source: mainline/uspace/lib/libc/arch/ia32/src/fibril.S@ 12f91130

#
# 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 context_t variable
# pointed by the 1st argument. Returns 1 in EAX.
#
context_save:
        movl 0(%esp),%eax       # the caller's return %eip
        movl 4(%esp),%edx       # address of the context variable to save context to

        movl %esp,0(%edx)       # %esp -> ctx->sp
        movl %eax,4(%edx)       # %eip -> ctx->pc
        movl %ebx,8(%edx)       # %ebx -> ctx->ebx
        movl %esi,12(%edx)      # %esi -> ctx->esi
        movl %edi,16(%edx)      # %edi -> ctx->edi
        movl %ebp,20(%edx)      # %ebp -> ctx->ebp

        # Save TLS
        movl %gs:0, %eax
        movl %eax, 24(%edx)     # tls -> ctx->tls
        
        xorl %eax,%eax          # context_save returns 1
        incl %eax
        ret


## Restore saved CPU context
#
# Restore CPU context from context_t variable
# pointed by the 1st argument. Returns 0 in EAX.
#
context_restore:
        movl 4(%esp),%eax       # address of the context variable to restore context from
        movl 0(%eax),%esp       # ctx->sp -> %esp
        movl 4(%eax),%edx       # ctx->pc -> %edx
        movl 8(%eax),%ebx       # ctx->ebx -> %ebx
        movl 12(%eax),%esi      # ctx->esi -> %esi
        movl 16(%eax),%edi      # ctx->edi -> %edi
        movl 20(%eax),%ebp      # ctx->ebp -> %ebp

        movl %edx,0(%esp)       # ctx->pc -> saver's return %eip

        # Set thread local storage
        pushl %edi
        movl 24(%eax), %eax   # Set arg1 to TLS addr
        movl $1, %edi         # Syscall 1
        int $0x30
        popl %edi
        
        xorl %eax,%eax          # context_restore returns 0
        ret