1/* 2 * linux/arch/arm/kernel/head-common.S 3 * 4 * Copyright (C) 1994-2002 Russell King 5 * Copyright (c) 2003 ARM Limited 6 * All Rights Reserved 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 * 12 */ 13 14#define ATAG_CORE 0x54410001 15#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) 16#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2) 17 18/* 19 * Exception handling. Something went wrong and we can't proceed. We 20 * ought to tell the user, but since we don't have any guarantee that 21 * we're even running on the right architecture, we do virtually nothing. 22 * 23 * If CONFIG_DEBUG_LL is set we try to print out something about the error 24 * and hope for the best (useful if bootloader fails to pass a proper 25 * machine ID for example). 26 */ 27 __HEAD 28__error_a: 29#ifdef CONFIG_DEBUG_LL 30 mov r4, r1 @ preserve machine ID 31 adr r0, str_a1 32 bl printascii 33 mov r0, r4 34 bl printhex8 35 adr r0, str_a2 36 bl printascii 37 adr r3, __lookup_machine_type_data 38 ldmia r3, {r4, r5, r6} @ get machine desc list 39 sub r4, r3, r4 @ get offset between virt&phys 40 add r5, r5, r4 @ convert virt addresses to 41 add r6, r6, r4 @ physical address space 421: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type 43 bl printhex8 44 mov r0, #'\t' 45 bl printch 46 ldr r0, [r5, #MACHINFO_NAME] @ get machine name 47 add r0, r0, r4 48 bl printascii 49 mov r0, #'\n' 50 bl printch 51 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc 52 cmp r5, r6 53 blo 1b 54 adr r0, str_a3 55 bl printascii 56 b __error 57ENDPROC(__error_a) 58 59str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x" 60str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n" 61str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n" 62 .align 63#else 64 b __error 65#endif 66 67/* 68 * Lookup machine architecture in the linker-build list of architectures. 69 * Note that we can't use the absolute addresses for the __arch_info 70 * lists since we aren't running with the MMU on (and therefore, we are 71 * not in the correct address space). We have to calculate the offset. 72 * 73 * r1 = machine architecture number 74 * Returns: 75 * r3, r4, r6 corrupted 76 * r5 = mach_info pointer in physical address space 77 */ 78__lookup_machine_type: 79 adr r3, __lookup_machine_type_data 80 ldmia r3, {r4, r5, r6} 81 sub r3, r3, r4 @ get offset between virt&phys 82 add r5, r5, r3 @ convert virt addresses to 83 add r6, r6, r3 @ physical address space 841: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type 85 teq r3, r1 @ matches loader number? 86 beq 2f @ found 87 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc 88 cmp r5, r6 89 blo 1b 90 mov r5, #0 @ unknown machine 912: mov pc, lr 92ENDPROC(__lookup_machine_type) 93 94/* 95 * Look in arch/arm/kernel/arch.[ch] for information about the 96 * __arch_info structures. 97 */ 98 .align 2 99 .type __lookup_machine_type_data, %object 100__lookup_machine_type_data: 101 .long . 102 .long __arch_info_begin 103 .long __arch_info_end 104 .size __lookup_machine_type_data, . - __lookup_machine_type_data 105 106/* Determine validity of the r2 atags pointer. The heuristic requires 107 * that the pointer be aligned, in the first 16k of physical RAM and 108 * that the ATAG_CORE marker is first and present. Future revisions 109 * of this function may be more lenient with the physical address and 110 * may also be able to move the ATAGS block if necessary. 111 * 112 * r8 = machinfo 113 * 114 * Returns: 115 * r2 either valid atags pointer, or zero 116 * r5, r6 corrupted 117 */ 118__vet_atags: 119 tst r2, #0x3 @ aligned? 120 bne 1f 121 122 ldr r5, [r2, #0] @ is first tag ATAG_CORE? 123 cmp r5, #ATAG_CORE_SIZE 124 cmpne r5, #ATAG_CORE_SIZE_EMPTY 125 bne 1f 126 ldr r5, [r2, #4] 127 ldr r6, =ATAG_CORE 128 cmp r5, r6 129 bne 1f 130 131 mov pc, lr @ atag pointer is ok 132 1331: mov r2, #0 134 mov pc, lr 135ENDPROC(__vet_atags) 136 137/* 138 * The following fragment of code is executed with the MMU on in MMU mode, 139 * and uses absolute addresses; this is not position independent. 140 * 141 * r0 = cp#15 control register 142 * r1 = machine ID 143 * r2 = atags pointer 144 * r9 = processor ID 145 */ 146 __INIT 147__mmap_switched: 148 adr r3, __mmap_switched_data 149 150 ldmia r3!, {r4, r5, r6, r7} 151 cmp r4, r5 @ Copy data segment if needed 1521: cmpne r5, r6 153 ldrne fp, [r4], #4 154 strne fp, [r5], #4 155 bne 1b 156 157 mov fp, #0 @ Clear BSS (and zero fp) 1581: cmp r6, r7 159 strcc fp, [r6],#4 160 bcc 1b 161 162 ARM( ldmia r3, {r4, r5, r6, r7, sp}) 163 THUMB( ldmia r3, {r4, r5, r6, r7} ) 164 THUMB( ldr sp, [r3, #16] ) 165 str r9, [r4] @ Save processor ID 166 str r1, [r5] @ Save machine type 167 str r2, [r6] @ Save atags pointer 168 bic r4, r0, #CR_A @ Clear 'A' bit 169 stmia r7, {r0, r4} @ Save control register values 170 b start_kernel 171ENDPROC(__mmap_switched) 172 173 .align 2 174 .type __mmap_switched_data, %object 175__mmap_switched_data: 176 .long __data_loc @ r4 177 .long _sdata @ r5 178 .long __bss_start @ r6 179 .long _end @ r7 180 .long processor_id @ r4 181 .long __machine_arch_type @ r5 182 .long __atags_pointer @ r6 183 .long cr_alignment @ r7 184 .long init_thread_union + THREAD_START_SP @ sp 185 .size __mmap_switched_data, . - __mmap_switched_data 186 187/* 188 * This provides a C-API version of __lookup_machine_type 189 */ 190ENTRY(lookup_machine_type) 191 stmfd sp!, {r4 - r6, lr} 192 mov r1, r0 193 bl __lookup_machine_type 194 mov r0, r5 195 ldmfd sp!, {r4 - r6, pc} 196ENDPROC(lookup_machine_type) 197 198/* 199 * This provides a C-API version of __lookup_processor_type 200 */ 201ENTRY(lookup_processor_type) 202 stmfd sp!, {r4 - r6, r9, lr} 203 mov r9, r0 204 bl __lookup_processor_type 205 mov r0, r5 206 ldmfd sp!, {r4 - r6, r9, pc} 207ENDPROC(lookup_processor_type) 208 209/* 210 * Read processor ID register (CP#15, CR0), and look up in the linker-built 211 * supported processor list. Note that we can't use the absolute addresses 212 * for the __proc_info lists since we aren't running with the MMU on 213 * (and therefore, we are not in the correct address space). We have to 214 * calculate the offset. 215 * 216 * r9 = cpuid 217 * Returns: 218 * r3, r4, r6 corrupted 219 * r5 = proc_info pointer in physical address space 220 * r9 = cpuid (preserved) 221 */ 222 __CPUINIT 223__lookup_processor_type: 224 adr r3, __lookup_processor_type_data 225 ldmia r3, {r4 - r6} 226 sub r3, r3, r4 @ get offset between virt&phys 227 add r5, r5, r3 @ convert virt addresses to 228 add r6, r6, r3 @ physical address space 2291: ldmia r5, {r3, r4} @ value, mask 230 and r4, r4, r9 @ mask wanted bits 231 teq r3, r4 232 beq 2f 233 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list) 234 cmp r5, r6 235 blo 1b 236 mov r5, #0 @ unknown processor 2372: mov pc, lr 238ENDPROC(__lookup_processor_type) 239 240/* 241 * Look in <asm/procinfo.h> for information about the __proc_info structure. 242 */ 243 .align 2 244 .type __lookup_processor_type_data, %object 245__lookup_processor_type_data: 246 .long . 247 .long __proc_info_begin 248 .long __proc_info_end 249 .size __lookup_processor_type_data, . - __lookup_processor_type_data 250 251__error_p: 252#ifdef CONFIG_DEBUG_LL 253 adr r0, str_p1 254 bl printascii 255 mov r0, r9 256 bl printhex8 257 adr r0, str_p2 258 bl printascii 259 b __error 260str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x" 261str_p2: .asciz ").\n" 262 .align 263#endif 264ENDPROC(__error_p) 265 266__error: 267#ifdef CONFIG_ARCH_RPC 268/* 269 * Turn the screen red on a error - RiscPC only. 270 */ 271 mov r0, #0x02000000 272 mov r3, #0x11 273 orr r3, r3, r3, lsl #8 274 orr r3, r3, r3, lsl #16 275 str r3, [r0], #4 276 str r3, [r0], #4 277 str r3, [r0], #4 278 str r3, [r0], #4 279#endif 2801: mov r0, r0 281 b 1b 282ENDPROC(__error) 283