1/* $Id: etrap.S,v 1.31 2000/01/08 16:38:18 anton Exp $
2 * etrap.S: Sparc trap window preparation for entry into the
3 *          Linux kernel.
4 *
5 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
6 */
7
8#include <asm/cprefix.h>
9#include <asm/head.h>
10#include <asm/asi.h>
11#include <asm/contregs.h>
12#include <asm/page.h>
13#include <asm/psr.h>
14#include <asm/ptrace.h>
15#include <asm/winmacro.h>
16#include <asm/asmmacro.h>
17
18/* Registers to not touch at all. */
19#define t_psr        l0 /* Set by caller */
20#define t_pc         l1 /* Set by caller */
21#define t_npc        l2 /* Set by caller */
22#define t_wim        l3 /* Set by caller */
23#define t_twinmask   l4 /* Set at beginning of this entry routine. */
24#define t_kstack     l5 /* Set right before pt_regs frame is built */
25#define t_retpc      l6 /* If you change this, change winmacro.h header file */
26#define t_systable   l7 /* Never touch this, could be the syscall table ptr. */
27#define curptr       g6 /* Set after pt_regs frame is built */
28
29	.text
30	.align 4
31
32	/* SEVEN WINDOW PATCH INSTRUCTIONS */
33	.globl	tsetup_7win_patch1, tsetup_7win_patch2
34	.globl	tsetup_7win_patch3, tsetup_7win_patch4
35	.globl	tsetup_7win_patch5, tsetup_7win_patch6
36tsetup_7win_patch1:	sll	%t_wim, 0x6, %t_wim
37tsetup_7win_patch2:	and	%g2, 0x7f, %g2
38tsetup_7win_patch3:	and	%g2, 0x7f, %g2
39tsetup_7win_patch4:	and	%g1, 0x7f, %g1
40tsetup_7win_patch5:	sll	%t_wim, 0x6, %t_wim
41tsetup_7win_patch6:	and	%g2, 0x7f, %g2
42	/* END OF PATCH INSTRUCTIONS */
43
44	/* At trap time, interrupts and all generic traps do the
45	 * following:
46	 *
47	 * rd	%psr, %l0
48	 * b	some_handler
49	 * rd	%wim, %l3
50	 * nop
51	 *
52	 * Then 'some_handler' if it needs a trap frame (ie. it has
53	 * to call c-code and the trap cannot be handled in-window)
54	 * then it does the SAVE_ALL macro in entry.S which does
55	 *
56	 * sethi	%hi(trap_setup), %l4
57	 * jmpl		%l4 + %lo(trap_setup), %l6
58	 * mov		1, %l4
59	 */
60
61	/* 2 3 4  window number
62	 * -----
63	 * O T S  mnemonic
64	 *
65	 * O == Current window before trap
66	 * T == Window entered when trap occurred
67	 * S == Window we will need to save if (1<<T) == %wim
68	 *
69	 * Before execution gets here, it must be guaranteed that
70	 * %l0 contains trap time %psr, %l1 and %l2 contain the
71	 * trap pc and npc, and %l3 contains the trap time %wim.
72	 */
73
74	.globl	trap_setup, tsetup_patch1, tsetup_patch2
75	.globl	tsetup_patch3, tsetup_patch4
76	.globl	tsetup_patch5, tsetup_patch6
77trap_setup:
78	/* Calculate mask of trap window.  See if from user
79	 * or kernel and branch conditionally.
80	 */
81	mov	1, %t_twinmask
82	andcc	%t_psr, PSR_PS, %g0		 ! fromsupv_p = (psr & PSR_PS)
83	be	trap_setup_from_user		 ! nope, from user mode
84	 sll	%t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
85
86	/* From kernel, allocate more kernel stack and
87	 * build a pt_regs trap frame.
88	 */
89	sub	%fp, (STACKFRAME_SZ + TRACEREG_SZ), %t_kstack
90	STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
91
92	/* See if we are in the trap window. */
93	andcc	%t_twinmask, %t_wim, %g0
94	bne	trap_setup_kernel_spill		! in trap window, clean up
95	 nop
96
97	/* Trap from kernel with a window available.
98	 * Just do it...
99	 */
100	jmpl	%t_retpc + 0x8, %g0	! return to caller
101	 mov	%t_kstack, %sp		! jump onto new stack
102
103trap_setup_kernel_spill:
104	ld	[%curptr + AOFF_task_thread + AOFF_thread_uwinmask], %g1
105	orcc	%g0, %g1, %g0
106	bne	trap_setup_user_spill	! there are some user windows, yuck
107	/* Spill from kernel, but only kernel windows, adjust
108	 * %wim and go.
109	 */
110	 srl	%t_wim, 0x1, %g2	! begin computation of new %wim
111tsetup_patch1:
112	sll	%t_wim, 0x7, %t_wim	! patched on 7 window Sparcs
113	or	%t_wim, %g2, %g2
114tsetup_patch2:
115	and	%g2, 0xff, %g2		! patched on 7 window Sparcs
116
117	save	%g0, %g0, %g0
118
119	/* Set new %wim value */
120	wr	%g2, 0x0, %wim
121
122	/* Save the kernel window onto the corresponding stack. */
123	STORE_WINDOW(sp)
124
125	restore	%g0, %g0, %g0
126
127	jmpl	%t_retpc + 0x8, %g0	! return to caller
128	 mov	%t_kstack, %sp		! and onto new kernel stack
129
130#define STACK_OFFSET (TASK_UNION_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
131trap_setup_from_user:
132	/* We can't use %curptr yet. */
133	LOAD_CURRENT(t_kstack, t_twinmask)
134
135	sethi	%hi(STACK_OFFSET), %t_twinmask
136	or	%t_twinmask, %lo(STACK_OFFSET), %t_twinmask
137	add	%t_kstack, %t_twinmask, %t_kstack
138
139	mov	1, %t_twinmask
140	sll	%t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
141
142	/* Build pt_regs frame. */
143	STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
144
145#if 0
146	/* If we're sure every task_struct is TASK_UNION_SIZE aligned,
147	   we can speed this up. */
148	sethi	%hi(STACK_OFFSET), %curptr
149	or	%curptr, %lo(STACK_OFFSET), %curptr
150	sub	%t_kstack, %curptr, %curptr
151#else
152	sethi	%hi(~(TASK_UNION_SIZE - 1)), %curptr
153	and	%t_kstack, %curptr, %curptr
154#endif
155
156	/* Clear current->thread.w_saved */
157	st	%g0, [%curptr + AOFF_task_thread + AOFF_thread_w_saved]
158
159	/* See if we are in the trap window. */
160	andcc	%t_twinmask, %t_wim, %g0
161	bne	trap_setup_user_spill		! yep we are
162	 orn	%g0, %t_twinmask, %g1		! negate trap win mask into %g1
163
164	/* Trap from user, but not into the invalid window.
165	 * Calculate new umask.  The way this works is,
166	 * any window from the %wim at trap time until
167	 * the window right before the one we are in now,
168	 * is a user window.  A diagram:
169	 *
170	 *      7 6 5 4 3 2 1 0    window number
171	 *      ---------------
172	 *        I     L T        mnemonic
173	 *
174	 * Window 'I' is the invalid window in our example,
175	 * window 'L' is the window the user was in when
176	 * the trap occurred, window T is the trap window
177	 * we are in now.  So therefore, windows 5, 4 and
178	 * 3 are user windows.  The following sequence
179	 * computes the user winmask to represent this.
180	 */
181	subcc	%t_wim, %t_twinmask, %g2
182	bneg,a	1f
183	 sub	%g2, 0x1, %g2
1841:
185	andn	%g2, %t_twinmask, %g2
186tsetup_patch3:
187	and	%g2, 0xff, %g2			! patched on 7win Sparcs
188	st	%g2, [%curptr + AOFF_task_thread + AOFF_thread_uwinmask]	! store new umask
189
190	jmpl	%t_retpc + 0x8, %g0		! return to caller
191	 mov	%t_kstack, %sp			! and onto kernel stack
192
193trap_setup_user_spill:
194	/* A spill occurred from either kernel or user mode
195	 * and there exist some user windows to deal with.
196	 * A mask of the currently valid user windows
197	 * is in %g1 upon entry to here.
198	 */
199
200tsetup_patch4:
201	and	%g1, 0xff, %g1		! patched on 7win Sparcs, mask
202	srl	%t_wim, 0x1, %g2	! compute new %wim
203tsetup_patch5:
204	sll	%t_wim, 0x7, %t_wim	! patched on 7win Sparcs
205	or	%t_wim, %g2, %g2	! %g2 is new %wim
206tsetup_patch6:
207	and	%g2, 0xff, %g2		! patched on 7win Sparcs
208	andn	%g1, %g2, %g1		! clear this bit in %g1
209	st	%g1, [%curptr + AOFF_task_thread + AOFF_thread_uwinmask]
210
211	save	%g0, %g0, %g0
212
213	wr	%g2, 0x0, %wim
214
215	/* Call MMU-architecture dependent stack checking
216	 * routine.
217	 */
218	.globl	C_LABEL(tsetup_mmu_patchme)
219C_LABEL(tsetup_mmu_patchme):
220	b	C_LABEL(tsetup_sun4c_stackchk)
221	 andcc	%sp, 0x7, %g0
222
223	/* Architecture specific stack checking routines.  When either
224	 * of these routines are called, the globals are free to use
225	 * as they have been safely stashed on the new kernel stack
226	 * pointer.  Thus the definition below for simplicity.
227	 */
228#define glob_tmp     g1
229
230	.globl	C_LABEL(tsetup_sun4c_stackchk)
231C_LABEL(tsetup_sun4c_stackchk):
232	/* Done by caller: andcc %sp, 0x7, %g0 */
233	bne	trap_setup_user_stack_is_bolixed
234	 sra	%sp, 29, %glob_tmp
235
236	add	%glob_tmp, 0x1, %glob_tmp
237	andncc	%glob_tmp, 0x1, %g0
238	bne	trap_setup_user_stack_is_bolixed
239	 and	%sp, 0xfff, %glob_tmp		! delay slot
240
241	/* See if our dump area will be on more than one
242	 * page.
243	 */
244	add	%glob_tmp, 0x38, %glob_tmp
245	andncc	%glob_tmp, 0xff8, %g0
246	be	tsetup_sun4c_onepage		! only one page to check
247	 lda	[%sp] ASI_PTE, %glob_tmp	! have to check first page anyways
248
249tsetup_sun4c_twopages:
250	/* Is first page ok permission wise? */
251	srl	%glob_tmp, 29, %glob_tmp
252	cmp	%glob_tmp, 0x6
253	bne	trap_setup_user_stack_is_bolixed
254	 add	%sp, 0x38, %glob_tmp		/* Is second page in vma hole? */
255
256	sra	%glob_tmp, 29, %glob_tmp
257	add	%glob_tmp, 0x1, %glob_tmp
258	andncc	%glob_tmp, 0x1, %g0
259	bne	trap_setup_user_stack_is_bolixed
260	 add	%sp, 0x38, %glob_tmp
261
262	lda	[%glob_tmp] ASI_PTE, %glob_tmp
263
264tsetup_sun4c_onepage:
265	srl	%glob_tmp, 29, %glob_tmp
266	cmp	%glob_tmp, 0x6				! can user write to it?
267	bne	trap_setup_user_stack_is_bolixed	! failure
268	 nop
269
270	STORE_WINDOW(sp)
271
272	restore %g0, %g0, %g0
273
274	jmpl	%t_retpc + 0x8, %g0
275	 mov	%t_kstack, %sp
276
277	.globl	C_LABEL(tsetup_srmmu_stackchk)
278C_LABEL(tsetup_srmmu_stackchk):
279	/* Check results of callers andcc %sp, 0x7, %g0 */
280	bne	trap_setup_user_stack_is_bolixed
281	 sethi   %hi(PAGE_OFFSET), %glob_tmp
282
283	cmp	%glob_tmp, %sp
284	bleu,a	1f
285	 lda	[%g0] ASI_M_MMUREGS, %glob_tmp		! read MMU control
286
287trap_setup_user_stack_is_bolixed:
288	/* From user/kernel into invalid window w/bad user
289	 * stack. Save bad user stack, and return to caller.
290	 */
291	SAVE_BOLIXED_USER_STACK(curptr, g3)
292	restore	%g0, %g0, %g0
293
294	jmpl	%t_retpc + 0x8, %g0
295	 mov	%t_kstack, %sp
296
2971:
298	/* Clear the fault status and turn on the no_fault bit. */
299	or	%glob_tmp, 0x2, %glob_tmp		! or in no_fault bit
300	sta	%glob_tmp, [%g0] ASI_M_MMUREGS		! set it
301
302	/* Dump the registers and cross fingers. */
303	STORE_WINDOW(sp)
304
305	/* Clear the no_fault bit and check the status. */
306	andn	%glob_tmp, 0x2, %glob_tmp
307	sta	%glob_tmp, [%g0] ASI_M_MMUREGS
308	mov	AC_M_SFAR, %glob_tmp
309	lda	[%glob_tmp] ASI_M_MMUREGS, %g0
310	mov	AC_M_SFSR, %glob_tmp
311	lda	[%glob_tmp] ASI_M_MMUREGS, %glob_tmp	! save away status of winstore
312	andcc	%glob_tmp, 0x2, %g0			! did we fault?
313	bne	trap_setup_user_stack_is_bolixed	! failure
314	 nop
315
316	restore %g0, %g0, %g0
317
318	jmpl	%t_retpc + 0x8, %g0
319	 mov	%t_kstack, %sp
320
321