Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions

[Baoquan He]

On 07/28/17 at 06:18pm, Baoquan He wrote:
> On 07/28/17 at 11:55am, Ingo Molnar wrote:
> > 
> > * Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote:
> > 
> > > On Fri, 21 Jul, at 09:19:56PM, Baoquan He wrote:
> > > >
> > > > There are places where the efi map is getting and used like this. E.g
> > > > in efi_high_alloc() of drivers/firmware/efi/libstub/efi-stub-helper.c.
> > > > EFI developers worry the size of efi_memory_desc_t could not be the same
> > > > as e->efi_memdesc_size?
> > > > 
> > > > Hi Matt,
> > > > 
> > > > Could you help have a look at this?
> > > 
> > > You're exactly right. The code guards against the size of the
> > > efi_memory_desc_t struct changing. The UEFI spec says to traverse the
> > > memory map this way.
> > 
> > This is not obvious and looks pretty ugly as well, and open coded in several 
> > places.
> > 
> > At minimum we should have an efi_memdesc_ptr(efi, i) wrapper inline (or so) that 
> > gives us the entry pointer, plus a comment that points out that ->memdesc_size 
> > might not be equal to sizeof(efi_memory_memdesc_t).
> 
> Seems for_each_efi_memory_desc_in_map() can be used to hide the
> calculation and type cast each time for better memmap loop.

Oh, plesse ignore this noise, it need involve struct efi_memory_map which
need be built till efi_init() called.