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Commit fb526835 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Ingo Molnar
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x86/boot/compressed/64: Save and restore trampoline memory 



The memory area we found for trampoline shouldn't contain anything
useful. But let's preserve the data anyway. Just to be on safe side.

paging_prepare() would save the data into a buffer.

cleanup_trampoline() would restore it back once we are done with the
trampoline.

Tested-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180226180451.86788-4-kirill.shutemov@linux.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3548e131

arch/x86/boot/compressed/head_64.S

+10 −0
Original line number Diff line number Diff line
@@ -355,6 +355,16 @@ ENTRY(startup_64) 
	lretq

lvl5:



	/*

	 * cleanup_trampoline() would restore trampoline memory.

	 *

	 * RSI holds real mode data and needs to be preserved across

	 * this function call.

	 */

	pushq	%rsi

	call	cleanup_trampoline

	popq	%rsi



	/* Zero EFLAGS */

	pushq	$0

	popfq

arch/x86/boot/compressed/pgtable_64.c

+13 −0
Original line number Diff line number Diff line 
#include <asm/processor.h>

#include "pgtable.h"

#include "../string.h"



/*

 * __force_order is used by special_insns.h asm code to force instruction
@@ -18,6 +19,9 @@ struct paging_config { 
	unsigned long l5_required;

};



/* Buffer to preserve trampoline memory */

static char trampoline_save[TRAMPOLINE_32BIT_SIZE];



/*

 * Trampoline address will be printed by extract_kernel() for debugging

 * purposes.
@@ -69,5 +73,14 @@ struct paging_config paging_prepare(void) 


	trampoline_32bit = (unsigned long *)paging_config.trampoline_start;



	/* Preserve trampoline memory */

	memcpy(trampoline_save, trampoline_32bit, TRAMPOLINE_32BIT_SIZE);



	return paging_config;

}



void cleanup_trampoline(void)

{

	/* Restore trampoline memory */

	memcpy(trampoline_32bit, trampoline_save, TRAMPOLINE_32BIT_SIZE);

}