Re: [tip:x86/boot] x86/boot: Early parse RSDP and save it in boot_params

[Ard Biesheuvel]

On Mon, 11 Feb 2019 at 11:43, Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Mon, Feb 11, 2019 at 11:24:26AM +0100, Borislav Petkov wrote:
> > It is only an observation for now though...
>
> Ok, now I did this:
>
>         for (i = 0; i < systab->nr_tables; i++) {
>                 acpi_physical_address table;
>                 void *config_tables;
>                 efi_guid_t guid;
>
>                 if ((unsigned long)systab->tables >> 32)                        <---
>                         asm volatile("1:\n jmp 1b");
>
>                 config_tables = (void *)(systab->tables + size * i);
>
> It did stop at the endless loop there which would mean that
> systab->tables is simply pointing somewhere into the weeds.
>


As I pointed out in my previous reply, systab will be the wrong type
on 32-bit firmware, it needs to be efi_system_table_32_t


> Asm is:
>
> ---
> # arch/x86/boot/compressed/acpi.c:96:                   asm volatile("1:\n jmp 1b");
> #APP
> # 96 "arch/x86/boot/compressed/acpi.c" 1
>         1:
>  jmp 1b
> # 0 "" 2
> #NO_APP
>         movq    112(%rcx), %rdi # systab_147->tables, _31
> .L29:
> # arch/x86/boot/compressed/acpi.c:98:           config_tables = (void *)(systab->tables + size * i);
>         addq    %r9, %rdi       # ivtmp.64, config_tables
> # arch/x86/boot/compressed/acpi.c:104:                  guid = tmp_table->guid;
> ---
>
> and RDI is
>
> rdi            0x630646870
>
> in gdb.
>
> systab itself gets computed to something low: 0x3fedb010.
>
> Hmmm. Could it be that that EDK BIOS image is buggy?
>
> [    0.000000] efi: EFI v2.70 by EDK II
> [    0.000000] efi:  SMBIOS=0x3feb9000  ACPI=0x3fee7000  ACPI 2.0=0x3fee7014  MEMATTR=0x3f524110
>
> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.