Re: [PATCH 15/16] bootparam: Pass acpi_rsdp pointer in bootparam

H. Peter Anvin
2013-09-10T22:53:35Z

On 09/10/2013 02:44 PM, Vivek Goyal wrote:
> Currently kexec does not enables EFI and its tables in second kernel. Hence
> acpi rsdp root pointer is passed on command line. But secureboot does not trust
> acpi_rsdp on command line as kernel can execute some of the code as retrieved
> by following acpi_rsdp and root can modify command line. So in secureboot
> mode we ignore acpi_rsdp on command line.
>
> Start passing it in bootparams for the time being. kexec-tools will prepare
> the bootparams and put acpi_rsdp pointer there.
>
> Peter Jones suggested that scan all ACPI memory for acpi_rsdp if EFI is
> not enabled. This probably is a better fix and most likely this patch will
> change and adopt that approach down the line.
>
> In fact if we figure out how to make UEFI run time calls in second kernel,
> we will not need acpi_rsdp at all.
>

Borislav Petkov has been working on a fixed mapping of UEFI memory,
which should allow UEFI runtime calls across kexec.

-hpa