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SubjectRe: [tip:x86/boot] x86/boot: Early parse RSDP and save it in boot_params
On Mon, Feb 11, 2019 at 01:22:20AM +0100, Borislav Petkov wrote:
>On Fri, Feb 08, 2019 at 10:53:22PM +0100, Borislav Petkov wrote:
>> On Fri, Feb 08, 2019 at 12:44:51PM -0800, Guenter Roeck wrote:
>> > Yes, the kernel boots if I comment out that function and have it return 0.
>>
>> Thanks, this localizes the issue significantly.
>
>Some observations:
>
> } else {
> efi_config_table_32_t *tmp_table;
>
> tmp_table = config_tables;
> guid = tmp_table->guid; <--- *
> table = tmp_table->table;
> }
>
>It blows up at that tmp_table->guid deref above. Singlestepping through
>it with gdb shows:
>
># arch/x86/boot/compressed/acpi.c:114: guid = tmp_table->guid;
> movq (%rdi), %rax # MEM[(struct efi_config_table_32_t *)config_tables_37].guid, guid
> movq 8(%rdi), %rsi # MEM[(struct efi_config_table_32_t *)config_tables_37].guid, guid
># arch/x86/boot/compressed/acpi.c:115: table = tmp_table->table;
> movl 16(%rdi), %r10d # MEM[(struct efi_config_table_32_t *)config_tables_37].table, table
> jmp .L30 #
>
>and %rdi has:
>
> rdi 0x630646870
>
>which is an address above 4G but we're using a 32-bit EFI BIOS.
>
>Which begs the question whether EFI system tables can even be mapped at
>something above 4G with a 32-bit EFI and whether that could work ok.
>Hmm.

Thanks for your help. As you said, I am not wure whether 32-bit EFI can
map table address above 4G.
If the map method has problem, I think adding a check here can work.

Thanks,
Chao Fan

>
>Lemme add Ard and mfleming for insight here.
>
>Thx.
>
>--
>Regards/Gruss,
> Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>


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