[PATCH v2] efi_loader: Add U-Boot memory to the EFI memory map

[Ilias Apalodimas]

Hi Tom

On Sat, 30 Nov 2024 at 05:42, Tom Rini <trini at konsulko.com> wrote:
>
> On Fri, Nov 29, 2024 at 04:27:40PM -0700, Simon Glass wrote:
> > (Sorry, that was supposed to be sent to Ilias)
> >
> > - Simon
> >
> > On Fri, 29 Nov 2024 at 15:26, Simon Glass <sjg at chromium.org> wrote:
> > >
> > > Hi Sughosh,
> > >
> > > On Fri, 29 Nov 2024 at 10:26, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> > > >
> > > > On Fri, 29 Nov 2024 at 22:38, Ilias Apalodimas
> > > > <ilias.apalodimas at linaro.org> wrote:
> > > > >
> > > > > This reverts commit ("commit a68c9ac5d8af ("efi_memory: do not add U-Boot memory to the memory map")
> > > > > This code was removed when the EFI subsystem started using LMB calls for
> > > > > the reservations. In hindsight it unearthed two problems.
> > > > >
> > > > > The e820 code is adding u-boot memory as EfiReservedMemory while it
> > > > > should look at what LMB added and decide instead of blindly overwriting
> > > > > it. The reason this worked is that we marked that code properly late,
> > > > > when the EFI came up. But now with the LMB changes, the EFI map gets
> > > > > added first and the e820 code overwrites it.
> > > > >
> > > > > The second problem is that we never mark SetVirtualAddressMap as runtime
> > > > > code, which we should according to the spec. Until we fix this the
> > > > > current hack can't go away, at least for architectures that *need* to
> > > > > call SVAM.
> > > > >
> > > > > More specifically x86 currently requires SVAM and sets the NX bit for
> > > > > pages not marked as *_CODE. So unless we do that late, it will crash
> > > > > trying to execute from non-executable memory. It's also worth noting
> > > > > that x86 calls SVAM late in the boot, so this will work until someone
> > > > > decides to overwrite/use BootServicesData from the OS.
> > > > >
> > > > > Notably arm64 disables it explicitly if the VA space is > 48bits, so
> > > > > doesn't suffer from any of these problems.
> > > > >
> > > > > This doesn't really deserve a fixes tag, since it brings back a hack to
> > > > > remedy a situation that was wrong long before that commit, but in case
> > > > > anyone hits the same bug ...
> > > > > Simon sent the original revert in the link, but we need a proper
> > > > > justification for it.
> > > > >
> > > > > Link: https://lore.kernel.org/u-boot/20241112131830.576864-1-sjg@chromium.org/
> > > > > Fixes: commit a68c9ac5d8af ("efi_memory: do not add U-Boot memory to the memory map")
> > > > > Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> > > > > ---
> > > >
> > > > Acked-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > > >
> > > > Like you mention in the commit message, I don't think it warrants a Fixes tag.
> > > >
> > > > -sughosh
> > > >
> > > > > Apologies for sending v2 so fast but we need this in for the release
> > > > > Changes since v1:
> > > > > - reword the commit message and fix spelling
> > > > >
> > > > >  lib/efi_loader/efi_memory.c | 11 ++++++++++-
> > > > >  1 file changed, 10 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> > > > > index e493934c7131..edd7da7d8c6e 100644
> > > > > --- a/lib/efi_loader/efi_memory.c
> > > > > +++ b/lib/efi_loader/efi_memory.c
> > > > > @@ -814,7 +814,16 @@ static void add_u_boot_and_runtime(void)
> > > > >  {
> > > > >         unsigned long runtime_start, runtime_end, runtime_pages;
> > > > >         unsigned long runtime_mask = EFI_PAGE_MASK;
> > > > > -
> > > > > +       unsigned long uboot_start, uboot_pages;
> > > > > +       unsigned long uboot_stack_size = CONFIG_STACK_SIZE;
> > > > > +
> > > > > +       /* Add U-Boot */
> > > > > +       uboot_start = ((uintptr_t)map_sysmem(gd->start_addr_sp, 0) -
> > > > > +                      uboot_stack_size) & ~EFI_PAGE_MASK;
> > > > > +       uboot_pages = ((uintptr_t)map_sysmem(gd->ram_top - 1, 0) -
> > > > > +                      uboot_start + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT;
> > > > > +       efi_add_memory_map_pg(uboot_start, uboot_pages, EFI_BOOT_SERVICES_CODE,
> > > > > +                             false);
> > > > >  #if defined(__aarch64__)
> > > > >         /*
> > > > >          * Runtime Services must be 64KiB aligned according to the
> > > > > --
> > > > > 2.45.2
> > > > >
> > >
> > > Thank you for digging into this. It is helpful to add more things to
> > > the commit message, but please redo your patch with a 'git revert' so
> > > we get the correct subject and body, as my patch did.
>
> I don't have a preference about the subject, but the body above is
> correct. It says "This reverts commit ..." and then explains _why_ we
> need to revert it.

Yes, we agree and although we are in bikeshedding territory now, I
don't mind sending a new one with a changed subject. Just let me know.
In any case feel free to merge this as
Revert "efi_memory: do not add U-Boot memory to the memory map"

Cheers
/Ilias
> --
> Tom