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 17 .type __switch_data, %object 18__switch_data: 19 .long __mmap_switched 20 .long __data_loc @ r4 21 .long __data_start @ r5 22 .long __bss_start @ r6 23 .long _end @ r7 24 .long processor_id @ r4 25 .long __machine_arch_type @ r5 26 .long __atags_pointer @ r6 27 .long cr_alignment @ r7 28 .long init_thread_union + THREAD_START_SP @ sp 29 30/* 31 * The following fragment of code is executed with the MMU on in MMU mode, 32 * and uses absolute addresses; this is not position independent. 33 * 34 * r0 = cp#15 control register 35 * r1 = machine ID 36 * r2 = atags pointer 37 * r9 = processor ID 38 */ 39__mmap_switched: 40 adr r3, __switch_data + 4 41 42 ldmia r3!, {r4, r5, r6, r7} 43 cmp r4, r5 @ Copy data segment if needed 441: cmpne r5, r6 45 ldrne fp, [r4], #4 46 strne fp, [r5], #4 47 bne 1b 48 49 mov fp, #0 @ Clear BSS (and zero fp) 501: cmp r6, r7 51 strcc fp, [r6],#4 52 bcc 1b 53 54 ldmia r3, {r4, r5, r6, r7, sp} 55 str r9, [r4] @ Save processor ID 56 str r1, [r5] @ Save machine type 57 str r2, [r6] @ Save atags pointer 58 bic r4, r0, #CR_A @ Clear 'A' bit 59 stmia r7, {r0, r4} @ Save control register values 60 b start_kernel 61ENDPROC(__mmap_switched) 62 63/* 64 * Exception handling. Something went wrong and we can't proceed. We 65 * ought to tell the user, but since we don't have any guarantee that 66 * we're even running on the right architecture, we do virtually nothing. 67 * 68 * If CONFIG_DEBUG_LL is set we try to print out something about the error 69 * and hope for the best (useful if bootloader fails to pass a proper 70 * machine ID for example). 71 */ 72__error_p: 73#ifdef CONFIG_DEBUG_LL 74 adr r0, str_p1 75 bl printascii 76 mov r0, r9 77 bl printhex8 78 adr r0, str_p2 79 bl printascii 80 b __error 81str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x" 82str_p2: .asciz ").\n" 83 .align 84#endif 85ENDPROC(__error_p) 86 87__error_a: 88#ifdef CONFIG_DEBUG_LL 89 mov r4, r1 @ preserve machine ID 90 adr r0, str_a1 91 bl printascii 92 mov r0, r4 93 bl printhex8 94 adr r0, str_a2 95 bl printascii 96 adr r3, 3f 97 ldmia r3, {r4, r5, r6} @ get machine desc list 98 sub r4, r3, r4 @ get offset between virt&phys 99 add r5, r5, r4 @ convert virt addresses to 100 add r6, r6, r4 @ physical address space 1011: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type 102 bl printhex8 103 mov r0, #'\t' 104 bl printch 105 ldr r0, [r5, #MACHINFO_NAME] @ get machine name 106 add r0, r0, r4 107 bl printascii 108 mov r0, #'\n' 109 bl printch 110 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc 111 cmp r5, r6 112 blo 1b 113 adr r0, str_a3 114 bl printascii 115 b __error 116ENDPROC(__error_a) 117 118str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x" 119str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n" 120str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n" 121 .align 122#endif 123 124__error: 125#ifdef CONFIG_ARCH_RPC 126/* 127 * Turn the screen red on a error - RiscPC only. 128 */ 129 mov r0, #0x02000000 130 mov r3, #0x11 131 orr r3, r3, r3, lsl #8 132 orr r3, r3, r3, lsl #16 133 str r3, [r0], #4 134 str r3, [r0], #4 135 str r3, [r0], #4 136 str r3, [r0], #4 137#endif 1381: mov r0, r0 139 b 1b 140ENDPROC(__error) 141 142 143/* 144 * Read processor ID register (CP#15, CR0), and look up in the linker-built 145 * supported processor list. Note that we can't use the absolute addresses 146 * for the __proc_info lists since we aren't running with the MMU on 147 * (and therefore, we are not in the correct address space). We have to 148 * calculate the offset. 149 * 150 * r9 = cpuid 151 * Returns: 152 * r3, r4, r6 corrupted 153 * r5 = proc_info pointer in physical address space 154 * r9 = cpuid (preserved) 155 */ 156__lookup_processor_type: 157 adr r3, 3f 158 ldmda r3, {r5 - r7} 159 sub r3, r3, r7 @ get offset between virt&phys 160 add r5, r5, r3 @ convert virt addresses to 161 add r6, r6, r3 @ physical address space 1621: ldmia r5, {r3, r4} @ value, mask 163 and r4, r4, r9 @ mask wanted bits 164 teq r3, r4 165 beq 2f 166 add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list) 167 cmp r5, r6 168 blo 1b 169 mov r5, #0 @ unknown processor 1702: mov pc, lr 171ENDPROC(__lookup_processor_type) 172 173/* 174 * This provides a C-API version of the above function. 175 */ 176ENTRY(lookup_processor_type) 177 stmfd sp!, {r4 - r7, r9, lr} 178 mov r9, r0 179 bl __lookup_processor_type 180 mov r0, r5 181 ldmfd sp!, {r4 - r7, r9, pc} 182ENDPROC(lookup_processor_type) 183 184/* 185 * Look in <asm/procinfo.h> and arch/arm/kernel/arch.[ch] for 186 * more information about the __proc_info and __arch_info structures. 187 */ 188 .long __proc_info_begin 189 .long __proc_info_end 1903: .long . 191 .long __arch_info_begin 192 .long __arch_info_end 193 194/* 195 * Lookup machine architecture in the linker-build list of architectures. 196 * Note that we can't use the absolute addresses for the __arch_info 197 * lists since we aren't running with the MMU on (and therefore, we are 198 * not in the correct address space). We have to calculate the offset. 199 * 200 * r1 = machine architecture number 201 * Returns: 202 * r3, r4, r6 corrupted 203 * r5 = mach_info pointer in physical address space 204 */ 205__lookup_machine_type: 206 adr r3, 3b 207 ldmia r3, {r4, r5, r6} 208 sub r3, r3, r4 @ get offset between virt&phys 209 add r5, r5, r3 @ convert virt addresses to 210 add r6, r6, r3 @ physical address space 2111: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type 212 teq r3, r1 @ matches loader number? 213 beq 2f @ found 214 add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc 215 cmp r5, r6 216 blo 1b 217 mov r5, #0 @ unknown machine 2182: mov pc, lr 219ENDPROC(__lookup_machine_type) 220 221/* 222 * This provides a C-API version of the above function. 223 */ 224ENTRY(lookup_machine_type) 225 stmfd sp!, {r4 - r6, lr} 226 mov r1, r0 227 bl __lookup_machine_type 228 mov r0, r5 229 ldmfd sp!, {r4 - r6, pc} 230ENDPROC(lookup_machine_type) 231 232/* Determine validity of the r2 atags pointer. The heuristic requires 233 * that the pointer be aligned, in the first 16k of physical RAM and 234 * that the ATAG_CORE marker is first and present. Future revisions 235 * of this function may be more lenient with the physical address and 236 * may also be able to move the ATAGS block if necessary. 237 * 238 * r8 = machinfo 239 * 240 * Returns: 241 * r2 either valid atags pointer, or zero 242 * r5, r6 corrupted 243 */ 244__vet_atags: 245 tst r2, #0x3 @ aligned? 246 bne 1f 247 248 ldr r5, [r2, #0] @ is first tag ATAG_CORE? 249 subs r5, r5, #ATAG_CORE_SIZE 250 bne 1f 251 ldr r5, [r2, #4] 252 ldr r6, =ATAG_CORE 253 cmp r5, r6 254 bne 1f 255 256 mov pc, lr @ atag pointer is ok 257 2581: mov r2, #0 259 mov pc, lr 260ENDPROC(__vet_atags) 261