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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
88278ca2 | 2 | /* |
1da177e4 LT |
3 | * wuf.S: Window underflow trap handler for the Sparc. |
4 | * | |
5 | * Copyright (C) 1995 David S. Miller | |
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 | /* Just like the overflow handler we define macros for registers | |
19 | * with fixed meanings in this routine. | |
20 | */ | |
21 | #define t_psr l0 | |
22 | #define t_pc l1 | |
23 | #define t_npc l2 | |
24 | #define t_wim l3 | |
25 | /* Don't touch the above registers or else you die horribly... */ | |
26 | ||
27 | /* Now macros for the available scratch registers in this routine. */ | |
28 | #define twin_tmp1 l4 | |
29 | #define twin_tmp2 l5 | |
30 | ||
31 | #define curptr g6 | |
32 | ||
33 | .text | |
34 | .align 4 | |
35 | ||
36 | /* The trap entry point has executed the following: | |
37 | * | |
38 | * rd %psr, %l0 | |
39 | * rd %wim, %l3 | |
40 | * b fill_window_entry | |
41 | * andcc %l0, PSR_PS, %g0 | |
42 | */ | |
43 | ||
44 | /* Datum current_thread_info->uwinmask contains at all times a bitmask | |
45 | * where if any user windows are active, at least one bit will | |
46 | * be set in to mask. If no user windows are active, the bitmask | |
47 | * will be all zeroes. | |
48 | */ | |
49 | ||
50 | /* To get an idea of what has just happened to cause this | |
51 | * trap take a look at this diagram: | |
52 | * | |
53 | * 1 2 3 4 <-- Window number | |
54 | * ---------- | |
55 | * T O W I <-- Symbolic name | |
56 | * | |
57 | * O == the window that execution was in when | |
58 | * the restore was attempted | |
59 | * | |
60 | * T == the trap itself has save'd us into this | |
61 | * window | |
62 | * | |
63 | * W == this window is the one which is now invalid | |
64 | * and must be made valid plus loaded from the | |
65 | * stack | |
66 | * | |
67 | * I == this window will be the invalid one when we | |
68 | * are done and return from trap if successful | |
69 | */ | |
70 | ||
71 | /* BEGINNING OF PATCH INSTRUCTIONS */ | |
72 | ||
73 | /* On 7-window Sparc the boot code patches fnwin_patch1 | |
74 | * with the following instruction. | |
75 | */ | |
76 | .globl fnwin_patch1_7win, fnwin_patch2_7win | |
77 | fnwin_patch1_7win: srl %t_wim, 6, %twin_tmp2 | |
78 | fnwin_patch2_7win: and %twin_tmp1, 0x7f, %twin_tmp1 | |
79 | /* END OF PATCH INSTRUCTIONS */ | |
80 | ||
81 | .globl fill_window_entry, fnwin_patch1, fnwin_patch2 | |
82 | fill_window_entry: | |
83 | /* LOCATION: Window 'T' */ | |
84 | ||
85 | /* Compute what the new %wim is going to be if we retrieve | |
86 | * the proper window off of the stack. | |
87 | */ | |
88 | sll %t_wim, 1, %twin_tmp1 | |
89 | fnwin_patch1: srl %t_wim, 7, %twin_tmp2 | |
90 | or %twin_tmp1, %twin_tmp2, %twin_tmp1 | |
91 | fnwin_patch2: and %twin_tmp1, 0xff, %twin_tmp1 | |
92 | ||
93 | wr %twin_tmp1, 0x0, %wim /* Make window 'I' invalid */ | |
94 | ||
95 | andcc %t_psr, PSR_PS, %g0 | |
96 | be fwin_from_user | |
97 | restore %g0, %g0, %g0 /* Restore to window 'O' */ | |
98 | ||
99 | /* Trapped from kernel, we trust that the kernel does not | |
100 | * 'over restore' sorta speak and just grab the window | |
101 | * from the stack and return. Easy enough. | |
102 | */ | |
103 | fwin_from_kernel: | |
104 | /* LOCATION: Window 'O' */ | |
105 | ||
106 | restore %g0, %g0, %g0 | |
107 | ||
108 | /* LOCATION: Window 'W' */ | |
109 | ||
110 | LOAD_WINDOW(sp) /* Load it up */ | |
111 | ||
112 | /* Spin the wheel... */ | |
113 | save %g0, %g0, %g0 | |
114 | save %g0, %g0, %g0 | |
115 | /* I'd like to buy a vowel please... */ | |
116 | ||
117 | /* LOCATION: Window 'T' */ | |
118 | ||
119 | /* Now preserve the condition codes in %psr, pause, and | |
120 | * return from trap. This is the simplest case of all. | |
121 | */ | |
122 | wr %t_psr, 0x0, %psr | |
123 | WRITE_PAUSE | |
124 | ||
125 | jmp %t_pc | |
126 | rett %t_npc | |
127 | ||
128 | fwin_from_user: | |
129 | /* LOCATION: Window 'O' */ | |
130 | ||
131 | restore %g0, %g0, %g0 /* Restore to window 'W' */ | |
132 | ||
133 | /* LOCATION: Window 'W' */ | |
134 | ||
28de2f73 SR |
135 | /* Branch to the stack validation routine */ |
136 | b srmmu_fwin_stackchk | |
137 | andcc %sp, 0x7, %g0 | |
1da177e4 LT |
138 | |
139 | #define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ) | |
140 | ||
141 | fwin_user_stack_is_bolixed: | |
142 | /* LOCATION: Window 'W' */ | |
143 | ||
144 | /* Place a pt_regs frame on the kernel stack, save back | |
145 | * to the trap window and call c-code to deal with this. | |
146 | */ | |
147 | LOAD_CURRENT(l4, l5) | |
148 | ||
149 | sethi %hi(STACK_OFFSET), %l5 | |
150 | or %l5, %lo(STACK_OFFSET), %l5 | |
151 | add %l4, %l5, %l5 | |
152 | ||
153 | /* Store globals into pt_regs frame. */ | |
154 | STORE_PT_GLOBALS(l5) | |
155 | STORE_PT_YREG(l5, g3) | |
156 | ||
157 | /* Save current in a global while we change windows. */ | |
158 | mov %l4, %curptr | |
159 | ||
160 | save %g0, %g0, %g0 | |
161 | ||
162 | /* LOCATION: Window 'O' */ | |
163 | ||
164 | rd %psr, %g3 /* Read %psr in live user window */ | |
165 | mov %fp, %g4 /* Save bogus frame pointer. */ | |
166 | ||
167 | save %g0, %g0, %g0 | |
168 | ||
169 | /* LOCATION: Window 'T' */ | |
170 | ||
171 | sethi %hi(STACK_OFFSET), %l5 | |
172 | or %l5, %lo(STACK_OFFSET), %l5 | |
173 | add %curptr, %l5, %sp | |
174 | ||
175 | /* Build rest of pt_regs. */ | |
176 | STORE_PT_INS(sp) | |
177 | STORE_PT_PRIV(sp, t_psr, t_pc, t_npc) | |
178 | ||
179 | /* re-set trap time %wim value */ | |
180 | wr %t_wim, 0x0, %wim | |
181 | ||
182 | /* Fix users window mask and buffer save count. */ | |
183 | mov 0x1, %g5 | |
184 | sll %g5, %g3, %g5 | |
185 | st %g5, [%curptr + TI_UWINMASK] ! one live user window still | |
186 | st %g0, [%curptr + TI_W_SAVED] ! no windows in the buffer | |
187 | ||
188 | wr %t_psr, PSR_ET, %psr ! enable traps | |
189 | nop | |
190 | call window_underflow_fault | |
191 | mov %g4, %o0 | |
192 | ||
193 | b ret_trap_entry | |
194 | clr %l6 | |
195 | ||
196 | fwin_user_stack_is_ok: | |
197 | /* LOCATION: Window 'W' */ | |
198 | ||
199 | /* The users stack area is kosher and mapped, load the | |
200 | * window and fall through to the finish up routine. | |
201 | */ | |
202 | LOAD_WINDOW(sp) | |
203 | ||
204 | /* Round and round she goes... */ | |
205 | save %g0, %g0, %g0 /* Save to window 'O' */ | |
206 | save %g0, %g0, %g0 /* Save to window 'T' */ | |
207 | /* Where she'll trap nobody knows... */ | |
208 | ||
209 | /* LOCATION: Window 'T' */ | |
210 | ||
211 | fwin_user_finish_up: | |
212 | /* LOCATION: Window 'T' */ | |
213 | ||
214 | wr %t_psr, 0x0, %psr | |
215 | WRITE_PAUSE | |
216 | ||
217 | jmp %t_pc | |
218 | rett %t_npc | |
219 | ||
220 | /* Here come the architecture specific checks for stack. | |
221 | * mappings. Note that unlike the window overflow handler | |
222 | * we only need to check whether the user can read from | |
223 | * the appropriate addresses. Also note that we are in | |
224 | * an invalid window which will be loaded, and this means | |
225 | * that until we actually load the window up we are free | |
226 | * to use any of the local registers contained within. | |
227 | * | |
228 | * On success these routine branch to fwin_user_stack_is_ok | |
229 | * if the area at %sp is user readable and the window still | |
230 | * needs to be loaded, else fwin_user_finish_up if the | |
231 | * routine has done the loading itself. On failure (bogus | |
232 | * user stack) the routine shall branch to the label called | |
233 | * fwin_user_stack_is_bolixed. | |
234 | * | |
235 | * Contrary to the arch-specific window overflow stack | |
236 | * check routines in wof.S, these routines are free to use | |
237 | * any of the local registers they want to as this window | |
238 | * does not belong to anyone at this point, however the | |
239 | * outs and ins are still verboten as they are part of | |
240 | * 'someone elses' window possibly. | |
241 | */ | |
242 | ||
1da177e4 LT |
243 | .globl srmmu_fwin_stackchk |
244 | srmmu_fwin_stackchk: | |
245 | /* LOCATION: Window 'W' */ | |
246 | ||
247 | /* Caller did 'andcc %sp, 0x7, %g0' */ | |
248 | bne fwin_user_stack_is_bolixed | |
249 | sethi %hi(PAGE_OFFSET), %l5 | |
250 | ||
251 | /* Check if the users stack is in kernel vma, then our | |
252 | * trial and error technique below would succeed for | |
253 | * the 'wrong' reason. | |
254 | */ | |
255 | mov AC_M_SFSR, %l4 | |
256 | cmp %l5, %sp | |
257 | bleu fwin_user_stack_is_bolixed | |
1ec8cf62 SR |
258 | LEON_PI( lda [%l4] ASI_LEON_MMUREGS, %g0) ! clear fault status |
259 | SUN_PI_( lda [%l4] ASI_M_MMUREGS, %g0) ! clear fault status | |
1da177e4 LT |
260 | |
261 | /* The technique is, turn off faults on this processor, | |
262 | * just let the load rip, then check the sfsr to see if | |
263 | * a fault did occur. Then we turn on fault traps again | |
264 | * and branch conditionally based upon what happened. | |
265 | */ | |
1ec8cf62 SR |
266 | LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %l5) ! read mmu-ctrl reg |
267 | SUN_PI_(lda [%g0] ASI_M_MMUREGS, %l5) ! read mmu-ctrl reg | |
1da177e4 | 268 | or %l5, 0x2, %l5 ! turn on no-fault bit |
1ec8cf62 SR |
269 | LEON_PI(sta %l5, [%g0] ASI_LEON_MMUREGS) ! store it |
270 | SUN_PI_(sta %l5, [%g0] ASI_M_MMUREGS) ! store it | |
1da177e4 LT |
271 | |
272 | /* Cross fingers and go for it. */ | |
273 | LOAD_WINDOW(sp) | |
274 | ||
275 | /* A penny 'saved'... */ | |
276 | save %g0, %g0, %g0 | |
277 | save %g0, %g0, %g0 | |
278 | /* Is a BADTRAP earned... */ | |
279 | ||
280 | /* LOCATION: Window 'T' */ | |
281 | ||
1ec8cf62 SR |
282 | LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %twin_tmp1) ! load mmu-ctrl again |
283 | SUN_PI_(lda [%g0] ASI_M_MMUREGS, %twin_tmp1) ! load mmu-ctrl again | |
284 | andn %twin_tmp1, 0x2, %twin_tmp1 ! clear no-fault bit | |
285 | LEON_PI(sta %twin_tmp1, [%g0] ASI_LEON_MMUREGS) ! store it | |
286 | SUN_PI_(sta %twin_tmp1, [%g0] ASI_M_MMUREGS) ! store it | |
1da177e4 LT |
287 | |
288 | mov AC_M_SFAR, %twin_tmp2 | |
1ec8cf62 SR |
289 | LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %g0) ! read fault address |
290 | SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %g0) ! read fault address | |
1da177e4 LT |
291 | |
292 | mov AC_M_SFSR, %twin_tmp2 | |
1ec8cf62 SR |
293 | LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS, %twin_tmp2) ! read fault status |
294 | SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %twin_tmp2) ! read fault status | |
295 | andcc %twin_tmp2, 0x2, %g0 ! did fault occur? | |
1da177e4 | 296 | |
1ec8cf62 | 297 | bne 1f ! yep, cleanup |
1da177e4 LT |
298 | nop |
299 | ||
300 | wr %t_psr, 0x0, %psr | |
301 | nop | |
302 | b fwin_user_finish_up + 0x4 | |
303 | nop | |
304 | ||
305 | /* Did I ever tell you about my window lobotomy? | |
306 | * anyways... fwin_user_stack_is_bolixed expects | |
307 | * to be in window 'W' so make it happy or else | |
308 | * we watchdog badly. | |
309 | */ | |
310 | 1: | |
311 | restore %g0, %g0, %g0 | |
312 | b fwin_user_stack_is_bolixed ! oh well | |
313 | restore %g0, %g0, %g0 |