[PATCH] efi/libstub: arm: omit sorting of the UEFI memory map

[Russell King - ARM Linux]

On Fri, Oct 27, 2017 at 05:12:58PM +0200, Matthias Brugger wrote:
> Hi Ard,
> 
> On 10/22/2017 04:14 PM, Ard Biesheuvel wrote:
> > ARM shares its EFI stub implementation with arm64, which has some
> > special handling in the virtual remapping code to
> > a) make sure that we can map everything even if the OS executes
> >    with 64k page size, and
> > b) make sure that adjacent regions with the same attributes are not
> >    reordered or moved apart in memory.
> > 
> > The latter is a workaround for a 'feature' that was shortly recommended
> > by UEFI spec v2.5, but deprecated shortly after, due to the fact that
> > it broke many OS installers, including non-Linux ones, and it was never
> > widely implemented for ARM systems. Before implementing b), the arm64
> > code simply rounded up all regions to 64 KB granularity, but given that
> > that results in moving adjacent regions apart, it had to be refined when
> > b) was implemented.
> > 
> > The adjacency check requires a sort() pass, due to the fact that the
> > UEFI spec does not mandate any ordering, and the inclusion of the
> > lib/sort.c code into the ARM EFI stub is causing some trouble with
> > the decompressor build due to the fact that its EXPORT_SYMBOL() call
> > triggers the creation of ksymtab/kcrctab sections.
> > 
> > So let's simply do away with the adjacency check for ARM, and simply put
> > all UEFI runtime regions together if they have the same memory attributes.
> > This is guaranteed to work, given that ARM only supports 4 KB pages,
> > and allows us to remove the sort() call entirely.
> > 
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> > ---
> >  drivers/firmware/efi/libstub/Makefile   | 6 +++---
> >  drivers/firmware/efi/libstub/arm-stub.c | 7 +++++--
> >  2 files changed, 8 insertions(+), 5 deletions(-)
> > 
> 
> I thought I already provided my tag, but just in case:
> This fixes the boot problems I had on the bananapi-r2.
> 
> Tested-by: Matthias Brugger <matthias.bgg at gmail.com>

Please test my "fixes" branch - that has all three patches merged.

We don't have linux-next running at the moment, so folk need to be
manually fetching the appropriate git trees for testing.

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