diff options
Diffstat (limited to 'arch/arm/kernel/head-common.S')
| -rw-r--r-- | arch/arm/kernel/head-common.S | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S new file mode 100644 index 000000000..4a3982812 --- /dev/null +++ b/arch/arm/kernel/head-common.S @@ -0,0 +1,243 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/kernel/head-common.S + * + * Copyright (C) 1994-2002 Russell King + * Copyright (c) 2003 ARM Limited + * All Rights Reserved + */ +#include <asm/assembler.h> + +#define ATAG_CORE 0x54410001 +#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) +#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2) + +#ifdef CONFIG_CPU_BIG_ENDIAN +#define OF_DT_MAGIC 0xd00dfeed +#else +#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */ +#endif + +/* + * Exception handling. Something went wrong and we can't proceed. We + * ought to tell the user, but since we don't have any guarantee that + * we're even running on the right architecture, we do virtually nothing. + * + * If CONFIG_DEBUG_LL is set we try to print out something about the error + * and hope for the best (useful if bootloader fails to pass a proper + * machine ID for example). + */ + __HEAD + +/* Determine validity of the r2 atags pointer. The heuristic requires + * that the pointer be aligned, in the first 16k of physical RAM and + * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE + * is selected, then it will also accept a dtb pointer. Future revisions + * of this function may be more lenient with the physical address and + * may also be able to move the ATAGS block if necessary. + * + * Returns: + * r2 either valid atags pointer, valid dtb pointer, or zero + * r5, r6 corrupted + */ +__vet_atags: + tst r2, #0x3 @ aligned? + bne 1f + + ldr r5, [r2, #0] +#ifdef CONFIG_OF_FLATTREE + ldr r6, =OF_DT_MAGIC @ is it a DTB? + cmp r5, r6 + beq 2f +#endif + cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE? + cmpne r5, #ATAG_CORE_SIZE_EMPTY + bne 1f + ldr r5, [r2, #4] + ldr r6, =ATAG_CORE + cmp r5, r6 + bne 1f + +2: ret lr @ atag/dtb pointer is ok + +1: mov r2, #0 + ret lr +ENDPROC(__vet_atags) + +/* + * The following fragment of code is executed with the MMU on in MMU mode, + * and uses absolute addresses; this is not position independent. + * + * r0 = cp#15 control register (exc_ret for M-class) + * r1 = machine ID + * r2 = atags/dtb pointer + * r9 = processor ID + */ + __INIT +__mmap_switched: + + mov r7, r1 + mov r8, r2 + mov r10, r0 + + adr r4, __mmap_switched_data + mov fp, #0 + +#if defined(CONFIG_XIP_DEFLATED_DATA) + ARM( ldr sp, [r4], #4 ) + THUMB( ldr sp, [r4] ) + THUMB( add r4, #4 ) + bl __inflate_kernel_data @ decompress .data to RAM + teq r0, #0 + bne __error +#elif defined(CONFIG_XIP_KERNEL) + ARM( ldmia r4!, {r0, r1, r2, sp} ) + THUMB( ldmia r4!, {r0, r1, r2, r3} ) + THUMB( mov sp, r3 ) + sub r2, r2, r1 + bl memcpy @ copy .data to RAM +#endif + + ARM( ldmia r4!, {r0, r1, sp} ) + THUMB( ldmia r4!, {r0, r1, r3} ) + THUMB( mov sp, r3 ) + sub r2, r1, r0 + mov r1, #0 + bl memset @ clear .bss + + ldmia r4, {r0, r1, r2, r3} + str r9, [r0] @ Save processor ID + str r7, [r1] @ Save machine type + str r8, [r2] @ Save atags pointer + cmp r3, #0 + strne r10, [r3] @ Save control register values + mov lr, #0 + b start_kernel +ENDPROC(__mmap_switched) + + .align 2 + .type __mmap_switched_data, %object +__mmap_switched_data: +#ifdef CONFIG_XIP_KERNEL +#ifndef CONFIG_XIP_DEFLATED_DATA + .long _sdata @ r0 + .long __data_loc @ r1 + .long _edata_loc @ r2 +#endif + .long __bss_stop @ sp (temporary stack in .bss) +#endif + + .long __bss_start @ r0 + .long __bss_stop @ r1 + .long init_thread_union + THREAD_START_SP @ sp + + .long processor_id @ r0 + .long __machine_arch_type @ r1 + .long __atags_pointer @ r2 +#ifdef CONFIG_CPU_CP15 + .long cr_alignment @ r3 +#else +M_CLASS(.long exc_ret) @ r3 +AR_CLASS(.long 0) @ r3 +#endif + .size __mmap_switched_data, . - __mmap_switched_data + + __FINIT + .text + +/* + * This provides a C-API version of __lookup_processor_type + */ +ENTRY(lookup_processor_type) + stmfd sp!, {r4 - r6, r9, lr} + mov r9, r0 + bl __lookup_processor_type + mov r0, r5 + ldmfd sp!, {r4 - r6, r9, pc} +ENDPROC(lookup_processor_type) + +/* + * Read processor ID register (CP#15, CR0), and look up in the linker-built + * supported processor list. Note that we can't use the absolute addresses + * for the __proc_info lists since we aren't running with the MMU on + * (and therefore, we are not in the correct address space). We have to + * calculate the offset. + * + * r9 = cpuid + * Returns: + * r3, r4, r6 corrupted + * r5 = proc_info pointer in physical address space + * r9 = cpuid (preserved) + */ +__lookup_processor_type: + adr r3, __lookup_processor_type_data + ldmia r3, {r4 - r6} + sub r3, r3, r4 @ get offset between virt&phys + add r5, r5, r3 @ convert virt addresses to + add r6, r6, r3 @ physical address space +1: ldmia r5, {r3, r4} @ value, mask + and r4, r4, r9 @ mask wanted bits + teq r3, r4 + beq 2f + add r5, r5, #PROC_INFO_SZ @ sizeof(proc_info_list) + cmp r5, r6 + blo 1b + mov r5, #0 @ unknown processor +2: ret lr +ENDPROC(__lookup_processor_type) + +/* + * Look in <asm/procinfo.h> for information about the __proc_info structure. + */ + .align 2 + .type __lookup_processor_type_data, %object +__lookup_processor_type_data: + .long . + .long __proc_info_begin + .long __proc_info_end + .size __lookup_processor_type_data, . - __lookup_processor_type_data + +__error_lpae: +#ifdef CONFIG_DEBUG_LL + adr r0, str_lpae + bl printascii + b __error +str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n" +#else + b __error +#endif + .align +ENDPROC(__error_lpae) + +__error_p: +#ifdef CONFIG_DEBUG_LL + adr r0, str_p1 + bl printascii + mov r0, r9 + bl printhex8 + adr r0, str_p2 + bl printascii + b __error +str_p1: .asciz "\nError: unrecognized/unsupported processor variant (0x" +str_p2: .asciz ").\n" + .align +#endif +ENDPROC(__error_p) + +__error: +#ifdef CONFIG_ARCH_RPC +/* + * Turn the screen red on a error - RiscPC only. + */ + mov r0, #0x02000000 + mov r3, #0x11 + orr r3, r3, r3, lsl #8 + orr r3, r3, r3, lsl #16 + str r3, [r0], #4 + str r3, [r0], #4 + str r3, [r0], #4 + str r3, [r0], #4 +#endif +1: mov r0, r0 + b 1b +ENDPROC(__error) |