linux-kernel - Re: [tip:x86/microcode] x86/microcode/intel: Fix initrd loading with CONFIG_RANDOMIZE

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Date:	Wed, 27 Jul 2016 07:45:43 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Kees Cook <keescook@...omium.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Garnier <thgarnie@...gle.com>,
	Nicolai Stange <nicstange@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [tip:x86/microcode] x86/microcode/intel: Fix initrd loading with
 CONFIG_RANDOMIZE_MEMORY=y

On Tue, Jul 26, 2016 at 01:37:07PM -0700, Kees Cook wrote:
> These ifdefs aren't needed if we added a no-op __PAGE_OFFSET_BASE to
> the 32-bit page table headers. Then the compiler will DTRT with the
> start calculation. When CONFIG_RANDOMIZE_MEMORY is set, start will
> have a non-zero value, and when not set it'll be 0.

Something like this? I'm trying to mimick the 64-bit version:

---
diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h
index 3a52ee0e726d..3bae4969ac65 100644
--- a/arch/x86/include/asm/page_32_types.h
+++ b/arch/x86/include/asm/page_32_types.h
@@ -13,7 +13,8 @@
  * If you want more physical memory than this then see the CONFIG_HIGHMEM4G
  * and CONFIG_HIGHMEM64G options in the kernel configuration.
  */
-#define __PAGE_OFFSET		_AC(CONFIG_PAGE_OFFSET, UL)
+#define __PAGE_OFFSET_BASE	_AC(CONFIG_PAGE_OFFSET, UL)
+#define __PAGE_OFFSET		__PAGE_OFFSET_BASE
 
 #define __START_KERNEL_map	__PAGE_OFFSET
 
-- 
Regards/Gruss,
    Boris.

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