1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * wuf.S: Window underflow trap handler for th
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 ma
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
26
27 /* Now macros for the available scratch regist
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 t
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
45 * where if any user windows are activ
46 * be set in to mask. If no user wind
47 * will be all zeroes.
48 */
49
50 /* To get an idea of what has just hap
51 * trap take a look at this diagram:
52 *
53 * 1 2 3 4 <-- Window num
54 * ----------
55 * T O W I <-- Symbolic n
56 *
57 * O == the window that execution
58 * the restore was attempted
59 *
60 * T == the trap itself has save'
61 * window
62 *
63 * W == this window is the one wh
64 * and must be made valid pl
65 * stack
66 *
67 * I == this window will be the i
68 * are done and return from
69 */
70
71 /* BEGINNING OF PATCH INSTRUCTIONS */
72
73 /* On 7-window Sparc the boot code pat
74 * with the following instruction.
75 */
76 .globl fnwin_patch1_7win, fnwin_patch
77 fnwin_patch1_7win: srl %t_wim, 6, %tw
78 fnwin_patch2_7win: and %twin_tmp1, 0x
79 /* END OF PATCH INSTRUCTIONS */
80
81 .globl fill_window_entry, fnwin_patch
82 fill_window_entry:
83 /* LOCATION: Window 'T' */
84
85 /* Compute what the new %wim is going
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
91 fnwin_patch2: and %twin_tmp1, 0xff, %twi
92
93 wr %twin_tmp1, 0x0, %wim /* Mak
94
95 andcc %t_psr, PSR_PS, %g0
96 be fwin_from_user
97 restore %g0, %g0, %g0
98
99 /* Trapped from kernel, we trust that
100 * 'over restore' sorta speak and just
101 * from the stack and return. Easy en
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) /* Loa
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
120 * return from trap. This is the simp
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 /* Res
132
133 /* LOCATION: Window 'W' */
134
135 /* Branch to the stack validation rout
136 b srmmu_fwin_stackchk
137 andcc %sp, 0x7, %g0
138
139 #define STACK_OFFSET (THREAD_SIZE - TRACEREG_S
140
141 fwin_user_stack_is_bolixed:
142 /* LOCATION: Window 'W' */
143
144 /* Place a pt_regs frame on the kernel
145 * to the trap window and call c-code
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 c
158 mov %l4, %curptr
159
160 save %g0, %g0, %g0
161
162 /* LOCATION: Window 'O' */
163
164 rd %psr, %g3 /* Rea
165 mov %fp, %g4 /* Sav
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 sa
183 mov 0x1, %g5
184 sll %g5, %g3, %g5
185 st %g5, [%curptr + TI_UWINMASK]
186 st %g0, [%curptr + TI_W_SAVED]
187
188 wr %t_psr, PSR_ET, %psr
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
200 * window and fall through to the fini
201 */
202 LOAD_WINDOW(sp)
203
204 /* Round and round she goes... */
205 save %g0, %g0, %g0 /* Sav
206 save %g0, %g0, %g0 /* Sav
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
221 * mappings. Note that unlike the win
222 * we only need to check whether the u
223 * the appropriate addresses. Also no
224 * an invalid window which will be loa
225 * that until we actually load the win
226 * to use any of the local registers c
227 *
228 * On success these routine branch to
229 * if the area at %sp is user readable
230 * needs to be loaded, else fwin_user_
231 * routine has done the loading itself
232 * user stack) the routine shall branc
233 * fwin_user_stack_is_bolixed.
234 *
235 * Contrary to the arch-specific windo
236 * check routines in wof.S, these rout
237 * any of the local registers they wan
238 * does not belong to anyone at this p
239 * outs and ins are still verboten as
240 * 'someone elses' window possibly.
241 */
242
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 kern
252 * trial and error technique below wou
253 * the 'wrong' reason.
254 */
255 mov AC_M_SFSR, %l4
256 cmp %l5, %sp
257 bleu fwin_user_stack_is_bolixed
258 LEON_PI( lda [%l4] ASI_LEON_MMUREGS, %g0)
259 SUN_PI_( lda [%l4] ASI_M_MMUREGS, %g0)
260
261 /* The technique is, turn off faults o
262 * just let the load rip, then check t
263 * a fault did occur. Then we turn on
264 * and branch conditionally based upon
265 */
266 LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %l5)
267 SUN_PI_(lda [%g0] ASI_M_MMUREGS, %l5)
268 or %l5, 0x2, %l5
269 LEON_PI(sta %l5, [%g0] ASI_LEON_MMUREGS)
270 SUN_PI_(sta %l5, [%g0] ASI_M_MMUREGS)
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
282 LEON_PI(lda [%g0] ASI_LEON_MMUREGS, %twin_
283 SUN_PI_(lda [%g0] ASI_M_MMUREGS, %twin_tmp
284 andn %twin_tmp1, 0x2, %twin_tmp1
285 LEON_PI(sta %twin_tmp1, [%g0] ASI_LEON_MMU
286 SUN_PI_(sta %twin_tmp1, [%g0] ASI_M_MMUREG
287
288 mov AC_M_SFAR, %twin_tmp2
289 LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS,
290 SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %g
291
292 mov AC_M_SFSR, %twin_tmp2
293 LEON_PI(lda [%twin_tmp2] ASI_LEON_MMUREGS,
294 SUN_PI_(lda [%twin_tmp2] ASI_M_MMUREGS, %t
295 andcc %twin_tmp2, 0x2, %g0
296
297 bne 1f
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
306 * anyways... fwin_user_stack_is_bolix
307 * to be in window 'W' so make it happ
308 * we watchdog badly.
309 */
310 1:
311 restore %g0, %g0, %g0
312 b fwin_user_stack_is_bolixed
313 restore %g0, %g0, %g0
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