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x86: hibernation: document __save_processor_state() on x86 

Document the fact that __save_processor_state() has to save all CPU
registers referred to by the kernel in case a different kernel is
used to load and restore a hibernation image containing it.

Sigend-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Rafael J. Wysocki 2008-01-30 13:30:04 +01:00 committed by Ingo Molnar
parent 9484b1eb4d
commit 5c9c9bec05
2 changed files with 28 additions and 1 deletions
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20
arch/x86/kernel/suspend_64.c
View File

@ -19,6 +19,21 @@ extern const void __nosave_begin, __nosave_end;
struct saved_context saved_context;
/**
* __save_processor_state - save CPU registers before creating a
* hibernation image and before restoring the memory state from it
* @ctxt - structure to store the registers contents in
*
* NOTE: If there is a CPU register the modification of which by the
* boot kernel (ie. the kernel used for loading the hibernation image)
* might affect the operations of the restored target kernel (ie. the one
* saved in the hibernation image), then its contents must be saved by this
* function. In other words, if kernel A is hibernated and different
* kernel B is used for loading the hibernation image into memory, the
* kernel A's __save_processor_state() function must save all registers
* needed by kernel A, so that it can operate correctly after the resume
* regardless of what kernel B does in the meantime.
*/
void __save_processor_state(struct saved_context *ctxt)
{
kernel_fpu_begin();
@ -69,6 +84,11 @@ static void do_fpu_end(void)
kernel_fpu_end();
}
/**
* __restore_processor_state - restore the contents of CPU registers saved
* by __save_processor_state()
* @ctxt - structure to load the registers contents from
*/
void __restore_processor_state(struct saved_context *ctxt)
{
/*

9
include/asm-x86/suspend_64.h
View File

@ -15,7 +15,14 @@ arch_prepare_suspend(void)
return 0;
}
/* Image of the saved processor state. If you touch this, fix acpi/wakeup.S. */
/*
* Image of the saved processor state, used by the low level ACPI suspend to
* RAM code and by the low level hibernation code.
*
* If you modify it, fix arch/x86/kernel/acpi/wakeup_64.S and make sure that
* __save/__restore_processor_state(), defined in arch/x86/kernel/suspend_64.c,
* still work as required.
*/
struct saved_context {
struct pt_regs regs;
u16 ds, es, fs, gs, ss;