source: rtems/c/src/lib/libbsp/i386/shared/irq/irq_asm.S @ 4a4201c

/* irq.c
 *
 *  This file contains the implementation of the function described in irq.h
 *
 *  CopyRight (C) 1998 valette@crf.canon.fr
 *
 *  The license and distribution terms for this file may be
 *  found in found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  $Id$
 */

#include <rtems/asm.h>
#include <bsp/irq_asm.h>
#include <rtems/score/cpu.h>

#ifndef CPU_STACK_ALIGNMENT
#error "Missing header? CPU_STACK_ALIGNMENT is not defined here"
#endif

/* Stack frame we use for intermediate storage               */
#define ARG_OFF 0
#define MSK_OFF 4
#define EBP_OFF 8        /* code restoring ebp/esp relies on */
#define ESP_OFF 12       /* esp being on top of ebp!         */
#ifdef __SSE__
#define FRM_SIZ (16+512)
#define SSE_OFF 16
#else
#define FRM_SIZ 16 
#endif

        BEGIN_CODE

SYM (_ISR_Handler):
        /*
         *  Before this was point is reached the vectors unique
         *  entry point did the following:
         *
         *     1. saved scratch registers registers eax edx ecx"
         *     2. put the vector number in ecx.
         *
         * BEGINNING OF ESTABLISH SEGMENTS
         *
         *  WARNING: If an interrupt can occur when the segments are
         *           not correct, then this is where we should establish
         *           the segments.  In addition to establishing the
         *           segments, it may be necessary to establish a stack
         *           in the current data area on the outermost interrupt.
         *
         *  NOTE:  If the previous values of the segment registers are
         *         pushed, do not forget to adjust SAVED_REGS.
         *
         *  NOTE:  Make sure the exit code which restores these
         *         when this type of code is needed.
         */

        /***** ESTABLISH SEGMENTS CODE GOES HERE  ******/

        /*
         * END OF ESTABLISH SEGMENTS
         */

        /*
         * Establish an aligned stack frame
         *   original-sp
         *   saved-bp
         *   saved-irq-mask
         *   vector-arg-to-C_dispatch_isr   <- aligned SP
         */
        movl      esp, eax
        subl      $FRM_SIZ, esp
        andl      $ - CPU_STACK_ALIGNMENT, esp
        movl      eax, ESP_OFF(esp)
        movl      ebp, EBP_OFF(esp)

#ifdef __SSE__
        /* NOTE: SSE only is supported if the BSP enables fxsave/fxrstor
         * to save/restore SSE context! This is so far only implemented
         * for pc386!.
         */

        /* We save SSE here (on the task stack) because we possibly
         * call other C-code (besides the ISR, namely _Thread_Dispatch()
         * or _ThreadProcessSignalsFromIrq()).
         */
    /*  don't wait here; a possible exception condition will eventually be
     *  detected when the task resumes control and executes a FP instruction
        fwait
     */
        fxsave SSE_OFF(esp)
        fninit                          /* clean-slate FPU                */
        movl   $0x1f80, ARG_OFF(esp)    /* use ARG_OFF as scratch space   */
        ldmxcsr ARG_OFF(esp)            /* clean-slate MXCSR              */
#endif


        /*
         * acknowledge the interrupt
         *
         */
        movw      SYM (i8259s_cache), ax /* move current i8259 interrupt mask in ax */
        movl      eax, MSK_OFF(esp)      /* save in stack frame */
        /*
         * compute the new PIC mask:
         *
         * <new mask> = <old mask> | irq_mask_or_tbl[<intr number aka ecx>]
         */
        movw      SYM (irq_mask_or_tbl) (,ecx,2), dx
        orw       dx, ax
        /*
         * Install new computed value on the i8259 and update cache
         * accordingly
         */
        movw      ax, SYM (i8259s_cache)
        outb      $PIC_MASTER_IMR_IO_PORT
        movb      ah, al
        outb      $PIC_SLAVE_IMR_IO_PORT

        movb      $PIC_EOI, al
        cmpl      $7, ecx
        jbe      .master
        outb      $PIC_SLAVE_COMMAND_IO_PORT
.master:
        outb      $PIC_MASTER_COMMAND_IO_PORT

        /*
         *  Now switch stacks if necessary
         */

.check_stack_switch:
        movl      esp, ebp                  /* ebp = previous stack pointer */
        cmpl      $0, SYM (_ISR_Nest_level) /* is this the outermost interrupt? */
        jne       nested                    /* No, then continue */
        movl      SYM (_CPU_Interrupt_stack_high), esp

        /*
         *  We want to insure that the old stack pointer is in ebp
         *  By saving it on every interrupt, all we have to do is 
         *  movl ebp->esp near the end of every interrupt.
         */

nested:
        incl      SYM (_ISR_Nest_level)     /* one nest level deeper */
        incl      SYM (_Thread_Dispatch_disable_level) /* disable multitasking */

        /*
         * re-enable interrupts at processor level as the current
         * interrupt source is now masked via i8259
         */
        sti

    /*
         *  ECX is preloaded with the vector number; store as arg
         *  on top of stack. Note that _CPU_Interrupt_stack_high
         *  was adjusted in _CPU_Interrupt_stack_setup() (score/rtems/cpu.h)
         *  to make sure there is space.
         */

        movl      ecx, ARG_OFF(esp)  /* store vector arg in stack */
        call      C_dispatch_isr

        /*
         * disable interrupts_again
         */
        cli

        /*
         * Restore stack. This moves back to the task stack
         * when all interrupts are unnested.
         */
        movl      ebp, esp

        /*
         * restore the original i8259 masks
         */
        movl      MSK_OFF(esp), eax
        movw      ax, SYM (i8259s_cache)
        outb      $PIC_MASTER_IMR_IO_PORT
        movb      ah, al
        outb      $PIC_SLAVE_IMR_IO_PORT

        decl      SYM (_ISR_Nest_level)     /* one less ISR nest level */
                                            /* If interrupts are nested, */
                                            /*   then dispatching is disabled */

        decl      SYM (_Thread_Dispatch_disable_level)
                                            /* unnest multitasking */
                                            /* Is dispatch disabled */
        jne       .exit                     /* Yes, then exit */

        cmpb      $0, SYM (_Context_Switch_necessary)
                                            /* Is task switch necessary? */
        jne       .schedule                 /* Yes, then call the scheduler */

        cmpb      $0, SYM (_ISR_Signals_to_thread_executing)
                                            /* signals sent to Run_thread */
                                            /*   while in interrupt handler? */
        je        .exit                     /* No, exit */

.bframe:
        movb      $0, SYM (_ISR_Signals_to_thread_executing)
        /*
         * This code is the less critical path. In order to have a single
         * Thread Context, we take the same frame than the one pushed on
         * exceptions. This makes sense because Signal is a software
         * exception.
         */
        call      _ThreadProcessSignalsFromIrq

        jmp       .exit

.schedule:
        /*
         * the scratch registers have already been saved and we are already
         * back on the thread system stack. So we can call _Thread_Displatch
         * directly
         */
        call      _Thread_Dispatch
        /*
         * fall through exit to restore complete contex (scratch registers
         * eip, CS, Flags).
         */
.exit:

#ifdef __SSE__
        fwait
        fxrstor   SSE_OFF(esp)
#endif

        /* restore ebp and original esp */
        addl      $EBP_OFF, esp
        popl      ebp
        popl      esp
        /*
         * BEGINNING OF DE-ESTABLISH SEGMENTS
         *
         *  NOTE:  Make sure there is code here if code is added to
         *         load the segment registers.
         *
         */

        /******* DE-ESTABLISH SEGMENTS CODE GOES HERE ********/

        /*
         * END OF DE-ESTABLISH SEGMENTS
         */
        popl      edx
        popl      ecx
        popl      eax
        iret

#define DISTINCT_INTERRUPT_ENTRY(_vector) \
        .p2align 4                         ; \
        PUBLIC (rtems_irq_prologue_ ## _vector ) ; \
SYM (rtems_irq_prologue_ ## _vector ):             \
        pushl     eax                ; \
        pushl     ecx                ; \
        pushl     edx                ; \
        movl      $ _vector, ecx     ; \
        jmp       SYM (_ISR_Handler) ;

DISTINCT_INTERRUPT_ENTRY(0)
DISTINCT_INTERRUPT_ENTRY(1)
DISTINCT_INTERRUPT_ENTRY(2)
DISTINCT_INTERRUPT_ENTRY(3)
DISTINCT_INTERRUPT_ENTRY(4)
DISTINCT_INTERRUPT_ENTRY(5)
DISTINCT_INTERRUPT_ENTRY(6)
DISTINCT_INTERRUPT_ENTRY(7)
DISTINCT_INTERRUPT_ENTRY(8)
DISTINCT_INTERRUPT_ENTRY(9)
DISTINCT_INTERRUPT_ENTRY(10)
DISTINCT_INTERRUPT_ENTRY(11)
DISTINCT_INTERRUPT_ENTRY(12)
DISTINCT_INTERRUPT_ENTRY(13)
DISTINCT_INTERRUPT_ENTRY(14)
DISTINCT_INTERRUPT_ENTRY(15)

        /*
         * routine used to initialize the IDT by default
         */

PUBLIC (default_raw_idt_handler)
PUBLIC (raw_idt_notify)

SYM (default_raw_idt_handler):
        pusha
        cld
        mov       esp, ebp
        andl     $ - CPU_STACK_ALIGNMENT, esp
        call      raw_idt_notify
        mov       ebp, esp
        popa
        iret

END_CODE

END