/* SPDX-License-Identifier: GPL-2.0 */
/*
 * etrap.S: Sparc trap window preparation for entry into the
 *          Linux kernel.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 */

#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>
#include <asm/asmmacro.h>
#include <asm/thread_info.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       g6 /* 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
         * nop
         */

        /* 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
        andcc   %t_psr, PSR_PS, %g0              ! fromsupv_p = (psr & PSR_PS)
        be      trap_setup_from_user             ! nope, from user mode
         sll    %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)

        /* From kernel, allocate more kernel stack and
         * build a pt_regs trap frame.
         */
        sub     %fp, (STACKFRAME_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
        bne     trap_setup_kernel_spill         ! in trap window, clean up
         nop

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

trap_setup_kernel_spill:
        ld      [%curptr + TI_UWINMASK], %g1
        orcc    %g0, %g1, %g0
        bne     trap_setup_user_spill   ! there are some user windows, yuck
        /* 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

        /* 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

#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)

trap_setup_from_user:
        /* We can't use %curptr yet. */
        LOAD_CURRENT(t_kstack, t_twinmask)

        sethi   %hi(STACK_OFFSET), %t_twinmask
        or      %t_twinmask, %lo(STACK_OFFSET), %t_twinmask
        add     %t_kstack, %t_twinmask, %t_kstack

        mov     1, %t_twinmask
        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)

#if 0
        /* If we're sure every task_struct is THREAD_SIZE aligned,
           we can speed this up. */
        sethi   %hi(STACK_OFFSET), %curptr
        or      %curptr, %lo(STACK_OFFSET), %curptr
        sub     %t_kstack, %curptr, %curptr
#else
        sethi   %hi(~(THREAD_SIZE - 1)), %curptr
        and     %t_kstack, %curptr, %curptr
#endif

        /* Clear current_thread_info->w_saved */
        st      %g0, [%curptr + TI_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 + TI_UWINMASK]    ! 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 + TI_UWINMASK]

        save    %g0, %g0, %g0

        wr      %g2, 0x0, %wim

        /* Call MMU-architecture dependent stack checking
         * routine.
         */
        b       tsetup_srmmu_stackchk
         andcc  %sp, 0x7, %g0

        /* 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  tsetup_srmmu_stackchk
tsetup_srmmu_stackchk:
        /* Check results of callers andcc %sp, 0x7, %g0 */
        bne     trap_setup_user_stack_is_bolixed
         sethi   %hi(PAGE_OFFSET), %glob_tmp

        cmp     %glob_tmp, %sp
        bleu,a  1f
LEON_PI( lda    [%g0] ASI_LEON_MMUREGS, %glob_tmp)      ! read MMU control
SUN_PI_( lda    [%g0] ASI_M_MMUREGS, %glob_tmp)         ! read MMU control

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

1:
        /* Clear the fault status and turn on the no_fault bit. */
        or      %glob_tmp, 0x2, %glob_tmp               ! or in no_fault bit
LEON_PI(sta     %glob_tmp, [%g0] ASI_LEON_MMUREGS)              ! set it
SUN_PI_(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
LEON_PI(sta     %glob_tmp, [%g0] ASI_LEON_MMUREGS)
SUN_PI_(sta     %glob_tmp, [%g0] ASI_M_MMUREGS)

        mov     AC_M_SFAR, %glob_tmp
LEON_PI(lda     [%glob_tmp] ASI_LEON_MMUREGS, %g0)
SUN_PI_(lda     [%glob_tmp] ASI_M_MMUREGS, %g0)

        mov     AC_M_SFSR, %glob_tmp
LEON_PI(lda     [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp)! save away status of winstore
SUN_PI_(lda     [%glob_tmp] ASI_M_MMUREGS, %glob_tmp)   ! save away status of winstore

        andcc   %glob_tmp, 0x2, %g0                     ! did we fault?
        bne     trap_setup_user_stack_is_bolixed        ! failure
         nop

        restore %g0, %g0, %g0

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