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/* SPDX-License-Identifier: GPL-2.0 */
* wof.S: Sparc window overflow handler.
* Copyright (C) 1995 David S. Miller (
#include <asm/contregs.h>
#include <asm/page.h>
#include <asm/ptrace.h>
#include <asm/psr.h>
#include <asm/smp.h>
#include <asm/asi.h>
#include <asm/winmacro.h>
#include <asm/asmmacro.h>
#include <asm/thread_info.h>
/* WARNING: This routine is hairy and _very_ complicated, but it
* must be as fast as possible as it handles the allocation
* of register windows to the user and kernel. If you touch
* this code be _very_ careful as many other pieces of the
* kernel depend upon how this code behaves. You have been
* duly warned...
/* We define macro's for registers which have a fixed
* meaning throughout this entire routine. The 'T' in
* the comments mean that the register can only be
* accessed when in the 'trap' window, 'G' means
* accessible in any window. Do not change these registers
* after they have been set, until you are ready to return
* from the trap.
#define t_psr l0 /* %psr at trap time T */
#define t_pc l1 /* PC for trap return T */
#define t_npc l2 /* NPC for trap return T */
#define t_wim l3 /* %wim at trap time T */
#define saved_g5 l5 /* Global save register T */
#define saved_g6 l6 /* Global save register T */
#define curptr g6 /* Gets set to 'current' then stays G */
/* Now registers whose values can change within the handler. */
#define twin_tmp l4 /* Temp reg, only usable in trap window T */
#define glob_tmp g5 /* Global temporary reg, usable anywhere G */
.align 4
/* On a 7-window Sparc the boot code patches spnwin_*
* instructions with the following ones.
.globl spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win
spnwin_patch1_7win: sll %t_wim, 6, %glob_tmp
spnwin_patch2_7win: and %glob_tmp, 0x7f, %glob_tmp
spnwin_patch3_7win: and %twin_tmp, 0x7f, %twin_tmp
/* The trap entry point has done the following:
* rd %psr, %l0
* rd %wim, %l3
* b spill_window_entry
* andcc %l0, PSR_PS, %g0
/* Datum current_thread_info->uwinmask contains at all times a bitmask
* where if any user windows are active, at least one bit will
* be set in to mask. If no user windows are active, the bitmask
* will be all zeroes.
.globl spill_window_entry
.globl spnwin_patch1, spnwin_patch2, spnwin_patch3
/* LOCATION: Trap Window */
mov %g5, %saved_g5 ! save away global temp register
mov %g6, %saved_g6 ! save away 'current' ptr register
/* Compute what the new %wim will be if we save the
* window properly in this trap handler.
* newwim = ((%wim>>1) | (%wim<<(nwindows - 1)));
srl %t_wim, 0x1, %twin_tmp
spnwin_patch1: sll %t_wim, 7, %glob_tmp
or %glob_tmp, %twin_tmp, %glob_tmp
spnwin_patch2: and %glob_tmp, 0xff, %glob_tmp
/* The trap entry point has set the condition codes
* up for us to see if this is from user or kernel.
* Get the load of 'curptr' out of the way.
LOAD_CURRENT(curptr, twin_tmp)
andcc %t_psr, PSR_PS, %g0
be,a spwin_fromuser ! all user wins, branch
save %g0, %g0, %g0 ! Go where saving will occur
/* See if any user windows are active in the set. */
ld [%curptr + TI_UWINMASK], %twin_tmp ! grab win mask
orcc %g0, %twin_tmp, %g0 ! check for set bits
bne spwin_exist_uwins ! yep, there are some
andn %twin_tmp, %glob_tmp, %twin_tmp ! compute new uwinmask
/* Save into the window which must be saved and do it.
* Basically if we are here, this means that we trapped
* from kernel mode with only kernel windows in the register
* file.
save %g0, %g0, %g0 ! save into the window to stash away
wr %glob_tmp, 0x0, %wim ! set new %wim, this is safe now
/* LOCATION: Window to be saved */
STORE_WINDOW(sp) ! stash the window
restore %g0, %g0, %g0 ! go back into trap window
/* LOCATION: Trap window */
mov %saved_g5, %g5 ! restore %glob_tmp
mov %saved_g6, %g6 ! restore %curptr
wr %t_psr, 0x0, %psr ! restore condition codes in %psr
WRITE_PAUSE ! waste some time
jmp %t_pc ! Return from trap
rett %t_npc ! we are done
/* LOCATION: Trap window */
/* Wow, user windows have to be dealt with, this is dirty
* and messy as all hell. And difficult to follow if you
* are approaching the infamous register window trap handling
* problem for the first time. DON'T LOOK!
* Note that how the execution path works out, the new %wim
* will be left for us in the global temporary register,
* %glob_tmp. We cannot set the new %wim first because we
* need to save into the appropriate window without inducing
* a trap (traps are off, we'd get a watchdog wheee)...
* But first, store the new user window mask calculated
* above.
st %twin_tmp, [%curptr + TI_UWINMASK]
save %g0, %g0, %g0 ! Go to where the saving will occur
/* LOCATION: Window to be saved */
wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim
/* LOCATION: Window to be saved */
/* This instruction branches to a routine which will check
* to validity of the users stack pointer by whatever means
* are necessary. This means that this is architecture
* specific and thus this branch instruction will need to
* be patched at boot time once the machine type is known.
* This routine _shall not_ touch %curptr under any
* circumstances whatsoever! It will branch back to the
* label 'spwin_good_ustack' if the stack is ok but still
* needs to be dumped (SRMMU for instance will not need to
* do this) or 'spwin_finish_up' if the stack is ok and the
* registers have already been saved. If the stack is found
* to be bogus for some reason the routine shall branch to
* the label 'spwin_user_stack_is_bolixed' which will take
* care of things at that point.
b spwin_srmmu_stackchk
andcc %sp, 0x7, %g0
/* LOCATION: Window to be saved */
/* The users stack is ok and we can safely save it at
* %sp.
restore %g0, %g0, %g0 /* Back to trap window. */
/* LOCATION: Trap window */
/* We have spilled successfully, and we have properly stored
* the appropriate window onto the stack.
/* Restore saved globals */
mov %saved_g5, %g5
mov %saved_g6, %g6
wr %t_psr, 0x0, %psr
jmp %t_pc
rett %t_npc
/* LOCATION: Window to be saved */
/* Wheee, user has trashed his/her stack. We have to decide
* how to proceed based upon whether we came from kernel mode
* or not. If we came from kernel mode, toss the window into
* a special buffer and proceed, the kernel _needs_ a window
* and we could be in an interrupt handler so timing is crucial.
* If we came from user land we build a full stack frame and call
* c-code to gun down the process.
rd %psr, %glob_tmp
andcc %glob_tmp, PSR_PS, %g0
bne spwin_bad_ustack_from_kernel
/* Oh well, throw this one window into the per-task window
* buffer, the first one.
st %sp, [%curptr + TI_RWIN_SPTRS]
restore %g0, %g0, %g0
/* LOCATION: Trap Window */
/* Back in the trap window, update winbuffer save count. */
mov 1, %twin_tmp
st %twin_tmp, [%curptr + TI_W_SAVED]
/* Compute new user window mask. What we are basically
* doing is taking two windows, the invalid one at trap
* time and the one we attempted to throw onto the users
* stack, and saying that everything else is an ok user
* window. umask = ((~(%t_wim | %wim)) & valid_wim_bits)
rd %wim, %twin_tmp
or %twin_tmp, %t_wim, %twin_tmp
not %twin_tmp
spnwin_patch3: and %twin_tmp, 0xff, %twin_tmp ! patched on 7win Sparcs
st %twin_tmp, [%curptr + TI_UWINMASK]
sethi %hi(STACK_OFFSET), %sp
or %sp, %lo(STACK_OFFSET), %sp
add %curptr, %sp, %sp
/* Restore the saved globals and build a pt_regs frame. */
mov %saved_g5, %g5
mov %saved_g6, %g6
STORE_PT_ALL(sp, t_psr, t_pc, t_npc, g1)
sethi %hi(STACK_OFFSET), %g6
or %g6, %lo(STACK_OFFSET), %g6
sub %sp, %g6, %g6 ! curptr
/* Turn on traps and call c-code to deal with it. */
wr %t_psr, PSR_ET, %psr
call window_overflow_fault
/* Return from trap if C-code actually fixes things, if it
* doesn't then we never get this far as the process will
* be given the look of death from Commander Peanut.
b ret_trap_entry
clr %l6
/* LOCATION: Window to be saved */
/* The kernel provoked a spill window trap, but the window we
* need to save is a user one and the process has trashed its
* stack pointer. We need to be quick, so we throw it into
* a per-process window buffer until we can properly handle
* this later on.
SAVE_BOLIXED_USER_STACK(curptr, glob_tmp)
restore %g0, %g0, %g0
/* LOCATION: Trap window */
/* Restore globals, condition codes in the %psr and
* return from trap. Note, restoring %g6 when returning
* to kernel mode is not necessarily these days. ;-)
mov %saved_g5, %g5
mov %saved_g6, %g6
wr %t_psr, 0x0, %psr
jmp %t_pc
rett %t_npc
/* Undefine the register macros which would only cause trouble
* if used below. This helps find 'stupid' coding errors that
* produce 'odd' behavior. The routines below are allowed to
* make usage of glob_tmp and t_psr so we leave them defined.
#undef twin_tmp
#undef curptr
#undef t_pc
#undef t_npc
#undef t_wim
#undef saved_g5
#undef saved_g6
/* Now come the per-architecture window overflow stack checking routines.
* As noted above %curptr cannot be touched by this routine at all.
/* This is a generic SRMMU routine. As far as I know this
* works for all current v8/srmmu implementations, we'll
* see...
.globl spwin_srmmu_stackchk
/* LOCATION: Window to be saved on the stack */
/* Because of SMP concerns and speed we play a trick.
* We disable fault traps in the MMU control register,
* Execute the stores, then check the fault registers
* to see what happens. I can hear Linus now
* "disgusting... broken hardware...".
* But first, check to see if the users stack has ended
* up in kernel vma, then we would succeed for the 'wrong'
* reason... ;( Note that the 'sethi' below assumes the
* kernel is page aligned, which should always be the case.
/* Check results of callers andcc %sp, 0x7, %g0 */
bne spwin_user_stack_is_bolixed
sethi %hi(PAGE_OFFSET), %glob_tmp
cmp %glob_tmp, %sp
bleu spwin_user_stack_is_bolixed
mov AC_M_SFSR, %glob_tmp
/* Clear the fault status and turn on the no_fault bit. */
LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) ! eat SFSR
SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) ! eat SFSR
LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %glob_tmp) ! read MMU control
SUN_PI_(lda [%g0] ASI_M_MMUREGS, %glob_tmp) ! read MMU control
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. */
/* 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)
SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp)
andcc %glob_tmp, 0x2, %g0 ! did we fault?
be,a spwin_finish_up + 0x4 ! cool beans, success
restore %g0, %g0, %g0
rd %psr, %glob_tmp
b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh