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/*
* wuf.S: Window underflow trap handler for the Sparc.
*
* 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>
/* Just like the overflow handler we define macros for registers
* with fixed meanings in this routine.
*/
#define t_psr l0
#define t_pc l1
#define t_npc l2
#define t_wim l3
/* Don't touch the above registers or else you die horribly... */
/* Now macros for the available scratch registers in this routine. */
#define twin_tmp1 l4
#define twin_tmp2 l5
#define curptr g6
.text
.align 4
/* The trap entry point has executed the following:
*
* rd %psr, %l0
* rd %wim, %l3
* b fill_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.
*/
/* To get an idea of what has just happened to cause this
* trap take a look at this diagram:
*
* 1 2 3 4 <-- Window number
* ----------
* T O W I <-- Symbolic name
*
* O == the window that execution was in when
* the restore was attempted
*
* T == the trap itself has save'd us into this
* window
*
* W == this window is the one which is now invalid
* and must be made valid plus loaded from the
* stack
*
* I == this window will be the invalid one when we
* are done and return from trap if successful
*/
/* BEGINNING OF PATCH INSTRUCTIONS */
/* On 7-window Sparc the boot code patches fnwin_patch1
* with the following instruction.
*/
.globl fnwin_patch1_7win, fnwin_patch2_7win
fnwin_patch1_7win: srl %t_wim, 6, %twin_tmp2
fnwin_patch2_7win: and %twin_tmp1, 0x7f, %twin_tmp1
/* END OF PATCH INSTRUCTIONS */
.globl fill_window_entry, fnwin_patch1, fnwin_patch2
fill_window_entry:
/* LOCATION: Window 'T' */
/* Compute what the new %wim is going to be if we retrieve
* the proper window off of the stack.
*/
sll %t_wim, 1, %twin_tmp1
fnwin_patch1: srl %t_wim, 7, %twin_tmp2
or %twin_tmp1, %twin_tmp2, %twin_tmp1
fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1
wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */
andcc %t_psr, PSR_PS, %g0
be fwin_from_user
restore %g0, %g0, %g0 /* Restore to window 'O' */
/* Trapped from kernel, we trust that the kernel does not
* 'over restore' sorta speak and just grab the window
* from the stack and return. Easy enough.
*/
fwin_from_kernel:
/* LOCATION: Window 'O' */
restore %g0, %g0, %g0
/* LOCATION: Window 'W' */
LOAD_WINDOW(sp) /* Load it up */
/* Spin the wheel... */
save %g0, %g0, %g0
save %g0, %g0, %g0
/* I'd like to buy a vowel please... */
/* LOCATION: Window 'T' */
/* Now preserve the condition codes in %psr, pause, and
* return from trap. This is the simplest case of all.
*/
wr %t_psr, 0x0, %psr
WRITE_PAUSE
jmp %t_pc
rett %t_npc
fwin_from_user:
/* LOCATION: Window 'O' */
restore %g0, %g0, %g0 /* Restore to window 'W' */
/* LOCATION: Window 'W' */
/* Branch to the stack validation routine */
b srmmu_fwin_stackchk
andcc %sp, 0x7, %g0
#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
fwin_user_stack_is_bolixed:
/* LOCATION: Window 'W' */
/* Place a pt_regs frame on the kernel stack, save back
* to the trap window and call c-code to deal with this.
*/
LOAD_CURRENT(l4, l5)
sethi %hi(STACK_OFFSET), %l5
or %l5, %lo(STACK_OFFSET), %l5
add %l4, %l5, %l5
/* Store globals into pt_regs frame. */
STORE_PT_GLOBALS(l5)
STORE_PT_YREG(l5, g3)
/* Save current in a global while we change windows. */
mov %l4, %curptr
save %g0, %g0, %g0
/* LOCATION: Window 'O' */
rd %psr, %g3 /* Read %psr in live user window */
mov %fp, %g4 /* Save bogus frame pointer. */
save %g0, %g0, %g0
/* LOCATION: Window 'T' */
sethi %hi(STACK_OFFSET), %l5
or %l5, %lo(STACK_OFFSET), %l5
add %curptr, %l5, %sp
/* Build rest of pt_regs. */
STORE_PT_INS(sp)
STORE_PT_PRIV(sp, t_psr, t_pc, t_npc)
/* re-set trap time %wim value */
wr %t_wim, 0x0, %wim
/* Fix users window mask and buffer save count. */
mov 0x1, %g5
sll %g5, %g3, %g5
st %g5, [%curptr + TI_UWINMASK] ! one live user window still
st %g0, [%curptr + TI_W_SAVED] ! no windows in the buffer
wr %t_psr, PSR_ET, %psr ! enable traps
nop
call window_underflow_fault
mov %g4, %o0
b ret_trap_entry
clr %l6
fwin_user_stack_is_ok:
/* LOCATION: Window 'W' */
/* The users stack area is kosher and mapped, load the
* window and fall through to the finish up routine.
*/
LOAD_WINDOW(sp)
/* Round and round she goes... */
save %g0, %g0, %g0 /* Save to window 'O' */
save %g0, %g0, %g0 /* Save to window 'T' */
/* Where she'll trap nobody knows... */
/* LOCATION: Window 'T' */
fwin_user_finish_up:
/* LOCATION: Window 'T' */
wr %t_psr, 0x0, %psr
WRITE_PAUSE
jmp %t_pc
rett %t_npc
/* Here come the architecture specific checks for stack.
* mappings. Note that unlike the window overflow handler
* we only need to check whether the user can read from
* the appropriate addresses. Also note that we are in
* an invalid window which will be loaded, and this means
* that until we actually load the window up we are free
* to use any of the local registers contained within.
*
* On success these routine branch to fwin_user_stack_is_ok
* if the area at %sp is user readable and the window still
* needs to be loaded, else fwin_user_finish_up if the
* routine has done the loading itself. On failure (bogus
* user stack) the routine shall branch to the label called
* fwin_user_stack_is_bolixed.
*
* Contrary to the arch-specific window overflow stack
* check routines in wof.S, these routines are free to use
* any of the local registers they want to as this window
* does not belong to anyone at this point, however the
* outs and ins are still verboten as they are part of
* 'someone elses' window possibly.
*/
.globl srmmu_fwin_stackchk
srmmu_fwin_stackchk:
/* LOCATION: Window 'W' */
/* Caller did 'andcc %sp, 0x7, %g0' */
bne fwin_user_stack_is_bolixed
sethi %hi(PAGE_OFFSET), %l5
/* Check if the users stack is in kernel vma, then our
* trial and error technique below would succeed for
* the 'wrong' reason.
*/
mov AC_M_SFSR, %l4
cmp %l5, %sp
bleu fwin_user_stack_is_bolixed
lda [%l4] ASI_M_MMUREGS, %g0 ! clear fault status
/* The technique is, turn off faults on this processor,
* just let the load rip, then check the sfsr to see if
* a fault did occur. Then we turn on fault traps again
* and branch conditionally based upon what happened.
*/
lda [%g0] ASI_M_MMUREGS, %l5 ! read mmu-ctrl reg
or %l5, 0x2, %l5 ! turn on no-fault bit
sta %l5, [%g0] ASI_M_MMUREGS ! store it
/* Cross fingers and go for it. */
LOAD_WINDOW(sp)
/* A penny 'saved'... */
save %g0, %g0, %g0
save %g0, %g0, %g0
/* Is a BADTRAP earned... */
/* LOCATION: Window 'T' */
lda [%g0] ASI_M_MMUREGS, %twin_tmp1 ! load mmu-ctrl again
andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit
sta %twin_tmp1, [%g0] ASI_M_MMUREGS ! store it
mov AC_M_SFAR, %twin_tmp2
lda [%twin_tmp2] ASI_M_MMUREGS, %g0 ! read fault address
mov AC_M_SFSR, %twin_tmp2
lda [%twin_tmp2] ASI_M_MMUREGS, %twin_tmp2 ! read fault status
andcc %twin_tmp2, 0x2, %g0 ! did fault occur?
bne 1f ! yep, cleanup
nop
wr %t_psr, 0x0, %psr
nop
b fwin_user_finish_up + 0x4
nop
/* Did I ever tell you about my window lobotomy?
* anyways... fwin_user_stack_is_bolixed expects
* to be in window 'W' so make it happy or else
* we watchdog badly.
*/
1:
restore %g0, %g0, %g0
b fwin_user_stack_is_bolixed ! oh well
restore %g0, %g0, %g0
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