aboutsummaryrefslogtreecommitdiffstats
path: root/arch/arm/kernel/head.S
blob: 1aca1775b28f188ac6682e5dfd15cd54e05b414e (plain)
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
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
/*
 *  linux/arch/arm/kernel/head.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.
 *
 *  Kernel startup code for all 32-bit CPUs
 */
#include <linux/config.h>
#include <linux/linkage.h>
#include <linux/init.h>

#include <asm/assembler.h>
#include <asm/domain.h>
#include <asm/procinfo.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>
#include <asm/memory.h>
#include <asm/thread_info.h>
#include <asm/system.h>

#define PROCINFO_MMUFLAGS	8
#define PROCINFO_INITFUNC	12

#define MACHINFO_TYPE		0
#define MACHINFO_PHYSRAM	4
#define MACHINFO_PHYSIO		8
#define MACHINFO_PGOFFIO	12
#define MACHINFO_NAME		16

#define KERNEL_RAM_ADDR	(PAGE_OFFSET + TEXT_OFFSET)

/*
 * swapper_pg_dir is the virtual address of the initial page table.
 * We place the page tables 16K below KERNEL_RAM_ADDR.  Therefore, we must
 * make sure that KERNEL_RAM_ADDR is correctly set.  Currently, we expect
 * the least significant 16 bits to be 0x8000, but we could probably
 * relax this restriction to KERNEL_RAM_ADDR >= PAGE_OFFSET + 0x4000.
 */
#if (KERNEL_RAM_ADDR & 0xffff) != 0x8000
#error KERNEL_RAM_ADDR must start at 0xXXXX8000
#endif

	.globl	swapper_pg_dir
	.equ	swapper_pg_dir, KERNEL_RAM_ADDR - 0x4000

	.macro	pgtbl, rd
	ldr	\rd, =(__virt_to_phys(KERNEL_RAM_ADDR - 0x4000))
	.endm

#ifdef CONFIG_XIP_KERNEL
#define TEXTADDR  XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
#else
#define TEXTADDR  KERNEL_RAM_ADDR
#endif

/*
 * Kernel startup entry point.
 * ---------------------------
 *
 * This is normally called from the decompressor code.  The requirements
 * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
 * r1 = machine nr.
 *
 * This code is mostly position independent, so if you link the kernel at
 * 0xc0008000, you call this at __pa(0xc0008000).
 *
 * See linux/arch/arm/tools/mach-types for the complete list of machine
 * numbers for r1.
 *
 * We're trying to keep crap to a minimum; DO NOT add any machine specific
 * crap here - that's what the boot loader (or in extreme, well justified
 * circumstances, zImage) is for.
 */
	__INIT
	.type	stext, %function
ENTRY(stext)
	msr	cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC @ ensure svc mode
						@ and irqs disabled
	bl	__lookup_processor_type		@ r5=procinfo r9=cpuid
	movs	r10, r5				@ invalid processor (r5=0)?
	beq	__error_p			@ yes, error 'p'
	bl	__lookup_machine_type		@ r5=machinfo
	movs	r8, r5				@ invalid machine (r5=0)?
	beq	__error_a			@ yes, error 'a'
	bl	__create_page_tables

	/*
	 * The following calls CPU specific code in a position independent
	 * manner.  See arch/arm/mm/proc-*.S for details.  r10 = base of
	 * xxx_proc_info structure selected by __lookup_machine_type
	 * above.  On return, the CPU will be ready for the MMU to be
	 * turned on, and r0 will hold the CPU control register value.
	 */
	ldr	r13, __switch_data		@ address to jump to after
						@ mmu has been enabled
	adr	lr, __enable_mmu		@ return (PIC) address
	add	pc, r10, #PROCINFO_INITFUNC

	.type	__switch_data, %object
__switch_data:
	.long	__mmap_switched
	.long	__data_loc			@ r4
	.long	__data_start			@ r5
	.long	__bss_start			@ r6
	.long	_end				@ r7
	.long	processor_id			@ r4
	.long	__machine_arch_type		@ r5
	.long	cr_alignment			@ r6
	.long	init_thread_union + THREAD_START_SP @ sp

/*
 * The following fragment of code is executed with the MMU on, and uses
 * absolute addresses; this is not position independent.
 *
 *  r0  = cp#15 control register
 *  r1  = machine ID
 *  r9  = processor ID
 */
	.type	__mmap_switched, %function
__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

	ldmia	r3, {r4, r5, r6, sp}
	str	r9, [r4]			@ Save processor ID
	str	r1, [r5]			@ Save machine type
	bic	r4, r0, #CR_A			@ Clear 'A' bit
	stmia	r6, {r0, r4}			@ Save control register values
	b	start_kernel

#if defined(CONFIG_SMP)
	.type   secondary_startup, #function
ENTRY(secondary_startup)
	/*
	 * Common entry point for secondary CPUs.
	 *
	 * Ensure that we're in SVC mode, and IRQs are disabled.  Lookup
	 * the processor type - there is no need to check the machine type
	 * as it has already been validated by the primary processor.
	 */
	msr	cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC
	bl	__lookup_processor_type
	movs	r10, r5				@ invalid processor?
	moveq	r0, #'p'			@ yes, error 'p'
	beq	__error

	/*
	 * Use the page tables supplied from  __cpu_up.
	 */
	adr	r4, __secondary_data
	ldmia	r4, {r5, r6, r13}		@ address to jump to after
	sub	r4, r4, r5			@ mmu has been enabled
	ldr	r4, [r6, r4]			@ get secondary_data.pgdir
	adr	lr, __enable_mmu		@ return address
	add	pc, r10, #12			@ initialise processor
						@ (return control reg)

	/*
	 * r6  = &secondary_data
	 */
ENTRY(__secondary_switched)
	ldr	sp, [r6, #4]			@ get secondary_data.stack
	mov	fp, #0
	b	secondary_start_kernel

	.type	__secondary_data, %object
__secondary_data:
	.long	.
	.long	secondary_data
	.long	__secondary_switched
#endif /* defined(CONFIG_SMP) */



/*
 * Setup common bits before finally enabling the MMU.  Essentially
 * this is just loading the page table pointer and domain access
 * registers.
 */
	.type	__enable_mmu, %function
__enable_mmu:
#ifdef CONFIG_ALIGNMENT_TRAP
	orr	r0, r0, #CR_A
#else
	bic	r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
	bic	r0, r0, #CR_C
#endif
#ifdef CONFIG_CPU_BPREDICT_DISABLE
	bic	r0, r0, #CR_Z
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
	bic	r0, r0, #CR_I
#endif
	mov	r5, #(domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
		      domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
		      domain_val(DOMAIN_TABLE, DOMAIN_MANAGER) | \
		      domain_val(DOMAIN_IO, DOMAIN_CLIENT))
	mcr	p15, 0, r5, c3, c0, 0		@ load domain access register
	mcr	p15, 0, r4, c2, c0, 0		@ load page table pointer
	b	__turn_mmu_on

/*
 * Enable the MMU.  This completely changes the structure of the visible
 * memory space.  You will not be able to trace execution through this.
 * If you have an enquiry about this, *please* check the linux-arm-kernel
 * mailing list archives BEFORE sending another post to the list.
 *
 *  r0  = cp#15 control register
 *  r13 = *virtual* address to jump to upon completion
 *
 * other registers depend on the function called upon completion
 */
	.align	5
	.type	__turn_mmu_on, %function
__turn_mmu_on:
	mov	r0, r0
	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
	mrc	p15, 0, r3, c0, c0, 0		@ read id reg
	mov	r3, r3
	mov	r3, r3
	mov	pc, r13



/*
 * 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.
 *
 * r8  = machinfo
 * r9  = cpuid
 * r10 = procinfo
 *
 * Returns:
 *  r0, r3, r6, r7 corrupted
 *  r4 = physical page table address
 */
	.type	__create_page_tables, %function
__create_page_tables:
	pgtbl	r4				@ page table address

	/*
	 * Clear the 16K level 1 swapper page table
	 */
	mov	r0, r4
	mov	r3, #0
	add	r6, r0, #0x4000
1:	str	r3, [r0], #4
	str	r3, [r0], #4
	str	r3, [r0], #4
	str	r3, [r0], #4
	teq	r0, r6
	bne	1b

	ldr	r7, [r10, #PROCINFO_MMUFLAGS]	@ mmuflags

	/*
	 * Create identity mapping for first MB 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, lsr #20			@ start of kernel section
	orr	r3, r7, r6, lsl #20		@ flags + kernel base
	str	r3, [r4, r6, lsl #2]		@ identity mapping

	/*
	 * Now setup the pagetables for our kernel direct
	 * mapped region.  We round TEXTADDR down to the
	 * nearest megabyte boundary.  It is assumed that
	 * the kernel fits within 4 contigous 1MB sections.
	 */
	add	r0, r4,  #(TEXTADDR & 0xff000000) >> 18	@ start of kernel
	str	r3, [r0, #(TEXTADDR & 0x00f00000) >> 18]!
	add	r3, r3, #1 << 20
	str	r3, [r0, #4]!			@ KERNEL + 1MB
	add	r3, r3, #1 << 20
	str	r3, [r0, #4]!			@ KERNEL + 2MB
	add	r3, r3, #1 << 20
	str	r3, [r0, #4]			@ KERNEL + 3MB

	/*
	 * Then map first 1MB of ram in case it contains our boot params.
	 */
	add	r0, r4, #PAGE_OFFSET >> 18
	orr	r6, r7, #PHYS_OFFSET
	str	r6, [r0]

#ifdef CONFIG_XIP_KERNEL
	/*
	 * Map some ram to cover our .data and .bss areas.
	 * Mapping 3MB should be plenty.
	 */
	sub	r3, r4, #PHYS_OFFSET
	mov	r3, r3, lsr #20
	add	r0, r0, r3, lsl #2
	add	r6, r6, r3, lsl #20
	str	r6, [r0], #4
	add	r6, r6, #(1 << 20)
	str	r6, [r0], #4
	add	r6, r6, #(1 << 20)
	str	r6, [r0]
#endif

#ifdef CONFIG_DEBUG_LL
	bic	r7, r7, #0x0c			@ turn off cacheable
						@ and bufferable bits
	/*
	 * Map in IO space for serial debugging.
	 * This allows debug messages to be output
	 * via a serial console before paging_init.
	 */
	ldr	r3, [r8, #MACHINFO_PGOFFIO]
	add	r0, r4, r3
	rsb	r3, r3, #0x4000			@ PTRS_PER_PGD*sizeof(long)
	cmp	r3, #0x0800			@ limit to 512MB
	movhi	r3, #0x0800
	add	r6, r0, r3
	ldr	r3, [r8, #MACHINFO_PHYSIO]
	orr	r3, r3, r7
1:	str	r3, [r0], #4
	add	r3, r3, #1 << 20
	teq	r0, r6
	bne	1b
#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
	/*
	 * If we're using the NetWinder or CATS, we also need to map
	 * in the 16550-type serial port for the debug messages
	 */
	add	r0, r4, #0xff000000 >> 18
	orr	r3, r7, #0x7c000000
	str	r3, [r0]
#endif
#ifdef CONFIG_ARCH_RPC
	/*
	 * Map in screen at 0x02000000 & SCREEN2_BASE
	 * Similar reasons here - for debug.  This is
	 * only for Acorn RiscPC architectures.
	 */
	add	r0, r4, #0x02000000 >> 18
	orr	r3, r7, #0x02000000
	str	r3, [r0]
	add	r0, r4, #0xd8000000 >> 18
	str	r3, [r0]
#endif
#endif
	mov	pc, lr
	.ltorg



/*
 * 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).
 */

	.type	__error_p, %function
__error_p:
#ifdef CONFIG_DEBUG_LL
	adr	r0, str_p1
	bl	printascii
	b	__error
str_p1:	.asciz	"\nError: unrecognized/unsupported processor variant.\n"
	.align
#endif

	.type	__error_a, %function
__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, 3f
	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
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

	.type	__error, %function
__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


/*
 * 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.
 *
 * Returns:
 *	r3, r4, r6 corrupted
 *	r5 = proc_info pointer in physical address space
 *	r9 = cpuid
 */
	.type	__lookup_processor_type, %function
__lookup_processor_type:
	adr	r3, 3f
	ldmda	r3, {r5, r6, r9}
	sub	r3, r3, r9			@ get offset between virt&phys
	add	r5, r5, r3			@ convert virt addresses to
	add	r6, r6, r3			@ physical address space
	mrc	p15, 0, r9, c0, c0		@ get processor id
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

/*
 * This provides a C-API version of the above function.
 */
ENTRY(lookup_processor_type)
	stmfd	sp!, {r4 - r6, r9, lr}
	bl	__lookup_processor_type
	mov	r0, r5
	ldmfd	sp!, {r4 - r6, r9, pc}

/*
 * Look in include/asm-arm/procinfo.h and arch/arm/kernel/arch.[ch] for
 * more information about the __proc_info and __arch_info structures.
 */
	.long	__proc_info_begin
	.long	__proc_info_end
3:	.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
 */
	.type	__lookup_machine_type, %function
__lookup_machine_type:
	adr	r3, 3b
	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

/*
 * 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}