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