#
# Copyright (C) 2001-2004 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.text

.global context_save
.global context_restore

#include "context_offset.h"

## Save current CPU context
#
# Save CPU context to the kernel_context variable
# pointed by the 1st argument. Returns 1 in EAX.
#
context_save:
	movq (%rsp), %rdx     # the caller's return %eip
	# In %edi is passed 1st argument
	movq %rdx, OFFSET_PC(%rdi)
	movq %rsp, OFFSET_SP(%rdi)
	
	movq %rbx, OFFSET_RBX(%rdi)
	movq %rbp, OFFSET_RBP(%rdi)
	movq %r12, OFFSET_R12(%rdi)
	movq %r13, OFFSET_R13(%rdi)
	movq %r14, OFFSET_R14(%rdi)
	movq %r15, OFFSET_R15(%rdi)
	
	xorq %rax,%rax		# context_save returns 1
	incq %rax
	ret


## Restore current CPU context
#
# Restore CPU context from the kernel_context variable
# pointed by the 1st argument. Returns 0 in EAX.
#
context_restore:	
	movq OFFSET_R15(%rdi), %r15
	movq OFFSET_R14(%rdi), %r14
	movq OFFSET_R13(%rdi), %r13
	movq OFFSET_R12(%rdi), %r12
	movq OFFSET_RBP(%rdi), %rbp
	movq OFFSET_RBX(%rdi), %rbx	
	
	movq OFFSET_SP(%rdi), %rsp   # ctx->sp -> %rsp
	
	movq OFFSET_PC(%rdi), %rdx
	movq %rdx,(%rsp)

	xorq %rax,%rax		# context_restore returns 0
	ret