blob: a7810be07da1c56c1502a72b60d7bc3da8075d91 [file] [log] [blame]
/* 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)
#define OF_DT_MAGIC 0xd00dfeed
#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
* 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).
/* 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
tst r2, #0x3 @ aligned?
bne 1f
ldr r5, [r2, #0]
ldr r6, =OF_DT_MAGIC @ is it a DTB?
cmp r5, r6
beq 2f
cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE?
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
* 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
* r1 = machine ID
* r2 = atags/dtb pointer
* r9 = processor ID
mov r7, r1
mov r8, r2
mov r10, r0
adr r4, __mmap_switched_data
mov fp, #0
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
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
.align 2
.type __mmap_switched_data, %object
.long _sdata @ r0
.long __data_loc @ r1
.long _edata_loc @ r2
.long __bss_stop @ sp (temporary stack in .bss)
.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
.long 0 @ r3
.size __mmap_switched_data, . - __mmap_switched_data
* This provides a C-API version of __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}
* 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)
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
* Look in <asm/procinfo.h> for information about the __proc_info structure.
.align 2
.type __lookup_processor_type_data, %object
.long .
.long __proc_info_begin
.long __proc_info_end
.size __lookup_processor_type_data, . - __lookup_processor_type_data
adr r0, str_lpae
bl printascii
b __error
str_lpae: .asciz "\nError: Kernel with LPAE support, but CPU does not support LPAE.\n"
b __error
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"
* 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
1: mov r0, r0
b 1b