1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * etrap.S: Sparc trap window preparation for entry into the
4 * Linux kernel.
5 *
6 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
7 */
8
9#include <asm/head.h>
10#include <asm/asi.h>
11#include <asm/contregs.h>
12#include <asm/page.h>
13#include <asm/psr.h>
14#include <asm/ptrace.h>
15#include <asm/winmacro.h>
16#include <asm/asmmacro.h>
17#include <asm/thread_info.h>
18
19/* Registers to not touch at all. */
20#define t_psr l0 /* Set by caller */
21#define t_pc l1 /* Set by caller */
22#define t_npc l2 /* Set by caller */
23#define t_wim l3 /* Set by caller */
24#define t_twinmask l4 /* Set at beginning of this entry routine. */
25#define t_kstack l5 /* Set right before pt_regs frame is built */
26#define t_retpc l6 /* If you change this, change winmacro.h header file */
27#define t_systable l7 /* Never touch this, could be the syscall table ptr. */
28#define curptr g6 /* Set after pt_regs frame is built */
29
30 .text
31 .align 4
32
33 /* SEVEN WINDOW PATCH INSTRUCTIONS */
34 .globl tsetup_7win_patch1, tsetup_7win_patch2
35 .globl tsetup_7win_patch3, tsetup_7win_patch4
36 .globl tsetup_7win_patch5, tsetup_7win_patch6
37tsetup_7win_patch1: sll %t_wim, 0x6, %t_wim
38tsetup_7win_patch2: and %g2, 0x7f, %g2
39tsetup_7win_patch3: and %g2, 0x7f, %g2
40tsetup_7win_patch4: and %g1, 0x7f, %g1
41tsetup_7win_patch5: sll %t_wim, 0x6, %t_wim
42tsetup_7win_patch6: and %g2, 0x7f, %g2
43 /* END OF PATCH INSTRUCTIONS */
44
45 /* At trap time, interrupts and all generic traps do the
46 * following:
47 *
48 * rd %psr, %l0
49 * b some_handler
50 * rd %wim, %l3
51 * nop
52 *
53 * Then 'some_handler' if it needs a trap frame (ie. it has
54 * to call c-code and the trap cannot be handled in-window)
55 * then it does the SAVE_ALL macro in entry.S which does
56 *
57 * sethi %hi(trap_setup), %l4
58 * jmpl %l4 + %lo(trap_setup), %l6
59 * nop
60 */
61
62 /* 2 3 4 window number
63 * -----
64 * O T S mnemonic
65 *
66 * O == Current window before trap
67 * T == Window entered when trap occurred
68 * S == Window we will need to save if (1<<T) == %wim
69 *
70 * Before execution gets here, it must be guaranteed that
71 * %l0 contains trap time %psr, %l1 and %l2 contain the
72 * trap pc and npc, and %l3 contains the trap time %wim.
73 */
74
75 .globl trap_setup, tsetup_patch1, tsetup_patch2
76 .globl tsetup_patch3, tsetup_patch4
77 .globl tsetup_patch5, tsetup_patch6
78trap_setup:
79 /* Calculate mask of trap window. See if from user
80 * or kernel and branch conditionally.
81 */
82 mov 1, %t_twinmask
83 andcc %t_psr, PSR_PS, %g0 ! fromsupv_p = (psr & PSR_PS)
84 be trap_setup_from_user ! nope, from user mode
85 sll %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
86
87 /* From kernel, allocate more kernel stack and
88 * build a pt_regs trap frame.
89 */
90 sub %fp, (STACKFRAME_SZ + TRACEREG_SZ), %t_kstack
91 STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
92
93 /* See if we are in the trap window. */
94 andcc %t_twinmask, %t_wim, %g0
95 bne 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 jmpl %t_retpc + 0x8, %g0 ! return to caller
102 mov %t_kstack, %sp ! jump onto new stack
103
104trap_setup_kernel_spill:
105 ld [%curptr + TI_UWINMASK], %g1
106 orcc %g0, %g1, %g0
107 bne trap_setup_user_spill ! there are some user windows, yuck
108 /* Spill from kernel, but only kernel windows, adjust
109 * %wim and go.
110 */
111 srl %t_wim, 0x1, %g2 ! begin computation of new %wim
112tsetup_patch1:
113 sll %t_wim, 0x7, %t_wim ! patched on 7 window Sparcs
114 or %t_wim, %g2, %g2
115tsetup_patch2:
116 and %g2, 0xff, %g2 ! patched on 7 window Sparcs
117
118 save %g0, %g0, %g0
119
120 /* Set new %wim value */
121 wr %g2, 0x0, %wim
122
123 /* Save the kernel window onto the corresponding stack. */
124 STORE_WINDOW(sp)
125
126 restore %g0, %g0, %g0
127
128 jmpl %t_retpc + 0x8, %g0 ! return to caller
129 mov %t_kstack, %sp ! and onto new kernel stack
130
131#define STACK_OFFSET (THREAD_SIZE - TRACEREG_SZ - STACKFRAME_SZ)
132
133trap_setup_from_user:
134 /* We can't use %curptr yet. */
135 LOAD_CURRENT(t_kstack, t_twinmask)
136
137 sethi %hi(STACK_OFFSET), %t_twinmask
138 or %t_twinmask, %lo(STACK_OFFSET), %t_twinmask
139 add %t_kstack, %t_twinmask, %t_kstack
140
141 mov 1, %t_twinmask
142 sll %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
143
144 /* Build pt_regs frame. */
145 STORE_PT_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
146
147#if 0
148 /* If we're sure every task_struct is THREAD_SIZE aligned,
149 we can speed this up. */
150 sethi %hi(STACK_OFFSET), %curptr
151 or %curptr, %lo(STACK_OFFSET), %curptr
152 sub %t_kstack, %curptr, %curptr
153#else
154 sethi %hi(~(THREAD_SIZE - 1)), %curptr
155 and %t_kstack, %curptr, %curptr
156#endif
157
158 /* Clear current_thread_info->w_saved */
159 st %g0, [%curptr + TI_W_SAVED]
160
161 /* See if we are in the trap window. */
162 andcc %t_twinmask, %t_wim, %g0
163 bne trap_setup_user_spill ! yep we are
164 orn %g0, %t_twinmask, %g1 ! negate trap win mask into %g1
165
166 /* Trap from user, but not into the invalid window.
167 * Calculate new umask. The way this works is,
168 * any window from the %wim at trap time until
169 * the window right before the one we are in now,
170 * is a user window. A diagram:
171 *
172 * 7 6 5 4 3 2 1 0 window number
173 * ---------------
174 * I L T mnemonic
175 *
176 * Window 'I' is the invalid window in our example,
177 * window 'L' is the window the user was in when
178 * the trap occurred, window T is the trap window
179 * we are in now. So therefore, windows 5, 4 and
180 * 3 are user windows. The following sequence
181 * computes the user winmask to represent this.
182 */
183 subcc %t_wim, %t_twinmask, %g2
184 bneg,a 1f
185 sub %g2, 0x1, %g2
1861:
187 andn %g2, %t_twinmask, %g2
188tsetup_patch3:
189 and %g2, 0xff, %g2 ! patched on 7win Sparcs
190 st %g2, [%curptr + TI_UWINMASK] ! store new umask
191
192 jmpl %t_retpc + 0x8, %g0 ! return to caller
193 mov %t_kstack, %sp ! and onto kernel stack
194
195trap_setup_user_spill:
196 /* A spill occurred from either kernel or user mode
197 * and there exist some user windows to deal with.
198 * A mask of the currently valid user windows
199 * is in %g1 upon entry to here.
200 */
201
202tsetup_patch4:
203 and %g1, 0xff, %g1 ! patched on 7win Sparcs, mask
204 srl %t_wim, 0x1, %g2 ! compute new %wim
205tsetup_patch5:
206 sll %t_wim, 0x7, %t_wim ! patched on 7win Sparcs
207 or %t_wim, %g2, %g2 ! %g2 is new %wim
208tsetup_patch6:
209 and %g2, 0xff, %g2 ! patched on 7win Sparcs
210 andn %g1, %g2, %g1 ! clear this bit in %g1
211 st %g1, [%curptr + TI_UWINMASK]
212
213 save %g0, %g0, %g0
214
215 wr %g2, 0x0, %wim
216
217 /* Call MMU-architecture dependent stack checking
218 * routine.
219 */
220 b tsetup_srmmu_stackchk
221 andcc %sp, 0x7, %g0
222
223 /* Architecture specific stack checking routines. When either
224 * of these routines are called, the globals are free to use
225 * as they have been safely stashed on the new kernel stack
226 * pointer. Thus the definition below for simplicity.
227 */
228#define glob_tmp g1
229
230 .globl tsetup_srmmu_stackchk
231tsetup_srmmu_stackchk:
232 /* Check results of callers andcc %sp, 0x7, %g0 */
233 bne trap_setup_user_stack_is_bolixed
234 sethi %hi(PAGE_OFFSET), %glob_tmp
235
236 cmp %glob_tmp, %sp
237 bleu,a 1f
238LEON_PI( lda [%g0] ASI_LEON_MMUREGS, %glob_tmp) ! read MMU control
239SUN_PI_( lda [%g0] ASI_M_MMUREGS, %glob_tmp) ! read MMU control
240
241trap_setup_user_stack_is_bolixed:
242 /* From user/kernel into invalid window w/bad user
243 * stack. Save bad user stack, and return to caller.
244 */
245 SAVE_BOLIXED_USER_STACK(curptr, g3)
246 restore %g0, %g0, %g0
247
248 jmpl %t_retpc + 0x8, %g0
249 mov %t_kstack, %sp
250
2511:
252 /* Clear the fault status and turn on the no_fault bit. */
253 or %glob_tmp, 0x2, %glob_tmp ! or in no_fault bit
254LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS) ! set it
255SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS) ! set it
256
257 /* Dump the registers and cross fingers. */
258 STORE_WINDOW(sp)
259
260 /* Clear the no_fault bit and check the status. */
261 andn %glob_tmp, 0x2, %glob_tmp
262LEON_PI(sta %glob_tmp, [%g0] ASI_LEON_MMUREGS)
263SUN_PI_(sta %glob_tmp, [%g0] ASI_M_MMUREGS)
264
265 mov AC_M_SFAR, %glob_tmp
266LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %g0)
267SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %g0)
268
269 mov AC_M_SFSR, %glob_tmp
270LEON_PI(lda [%glob_tmp] ASI_LEON_MMUREGS, %glob_tmp)! save away status of winstore
271SUN_PI_(lda [%glob_tmp] ASI_M_MMUREGS, %glob_tmp) ! save away status of winstore
272
273 andcc %glob_tmp, 0x2, %g0 ! did we fault?
274 bne trap_setup_user_stack_is_bolixed ! failure
275 nop
276
277 restore %g0, %g0, %g0
278
279 jmpl %t_retpc + 0x8, %g0
280 mov %t_kstack, %sp
281
282

source code of linux/arch/sparc/kernel/etrap_32.S