linux-kernel - [tip:x86/urgent] x86/init: Clear 'init_level4

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Message-ID: <tip-d0f77d4d04b222a817925d33ba3589b190bfa863@git.kernel.org>
Date:	Mon, 6 Jul 2015 08:36:19 -0700
From:	tip-bot for Andrey Ryabinin <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	alpopov@...ecurity.com, peterz@...radead.org, hpa@...or.com,
	adech.fo@...il.com, dvyukov@...gle.com, glider@...gle.com,
	bp@...en8.de, torvalds@...ux-foundation.org, mingo@...nel.org,
	a.ryabinin@...sung.com
Subject: [tip:x86/urgent] x86/init: Clear 'init_level4_pgt' earlier

Commit-ID:  d0f77d4d04b222a817925d33ba3589b190bfa863
Gitweb:     http://git.kernel.org/tip/d0f77d4d04b222a817925d33ba3589b190bfa863
Author:     Andrey Ryabinin <a.ryabinin@...sung.com>
AuthorDate: Thu, 2 Jul 2015 12:09:33 +0300
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 6 Jul 2015 14:53:13 +0200

x86/init: Clear 'init_level4_pgt' earlier

Currently x86_64_start_kernel() has two KASAN related
function calls. The first call maps shadow to early_level4_pgt,
the second maps shadow to init_level4_pgt.

If we move clear_page(init_level4_pgt) earlier, we could hide
KASAN low level detail from generic x86_64 initialization code.
The next patch will do it.

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
Cc: <stable@...r.kernel.org> # 4.0+
Cc: Alexander Popov <alpopov@...ecurity.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Andrey Konovalov <adech.fo@...il.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1435828178-10975-2-git-send-email-a.ryabinin@samsung.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/head64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 5a46681..65c8985 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -166,6 +166,8 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 	/* clear bss before set_intr_gate with early_idt_handler */
 	clear_bss();
 
+	clear_page(init_level4_pgt);
+
 	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
 		set_intr_gate(i, early_idt_handler_array[i]);
 	load_idt((const struct desc_ptr *)&idt_descr);
@@ -177,7 +179,6 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 	 */
 	load_ucode_bsp();
 
-	clear_page(init_level4_pgt);
 	/* set init_level4_pgt kernel high mapping*/
 	init_level4_pgt[511] = early_level4_pgt[511];
 
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