一、定義 [cpp] #define MACHINE_START(_type,_name) \ //板類型,板名字 static const struct machine_desc __mach_desc_##_type \ __used \ __attribute__((__section__(".arch.info.init"))) = { \ .nr = MACH_TYPE_##_type, \ .name = _name, #define MACHINE_END \ }; MACHINE_START和MACHINE_END框起了一個machine_desc結構體的聲明並根據MACHINE_START宏的參數初始化其.nr和.name成員 並將該結構體標記編譯到.arch.info.init段 在MACHINE_START和MACHINE_END宏之間可以初始化machine_desc結構體的剩余成員 machine_desc結構體的定義 [cpp] struct machine_desc { unsigned int nr; /* architecture number 編號 */ const char *name; /* architecture name 名字 */ unsigned long boot_params; /* tagged list */ unsigned int nr_irqs; /* number of IRQs 中斷數 */ unsigned int video_start; /* start of video RAM */ unsigned int video_end; /* end of video RAM */ unsigned int reserve_lp0 :1; /* never has lp0 */ unsigned int reserve_lp1 :1; /* never has lp1 */ unsigned int reserve_lp2 :1; /* never has lp2 */ unsigned int soft_reboot :1; /* soft reboot */ void (*fixup)(struct machine_desc *,struct tag *, char **,struct meminfo *); void (*reserve)(void); /* reserve mem blocks */ void (*map_io)(void); /* IO mapping function io映射函數 */ void (*init_irq)(void); /* 中斷初始化函數 */ struct sys_timer *timer; /* system tick timer 滴答定時器 */ void (*init_machine)(void); /* 初始化函數 */ }; 使用例子: [cpp] MACHINE_START(SMDKC110, "SMDKC110") /* Maintainer: Kukjin Kim <[email protected]> */ .boot_params = S5P_PA_SDRAM + 0x100, .init_irq = s5pv210_init_irq, .map_io = smdkc110_map_io, .init_machine = smdkc110_machine_init, .timer = &s3c24xx_timer, MACHINE_END 這裡smdkc110_machine_init就是對應的板級初始化函數,s5pv210_init_irq就是板級中斷初始化函數,smdkc110_map_io就是板級io初始化函數... 二、調用關系 MACHINE_START宏將machine_desc標記編譯到.arch.info.init段,而/arch/arm/kernel/vmlinux.lds中 [cpp] __arch_info_begin = .; *(.arch.info.init) __arch_info_end = .; 在linux啟動函數start_kernel中調用了setup_arch(&command_line); [cpp] void __init setup_arch(char **cmdline_p) { struct tag *tags = (struct tag *)&init_tags; struct machine_desc *mdesc; //聲明了一個machine_desc結構體指針 char *from = default_command_line; init_tags.mem.start = PHYS_OFFSET; unwind_init(); setup_processor(); mdesc = setup_machine(machine_arch_type); //0根據machine_arch_type獲取machine_desc machine_name = mdesc->name; //設置名字 if (mdesc->soft_reboot) //需要軟重啟? reboot_setup("s"); if (__atags_pointer) tags = phys_to_virt(__atags_pointer); else if (mdesc->boot_params) { //處理啟動參數 #ifdef CONFIG_MMU if (mdesc->boot_params < PHYS_OFFSET || mdesc->boot_params >= PHYS_OFFSET + SZ_1M) { printk(KERN_WARNING"Default boot params at physical 0x%08lx out of reach\n",mdesc->boot_params); } else #endif { tags = phys_to_virt(mdesc->boot_params); } } #if defined(CONFIG_DEPRECATED_PARAM_STRUCT) if (tags->hdr.tag != ATAG_CORE) convert_to_tag_list(tags); #endif if (tags->hdr.tag != ATAG_CORE) tags = (struct tag *)&init_tags; if (mdesc->fixup) //若存在fixup方法則調用其方法 mdesc->fixup(mdesc, tags, &from, &meminfo); if (tags->hdr.tag == ATAG_CORE) { if (meminfo.nr_banks != 0) squash_mem_tags(tags); save_atags(tags); parse_tags(tags); } init_mm.start_code = (unsigned long) _text; init_mm.end_code = (unsigned long) _etext; init_mm.end_data = (unsigned long) _edata; init_mm.brk = (unsigned long) _end; /* parse_early_param needs a boot_command_line */ strlcpy(boot_command_line, from, COMMAND_LINE_SIZE); /* populate cmd_line too for later use, preserving boot_command_line */ strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE); *cmdline_p = cmd_line; parse_early_param(); arm_memblock_init(&meminfo, mdesc); //這裡可能會調用reserve方法 paging_init(mdesc); //->devicemaps_init(mdesc)->map_io方法 request_standard_resources(&meminfo, mdesc); //這裡可能會調用video_start方法 #ifdef CONFIG_SMP if (is_smp()) smp_init_cpus(); #endif reserve_crashkernel(); cpu_init(); tcm_init(); arch_nr_irqs = mdesc->nr_irqs; //1設置全局變量 中斷個數 init_arch_irq = mdesc->init_irq; //2設置全局變量 中斷初始化函數 system_timer = mdesc->timer; //3設置全局變量 sys_timer結構體 init_machine = mdesc->init_machine; //4設置全局變量 板級初始化函數 #ifdef CONFIG_VT #if defined(CONFIG_VGA_CONSOLE) conswitchp = &vga_con; #elif defined(CONFIG_DUMMY_CONSOLE) conswitchp = &dummy_con; #endif #endif early_trap_init(); } 0. [cpp] static struct machine_desc * __init setup_machine(unsigned int nr) { extern struct machine_desc __arch_info_begin[], __arch_info_end[]; struct machine_desc *p; for (p = __arch_info_begin; p < __arch_info_end; p++)//遍歷__arch_info_begin和__arch_info_end之間的machine_desc結構體 if (nr == p->nr) { //找到對應的板 printk("Machine: %s\n", p->name);//打印板級信息 return p; } early_print("\n" "Error: unrecognized/unsupported machine ID (r1 = 0x%08x).\n\n" "Available machine support:\n\nID (hex)\tNAME\n", nr); for (p = __arch_info_begin; p < __arch_info_end; p++) early_print("%08x\t%s\n", p->nr, p->name); early_print("\nPlease check your kernel config and/or bootloader.\n"); while (true) /* can't use cpu_relax() here as it may require MMU setup */; } 1.中斷個數 start_kernel->early_irq_init->arch_probe_nr_irqs函數中nr_irqs = arch_nr_irqs ? arch_nr_irqs : NR_IRQS;設置全局nr_irqs變量 2.中斷初始化函數 start_kernel->init_IRQ->init_arch_irq() 3.sys_timer結構體 start_kernel->time_init()調用system_timer->init()方法既sys_timer->init() 4.板級初始化函數 [cpp] static void (*init_machine)(void) __initdata; static int __init customize_machine(void) { /* customizes platform devices, or adds new ones */ if (init_machine)//全局函數init_machine存在 init_machine();//則調用,既mdesc->init_machine() return 0; } arch_initcall(customize_machine);//用arch_initcall修飾customize_machine函數 arch_iniitcall函數在/include/linux/init.h中定義 [cpp] #define arch_initcall(fn) __define_initcall("3",fn,3) __define_initcall的定義 [cpp] #define __define_initcall(level,fn,id) \ static initcall_t __initcall_##fn##id __used \ __attribute__((__section__(".initcall" level ".init"))) = fn 展開就是static initcall_t __initcall_customize_machine3 __used __attribute__((__section__(".initcall3.init")))=customize_machine 在vmlinux.lds中 [cpp] __initcall_start = .; *(.initcallearly.init) __early_initcall_end = .; *(.initcall0.init) *(.initcall0s.init) *(.initcall1.init) *(.initcall1s.init) *(.initcall2.init) *(.initcall2s.init) *(.initcall3.init) *(.initcall3s.init) *(.initcall4.init) *(.initcall4s.init) *(.initcall5.init) *(.initcall5s.init) *(.initcallrootfs.init) *(.initcall6.init) *(.initcall6s.init) *(.initcall7.init) *(.initcall7s.init) __initcall_end = .; 標注為.initcall3.init的函數編譯進__initcall_start和__initcall_end框起的section中 而在系統啟動的時候 start_kernel->rest_init()->kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);創建了kernel線程 kernel_init->do_pre_smp static void __init do_pre_smp_initcalls(void) { initcall_t *fn; for (fn = __initcall_start; fn < __early_initcall_end; fn++) do_one_initcall(*fn); } 該函數遍歷__initcall_start和__early_initcall_end中的函數,並調用do_one_initcall [cpp] int __init_or_module do_one_initcall(initcall_t fn) { int count = preempt_count(); int ret; if (initcall_debug) ret = do_one_initcall_debug(fn); else ret = fn();//執行了fn函數也就是customize_machine msgbuf[0] = 0; if (ret && ret != -ENODEV && initcall_debug) sprintf(msgbuf, "error code %d ", ret); if (preempt_count() != count) { strlcat(msgbuf, "preemption imbalance ", sizeof(msgbuf)); preempt_count() = count; } if (irqs_disabled()) { strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf)); local_irq_enable(); } if (msgbuf[0]) { printk("initcall %pF returned with %s\n", fn, msgbuf); } return ret; }
