From mboxrd@z Thu Jan 1 00:00:00 1970 From: Baoquan He Subject: Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Date: Fri, 4 Aug 2017 19:40:05 +0800 Message-ID: <20170804114005.GC29975@x1> References: <1500542189-15779-1-git-send-email-bhe@redhat.com> <20170721103757.hc74czr3mfunrv6c@gmail.com> <20170721131956.GK2344@x1> <20170724133410.GC11076@codeblueprint.co.uk> <20170728095525.y4tuv6aavzfs4ekb@gmail.com> <20170728112603.GS24304@x1> <20170804112325.GB8187@codeblueprint.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170804112325.GB8187-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Matt Fleming Cc: Ingo Molnar , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, izumi.taku-+CUm20s59erQFUHtdCDX3A@public.gmane.org, fanc.fnst-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org, thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org, Ard Biesheuvel , linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-efi@vger.kernel.org On 08/04/17 at 12:23pm, Matt Fleming wrote: > On Fri, 28 Jul, at 07:26:03PM, Baoquan He wrote: > > Hi Matt, > > > > On 07/28/17 at 11:55am, Ingo Molnar wrote: > > > > > > * Matt Fleming 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). > > > > I can make a efi_memdesc_ptr(efi, i) wrapper as Ingo suggested and use > > it here if you agree. Seems it might be not good to add another > > for_each_efi_memory_desc_xxxx wrapper since there are different memmap > > data structures in x86 boot and in general efi libstub. Or any other > > idea? > > I think adding a wrapper is fine, but I'd suggest including the word > "early" (or something similar) to explain that it should only be used > during bootup -- we want everyone else to use the > for_each_efi_memory_*() API. Thanks, Matt. I can do that. Do you think below helper definition is OK to you? If yes, I can upstate with it and post v9. #define efi_early_memdesc_ptr(map, desc_size, n) \ (efi_memory_desc_t *)((void *)(map) + ((n) * (desc_size)))