linux-kernel - [PATCH v2 1/6] x86_64, init: clear init_level4

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Message-id: <1435828178-10975-2-git-send-email-a.ryabinin@samsung.com>
Date:	Thu, 02 Jul 2015 12:09:33 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Cc:	Andrey Konovalov <adech.fo@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Alexander Popov <alpopov@...ecurity.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	linux-kernel@...r.kernel.org,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	stable@...r.kernel.org
Subject: [PATCH v2 1/6] x86_64, 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+
---
 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];
 
-- 
2.4.5

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