On Thu, Oct 04, 2018 at 10:03:21AM +0200, Joerg Roedel wrote:
> I also triggered this when working in the PTI-x32 code. It always
> happens on a 32-bit PAE kernel for me.
>
> Tracking it down I ended up in (iirc) arch/x86/mm/pageattr.c
> function static_protections():
>
> /*
> * The BIOS area between 640k and 1Mb needs to be executable for
> * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
> */
> #ifdef CONFIG_PCI_BIOS
> if (pcibios_enabled && within(pfn, BIOS_BEGIN >> PAGE_SHIFT,
> BIOS_END >> PAGE_SHIFT))
> pgprot_val(forbidden) |= _PAGE_NX;
> #endif
>
> I think that is the reason we are seeing this in that configuration.
So looking at this, BIOS_BEGIN and BIOS_END is the same range as the ISA
range:
#define ISA_START_ADDRESS 0x000a0000
#define ISA_END_ADDRESS 0x00100000
#define BIOS_BEGIN 0x000a0000
#define BIOS_END 0x00100000
and I did try marking the ISA range RO in mark_rodata_ro() but the
machine wouldn't boot after. So I'm guessing BIOS needs to write there
some crap.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
