1/* 2 * arch/v850/kernel/head.S -- Lowest-level startup code 3 * 4 * Copyright (C) 2001,02,03 NEC Electronics Corporation 5 * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org> 6 * 7 * This file is subject to the terms and conditions of the GNU General 8 * Public License. See the file COPYING in the main directory of this 9 * archive for more details. 10 * 11 * Written by Miles Bader <miles@gnu.org> 12 */ 13 14#include <asm/clinkage.h> 15#include <asm/current.h> 16#include <asm/entry.h> 17#include <asm/thread_info.h> 18#include <asm/irq.h> 19 20 21/* Make a slightly more convenient alias for C_SYMBOL_NAME. */ 22#define CSYM C_SYMBOL_NAME 23 24 25 .text 26 27 // Define `mach_early_init' as a weak symbol 28 .global CSYM(mach_early_init) 29 .weak CSYM(mach_early_init) 30 31C_ENTRY(start): 32 // Make sure interrupts are turned off, just in case 33 di 34 35#ifdef CONFIG_RESET_GUARD 36 // See if we got here via an unexpected reset 37 ld.w RESET_GUARD, r19 // Check current value of reset guard 38 mov RESET_GUARD_ACTIVE, r20 39 cmp r19, r20 40 bne 1f // Guard was not active 41 42 // If we get here, the reset guard was active. Load up some 43 // interesting values as arguments, and jump to the handler. 44 st.w r0, RESET_GUARD // Allow further resets to succeed 45 mov lp, r6 // Arg 0: return address 46 ld.b KM, r7 // Arg 1: kernel mode 47 mov sp, r9 // Arg 3: stack pointer 48 ld.w KSP, r19 // maybe switch to kernel stack 49 cmp r7, r0 // see if already in kernel mode 50 cmov z, r19, sp, sp // and switch to kernel stack if not 51 GET_CURRENT_TASK(r8) // Arg 2: task pointer 52 jr CSYM(unexpected_reset) 53 541: st.w r20, RESET_GUARD // Turn on reset guard 55#endif /* CONFIG_RESET_GUARD */ 56 57 // Setup a temporary stack for doing pre-initialization function calls. 58 // 59 // We can't use the initial kernel stack, because (1) it may be 60 // located in memory we're not allowed to touch, and (2) since 61 // it's in the data segment, calling memcpy to initialize that 62 // area from ROM will overwrite memcpy's return address. 63 mov hilo(CSYM(_init_stack_end) - 4), sp 64 65 // See if there's a platform-specific early-initialization routine 66 // defined; it's a weak symbol, so it will have an address of zero if 67 // there's not. 68 mov hilo(CSYM(mach_early_init)), r6 69 cmp r6, r0 70 bz 3f 71 72 // There is one, so call it. If this function is written in C, it 73 // should be very careful -- the stack pointer is valid, but very 74 // little else is (e.g., bss is not zeroed yet, and initialized data 75 // hasn't been). 76 jarl 2f, lp // first figure out return address 772: add 3f - ., lp 78 jmp [r6] // do call 793: 80 81#ifdef CONFIG_ROM_KERNEL 82 // Copy the data area from ROM to RAM 83 mov hilo(CSYM(_rom_copy_dst_start)), r6 84 mov hilo(CSYM(_rom_copy_src_start)), r7 85 mov hilo(CSYM(_rom_copy_dst_end)), r8 86 sub r6, r8 87 jarl CSYM(memcpy), lp 88#endif 89 90 // Load the initial thread's stack, and current task pointer (in r16) 91 mov hilo(CSYM(init_thread_union)), r19 92 movea THREAD_SIZE, r19, sp 93 ld.w TI_TASK[r19], CURRENT_TASK 94 95#ifdef CONFIG_TIME_BOOTUP 96 /* This stuff must come after mach_early_init, because interrupts may 97 not work until after its been called. */ 98 jarl CSYM(highres_timer_reset), lp 99 jarl CSYM(highres_timer_start), lp 100#endif 101 102 // Kernel stack pointer save location 103 st.w sp, KSP 104 105 // Assert that we're in `kernel mode' 106 mov 1, r19 107 st.w r19, KM 108 109#ifdef CONFIG_ZERO_BSS 110 // Zero bss area, since we can't rely upon any loader to do so 111 mov hilo(CSYM(_sbss)), r6 112 mov r0, r7 113 mov hilo(CSYM(_ebss)), r8 114 sub r6, r8 115 jarl CSYM(memset), lp 116#endif 117 118 // What happens if the main kernel function returns (it shouldn't) 119 mov hilo(CSYM(machine_halt)), lp 120 121 // Start the linux kernel. We use an indirect jump to get extra 122 // range, because on some platforms this initial startup code 123 // (and the associated platform-specific code in mach_early_init) 124 // are located far away from the main kernel, e.g. so that they 125 // can initialize RAM first and copy the kernel or something. 126 mov hilo(CSYM(start_kernel)), r12 127 jmp [r12] 128C_END(start) 129