linux内核启动之lookup_machine_type
发布时间：2016-10-31 17:53:05 所属栏目：交互 来源：站长网
导读：1.有MMU的设备的启动过程 arch/arm/kernel/head.S .section ".text.head", "ax" ENTRY(stext) msr cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode @ and irqs disabled mrc p15, 0, r9, c0, c0 @ get processor id bl __lookup_processor_ty
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1.有MMU的设备的启动过程 arch/arm/kernel/head.S .section ".text.head", "ax" ENTRY(stext) msr cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode @ and irqs disabled mrc p15, 0, r9, c0, c0 @ get processor id bl __lookup_processor_type @ r5=procinfo r9=cpuid movs r10, r5 @ invalid processor (r5=0)? beq __error_p @ yes, error 'p' bl __lookup_machine_type @ r5=machinfo movs r8, r5 @ invalid machine (r5=0)? beq __error_a @ yes, error 'a' bl __vet_atags bl __create_page_tables /* * The following calls CPU specific code in a position independent * manner. See arch/arm/mm/proc-*.S for details. r10 = base of * xxx_proc_info structure selected by __lookup_machine_type * above. On return, the CPU will be ready for the MMU to be * turned on, and r0 will hold the CPU control register value. */ ldr r13, __switch_data @ address to jump to after @ mmu has been enabled adr lr, __enable_mmu @ return (PIC) address add pc, r10, #PROCINFO_INITFUNC ENDPROC(stext) 执行流程 1.__lookup_processor_type：确定内核是否支持该构架 2.__lookup_machine_type：确定内核是否支持此平台 3.__create_page_tables:建立一级页表 4.__enable_mmu:使能mmu 5.__switch_data arch/arm/kernel/head-common.S __switch_data --> __mmap_switched --> start_kernel 2.无MMU的设备的启动过程 .section ".text.head", "ax" .type stext, %function ENTRY(stext) ldr r1, =machine_arch_type @ find the machine type msr cpsr_c, #PSR_F_BIT | PSR_I_BIT | SVC_MODE @ ensure svc mode @ and irqs disabled #ifndef CONFIG_CPU_CP15 ldr r9, =CONFIG_PROCESSOR_ID #else mrc p15, 0, r9, c0, c0 @ get processor id #endif bl __lookup_processor_type @ r5=procinfo r9=cpuid movs r10, r5 @ invalid processor (r5=0)? beq __error_p @ yes, error 'p' bl __lookup_machine_type @ r5=machinfo movs r8, r5 @ invalid machine (r5=0)? beq __error_a @ yes, error 'a' ldr r13, __switch_data @ address to jump to after @ the initialization is done adr lr, __after_proc_init @ return (PIC) address add pc, r10, #PROCINFO_INITFUNC 其启动流程和上面基本相同 例子分享： 我现在移植的一个板子，是不带mmu的，刚开始怎么都启动不起来，打印出“done, booting the kernel",然后就无声无息了。后来在Kernel startup entry point开始处的ENTRY(stext)下添加了句代码： ”ldr r1, =machine_arch_type“就很顺利得起来了.后来分析知道，添加这句代码后就不会进行平台的匹配了！但是启动以后也是正常的！不知道此处平台匹配的真正意义是什么，还需要与有经验的朋友共同探讨。 xin.jin （编辑：南京站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
