linux-kernel - [PATCH] x86/asm, microcode: Add __PAGE_OFFSET

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Message-ID: <20160727120939.GA18911@nazgul.tnic>
Date:	Wed, 27 Jul 2016 14:09:39 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Kees Cook <keescook@...omium.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: [PATCH] x86/asm, microcode: Add __PAGE_OFFSET_BASE define on 32-bit

On Wed, Jul 27, 2016 at 12:36:55PM +0200, Ingo Molnar wrote:
> On top of:
> 
>   tip/x86/microcode df15929f8f5c: Merge branch 'linus' into x86/microcode, to pick up merge window changes
> 
> (the merge commit is fresh, I just pushed it out)
> 
> ... because this way there's actually a CONFIG_RANDOMIZE_MEMORY option available 
> in that kernel tree.

Here it is:

---
From: Borislav Petkov <bp@...e.de>
Subject: [PATCH] x86/asm, microcode: Add __PAGE_OFFSET_BASE define on 32-bit

... in order to avoid ifdeffery in code computing the ASLR randomization
offset. Remove that ifdeffery in the microcode loader.

Suggested-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/page_32_types.h  | 3 ++-
 arch/x86/kernel/cpu/microcode/intel.c | 2 --
 2 files changed, 2 insertions(+), 3 deletions(-)

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
 
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 0f97ae93441b..cdc0deab00c9 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -818,13 +818,11 @@ void load_ucode_intel_ap(void)
 	if (blobs_p->valid) {
 		start = blobs_p->start;
 
-#ifdef CONFIG_RANDOMIZE_MEMORY
 		/*
 		 * Pay attention to CONFIG_RANDOMIZE_MEMORY=y as it shuffles
 		 * physmem mapping too and there we have the initrd.
 		 */
 		start += PAGE_OFFSET - __PAGE_OFFSET_BASE;
-#endif
 	}
 
 	collect_cpu_info_early(&uci);
-- 
2.8.4

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

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