FreeBSD/Linux Kernel Cross Reference
sys/powerpc/ofw/ofwcall32.S

     /*-
      * Copyright (C) 2009-2011 Nathan Whitehorn
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. 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.
     *
     * 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 TOOLS GMBH 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.
     *
     * $FreeBSD: releng/11.1/sys/powerpc/ofw/ofwcall32.S 279750 2015-03-07 20:14:46Z nwhitehorn $
     */
    
    #include <sys/syscall.h>
    
    #include <machine/trap.h>
    #include <machine/param.h>
    #include <machine/spr.h>
    #include <machine/asm.h>
    
    #define OFWSTKSZ        4096            /* 4K Open Firmware stack */
    
    /*
     * Globals
     */
            .data
    GLOBAL(ofmsr)
            .long   0, 0, 0, 0, 0           /* msr/sprg0-3 used in Open Firmware */
    GLOBAL(rtasmsr)
            .long   0
    GLOBAL(openfirmware_entry)
            .long   0                       /* Open Firmware entry point */
    GLOBAL(rtas_entry)
            .long   0                       /* RTAS entry point */
    
            .align  4
    ofwstk:
            .space  OFWSTKSZ
    rtas_regsave:
            .space  4
    
    /*
     * Open Firmware Entry Point. May need to enter real mode.
     *
     * C prototype: int ofwcall(void *callbuffer);
     */
    
    ASENTRY(ofwcall)
            mflr    %r0
            stw     %r0,4(%r1)
    
            /* Record the old MSR */
            mfmsr   %r6
    
            /* GOT pointer in r7 */
            bl      _GLOBAL_OFFSET_TABLE_@local-4
            mflr    %r7
    
            /* read client interface handler */
            lwz     %r4,openfirmware_entry@got(%r7)
            lwz     %r4,0(%r4)
    
            /*
             * Set the MSR to the OF value. This has the side effect of disabling
             * exceptions, which prevents preemption later.
             */
    
            lwz     %r5,ofmsr@got(%r7)
            lwz     %r5,0(%r5)
            mtmsr   %r5
            isync
    
            /*
             * Set up OF stack. This needs to be potentially accessible in real mode
             * The pointer to the current kernel stack is placed at the very
             * top of the stack along with the old MSR so we can get them back
             * later.
             */
            mr      %r5,%r1
            lwz     %r1,ofwstk@got(%r7)
            addi    %r1,%r1,(OFWSTKSZ-32)
            stw     %r5,20(%r1)     /* Save real stack pointer */
            stw     %r2,24(%r1)     /* Save curthread */
            stw     %r6,28(%r1)     /* Save old MSR */
            li      %r5,0
           stw     %r5,4(%r1)
           stw     %r5,0(%r1)
   
           /* Finally, branch to OF */
           mtctr   %r4
           bctrl
   
           /* Reload stack pointer and MSR from the OFW stack */
           lwz     %r6,28(%r1)
           lwz     %r2,24(%r1)
           lwz     %r1,20(%r1)
   
           /* Now set the real MSR */
           mtmsr   %r6
           isync
   
           /* Return */
           lwz     %r0,4(%r1)
           mtlr    %r0
           blr
   
   /*
    * RTAS Entry Point. Similar to the OF one, but simpler (no separate stack)
    *
    * C prototype: int rtascall(void *callbuffer, void *rtas_privdat);
    */
   
   ASENTRY(rtascall)
           mflr    %r0
           stw     %r0,4(%r1)
   
           /* GOT pointer in r7 */
           bl      _GLOBAL_OFFSET_TABLE_@local-4
           mflr    %r7
   
           /* Record the old MSR to real-mode-accessible area */
           mfmsr   %r0
           lwz     %r5,rtas_regsave@got(%r7)
           stw     %r0,0(%r5)
   
           /* read client interface handler */
           lwz     %r5,rtas_entry@got(%r7)
           lwz     %r5,0(%r5)
   
           /* Set the MSR to the RTAS value */
           lwz     %r6,rtasmsr@got(%r7)
           lwz     %r6,0(%r6)
           mtmsr   %r6
           isync
   
           /* Branch to RTAS */
           mtctr   %r5
           bctrl
   
           /* GOT pointer in r7 */
           bl      _GLOBAL_OFFSET_TABLE_@local-4
           mflr    %r7
   
           /* Now set the MSR back */
           lwz     %r6,rtas_regsave@got(%r7)
           lwz     %r6,0(%r6)
           mtmsr   %r6
           isync
   
           /* And return */
           lwz     %r0,4(%r1)
           mtlr    %r0
           blr
   

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