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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/sparc/kernel/wuf.S
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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1/* $Id: wuf.S,v 1.39 2000/01/08 16:38:18 anton Exp $
2 * wuf.S: Window underflow trap handler for the Sparc.
3 *
4 * Copyright (C) 1995 David S. Miller
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/* Just like the overflow handler we define macros for registers
18 * with fixed meanings in this routine.
19 */
20#define t_psr l0
21#define t_pc l1
22#define t_npc l2
23#define t_wim l3
24/* Don't touch the above registers or else you die horribly... */
25
26/* Now macros for the available scratch registers in this routine. */
27#define twin_tmp1 l4
28#define twin_tmp2 l5
29
30#define curptr g6
31
32 .text
33 .align 4
34
35 /* The trap entry point has executed the following:
36 *
37 * rd %psr, %l0
38 * rd %wim, %l3
39 * b fill_window_entry
40 * andcc %l0, PSR_PS, %g0
41 */
42
43 /* Datum current_thread_info->uwinmask contains at all times a bitmask
44 * where if any user windows are active, at least one bit will
45 * be set in to mask. If no user windows are active, the bitmask
46 * will be all zeroes.
47 */
48
49 /* To get an idea of what has just happened to cause this
50 * trap take a look at this diagram:
51 *
52 * 1 2 3 4 <-- Window number
53 * ----------
54 * T O W I <-- Symbolic name
55 *
56 * O == the window that execution was in when
57 * the restore was attempted
58 *
59 * T == the trap itself has save'd us into this
60 * window
61 *
62 * W == this window is the one which is now invalid
63 * and must be made valid plus loaded from the
64 * stack
65 *
66 * I == this window will be the invalid one when we
67 * are done and return from trap if successful
68 */
69
70 /* BEGINNING OF PATCH INSTRUCTIONS */
71
72 /* On 7-window Sparc the boot code patches fnwin_patch1
73 * with the following instruction.
74 */
75 .globl fnwin_patch1_7win, fnwin_patch2_7win
76fnwin_patch1_7win: srl %t_wim, 6, %twin_tmp2
77fnwin_patch2_7win: and %twin_tmp1, 0x7f, %twin_tmp1
78 /* END OF PATCH INSTRUCTIONS */
79
80 .globl fill_window_entry, fnwin_patch1, fnwin_patch2
81fill_window_entry:
82 /* LOCATION: Window 'T' */
83
84 /* Compute what the new %wim is going to be if we retrieve
85 * the proper window off of the stack.
86 */
87 sll %t_wim, 1, %twin_tmp1
88fnwin_patch1: srl %t_wim, 7, %twin_tmp2
89 or %twin_tmp1, %twin_tmp2, %twin_tmp1
90fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1
91
92 wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */
93
94 andcc %t_psr, PSR_PS, %g0
95 be fwin_from_user
96 restore %g0, %g0, %g0 /* Restore to window 'O' */
97
98 /* Trapped from kernel, we trust that the kernel does not
99 * 'over restore' sorta speak and just grab the window
100 * from the stack and return. Easy enough.
101 */
102fwin_from_kernel:
103 /* LOCATION: Window 'O' */
104
105 restore %g0, %g0, %g0
106
107 /* LOCATION: Window 'W' */
108
109 LOAD_WINDOW(sp) /* Load it up */
110
111 /* Spin the wheel... */
112 save %g0, %g0, %g0
113 save %g0, %g0, %g0
114 /* I'd like to buy a vowel please... */
115
116 /* LOCATION: Window 'T' */
117
118 /* Now preserve the condition codes in %psr, pause, and
119 * return from trap. This is the simplest case of all.
120 */
121 wr %t_psr, 0x0, %psr
122 WRITE_PAUSE
123
124 jmp %t_pc
125 rett %t_npc
126
127fwin_from_user:
128 /* LOCATION: Window 'O' */
129
130 restore %g0, %g0, %g0 /* Restore to window 'W' */
131
132 /* LOCATION: Window 'W' */
133
134 /* Branch to the architecture specific stack validation
135 * routine. They can be found below...
136 */
137 .globl fwin_mmu_patchme
138fwin_mmu_patchme: b sun4c_fwin_stackchk
139 andcc %sp, 0x7, %g0
140
141#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
142
143fwin_user_stack_is_bolixed:
144 /* LOCATION: Window 'W' */
145
146 /* Place a pt_regs frame on the kernel stack, save back
147 * to the trap window and call c-code to deal with this.
148 */
149 LOAD_CURRENT(l4, l5)
150
151 sethi %hi(STACK_OFFSET), %l5
152 or %l5, %lo(STACK_OFFSET), %l5
153 add %l4, %l5, %l5
154
155 /* Store globals into pt_regs frame. */
156 STORE_PT_GLOBALS(l5)
157 STORE_PT_YREG(l5, g3)
158
159 /* Save current in a global while we change windows. */
160 mov %l4, %curptr
161
162 save %g0, %g0, %g0
163
164 /* LOCATION: Window 'O' */
165
166 rd %psr, %g3 /* Read %psr in live user window */
167 mov %fp, %g4 /* Save bogus frame pointer. */
168
169 save %g0, %g0, %g0
170
171 /* LOCATION: Window 'T' */
172
173 sethi %hi(STACK_OFFSET), %l5
174 or %l5, %lo(STACK_OFFSET), %l5
175 add %curptr, %l5, %sp
176
177 /* Build rest of pt_regs. */
178 STORE_PT_INS(sp)
179 STORE_PT_PRIV(sp, t_psr, t_pc, t_npc)
180
181 /* re-set trap time %wim value */
182 wr %t_wim, 0x0, %wim
183
184 /* Fix users window mask and buffer save count. */
185 mov 0x1, %g5
186 sll %g5, %g3, %g5
187 st %g5, [%curptr + TI_UWINMASK] ! one live user window still
188 st %g0, [%curptr + TI_W_SAVED] ! no windows in the buffer
189
190 wr %t_psr, PSR_ET, %psr ! enable traps
191 nop
192 call window_underflow_fault
193 mov %g4, %o0
194
195 b ret_trap_entry
196 clr %l6
197
198fwin_user_stack_is_ok:
199 /* LOCATION: Window 'W' */
200
201 /* The users stack area is kosher and mapped, load the
202 * window and fall through to the finish up routine.
203 */
204 LOAD_WINDOW(sp)
205
206 /* Round and round she goes... */
207 save %g0, %g0, %g0 /* Save to window 'O' */
208 save %g0, %g0, %g0 /* Save to window 'T' */
209 /* Where she'll trap nobody knows... */
210
211 /* LOCATION: Window 'T' */
212
213fwin_user_finish_up:
214 /* LOCATION: Window 'T' */
215
216 wr %t_psr, 0x0, %psr
217 WRITE_PAUSE
218
219 jmp %t_pc
220 rett %t_npc
221
222 /* Here come the architecture specific checks for stack.
223 * mappings. Note that unlike the window overflow handler
224 * we only need to check whether the user can read from
225 * the appropriate addresses. Also note that we are in
226 * an invalid window which will be loaded, and this means
227 * that until we actually load the window up we are free
228 * to use any of the local registers contained within.
229 *
230 * On success these routine branch to fwin_user_stack_is_ok
231 * if the area at %sp is user readable and the window still
232 * needs to be loaded, else fwin_user_finish_up if the
233 * routine has done the loading itself. On failure (bogus
234 * user stack) the routine shall branch to the label called
235 * fwin_user_stack_is_bolixed.
236 *
237 * Contrary to the arch-specific window overflow stack
238 * check routines in wof.S, these routines are free to use
239 * any of the local registers they want to as this window
240 * does not belong to anyone at this point, however the
241 * outs and ins are still verboten as they are part of
242 * 'someone elses' window possibly.
243 */
244
245 .align 4
246 .globl sun4c_fwin_stackchk
247sun4c_fwin_stackchk:
248 /* LOCATION: Window 'W' */
249
250 /* Caller did 'andcc %sp, 0x7, %g0' */
251 be 1f
252 and %sp, 0xfff, %l0 ! delay slot
253
254 b,a fwin_user_stack_is_bolixed
255
256 /* See if we have to check the sanity of one page or two */
2571:
258 add %l0, 0x38, %l0
259 sra %sp, 29, %l5
260 add %l5, 0x1, %l5
261 andncc %l5, 0x1, %g0
262 be 1f
263 andncc %l0, 0xff8, %g0
264
265 b,a fwin_user_stack_is_bolixed /* %sp is in vma hole, yuck */
266
2671:
268 be sun4c_fwin_onepage /* Only one page to check */
269 lda [%sp] ASI_PTE, %l1
270sun4c_fwin_twopages:
271 add %sp, 0x38, %l0
272 sra %l0, 29, %l5
273 add %l5, 0x1, %l5
274 andncc %l5, 0x1, %g0
275 be 1f
276 lda [%l0] ASI_PTE, %l1
277
278 b,a fwin_user_stack_is_bolixed /* Second page in vma hole */
279
2801:
281 srl %l1, 29, %l1
282 andcc %l1, 0x4, %g0
283 bne sun4c_fwin_onepage
284 lda [%sp] ASI_PTE, %l1
285
286 b,a fwin_user_stack_is_bolixed /* Second page has bad perms */
287
288sun4c_fwin_onepage:
289 srl %l1, 29, %l1
290 andcc %l1, 0x4, %g0
291 bne fwin_user_stack_is_ok
292 nop
293
294 /* A page had bad page permissions, losing... */
295 b,a fwin_user_stack_is_bolixed
296
297 .globl srmmu_fwin_stackchk
298srmmu_fwin_stackchk:
299 /* LOCATION: Window 'W' */
300
301 /* Caller did 'andcc %sp, 0x7, %g0' */
302 bne fwin_user_stack_is_bolixed
303 sethi %hi(PAGE_OFFSET), %l5
304
305 /* Check if the users stack is in kernel vma, then our
306 * trial and error technique below would succeed for
307 * the 'wrong' reason.
308 */
309 mov AC_M_SFSR, %l4
310 cmp %l5, %sp
311 bleu fwin_user_stack_is_bolixed
312 lda [%l4] ASI_M_MMUREGS, %g0 ! clear fault status
313
314 /* The technique is, turn off faults on this processor,
315 * just let the load rip, then check the sfsr to see if
316 * a fault did occur. Then we turn on fault traps again
317 * and branch conditionally based upon what happened.
318 */
319 lda [%g0] ASI_M_MMUREGS, %l5 ! read mmu-ctrl reg
320 or %l5, 0x2, %l5 ! turn on no-fault bit
321 sta %l5, [%g0] ASI_M_MMUREGS ! store it
322
323 /* Cross fingers and go for it. */
324 LOAD_WINDOW(sp)
325
326 /* A penny 'saved'... */
327 save %g0, %g0, %g0
328 save %g0, %g0, %g0
329 /* Is a BADTRAP earned... */
330
331 /* LOCATION: Window 'T' */
332
333 lda [%g0] ASI_M_MMUREGS, %twin_tmp1 ! load mmu-ctrl again
334 andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit
335 sta %twin_tmp1, [%g0] ASI_M_MMUREGS ! store it
336
337 mov AC_M_SFAR, %twin_tmp2
338 lda [%twin_tmp2] ASI_M_MMUREGS, %g0 ! read fault address
339
340 mov AC_M_SFSR, %twin_tmp2
341 lda [%twin_tmp2] ASI_M_MMUREGS, %twin_tmp2 ! read fault status
342 andcc %twin_tmp2, 0x2, %g0 ! did fault occur?
343
344 bne 1f ! yep, cleanup
345 nop
346
347 wr %t_psr, 0x0, %psr
348 nop
349 b fwin_user_finish_up + 0x4
350 nop
351
352 /* Did I ever tell you about my window lobotomy?
353 * anyways... fwin_user_stack_is_bolixed expects
354 * to be in window 'W' so make it happy or else
355 * we watchdog badly.
356 */
3571:
358 restore %g0, %g0, %g0
359 b fwin_user_stack_is_bolixed ! oh well
360 restore %g0, %g0, %g0