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) 240