xref: /openbmc/linux/arch/arm/kernel/head.S (revision 0ad53fe3) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/kernel/head.S
4 *
5 *  Copyright (C) 1994-2002 Russell King
6 *  Copyright (c) 2003 ARM Limited
7 *  All Rights Reserved
8 *
9 *  Kernel startup code for all 32-bit CPUs
10 */
11#include <linux/linkage.h>
12#include <linux/init.h>
13#include <linux/pgtable.h>
14
15#include <asm/assembler.h>
16#include <asm/cp15.h>
17#include <asm/domain.h>
18#include <asm/ptrace.h>
19#include <asm/asm-offsets.h>
20#include <asm/memory.h>
21#include <asm/thread_info.h>
22
23#if defined(CONFIG_DEBUG_LL) && !defined(CONFIG_DEBUG_SEMIHOSTING)
24#include CONFIG_DEBUG_LL_INCLUDE
25#endif
26/*
27 * swapper_pg_dir is the virtual address of the initial page table.
28 * We place the page tables 16K below KERNEL_RAM_VADDR.  Therefore, we must
29 * make sure that KERNEL_RAM_VADDR is correctly set.  Currently, we expect
30 * the least significant 16 bits to be 0x8000, but we could probably
31 * relax this restriction to KERNEL_RAM_VADDR >= PAGE_OFFSET + 0x4000.
32 */
33#define KERNEL_RAM_VADDR	(KERNEL_OFFSET + TEXT_OFFSET)
34#if (KERNEL_RAM_VADDR & 0xffff) != 0x8000
35#error KERNEL_RAM_VADDR must start at 0xXXXX8000
36#endif
37
38#ifdef CONFIG_ARM_LPAE
39	/* LPAE requires an additional page for the PGD */
40#define PG_DIR_SIZE	0x5000
41#define PMD_ORDER	3
42#else
43#define PG_DIR_SIZE	0x4000
44#define PMD_ORDER	2
45#endif
46
47	.globl	swapper_pg_dir
48	.equ	swapper_pg_dir, KERNEL_RAM_VADDR - PG_DIR_SIZE
49
50	/*
51	 * This needs to be assigned at runtime when the linker symbols are
52	 * resolved. These are unsigned 64bit really, but in this assembly code
53	 * We store them as 32bit.
54	 */
55	.pushsection .data
56	.align	2
57	.globl	kernel_sec_start
58	.globl	kernel_sec_end
59kernel_sec_start:
60	.long	0
61	.long	0
62kernel_sec_end:
63	.long	0
64	.long	0
65	.popsection
66
67	.macro	pgtbl, rd, phys
68	add	\rd, \phys, #TEXT_OFFSET
69	sub	\rd, \rd, #PG_DIR_SIZE
70	.endm
71
72/*
73 * Kernel startup entry point.
74 * ---------------------------
75 *
76 * This is normally called from the decompressor code.  The requirements
77 * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
78 * r1 = machine nr, r2 = atags or dtb pointer.
79 *
80 * This code is mostly position independent, so if you link the kernel at
81 * 0xc0008000, you call this at __pa(0xc0008000).
82 *
83 * See linux/arch/arm/tools/mach-types for the complete list of machine
84 * numbers for r1.
85 *
86 * We're trying to keep crap to a minimum; DO NOT add any machine specific
87 * crap here - that's what the boot loader (or in extreme, well justified
88 * circumstances, zImage) is for.
89 */
90	.arm
91
92	__HEAD
93ENTRY(stext)
94 ARM_BE8(setend	be )			@ ensure we are in BE8 mode
95
96 THUMB(	badr	r9, 1f		)	@ Kernel is always entered in ARM.
97 THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
98 THUMB(	.thumb			)	@ switch to Thumb now.
99 THUMB(1:			)
100
101#ifdef CONFIG_ARM_VIRT_EXT
102	bl	__hyp_stub_install
103#endif
104	@ ensure svc mode and all interrupts masked
105	safe_svcmode_maskall r9
106
107	mrc	p15, 0, r9, c0, c0		@ get processor id
108	bl	__lookup_processor_type		@ r5=procinfo r9=cpuid
109	movs	r10, r5				@ invalid processor (r5=0)?
110 THUMB( it	eq )		@ force fixup-able long branch encoding
111	beq	__error_p			@ yes, error 'p'
112
113#ifdef CONFIG_ARM_LPAE
114	mrc	p15, 0, r3, c0, c1, 4		@ read ID_MMFR0
115	and	r3, r3, #0xf			@ extract VMSA support
116	cmp	r3, #5				@ long-descriptor translation table format?
117 THUMB( it	lo )				@ force fixup-able long branch encoding
118	blo	__error_lpae			@ only classic page table format
119#endif
120
121#ifndef CONFIG_XIP_KERNEL
122	adr_l	r8, _text			@ __pa(_text)
123	sub	r8, r8, #TEXT_OFFSET		@ PHYS_OFFSET
124#else
125	ldr	r8, =PLAT_PHYS_OFFSET		@ always constant in this case
126#endif
127
128	/*
129	 * r1 = machine no, r2 = atags or dtb,
130	 * r8 = phys_offset, r9 = cpuid, r10 = procinfo
131	 */
132	bl	__vet_atags
133#ifdef CONFIG_SMP_ON_UP
134	bl	__fixup_smp
135#endif
136#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
137	bl	__fixup_pv_table
138#endif
139	bl	__create_page_tables
140
141	/*
142	 * The following calls CPU specific code in a position independent
143	 * manner.  See arch/arm/mm/proc-*.S for details.  r10 = base of
144	 * xxx_proc_info structure selected by __lookup_processor_type
145	 * above.
146	 *
147	 * The processor init function will be called with:
148	 *  r1 - machine type
149	 *  r2 - boot data (atags/dt) pointer
150	 *  r4 - translation table base (low word)
151	 *  r5 - translation table base (high word, if LPAE)
152	 *  r8 - translation table base 1 (pfn if LPAE)
153	 *  r9 - cpuid
154	 *  r13 - virtual address for __enable_mmu -> __turn_mmu_on
155	 *
156	 * On return, the CPU will be ready for the MMU to be turned on,
157	 * r0 will hold the CPU control register value, r1, r2, r4, and
158	 * r9 will be preserved.  r5 will also be preserved if LPAE.
159	 */
160	ldr	r13, =__mmap_switched		@ address to jump to after
161						@ mmu has been enabled
162	badr	lr, 1f				@ return (PIC) address
163#ifdef CONFIG_ARM_LPAE
164	mov	r5, #0				@ high TTBR0
165	mov	r8, r4, lsr #12			@ TTBR1 is swapper_pg_dir pfn
166#else
167	mov	r8, r4				@ set TTBR1 to swapper_pg_dir
168#endif
169	ldr	r12, [r10, #PROCINFO_INITFUNC]
170	add	r12, r12, r10
171	ret	r12
1721:	b	__enable_mmu
173ENDPROC(stext)
174	.ltorg
175
176/*
177 * Setup the initial page tables.  We only setup the barest
178 * amount which are required to get the kernel running, which
179 * generally means mapping in the kernel code.
180 *
181 * r8 = phys_offset, r9 = cpuid, r10 = procinfo
182 *
183 * Returns:
184 *  r0, r3, r5-r7 corrupted
185 *  r4 = physical page table address
186 */
187__create_page_tables:
188	pgtbl	r4, r8				@ page table address
189
190	/*
191	 * Clear the swapper page table
192	 */
193	mov	r0, r4
194	mov	r3, #0
195	add	r6, r0, #PG_DIR_SIZE
1961:	str	r3, [r0], #4
197	str	r3, [r0], #4
198	str	r3, [r0], #4
199	str	r3, [r0], #4
200	teq	r0, r6
201	bne	1b
202
203#ifdef CONFIG_ARM_LPAE
204	/*
205	 * Build the PGD table (first level) to point to the PMD table. A PGD
206	 * entry is 64-bit wide.
207	 */
208	mov	r0, r4
209	add	r3, r4, #0x1000			@ first PMD table address
210	orr	r3, r3, #3			@ PGD block type
211	mov	r6, #4				@ PTRS_PER_PGD
212	mov	r7, #1 << (55 - 32)		@ L_PGD_SWAPPER
2131:
214#ifdef CONFIG_CPU_ENDIAN_BE8
215	str	r7, [r0], #4			@ set top PGD entry bits
216	str	r3, [r0], #4			@ set bottom PGD entry bits
217#else
218	str	r3, [r0], #4			@ set bottom PGD entry bits
219	str	r7, [r0], #4			@ set top PGD entry bits
220#endif
221	add	r3, r3, #0x1000			@ next PMD table
222	subs	r6, r6, #1
223	bne	1b
224
225	add	r4, r4, #0x1000			@ point to the PMD tables
226#ifdef CONFIG_CPU_ENDIAN_BE8
227	add	r4, r4, #4			@ we only write the bottom word
228#endif
229#endif
230
231	ldr	r7, [r10, #PROCINFO_MM_MMUFLAGS] @ mm_mmuflags
232
233	/*
234	 * Create identity mapping to cater for __enable_mmu.
235	 * This identity mapping will be removed by paging_init().
236	 */
237	adr_l	r5, __turn_mmu_on		@ _pa(__turn_mmu_on)
238	adr_l	r6, __turn_mmu_on_end		@ _pa(__turn_mmu_on_end)
239	mov	r5, r5, lsr #SECTION_SHIFT
240	mov	r6, r6, lsr #SECTION_SHIFT
241
2421:	orr	r3, r7, r5, lsl #SECTION_SHIFT	@ flags + kernel base
243	str	r3, [r4, r5, lsl #PMD_ORDER]	@ identity mapping
244	cmp	r5, r6
245	addlo	r5, r5, #1			@ next section
246	blo	1b
247
248	/*
249	 * The main matter: map in the kernel using section mappings, and
250	 * set two variables to indicate the physical start and end of the
251	 * kernel.
252	 */
253	add	r0, r4, #KERNEL_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
254	ldr	r6, =(_end - 1)
255	adr_l	r5, kernel_sec_start		@ _pa(kernel_sec_start)
256#ifdef CONFIG_CPU_ENDIAN_BE8
257	str	r8, [r5, #4]			@ Save physical start of kernel (BE)
258#else
259	str	r8, [r5]			@ Save physical start of kernel (LE)
260#endif
261	orr	r3, r8, r7			@ Add the MMU flags
262	add	r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
2631:	str	r3, [r0], #1 << PMD_ORDER
264	add	r3, r3, #1 << SECTION_SHIFT
265	cmp	r0, r6
266	bls	1b
267	eor	r3, r3, r7			@ Remove the MMU flags
268	adr_l	r5, kernel_sec_end		@ _pa(kernel_sec_end)
269#ifdef CONFIG_CPU_ENDIAN_BE8
270	str	r3, [r5, #4]			@ Save physical end of kernel (BE)
271#else
272	str	r3, [r5]			@ Save physical end of kernel (LE)
273#endif
274
275#ifdef CONFIG_XIP_KERNEL
276	/*
277	 * Map the kernel image separately as it is not located in RAM.
278	 */
279#define XIP_START XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
280	mov	r3, pc
281	mov	r3, r3, lsr #SECTION_SHIFT
282	orr	r3, r7, r3, lsl #SECTION_SHIFT
283	add	r0, r4,  #(XIP_START & 0xff000000) >> (SECTION_SHIFT - PMD_ORDER)
284	str	r3, [r0, #((XIP_START & 0x00f00000) >> SECTION_SHIFT) << PMD_ORDER]!
285	ldr	r6, =(_edata_loc - 1)
286	add	r0, r0, #1 << PMD_ORDER
287	add	r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
2881:	cmp	r0, r6
289	add	r3, r3, #1 << SECTION_SHIFT
290	strls	r3, [r0], #1 << PMD_ORDER
291	bls	1b
292#endif
293
294	/*
295	 * Then map boot params address in r2 if specified.
296	 * We map 2 sections in case the ATAGs/DTB crosses a section boundary.
297	 */
298	mov	r0, r2, lsr #SECTION_SHIFT
299	cmp	r2, #0
300	ldrne	r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER)
301	addne	r3, r3, r4
302	orrne	r6, r7, r0, lsl #SECTION_SHIFT
303	strne	r6, [r3], #1 << PMD_ORDER
304	addne	r6, r6, #1 << SECTION_SHIFT
305	strne	r6, [r3]
306
307#if defined(CONFIG_ARM_LPAE) && defined(CONFIG_CPU_ENDIAN_BE8)
308	sub	r4, r4, #4			@ Fixup page table pointer
309						@ for 64-bit descriptors
310#endif
311
312#ifdef CONFIG_DEBUG_LL
313#if !defined(CONFIG_DEBUG_ICEDCC) && !defined(CONFIG_DEBUG_SEMIHOSTING)
314	/*
315	 * Map in IO space for serial debugging.
316	 * This allows debug messages to be output
317	 * via a serial console before paging_init.
318	 */
319	addruart r7, r3, r0
320
321	mov	r3, r3, lsr #SECTION_SHIFT
322	mov	r3, r3, lsl #PMD_ORDER
323
324	add	r0, r4, r3
325	mov	r3, r7, lsr #SECTION_SHIFT
326	ldr	r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
327	orr	r3, r7, r3, lsl #SECTION_SHIFT
328#ifdef CONFIG_ARM_LPAE
329	mov	r7, #1 << (54 - 32)		@ XN
330#ifdef CONFIG_CPU_ENDIAN_BE8
331	str	r7, [r0], #4
332	str	r3, [r0], #4
333#else
334	str	r3, [r0], #4
335	str	r7, [r0], #4
336#endif
337#else
338	orr	r3, r3, #PMD_SECT_XN
339	str	r3, [r0], #4
340#endif
341
342#else /* CONFIG_DEBUG_ICEDCC || CONFIG_DEBUG_SEMIHOSTING */
343	/* we don't need any serial debugging mappings */
344	ldr	r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
345#endif
346
347#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
348	/*
349	 * If we're using the NetWinder or CATS, we also need to map
350	 * in the 16550-type serial port for the debug messages
351	 */
352	add	r0, r4, #0xff000000 >> (SECTION_SHIFT - PMD_ORDER)
353	orr	r3, r7, #0x7c000000
354	str	r3, [r0]
355#endif
356#ifdef CONFIG_ARCH_RPC
357	/*
358	 * Map in screen at 0x02000000 & SCREEN2_BASE
359	 * Similar reasons here - for debug.  This is
360	 * only for Acorn RiscPC architectures.
361	 */
362	add	r0, r4, #0x02000000 >> (SECTION_SHIFT - PMD_ORDER)
363	orr	r3, r7, #0x02000000
364	str	r3, [r0]
365	add	r0, r4, #0xd8000000 >> (SECTION_SHIFT - PMD_ORDER)
366	str	r3, [r0]
367#endif
368#endif
369#ifdef CONFIG_ARM_LPAE
370	sub	r4, r4, #0x1000		@ point to the PGD table
371#endif
372	ret	lr
373ENDPROC(__create_page_tables)
374	.ltorg
375
376#if defined(CONFIG_SMP)
377	.text
378	.arm
379ENTRY(secondary_startup_arm)
380 THUMB(	badr	r9, 1f		)	@ Kernel is entered in ARM.
381 THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
382 THUMB(	.thumb			)	@ switch to Thumb now.
383 THUMB(1:			)
384ENTRY(secondary_startup)
385	/*
386	 * Common entry point for secondary CPUs.
387	 *
388	 * Ensure that we're in SVC mode, and IRQs are disabled.  Lookup
389	 * the processor type - there is no need to check the machine type
390	 * as it has already been validated by the primary processor.
391	 */
392
393 ARM_BE8(setend	be)				@ ensure we are in BE8 mode
394
395#ifdef CONFIG_ARM_VIRT_EXT
396	bl	__hyp_stub_install_secondary
397#endif
398	safe_svcmode_maskall r9
399
400	mrc	p15, 0, r9, c0, c0		@ get processor id
401	bl	__lookup_processor_type
402	movs	r10, r5				@ invalid processor?
403	moveq	r0, #'p'			@ yes, error 'p'
404 THUMB( it	eq )		@ force fixup-able long branch encoding
405	beq	__error_p
406
407	/*
408	 * Use the page tables supplied from  __cpu_up.
409	 */
410	adr_l	r3, secondary_data
411	mov_l	r12, __secondary_switched
412	ldrd	r4, r5, [r3, #0]		@ get secondary_data.pgdir
413ARM_BE8(eor	r4, r4, r5)			@ Swap r5 and r4 in BE:
414ARM_BE8(eor	r5, r4, r5)			@ it can be done in 3 steps
415ARM_BE8(eor	r4, r4, r5)			@ without using a temp reg.
416	ldr	r8, [r3, #8]			@ get secondary_data.swapper_pg_dir
417	badr	lr, __enable_mmu		@ return address
418	mov	r13, r12			@ __secondary_switched address
419	ldr	r12, [r10, #PROCINFO_INITFUNC]
420	add	r12, r12, r10			@ initialise processor
421						@ (return control reg)
422	ret	r12
423ENDPROC(secondary_startup)
424ENDPROC(secondary_startup_arm)
425
426ENTRY(__secondary_switched)
427	ldr_l	r7, secondary_data + 12		@ get secondary_data.stack
428	mov	sp, r7
429	mov	fp, #0
430	b	secondary_start_kernel
431ENDPROC(__secondary_switched)
432
433#endif /* defined(CONFIG_SMP) */
434
435
436
437/*
438 * Setup common bits before finally enabling the MMU.  Essentially
439 * this is just loading the page table pointer and domain access
440 * registers.  All these registers need to be preserved by the
441 * processor setup function (or set in the case of r0)
442 *
443 *  r0  = cp#15 control register
444 *  r1  = machine ID
445 *  r2  = atags or dtb pointer
446 *  r4  = TTBR pointer (low word)
447 *  r5  = TTBR pointer (high word if LPAE)
448 *  r9  = processor ID
449 *  r13 = *virtual* address to jump to upon completion
450 */
451__enable_mmu:
452#if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
453	orr	r0, r0, #CR_A
454#else
455	bic	r0, r0, #CR_A
456#endif
457#ifdef CONFIG_CPU_DCACHE_DISABLE
458	bic	r0, r0, #CR_C
459#endif
460#ifdef CONFIG_CPU_BPREDICT_DISABLE
461	bic	r0, r0, #CR_Z
462#endif
463#ifdef CONFIG_CPU_ICACHE_DISABLE
464	bic	r0, r0, #CR_I
465#endif
466#ifdef CONFIG_ARM_LPAE
467	mcrr	p15, 0, r4, r5, c2		@ load TTBR0
468#else
469	mov	r5, #DACR_INIT
470	mcr	p15, 0, r5, c3, c0, 0		@ load domain access register
471	mcr	p15, 0, r4, c2, c0, 0		@ load page table pointer
472#endif
473	b	__turn_mmu_on
474ENDPROC(__enable_mmu)
475
476/*
477 * Enable the MMU.  This completely changes the structure of the visible
478 * memory space.  You will not be able to trace execution through this.
479 * If you have an enquiry about this, *please* check the linux-arm-kernel
480 * mailing list archives BEFORE sending another post to the list.
481 *
482 *  r0  = cp#15 control register
483 *  r1  = machine ID
484 *  r2  = atags or dtb pointer
485 *  r9  = processor ID
486 *  r13 = *virtual* address to jump to upon completion
487 *
488 * other registers depend on the function called upon completion
489 */
490	.align	5
491	.pushsection	.idmap.text, "ax"
492ENTRY(__turn_mmu_on)
493	mov	r0, r0
494	instr_sync
495	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
496	mrc	p15, 0, r3, c0, c0, 0		@ read id reg
497	instr_sync
498	mov	r3, r3
499	mov	r3, r13
500	ret	r3
501__turn_mmu_on_end:
502ENDPROC(__turn_mmu_on)
503	.popsection
504
505
506#ifdef CONFIG_SMP_ON_UP
507	__HEAD
508__fixup_smp:
509	and	r3, r9, #0x000f0000	@ architecture version
510	teq	r3, #0x000f0000		@ CPU ID supported?
511	bne	__fixup_smp_on_up	@ no, assume UP
512
513	bic	r3, r9, #0x00ff0000
514	bic	r3, r3, #0x0000000f	@ mask 0xff00fff0
515	mov	r4, #0x41000000
516	orr	r4, r4, #0x0000b000
517	orr	r4, r4, #0x00000020	@ val 0x4100b020
518	teq	r3, r4			@ ARM 11MPCore?
519	reteq	lr			@ yes, assume SMP
520
521	mrc	p15, 0, r0, c0, c0, 5	@ read MPIDR
522	and	r0, r0, #0xc0000000	@ multiprocessing extensions and
523	teq	r0, #0x80000000		@ not part of a uniprocessor system?
524	bne    __fixup_smp_on_up	@ no, assume UP
525
526	@ Core indicates it is SMP. Check for Aegis SOC where a single
527	@ Cortex-A9 CPU is present but SMP operations fault.
528	mov	r4, #0x41000000
529	orr	r4, r4, #0x0000c000
530	orr	r4, r4, #0x00000090
531	teq	r3, r4			@ Check for ARM Cortex-A9
532	retne	lr			@ Not ARM Cortex-A9,
533
534	@ If a future SoC *does* use 0x0 as the PERIPH_BASE, then the
535	@ below address check will need to be #ifdef'd or equivalent
536	@ for the Aegis platform.
537	mrc	p15, 4, r0, c15, c0	@ get SCU base address
538	teq	r0, #0x0		@ '0' on actual UP A9 hardware
539	beq	__fixup_smp_on_up	@ So its an A9 UP
540	ldr	r0, [r0, #4]		@ read SCU Config
541ARM_BE8(rev	r0, r0)			@ byteswap if big endian
542	and	r0, r0, #0x3		@ number of CPUs
543	teq	r0, #0x0		@ is 1?
544	retne	lr
545
546__fixup_smp_on_up:
547	adr_l	r4, __smpalt_begin
548	adr_l	r5, __smpalt_end
549	b	__do_fixup_smp_on_up
550ENDPROC(__fixup_smp)
551
552	.pushsection .data
553	.align	2
554	.globl	smp_on_up
555smp_on_up:
556	ALT_SMP(.long	1)
557	ALT_UP(.long	0)
558	.popsection
559#endif
560
561	.text
562__do_fixup_smp_on_up:
563	cmp	r4, r5
564	reths	lr
565	ldmia	r4, {r0, r6}
566 ARM(	str	r6, [r0, r4]	)
567 THUMB(	add	r0, r0, r4	)
568	add	r4, r4, #8
569#ifdef __ARMEB__
570 THUMB(	mov	r6, r6, ror #16	)	@ Convert word order for big-endian.
571#endif
572 THUMB(	strh	r6, [r0], #2	)	@ For Thumb-2, store as two halfwords
573 THUMB(	mov	r6, r6, lsr #16	)	@ to be robust against misaligned r0.
574 THUMB(	strh	r6, [r0]	)
575	b	__do_fixup_smp_on_up
576ENDPROC(__do_fixup_smp_on_up)
577
578ENTRY(fixup_smp)
579	stmfd	sp!, {r4 - r6, lr}
580	mov	r4, r0
581	add	r5, r0, r1
582	bl	__do_fixup_smp_on_up
583	ldmfd	sp!, {r4 - r6, pc}
584ENDPROC(fixup_smp)
585
586#include "head-common.S"
587