/* * linux/arch/arm/kernel/head.S * * Copyright (C) 1994-2002 Russell King * Copyright (c) 2003 ARM Limited * All Rights Reserved * * 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 #include #include #include #include #include #include #include #include #include #include #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 + THREAD_START_SP @ 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 #if defined(CONFIG_SMP) .type secondary_startup, #function ENTRY(secondary_startup) /* * Common entry point for secondary CPUs. * * Ensure that we're in SVC mode, and IRQs are disabled. Lookup * the processor type - there is no need to check the machine type * as it has already been validated by the primary processor. */ msr cpsr_c, #PSR_F_BIT | PSR_I_BIT | MODE_SVC bl __lookup_processor_type movs r10, r5 @ invalid processor? moveq r0, #'p' @ yes, error 'p' beq __error /* * Use the page tables supplied from __cpu_up. */ adr r4, __secondary_data ldmia r4, {r5, r6, r13} @ address to jump to after sub r4, r4, r5 @ mmu has been enabled ldr r4, [r6, r4] @ get secondary_data.pgdir adr lr, __enable_mmu @ return address add pc, r10, #12 @ initialise processor @ (return control reg) /* * r6 = &secondary_data */ ENTRY(__secondary_switched) ldr sp, [r6, #4] @ get secondary_data.stack mov fp, #0 b secondary_start_kernel .type __secondary_data, %object __secondary_data: .long . .long secondary_data .long __secondary_switched #endif /* defined(CONFIG_SMP) */ /* * 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 #ifdef CONFIG_DEBUG_LL bic r7, r7, #0x0c @ turn off cacheable @ and bufferable bits /* * 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, #0xff000000 >> 18 orr r3, r7, #0x7c000000 str r3, [r0] 1: #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, #0x02000000 >> 18 orr r3, r7, #0x02000000 str r3, [r0] add r0, r4, #0xd8000000 >> 18 str r3, [r0] #endif #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}