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

Lemme add Ard and mfleming for insight here.



Good mailing practices for 400: avoid top-posting and trim the reply.

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