xref: /openbmc/linux/arch/arm/kernel/head.S (revision 6a143a7c) 
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/*
28 * swapper_pg_dir is the virtual address of the initial page table.
29 * We place the page tables 16K below KERNEL_RAM_VADDR.  Therefore, we must
30 * make sure that KERNEL_RAM_VADDR is correctly set.  Currently, we expect
31 * the least significant 16 bits to be 0x8000, but we could probably
32 * relax this restriction to KERNEL_RAM_VADDR >= PAGE_OFFSET + 0x4000.
33 */
34#define KERNEL_RAM_VADDR	(PAGE_OFFSET + TEXT_OFFSET)
35#if (KERNEL_RAM_VADDR & 0xffff) != 0x8000
36#error KERNEL_RAM_VADDR must start at 0xXXXX8000
37#endif
38
39#ifdef CONFIG_ARM_LPAE
40	/* LPAE requires an additional page for the PGD */
41#define PG_DIR_SIZE	0x5000
42#define PMD_ORDER	3
43#else
44#define PG_DIR_SIZE	0x4000
45#define PMD_ORDER	2
46#endif
47
48	.globl	swapper_pg_dir
49	.equ	swapper_pg_dir, KERNEL_RAM_VADDR - PG_DIR_SIZE
50
51	.macro	pgtbl, rd, phys
52	add	\rd, \phys, #TEXT_OFFSET
53	sub	\rd, \rd, #PG_DIR_SIZE
54	.endm
55
56/*
57 * Kernel startup entry point.
58 * ---------------------------
59 *
60 * This is normally called from the decompressor code.  The requirements
61 * are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
62 * r1 = machine nr, r2 = atags or dtb pointer.
63 *
64 * This code is mostly position independent, so if you link the kernel at
65 * 0xc0008000, you call this at __pa(0xc0008000).
66 *
67 * See linux/arch/arm/tools/mach-types for the complete list of machine
68 * numbers for r1.
69 *
70 * We're trying to keep crap to a minimum; DO NOT add any machine specific
71 * crap here - that's what the boot loader (or in extreme, well justified
72 * circumstances, zImage) is for.
73 */
74	.arm
75
76	__HEAD
77ENTRY(stext)
78 ARM_BE8(setend	be )			@ ensure we are in BE8 mode
79
80 THUMB(	badr	r9, 1f		)	@ Kernel is always entered in ARM.
81 THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
82 THUMB(	.thumb			)	@ switch to Thumb now.
83 THUMB(1:			)
84
85#ifdef CONFIG_ARM_VIRT_EXT
86	bl	__hyp_stub_install
87#endif
88	@ ensure svc mode and all interrupts masked
89	safe_svcmode_maskall r9
90
91	mrc	p15, 0, r9, c0, c0		@ get processor id
92	bl	__lookup_processor_type		@ r5=procinfo r9=cpuid
93	movs	r10, r5				@ invalid processor (r5=0)?
94 THUMB( it	eq )		@ force fixup-able long branch encoding
95	beq	__error_p			@ yes, error 'p'
96
97#ifdef CONFIG_ARM_LPAE
98	mrc	p15, 0, r3, c0, c1, 4		@ read ID_MMFR0
99	and	r3, r3, #0xf			@ extract VMSA support
100	cmp	r3, #5				@ long-descriptor translation table format?
101 THUMB( it	lo )				@ force fixup-able long branch encoding
102	blo	__error_lpae			@ only classic page table format
103#endif
104
105#ifndef CONFIG_XIP_KERNEL
106	adr_l	r8, _text			@ __pa(_text)
107	sub	r8, r8, #TEXT_OFFSET		@ PHYS_OFFSET
108#else
109	ldr	r8, =PLAT_PHYS_OFFSET		@ always constant in this case
110#endif
111
112	/*
113	 * r1 = machine no, r2 = atags or dtb,
114	 * r8 = phys_offset, r9 = cpuid, r10 = procinfo
115	 */
116	bl	__vet_atags
117#ifdef CONFIG_SMP_ON_UP
118	bl	__fixup_smp
119#endif
120#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
121	bl	__fixup_pv_table
122#endif
123	bl	__create_page_tables
124
125	/*
126	 * The following calls CPU specific code in a position independent
127	 * manner.  See arch/arm/mm/proc-*.S for details.  r10 = base of
128	 * xxx_proc_info structure selected by __lookup_processor_type
129	 * above.
130	 *
131	 * The processor init function will be called with:
132	 *  r1 - machine type
133	 *  r2 - boot data (atags/dt) pointer
134	 *  r4 - translation table base (low word)
135	 *  r5 - translation table base (high word, if LPAE)
136	 *  r8 - translation table base 1 (pfn if LPAE)
137	 *  r9 - cpuid
138	 *  r13 - virtual address for __enable_mmu -> __turn_mmu_on
139	 *
140	 * On return, the CPU will be ready for the MMU to be turned on,
141	 * r0 will hold the CPU control register value, r1, r2, r4, and
142	 * r9 will be preserved.  r5 will also be preserved if LPAE.
143	 */
144	ldr	r13, =__mmap_switched		@ address to jump to after
145						@ mmu has been enabled
146	badr	lr, 1f				@ return (PIC) address
147#ifdef CONFIG_ARM_LPAE
148	mov	r5, #0				@ high TTBR0
149	mov	r8, r4, lsr #12			@ TTBR1 is swapper_pg_dir pfn
150#else
151	mov	r8, r4				@ set TTBR1 to swapper_pg_dir
152#endif
153	ldr	r12, [r10, #PROCINFO_INITFUNC]
154	add	r12, r12, r10
155	ret	r12
1561:	b	__enable_mmu
157ENDPROC(stext)
158	.ltorg
159
160/*
161 * Setup the initial page tables.  We only setup the barest
162 * amount which are required to get the kernel running, which
163 * generally means mapping in the kernel code.
164 *
165 * r8 = phys_offset, r9 = cpuid, r10 = procinfo
166 *
167 * Returns:
168 *  r0, r3, r5-r7 corrupted
169 *  r4 = physical page table address
170 */
171__create_page_tables:
172	pgtbl	r4, r8				@ page table address
173
174	/*
175	 * Clear the swapper page table
176	 */
177	mov	r0, r4
178	mov	r3, #0
179	add	r6, r0, #PG_DIR_SIZE
1801:	str	r3, [r0], #4
181	str	r3, [r0], #4
182	str	r3, [r0], #4
183	str	r3, [r0], #4
184	teq	r0, r6
185	bne	1b
186
187#ifdef CONFIG_ARM_LPAE
188	/*
189	 * Build the PGD table (first level) to point to the PMD table. A PGD
190	 * entry is 64-bit wide.
191	 */
192	mov	r0, r4
193	add	r3, r4, #0x1000			@ first PMD table address
194	orr	r3, r3, #3			@ PGD block type
195	mov	r6, #4				@ PTRS_PER_PGD
196	mov	r7, #1 << (55 - 32)		@ L_PGD_SWAPPER
1971:
198#ifdef CONFIG_CPU_ENDIAN_BE8
199	str	r7, [r0], #4			@ set top PGD entry bits
200	str	r3, [r0], #4			@ set bottom PGD entry bits
201#else
202	str	r3, [r0], #4			@ set bottom PGD entry bits
203	str	r7, [r0], #4			@ set top PGD entry bits
204#endif
205	add	r3, r3, #0x1000			@ next PMD table
206	subs	r6, r6, #1
207	bne	1b
208
209	add	r4, r4, #0x1000			@ point to the PMD tables
210#ifdef CONFIG_CPU_ENDIAN_BE8
211	add	r4, r4, #4			@ we only write the bottom word
212#endif
213#endif
214
215	ldr	r7, [r10, #PROCINFO_MM_MMUFLAGS] @ mm_mmuflags
216
217	/*
218	 * Create identity mapping to cater for __enable_mmu.
219	 * This identity mapping will be removed by paging_init().
220	 */
221	adr_l	r5, __turn_mmu_on		@ _pa(__turn_mmu_on)
222	adr_l	r6, __turn_mmu_on_end		@ _pa(__turn_mmu_on_end)
223	mov	r5, r5, lsr #SECTION_SHIFT
224	mov	r6, r6, lsr #SECTION_SHIFT
225
2261:	orr	r3, r7, r5, lsl #SECTION_SHIFT	@ flags + kernel base
227	str	r3, [r4, r5, lsl #PMD_ORDER]	@ identity mapping
228	cmp	r5, r6
229	addlo	r5, r5, #1			@ next section
230	blo	1b
231
232	/*
233	 * Map our RAM from the start to the end of the kernel .bss section.
234	 */
235	add	r0, r4, #PAGE_OFFSET >> (SECTION_SHIFT - PMD_ORDER)
236	ldr	r6, =(_end - 1)
237	orr	r3, r8, r7
238	add	r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
2391:	str	r3, [r0], #1 << PMD_ORDER
240	add	r3, r3, #1 << SECTION_SHIFT
241	cmp	r0, r6
242	bls	1b
243
244#ifdef CONFIG_XIP_KERNEL
245	/*
246	 * Map the kernel image separately as it is not located in RAM.
247	 */
248#define XIP_START XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
249	mov	r3, pc
250	mov	r3, r3, lsr #SECTION_SHIFT
251	orr	r3, r7, r3, lsl #SECTION_SHIFT
252	add	r0, r4,  #(XIP_START & 0xff000000) >> (SECTION_SHIFT - PMD_ORDER)
253	str	r3, [r0, #((XIP_START & 0x00f00000) >> SECTION_SHIFT) << PMD_ORDER]!
254	ldr	r6, =(_edata_loc - 1)
255	add	r0, r0, #1 << PMD_ORDER
256	add	r6, r4, r6, lsr #(SECTION_SHIFT - PMD_ORDER)
2571:	cmp	r0, r6
258	add	r3, r3, #1 << SECTION_SHIFT
259	strls	r3, [r0], #1 << PMD_ORDER
260	bls	1b
261#endif
262
263	/*
264	 * Then map boot params address in r2 if specified.
265	 * We map 2 sections in case the ATAGs/DTB crosses a section boundary.
266	 */
267	mov	r0, r2, lsr #SECTION_SHIFT
268	cmp	r2, #0
269	ldrne	r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER)
270	addne	r3, r3, r4
271	orrne	r6, r7, r0, lsl #SECTION_SHIFT
272	strne	r6, [r3], #1 << PMD_ORDER
273	addne	r6, r6, #1 << SECTION_SHIFT
274	strne	r6, [r3]
275
276#if defined(CONFIG_ARM_LPAE) && defined(CONFIG_CPU_ENDIAN_BE8)
277	sub	r4, r4, #4			@ Fixup page table pointer
278						@ for 64-bit descriptors
279#endif
280
281#ifdef CONFIG_DEBUG_LL
282#if !defined(CONFIG_DEBUG_ICEDCC) && !defined(CONFIG_DEBUG_SEMIHOSTING)
283	/*
284	 * Map in IO space for serial debugging.
285	 * This allows debug messages to be output
286	 * via a serial console before paging_init.
287	 */
288	addruart r7, r3, r0
289
290	mov	r3, r3, lsr #SECTION_SHIFT
291	mov	r3, r3, lsl #PMD_ORDER
292
293	add	r0, r4, r3
294	mov	r3, r7, lsr #SECTION_SHIFT
295	ldr	r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
296	orr	r3, r7, r3, lsl #SECTION_SHIFT
297#ifdef CONFIG_ARM_LPAE
298	mov	r7, #1 << (54 - 32)		@ XN
299#ifdef CONFIG_CPU_ENDIAN_BE8
300	str	r7, [r0], #4
301	str	r3, [r0], #4
302#else
303	str	r3, [r0], #4
304	str	r7, [r0], #4
305#endif
306#else
307	orr	r3, r3, #PMD_SECT_XN
308	str	r3, [r0], #4
309#endif
310
311#else /* CONFIG_DEBUG_ICEDCC || CONFIG_DEBUG_SEMIHOSTING */
312	/* we don't need any serial debugging mappings */
313	ldr	r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
314#endif
315
316#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
317	/*
318	 * If we're using the NetWinder or CATS, we also need to map
319	 * in the 16550-type serial port for the debug messages
320	 */
321	add	r0, r4, #0xff000000 >> (SECTION_SHIFT - PMD_ORDER)
322	orr	r3, r7, #0x7c000000
323	str	r3, [r0]
324#endif
325#ifdef CONFIG_ARCH_RPC
326	/*
327	 * Map in screen at 0x02000000 & SCREEN2_BASE
328	 * Similar reasons here - for debug.  This is
329	 * only for Acorn RiscPC architectures.
330	 */
331	add	r0, r4, #0x02000000 >> (SECTION_SHIFT - PMD_ORDER)
332	orr	r3, r7, #0x02000000
333	str	r3, [r0]
334	add	r0, r4, #0xd8000000 >> (SECTION_SHIFT - PMD_ORDER)
335	str	r3, [r0]
336#endif
337#endif
338#ifdef CONFIG_ARM_LPAE
339	sub	r4, r4, #0x1000		@ point to the PGD table
340#endif
341	ret	lr
342ENDPROC(__create_page_tables)
343	.ltorg
344
345#if defined(CONFIG_SMP)
346	.text
347	.arm
348ENTRY(secondary_startup_arm)
349 THUMB(	badr	r9, 1f		)	@ Kernel is entered in ARM.
350 THUMB(	bx	r9		)	@ If this is a Thumb-2 kernel,
351 THUMB(	.thumb			)	@ switch to Thumb now.
352 THUMB(1:			)
353ENTRY(secondary_startup)
354	/*
355	 * Common entry point for secondary CPUs.
356	 *
357	 * Ensure that we're in SVC mode, and IRQs are disabled.  Lookup
358	 * the processor type - there is no need to check the machine type
359	 * as it has already been validated by the primary processor.
360	 */
361
362 ARM_BE8(setend	be)				@ ensure we are in BE8 mode
363
364#ifdef CONFIG_ARM_VIRT_EXT
365	bl	__hyp_stub_install_secondary
366#endif
367	safe_svcmode_maskall r9
368
369	mrc	p15, 0, r9, c0, c0		@ get processor id
370	bl	__lookup_processor_type
371	movs	r10, r5				@ invalid processor?
372	moveq	r0, #'p'			@ yes, error 'p'
373 THUMB( it	eq )		@ force fixup-able long branch encoding
374	beq	__error_p
375
376	/*
377	 * Use the page tables supplied from  __cpu_up.
378	 */
379	adr_l	r3, secondary_data
380	mov_l	r12, __secondary_switched
381	ldrd	r4, r5, [r3, #0]		@ get secondary_data.pgdir
382ARM_BE8(eor	r4, r4, r5)			@ Swap r5 and r4 in BE:
383ARM_BE8(eor	r5, r4, r5)			@ it can be done in 3 steps
384ARM_BE8(eor	r4, r4, r5)			@ without using a temp reg.
385	ldr	r8, [r3, #8]			@ get secondary_data.swapper_pg_dir
386	badr	lr, __enable_mmu		@ return address
387	mov	r13, r12			@ __secondary_switched address
388	ldr	r12, [r10, #PROCINFO_INITFUNC]
389	add	r12, r12, r10			@ initialise processor
390						@ (return control reg)
391	ret	r12
392ENDPROC(secondary_startup)
393ENDPROC(secondary_startup_arm)
394
395ENTRY(__secondary_switched)
396	ldr_l	r7, secondary_data + 12		@ get secondary_data.stack
397	mov	sp, r7
398	mov	fp, #0
399	b	secondary_start_kernel
400ENDPROC(__secondary_switched)
401
402#endif /* defined(CONFIG_SMP) */
403
404
405
406/*
407 * Setup common bits before finally enabling the MMU.  Essentially
408 * this is just loading the page table pointer and domain access
409 * registers.  All these registers need to be preserved by the
410 * processor setup function (or set in the case of r0)
411 *
412 *  r0  = cp#15 control register
413 *  r1  = machine ID
414 *  r2  = atags or dtb pointer
415 *  r4  = TTBR pointer (low word)
416 *  r5  = TTBR pointer (high word if LPAE)
417 *  r9  = processor ID
418 *  r13 = *virtual* address to jump to upon completion
419 */
420__enable_mmu:
421#if defined(CONFIG_ALIGNMENT_TRAP) && __LINUX_ARM_ARCH__ < 6
422	orr	r0, r0, #CR_A
423#else
424	bic	r0, r0, #CR_A
425#endif
426#ifdef CONFIG_CPU_DCACHE_DISABLE
427	bic	r0, r0, #CR_C
428#endif
429#ifdef CONFIG_CPU_BPREDICT_DISABLE
430	bic	r0, r0, #CR_Z
431#endif
432#ifdef CONFIG_CPU_ICACHE_DISABLE
433	bic	r0, r0, #CR_I
434#endif
435#ifdef CONFIG_ARM_LPAE
436	mcrr	p15, 0, r4, r5, c2		@ load TTBR0
437#else
438	mov	r5, #DACR_INIT
439	mcr	p15, 0, r5, c3, c0, 0		@ load domain access register
440	mcr	p15, 0, r4, c2, c0, 0		@ load page table pointer
441#endif
442	b	__turn_mmu_on
443ENDPROC(__enable_mmu)
444
445/*
446 * Enable the MMU.  This completely changes the structure of the visible
447 * memory space.  You will not be able to trace execution through this.
448 * If you have an enquiry about this, *please* check the linux-arm-kernel
449 * mailing list archives BEFORE sending another post to the list.
450 *
451 *  r0  = cp#15 control register
452 *  r1  = machine ID
453 *  r2  = atags or dtb pointer
454 *  r9  = processor ID
455 *  r13 = *virtual* address to jump to upon completion
456 *
457 * other registers depend on the function called upon completion
458 */
459	.align	5
460	.pushsection	.idmap.text, "ax"
461ENTRY(__turn_mmu_on)
462	mov	r0, r0
463	instr_sync
464	mcr	p15, 0, r0, c1, c0, 0		@ write control reg
465	mrc	p15, 0, r3, c0, c0, 0		@ read id reg
466	instr_sync
467	mov	r3, r3
468	mov	r3, r13
469	ret	r3
470__turn_mmu_on_end:
471ENDPROC(__turn_mmu_on)
472	.popsection
473
474
475#ifdef CONFIG_SMP_ON_UP
476	__HEAD
477__fixup_smp:
478	and	r3, r9, #0x000f0000	@ architecture version
479	teq	r3, #0x000f0000		@ CPU ID supported?
480	bne	__fixup_smp_on_up	@ no, assume UP
481
482	bic	r3, r9, #0x00ff0000
483	bic	r3, r3, #0x0000000f	@ mask 0xff00fff0
484	mov	r4, #0x41000000
485	orr	r4, r4, #0x0000b000
486	orr	r4, r4, #0x00000020	@ val 0x4100b020
487	teq	r3, r4			@ ARM 11MPCore?
488	reteq	lr			@ yes, assume SMP
489
490	mrc	p15, 0, r0, c0, c0, 5	@ read MPIDR
491	and	r0, r0, #0xc0000000	@ multiprocessing extensions and
492	teq	r0, #0x80000000		@ not part of a uniprocessor system?
493	bne    __fixup_smp_on_up	@ no, assume UP
494
495	@ Core indicates it is SMP. Check for Aegis SOC where a single
496	@ Cortex-A9 CPU is present but SMP operations fault.
497	mov	r4, #0x41000000
498	orr	r4, r4, #0x0000c000
499	orr	r4, r4, #0x00000090
500	teq	r3, r4			@ Check for ARM Cortex-A9
501	retne	lr			@ Not ARM Cortex-A9,
502
503	@ If a future SoC *does* use 0x0 as the PERIPH_BASE, then the
504	@ below address check will need to be #ifdef'd or equivalent
505	@ for the Aegis platform.
506	mrc	p15, 4, r0, c15, c0	@ get SCU base address
507	teq	r0, #0x0		@ '0' on actual UP A9 hardware
508	beq	__fixup_smp_on_up	@ So its an A9 UP
509	ldr	r0, [r0, #4]		@ read SCU Config
510ARM_BE8(rev	r0, r0)			@ byteswap if big endian
511	and	r0, r0, #0x3		@ number of CPUs
512	teq	r0, #0x0		@ is 1?
513	retne	lr
514
515__fixup_smp_on_up:
516	adr_l	r4, __smpalt_begin
517	adr_l	r5, __smpalt_end
518	b	__do_fixup_smp_on_up
519ENDPROC(__fixup_smp)
520
521	.pushsection .data
522	.align	2
523	.globl	smp_on_up
524smp_on_up:
525	ALT_SMP(.long	1)
526	ALT_UP(.long	0)
527	.popsection
528#endif
529
530	.text
531__do_fixup_smp_on_up:
532	cmp	r4, r5
533	reths	lr
534	ldmia	r4, {r0, r6}
535 ARM(	str	r6, [r0, r4]	)
536 THUMB(	add	r0, r0, r4	)
537	add	r4, r4, #8
538#ifdef __ARMEB__
539 THUMB(	mov	r6, r6, ror #16	)	@ Convert word order for big-endian.
540#endif
541 THUMB(	strh	r6, [r0], #2	)	@ For Thumb-2, store as two halfwords
542 THUMB(	mov	r6, r6, lsr #16	)	@ to be robust against misaligned r0.
543 THUMB(	strh	r6, [r0]	)
544	b	__do_fixup_smp_on_up
545ENDPROC(__do_fixup_smp_on_up)
546
547ENTRY(fixup_smp)
548	stmfd	sp!, {r4 - r6, lr}
549	mov	r4, r0
550	add	r5, r0, r1
551	bl	__do_fixup_smp_on_up
552	ldmfd	sp!, {r4 - r6, pc}
553ENDPROC(fixup_smp)
554
555#include "head-common.S"
556