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/* $Id: etrap.S,v 1.1 2005-12-20 09:50:43 jcastillo Exp $
 * etrap.S: Sparc trap window preparation for entry into the
 *          Linux kernel.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 */

#include <asm/cprefix.h>
#include <asm/head.h>
#include <asm/asi.h>
#include <asm/contregs.h>
#include <asm/page.h>
#include <asm/psr.h>
#include <asm/ptrace.h>
#include <asm/winmacro.h>

/* Registers to not touch at all. */
#define t_psr        l0 /* Set by caller */
#define t_pc         l1 /* Set by caller */
#define t_npc        l2 /* Set by caller */
#define t_wim        l3 /* Set by caller */
#define t_twinmask   l4 /* Set at beginning of this entry routine. */
#define t_kstack     l5 /* Set right before pt_regs frame is built */
#define t_retpc      l6 /* If you change this, change winmacro.h header file */
#define t_systable   l7 /* Never touch this, could be the syscall table ptr. */
#define curptr       g4 /* Set after pt_regs frame is built */

        .text
        .align 4

        /* SEVEN WINDOW PATCH INSTRUCTIONS */
        .globl  tsetup_7win_patch1, tsetup_7win_patch2
        .globl  tsetup_7win_patch3, tsetup_7win_patch4
        .globl  tsetup_7win_patch5, tsetup_7win_patch6
tsetup_7win_patch1:     sll     %t_wim, 0x6, %t_wim
tsetup_7win_patch2:     and     %g2, 0x7f, %g2
tsetup_7win_patch3:     and     %g2, 0x7f, %g2
tsetup_7win_patch4:     and     %g1, 0x7f, %g1
tsetup_7win_patch5:     sll     %t_wim, 0x6, %t_wim
tsetup_7win_patch6:     and     %g2, 0x7f, %g2
        /* END OF PATCH INSTRUCTIONS */

        /* At trap time, interrupts and all generic traps do the
         * following:
         *
         * rd   %psr, %l0
         * b    some_handler
         * rd   %wim, %l3
         * nop
         *
         * Then 'some_handler' if it needs a trap frame (ie. it has
         * to call c-code and the trap cannot be handled in-window)
         * then it does the SAVE_ALL macro in entry.S which does
         *
         * sethi        %hi(trap_setup), %l4
         * jmpl         %l4 + %lo(trap_setup), %l6
         * mov          1, %l4
         */

        /* 2 3 4  window number
         * -----
         * O T S  mnemonic
         *
         * O == Current window before trap
         * T == Window entered when trap occurred
         * S == Window we will need to save if (1<<T) == %wim
         *
         * Before execution gets here, it must be guaranteed that
         * %l0 contains trap time %psr, %l1 and %l2 contain the
         * trap pc and npc, and %l3 contains the trap time %wim.
         */

        .globl  trap_setup, tsetup_patch1, tsetup_patch2
        .globl  tsetup_patch3, tsetup_patch4
        .globl  tsetup_patch5, tsetup_patch6
trap_setup:
        /* Calculate mask of trap window.  See if from user
         * or kernel and branch conditionally.
         */
        mov     1, %t_twinmask
        sll     %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
        andcc   %t_psr, PSR_PS, %g0              ! fromsupv_p = (psr & PSR_PS)
        be      trap_setup_from_user             ! nope, from user mode
         nop

        /* From kernel, allocate more kernel stack and
         * build a pt_regs trap frame.
         */
        sub     %fp, (REGWIN_SZ + TRACEREG_SZ), %t_kstack
        STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)

        /* See if we are in the trap window. */
        andcc   %t_twinmask, %t_wim, %g0
        be      1f
         nop

        b       trap_setup_kernel_spill         ! in trap window, clean up
         nop

        /* Trap from kernel with a window available.
         * Just do it...
         */
1:
        jmpl    %t_retpc + 0x8, %g0     ! return to caller
         mov    %t_kstack, %sp          ! jump onto new stack

trap_setup_kernel_spill:
        LOAD_CURRENT(curptr, g1)
        ld      [%curptr + THREAD_UMASK], %g1
        orcc    %g0, %g1, %g0
        bne     trap_setup_user_spill   ! there are some user windows, yuck
         nop

                /* Spill from kernel, but only kernel windows, adjust
                 * %wim and go.
                 */
                srl     %t_wim, 0x1, %g2        ! begin computation of new %wim
tsetup_patch1:  sll     %t_wim, 0x7, %t_wim     ! patched on 7 window Sparcs
                or      %t_wim, %g2, %g2
tsetup_patch2:  and     %g2, 0xff, %g2          ! patched on 7 window Sparcs

        save    %g0, %g0, %g0

        /* Set new %wim value */
        wr      %g2, 0x0, %wim
        WRITE_PAUSE

        /* Save the kernel window onto the corresponding stack. */
        STORE_WINDOW(sp)

        restore %g0, %g0, %g0

        jmpl    %t_retpc + 0x8, %g0     ! return to caller
         mov    %t_kstack, %sp          ! and onto new kernel stack

trap_setup_from_user:
        /* We can't use %curptr yet. */
        LOAD_CURRENT(t_kstack, t_twinmask)
        mov     1, %t_twinmask
        ld      [%t_kstack + TASK_SAVED_KSTACK], %t_kstack
        sll     %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)

        /* Build pt_regs frame. */
        STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)

        /* Clear current->tss.w_saved */
        LOAD_CURRENT(curptr, g1)
        st      %g0, [%curptr + THREAD_W_SAVED]

        /* See if we are in the trap window. */
        andcc   %t_twinmask, %t_wim, %g0
        bne     trap_setup_user_spill           ! yep we are
         orn    %g0, %t_twinmask, %g1           ! negate trap win mask into %g1

                /* Trap from user, but not into the invalid window.
                 * Calculate new umask.  The way this works is,
                 * any window from the %wim at trap time until
                 * the window right before the one we are in now,
                 * is a user window.  A diagram:
                 *
                 *      7 6 5 4 3 2 1 0    window number
                 *      ---------------
                 *        I     L T        mnemonic
                 *
                 * Window 'I' is the invalid window in our example,
                 * window 'L' is the window the user was in when
                 * the trap occurred, window T is the trap window
                 * we are in now.  So therefore, windows 5, 4 and
                 * 3 are user windows.  The following sequence
                 * computes the user winmask to represent this.
                 */
                subcc   %t_wim, %t_twinmask, %g2
                bneg,a  1f
                 sub    %g2, 0x1, %g2
1:
                andn    %g2, %t_twinmask, %g2
tsetup_patch3:  and     %g2, 0xff, %g2                  ! patched on 7win Sparcs
                st      %g2, [%curptr + THREAD_UMASK]   ! store new umask

                jmpl    %t_retpc + 0x8, %g0             ! return to caller
                 mov    %t_kstack, %sp                  ! and onto kernel stack

trap_setup_user_spill:
                /* A spill occurred from either kernel or user mode
                 * and there exist some user windows to deal with.
                 * A mask of the currently valid user windows
                 * is in %g1 upon entry to here.
                 */

tsetup_patch4:  and     %g1, 0xff, %g1          ! patched on 7win Sparcs, mask
                srl     %t_wim, 0x1, %g2        ! compute new %wim
tsetup_patch5:  sll     %t_wim, 0x7, %t_wim     ! patched on 7win Sparcs
                or      %t_wim, %g2, %g2        ! %g2 is new %wim
tsetup_patch6:  and     %g2, 0xff, %g2          ! patched on 7win Sparcs
                andn    %g1, %g2, %g1           ! clear this bit in %g1
                st      %g1, [%curptr + THREAD_UMASK]

        save    %g0, %g0, %g0

        wr      %g2, 0x0, %wim
        WRITE_PAUSE

        /* Call MMU-architecture dependent stack checking
         * routine.
         */
        .globl  C_LABEL(tsetup_mmu_patchme)
C_LABEL(tsetup_mmu_patchme):    b       C_LABEL(tsetup_sun4c_stackchk)
                                 andcc  %sp, 0x7, %g0

trap_setup_user_stack_is_bolixed:
        /* From user/kernel into invalid window w/bad user
         * stack. Save bad user stack, and return to caller.
         */
        SAVE_BOLIXED_USER_STACK(curptr, g3)
        restore %g0, %g0, %g0

        jmpl    %t_retpc + 0x8, %g0
         mov    %t_kstack, %sp

trap_setup_good_ustack:
        STORE_WINDOW(sp)

trap_setup_finish_up:
        restore %g0, %g0, %g0

        jmpl    %t_retpc + 0x8, %g0
         mov    %t_kstack, %sp

        /* Architecture specific stack checking routines.  When either
         * of these routines are called, the globals are free to use
         * as they have been safely stashed on the new kernel stack
         * pointer.  Thus the definition below for simplicity.
         */
#define glob_tmp     g1

        .globl  C_LABEL(tsetup_sun4c_stackchk)
C_LABEL(tsetup_sun4c_stackchk):
        /* Done by caller: andcc %sp, 0x7, %g0 */
        be      1f
         sra    %sp, 29, %glob_tmp

        b       trap_setup_user_stack_is_bolixed
         nop

1:
        add     %glob_tmp, 0x1, %glob_tmp
        andncc  %glob_tmp, 0x1, %g0
        be      1f
         and    %sp, 0xfff, %glob_tmp           ! delay slot

        b       trap_setup_user_stack_is_bolixed
         nop

        /* See if our dump area will be on more than one
         * page.
         */
1:
        add     %glob_tmp, 0x38, %glob_tmp
        andncc  %glob_tmp, 0xff8, %g0
        be      tsetup_sun4c_onepage            ! only one page to check
         lda    [%sp] ASI_PTE, %glob_tmp        ! have to check first page anyways

tsetup_sun4c_twopages:
        /* Is first page ok permission wise? */
        srl     %glob_tmp, 29, %glob_tmp
        cmp     %glob_tmp, 0x6
        be      1f
         add    %sp, 0x38, %glob_tmp            /* Is second page in vma hole? */

        b       trap_setup_user_stack_is_bolixed
         nop

1:
        sra     %glob_tmp, 29, %glob_tmp
        add     %glob_tmp, 0x1, %glob_tmp
        andncc  %glob_tmp, 0x1, %g0
        be      1f
         add    %sp, 0x38, %glob_tmp

        b       trap_setup_user_stack_is_bolixed
         nop

1:
        lda     [%glob_tmp] ASI_PTE, %glob_tmp

tsetup_sun4c_onepage:
        srl     %glob_tmp, 29, %glob_tmp
        cmp     %glob_tmp, 0x6                          ! can user write to it?
        be      trap_setup_good_ustack                  ! success
         nop

        b       trap_setup_user_stack_is_bolixed
         nop

        .globl  C_LABEL(tsetup_srmmu_stackchk)
C_LABEL(tsetup_srmmu_stackchk):
        /* Check results of callers andcc %sp, 0x7, %g0 */
        bne     trap_setup_user_stack_is_bolixed
         sethi  %hi(KERNBASE), %glob_tmp
        cmp     %glob_tmp, %sp
        bleu    trap_setup_user_stack_is_bolixed
         nop

        /* Clear the fault status and turn on the no_fault bit. */
        lda     [%g0] ASI_M_MMUREGS, %glob_tmp          ! read MMU control
        or      %glob_tmp, 0x2, %glob_tmp               ! or in no_fault bit
        sta     %glob_tmp, [%g0] ASI_M_MMUREGS          ! set it

        /* Dump the registers and cross fingers. */
        STORE_WINDOW(sp)

        /* Clear the no_fault bit and check the status. */
        andn    %glob_tmp, 0x2, %glob_tmp
        sta     %glob_tmp, [%g0] ASI_M_MMUREGS
        mov     AC_M_SFAR, %glob_tmp
        lda     [%glob_tmp] ASI_M_MMUREGS, %g0
        mov     AC_M_SFSR, %glob_tmp
        lda     [%glob_tmp] ASI_M_MMUREGS, %glob_tmp    ! save away status of winstore
        andcc   %glob_tmp, 0x2, %g0                     ! did we fault?
        be      trap_setup_finish_up                    ! cool beans, success
         nop

        b       trap_setup_user_stack_is_bolixed        ! we faulted, ugh
         nop