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鍥?锛氫粠涓婄數鍒癇IOS
鎸変笅鐢垫簮寮€鍏崇殑閭ｄ釜鐪熷疄鐨勪汉灏辨槸Linux涓栫晫閲岀殑涓婂笣锛屼粬鍒涢€犱簡Linux涓栫晫鐨勪竴鍒囥€傚綋浠栨寜涓嬫満绠变笂鐨勭數婧愬紑鍏虫椂锛屼富鏉垮紑濮嬩緵鐢碉紝CPU涓婄殑Reset Pin琚媺楂橈紝杩欎細寮曡捣CPU鐨勪竴绯诲垪鍔ㄤ綔锛岃繖浜涘姩浣滄槸鑺墖璁捐鏃跺氨鍐冲畾鐨勩€侰PU涓殑涓€浜涘瘎瀛樺櫒琚疆涓哄浐瀹氱殑鍊硷紝鍥犱负杩欎簺瀵勫瓨鍣ㄥ彲鑳藉湪鍚姩鐨勮繃绋嬩腑瑕佷娇鐢紝姣斿CS锛堜唬鐮佹瀵勫瓨鍣級鍜孍IP锛堟寚閽堟寚浠ゅ瘎瀛樺櫒锛夈€傝繖涓€姝ュ畬鎴愪箣鍚庯紝CPU灏卞彲寮€鎵ц鍦板潃涓?xfffffff0閲岀殑ROM涓殑绋嬪簭銆傝繖娈电▼搴忓氨鏄疊IOS(Basic Input Output System)銆?/p>
BIOS瀹屾垚涓嬮潰鐨勫姛鑳斤細
1.POST锛圥ower-On Self Test锛夛細椤惧悕鎬濆悕锛屽氨鏄煡鏌ユ湁浠€涔堣澶囷紝杩欎簺璁惧鏄笉鏄甯搞€傝鏄疌PU鏈堿dvanced Configuration and Power Interface(ACPI )鐨勬敮鎸侊紝涔熷湪杩欎釜鏃跺€欒繘琛屻€侫CPI鏄敤鏉ュ鐢垫簮杩涜绠＄悊鐨勶紝鐢ㄦ潵鑺傜數涔嬬被鐨勩€?/p>
2.鍒濆鍖栬澶囷細纭繚娌℃湁IRQ鍜孖O鍐茬獊銆?/p>
3.瀵绘壘OS/Bootloader銆傝繖涓€姝ュ悗闈㈢偣鍐嶇粏璇?/p>
鎴戜滑鍦˙IOS鐨勮缃彍鍗曢噷鑳藉璁剧疆浠庝綍澶勫惎鍔紝姣斿杞洏锛岀‖鐩橈紝鍏夐┍…BIOS浼氭寜鎴戜滑璁惧畾鐨勯『搴忔悳绱S銆?/p>
4.鎶夿ootloader澶嶅埗鍒癛AM閲岋紙鍦板潃涓?×00007c00锛夛紝鐒跺悗閭ｄ釜鍦板潃寮€濮嬫墽琛屻€?/p>
浠€涔堟槸Bootloader锛?/em>
鐜板湪锛屾垜浠彧瑕佸叧蹇冪殑鏄細bootloader浼氭壘鍒癘S锛屾妸OS鍐呮牳COPY鍒癛AM涓€?/em>
鍥?锛歜oot loader鐨勫姞杞?/p>
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Bootloader浼氭妸OS鐨勫唴鏍告槧鍍忓鍒跺埌RAM涓€?/p>
1. 璋冪敤BIOS浠ユ樉绀衡€淟oading Image鈥濈殑娑堟伅銆?/p>
2. 璋冪敤BIOS锛屾妸鍐呮牳鏄犲儚鐨勫墠512瀛楄妭澶嶅埗鍒?×00090000锛宻etup()鍑芥暟鍦?×00090200銆?/p>
3. 璋冪敤BIOS锛屾妸鍓╀笅鐨勫唴鏍告槧鍍忓姞杞藉埌0×00010000锛堝皬鍐呮牳zImage锛夋垨0×00100000锛堝ぇ鍐呮牳bzImage锛?/p>
4. 璺冲埌setup()寮€濮嬫墽琛屻€?/p>
setup()鐢ㄦ潵鍒濆鍖栬澶囥€傝櫧鐒禕IOS宸茬粡鍋氫簡涓€浜涘垵濮嬪寲鐨勫伐浣滐紝浣嗘槸Linux鍏充笉渚濊禆浜庝粬銆俿etup()浼氬垵濮嬪寲閿洏锛孎PU绛夎澶囷紝骞惰缃竴浜涘瘎瀛樺櫒銆傚湪Setup()鐨勬渶鍚庯紝浼氳皟鐢╯tartup_32()銆?/p>
startup_32() Linux閲屾湁涓や釜startup_32()銆?/p>
棣栧厛浼氭墽琛岀殑鏄?em>arch/i386/boot/compressed/head.SBootloader鐨勫伐浣?/h3>
Setup()鐨勫伐浣?/h3>
绗簩涓猻tartup_32()鏄湪arch/i386/kernel/head.S鐨勩€傝繖涓猻tartup_32()鐨勫伐浣滃氨鏄负Linux鐨勭涓€涓繘绋嬶紙灏辨槸Mr. Process鐨勭鍏堬級璁剧疆鐢熷瓨鐜銆傛渶鍚庤烦鍒皊tart_kernel()涓幓銆?/p>
鍦║nderstanding the Linux Kernel 3rd 涓殑鎻忚堪濡備笅
- Initializes the segmentation registers with their final values.
- Fills the bss segment of the kernel (see the section “Program Segments and Process Memory Regions” in Chapter 20) with zeros.
- Initializes the provisional kernel Page Tables contained in swapper_pg_dir and pg0 to identically map the linear addresses to the same physical addresses, as explained in the section “Kernel Page Tables” in Chapter 2.
- Stores the address of the Page Global Directory in the cr3 register, and enables paging by setting the PG bit in the cr0 register.
- Sets up the Kernel Mode stack for process 0 (see the section “Kernel Threads” in Chapter 3).
- Once again, the function clears all bits in the eflags register.
- Invokes setup_idt( ) to fill the IDT with null interrupt handlers (see the section “Preliminary Initialization of the IDT” in Chapter 4).
- Puts the system parameters obtained from the BIOS and the parameters passed to the operating system into the first page frame (see the section “Physical Memory Layout” in Chapter 2).
- Identifies the model of the processor.
10.聽 Loads the gdtr and idtr registers with the addresses of the GDT and IDT tables.
11.聽 Jumps to the start_kernel( ) function.
start_kernel()鐨勫伐浣?/h3>
瀹屾垚鎵€鏈夌粍浠剁殑鍒濆鍖栧伐浣溿€?/p>
Understanding the Linux Kernel瀵硅繖涓€娈靛伐浣滅殑鎻忚堪濡備笅锛?/p>
篓聽聽聽 The scheduler is initialized by invoking the sched_init( ) function (see Chapter 7).
篓聽聽聽 The memory zones are initialized by invoking the build_all_zonelists( ) function (see the section “Memory Zones” in Chapter 8).
篓聽聽聽 The Buddy system allocators are initialized by invoking the page_alloc_init( ) and mem_init( ) functions (see the section “The Buddy System Algorithm” in Chapter 8).
篓聽聽聽 The final initialization of the IDT is performed by invoking trap_init( ) (see the section “Exception Handling” in Chapter 4) and init_IRQ( ) (see the section “IRQ data structures” in Chapter 4).
篓聽聽聽 The TASKLET_SOFTIRQ and HI_SOFTIRQ are initialized by invoking the softirq_init( ) function (see the section “Softirqs” in Chapter 4).
篓聽聽聽 The system date and time are initialized by the time_init( ) function (see the section “The Linux Timekeeping Architecture” in Chapter 6).
篓聽聽聽 The slab allocator is initialized by the kmem_cache_init( ) function (see the section “General and Specific Caches” in Chapter 8).
篓聽聽聽 The speed of the CPU clock is determined by invoking the calibrate_delay( ) function (see the section “Delay Functions” in Chapter 6).
篓聽聽聽 The kernel thread for process 1 is created by invoking the kernel_thread( ) function. In turn, this kernel thread creates the other kernel threads and executes the /sbin/init program, as described in the section “Kernel Threads” in Chapter 3.
浠ヤ笂鍑犱釜鍑芥暟鐨勬墽琛岃繃绋嬪涓嬪浘锛?/p>
鍥?锛氬惎鍔ㄥ嚱鏁扮殑鎵ц杩囩▼
绗簩涓猻tartup_32()鍜宻tart_kernel()鎻ず浜哃inux涓€鐢熺殑鐪熻皼銆備粠杩欓噷闈㈠挶鐪嬪埌浜哅r. Process锛堜竴涓櫘閫氱殑杩涚▼锛夋墍鎷ユ湁鐨勪竴鍒囨槸鎬庝箞寰楀埌鐨勩€傚紕娓呮浜嗚繖浜涳紝涔熷氨寮勬竻妤氫簡Linux銆俁eally娓呮銆?/p>
BTW锛屾垜鍋氱殑鍥炬€庝箞閭ｄ箞濂界湅~缇庢劅澶╃敓鍦ㄩ偅閲岋紝浣犳尅閮芥尅涓嶄綇锛屾€庝箞鎼炴€庝箞濂界湅鍔犱笓涓氾紒
