Re: [PATCH] x86/boot/KASLR: exclude EFI_BOOT_SERVICES_{CODE|DATA} from KASLR's choice

[Baoquan He]

On 07/06/17 at 03:57pm, Matt Fleming wrote:
> On Thu, 06 Jul, at 08:31:07AM, Naoya Horiguchi wrote:
> > +	for (i = 0; i < nr_desc; i++) {
> > +		md = (efi_memory_desc_t *)(pmap + (i * e->efi_memdesc_size));
> > +
> > +		/*
> > +		 * EFI_BOOT_SERVICES_{CODE|DATA} are avoided because boot
> > +		 * services regions could be accessed after ExitBootServices()
> > +		 * due to the workaround for buggy firmware.
> > +		 */
> > +		if (!(md->type == EFI_LOADER_CODE ||
> > +		      md->type == EFI_LOADER_DATA ||
> > +		      md->type == EFI_CONVENTIONAL_MEMORY))
> > +			continue;
> 
> Wouldn't it make more sense to *only* use EFI_CONVENTIONAL_MEMORY?
> 
> You can't re-use EFI_LOADER_* regions because the kaslr code is run so
> early in boot that you've no idea if data the kernel will need is in
> those EFI_LOADER_* regions.
> 
> For example, we pass struct setup_data objects inside of
> EFI_LOADER_DATA regions.

It doesn't matter because we have tried to avoid those memory setup_data
resides in in mem_avoid_overlap(). Here discarding EFI_LOADER_* could
discard the whole regions while setup_data could occupy small part of
them.