diff options
Diffstat (limited to 'arch/arm/kernel/head.S')
| -rw-r--r-- | arch/arm/kernel/head.S | 516 |
1 files changed, 516 insertions, 0 deletions
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S new file mode 100644 index 00000000000..171b3e811c7 --- /dev/null +++ b/arch/arm/kernel/head.S @@ -0,0 +1,516 @@ +/* + * 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} |