1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | /* |
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 | */ |
167 | b spwin_srmmu_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 | |
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. */ |
336 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) ! eat SFSR |
337 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) ! eat SFSR |
338 | |
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 |
341 | or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit |
342 | LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) ! set it |
343 | SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) ! set it |
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 |
350 | LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) |
351 | SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) |
352 | |
353 | mov AC_M_SFAR, %glob_tmp |
354 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0) |
355 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0) |
356 | |
357 | mov AC_M_SFSR, %glob_tmp |
358 | LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp) |
359 | SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp) |
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 |
367 | |