1 啓動代碼分析(for MIPS): 2 packages/hal/mips/arch/v2_0/src/vector.S 3 FUNC_START(reset_vector) //reset向量,地址爲0xbfc00000,內核由此地址啓動 4 5 #ifndef CYG_HAL_STARTUP_RAM 6 # if defined(CYGPKG_HAL_RESET_VECTOR_FIRST_CODE) 7 hal_reset_vector_first_code 8 # endif 9 # if defined(CYGPKG_HAL_EARLY_INIT) 10 hal_early_init 11 # endif 12 # Decide whether this is an NMI, cold or warm boot. 13 14 mfc0 k0,status # get status reg //處理NMI位,MIPS R3000中不涉及NMI操作 15 lui k1,0x0008 # isolate NMI bit 16 and k1,k1,k0 17 beqz k1,1f # skip if zero 18 nop 19 20 lar k1,__nmi_entry # jump to ROM nmi code 21 jalr k1 22 nop 23 1: 24 lui k1,0x0010 # isolate soft reset bit 25 and k1,k1,k0 26 beqz k1,2f # skip if zero 27 nop 28 29 lar k1,__warm_start # jump to ROM warm_start code //__warm_start代碼用於調試,可選 30 jr k1 31 nop 32 2: 33 la k0,INITIAL_CONFIG0 # Set up config0 register //初始化config0寄存器,MIPS R3000沒有這個寄存器 34 mtc0 k0,config0 # to disable cache //禁用cache 35 #endif 36 lar v0,_start # jump to start //加載_start標號地址(此處的lar指令MIPS R3000不支持) 37 #ifdef CYGARC_START_FUNC_UNCACHED 38 CYGARC_ADDRESS_REG_UNCACHED(v0) 39 #endif 40 41 jr v0 //跳轉到_start處 42 nop # (delay slot) 43 44 FUNC_END(reset_vector) 45 46 FUNC_START(_start) //_start函數,做大部分初始化工作,具體代碼在_start之後分析 47 48 # Initialize hardware 49 hal_cpu_init //packages/hal/mips/arch/v2_0/include/arch.inc 初始化watchdog寄存器,cause寄存器清零初始化status寄存器初始化config0寄存器(MIPS R3000沒有config0寄存器) 50 hal_diag_init //診斷支持初始化,如果未定義CYGPKG_HAL_MIPS_DIAG_DEFINED,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義一個空宏,如果定義了則實現依賴於特定平臺,如packages/hal/mips/tx39/v2_0/src/hal_duag.c 51 hal_mmu_init //初始化mmu,如果未定義CYGPKG_HAL_MIPS_MMU_DEFINED,則表示該variant不支持mmu,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義一個空宏,如果定義了則實現依賴於特定平臺,如packages/hal/mips/vrc437x/v2_0/include/platform.inc 52 hal_fpu_init //packages/hal/mips/arch/v2_0/include/arch.inc,初始化fpu 53 hal_memc_init //初始化memory控制器,如果未定義CYGPKG_HAL_MIPS_MEMC_DEFINED,則表示該platform沒有memory控制器,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義一個空宏,如果定義了則實現依賴於特定平臺,如packages/hal/mips/tx39/v2_0/include/variant.inc,該宏也可能在platform.inc中實現 54 hal_intc_init //初始化中斷控制器,如果未定義CYGPKG_HAL_MIPS_INTC_INIT_DEFINED,則表示該platform沒有中斷控制器,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義該宏,在status寄存器中禁用所有中斷,如果定義了則實現依賴於特定平臺,如packages/hal/mips/tx39/v2_0/include/variant.inc,該宏也可能在platform.inc中實現 55 hal_cache_init //初始化cache,如果未定義CYGPKG_HAL_MIPS_CACHE_DEFINED,則表示該variant的cache是標準cache,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義該宏,使用config寄存器初始化cache,如果定義了則實現依賴於特定variant,如packages/hal/mips/tx49/v2_0/include/variant.inc 56 hal_timer_init //初始化timer,如果未定義CYGPKG_HAL_MIPS_TIMER_DEFINED,則表示該platform沒有timer,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義一個空宏,如果定義了則實現依賴於特定platform 57 58 #ifdef CYGARC_START_FUNC_UNCACHED 59 # switch to cached execution address if necessary 60 # assumption is that hal_cache_init makes this safe 61 lar v0,1f 62 jr v0 63 nop 64 1: 65 #endif 66 67 # Load Global Pointer register. 68 la gp,_gp //加載gp寄存器 69 70 # load initial stack pointer //設置stack指針,給c代碼使用,通常interrupt stack用於此目的 71 la a0,__interrupt_stack //定義於vector.S,定義如下: 72 .balign 16 73 .global cyg_interrupt_stack 74 cyg_interrupt_stack: 75 __interrupt_stack: 76 .long 0,0,0,0,0,0,0,0 77 move sp,a0 //加載stack指針 78 79 hal_mon_init //初始化monitor,用於安裝中斷向量,如果未定義CYGPKG_HAL_MIPS_MON_DEFINED,則表示該platform未實現monitor,則在packages/hal/mips/arch/v2_0/include/arch.inc中定義一個空宏,如果定義了則實現依賴於特定platform,如packages/hal/mips/rm7000/v2_0/include/platform.inc,一般會調用hal_vectors_init() 80 #ifdef CYG_HAL_STARTUP_ROM //如果eCos從ROM啓動,則拷貝data段到RAM中 81 # Copy data from ROM to RAM 82 83 .extern hal_copy_data 84 jal hal_copy_data //packages/hal/mips/arch/v2_0/src/hal_misc.c 85 nop 86 87 #endif 88 89 # Zero BSS //bss段清零 90 91 .extern hal_zero_bss 92 jal hal_zero_bss //packages/hal/mips/arch/v2_0/src/vectors.S 93 nop 94 95 # Call variant and platform HAL 96 # initialization routines. 97 98 .extern hal_variant_init 99 jal hal_variant_init //variant初始化,packages/hal/mips/tx39/v2_0/src/var_misc.c,大部分爲空函數,也可在此處進一步初始化中斷控制器,PCI橋,IO設備,啓用cache等 100 nop 101 102 .extern hal_platform_init 103 jal hal_platform_init //platform初始化,packages/hal/mips/vrc437x/v2_0/src/plf_misc.c,可以不實現,也可在此處進一步初始化中斷控制器,PCI橋,IO設備,啓用cache等 104 nop 105 106 # Call constructors 107 .extern cyg_hal_invoke_constructors 108 jal cyg_hal_invoke_constructors //建立構造函數表,運行靜態構造函數(packages/hal/mips/arch/v2_0/src/hal_misc.c) 109 nop 110 111 #if defined(CYGDBG_HAL_DEBUG_GDB_INCLUDE_STUBS) //如果實現了GDB stub,則初始化 112 .extern initialize_stub 113 jal initialize_stub //初始化GDB stub,packages/hal/common/v2_0/src/generic-stub.c 114 nop 115 #endif 116 #if defined(CYGDBG_HAL_MIPS_DEBUG_GDB_CTRLC_SUPPORT) //如果GDB需要ctrl-c支持,則初始化 117 .extern hal_ctrlc_isr_init 118 jal hal_ctrlc_isr_init //初始化GDB ctrl-c支持,實現依賴於platform,如packages/hal/mips/vrc437x/v2_0/src/plf_misc.c 119 nop 120 #endif 121 # Call cyg_start 122 .extern cyg_start 123 j cyg_start //調用cyg_start()進入主循環,kernel開始運行,永不返回,cyg_start()由應用程序自己實現,可在此處調用_bsp_init()初始化設備驅動,一般實現如下: 124 void 125 cyg_start(void) 126 { 127 cyg_thread_create(10, // Priority - just a number 128 (cyg_thread_entry_t*)console_test, // entry 129 0, // 130 "console_thread", // Name 131 &stack[0], // Stack 132 STACK_SIZE, // Size 133 &thread_handle, // Handle 134 &thread_data // Thread data structure 135 ); 136 cyg_thread_resume(thread_handle); 137 cyg_scheduler_start(); 138 } 139 lui ra,0 140 141 FUNC_END(_start )
eCos學習筆記之啓動代碼分析
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