1 /* $Id: etrap.S,v 1.10 1995/11/25 00:57:58 davem Exp $ 2 * etrap.S: Sparc trap window preparation for entry into the 3 * Linux kernel. 4 * 5 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu) 6 */ 7
8 #include <asm/cprefix.h>
9 #include <asm/head.h>
10 #include <asm/page.h>
11 #include <asm/psr.h>
12 #include <asm/ptrace.h>
13 #include <asm/winmacro.h>
14
15 /* Registers to not touch at all. */ 16 #define t_psr l0 /* Set by caller */ 17 #define t_pc l1 /* Set by caller */ 18 #define t_npc l2 /* Set by caller */ 19 #define t_wim l3 /* Set by caller */ 20 #define t_twinmask l4 /* Set at beginning of this entry routine. */ 21 #define t_kstack l5 /* Set right before pt_regs frame is built */ 22 #define t_retpc l6 /* If you change this, change winmacro.h header file */ 23 #define t_systable l7 /* Never touch this, could be the syscall table ptr. */ 24 #define curptr g4 /* Set after pt_regs frame is built */ 25
26 .text
27 .align 4
28
29 /* SEVEN WINDOW PATCH INSTRUCTIONS */ 30 .globl tsetup_7win_patch1, tsetup_7win_patch2
31 .globl tsetup_7win_patch3, tsetup_7win_patch4
32 .globl tsetup_7win_patch5, tsetup_7win_patch6
33 tsetup_7win_patch1: sll %t_wim, 0x6, %t_wim
34 tsetup_7win_patch2: and %g2, 0x7f, %g2
35 tsetup_7win_patch3: and %g2, 0x7f, %g2
36 tsetup_7win_patch4: and %g1, 0x7f, %g1
37 tsetup_7win_patch5: sll %t_wim, 0x6, %t_wim
38 tsetup_7win_patch6: and %g2, 0x7f, %g2
39 /* END OF PATCH INSTRUCTIONS */ 40
41 /* At trap time, interrupts and all generic traps do the 42 * following: 43 * 44 * rd %psr, %l0 45 * b some_handler 46 * rd %wim, %l3 47 * nop 48 * 49 * Then 'some_handler' if it needs a trap frame (ie. it has 50 * to call c-code and the trap cannot be handled in-window) 51 * then it does the SAVE_ALL macro in entry.S which does 52 * 53 * sethi %hi(trap_setup), %l4 54 * jmpl %l4 + %lo(trap_setup), %l6 55 * mov 1, %l4 56 */ 57
58 /* 2 3 4 window number 59 * ----- 60 * O T S mnemonic 61 * 62 * O == Current window before trap 63 * T == Window entered when trap occurred 64 * S == Window we will need to save if (1<<T) == %wim 65 * 66 * Before execution gets here, it must be guarenteed that 67 * %l0 contains trap time %psr, %l1 and %l2 contain the 68 * trap pc and npc, and %l3 contains the trap time %wim. 69 */ 70
71 .globl trap_setup, tsetup_patch1, tsetup_patch2
72 .globl tsetup_patch3, tsetup_patch4
73 .globl tsetup_patch5, tsetup_patch6
74 trap_setup:
75 /* Calculate mask of trap window. See if from user 76 * or kernel and branch conditionally. 77 */ 78 mov 1, %t_twinmask
79 sll %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
80 andcc %t_psr, PSR_PS, %g0 ! fromsupv_p = (psr & PSR_PS)
81 be trap_setup_from_user ! nope, from user mode
82 nop
83
84 /* From kernel, allocate more kernel stack and 85 * build a pt_regs trap frame. 86 */ 87 sub %fp, (STACKFRAME_SZ + TRACEREG_SZ), %t_kstack
88 STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, t_wim, g2)
89
90 /* See if we are in the trap window. */ 91 andcc %t_twinmask, %t_wim, %g0
92 be 1f
93 nop
94
95 b trap_setup_kernel_spill ! in trap window, clean up
96 nop
97
98 /* Trap from kernel with a window available. 99 * Just do it... 100 */ 101 1:
102 mov %t_kstack, %sp ! jump onto new stack
103 jmpl %t_retpc + 0x8, %g0 ! return to caller
104 nop
105
106 trap_setup_kernel_spill:
107 LOAD_CURRENT(curptr)
108 ld [%curptr + THREAD_UMASK], %g1
109 orcc %g0, %g1, %g0
110 bne trap_setup_user_spill ! there are some user windows, yuck
111 nop
112
113 /* Spill from kernel, but only kernel windows, adjust 114 * %wim and go. 115 */ 116 srl %t_wim, 0x1, %g2 ! begin computation of new %wim
117 tsetup_patch1: sll %t_wim, 0x7, %t_wim ! patched on 7 window Sparcs
118 or %t_wim, %g2, %g2
119 tsetup_patch2: and %g2, 0xff, %g2 ! patched on 7 window Sparcs
120
121 save %g0, %g0, %g0
122
123 /* Set new %wim value */ 124 wr %g2, 0x0, %wim
125 WRITE_PAUSE
126
127 /* Save the kernel window onto the corresponding stack. */ 128 STORE_WINDOW(sp)
129
130 restore %g0, %g0, %g0
131
132 mov %t_kstack, %sp ! and onto new kernel stack
133 jmpl %t_retpc + 0x8, %g0 ! return to caller
134 nop
135
136 trap_setup_from_user:
137 /* We can't use %curptr yet. */ 138 LOAD_CURRENT(t_kstack)
139 ld [%t_kstack + TASK_KSTACK_PG], %t_kstack
140
141 /* Build pt_regs frame. */ 142 add %t_kstack, (PAGE_SIZE - STACKFRAME_SZ - TRACEREG_SZ), %t_kstack
143 STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, t_wim, g2)
144
145 /* Clear current->tss.w_saved */ 146 LOAD_CURRENT(curptr)
147 st %g0, [%curptr + THREAD_W_SAVED]
148
149 /* See if we are in the trap window. */ 150 andcc %t_twinmask, %t_wim, %g0
151 bne trap_setup_user_spill ! yep we are
152 orn %g0, %t_twinmask, %g1 ! negate trap win mask into %g1
153
154 /* Trap from user, but not into the invalid window. 155 * Calculate new umask. The way this works is, 156 * any window from the %wim at trap time until 157 * the window right before the one we are in now, 158 * is a user window. A diagram: 159 * 160 * 7 6 5 4 3 2 1 0 window number 161 * --------------- 162 * I L T mnemonic 163 * 164 * Window 'I' is the invalid window in our example, 165 * window 'L' is the window the user was in when 166 * the trap occurred, window T is the trap window 167 * we are in now. So therefore, windows 5, 4 and 168 * 3 are user windows. The following sequence 169 * computes the user winmask to represent this. 170 */ 171 subcc %t_wim, %t_twinmask, %g2
172 bneg,a 1f
173 sub %g2, 0x1, %g2
174 1:
175 andn %g2, %t_twinmask, %g2
176 tsetup_patch3: and %g2, 0xff, %g2 ! patched on 7win Sparcs
177 st %g2, [%curptr + THREAD_UMASK] ! store new umask
178
179 mov %t_kstack, %sp ! and onto kernel stack
180 jmpl %t_retpc + 0x8, %g0 ! return to caller
181 nop
182
183 trap_setup_user_spill:
184 /* A spill occured from either kernel or user mode 185 * and there exist some user windows to deal with. 186 * A mask of the currently valid user windows 187 * is in %g1 upon entry to here. 188 */ 189
190 tsetup_patch4: and %g1, 0xff, %g1 ! patched on 7win Sparcs, mask
191 srl %t_wim, 0x1, %g2 ! compute new %wim
192 tsetup_patch5: sll %t_wim, 0x7, %t_wim ! patched on 7win Sparcs
193 or %t_wim, %g2, %g2 ! %g2 is new %wim
194 tsetup_patch6: and %g2, 0xff, %g2 ! patched on 7win Sparcs
195 andn %g1, %g2, %g1 ! clear this bit in %g1
196 st %g1, [%curptr + THREAD_UMASK]
197
198 save %g0, %g0, %g0
199
200 wr %g2, 0x0, %wim
201 WRITE_PAUSE
202
203 /* Call MMU-architecture dependant stack checking 204 * routine. 205 */ 206 .globl C_LABEL(tsetup_mmu_patchme)
207 C_LABEL(tsetup_mmu_patchme): b C_LABEL(tsetup_sun4c_stackchk)
208 andcc %sp, 0x7, %g0
209
210 trap_setup_user_stack_is_bolixed:
211 /* From user/kernel into invalid window w/bad user 212 * stack. Save bad user stack, and return to caller. 213 */ 214 SAVE_BOLIXED_USER_STACK(curptr, g3)
215 restore %g0, %g0, %g0
216 mov %t_kstack, %sp
217 jmpl %t_retpc + 0x8, %g0
218 nop
219
220 trap_setup_good_ustack:
221 STORE_WINDOW(sp)
222
223 trap_setup_finish_up:
224 restore %g0, %g0, %g0
225 mov %t_kstack, %sp
226 jmpl %t_retpc + 0x8, %g0
227 nop
228
229 /* Architecture specific stack checking routines. When either 230 * of these routines are called, the globals are free to use 231 * as they have been safely stashed on the new kernel stack 232 * pointer. Thus the definition below for simplicity. 233 */ 234 #define glob_tmp g1
235
236 .globl C_LABEL(tsetup_sun4c_stackchk)
237 .globl C_LABEL(tsetup_srmmu_stackchk)
238 C_LABEL(tsetup_sun4c_stackchk):
239 /* Done by caller: andcc %sp, 0x7, %g0 */ 240 be 1f
241 sra %sp, 29, %glob_tmp
242
243 b trap_setup_user_stack_is_bolixed
244 nop
245
246 1:
247 add %glob_tmp, 0x1, %glob_tmp
248 andncc %glob_tmp, 0x1, %g0
249 be 1f
250 and %sp, 0xfff, %glob_tmp ! delay slot
251
252 b trap_setup_user_stack_is_bolixed
253 nop
254
255 /* See if our dump area will be on more than one 256 * page. 257 */ 258 1:
259 add %glob_tmp, 0x38, %glob_tmp
260 andncc %glob_tmp, 0xff8, %g0
261 be tsetup_sun4c_onepage ! only one page to check
262 lda [%sp] ASI_PTE, %glob_tmp ! have to check first page anyways
263
264 tsetup_sun4c_twopages:
265 /* Is first page ok permission wise? */ 266 srl %glob_tmp, 29, %glob_tmp
267 cmp %glob_tmp, 0x6
268 be 1f
269 add %sp, 0x38, %glob_tmp /* Is second page in vma hole? */ 270
271 b trap_setup_user_stack_is_bolixed
272 nop
273
274 1:
275 sra %glob_tmp, 29, %glob_tmp
276 add %glob_tmp, 0x1, %glob_tmp
277 andncc %glob_tmp, 0x1, %g0
278 be 1f
279 add %sp, 0x38, %glob_tmp
280
281 b trap_setup_user_stack_is_bolixed
282 nop
283
284 1:
285 lda [%glob_tmp] ASI_PTE, %glob_tmp
286
287 tsetup_sun4c_onepage:
288 srl %glob_tmp, 29, %glob_tmp
289 cmp %glob_tmp, 0x6 ! can user write to it?
290 be trap_setup_good_ustack ! success
291 nop
292
293 b trap_setup_user_stack_is_bolixed
294 nop
295
296 C_LABEL(tsetup_srmmu_stackchk):
297 /* Check results of callers andcc %sp, 0x7, %g0 */ 298 bne trap_setup_user_stack_is_bolixed
299 sethi %hi(KERNBASE), %glob_tmp
300 cmp %glob_tmp, %sp
301 bleu trap_setup_user_stack_is_bolixed
302 nop
303
304 /* Clear the fault status and turn on the no_fault bit. */ 305 mov AC_M_SFSR, %glob_tmp ! delay from above...
306 lda [%glob_tmp] ASI_M_MMUREGS, %g0 ! eat SFSR
307 lda [%g0] ASI_M_MMUREGS, %glob_tmp ! read MMU control
308 or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit
309 sta %glob_tmp, [%g0] ASI_M_MMUREGS ! set it
310
311 /* Dump the registers and cross fingers. */ 312 STORE_WINDOW(sp)
313
314 /* Clear the no_fault bit and check the status. */ 315 andn %glob_tmp, 0x2, %glob_tmp
316 sta %glob_tmp, [%g0] ASI_M_MMUREGS
317 mov AC_M_SFAR, %glob_tmp
318 lda [%glob_tmp] ASI_M_MMUREGS, %g0
319 mov AC_M_SFSR, %glob_tmp
320 lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp
321 andcc %glob_tmp, 0x2, %g0 ! did we fault?
322 be trap_setup_finish_up ! cool beans, success
323 nop
324
325 b trap_setup_user_stack_is_bolixed ! we faulted, ugh
326 nop
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