[U-Boot] [PATCH 1/1] x86: efi_loader: Fix invalid address return from efi_alloc()

[Park, Aiden]

Hi Heinrich and Bin,

> -----Original Message-----
> From: Heinrich Schuchardt [mailto:xypron.glpk at gmx.de]
> Sent: Wednesday, August 28, 2019 10:16 PM
> To: Bin Meng <bmeng.cn at gmail.com>; Park, Aiden <aiden.park at intel.com>
> Cc: Simon Glass <sjg at chromium.org>; u-boot at lists.denx.de; Alexander Graf
> <agraf at csgraf.de>
> Subject: Re: [PATCH 1/1] x86: efi_loader: Fix invalid address return from
> efi_alloc()
> 
> On 8/29/19 5:36 AM, Bin Meng wrote:
> > +Heinrich,
> >
> > On Wed, Aug 28, 2019 at 2:35 AM Park, Aiden <aiden.park at intel.com> wrote:
> >>
> >> This issue can be seen on 32bit operation when one of E820_RAM type
> >> entries is greater than 4GB memory space.
> >>
> >> The efi_alloc() finds a free memory in the conventional memory which
> >> is greater than 4GB. But, it does type cast to 32bit address space
> >> and eventually returns invalid address.
> >>
> >> Signed-off-by: Aiden Park <aiden.park at intel.com>
> >> ---
> >>   arch/x86/lib/e820.c | 22 +++++++++++++++++++++-
> >>   1 file changed, 21 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/x86/lib/e820.c b/arch/x86/lib/e820.c index
> >> d6ae2c4e9d..3e93931231 100644
> >> --- a/arch/x86/lib/e820.c
> >> +++ b/arch/x86/lib/e820.c
> >> @@ -41,11 +41,15 @@ void efi_add_known_memory(void)
> >>   {
> >>          struct e820_entry e820[E820MAX];
> >>          unsigned int i, num;
> >> -       u64 start, pages;
> >> +       u64 start, pages, ram_top;
> >>          int type;
> >>
> >>          num = install_e820_map(ARRAY_SIZE(e820), e820);
> >>
> >> +       ram_top = (u64)gd->ram_top & ~EFI_PAGE_MASK;
> >> +       if (!ram_top)
> >
> > So for the logic here to work, gd->ram_top is already zero in 32-bit,
> > right? I was wondering how U-Boot could boot on such target?
> 
> If in 32bit mode RAM addresses up to 2^32-1 are available, gd->ram_top is 0 due
> to overflow.
> 
> >
> >> +               ram_top = 0x100000000ULL;
> 
> In this special case we correct the value to 4GB.
> 
> >> +
> >>          for (i = 0; i < num; ++i) {
> >>                  start = e820[i].addr;
> >>                  pages = ALIGN(e820[i].size, EFI_PAGE_SIZE) >>
> >> EFI_PAGE_SHIFT; @@ -70,6 +74,22 @@ void efi_add_known_memory(void)
> >>                  }
> >>
> >>                  efi_add_memory_map(start, pages, type, false);
> >> +
> >> +               if (type == EFI_CONVENTIONAL_MEMORY) {
> >> +                       u64 end = start + (pages << EFI_PAGE_SHIFT);
> >> +
> >> +                       /* reserve the memory region greater than ram_top */
> >> +                       if (ram_top < start) {
> >> +                               efi_add_memory_map(start, pages,
> >> +                                                  EFI_BOOT_SERVICES_DATA,
> >> +                                                  true);
> >
> > Heinrich, could you please review the changes here?
> 
> These lines are verbatim copies of what we have in lib/efi_loader/efi_memory.c.
> Function wise this is ok.
> 
> But this creates code duplication. Most of what is in this loop and in the loop in
> lib/efi_loader/efi_memory.c (starting at /* Remove partial pages */) could be
> put into a separate common function.
> 
> Aiden, do you want to give a try?
> 
I have a quick question here. Do we really need to override
efi_add_known_memory() in arch/x86/lib/e820.c?
I think the original weak function would be okay for x86 arch as well.

> Best regards
> 
> Heinrich
> 
> >
> >> +                       } else if (start < ram_top && ram_top < end) {
> >> +                               pages = (end - ram_top) >> EFI_PAGE_SHIFT;
> >> +                               efi_add_memory_map(ram_top, pages,
> >> +                                                  EFI_BOOT_SERVICES_DATA,
> >> +                                                  true);
> >> +                       }
> >> +               }
> >>          }
> >>   }
> >>   #endif /* CONFIG_IS_ENABLED(EFI_LOADER) */
> >> --
> >
> > Regards,
> > Bin
> >

Best Regards,
Aiden