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/*  cpu_asm.s
 *
 *  This file contains all assembly code for the Intel i386 implementation
 *  of RTEMS.
 *
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.OARcorp.com/rtems/license.html.
 *
 *  $Id: cpu_asm.S,v 1.2 2001-09-27 11:59:26 chris Exp $
 */

#include <asm.h>

/*
 * Format of i386 Register structure
 */

.set REG_EFLAGS,  0
.set REG_ESP,     REG_EFLAGS + 4
.set REG_EBP,     REG_ESP + 4
.set REG_EBX,     REG_EBP + 4
.set REG_ESI,     REG_EBX + 4
.set REG_EDI,     REG_ESI + 4
.set SIZE_REGS,   REG_EDI + 4

        BEGIN_CODE

/*
 *  void _CPU_Context_switch( run_context, heir_context )
 *
 *  This routine performs a normal non-FP context.
 */

        .p2align  1
        PUBLIC (_CPU_Context_switch)

.set RUNCONTEXT_ARG,   4                   # save context argument
.set HEIRCONTEXT_ARG,  8                   # restore context argument

SYM (_CPU_Context_switch):
        movl      RUNCONTEXT_ARG(esp),eax  # eax = running threads context
        pushf                              # push eflags
        popl      REG_EFLAGS(eax)          # save eflags
        movl      esp,REG_ESP(eax)         # save stack pointer
        movl      ebp,REG_EBP(eax)         # save base pointer
        movl      ebx,REG_EBX(eax)         # save ebx
        movl      esi,REG_ESI(eax)         # save source register
        movl      edi,REG_EDI(eax)         # save destination register

        movl      HEIRCONTEXT_ARG(esp),eax # eax = heir threads context

restore:
        pushl     REG_EFLAGS(eax)          # push eflags
        popf                               # restore eflags
        movl      REG_ESP(eax),esp         # restore stack pointer
        movl      REG_EBP(eax),ebp         # restore base pointer
        movl      REG_EBX(eax),ebx         # restore ebx
        movl      REG_ESI(eax),esi         # restore source register
        movl      REG_EDI(eax),edi         # restore destination register
        ret

/*
 *  NOTE: May be unnecessary to reload some registers.
 */

/*
 *  void _CPU_Context_restore( new_context )
 *
 *  This routine performs a normal non-FP context.
 */

        PUBLIC (_CPU_Context_restore)

.set NEWCONTEXT_ARG,   4                   # context to restore argument

SYM (_CPU_Context_restore):

        movl      NEWCONTEXT_ARG(esp),eax  # eax = running threads context
        jmp       restore

/*PAGE
 *  void _CPU_Context_save_fp_context( &fp_context_ptr )
 *  void _CPU_Context_restore_fp_context( &fp_context_ptr )
 *
 *  This section is used to context switch an i80287, i80387,
 *  the built-in coprocessor or the i80486 or compatible.
 */

.set FPCONTEXT_ARG,   4                    # FP context argument

        .p2align  1
        PUBLIC (_CPU_Context_save_fp)
SYM (_CPU_Context_save_fp):
        movl      FPCONTEXT_ARG(esp),eax   # eax = &ptr to FP context area
        movl      (eax),eax                # eax = FP context area
        fsave     (eax)                    # save FP context
        ret

        .p2align  1
        PUBLIC (_CPU_Context_restore_fp)
SYM (_CPU_Context_restore_fp):
        movl      FPCONTEXT_ARG(esp),eax   # eax = &ptr to FP context area
        movl      (eax),eax                # eax = FP context area
        frstor    (eax)                    # restore FP context
        ret

        PUBLIC (_Exception_Handler)
SYM (_Exception_Handler):
        pusha                              # Push general purpose registers
        pushl   esp                        # Push exception frame address
        movl    _currentExcHandler, eax    # Call function storead in _currentExcHandler
        call    * eax
        addl    $4, esp
        popa                               # restore general purpose registers
        addl    $8, esp                    # skill vector number and faultCode
        iret
                
#define DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY(_vector) \
        .p2align 4                         ; \
        PUBLIC (rtems_exception_prologue_ ## _vector ) ; \
SYM (rtems_exception_prologue_ ## _vector ):             \
        pushl   $ _vector       ; \
        jmp   SYM (_Exception_Handler) ;

#define DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY(_vector) \
        .p2align 4                         ; \
        PUBLIC (rtems_exception_prologue_ ## _vector ) ; \
SYM (rtems_exception_prologue_ ## _vector ):             \
        pushl   $ 0             ; \
        pushl   $ _vector       ; \
        jmp   SYM (_Exception_Handler) ;

/*
 * Divide Error
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (0)
/*
 * Debug Exception
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (1)
/*
 * NMI
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (2)
/*
 * Breakpoint
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (3)
/*
 * Overflow
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (4)
/*
 * Bound Range Exceeded
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (5)
/*
 * Invalid Opcode
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (6)
/*
 * No Math Coproc
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (7)
/*
 * Double Fault
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (8)
/*
 * Coprocessor segment overrun
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (9)
/*
 * Invalid TSS
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (10)
/*
 * Segment Not Present
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (11)
/*
 * Stack segment Fault
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (12)
/*
 * General Protection Fault
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (13)
/*
 * Page Fault
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (14)
/*
 * Floating point error (NB 15 is reserved it is therefor skipped)
 */     
DISTINCT_EXCEPTION_WITHOUT_FAULTCODE_ENTRY (16)
/*
 * Aligment Check
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (17)
/*
 * Machine Check
 */     
DISTINCT_EXCEPTION_WITH_FAULTCODE_ENTRY (18)
        

/*
 *  void *i386_Logical_to_physical(
 *     rtems_unsigned16  segment,
 *     void             *address
 *  );
 *
 *  Returns thirty-two bit physical address for segment:address.
 */

.set SEGMENT_ARG, 4
.set ADDRESS_ARG, 8

             PUBLIC (i386_Logical_to_physical)

SYM (i386_Logical_to_physical):

        xorl    eax,eax                # clear eax
        movzwl  SEGMENT_ARG(esp),ecx   # ecx = segment value
        movl    $ SYM (_Global_descriptor_table),edx
                                       # edx = address of our GDT
        addl    ecx,edx                # edx = address of desired entry
        movb    7(edx),ah              # ah = base 31:24
        movb    4(edx),al              # al = base 23:16
        shll    $16,eax                # move ax into correct bits
        movw    2(edx),ax              # ax = base 0:15
        movl    ADDRESS_ARG(esp),ecx   # ecx = address to convert
        addl    eax,ecx                # ecx = physical address equivalent
        movl    ecx,eax                # eax = ecx
        ret

/*
 *  void *i386_Physical_to_logical(
 *     rtems_unsigned16  segment,
 *     void             *address
 *  );
 *
 *  Returns thirty-two bit physical address for segment:address.
 */

/*
 *.set SEGMENT_ARG, 4
 *.set ADDRESS_ARG, 8   -- use sets from above
 */

       PUBLIC (i386_Physical_to_logical)

SYM (i386_Physical_to_logical):
        xorl    eax,eax                # clear eax
        movzwl  SEGMENT_ARG(esp),ecx   # ecx = segment value
        movl    $ SYM (_Global_descriptor_table),edx
                                       # edx = address of our GDT
        addl    ecx,edx                # edx = address of desired entry
        movb    7(edx),ah              # ah = base 31:24
        movb    4(edx),al              # al = base 23:16
        shll    $16,eax                # move ax into correct bits
        movw    2(edx),ax              # ax = base 0:15
        movl    ADDRESS_ARG(esp),ecx   # ecx = address to convert
        subl    eax,ecx                # ecx = logical address equivalent
        movl    ecx,eax                # eax = ecx
        ret

END_CODE

END