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##=============================================================================
##
## context.S
##
## i386 context switch code
##
##=============================================================================
#####ECOSGPLCOPYRIGHTBEGIN####
## -------------------------------------------
## This file is part of eCos, the Embedded Configurable Operating System.
## Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
##
## eCos is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free
## Software Foundation; either version 2 or (at your option) any later version.
##
## eCos is distributed in the hope that it will be useful, but WITHOUT ANY
## WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
## for more details.
##
## You should have received a copy of the GNU General Public License along
## with eCos; if not, write to the Free Software Foundation, Inc.,
## 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
##
## As a special exception, if other files instantiate templates or use macros
## or inline functions from this file, or you compile this file and link it
## with other works to produce a work based on this file, this file does not
## by itself cause the resulting work to be covered by the GNU General Public
## License. However the source code for this file must still be made available
## in accordance with section (3) of the GNU General Public License.
##
## This exception does not invalidate any other reasons why a work based on
## this file might be covered by the GNU General Public License.
##
## Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
## at http://sources.redhat.com/ecos/ecos-license/
## -------------------------------------------
#####ECOSGPLCOPYRIGHTEND####
##=============================================================================
#######DESCRIPTIONBEGIN####
##
## Author(s): jskov
## Contributors:jskov, pjo, nickg
## Date: 1999-01-20
## Purpose: i386 context switch code
## Description: This file contains implementations of the thread context
## switch routines. It also contains the longjmp() and setjmp()
## routines.
## Based on PowerPC context.S, using data from SYSV ABI4, i386
## supplement (page 37-38)
## http://www.sco.com/products/layered/develop/devspecs/abi386-4.pdf
##
######DESCRIPTIONEND####
##
##=============================================================================
#include <pkgconf/hal.h>
#include <cyg/hal/i386.inc>
#include <cyg/hal/arch.inc>
#------------------------------------------------------------------------------
# function declaration macro
#define FUNC_START(name) \
.globl name; \
name:
#------------------------------------------------------------------------------
# hal_thread_switch_context
# Switch thread contexts
# : 0(%esp) : return address
# : 4(%esp) : address of sp of next thread to execute
# : 8(%esp) : address of sp save location of current thread
#
# %eax, %ecx, and %edx are ours to abuse.
FUNC_START(hal_thread_switch_context)
# Pop the return address from the stack, but leave the
# arguments there so that the caller can remove them
# itself when we return.
popl %ecx # pop return eip
movl 0(%esp),%eax # get next context ptr
movl 4(%esp),%edx # get this context ptr
# Save context in the same format as an
# exception
pushfl # save eflags
pushl %cs # save cs
pushl %ecx # save eip
pushl $-1 # push fake vector
pushal # push general registers
hal_fpu_push_ctx # push FPU state
# Store the context ptr
movl %esp,(%edx)
hal_thread_switch_context_load:
# The pointer to the next context is in EAX
movl (%eax),%esp # Point ESP at new state
# Merge the IF bit in the saved EFLAGS with the rest of the
# bits currently in EFLAGS.
movl i386reg_eflags(%esp),%ebx # EBX = saved EFLAGS
andl $0x0200,%ebx # isolate IF bit
pushfl # push current flags
popl %ecx # pop into ECX
btrl $9,%ecx # clear IF flag in current EFLAGS
orl %ebx,%ecx # Or in saved IF bit
movl %ecx,i386reg_eflags(%esp) # Restore to saved state for use by iret
# Now we can load the state and enter next thread
hal_fpu_pop_ctx # Pop FPU state
popal # unstack general registers
add $4,%esp # skip vector number
iret # And return
#------------------------------------------------------------------------------
# hal_thread_load_context
# Load thread context
# : 4(%esp) = address of sp of thread to execute
#
# %eax, %ecx, and %edx are ours to abuse.
FUNC_START(hal_thread_load_context)
movl 4(%esp),%eax # get new context ptr
# Jump into hal_thread_switch_context at the right
# point to load this context.
jmp hal_thread_switch_context_load
#------------------------------------------------------------------------------
# HAL longjmp, setjmp implementations
# hal_setjmp saves only to callee save registers ebp, ebx, esi, edi and
# and esp+pc into buffer supplied in 4(esp)
# Note: These definitions are repeated in hal_arch.h. If changes are required
# remember to update both sets.
#define CYGARC_JMP_BUF_SP 0
#define CYGARC_JMP_BUF_EBP 1
#define CYGARC_JMP_BUF_EBX 2
#define CYGARC_JMP_BUF_ESI 3
#define CYGARC_JMP_BUF_EDI 4
#define CYGARC_JMP_BUF_PC 5
#define CYGARC_JMP_BUF_SIZE 6
FUNC_START(hal_setjmp)
# Get jmpbuf pointer
movl 4(%esp),%eax
# Save regular registers
movl %ebp,CYGARC_JMP_BUF_EBP*4(%eax)
movl %ebx,CYGARC_JMP_BUF_EBX*4(%eax)
movl %esi,CYGARC_JMP_BUF_ESI*4(%eax)
movl %edi,CYGARC_JMP_BUF_EDI*4(%eax)
# Stack and PC
movl %esp,CYGARC_JMP_BUF_SP*4(%eax)
movl 0(%esp),%edx
movl %edx,CYGARC_JMP_BUF_PC*4(%eax)
# Return 0
xor %eax,%eax
ret
# hal_longjmp loads state from 4(esp) and returns to PC stored in state
FUNC_START(hal_longjmp)
# Get return value
movl 8(%esp),%eax
# Get jmpbuf pointer
movl 4(%esp),%ecx
# Restore regular registers
movl CYGARC_JMP_BUF_EBP*4(%ecx),%ebp
movl CYGARC_JMP_BUF_EBX*4(%ecx),%ebx
movl CYGARC_JMP_BUF_ESI*4(%ecx),%esi
movl CYGARC_JMP_BUF_EDI*4(%ecx),%edi
# Restore stack pointer
movl CYGARC_JMP_BUF_SP*4(%ecx),%esp
# Put return address on stack
movl CYGARC_JMP_BUF_PC*4(%ecx),%edx
movl %edx,0(%esp)
ret
#-----------------------------------------------------------------------------
# End of context.S
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