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#
# 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
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

.text

.global context_save
.global context_restore


## Save current CPU context
#
# Save CPU context to the kernel_context variable
# pointed by the 1st argument. Returns 1 in EAX.
#
context_save:
    push %ebx

    movl 4(%esp),%eax   # the caller's return %eip
    movl 8(%esp),%ebx   # address of the kernel_context variable to save context to
        movl %eax,4(%ebx)   # %eip -> ctx->pc
    movl %esp,(%ebx)    # %esp -> ctx->sp

    movl %ebx,%eax
    pop %ebx

    movl %ebx,8(%eax)
    movl %ecx,12(%eax)
    movl %edx,16(%eax)
    movl %esi,20(%eax)
    movl %edi,24(%eax)
    movl %ebp,28(%eax)    
    
    xorl %eax,%eax      # context_save returns 1
    incl %eax
    ret


## Restore current CPU context
#
# Restore CPU context from the kernel_context variable
# pointed by the 1st argument. Returns 0 in EAX.
#    
context_restore:
    movl 4(%esp),%eax   # address of the kernel_context variable to restore context from
    movl (%eax),%esp    # ctx->sp -> %esp
    addl $4,%esp        # this is for the pop we don't do

    movl 8(%eax),%ebx
    movl 12(%eax),%ecx
    movl 16(%eax),%edx
    movl 20(%eax),%esi
    movl 24(%eax),%edi
    movl 28(%eax),%ebp

    movl 4(%eax),%eax
    movl %eax,(%esp)    # ctx->pc -> saver's return %eip
        xorl %eax,%eax      # context_restore returns 0
    ret