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Annotation of qemu/roms/openbios/arch/sparc32/wof.S, revision 1.1

1.1     ! root        1: /*
        !             2:  * Proll takes this from Sparclinux kernel, ruthlessly truncated
        !             3:  * because we have no user windows.
        !             4:  *
        !             5:  *   Copyright (C) 1995 David S. Miller ([email protected])
        !             6:  *
        !             7:  *   This program is free software; you can redistribute it and/or
        !             8:  *   modify it under the terms of the GNU General Public License
        !             9:  *   version 2 as published by the Free Software Foundation.
        !            10:  *
        !            11:  *   This program is distributed in the hope that it will be useful,
        !            12:  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
        !            13:  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        !            14:  *   GNU General Public License for more details.
        !            15:  *
        !            16:  *   You should have received a copy of the GNU General Public License
        !            17:  *   along with this program; if not, write to the Free Software
        !            18:  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
        !            19:  *   MA  02110-1301, USA.
        !            20:  *   This program is free software; you can redistribute it and/or
        !            21:  *   modify it under the terms of the GNU General Public License V2
        !            22:  *   as published by the Free Software Foundation
        !            23:  */
        !            24: 
        !            25: // #include <asm/winmacro.h>
        !            26: // #include <asm/asmmacro.h>
        !            27: 
        !            28: /* Reg_window offsets */
        !            29: #define RW_L0     0x00
        !            30: #define RW_L1     0x04
        !            31: #define RW_L2     0x08
        !            32: #define RW_L3     0x0c
        !            33: #define RW_L4     0x10
        !            34: #define RW_L5     0x14
        !            35: #define RW_L6     0x18
        !            36: #define RW_L7     0x1c
        !            37: #define RW_I0     0x20
        !            38: #define RW_I1     0x24
        !            39: #define RW_I2     0x28
        !            40: #define RW_I3     0x2c
        !            41: #define RW_I4     0x30
        !            42: #define RW_I5     0x34
        !            43: #define RW_I6     0x38
        !            44: #define RW_I7     0x3c
        !            45: 
        !            46: /* Store the register window onto the 8-byte aligned area starting
        !            47:  * at %reg.  It might be %sp, it might not, we don't care.
        !            48:  */
        !            49: #define STORE_WINDOW(reg) \
        !            50:        std     %l0, [%reg + RW_L0]; \
        !            51:        std     %l2, [%reg + RW_L2]; \
        !            52:        std     %l4, [%reg + RW_L4]; \
        !            53:        std     %l6, [%reg + RW_L6]; \
        !            54:        std     %i0, [%reg + RW_I0]; \
        !            55:        std     %i2, [%reg + RW_I2]; \
        !            56:        std     %i4, [%reg + RW_I4]; \
        !            57:        std     %i6, [%reg + RW_I6];
        !            58: 
        !            59: /* We define macro's for registers which have a fixed
        !            60:  * meaning throughout this entire routine.  The 'T' in
        !            61:  * the comments mean that the register can only be
        !            62:  * accessed when in the 'trap' window, 'G' means
        !            63:  * accessible in any window.  Do not change these registers
        !            64:  * after they have been set, until you are ready to return
        !            65:  * from the trap.
        !            66:  */
        !            67: #define t_psr       l0 /* %psr at trap time                     T */
        !            68: #define t_pc        l1 /* PC for trap return                    T */
        !            69: #define t_npc       l2 /* NPC for trap return                   T */
        !            70: #define t_wim       l3 /* %wim at trap time                     T */
        !            71: #define saved_g5    l5 /* Global save register                  T */
        !            72: #define saved_g6    l6 /* Global save register                  T */
        !            73: 
        !            74: /* Now registers whose values can change within the handler.      */
        !            75: #define twin_tmp    l4 /* Temp reg, only usable in trap window  T */
        !            76: #define glob_tmp    g5 /* Global temporary reg, usable anywhere G */
        !            77: 
        !            78:        .text
        !            79:        .align  4
        !            80: 
        !            81:        /* BEGINNING OF PATCH INSTRUCTIONS */
        !            82:        /* On a 7-window Sparc the boot code patches spnwin_*
        !            83:         * instructions with the following ones.
        !            84:         */
        !            85:        .globl  spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win
        !            86: spnwin_patch1_7win:    sll     %t_wim, 6, %glob_tmp
        !            87: spnwin_patch2_7win:    and     %glob_tmp, 0x7f, %glob_tmp
        !            88: spnwin_patch3_7win:    and     %twin_tmp, 0x7f, %twin_tmp
        !            89:        /* END OF PATCH INSTRUCTIONS */
        !            90: 
        !            91:        /* The trap entry point has done the following:
        !            92:         *
        !            93:         * rd    %psr, %l0
        !            94:         * rd    %wim, %l3
        !            95:         * b     spill_window_entry
        !            96:         * nop
        !            97:         */
        !            98: 
        !            99:        .globl  spill_window_entry
        !           100:        .globl  spnwin_patch1, spnwin_patch2
        !           101: spill_window_entry:
        !           102:        /* LOCATION: Trap Window */
        !           103: 
        !           104:        mov     %g5, %saved_g5          ! save away global temp register
        !           105:        mov     %g6, %saved_g6          ! save away 'current' ptr register
        !           106: 
        !           107:        /* Compute what the new %wim will be if we save the
        !           108:         * window properly in this trap handler.
        !           109:         *
        !           110:         * newwim = ((%wim>>1) | (%wim<<(nwindows - 1)));
        !           111:         */
        !           112:                srl     %t_wim, 0x1, %twin_tmp
        !           113: spnwin_patch1: sll     %t_wim, 7, %glob_tmp
        !           114:                or      %glob_tmp, %twin_tmp, %glob_tmp
        !           115: spnwin_patch2: and     %glob_tmp, 0xff, %glob_tmp
        !           116: 
        !           117:        /* Save into the window which must be saved and do it.
        !           118:         */
        !           119:        save    %g0, %g0, %g0           ! save into the window to stash away
        !           120:        wr      %glob_tmp, 0x0, %wim    ! set new %wim, this is safe now
        !           121: 
        !           122:        /* LOCATION: Window to be saved */
        !           123: 
        !           124:        STORE_WINDOW(sp)                ! stash the window
        !           125:        restore %g0, %g0, %g0           ! go back into trap window
        !           126: 
        !           127:        /* LOCATION: Trap window */
        !           128:        mov     %saved_g5, %g5          ! restore %glob_tmp
        !           129:        mov     %saved_g6, %g6          ! restore %curptr
        !           130:        wr      %t_psr, 0x0, %psr       ! restore condition codes in %psr
        !           131:        nop; nop; nop                   ! waste some time
        !           132:        jmp     %t_pc                   ! Return from trap
        !           133:        rett    %t_npc                  ! we are done

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