Date: Mon, 18 Apr 2016 09:50:23 -0700 From: Kees Cook <keescook@...omium.org> To: Ingo Molnar <mingo@...nel.org> Cc: Yinghai Lu <yinghai@...nel.org>, Baoquan He <bhe@...hat.com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Matt Redfearn <matt.redfearn@...tec.com>, "x86@...nel.org" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Vivek Goyal <vgoyal@...hat.com>, Andy Lutomirski <luto@...nel.org>, Lasse Collin <lasse.collin@...aani.org>, Andrew Morton <akpm@...ux-foundation.org>, Dave Young <dyoung@...hat.com>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer On Fri, Apr 15, 2016 at 1:09 AM, Ingo Molnar <mingo@...nel.org> wrote: > > * Kees Cook <keescook@...omium.org> wrote: > >> From: Yinghai Lu <yinghai@...nel.org> >> >> This change makes later calculations about where the kernel is located >> easier to reason about. To better understand this change, we must first >> clarify what VO and ZO are. They were introduced in commits by hpa: >> >> 77d1a49 x86, boot: make symbols from the main vmlinux available >> 37ba7ab x86, boot: make kernel_alignment adjustable; new bzImage fields >> >> Specifically: >> >> VO: >> - uncompressed kernel image >> - size: VO__end - VO__text ("VO_INIT_SIZE" define) >> >> ZO: >> - bootable compressed kernel image (boot/compressed/vmlinux) >> - head text + compressed kernel (VO and relocs table) + decompressor code >> - size: ZO__end - ZO_startup_32 ("ZO_INIT_SIZE" define, though see below) >> >> The INIT_SIZE definition is used to find the larger of the two image sizes: >> >> #define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset) >> #define VO_INIT_SIZE (VO__end - VO__text) >> #if ZO_INIT_SIZE > VO_INIT_SIZE >> #define INIT_SIZE ZO_INIT_SIZE >> #else >> #define INIT_SIZE VO_INIT_SIZE >> #endif > > Please also harmonize all the prefixes, i.e. use VO__/ZO__ everywhere (rename > things where necessary), instead of this mixed up VO_/ZO_/VO__/ZO__ mess. I'm going to leave these as they are: they're auto-generated based on various functions of interest: boot/Makefile:sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(startup_32\|startup_64\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|input_data\|_end\|z_.*\)$$/\#define ZO_\2 0x\1/p' i.e. ZO__end is _end's location. ZO_input_data is input_data's position. I think it would further complicate things if we tried to consolidate consecutive "_"s, or if we eliminated the leading "_" (ZOinput_data and ZO_end). -Kees -- Kees Cook Chrome OS & Brillo Security
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