[deliverable/linux.git] / arch / sparc / kernel / wof.S

/*
 * wof.S: Sparc window overflow handler.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 */

#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 */

	.text
	.align	4
	/* BEGINNING OF PATCH INSTRUCTIONS */
	/* 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
	/* END OF PATCH INSTRUCTIONS */

	/* 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
spill_window_entry:
	/* 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

spwin_no_userwins_from_kernel:
	/* 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

spwin_exist_uwins:
	/* 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

spwin_fromuser:
	/* 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.
	 */
	.globl	spwin_mmu_patchme
spwin_mmu_patchme:	b	spwin_sun4c_stackchk
				 andcc	%sp, 0x7, %g0

spwin_good_ustack:
	/* LOCATION: Window to be saved */

	/* The users stack is ok and we can safely save it at
	 * %sp.
	 */
	STORE_WINDOW(sp)

spwin_finish_up:
	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
	WRITE_PAUSE
	jmp	%t_pc
	rett	%t_npc

spwin_user_stack_is_bolixed:
	/* 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
	 nop

	/* Oh well, throw this one window into the per-task window
	 * buffer, the first one.
	 */
	st	%sp, [%curptr + TI_RWIN_SPTRS]
	STORE_WINDOW(curptr + TI_REG_WINDOW)
	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]

#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)

	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
	nop
	call	window_overflow_fault
	 nop

	/* 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

spwin_bad_ustack_from_kernel:
	/* 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
	WRITE_PAUSE

	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.
 */

spwin_sun4c_stackchk:
	/* LOCATION: Window to be saved on the stack */

	/* See if the stack is in the address space hole but first,
	 * check results of callers andcc %sp, 0x7, %g0
	 */
	be	1f
	 sra	%sp, 29, %glob_tmp

	rd	%psr, %glob_tmp
	b	spwin_user_stack_is_bolixed + 0x4
	 nop

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

	rd	%psr, %glob_tmp
	b	spwin_user_stack_is_bolixed + 0x4
	 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	spwin_sun4c_onepage		! only one page to check
	 lda	[%sp] ASI_PTE, %glob_tmp	! have to check first page anyways

spwin_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? */

	rd	%psr, %glob_tmp
	b	spwin_user_stack_is_bolixed + 0x4
	 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

	rd	%psr, %glob_tmp
	b	spwin_user_stack_is_bolixed + 0x4
	 nop

1:
	lda	[%glob_tmp] ASI_PTE, %glob_tmp

spwin_sun4c_onepage:
	srl	%glob_tmp, 29, %glob_tmp
	cmp	%glob_tmp, 0x6				! can user write to it?
	be	spwin_good_ustack			! success
	 nop

	rd	%psr, %glob_tmp
	b	spwin_user_stack_is_bolixed + 0x4
	 nop

	/* 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
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. */
	lda	[%glob_tmp] ASI_M_MMUREGS, %g0		! eat SFSR

	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
	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
	 nop
Commit	Line	Data
88278ca2	1	/*
1da177e4 LT	2	* wof.S: Sparc window overflow handler.
	3	*
	4	* Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
	5	*/
	6
	7	#include <asm/contregs.h>
	8	#include <asm/page.h>
	9	#include <asm/ptrace.h>
	10	#include <asm/psr.h>
	11	#include <asm/smp.h>
	12	#include <asm/asi.h>
	13	#include <asm/winmacro.h>
	14	#include <asm/asmmacro.h>
	15	#include <asm/thread_info.h>
	16
	17	/* WARNING: This routine is hairy and _very_ complicated, but it
	18	* must be as fast as possible as it handles the allocation
	19	* of register windows to the user and kernel. If you touch
	20	* this code be _very_ careful as many other pieces of the
	21	* kernel depend upon how this code behaves. You have been
	22	* duly warned...
	23	*/
	24
	25	/* We define macro's for registers which have a fixed
	26	* meaning throughout this entire routine. The 'T' in
	27	* the comments mean that the register can only be
	28	* accessed when in the 'trap' window, 'G' means
	29	* accessible in any window. Do not change these registers
	30	* after they have been set, until you are ready to return
	31	* from the trap.
	32	*/
	33	#define t_psr l0 /* %psr at trap time T */
	34	#define t_pc l1 /* PC for trap return T */
	35	#define t_npc l2 /* NPC for trap return T */
	36	#define t_wim l3 /* %wim at trap time T */
	37	#define saved_g5 l5 /* Global save register T */
	38	#define saved_g6 l6 /* Global save register T */
	39	#define curptr g6 /* Gets set to 'current' then stays G */
	40
	41	/* Now registers whose values can change within the handler. */
	42	#define twin_tmp l4 /* Temp reg, only usable in trap window T */
	43	#define glob_tmp g5 /* Global temporary reg, usable anywhere G */
	44
	45	.text
	46	.align 4
	47	/* BEGINNING OF PATCH INSTRUCTIONS */
	48	/* On a 7-window Sparc the boot code patches spnwin_*
	49	* instructions with the following ones.
	50	*/
	51	.globl spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win
	52	spnwin_patch1_7win: sll %t_wim, 6, %glob_tmp
	53	spnwin_patch2_7win: and %glob_tmp, 0x7f, %glob_tmp
	54	spnwin_patch3_7win: and %twin_tmp, 0x7f, %twin_tmp
	55	/* END OF PATCH INSTRUCTIONS */
	56
	57	/* The trap entry point has done the following:
	58	*
	59	* rd %psr, %l0
	60	* rd %wim, %l3
	61	* b spill_window_entry
	62	* andcc %l0, PSR_PS, %g0
	63	*/
	64
	65	/* Datum current_thread_info->uwinmask contains at all times a bitmask
66	* where if any user windows are active, at least one bit will
67	* be set in to mask. If no user windows are active, the bitmask
68	* will be all zeroes.
69	*/
70	.globl spill_window_entry
71	.globl spnwin_patch1, spnwin_patch2, spnwin_patch3
72	spill_window_entry:
73	/* LOCATION: Trap Window */
74
75	mov %g5, %saved_g5 ! save away global temp register
76	mov %g6, %saved_g6 ! save away 'current' ptr register
77
78	/* Compute what the new %wim will be if we save the
79	* window properly in this trap handler.
80	*
81	* newwim = ((%wim>>1) \| (%wim<<(nwindows - 1)));
82	*/
83	srl %t_wim, 0x1, %twin_tmp
84	spnwin_patch1: sll %t_wim, 7, %glob_tmp
85	or %glob_tmp, %twin_tmp, %glob_tmp
86	spnwin_patch2: and %glob_tmp, 0xff, %glob_tmp
87
88	/* The trap entry point has set the condition codes
89	* up for us to see if this is from user or kernel.
90	* Get the load of 'curptr' out of the way.
91	*/
92	LOAD_CURRENT(curptr, twin_tmp)
93
94	andcc %t_psr, PSR_PS, %g0
95	be,a spwin_fromuser ! all user wins, branch
96	save %g0, %g0, %g0 ! Go where saving will occur
97
98	/* See if any user windows are active in the set. */
99	ld [%curptr + TI_UWINMASK], %twin_tmp ! grab win mask
100	orcc %g0, %twin_tmp, %g0 ! check for set bits
101	bne spwin_exist_uwins ! yep, there are some
102	andn %twin_tmp, %glob_tmp, %twin_tmp ! compute new uwinmask
103
104	/* Save into the window which must be saved and do it.
105	* Basically if we are here, this means that we trapped
106	* from kernel mode with only kernel windows in the register
107	* file.
108	*/
109	save %g0, %g0, %g0 ! save into the window to stash away
110	wr %glob_tmp, 0x0, %wim ! set new %wim, this is safe now
111
112	spwin_no_userwins_from_kernel:
113	/* LOCATION: Window to be saved */
114
115	STORE_WINDOW(sp) ! stash the window
116	restore %g0, %g0, %g0 ! go back into trap window
117
118	/* LOCATION: Trap window */
119	mov %saved_g5, %g5 ! restore %glob_tmp
120	mov %saved_g6, %g6 ! restore %curptr
121	wr %t_psr, 0x0, %psr ! restore condition codes in %psr
122	WRITE_PAUSE ! waste some time
123	jmp %t_pc ! Return from trap
124	rett %t_npc ! we are done
125
126	spwin_exist_uwins:
127	/* LOCATION: Trap window */
128
129	/* Wow, user windows have to be dealt with, this is dirty
130	* and messy as all hell. And difficult to follow if you
131	* are approaching the infamous register window trap handling
132	* problem for the first time. DON'T LOOK!
133	*
134	* Note that how the execution path works out, the new %wim
135	* will be left for us in the global temporary register,
136	* %glob_tmp. We cannot set the new %wim first because we
137	* need to save into the appropriate window without inducing
138	* a trap (traps are off, we'd get a watchdog wheee)...
139	* But first, store the new user window mask calculated
140	* above.
141	*/
142	st %twin_tmp, [%curptr + TI_UWINMASK]
143	save %g0, %g0, %g0 ! Go to where the saving will occur
144
145	spwin_fromuser:
146	/* LOCATION: Window to be saved */
147	wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim
148
149	/* LOCATION: Window to be saved */
150
151	/* This instruction branches to a routine which will check
152	* to validity of the users stack pointer by whatever means
153	* are necessary. This means that this is architecture
154	* specific and thus this branch instruction will need to
155	* be patched at boot time once the machine type is known.
156	* This routine _shall not_ touch %curptr under any
157	* circumstances whatsoever! It will branch back to the
158	* label 'spwin_good_ustack' if the stack is ok but still
159	* needs to be dumped (SRMMU for instance will not need to
160	* do this) or 'spwin_finish_up' if the stack is ok and the
161	* registers have already been saved. If the stack is found
162	* to be bogus for some reason the routine shall branch to
163	* the label 'spwin_user_stack_is_bolixed' which will take
164	* care of things at that point.
165	*/
166	.globl spwin_mmu_patchme
167	spwin_mmu_patchme: b spwin_sun4c_stackchk
168	andcc %sp, 0x7, %g0
169
170	spwin_good_ustack:
171	/* LOCATION: Window to be saved */
172
173	/* The users stack is ok and we can safely save it at
174	* %sp.
175	*/
176	STORE_WINDOW(sp)
177
178	spwin_finish_up:
179	restore %g0, %g0, %g0 /* Back to trap window. */
180
181	/* LOCATION: Trap window */
182
183	/* We have spilled successfully, and we have properly stored
184	* the appropriate window onto the stack.
185	*/
186
187	/* Restore saved globals */
188	mov %saved_g5, %g5
189	mov %saved_g6, %g6
190
191	wr %t_psr, 0x0, %psr
192	WRITE_PAUSE
193	jmp %t_pc
194	rett %t_npc
195
196	spwin_user_stack_is_bolixed:
197	/* LOCATION: Window to be saved */
198
199	/* Wheee, user has trashed his/her stack. We have to decide
200	* how to proceed based upon whether we came from kernel mode
201	* or not. If we came from kernel mode, toss the window into
202	* a special buffer and proceed, the kernel _needs_ a window
203	* and we could be in an interrupt handler so timing is crucial.
204	* If we came from user land we build a full stack frame and call
205	* c-code to gun down the process.
206	*/
207	rd %psr, %glob_tmp
208	andcc %glob_tmp, PSR_PS, %g0
209	bne spwin_bad_ustack_from_kernel
210	nop
211
212	/* Oh well, throw this one window into the per-task window
213	* buffer, the first one.
214	*/
215	st %sp, [%curptr + TI_RWIN_SPTRS]
216	STORE_WINDOW(curptr + TI_REG_WINDOW)
217	restore %g0, %g0, %g0
218
219	/* LOCATION: Trap Window */
220
221	/* Back in the trap window, update winbuffer save count. */
222	mov 1, %twin_tmp
223	st %twin_tmp, [%curptr + TI_W_SAVED]
224
225	/* Compute new user window mask. What we are basically
226	* doing is taking two windows, the invalid one at trap
227	* time and the one we attempted to throw onto the users
228	* stack, and saying that everything else is an ok user
229	* window. umask = ((~(%t_wim \| %wim)) & valid_wim_bits)
230	*/
231	rd %wim, %twin_tmp
232	or %twin_tmp, %t_wim, %twin_tmp
233	not %twin_tmp
234	spnwin_patch3: and %twin_tmp, 0xff, %twin_tmp ! patched on 7win Sparcs
235	st %twin_tmp, [%curptr + TI_UWINMASK]
236
237	#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
238
239	sethi %hi(STACK_OFFSET), %sp
240	or %sp, %lo(STACK_OFFSET), %sp
241	add %curptr, %sp, %sp
242
243	/* Restore the saved globals and build a pt_regs frame. */
244	mov %saved_g5, %g5
245	mov %saved_g6, %g6
246	STORE_PT_ALL(sp, t_psr, t_pc, t_npc, g1)
247
248	sethi %hi(STACK_OFFSET), %g6
249	or %g6, %lo(STACK_OFFSET), %g6
250	sub %sp, %g6, %g6 ! curptr
251
252	/* Turn on traps and call c-code to deal with it. */
253	wr %t_psr, PSR_ET, %psr
254	nop
255	call window_overflow_fault
256	nop
257
258	/* Return from trap if C-code actually fixes things, if it
259	* doesn't then we never get this far as the process will
260	* be given the look of death from Commander Peanut.
261	*/
262	b ret_trap_entry
263	clr %l6
264
265	spwin_bad_ustack_from_kernel:
266	/* LOCATION: Window to be saved */
267
268	/* The kernel provoked a spill window trap, but the window we
269	* need to save is a user one and the process has trashed its
270	* stack pointer. We need to be quick, so we throw it into
271	* a per-process window buffer until we can properly handle
272	* this later on.
273	*/
274	SAVE_BOLIXED_USER_STACK(curptr, glob_tmp)
275	restore %g0, %g0, %g0
276
277	/* LOCATION: Trap window */
278
279	/* Restore globals, condition codes in the %psr and
280	* return from trap. Note, restoring %g6 when returning
281	* to kernel mode is not necessarily these days. ;-)
282	*/
283	mov %saved_g5, %g5
284	mov %saved_g6, %g6
285
286	wr %t_psr, 0x0, %psr
287	WRITE_PAUSE
288
289	jmp %t_pc
290	rett %t_npc
291
292	/* Undefine the register macros which would only cause trouble
293	* if used below. This helps find 'stupid' coding errors that
294	* produce 'odd' behavior. The routines below are allowed to
295	* make usage of glob_tmp and t_psr so we leave them defined.
296	*/
297	#undef twin_tmp
298	#undef curptr
299	#undef t_pc
300	#undef t_npc
301	#undef t_wim
302	#undef saved_g5
303	#undef saved_g6
304
305	/* Now come the per-architecture window overflow stack checking routines.
306	* As noted above %curptr cannot be touched by this routine at all.
307	*/
308
1da177e4 LT	309	spwin_sun4c_stackchk:
	310	/* LOCATION: Window to be saved on the stack */
	311
	312	/* See if the stack is in the address space hole but first,
	313	* check results of callers andcc %sp, 0x7, %g0
	314	*/
	315	be 1f
	316	sra %sp, 29, %glob_tmp
	317
	318	rd %psr, %glob_tmp
	319	b spwin_user_stack_is_bolixed + 0x4
	320	nop
	321
	322	1:
	323	add %glob_tmp, 0x1, %glob_tmp
	324	andncc %glob_tmp, 0x1, %g0
	325	be 1f
	326	and %sp, 0xfff, %glob_tmp ! delay slot
	327
	328	rd %psr, %glob_tmp
	329	b spwin_user_stack_is_bolixed + 0x4
	330	nop
	331
	332	/* See if our dump area will be on more than one
	333	* page.
	334	*/
	335	1:
	336	add %glob_tmp, 0x38, %glob_tmp
	337	andncc %glob_tmp, 0xff8, %g0
	338	be spwin_sun4c_onepage ! only one page to check
	339	lda [%sp] ASI_PTE, %glob_tmp ! have to check first page anyways
	340
	341	spwin_sun4c_twopages:
	342	/* Is first page ok permission wise? */
	343	srl %glob_tmp, 29, %glob_tmp
	344	cmp %glob_tmp, 0x6
	345	be 1f
	346	add %sp, 0x38, %glob_tmp /* Is second page in vma hole? */
	347
	348	rd %psr, %glob_tmp
	349	b spwin_user_stack_is_bolixed + 0x4
	350	nop
	351
	352	1:
	353	sra %glob_tmp, 29, %glob_tmp
	354	add %glob_tmp, 0x1, %glob_tmp
	355	andncc %glob_tmp, 0x1, %g0
	356	be 1f
	357	add %sp, 0x38, %glob_tmp
	358
	359	rd %psr, %glob_tmp
	360	b spwin_user_stack_is_bolixed + 0x4
	361	nop
	362
	363	1:
	364	lda [%glob_tmp] ASI_PTE, %glob_tmp
	365
	366	spwin_sun4c_onepage:
	367	srl %glob_tmp, 29, %glob_tmp
	368	cmp %glob_tmp, 0x6 ! can user write to it?
	369	be spwin_good_ustack ! success
	370	nop
	371
	372	rd %psr, %glob_tmp
373	b spwin_user_stack_is_bolixed + 0x4
374	nop
375
376	/* This is a generic SRMMU routine. As far as I know this
377	* works for all current v8/srmmu implementations, we'll
378	* see...
379	*/
380	.globl spwin_srmmu_stackchk
381	spwin_srmmu_stackchk:
382	/* LOCATION: Window to be saved on the stack */
383
384	/* Because of SMP concerns and speed we play a trick.
385	* We disable fault traps in the MMU control register,
386	* Execute the stores, then check the fault registers
387	* to see what happens. I can hear Linus now
388	* "disgusting... broken hardware...".
389	*
390	* But first, check to see if the users stack has ended
391	* up in kernel vma, then we would succeed for the 'wrong'
392	* reason... ;( Note that the 'sethi' below assumes the
393	* kernel is page aligned, which should always be the case.
394	*/
395	/* Check results of callers andcc %sp, 0x7, %g0 */
396	bne spwin_user_stack_is_bolixed
397	sethi %hi(PAGE_OFFSET), %glob_tmp
398	cmp %glob_tmp, %sp
399	bleu spwin_user_stack_is_bolixed
400	mov AC_M_SFSR, %glob_tmp
401
402	/* Clear the fault status and turn on the no_fault bit. */
403	lda [%glob_tmp] ASI_M_MMUREGS, %g0 ! eat SFSR
404
405	lda [%g0] ASI_M_MMUREGS, %glob_tmp ! read MMU control
406	or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit
407	sta %glob_tmp, [%g0] ASI_M_MMUREGS ! set it
408
409	/* Dump the registers and cross fingers. */
410	STORE_WINDOW(sp)
411
412	/* Clear the no_fault bit and check the status. */
413	andn %glob_tmp, 0x2, %glob_tmp
414	sta %glob_tmp, [%g0] ASI_M_MMUREGS
415
416	mov AC_M_SFAR, %glob_tmp
417	lda [%glob_tmp] ASI_M_MMUREGS, %g0
418
419	mov AC_M_SFSR, %glob_tmp
420	lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp
421	andcc %glob_tmp, 0x2, %g0 ! did we fault?
422	be,a spwin_finish_up + 0x4 ! cool beans, success
423	restore %g0, %g0, %g0
424
425	rd %psr, %glob_tmp
426	b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh
427	nop