summaryrefslogtreecommitdiffstats
path: root/arch/arm/kernel/head-common.S
blob: b9505aa267c003a84b2101b1e66af809932f867e (plain) (blame)
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
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
/*
 *  linux/arch/arm/kernel/head-common.S
 *
 *  Copyright (C) 1994-2002 Russell King
 *  Copyright (c) 2003 ARM Limited
 *  All Rights Reserved
 *
 * 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.
 *
 */

#define ATAG_CORE 0x54410001
#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)

	.align	2
	.type	__switch_data, %object
__switch_data:
	.long	__mmap_switched
	.long	__data_loc			@ r4
	.long	_data				@ r5
	.long	__bss_start			@ r6
	.long	_end				@ r7
	.long	processor_id			@ r4
	.long	__machine_arch_type		@ r5
	.long	__atags_pointer			@ r6
	.long	cr_alignment			@ r7
	.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#15 control register
 *  r1  = machine ID
 *  r2  = atags pointer
 *  r9  = processor ID
 */
__mmap_switched:
	adr	r3, __switch_data + 4

	ldmia	r3!, {r4, r5, r6, r7}
	cmp	r4, r5				@ Copy data segment if needed
1:	cmpne	r5, r6
	ldrne	fp, [r4], #4
	strne	fp, [r5], #4
	bne	1b

	mov	fp, #0				@ Clear BSS (and zero fp)
1:	cmp	r6, r7
	strcc	fp, [r6],#4
	bcc	1b

 ARM(	ldmia	r3, {r4, r5, r6, r7, sp})
 THUMB(	ldmia	r3, {r4, r5, r6, r7}	)
 THUMB(	ldr	sp, [r3, #16]		)
	str	r9, [r4]			@ Save processor ID
	str	r1, [r5]			@ Save machine type
	str	r2, [r6]			@ Save atags pointer
	bic	r4, r0, #CR_A			@ Clear 'A' bit
	stmia	r7, {r0, r4}			@ 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
	bl	printascii
	mov	r0, r9
	bl	printhex8
	adr	r0, str_p2
	bl	printascii
	b	__error
str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant (0x"
str_p2:	.asciz	").\n"
	.align
#endif
ENDPROC(__error_p)

__error_a:
#ifdef CONFIG_DEBUG_LL
	mov	r4, r1				@ preserve machine ID
	adr	r0, str_a1
	bl	printascii
	mov	r0, r4
	bl	printhex8
	adr	r0, str_a2
	bl	printascii
	adr	r3, 4f
	ldmia	r3, {r4, r5, r6}		@ get machine desc list
	sub	r4, r3, r4			@ get offset between virt&phys
	add	r5, r5, r4			@ convert virt addresses to
	add	r6, r6, r4			@ physical address space
1:	ldr	r0, [r5, #MACHINFO_TYPE]	@ get machine type
	bl	printhex8
	mov	r0, #'\t'
	bl	printch
	ldr     r0, [r5, #MACHINFO_NAME]	@ get machine name
	add	r0, r0, r4
	bl	printascii
	mov	r0, #'\n'
	bl	printch
	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
	cmp	r5, r6
	blo	1b
	adr	r0, str_a3
	bl	printascii
	b	__error
ENDPROC(__error_a)

str_a1:	.asciz	"\nError: unrecognized/unsupported machine ID (r1 = 0x"
str_a2:	.asciz	").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
str_a3:	.asciz	"\nPlease check your kernel config and/or bootloader.\n"
	.align
#endif

__error:
#ifdef CONFIG_ARCH_RPC
/*
 * Turn the screen red on a error - RiscPC only.
 */
	mov	r0, #0x02000000
	mov	r3, #0x11
	orr	r3, r3, r3, lsl #8
	orr	r3, r3, r3, lsl #16
	str	r3, [r0], #4
	str	r3, [r0], #4
	str	r3, [r0], #4
	str	r3, [r0], #4
#endif
1:	mov	r0, r0
	b	1b
ENDPROC(__error)


/*
 * Read processor ID register (CP#15, CR0), and look up in the linker-built
 * supported processor list.  Note that we can't use the absolute addresses
 * for the __proc_info lists since we aren't running with the MMU on
 * (and therefore, we are not in the correct address space).  We have to
 * calculate the offset.
 *
 *	r9 = cpuid
 * Returns:
 *	r3, r4, r6 corrupted
 *	r5 = proc_info pointer in physical address space
 *	r9 = cpuid (preserved)
 */
__lookup_processor_type:
	adr	r3, 3f
	ldmia	r3, {r5 - r7}
	add	r3, r3, #8
	sub	r3, r3, r7			@ get offset between virt&phys
	add	r5, r5, r3			@ convert virt addresses to
	add	r6, r6, r3			@ physical address space
1:	ldmia	r5, {r3, r4}			@ value, mask
	and	r4, r4, r9			@ mask wanted bits
	teq	r3, r4
	beq	2f
	add	r5, r5, #PROC_INFO_SZ		@ sizeof(proc_info_list)
	cmp	r5, r6
	blo	1b
	mov	r5, #0				@ unknown processor
2:	mov	pc, lr
ENDPROC(__lookup_processor_type)

/*
 * This provides a C-API version of the above function.
 */
ENTRY(lookup_processor_type)
	stmfd	sp!, {r4 - r7, r9, lr}
	mov	r9, r0
	bl	__lookup_processor_type
	mov	r0, r5
	ldmfd	sp!, {r4 - r7, r9, pc}
ENDPROC(lookup_processor_type)

/*
 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for
 * more information about the __proc_info and __arch_info structures.
 */
	.align	2
3:	.long	__proc_info_begin
	.long	__proc_info_end
4:	.long	.
	.long	__arch_info_begin
	.long	__arch_info_end

/*
 * Lookup machine architecture in the linker-build list of architectures.
 * Note that we can't use the absolute addresses for the __arch_info
 * lists since we aren't running with the MMU on (and therefore, we are
 * not in the correct address space).  We have to calculate the offset.
 *
 *  r1 = machine architecture number
 * Returns:
 *  r3, r4, r6 corrupted
 *  r5 = mach_info pointer in physical address space
 */
__lookup_machine_type:
	adr	r3, 4b
	ldmia	r3, {r4, r5, r6}
	sub	r3, r3, r4			@ get offset between virt&phys
	add	r5, r5, r3			@ convert virt addresses to
	add	r6, r6, r3			@ physical address space
1:	ldr	r3, [r5, #MACHINFO_TYPE]	@ get machine type
	teq	r3, r1				@ matches loader number?
	beq	2f				@ found
	add	r5, r5, #SIZEOF_MACHINE_DESC	@ next machine_desc
	cmp	r5, r6
	blo	1b
	mov	r5, #0				@ unknown machine
2:	mov	pc, lr
ENDPROC(__lookup_machine_type)

/*
 * This provides a C-API version of the above function.
 */
ENTRY(lookup_machine_type)
	stmfd	sp!, {r4 - r6, lr}
	mov	r1, r0
	bl	__lookup_machine_type
	mov	r0, r5
	ldmfd	sp!, {r4 - r6, pc}
ENDPROC(lookup_machine_type)

/* Determine validity of the r2 atags pointer.  The heuristic requires
 * that the pointer be aligned, in the first 16k of physical RAM and
 * that the ATAG_CORE marker is first and present.  Future revisions
 * of this function may be more lenient with the physical address and
 * may also be able to move the ATAGS block if necessary.
 *
 * r8  = machinfo
 *
 * Returns:
 *  r2 either valid atags pointer, or zero
 *  r5, r6 corrupted
 */
__vet_atags:
	tst	r2, #0x3			@ aligned?
	bne	1f

	ldr	r5, [r2, #0]			@ is first tag ATAG_CORE?
	cmp	r5, #ATAG_CORE_SIZE
	cmpne	r5, #ATAG_CORE_SIZE_EMPTY
	bne	1f
	ldr	r5, [r2, #4]
	ldr	r6, =ATAG_CORE
	cmp	r5, r6
	bne	1f

	mov	pc, lr				@ atag pointer is ok

1:	mov	r2, #0
	mov	pc, lr
ENDPROC(__vet_atags)