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x86/boot/compressed/64: Save and restore trampoline memory

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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: Borislav Petkov <bp@suse.de>
Signed-off-by: Kirill 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kirill A. Shutemov 2018-02-26 21:04:49 +03:00 committed by Ingo Molnar
parent 3548e131ec
commit fb5268354d
2 changed files with 23 additions and 0 deletions
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10
arch/x86/boot/compressed/head_64.S
View file

@ -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

13
arch/x86/boot/compressed/pgtable_64.c
View file

@ -1,5 +1,6 @@
#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);
}