> > It seems very odd to me to set this given it's currently unused, and we
> > don't have permanent access to the table. That sounds like we're just
> > setting ourselves up for future fragility as users appear.
> >
>
> I wondered about the purpose as well. It is only ever set, and never
> tested (until this patch)
>
> @Matt: any thoughts?
Good question. EFI_SYSTEM_TABLES was introduced over 4 years ago, but
it looks like it has never had any users. I don't remember why I added
it, probably just be to be "complete" since we had bits for all the
other tables.
If somebody wants to rip it out, I wouldn't object.
To be fair, we don't have permanent access to any of the tables - you
always have to switch to the dedicated EFI page tables before
accessing regions.
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