| blob | 3bbcd8dc9abf6622a26525fe5de2278ccd83edec |
1 /*
2 * wof.S: Sparc window overflow handler.
3 *
4 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
5 */
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>
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 */
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 */
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 */
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 */
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 */
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 */
75 mov %g5, %saved_g5 ! save away global temp register
76 mov %g6, %saved_g6 ! save away 'current' ptr register
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
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)
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
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
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
112 spwin_no_userwins_from_kernel:
113 /* LOCATION: Window to be saved */
115 STORE_WINDOW(sp) ! stash the window
116 restore %g0, %g0, %g0 ! go back into trap window
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
126 spwin_exist_uwins:
127 /* LOCATION: Trap window */
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
145 spwin_fromuser:
146 /* LOCATION: Window to be saved */
147 wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim
149 /* LOCATION: Window to be saved */
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
170 spwin_good_ustack:
171 /* LOCATION: Window to be saved */
173 /* The users stack is ok and we can safely save it at
174 * %sp.
175 */
176 STORE_WINDOW(sp)
178 spwin_finish_up:
179 restore %g0, %g0, %g0 /* Back to trap window. */
181 /* LOCATION: Trap window */
183 /* We have spilled successfully, and we have properly stored
184 * the appropriate window onto the stack.
185 */
187 /* Restore saved globals */
188 mov %saved_g5, %g5
189 mov %saved_g6, %g6
191 wr %t_psr, 0x0, %psr
192 WRITE_PAUSE
193 jmp %t_pc
194 rett %t_npc
196 spwin_user_stack_is_bolixed:
197 /* LOCATION: Window to be saved */
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
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
219 /* LOCATION: Trap Window */
221 /* Back in the trap window, update winbuffer save count. */
222 mov 1, %twin_tmp
223 st %twin_tmp, [%curptr + TI_W_SAVED]
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]
237 #define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
239 sethi %hi(STACK_OFFSET), %sp
240 or %sp, %lo(STACK_OFFSET), %sp
241 add %curptr, %sp, %sp
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)
248 sethi %hi(STACK_OFFSET), %g6
249 or %g6, %lo(STACK_OFFSET), %g6
250 sub %sp, %g6, %g6 ! curptr
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
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
265 spwin_bad_ustack_from_kernel:
266 /* LOCATION: Window to be saved */
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
277 /* LOCATION: Trap window */
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
286 wr %t_psr, 0x0, %psr
287 WRITE_PAUSE
289 jmp %t_pc
290 rett %t_npc
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
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 */
309 spwin_sun4c_stackchk:
310 /* LOCATION: Window to be saved on the stack */
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
318 rd %psr, %glob_tmp
319 b spwin_user_stack_is_bolixed + 0x4
320 nop
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
328 rd %psr, %glob_tmp
329 b spwin_user_stack_is_bolixed + 0x4
330 nop
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
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? */
348 rd %psr, %glob_tmp
349 b spwin_user_stack_is_bolixed + 0x4
350 nop
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
359 rd %psr, %glob_tmp
360 b spwin_user_stack_is_bolixed + 0x4
361 nop
363 1:
364 lda [%glob_tmp] ASI_PTE, %glob_tmp
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
372 rd %psr, %glob_tmp
373 b spwin_user_stack_is_bolixed + 0x4
374 nop
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 */
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
402 /* Clear the fault status and turn on the no_fault bit. */
403 lda [%glob_tmp] ASI_M_MMUREGS, %g0 ! eat SFSR
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
409 /* Dump the registers and cross fingers. */
410 STORE_WINDOW(sp)
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
416 mov AC_M_SFAR, %glob_tmp
417 lda [%glob_tmp] ASI_M_MMUREGS, %g0
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
425 rd %psr, %glob_tmp
426 b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh
427 nop