1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
|
/*
* linux/arch/unicore32/kernel/head.S
*
* Code specific to PKUnity SoC and UniCore ISA
*
* Copyright (C) 2001-2010 GUAN Xue-tao
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <linux/init.h>
#include <asm/assembler.h>
#include <asm/ptrace.h>
#include <generated/asm-offsets.h>
#include <asm/memory.h>
#include <asm/thread_info.h>
#include <asm/system.h>
#include <asm/pgtable-hwdef.h>
#if (PHYS_OFFSET & 0x003fffff)
#error "PHYS_OFFSET must be at an even 4MiB boundary!"
#endif
#define KERNEL_RAM_VADDR (PAGE_OFFSET + KERNEL_IMAGE_START)
#define KERNEL_RAM_PADDR (PHYS_OFFSET + KERNEL_IMAGE_START)
#define KERNEL_PGD_PADDR (KERNEL_RAM_PADDR - 0x1000)
#define KERNEL_PGD_VADDR (KERNEL_RAM_VADDR - 0x1000)
#define KERNEL_START KERNEL_RAM_VADDR
#define KERNEL_END _end
/*
* swapper_pg_dir is the virtual address of the initial page table.
* We place the page tables 4K below KERNEL_RAM_VADDR. Therefore, we must
* make sure that KERNEL_RAM_VADDR is correctly set. Currently, we expect
* the least significant 16 bits to be 0x8000, but we could probably
* relax this restriction to KERNEL_RAM_VADDR >= PAGE_OFFSET + 0x1000.
*/
#if (KERNEL_RAM_VADDR & 0xffff) != 0x8000
#error KERNEL_RAM_VADDR must start at 0xXXXX8000
#endif
.globl swapper_pg_dir
.equ swapper_pg_dir, KERNEL_RAM_VADDR - 0x1000
/*
* Kernel startup entry point.
* ---------------------------
*
* This is normally called from the decompressor code. The requirements
* are: MMU = off, D-cache = off, I-cache = dont care
*
* This code is mostly position independent, so if you link the kernel at
* 0xc0008000, you call this at __pa(0xc0008000).
*/
__HEAD
ENTRY(stext)
@ set asr
mov r0, #PRIV_MODE @ ensure priv mode
or r0, #PSR_R_BIT | PSR_I_BIT @ disable irqs
mov.a asr, r0
@ process identify
movc r0, p0.c0, #0 @ cpuid
movl r1, 0xff00ffff @ mask
movl r2, 0x4d000863 @ value
and r0, r1, r0
cxor.a r0, r2
bne __error_p @ invalid processor id
/*
* Clear the 4K level 1 swapper page table
*/
movl r0, #KERNEL_PGD_PADDR @ page table address
mov r1, #0
add r2, r0, #0x1000
101: stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
stw.w r1, [r0]+, #4
cxor.a r0, r2
bne 101b
movl r4, #KERNEL_PGD_PADDR @ page table address
mov r7, #PMD_TYPE_SECT | PMD_PRESENT @ page size: section
or r7, r7, #PMD_SECT_CACHEABLE @ cacheable
or r7, r7, #PMD_SECT_READ | PMD_SECT_WRITE | PMD_SECT_EXEC
/*
* Create identity mapping for first 4MB of kernel to
* cater for the MMU enable. This identity mapping
* will be removed by paging_init(). We use our current program
* counter to determine corresponding section base address.
*/
mov r6, pc
mov r6, r6 >> #22 @ start of kernel section
or r1, r7, r6 << #22 @ flags + kernel base
stw r1, [r4+], r6 << #2 @ identity mapping
/*
* Now setup the pagetables for our kernel direct
* mapped region.
*/
add r0, r4, #(KERNEL_START & 0xff000000) >> 20
stw.w r1, [r0+], #(KERNEL_START & 0x00c00000) >> 20
movl r6, #(KERNEL_END - 1)
add r0, r0, #4
add r6, r4, r6 >> #20
102: csub.a r0, r6
add r1, r1, #1 << 22
bua 103f
stw.w r1, [r0]+, #4
b 102b
103:
/*
* Then map first 4MB of ram in case it contains our boot params.
*/
add r0, r4, #PAGE_OFFSET >> 20
or r6, r7, #(PHYS_OFFSET & 0xffc00000)
stw r6, [r0]
ldw r15, __switch_data @ address to jump to after
/*
* Initialise TLB, Caches, and MMU state ready to switch the MMU
* on.
*/
mov r0, #0
movc p0.c5, r0, #28 @ cache invalidate all
nop8
movc p0.c6, r0, #6 @ TLB invalidate all
nop8
/*
* ..V. .... ..TB IDAM
* ..1. .... ..01 1111
*/
movl r0, #0x201f @ control register setting
/*
* Setup common bits before finally enabling the MMU. Essentially
* this is just loading the page table pointer and domain access
* registers.
*/
#ifndef CONFIG_ALIGNMENT_TRAP
andn r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
andn r0, r0, #CR_D
#endif
#ifdef CONFIG_CPU_DCACHE_WRITETHROUGH
andn r0, r0, #CR_B
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
andn r0, r0, #CR_I
#endif
movc p0.c2, r4, #0 @ set pgd
b __turn_mmu_on
ENDPROC(stext)
/*
* Enable the MMU. This completely changes the stucture of the visible
* memory space. You will not be able to trace execution through this.
*
* r0 = cp#0 control register
* r15 = *virtual* address to jump to upon completion
*/
.align 5
__turn_mmu_on:
mov r0, r0
movc p0.c1, r0, #0 @ write control reg
nop @ fetch inst by phys addr
mov pc, r15
nop8 @ fetch inst by phys addr
ENDPROC(__turn_mmu_on)
/*
* Setup the initial page tables. We only setup the barest
* amount which are required to get the kernel running, which
* generally means mapping in the kernel code.
*
* r9 = cpuid
* r10 = procinfo
*
* Returns:
* r0, r3, r6, r7 corrupted
* r4 = physical page table address
*/
.ltorg
.align 2
.type __switch_data, %object
__switch_data:
.long __mmap_switched
.long __bss_start @ r6
.long _end @ r7
.long cr_alignment @ r8
.long init_thread_union + THREAD_START_SP @ sp
/*
* The following fragment of code is executed with the MMU on in MMU mode,
* and uses absolute addresses; this is not position independent.
*
* r0 = cp#0 control register
*/
__mmap_switched:
adr r3, __switch_data + 4
ldm.w (r6, r7, r8), [r3]+
ldw sp, [r3]
mov fp, #0 @ Clear BSS (and zero fp)
203: csub.a r6, r7
bea 204f
stw.w fp, [r6]+,#4
b 203b
204:
andn r1, r0, #CR_A @ Clear 'A' bit
stm (r0, r1), [r8]+ @ Save control register values
b start_kernel
ENDPROC(__mmap_switched)
/*
* Exception handling. Something went wrong and we can't proceed. We
* ought to tell the user, but since we don't have any guarantee that
* we're even running on the right architecture, we do virtually nothing.
*
* If CONFIG_DEBUG_LL is set we try to print out something about the error
* and hope for the best (useful if bootloader fails to pass a proper
* machine ID for example).
*/
__error_p:
#ifdef CONFIG_DEBUG_LL
adr r0, str_p1
b.l printascii
mov r0, r9
b.l printhex8
adr r0, str_p2
b.l printascii
901: nop8
b 901b
str_p1: .asciz "\nError: unrecognized processor variant (0x"
str_p2: .asciz ").\n"
.align
#endif
ENDPROC(__error_p)
|
