From: Andrey Ryabinin <a.ryabi...@samsung.com>

commit d0f77d4d04b222a817925d33ba3589b190bfa863 upstream.

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.ryabi...@samsung.com>
Cc: <sta...@vger.kernel.org> # 4.0+
Cc: Alexander Popov <alpo...@ptsecurity.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Andrey Konovalov <adech...@gmail.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Link: 
http://lkml.kernel.org/r/1435828178-10975-2-git-send-email-a.ryabi...@samsung.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Andrey Ryabinin <aryabi...@odin.com>
---
 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 67df086..357ce8a 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -164,6 +164,8 @@ 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_handlers[i]);
        load_idt((const struct desc_ptr *)&idt_descr);
@@ -178,7 +180,6 @@ void __init x86_64_start_kernel(char * real_mode_data)
        if (console_loglevel == 10)
                early_printk("Kernel alive\n");
 
-       clear_page(init_level4_pgt);
        /* set init_level4_pgt kernel high mapping*/
        init_level4_pgt[511] = early_level4_pgt[511];
 
-- 
2.4.6

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