1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * linux/arch/arm/kernel/head-common.S
4 *
5 * Copyright (C) 1994-2002 Russell King
6 * Copyright (c) 2003 ARM Limited
7 * All Rights Reserved
8 */
9 #include <asm/assembler.h>
10
11 #define ATAG_CORE 0x54410001
12 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
13 #define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
14
15 #ifdef CONFIG_CPU_BIG_ENDIAN
16 #define OF_DT_MAGIC 0xd00dfeed
17 #else
18 #define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
19 #endif
20
21 /*
22 * Exception handling. Something went wrong and we can't proceed. We
23 * ought to tell the user, but since we don't have any guarantee that
24 * we're even running on the right architecture, we do virtually nothing.
25 *
26 * If CONFIG_DEBUG_LL is set we try to print out something about the error
27 * and hope for the best (useful if bootloader fails to pass a proper
28 * machine ID for example).
29 */
30 __HEAD
31
32 /* Determine validity of the r2 atags pointer. The heuristic requires
33 * that the pointer be aligned, in the first 16k of physical RAM and
34 * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE
35 * is selected, then it will also accept a dtb pointer. Future revisions
36 * of this function may be more lenient with the physical address and
37 * may also be able to move the ATAGS block if necessary.
38 *
39 * Returns:
40 * r2 either valid atags pointer, valid dtb pointer, or zero
41 * r5, r6 corrupted
42 */
43 __vet_atags:
44 tst r2, #0x3 @ aligned?
45 bne 1f
46
47 ldr r5, [r2, #0]
48 #ifdef CONFIG_OF_FLATTREE
49 ldr r6, =OF_DT_MAGIC @ is it a DTB?
50 cmp r5, r6
51 beq 2f
52 #endif
53 cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE?
54 cmpne r5, #ATAG_CORE_SIZE_EMPTY
55 bne 1f
56 ldr r5, [r2, #4]
57 ldr r6, =ATAG_CORE
58 cmp r5, r6
59 bne 1f
60
61 2: ret lr @ atag/dtb pointer is ok
62
63 1: mov r2, #0
64 ret lr
65 ENDPROC(__vet_atags)
66
67 /*
68 * The following fragment of code is executed with the MMU on in MMU mode,
69 * and uses absolute addresses; this is not position independent.
70 *
71 * r0 = cp#15 control register (exc_ret for M-class)
72 * r1 = machine ID
73 * r2 = atags/dtb pointer
74 * r9 = processor ID
75 */
76 __INIT
77 __mmap_switched:
78
79 mov r7, r1
80 mov r8, r2
81 mov r10, r0
82
83 adr r4, __mmap_switched_data
84 mov fp, #0
85
86 #if defined(CONFIG_XIP_DEFLATED_DATA)
87 ARM( ldr sp, [r4], #4 )
88 THUMB( ldr sp, [r4] )
89 THUMB( add r4, #4 )
90 bl __inflate_kernel_data @ decompress .data to RAM
91 teq r0, #0
92 bne __error
93 #elif defined(CONFIG_XIP_KERNEL)
94 ARM( ldmia r4!, {r0, r1, r2, sp} )
95 THUMB( ldmia r4!, {r0, r1, r2, r3} )
96 THUMB( mov sp, r3 )
97 sub r2, r2, r1
98 bl __memcpy @ copy .data to RAM
99 #endif
100
101 ARM( ldmia r4!, {r0, r1, sp} )
102 THUMB( ldmia r4!, {r0, r1, r3} )
103 THUMB( mov sp, r3 )
104 sub r2, r1, r0
105 mov r1, #0
106 bl __memset @ clear .bss
107
108 adr_l r0, init_task @ get swapper task_struct
109 set_current r0, r1
110
111 ldmia r4, {r0, r1, r2, r3}
112 str r9, [r0] @ Save processor ID
113 str r7, [r1] @ Save machine type
114 str r8, [r2] @ Save atags pointer
115 cmp r3, #0
116 strne r10, [r3] @ Save control register values
117 #ifdef CONFIG_KASAN
118 bl kasan_early_init
119 #endif
120 mov lr, #0
121 b start_kernel
122 ENDPROC(__mmap_switched)
123
124 .align 2
125 .type __mmap_switched_data, %object
126 __mmap_switched_data:
127 #ifdef CONFIG_XIP_KERNEL
128 #ifndef CONFIG_XIP_DEFLATED_DATA
129 .long _sdata @ r0
130 .long __data_loc @ r1
131 .long _edata_loc @ r2
132 #endif
133 .long __bss_stop @ sp (temporary stack in .bss)
134 #endif
135
136 .long __bss_start @ r0
137 .long __bss_stop @ r1
138 .long init_thread_union + THREAD_START_SP @ sp
139
140 .long processor_id @ r0
141 .long __machine_arch_type @ r1
142 .long __atags_pointer @ r2
143 #ifdef CONFIG_CPU_CP15
144 .long cr_alignment @ r3
145 #else
146 M_CLASS(.long exc_ret) @ r3
147 AR_CLASS(.long 0) @ r3
148 #endif
149 .size __mmap_switched_data, . - __mmap_switched_data
150
151 __FINIT
152 .text
153
154 /*
155 * This provides a C-API version of __lookup_processor_type
156 */
157 ENTRY(lookup_processor_type)
158 stmfd sp!, {r4 - r6, r9, lr}
159 mov r9, r0
160 bl __lookup_processor_type
161 mov r0, r5
162 ldmfd sp!, {r4 - r6, r9, pc}
163 ENDPROC(lookup_processor_type)
164
165 /*
166 * Read processor ID register (CP#15, CR0), and look up in the linker-built
167 * supported processor list. Note that we can't use the absolute addresses
168 * for the __proc_info lists since we aren't running with the MMU on
169 * (and therefore, we are not in the correct address space). We have to
170 * calculate the offset.
171 *
172 * r9 = cpuid
173 * Returns:
174 * r3, r4, r6 corrupted
175 * r5 = proc_info pointer in physical address space
176 * r9 = cpuid (preserved)
177 */
178 __lookup_processor_type:
179 /*
180 * Look in <asm/procinfo.h> for information about the __proc_info
181 * structure.
182 */
183 adr_l r5, __proc_info_begin
184 adr_l r6, __proc_info_end
185 1: ldmia r5, {r3, r4} @ value, mask
186 and r4, r4, r9 @ mask wanted bits
187 teq r3, r4
188 beq 2f
189 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list)
190 cmp r5, r6
191 blo 1b
192 mov r5, #0 @ unknown processor
193 2: ret lr
194 ENDPROC(__lookup_processor_type)
195
196 __error_lpae:
197 #ifdef CONFIG_DEBUG_LL
198 adr r0, str_lpae
199 bl printascii
200 b __error
201 str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
202 #else
203 b __error
204 #endif
205 .align
206 ENDPROC(__error_lpae)
207
208 __error_p:
209 #ifdef CONFIG_DEBUG_LL
210 adr r0, str_p1
211 bl printascii
212 mov r0, r9
213 bl printhex8
214 adr r0, str_p2
215 bl printascii
216 b __error
217 str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x"
218 str_p2: .asciz ").\n"
219 .align
220 #endif
221 ENDPROC(__error_p)
222
223 __error:
224 #ifdef CONFIG_ARCH_RPC
225 /*
226 * Turn the screen red on a error - RiscPC only.
227 */
228 mov r0, #0x02000000
229 mov r3, #0x11
230 orr r3, r3, r3, lsl #8
231 orr r3, r3, r3, lsl #16
232 str r3, [r0], #4
233 str r3, [r0], #4
234 str r3, [r0], #4
235 str r3, [r0], #4
236 #endif
237 1: mov r0, r0
238 b 1b
239 ENDPROC(__error)
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