/*
* linux/arch/arm/kernel/head.S
*
* Copyright (C) 1994-2002 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Kernel startup code for all 32-bit CPUs
*/
#include <linux/config.h>
#include <linux/linkage.h>
#include <linux/init.h>
#include <asm/assembler.h>
#include <asm/domain.h>
#include <asm/mach-types.h>
#include <asm/procinfo.h>
#include <asm/ptrace.h>
#include <asm/constants.h>
#include <asm/system.h>
#define PROCINFO_MMUFLAGS 8
#define PROCINFO_INITFUNC 12
#define MACHINFO_TYPE 0
#define MACHINFO_PHYSRAM 4
#define MACHINFO_PHYSIO 8
#define MACHINFO_PGOFFIO 12
#define MACHINFO_NAME 16
#ifndef CONFIG_XIP_KERNEL
/*
* We place the page tables 16K below TEXTADDR. Therefore, we must make sure
* that TEXTADDR is correctly set. Currently, we expect the least significant
* 16 bits to be 0x8000, but we could probably relax this restriction to
* TEXTADDR >= PAGE_OFFSET + 0x4000
*
* Note that swapper_pg_dir is the virtual address of the page tables, and
* pgtbl gives us a position-independent reference to these tables. We can
* do this because stext == TEXTADDR
*/
#if (TEXTADDR & 0xffff) != 0x8000
#error TEXTADDR must start at 0xXXXX8000
#endif
.globl swapper_pg_dir
.equ swapper_pg_dir, TEXTADDR - 0x4000
.macro pgtbl, rd, phys
adr \rd, stext
sub \rd, \rd, #0x4000
.endm
#else
/*
* XIP Kernel:
*
* We place the page tables 16K below DATAADDR. Therefore, we must make sure
* that DATAADDR is correctly set. Currently, we expect the least significant
* 16 bits to be 0x8000, but we could probably relax this restriction to
* DATAADDR >= PAGE_OFFSET + 0x4000
*
* Note that pgtbl is meant to return the physical address of swapper_pg_dir.
* We can't make it relative to the kernel position in this case since
* the kernel can physically be anywhere.
*/
#if (DATAADDR & 0xffff) != 0x8000
#error DATAADDR must start at 0xXXXX8000
#endif
.globl swapper_pg_dir
.equ swapper_pg_dir, DATAADDR - 0x4000
.macro pgtbl, rd, phys
ldr \rd, =((DATAADDR - 0x4000) - VIRT_OFFSET)
add \rd, \rd, \phys
.endm
#endif
/*
* Kernel startup entry point.
* ---------------------------
*
* This is normally called from the decompressor code. The requirements
* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
* r1 = machine nr.
*
* This code is mostly position independent, so if you link the kernel at
* 0xc0008000, you call this at __pa(0xc0008000).
*
* See linux/arch/arm/tools/mach-types for the complete list of machine
* numbers for r1.
*
* We're trying to keep crap to a minimum; DO NOT add any machine specific
* crap here - that's what the boot loader (or in extreme, well justified
* circumstances, zImage) is for.
*/
__INIT
.type stext, %function
ENTRY(stext)
msr cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC @ ensure svc mode
@ and irqs disabled
bl __lookup_processor_type @ r5=procinfo r9=cpuid
movs r10, r5 @ invalid processor (r5=0)?
beq __error_p @ yes, error 'p'
bl __lookup_machine_type @ r5=machinfo
movs r8, r5 @ invalid machine (r5=0)?
beq __error_a @ yes, error 'a'
bl __create_page_tables
/*
* The following calls CPU specific code in a position independent
* manner. See arch/arm/mm/proc-*.S for details. r10 = base of
* xxx_proc_info structure selected by __lookup_machine_type
* above. On return, the CPU will be ready for the MMU to be
* turned on, and r0 will hold the CPU control register value.
*/
ldr r13, __switch_data @ address to jump to after
@ mmu has been enabled
adr lr, __enable_mmu @ return (PIC) address
add pc, r10, #PROCINFO_INITFUNC
.type __switch_data, %object
__switch_data:
.long __mmap_switched
.long __data_loc @ r4
.long __data_start @ r5
.long __bss_start @ r6
.long _end @ r7
.long processor_id @ r4
.long __machine_arch_type @ r5
.long cr_alignment @ r6
.long init_thread_union+8192 @ sp
/*
* The following fragment of code is executed with the MMU on, and uses
* absolute addresses; this is not position independent.
*
* r0 = cp#15 control register
* r1 = machine ID
* r9 = processor ID
*/
.type __mmap_switched, %function
__mmap_switched:
adr r3, __switch_data + 4
ldmia r3!, {r4, r5, r6, r7}
cmp r4, r5 @ Copy data segment if needed
1: cmpne r5, r6
ldrne fp, [r4], #4
strne fp, [r5], #4
bne 1b
mov fp, #0 @ Clear BSS (and zero fp)
1: cmp r6, r7
strcc fp, [r6],#4
bcc 1b
ldmia r3, {r4, r5, r6, sp}
str r9, [r4] @ Save processor ID
str r1, [r5] @ Save machine type
bic r4, r0, #CR_A @ Clear 'A' bit
stmia r6, {r0, r4} @ Save control register values
b start_kernel
/*
* Setup common bits before finally enabling the MMU. Essentially
* this is just loading the page table pointer and domain access
* registers.
*/
.type __enable_mmu, %function
__enable_mmu:
#ifdef CONFIG_ALIGNMENT_TRAP
orr r0, r0, #CR_A
#else
bic r0, r0, #CR_A
#endif
#ifdef CONFIG_CPU_DCACHE_DISABLE
bic r0, r0, #CR_C
#endif
#ifdef CONFIG_CPU_BPREDICT_DISABLE
bic r0, r0, #CR_Z
#endif
#ifdef CONFIG_CPU_ICACHE_DISABLE
bic r0, r0, #CR_I
#endif
mov r5, #(domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
domain_val(DOMAIN_TABLE, DOMAIN_MANAGER) | \
domain_val(DOMAIN_IO, DOMAIN_CLIENT))
mcr p15, 0, r5, c3, c0, 0 @ load domain access register
mcr p15, 0, r4, c2, c0, 0 @ load page table pointer
b __turn_mmu_on
/*
* Enable the MMU. This completely changes the structure of the visible
* memory space. You will not be able to trace execution through this.
* If you have an enquiry about this, *please* check the linux-arm-kernel
* mailing list archives BEFORE sending another post to the list.
*
* r0 = cp#15 control register
* r13 = *virtual* address to jump to upon completion
*
* other registers depend on the function called upon completion
*/
.align 5
.type __turn_mmu_on, %function
__turn_mmu_on:
mov r0, r0
mcr p15, 0, r0, c1, c0, 0 @ write control reg
mrc p15, 0, r3, c0, c0, 0 @ read id reg
mov r3, r3
mov r3, r3
mov pc, r13
/*
* Setup the initial page tables. We only setup the barest
* amount which are required to get the kernel running, which
* generally means mapping in the kernel code.
*
* r8 = machinfo
* r9 = cpuid
* r10 = procinfo
*
* Returns:
* r0, r3, r5, r6, r7 corrupted
* r4 = physical page table address
*/
.type __create_page_tables, %function
__create_page_tables:
ldr r5, [r8, #MACHINFO_PHYSRAM] @ physram
pgtbl r4, r5 @ page table address
/*
* Clear the 16K level 1 swapper page table
*/
mov r0, r4
mov r3, #0
add r6, r0, #0x4000
1: str r3, [r0], #4
str r3, [r0], #4
str r3, [r0], #4
str r3, [r0], #4
teq r0, r6
bne 1b
ldr r7, [r10, #PROCINFO_MMUFLAGS] @ mmuflags
/*
* Create identity mapping for first MB of kernel to
* cater for the MMU enable. This identity mapping
* will be removed by paging_init(). We use our current program
* counter to determine corresponding section base address.
*/
mov r6, pc, lsr #20 @ start of kernel section
orr r3, r7, r6, lsl #20 @ flags + kernel base
str r3, [r4, r6, lsl #2] @ identity mapping
/*
* Now setup the pagetables for our kernel direct
* mapped region. We round TEXTADDR down to the
* nearest megabyte boundary. It is assumed that
* the kernel fits within 4 contigous 1MB sections.
*/
add r0, r4, #(TEXTADDR & 0xff000000) >> 18 @ start of kernel
str r3, [r0, #(TEXTADDR & 0x00f00000) >> 18]!
add r3, r3, #1 << 20
str r3, [r0, #4]! @ KERNEL + 1MB
add r3, r3, #1 << 20
str r3, [r0, #4]! @ KERNEL + 2MB
add r3, r3, #1 << 20
str r3, [r0, #4] @ KERNEL + 3MB
/*
* Then map first 1MB of ram in case it contains our boot params.
*/
add r0, r4, #VIRT_OFFSET >> 18
orr r6, r5, r7
str r6, [r0]
#ifdef CONFIG_XIP_KERNEL
/*
* Map some ram to cover our .data and .bss areas.
* Mapping 3MB should be plenty.
*/
sub r3, r4, r5
mov r3, r3, lsr #20
add r0, r0, r3, lsl #2
add r6, r6, r3, lsl #20
str r6, [r0], #4
add r6, r6, #(1 << 20)
str r6, [r0], #4
add r6, r6, #(1 << 20)
str r6, [r0]
#endif
bic r7, r7, #0x0c @ turn off cacheable
@ and bufferable bits
#ifdef CONFIG_DEBUG_LL
/*
* Map in IO space for serial debugging.
* This allows debug messages to be output
* via a serial console before paging_init.
*/
ldr r3, [r8, #MACHINFO_PGOFFIO]
add r0, r4, r3
rsb r3, r3, #0x4000 @ PTRS_PER_PGD*sizeof(long)
cmp r3, #0x0800 @ limit to 512MB
movhi r3, #0x0800
add r6, r0, r3
ldr r3, [r8, #MACHINFO_PHYSIO]
orr r3, r3, r7
1: str r3, [r0], #4
add r3, r3, #1 << 20
teq r0, r6
bne 1b
#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
/*
* If we're using the NetWinder, we need to map in
* the 16550-type serial port for the debug messages
*/
teq r1, #MACH_TYPE_NETWINDER
teqne r1, #MACH_TYPE_CATS
bne 1f
add r0, r4, #0x3fc0 @ ff000000
mov r3, #0x7c000000
orr r3, r3, r7
str r3, [r0], #4
add r3, r3, #1 << 20
str r3, [r0], #4
1:
#endif
#endif
#ifdef CONFIG_ARCH_RPC
/*
* Map in screen at 0x02000000 & SCREEN2_BASE
* Similar reasons here - for debug. This is
* only for Acorn RiscPC architectures.
*/
add r0, r4, #0x80 @ 02000000
mov r3, #0x02000000
orr r3, r3, r7
str r3, [r0]
add r0, r4, #0x3600 @ d8000000
str r3, [r0]
#endif
mov pc, lr
.ltorg
/*
* 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).
*/
.type __error_p, %function
__error_p:
#ifdef CONFIG_DEBUG_LL
adr r0, str_p1
bl printascii
b __error
str_p1: .asciz "\nError: unrecognized/unsupported processor variant.\n"
.align
#endif
.type __error_a, %function
__error_a:
#ifdef CONFIG_DEBUG_LL
mov r4, r1 @ preserve machine ID
adr r0, str_a1
bl printascii
mov r0, r4
bl printhex8
adr r0, str_a2
bl printascii
adr r3, 3f
ldmia r3, {r4, r5, r6} @ get machine desc list
sub r4, r3, r4 @ get offset between virt&phys
add r5, r5, r4 @ convert virt addresses to
add r6, r6, r4 @ physical address space
1: ldr r0, [r5, #MACHINFO_TYPE] @ get machine type
bl printhex8
mov r0, #'\t'
bl printch
ldr r0, [r5, #MACHINFO_NAME] @ get machine name
add r0, r0, r4
bl printascii
mov r0, #'\n'
bl printch
add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
cmp r5, r6
blo 1b
adr r0, str_a3
bl printascii
b __error
str_a1: .asciz "\nError: unrecognized/unsupported machine ID (r1 = 0x"
str_a2: .asciz ").\n\nAvailable machine support:\n\nID (hex)\tNAME\n"
str_a3: .asciz "\nPlease check your kernel config and/or bootloader.\n"
.align
#endif
.type __error, %function
__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
/*
* 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.
*
* Returns:
* r3, r4, r6 corrupted
* r5 = proc_info pointer in physical address space
* r9 = cpuid
*/
.type __lookup_processor_type, %function
__lookup_processor_type:
adr r3, 3f
ldmda r3, {r5, r6, r9}
sub r3, r3, r9 @ get offset between virt&phys
add r5, r5, r3 @ convert virt addresses to
add r6, r6, r3 @ physical address space
mrc p15, 0, r9, c0, c0 @ get processor id
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: mov pc, lr
/*
* This provides a C-API version of the above function.
*/
ENTRY(lookup_processor_type)
stmfd sp!, {r4 - r6, r9, lr}
bl __lookup_processor_type
mov r0, r5
ldmfd sp!, {r4 - r6, r9, pc}
/*
* Look in include/asm-arm/procinfo.h and arch/arm/kernel/arch.[ch] for
* more information about the __proc_info and __arch_info structures.
*/
.long __proc_info_begin
.long __proc_info_end
3: .long .
.long __arch_info_begin
.long __arch_info_end
/*
* Lookup machine architecture in the linker-build list of architectures.
* Note that we can't use the absolute addresses for the __arch_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.
*
* r1 = machine architecture number
* Returns:
* r3, r4, r6 corrupted
* r5 = mach_info pointer in physical address space
*/
.type __lookup_machine_type, %function
__lookup_machine_type:
adr r3, 3b
ldmia r3, {r4, r5, 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: ldr r3, [r5, #MACHINFO_TYPE] @ get machine type
teq r3, r1 @ matches loader number?
beq 2f @ found
add r5, r5, #SIZEOF_MACHINE_DESC @ next machine_desc
cmp r5, r6
blo 1b
mov r5, #0 @ unknown machine
2: mov pc, lr
/*
* This provides a C-API version of the above function.
*/
ENTRY(lookup_machine_type)
stmfd sp!, {r4 - r6, lr}
mov r1, r0
bl __lookup_machine_type
mov r0, r5
ldmfd sp!, {r4 - r6, pc}
