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1/*
2 * arch/sh64/kernel/switchto.S
3 *
4 * sh64 context switch
5 *
6 * Copyright (C) 2004 Richard Curnow
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
10 * for more details.
11*/
12
13 .section .text..SHmedia32,"ax"
14 .little
15
16 .balign 32
17
18 .type sh64_switch_to,@function
19 .global sh64_switch_to
20 .global __sh64_switch_to_end
21sh64_switch_to:
22
23/* Incoming args
24 r2 - prev
25 r3 - &prev->thread
26 r4 - next
27 r5 - &next->thread
28
29 Outgoing results
30 r2 - last (=prev) : this just stays in r2 throughout
31
32 Want to create a full (struct pt_regs) on the stack to allow backtracing
33 functions to work. However, we only need to populate the callee-save
34 register slots in this structure; since we're a function our ancestors must
35 have themselves preserved all caller saved state in the stack. This saves
36 some wasted effort since we won't need to look at the values.
37
38 In particular, all caller-save registers are immediately available for
39 scratch use.
40
41*/
42
43#define FRAME_SIZE (76*8 + 8)
44
45 movi FRAME_SIZE, r0
46 sub.l r15, r0, r15
47 ! Do normal-style register save to support backtrace
48
49 st.l r15, 0, r18 ! save link reg
50 st.l r15, 4, r14 ! save fp
51 add.l r15, r63, r14 ! setup frame pointer
52
53 ! hopefully this looks normal to the backtrace now.
54
55 addi.l r15, 8, r1 ! base of pt_regs
56 addi.l r1, 24, r0 ! base of pt_regs.regs
57 addi.l r0, (63*8), r8 ! base of pt_regs.trregs
58
59 /* Note : to be fixed?
60 struct pt_regs is really designed for holding the state on entry
61 to an exception, i.e. pc,sr,regs etc. However, for the context
62 switch state, some of this is not required. But the unwinder takes
63 struct pt_regs * as an arg so we have to build this structure
64 to allow unwinding switched tasks in show_state() */
65
66 st.q r0, ( 9*8), r9
67 st.q r0, (10*8), r10
68 st.q r0, (11*8), r11
69 st.q r0, (12*8), r12
70 st.q r0, (13*8), r13
71 st.q r0, (14*8), r14 ! for unwind, want to look as though we took a trap at
72 ! the point where the process is left in suspended animation, i.e. current
73 ! fp here, not the saved one.
74 st.q r0, (16*8), r16
75
76 st.q r0, (24*8), r24
77 st.q r0, (25*8), r25
78 st.q r0, (26*8), r26
79 st.q r0, (27*8), r27
80 st.q r0, (28*8), r28
81 st.q r0, (29*8), r29
82 st.q r0, (30*8), r30
83 st.q r0, (31*8), r31
84 st.q r0, (32*8), r32
85 st.q r0, (33*8), r33
86 st.q r0, (34*8), r34
87 st.q r0, (35*8), r35
88
89 st.q r0, (44*8), r44
90 st.q r0, (45*8), r45
91 st.q r0, (46*8), r46
92 st.q r0, (47*8), r47
93 st.q r0, (48*8), r48
94 st.q r0, (49*8), r49
95 st.q r0, (50*8), r50
96 st.q r0, (51*8), r51
97 st.q r0, (52*8), r52
98 st.q r0, (53*8), r53
99 st.q r0, (54*8), r54
100 st.q r0, (55*8), r55
101 st.q r0, (56*8), r56
102 st.q r0, (57*8), r57
103 st.q r0, (58*8), r58
104 st.q r0, (59*8), r59
105
106 ! do this early as pta->gettr has no pipeline forwarding (=> 5 cycle latency)
107 ! Use a local label to avoid creating a symbol that will confuse the !
108 ! backtrace
109 pta .Lsave_pc, tr0
110
111 gettr tr5, r45
112 gettr tr6, r46
113 gettr tr7, r47
114 st.q r8, (5*8), r45
115 st.q r8, (6*8), r46
116 st.q r8, (7*8), r47
117
118 ! Now switch context
119 gettr tr0, r9
120 st.l r3, 0, r15 ! prev->thread.sp
121 st.l r3, 8, r1 ! prev->thread.kregs
122 st.l r3, 4, r9 ! prev->thread.pc
123 st.q r1, 0, r9 ! save prev->thread.pc into pt_regs->pc
124
125 ! Load PC for next task (init value or save_pc later)
126 ld.l r5, 4, r18 ! next->thread.pc
127 ! Switch stacks
128 ld.l r5, 0, r15 ! next->thread.sp
129 ptabs r18, tr0
130
131 ! Update current
132 ld.l r4, 4, r9 ! next->thread_info (2nd element of next task_struct)
133 putcon r9, kcr0 ! current = next->thread_info
134
135 ! go to save_pc for a reschedule, or the initial thread.pc for a new process
136 blink tr0, r63
137
138 ! Restore (when we come back to a previously saved task)
139.Lsave_pc:
140 addi.l r15, 32, r0 ! r0 = next's regs
141 addi.l r0, (63*8), r8 ! r8 = next's tr_regs
142
143 ld.q r8, (5*8), r45
144 ld.q r8, (6*8), r46
145 ld.q r8, (7*8), r47
146 ptabs r45, tr5
147 ptabs r46, tr6
148 ptabs r47, tr7
149
150 ld.q r0, ( 9*8), r9
151 ld.q r0, (10*8), r10
152 ld.q r0, (11*8), r11
153 ld.q r0, (12*8), r12
154 ld.q r0, (13*8), r13
155 ld.q r0, (14*8), r14
156 ld.q r0, (16*8), r16
157
158 ld.q r0, (24*8), r24
159 ld.q r0, (25*8), r25
160 ld.q r0, (26*8), r26
161 ld.q r0, (27*8), r27
162 ld.q r0, (28*8), r28
163 ld.q r0, (29*8), r29
164 ld.q r0, (30*8), r30
165 ld.q r0, (31*8), r31
166 ld.q r0, (32*8), r32
167 ld.q r0, (33*8), r33
168 ld.q r0, (34*8), r34
169 ld.q r0, (35*8), r35
170
171 ld.q r0, (44*8), r44
172 ld.q r0, (45*8), r45
173 ld.q r0, (46*8), r46
174 ld.q r0, (47*8), r47
175 ld.q r0, (48*8), r48
176 ld.q r0, (49*8), r49
177 ld.q r0, (50*8), r50
178 ld.q r0, (51*8), r51
179 ld.q r0, (52*8), r52
180 ld.q r0, (53*8), r53
181 ld.q r0, (54*8), r54
182 ld.q r0, (55*8), r55
183 ld.q r0, (56*8), r56
184 ld.q r0, (57*8), r57
185 ld.q r0, (58*8), r58
186 ld.q r0, (59*8), r59
187
188 ! epilogue
189 ld.l r15, 0, r18
190 ld.l r15, 4, r14
191 ptabs r18, tr0
192 movi FRAME_SIZE, r0
193 add r15, r0, r15
194 blink tr0, r63
195__sh64_switch_to_end:
196.LFE1:
197 .size sh64_switch_to,.LFE1-sh64_switch_to
198
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