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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
88278ca2 | 2 | /* |
1da177e4 LT |
3 | * wof.S: Sparc window overflow handler. |
4 | * | |
5 | * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu) | |
6 | */ | |
7 | ||
8 | #include <asm/contregs.h> | |
9 | #include <asm/page.h> | |
10 | #include <asm/ptrace.h> | |
11 | #include <asm/psr.h> | |
12 | #include <asm/smp.h> | |
13 | #include <asm/asi.h> | |
14 | #include <asm/winmacro.h> | |
15 | #include <asm/asmmacro.h> | |
16 | #include <asm/thread_info.h> | |
17 | ||
18 | /* WARNING: This routine is hairy and _very_ complicated, but it | |
19 | * must be as fast as possible as it handles the allocation | |
20 | * of register windows to the user and kernel. If you touch | |
21 | * this code be _very_ careful as many other pieces of the | |
22 | * kernel depend upon how this code behaves. You have been | |
23 | * duly warned... | |
24 | */ | |
25 | ||
26 | /* We define macro's for registers which have a fixed | |
27 | * meaning throughout this entire routine. The 'T' in | |
28 | * the comments mean that the register can only be | |
29 | * accessed when in the 'trap' window, 'G' means | |
30 | * accessible in any window. Do not change these registers | |
31 | * after they have been set, until you are ready to return | |
32 | * from the trap. | |
33 | */ | |
34 | #define t_psr l0 /* %psr at trap time T */ | |
35 | #define t_pc l1 /* PC for trap return T */ | |
36 | #define t_npc l2 /* NPC for trap return T */ | |
37 | #define t_wim l3 /* %wim at trap time T */ | |
38 | #define saved_g5 l5 /* Global save register T */ | |
39 | #define saved_g6 l6 /* Global save register T */ | |
40 | #define curptr g6 /* Gets set to 'current' then stays G */ | |
41 | ||
42 | /* Now registers whose values can change within the handler. */ | |
43 | #define twin_tmp l4 /* Temp reg, only usable in trap window T */ | |
44 | #define glob_tmp g5 /* Global temporary reg, usable anywhere G */ | |
45 | ||
46 | .text | |
47 | .align 4 | |
48 | /* BEGINNING OF PATCH INSTRUCTIONS */ | |
49 | /* On a 7-window Sparc the boot code patches spnwin_* | |
50 | * instructions with the following ones. | |
51 | */ | |
52 | .globl spnwin_patch1_7win, spnwin_patch2_7win, spnwin_patch3_7win | |
53 | spnwin_patch1_7win: sll %t_wim, 6, %glob_tmp | |
54 | spnwin_patch2_7win: and %glob_tmp, 0x7f, %glob_tmp | |
55 | spnwin_patch3_7win: and %twin_tmp, 0x7f, %twin_tmp | |
56 | /* END OF PATCH INSTRUCTIONS */ | |
57 | ||
58 | /* The trap entry point has done the following: | |
59 | * | |
60 | * rd %psr, %l0 | |
61 | * rd %wim, %l3 | |
62 | * b spill_window_entry | |
63 | * andcc %l0, PSR_PS, %g0 | |
64 | */ | |
65 | ||
66 | /* Datum current_thread_info->uwinmask contains at all times a bitmask | |
67 | * where if any user windows are active, at least one bit will | |
68 | * be set in to mask. If no user windows are active, the bitmask | |
69 | * will be all zeroes. | |
70 | */ | |
71 | .globl spill_window_entry | |
72 | .globl spnwin_patch1, spnwin_patch2, spnwin_patch3 | |
73 | spill_window_entry: | |
74 | /* LOCATION: Trap Window */ | |
75 | ||
76 | mov %g5, %saved_g5 ! save away global temp register | |
77 | mov %g6, %saved_g6 ! save away 'current' ptr register | |
78 | ||
79 | /* Compute what the new %wim will be if we save the | |
80 | * window properly in this trap handler. | |
81 | * | |
82 | * newwim = ((%wim>>1) | (%wim<<(nwindows - 1))); | |
83 | */ | |
84 | srl %t_wim, 0x1, %twin_tmp | |
85 | spnwin_patch1: sll %t_wim, 7, %glob_tmp | |
86 | or %glob_tmp, %twin_tmp, %glob_tmp | |
87 | spnwin_patch2: and %glob_tmp, 0xff, %glob_tmp | |
88 | ||
89 | /* The trap entry point has set the condition codes | |
90 | * up for us to see if this is from user or kernel. | |
91 | * Get the load of 'curptr' out of the way. | |
92 | */ | |
93 | LOAD_CURRENT(curptr, twin_tmp) | |
94 | ||
95 | andcc %t_psr, PSR_PS, %g0 | |
96 | be,a spwin_fromuser ! all user wins, branch | |
97 | save %g0, %g0, %g0 ! Go where saving will occur | |
98 | ||
99 | /* See if any user windows are active in the set. */ | |
100 | ld [%curptr + TI_UWINMASK], %twin_tmp ! grab win mask | |
101 | orcc %g0, %twin_tmp, %g0 ! check for set bits | |
102 | bne spwin_exist_uwins ! yep, there are some | |
103 | andn %twin_tmp, %glob_tmp, %twin_tmp ! compute new uwinmask | |
104 | ||
105 | /* Save into the window which must be saved and do it. | |
106 | * Basically if we are here, this means that we trapped | |
107 | * from kernel mode with only kernel windows in the register | |
108 | * file. | |
109 | */ | |
110 | save %g0, %g0, %g0 ! save into the window to stash away | |
111 | wr %glob_tmp, 0x0, %wim ! set new %wim, this is safe now | |
112 | ||
113 | spwin_no_userwins_from_kernel: | |
114 | /* LOCATION: Window to be saved */ | |
115 | ||
116 | STORE_WINDOW(sp) ! stash the window | |
117 | restore %g0, %g0, %g0 ! go back into trap window | |
118 | ||
119 | /* LOCATION: Trap window */ | |
120 | mov %saved_g5, %g5 ! restore %glob_tmp | |
121 | mov %saved_g6, %g6 ! restore %curptr | |
122 | wr %t_psr, 0x0, %psr ! restore condition codes in %psr | |
123 | WRITE_PAUSE ! waste some time | |
124 | jmp %t_pc ! Return from trap | |
125 | rett %t_npc ! we are done | |
126 | ||
127 | spwin_exist_uwins: | |
128 | /* LOCATION: Trap window */ | |
129 | ||
130 | /* Wow, user windows have to be dealt with, this is dirty | |
131 | * and messy as all hell. And difficult to follow if you | |
132 | * are approaching the infamous register window trap handling | |
133 | * problem for the first time. DON'T LOOK! | |
134 | * | |
135 | * Note that how the execution path works out, the new %wim | |
136 | * will be left for us in the global temporary register, | |
137 | * %glob_tmp. We cannot set the new %wim first because we | |
138 | * need to save into the appropriate window without inducing | |
139 | * a trap (traps are off, we'd get a watchdog wheee)... | |
140 | * But first, store the new user window mask calculated | |
141 | * above. | |
142 | */ | |
143 | st %twin_tmp, [%curptr + TI_UWINMASK] | |
144 | save %g0, %g0, %g0 ! Go to where the saving will occur | |
145 | ||
146 | spwin_fromuser: | |
147 | /* LOCATION: Window to be saved */ | |
148 | wr %glob_tmp, 0x0, %wim ! Now it is safe to set new %wim | |
149 | ||
150 | /* LOCATION: Window to be saved */ | |
151 | ||
152 | /* This instruction branches to a routine which will check | |
153 | * to validity of the users stack pointer by whatever means | |
154 | * are necessary. This means that this is architecture | |
155 | * specific and thus this branch instruction will need to | |
156 | * be patched at boot time once the machine type is known. | |
157 | * This routine _shall not_ touch %curptr under any | |
158 | * circumstances whatsoever! It will branch back to the | |
159 | * label 'spwin_good_ustack' if the stack is ok but still | |
160 | * needs to be dumped (SRMMU for instance will not need to | |
161 | * do this) or 'spwin_finish_up' if the stack is ok and the | |
162 | * registers have already been saved. If the stack is found | |
163 | * to be bogus for some reason the routine shall branch to | |
164 | * the label 'spwin_user_stack_is_bolixed' which will take | |
165 | * care of things at that point. | |
166 | */ | |
054768a1 SR |
167 | b spwin_srmmu_stackchk |
168 | andcc %sp, 0x7, %g0 | |
1da177e4 LT |
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 | /* This is a generic SRMMU routine. As far as I know this |
310 | * works for all current v8/srmmu implementations, we'll | |
311 | * see... | |
312 | */ | |
313 | .globl spwin_srmmu_stackchk | |
314 | spwin_srmmu_stackchk: | |
315 | /* LOCATION: Window to be saved on the stack */ | |
316 | ||
317 | /* Because of SMP concerns and speed we play a trick. | |
318 | * We disable fault traps in the MMU control register, | |
319 | * Execute the stores, then check the fault registers | |
320 | * to see what happens. I can hear Linus now | |
321 | * "disgusting... broken hardware...". | |
322 | * | |
323 | * But first, check to see if the users stack has ended | |
324 | * up in kernel vma, then we would succeed for the 'wrong' | |
325 | * reason... ;( Note that the 'sethi' below assumes the | |
326 | * kernel is page aligned, which should always be the case. | |
327 | */ | |
328 | /* Check results of callers andcc %sp, 0x7, %g0 */ | |
329 | bne spwin_user_stack_is_bolixed | |
330 | sethi %hi(PAGE_OFFSET), %glob_tmp | |
331 | cmp %glob_tmp, %sp | |
332 | bleu spwin_user_stack_is_bolixed | |
333 | mov AC_M_SFSR, %glob_tmp | |
334 | ||
335 | /* Clear the fault status and turn on the no_fault bit. */ | |
1ec8cf62 SR |
336 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) ! eat SFSR |
337 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) ! eat SFSR | |
1da177e4 | 338 | |
1ec8cf62 SR |
339 | LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %glob_tmp) ! read MMU control |
340 | SUN_PI_(lda [%g0] ASI_M_MMUREGS, %glob_tmp) ! read MMU control | |
1da177e4 | 341 | or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit |
1ec8cf62 SR |
342 | LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) ! set it |
343 | SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) ! set it | |
1da177e4 LT |
344 | |
345 | /* Dump the registers and cross fingers. */ | |
346 | STORE_WINDOW(sp) | |
347 | ||
348 | /* Clear the no_fault bit and check the status. */ | |
349 | andn %glob_tmp, 0x2, %glob_tmp | |
1ec8cf62 SR |
350 | LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) |
351 | SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) | |
1da177e4 LT |
352 | |
353 | mov AC_M_SFAR, %glob_tmp | |
1ec8cf62 SR |
354 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) |
355 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) | |
1da177e4 LT |
356 | |
357 | mov AC_M_SFSR, %glob_tmp | |
1ec8cf62 SR |
358 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp) |
359 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp) | |
1da177e4 LT |
360 | andcc %glob_tmp, 0x2, %g0 ! did we fault? |
361 | be,a spwin_finish_up + 0x4 ! cool beans, success | |
362 | restore %g0, %g0, %g0 | |
363 | ||
364 | rd %psr, %glob_tmp | |
365 | b spwin_user_stack_is_bolixed + 0x4 ! we faulted, ugh | |
366 | nop |