{"id":341,"date":"2018-03-14T09:41:40","date_gmt":"2018-03-14T01:41:40","guid":{"rendered":"http:\/\/www.max-shu.com\/blog\/?p=341"},"modified":"2018-03-14T09:41:40","modified_gmt":"2018-03-14T01:41:40","slug":"linux%e7%9a%84arch-arm-kernel-head-s-2","status":"publish","type":"post","link":"http:\/\/www.max-shu.com\/blog\/?p=341","title":{"rendered":"linux\u7684arch\/arm\/kernel\/head.S"},"content":{"rendered":"
<\/div>\n
\u8981\u6ce8\u610f\u548c\u201cboot\/compressed\/head.S\u201d\u7684\u533a\u522b\u3002<\/span><\/div>\n
<\/div>\n
\u8fdb\u5165\u8fd9\u4e2a\u4ee3\u7801\u65f6\uff0c\u4ece\u89e3\u538b\u7f29\u4ee3\u7801\u4f20\u5165\u7684\u53c2\u6570\uff1ar0: \u56fa\u5b9a0\uff0cr1\uff1a\u67b6\u6784id\uff0cr2\uff1a\u542f\u52a8\u53c2\u6570<\/div>\n
<\/div>\n
\/*
\n* Kernel startup entry point.
\n* —————————
\n*
\n* This is normally called from the decompressor code.\u00a0 The requirements
\n* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
\n* r1 = machine nr, r2 = atags pointer.
\n*
\n* This code is mostly position independent, so if you link the kernel at
\n* 0xc0008000, you call this at __pa(0xc0008000).
\n*
\n* See linux\/arch\/arm\/tools\/mach-types for the complete list of machine
\n* numbers for r1.
\n*
\n* We’re trying to keep crap to a minimum; DO NOT add any machine specific
\n* crap here – that’s what the boot loader (or in extreme, well justified
\n* circumstances, zImage) is for.
\n*\/
\n.section “.text.head”, “ax”
\nENTRY(stext)
\nmsr\u00a0\u00a0\u00a0\u00a0 cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode \u00a0 \/*\u8fd9\u91cc\u662f\u5185\u6838\u771f\u6b63\u7684\u7b2c\u4e00\u6761\u6307\u4ee4\uff0c\u786e\u4fddMMU\u4e0d\u5de5\u4f5c\uff0c\u6570\u636ecache\u4e0d\u5de5\u4f5c\uff0c\u6307\u4ee4cache\u4e0d\u5173\u5fc3\uff0c\u5fc5\u987b\u662fSVC\u6a21\u5f0f\uff0cIRQ\u5173\u95ed*\/
\n@ and irqs disabled
\nmrc\u00a0\u00a0\u00a0\u00a0 p15, 0, r9, c0, c0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get processor id \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u5f97\u5230\u5904\u7406\u673aID*\/
\nbl\u00a0\u00a0\u00a0\u00a0 __lookup_processor_type\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r5=procinfo r9=cpuid \/*\u5f97\u5230\u5904\u7406\u673a\u7c7b\u578b\u4fe1\u606f\uff0c\u8fd4\u56der5\u6307\u5411\u7ed3\u6784\uff0c\u89c1head-common.S*\/<\/div>\n
\u00a0\u00a0\u00a0\u00a0 movs\u00a0\u00a0\u00a0\u00a0 r10, r5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ invalid processor (r5=0)? \u00a0 \u00a0 \u00a0\/*r5\u4e3a0\u8868\u793a\u6ca1\u627e\u5230*\/
\nbeq\u00a0\u00a0\u00a0\u00a0 __error_p\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ yes, error ‘p’ \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8f93\u51fa\u9519\u8bef\uff0c\u89c1head-common.S*\/<\/div>\n
\u00a0\u00a0\u00a0\u00a0 bl\u00a0\u00a0\u00a0\u00a0 __lookup_machine_type\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r5=machinfo \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u627e\u5230\u673a\u5668\u4fe1\u606f\uff0c\u89c1head-common.S*\/<\/div>\n
\u00a0\u00a0\u00a0\u00a0 movs\u00a0\u00a0\u00a0\u00a0 r8, r5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ invalid machine (r5=0)?
\nbeq\u00a0\u00a0\u00a0\u00a0 __error_a\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ yes, error ‘a’ \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8f93\u51fa\u9519\u8bef\uff0c\u89c1head-common.S*\/
\nbl\u00a0\u00a0\u00a0\u00a0 __vet_atags \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u5224\u65ad\u53c2\u6570\u6709\u6548\u6027\uff0c\u89c1head-common.S*\/
\nbl\u00a0\u00a0\u00a0\u00a0 __create_page_tables \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u5efa\u7acb\u9875\u8868\uff0c\u89c1\u4e0b\u9762*\/<\/p>\n

\/*
\n* The following calls CPU specific code in a position independent
\n* manner.\u00a0 See arch\/arm\/mm\/proc-*.S for details.\u00a0 r10 = base of
\n* xxx_proc_info structure selected by __lookup_machine_type
\n* above.\u00a0 On return, the CPU will be ready for the MMU to be
\n* turned on, and r0 will hold the CPU control register value.
\n*\/
\nldr\u00a0\u00a0\u00a0\u00a0 r13, __switch_data\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ address to jump to after \u00a0\/*r13\u8bbe\u7f6e\u4e3a__switch_data\uff0c\u89c1head-common.S\uff0c\u5728MMU\u4f7f\u80fd\u540e\u4f1a\u4f7f\u7528\u5230*\/
\n@ mmu has been enabled
\nadr\u00a0\u00a0\u00a0\u00a0 lr, __enable_mmu\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ return (PIC) address \u00a0 \u00a0 \u00a0 \u00a0\/*\u8bbe\u7f6e\u8fd4\u56de\u5730\u5740\u4e3a__enable_mmu\uff0c\u6267\u884c\u5b8c\u4e0b\u9762\u51fd\u6570\u540e\u5c31\u4f1a\u8df3\u5230__enable_mmu\u6267\u884c*\/
\nadd\u00a0\u00a0\u00a0\u00a0 pc, r10, #PROCINFO_INITFUNC \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*r10\u4e0a\u9762\u7f6e\u4e3a\u4e86\u5904\u7406\u5668\u7ed3\u6784proc_info_list\uff08\u4ece__lookup_processor_type\u8fd9\u91cc\u77e5\u9053\uff0cProc_info_list\u5728__proc_info_begin\u5f00\u59cb\uff0c\u4ecevmlinux.lds.S\u77e5\u9053\uff0c\u5373\u662fproc.info.init\uff0c\u5b9a\u4e49\u5728proc-(arch).S\u91cc\u9762\uff09\u7684\u5730\u5740\uff0c\u8fd9\u91cc\u5c31\u4f1a\u8df3\u5230__cpu_flush\u5904\uff08\u4eceproc-(arch).S\u91cc\u9762\u770b\u5230\uff0c\u57fa\u672c\u90fd\u662f\u4e00\u6761\u8df3\u8f6c\u6307\u4ee4\uff0c\u5982\uff1ab\u00a0\u00a0\u00a0\u00a0 __v6_setup\uff0c\uff09\u6267\u884c\uff0c\u4ece__v6_setup\u6267\u884c\u5b8c\u540e\u4f1a\u4f7f\u7528\uff1amov\u00a0\u00a0\u00a0\u00a0 pc, lr\uff0c\u8df3\u8f6c\u5230\u4e0a\u9762\u8fd9\u6761\u6307\u4ee4\u6267\u884c\uff0c\u5373__eanble_mmu\u3002*\/<\/p><\/div>\n

ENDPROC(stext)<\/p>\n

#if defined(CONFIG_SMP)
\nENTRY(secondary_startup)
\n\/*
\n* Common entry point for secondary CPUs.
\n*
\n* Ensure that we’re in SVC mode, and IRQs are disabled.\u00a0 Lookup
\n* the processor type – there is no need to check the machine type
\n* as it has already been validated by the primary processor.
\n*\/
\nmsr\u00a0\u00a0\u00a0\u00a0 cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE
\nmrc\u00a0\u00a0\u00a0\u00a0 p15, 0, r9, c0, c0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get processor id
\nbl\u00a0\u00a0\u00a0\u00a0 __lookup_processor_type
\nmovs\u00a0\u00a0\u00a0\u00a0 r10, r5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ invalid processor?
\nmoveq\u00a0\u00a0\u00a0\u00a0 r0, #’p’\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ yes, error ‘p’
\nbeq\u00a0\u00a0\u00a0\u00a0 __error<\/p>\n

\/*
\n* Use the page tables supplied from\u00a0 __cpu_up.
\n*\/
\nadr\u00a0\u00a0\u00a0\u00a0 r4, __secondary_data
\nldmia\u00a0\u00a0\u00a0\u00a0 r4, {r5, r7, r13}\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ address to jump to after
\nsub\u00a0\u00a0\u00a0\u00a0 r4, r4, r5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ mmu has been enabled
\nldr\u00a0\u00a0\u00a0\u00a0 r4, [r7, r4]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get secondary_data.pgdir
\nadr\u00a0\u00a0\u00a0\u00a0 lr, __enable_mmu\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ return address
\nadd\u00a0\u00a0\u00a0\u00a0 pc, r10, #PROCINFO_INITFUNC\u00a0\u00a0\u00a0\u00a0 @ initialise processor
\n@ (return control reg)
\nENDPROC(secondary_startup)<\/p>\n

\/*
\n* r6\u00a0 = &secondary_data
\n*\/
\nENTRY(__secondary_switched)
\nldr\u00a0\u00a0\u00a0\u00a0 sp, [r7, #4]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get secondary_data.stack
\nmov\u00a0\u00a0\u00a0\u00a0 fp, #0
\nb\u00a0\u00a0\u00a0\u00a0 secondary_start_kernel
\nENDPROC(__secondary_switched)<\/p>\n

.type\u00a0\u00a0\u00a0\u00a0 __secondary_data, %object
\n__secondary_data:
\n.long\u00a0\u00a0\u00a0\u00a0 .
\n.long\u00a0\u00a0\u00a0\u00a0 secondary_data
\n.long\u00a0\u00a0\u00a0\u00a0 __secondary_switched
\n#endif \/* defined(CONFIG_SMP) *\/<\/p>\n

\/*
\n* Setup common bits before finally enabling the MMU.\u00a0 Essentially
\n* this is just loading the page table pointer and domain access
\n* registers.
\n*\/
\n__enable_mmu: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*Eable MMU\u4e4b\u524d\u7684\u6700\u540e\u6267\u884c\u4ee3\u7801\uff0c\u4e3a\u8fdb\u5165MMU\u505a\u51c6\u5907*\/
\n#ifdef CONFIG_ALIGNMENT_TRAP \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8bbe\u7f6e\u5730\u5740\u5bf9\u9f50\u9519\u8bef\u68c0\u6d4b*\/
\norr\u00a0\u00a0\u00a0\u00a0 r0, r0, #CR_A
\n#else
\nbic\u00a0\u00a0\u00a0\u00a0 r0, r0, #CR_A
\n#endif
\n#ifdef CONFIG_CPU_DCACHE_DISABLE
\nbic\u00a0\u00a0\u00a0\u00a0 r0, r0, #CR_C \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u7981\u6b62\u6570\u636ecache*\/
\n#endif
\n#ifdef CONFIG_CPU_BPREDICT_DISABLE
\nbic\u00a0\u00a0\u00a0\u00a0 r0, r0, #CR_Z
\n#endif
\n#ifdef CONFIG_CPU_ICACHE_DISABLE
\nbic\u00a0\u00a0\u00a0\u00a0 r0, r0, #CR_I \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u7981\u6b62\u6307\u4ee4cache*\/
\n#endif
\nmov\u00a0\u00a0\u00a0\u00a0 r5, #(domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \\
\ndomain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \\
\ndomain_val(DOMAIN_TABLE, DOMAIN_MANAGER) | \\
\ndomain_val(DOMAIN_IO, DOMAIN_CLIENT))
\nmcr\u00a0\u00a0\u00a0\u00a0 p15, 0, r5, c3, c0, 0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ load domain access register \u00a0\/*\u8bbe\u7f6e\u57df\u8bbf\u95ee\u5bc4\u5b58\u5668c3\uff0c\u8bbf\u95ee\u6743\u9650*\/
\nmcr\u00a0\u00a0\u00a0\u00a0 p15, 0, r4, c2, c0, 0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ load page table pointer \u00a0 \u00a0 \u00a0 \u00a0 \/*\u8bbe\u7f6e\u9875\u8868\u5730\u5740c2\uff0c\u9875\u8868\u57fa\u5730\u5740*\/
\nb\u00a0\u00a0\u00a0\u00a0 __turn_mmu_on \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8df3\u5230\u4e0b\u9762\u7684\u51fd\u6570*\/
\nENDPROC(__enable_mmu)<\/p>\n

\/*
\n* Enable the MMU.\u00a0 This completely changes the structure of the visible
\n* memory space.\u00a0 You will not be able to trace execution through this.
\n* If you have an enquiry about this, *please* check the linux-arm-kernel
\n* mailing list archives BEFORE sending another post to the list.
\n*
\n*\u00a0 r0\u00a0 = cp#15 control register
\n*\u00a0 r13 = *virtual* address to jump to upon completion
\n*
\n* other registers depend on the function called upon completion
\n*\/
\n.align\u00a0\u00a0\u00a0\u00a0 5
\n__turn_mmu_on: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8fdb\u5165MMU\u65b9\u5f0f\uff0c\u8fd9\u5c06\u6539\u53d8\u53ef\u89c1\u7684\u5185\u5b58\u7a7a\u95f4\uff0c\u4e0d\u80fd\u8ddf\u8e2a\u6267\u884c*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r0
\nmcr\u00a0\u00a0\u00a0\u00a0 p15, 0, r0, c1, c0, 0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ write control reg \u00a0\/*\u5199\u5165\u63a7\u5236\u5bc4\u5b58\u5668\uff0c\u6253\u5f00MMU\uff0c\u6253\u5f00cache\u7b49*\/
\nmrc\u00a0\u00a0\u00a0\u00a0 p15, 0, r3, c0, c0, 0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ read id reg \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8bfb\u4ee5\u4e0bid\u5bc4\u5b58\u5668*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r3, r3 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u7b49\u5927\u6307\u4ee4\u6267\u884c\u5b8c*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r3, r3
\nmov\u00a0\u00a0\u00a0\u00a0 pc, r13 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u524d\u9762\u8fdb\u5165__enable_mmu\u4e4b\u524d\u8bbe\u7f6e\u4e86r13=__switch_data\uff0c\u800c__switch_data\u7684\u7b2c\u4e00\u4e2a\u5730\u5740\u5904\u4e3a__mmap_switched\uff0c\u6240\u4ee5\u5c06\u6267\u884c__mmap_switched\uff0c\u5728head-common.S\u91cc\u9762*\/
\nENDPROC(__turn_mmu_on)<\/p>\n

\/*
\n* Setup the initial page tables.\u00a0 We only setup the barest
\n* amount which are required to get the kernel running, which
\n* generally means mapping in the kernel code.
\n*
\n* r8\u00a0 = machinfo
\n* r9\u00a0 = cpuid
\n* r10 = procinfo
\n*
\n* Returns:
\n*\u00a0 r0, r3, r6, r7 corrupted
\n*\u00a0 r4 = physical page table address
\n*\/
\n__create_page_tables:
\npgtbl\u00a0\u00a0\u00a0\u00a0 r4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ page table address \u00a0 \/*\u5b8f\uff0c\u9875\u8868\u5730\u574016k\u5bf9\u9f50\uff1aldr\u00a0\u00a0\u00a0\u00a0 \\rd, =(KERNEL_RAM_PADDR – 0x4000)*\/<\/p>\n

\/*
\n* Clear the 16K level 1 swapper page table
\n*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4e3a\u5185\u6838\u4ee3\u7801\u5b58\u50a8\u533a\u57df\u521b\u5efa\u9875\u8868\uff0c\u9996\u5148\u5c06\u5185\u6838\u8d77\u59cb\u5730\u5740-0x4000\u5230\u5185\u6838\u8d77\u59cb\u5730\u5740\u4e4b\u95f4\u768416K\u5b58\u50a8\u5668\u6e050\uff0c\u5c06\u521b\u5efa\u7684\u9875\u8868\u5b58\u4e8e\u6b64\u5904\u3002*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r3, #0
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r0, #0x4000
\n1:\u00a0\u00a0\u00a0\u00a0 str\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nteq\u00a0\u00a0\u00a0\u00a0 r0, r6
\nbne\u00a0\u00a0\u00a0\u00a0 1b<\/p>\n

ldr\u00a0\u00a0\u00a0\u00a0 r7, [r10, #PROCINFO_MM_MMUFLAGS] @ mm_mmuflags \/*\u4eceproc_info_list\u7ed3\u6784\u4e2d\u83b7\u53d6\u5b57\u6bb5__cpu_mm_mmu_flags\uff0c\u8be5\u5b57\u6bb5\u5305\u542b\u4e86\u5b58\u50a8\u7a7a\u95f4\u8bbf\u95ee\u6743\u9650\u7b49\u3002\u6b64\u5904\u6307\u4ee4\u6267\u884c\u4e4b\u540er7=0x00000c1e*\/<\/p>\n

\/*
\n* Create identity mapping for first MB of kernel to
\n* cater for the MMU enable.\u00a0 This identity mapping
\n* will be removed by paging_init().\u00a0 We use our current program
\n* counter to determine corresponding section base address.
\n*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r6, pc, lsr #20\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ start of kernel section \u00a0\/*\u6b64\u5904\u5efa\u7acb\u4e00\u4e2a\u7269\u7406\u5730\u5740\u5230\u7269\u7406\u5730\u5740\u7684\u5e73\u677f\u6620\u5c04\uff0c\u8fd9\u4e2a\u6620\u5c04\u5c06\u5728\u51fd\u6570paging_init().\u00a0 \u88ab\u6e05\u9664\u3002r6 = 0x300\u00a0 r3 = 0x30000c1e\u00a0\u00a0\u00a0 [0x30004c00]=0x30000c1e*\/
\norr\u00a0\u00a0\u00a0\u00a0 r3, r7, r6, lsl #20\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ flags + kernel base
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r4, r6, lsl #2]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ identity mapping<\/p>\n

\/*
\n* Now setup the pagetables for our kernel direct
\n* mapped region.
\n*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4,\u00a0 #(KERNEL_START & 0xff000000) >> 18 \u00a0\/*MMU\u662f\u901a\u8fc7C2\u4e2d\u57fa\u5730\u5740\uff08\u9ad818\u4f4d\uff09\u4e0e\u865a\u62df\u5730\u5740\u7684\u9ad812\u4f4d\u7ec4\u5408\u6210\u7269\u7406\u5730\u5740\uff0c\u5728\u8f6c\u6362\u8868\u4e2d\u67e5\u627e\u5730\u5740\u6761\u76ee\u3002R4\u4e2d\u5b58\u653e\u7684\u5c31\u662f\u8fd9\u4e2a\u57fa\u5730\u57400x30004000\u3002\u4e0b\u9762\u901a\u8fc7\u4e24\u6b21\u83b7\u53d6\u865a\u62df\u5730\u5740KERNEL_START\u7684\u9ad812\u4f4d\u3002KERNEL_START\u662f\u5185\u6838\u5b58\u653e\u7684\u8d77\u59cb\u5730\u5740\uff0c\u4e3a0X30008000\u3002r0 = 0x30007000*\/
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0, #(KERNEL_START & 0x00f00000) >> 18]! \u00a0 \/*r0 \u5b58\u653e\u7684\u662f\u8f6c\u6362\u8868\u7684\u8d77\u59cb\u4f4d\u7f6e*\/
\nldr\u00a0\u00a0\u00a0\u00a0 r6, =(KERNEL_END – 1) \u00a0 \u00a0 \u00a0 \/*\u83b7\u53d6\u5185\u6838\u7684\u5c3e\u90e8\u865a\u62df\u5730\u5740\u5b58\u4e8er6\u4e2d*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r0, #4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u7b2c\u4e00\u4e2a\u5730\u5740\u6761\u76ee\u5b58\u653e\u57280x30007004\u5904\uff0c\u4ee5\u540e\u4e00\u6b21\u9012\u589e*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r4, r6, lsr #18 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u8ba1\u7b97\u6700\u540e\u4e00\u4e2a\u5730\u5740\u6761\u76ee\u5b58\u653e\u7684\u4f4d\u7f6e*\/
\n1:\u00a0\u00a0\u00a0\u00a0 cmp\u00a0\u00a0\u00a0\u00a0 r0, r6 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u586b\u5145\u8fd9\u4e4b\u95f4\u7684\u5730\u5740\u6761\u76ee*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r3, r3, #1 << 20 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6bcf\u4e00\u4e2a\u5730\u5740\u6761\u76ee\u4ee3\u8868\u4e861MB\u7a7a\u95f4\u7684\u5730\u5740\u6620\u5c04\u3002\u7269\u7406\u5730\u5740\u5c06\u4ece0x30100000 \u5f00\u59cb\u6620\u5c04\u30020X30000000\u5f00\u59cb\u76841MB\u7a7a\u95f4\u5c06\u5728\u4e0b\u9762\u6620\u5c04\u3002*\/
\nstrls\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nbls\u00a0\u00a0\u00a0\u00a0 1b<\/p>\n

#ifdef CONFIG_XIP_KERNEL \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u5982\u679c\u662fXIP\u5c31\u8fdb\u884c\u4ee5\u4e0b\u6620\u5c04\uff0c\u8fd9\u53ea\u662f\u5c06\u5185\u6838\u4ee3\u7801\u5b58\u50a8\u7684\u7a7a\u95f4\u91cd\u65b0\u6620\u5c04\u3002*\/
\n\/*
\n* Map some ram to cover our .data and .bss areas.
\n*\/
\norr\u00a0\u00a0\u00a0\u00a0 r3, r7, #(KERNEL_RAM_PADDR & 0xff000000)
\n.if\u00a0\u00a0\u00a0\u00a0 (KERNEL_RAM_PADDR & 0x00f00000)
\norr\u00a0\u00a0\u00a0\u00a0 r3, r3, #(KERNEL_RAM_PADDR & 0x00f00000)
\n.endif
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4,\u00a0 #(KERNEL_RAM_VADDR & 0xff000000) >> 18
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0, #(KERNEL_RAM_VADDR & 0x00f00000) >> 18]!
\nldr\u00a0\u00a0\u00a0\u00a0 r6, =(_end – 1)
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r0, #4
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r4, r6, lsr #18
\n1:\u00a0\u00a0\u00a0\u00a0 cmp\u00a0\u00a0\u00a0\u00a0 r0, r6
\nadd\u00a0\u00a0\u00a0\u00a0 r3, r3, #1 << 20
\nstrls\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nbls\u00a0\u00a0\u00a0\u00a0 1b
\n#endif<\/p>\n

\/*
\n* Then map first 1MB of ram in case it contains our boot params.
\n*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4, #PAGE_OFFSET >> 18 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0\u00a0\/*\u6620\u5c040X30000000\u5f00\u59cb\u76841MB\u7a7a\u95f4\u3002PAGE_OFFSET = 0XC0000000,PHYS_OFFSET = 0X30000000, r0 = 0x30007000,\u4e0a\u9762\u662f\u4ece0x30007004\u5f00\u59cb\u5b58\u653e\u5730\u5740\u6761\u76ee\u7684\u3002*\/
\norr\u00a0\u00a0\u00a0\u00a0 r6, r7, #(PHYS_OFFSET & 0xff000000) \u00a0 \/*r6= 0x30000c1e*\/
\n.if\u00a0\u00a0\u00a0\u00a0 (PHYS_OFFSET & 0x00f00000)
\norr\u00a0\u00a0\u00a0\u00a0 r6, r6, #(PHYS_OFFSET & 0x00f00000)
\n.endif
\nstr\u00a0\u00a0\u00a0\u00a0 r6, [r0] \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u5c060x30000c1e\u5b58\u4e8e0x30007000\u5904\u3002*\/<\/p>\n

#ifdef CONFIG_DEBUG_LL \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8c03\u8bd5\u800c\u505a\u7684\u76f8\u5173\u6620\u5c04*\/
\nldr\u00a0\u00a0\u00a0\u00a0 r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
\n\/*
\n* Map in IO space for serial debugging.
\n* This allows debug messages to be output
\n* via a serial console before paging_init.
\n*\/
\nldr\u00a0\u00a0\u00a0\u00a0 r3, [r8, #MACHINFO_PGOFFIO]
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4, r3
\nrsb\u00a0\u00a0\u00a0\u00a0 r3, r3, #0x4000\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ PTRS_PER_PGD*sizeof(long)
\ncmp\u00a0\u00a0\u00a0\u00a0 r3, #0x0800\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ limit to 512MB
\nmovhi\u00a0\u00a0\u00a0\u00a0 r3, #0x0800
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r0, r3
\nldr\u00a0\u00a0\u00a0\u00a0 r3, [r8, #MACHINFO_PHYSIO]
\norr\u00a0\u00a0\u00a0\u00a0 r3, r3, r7
\n1:\u00a0\u00a0\u00a0\u00a0 str\u00a0\u00a0\u00a0\u00a0 r3, [r0], #4
\nadd\u00a0\u00a0\u00a0\u00a0 r3, r3, #1 << 20
\nteq\u00a0\u00a0\u00a0\u00a0 r0, r6
\nbne\u00a0\u00a0\u00a0\u00a0 1b
\n#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
\n\/*
\n* If we’re using the NetWinder or CATS, we also need to map
\n* in the 16550-type serial port for the debug messages
\n*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4, #0xff000000 >> 18
\norr\u00a0\u00a0\u00a0\u00a0 r3, r7, #0x7c000000
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0]
\n#endif
\n#ifdef CONFIG_ARCH_RPC
\n\/*
\n* Map in screen at 0x02000000 & SCREEN2_BASE
\n* Similar reasons here – for debug.\u00a0 This is
\n* only for Acorn RiscPC architectures.
\n*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4, #0x02000000 >> 18
\norr\u00a0\u00a0\u00a0\u00a0 r3, r7, #0x02000000
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0]
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r4, #0xd8000000 >> 18
\nstr\u00a0\u00a0\u00a0\u00a0 r3, [r0]
\n#endif
\n#endif
\nmov\u00a0\u00a0\u00a0\u00a0 pc, lr
\nENDPROC(__create_page_tables)
\n.ltorg<\/p>\n

#include “head-common.S”<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

\u8981\u6ce8\u610f\u548c\u201cboot\/compressed\/head.S\u201d\u7684\u533a\u522b\u3002 \u8fdb\u5165\u8fd9\u4e2a\u4ee3\u7801\u65f6\uff0c\u4ece\u89e3\u538b\u7f29\u4ee3\u7801\u4f20\u5165\u7684\u53c2\u6570\uff1ar0 …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15],"tags":[242,263,243,244],"class_list":["post-341","post","type-post","status-publish","format-standard","hentry","category-linuxandroid","tag-head-s","tag-liinux","tag-243","tag-244"],"views":1632,"_links":{"self":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=341"}],"version-history":[{"count":1,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/341\/revisions"}],"predecessor-version":[{"id":342,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/341\/revisions\/342"}],"wp:attachment":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=341"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}