{"id":343,"date":"2018-03-14T09:42:54","date_gmt":"2018-03-14T01:42:54","guid":{"rendered":"http:\/\/www.max-shu.com\/blog\/?p=343"},"modified":"2018-03-14T09:42:54","modified_gmt":"2018-03-14T01:42:54","slug":"linux%e7%9a%84arch-arm-kernel-head-common-s","status":"publish","type":"post","link":"http:\/\/www.max-shu.com\/blog\/?p=343","title":{"rendered":"linux\u7684arch\/arm\/kernel\/head-common.S"},"content":{"rendered":"
\u6700\u7ec8\u8c03\u7528c\u51fd\u6570start_kernel()\u6267\u884c\u5185\u6838\u8fdb\u7a0b<\/div>\n
<\/div>\n
<\/div>\n
#define ATAG_CORE 0x54410001
\n#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)<\/p>\n

.type\u00a0\u00a0\u00a0\u00a0 __switch_data, %object \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u7531head.S\u8df3\u8f6c\u8fc7\u6765*\/
\n__switch_data:
\n.long\u00a0\u00a0\u00a0\u00a0 __mmap_switched \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4f1a\u8df3\u5230__mmap_switched\u6267\u884c*\/
\n.long\u00a0\u00a0\u00a0\u00a0 __data_loc\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6570\u636e\u5b58\u653e\u4f4d\u7f6e*\/
\n.long\u00a0\u00a0\u00a0\u00a0 __data_start\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r5 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u6570\u636e\u5f00\u59cb\u4f4d\u7f6e\uff0c\u8fd9\u4e9b\u5728vmlinux.lds.S\u91cc\u9762\u4f1a\u5bf9\u5e94\u76f8\u5e94\u6bb5*\/
\n.long\u00a0\u00a0\u00a0\u00a0 __bss_start\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r6 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*BSS\u6bb5\u5f00\u59cb\u4f4d\u7f6e*\/
\n.long\u00a0\u00a0\u00a0\u00a0 _end\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r7 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*BSS\u7ed3\u675f\u4f4d\u7f6e\uff0c\u4e5f\u662f\u5185\u6838\u7ed3\u675f\u4f4d\u7f6e*\/
\n.long\u00a0\u00a0\u00a0\u00a0 processor_id\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8fd9\u4e9b\u4f1a\u5728setup.c\u91cc\u9762\u7528\u5230\uff1aunsigned int processor_id;\u00a0EXPORT_SYMBOL(processor_id);\uff0c\u5176\u4e2dEXPORT_SYMBOL\u5b9a\u4e49\u5728include\/module.h\uff0c\u7531extern typeof(sym) sym;\u53ef\u77e5\uff0c\u662f\u7528extern\u8868\u793a\u5b9a\u4e49\u5728\u5916\u90e8\uff0c\u5373\u672c\u5904\u3002*\/<\/p><\/div>\n

\u00a0\u00a0\u00a0\u00a0 .long\u00a0\u00a0\u00a0\u00a0 __machine_arch_type\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r5
\n.long\u00a0\u00a0\u00a0\u00a0 __atags_pointer\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r6
\n.long\u00a0\u00a0\u00a0\u00a0 cr_alignment\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ r7
\n.long\u00a0\u00a0\u00a0\u00a0 init_thread_union + THREAD_START_SP @ sp<\/p>\n

\/*
\n* The following fragment of code is executed with the MMU on in MMU mode,
\n* and uses absolute addresses; this is not position independent.
\n*
\n*\u00a0 r0\u00a0 = cp#15 control register
\n*\u00a0 r1\u00a0 = machine ID
\n*\u00a0 r2\u00a0 = atags pointer
\n*\u00a0 r9\u00a0 = processor ID
\n*\/
\n__mmap_switched: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6709\u4e0a\u9762__switch_data\u8df3\u8f6c\u8fdb\u6765\uff0c\u8fd9\u662f\u5728MMU\u542f\u7528\u6a21\u5f0f\u4e0b\u6267\u884c\u7684\u7b2c\u4e00\u6bb5\u6307\u4ee4<\/span><\/b>*\/
\nadr\u00a0\u00a0\u00a0\u00a0 r3, __switch_data + 4<\/p>\n

ldmia\u00a0\u00a0\u00a0\u00a0 r3!, {r4, r5, r6, r7}
\ncmp\u00a0\u00a0\u00a0\u00a0 r4, r5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Copy data segment if needed
\n1:\u00a0\u00a0\u00a0\u00a0 cmpne\u00a0\u00a0\u00a0\u00a0 r5, r6 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u5c06r4\u5f00\u59cb\u7684\u6570\u636e\u6bb5\u642c\u79fb\u5230r5\uff0c\u5c31\u662f\u628a__data_loc\u642c\u79fb\u5230__data_start\u5904*\/
\nldrne\u00a0\u00a0\u00a0\u00a0 fp, [r4], #4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*fp\u4e3ar11\uff0c\u53c2\u6570\u6307\u9488*\/
\nstrne\u00a0\u00a0\u00a0\u00a0 fp, [r5], #4
\nbne\u00a0\u00a0\u00a0\u00a0 1b<\/p>\n

mov\u00a0\u00a0\u00a0\u00a0 fp, #0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Clear BSS (and zero fp)
\n1:\u00a0\u00a0\u00a0\u00a0 cmp\u00a0\u00a0\u00a0\u00a0 r6, r7 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u628aBSS\u6bb5\u6e050*\/
\nstrcc\u00a0\u00a0\u00a0\u00a0 fp, [r6],#4
\nbcc\u00a0\u00a0\u00a0\u00a0 1b<\/p>\n

ldmia\u00a0\u00a0\u00a0\u00a0 r3, {r4, r5, r6, r7, sp}
\nstr\u00a0\u00a0\u00a0\u00a0 r9, [r4]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Save processor ID \u00a0 \/*\u4fdd\u5b58\u5904\u7406\u5668ID\u5230processor_id*\/
\nstr\u00a0\u00a0\u00a0\u00a0 r1, [r5]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Save machine type \u00a0\/*\u4fdd\u5b58\u673a\u5668\u7c7b\u578b\u5230__machine_arch_type*\/
\nstr\u00a0\u00a0\u00a0\u00a0 r2, [r6]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Save atags pointer \u00a0\/*\u4fdd\u5b58\u53c2\u6570\u5230cr_alignment*\/
\nbic\u00a0\u00a0\u00a0\u00a0 r4, r0, #CR_A\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Clear ‘A’ bit
\nstmia\u00a0\u00a0\u00a0\u00a0 r7, {r0, r4}\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ Save control register values \u00a0\/*\u8bbe\u7f6e\u63a7\u5236\u5bc4\u5b58\u5668*\/
\nb\u00a0\u00a0\u00a0\u00a0 start_kernel \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u8df3\u8f6c\u5230init\/main.c\u7684c\u51fd\u6570start_kernel\u5904\u6267\u884c\u3002*\/
\nENDPROC(__mmap_switched)<\/p>\n

\/*
\n* Exception handling.\u00a0 Something went wrong and we can’t proceed.\u00a0 We
\n* ought to tell the user, but since we don’t have any guarantee that
\n* we’re even running on the right architecture, we do virtually nothing.
\n*
\n* If CONFIG_DEBUG_LL is set we try to print out something about the error
\n* and hope for the best (useful if bootloader fails to pass a proper
\n* machine ID for example).
\n*\/
\n__error_p: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u5904\u7406\u9519\u8bef*\/
\n#ifdef CONFIG_DEBUG_LL
\nadr\u00a0\u00a0\u00a0\u00a0 r0, str_p1
\nbl\u00a0\u00a0\u00a0\u00a0 printascii \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6253\u5370ascii\u5b57\u7b26\u4e32\uff0c\u8fd9\u4e2a\u51fd\u6570\u5b9a\u4e49\u5728debug.S\u3002*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r9
\nbl\u00a0\u00a0\u00a0\u00a0 printhex8 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6253\u5370r9\u673acpuid\uff0c\u8fd9\u4e2a\u51fd\u6570\u5b9a\u4e49\u5728debug.S*\/
\nadr\u00a0\u00a0\u00a0\u00a0 r0, str_p2
\nbl\u00a0\u00a0\u00a0\u00a0 printascii \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u8f93\u51fa\u5b8c\u6574*\/
\nb\u00a0\u00a0\u00a0\u00a0 __error \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u8df3\u5230__error*\/
\nstr_p1:\u00a0\u00a0\u00a0\u00a0 .asciz\u00a0\u00a0\u00a0\u00a0 “\\nError: unrecognized\/unsupported processor variant (0x”
\nstr_p2:\u00a0\u00a0\u00a0\u00a0 .asciz\u00a0\u00a0\u00a0\u00a0 “).\\n”
\n.align
\n#endif
\nENDPROC(__error_p)<\/p>\n

__error_a: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4e0d\u652f\u6301\u7684\u673a\u5668ID\u9519\u8bef\u5904\u7406*\/
\n#ifdef CONFIG_DEBUG_LL
\nmov\u00a0\u00a0\u00a0\u00a0 r4, r1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ preserve machine ID
\nadr\u00a0\u00a0\u00a0\u00a0 r0, str_a1
\nbl\u00a0\u00a0\u00a0\u00a0 printascii
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r4
\nbl\u00a0\u00a0\u00a0\u00a0 printhex8
\nadr\u00a0\u00a0\u00a0\u00a0 r0, str_a2
\nbl\u00a0\u00a0\u00a0\u00a0 printascii
\nadr\u00a0\u00a0\u00a0\u00a0 r3, 3f
\nldmia\u00a0\u00a0\u00a0\u00a0 r3, {r4, r5, r6}\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get machine desc list
\nsub\u00a0\u00a0\u00a0\u00a0 r4, r3, r4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get offset between virt&phys
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, r4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ convert virt addresses to
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r6, r4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ physical address space
\n1:\u00a0\u00a0\u00a0\u00a0 ldr\u00a0\u00a0\u00a0\u00a0 r0, [r5, #MACHINFO_TYPE]\u00a0\u00a0\u00a0\u00a0 @ get machine type
\nbl\u00a0\u00a0\u00a0\u00a0 printhex8
\nmov\u00a0\u00a0\u00a0\u00a0 r0, #’\\t’
\nbl\u00a0\u00a0\u00a0\u00a0 printch
\nldr\u00a0\u00a0\u00a0\u00a0 r0, [r5, #MACHINFO_NAME]\u00a0\u00a0\u00a0\u00a0 @ get machine name
\nadd\u00a0\u00a0\u00a0\u00a0 r0, r0, r4
\nbl\u00a0\u00a0\u00a0\u00a0 printascii
\nmov\u00a0\u00a0\u00a0\u00a0 r0, #’\\n’
\nbl\u00a0\u00a0\u00a0\u00a0 printch
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, #SIZEOF_MACHINE_DESC\u00a0\u00a0\u00a0\u00a0 @ next machine_desc
\ncmp\u00a0\u00a0\u00a0\u00a0 r5, r6
\nblo\u00a0\u00a0\u00a0\u00a0 1b
\nadr\u00a0\u00a0\u00a0\u00a0 r0, str_a3
\nbl\u00a0\u00a0\u00a0\u00a0 printascii
\nb\u00a0\u00a0\u00a0\u00a0 __error
\nENDPROC(__error_a)<\/p>\n

str_a1:\u00a0\u00a0\u00a0\u00a0 .asciz\u00a0\u00a0\u00a0\u00a0 “\\nError: unrecognized\/unsupported machine ID (r1 = 0x”
\nstr_a2:\u00a0\u00a0\u00a0\u00a0 .asciz\u00a0\u00a0\u00a0\u00a0 “).\\n\\nAvailable machine support:\\n\\nID (hex)\\tNAME\\n”
\nstr_a3:\u00a0\u00a0\u00a0\u00a0 .asciz\u00a0\u00a0\u00a0\u00a0 “\\nPlease check your kernel config and\/or bootloader.\\n”
\n.align
\n#endif<\/p>\n

__error: \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\/*\u6700\u7ec8\u9519\u8bef\u5904\u7406*\/
\n#ifdef CONFIG_ARCH_RPC
\n\/*
\n* Turn the screen red on a error – RiscPC only.
\n*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r0, #0x02000000 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u5c4f\u5e55\u663e\u793a\u7ea2\u8272*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r3, #0x11
\norr\u00a0\u00a0\u00a0\u00a0 r3, r3, r3, lsl #8
\norr\u00a0\u00a0\u00a0\u00a0 r3, r3, r3, lsl #16
\nstr\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
\n#endif
\n1:\u00a0\u00a0\u00a0\u00a0 mov\u00a0\u00a0\u00a0\u00a0 r0, r0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u4e00\u6761\u6307\u4ee4\u65e0\u9650\u5faa\u73af*\/
\nb\u00a0\u00a0\u00a0\u00a0 1b
\nENDPROC(__error)<\/p>\n

\/*
\n* Read processor ID register (CP#15, CR0), and look up in the linker-built
\n* supported processor list.\u00a0 Note that we can’t use the absolute addresses
\n* for the __proc_info lists since we aren’t running with the MMU on
\n* (and therefore, we are not in the correct address space).\u00a0 We have to
\n* calculate the offset.
\n*
\n*\u00a0\u00a0\u00a0\u00a0 r9 = cpuid
\n* Returns:
\n*\u00a0\u00a0\u00a0\u00a0 r3, r4, r6 corrupted
\n*\u00a0\u00a0\u00a0\u00a0 r5 = proc_info pointer in physical address space
\n*\u00a0\u00a0\u00a0\u00a0 r9 = cpuid (preserved)
\n*\/
\n__lookup_processor_type: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u67e5\u627eproc_info_list\u8fd9\u4e2a\u7ed3\u6784\u6570\u7ec4\uff0c\u53d6\u5f97\u5bf9\u5e94\u7684\u5904\u7406\u673a\u4fe1\u606f\uff0c\u8fd4\u56der5\u4e3a\u6307\u5411\u7ed3\u6784\u7684\u6307\u9488*\/
\nadr\u00a0\u00a0\u00a0\u00a0 r3, 3f \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u5f97\u5230\u4e0b\u97623\u6807\u7b7e\u5904\u7684\u5b9e\u9645\u7269\u7406\u5730\u5740*\/
\nldmda\u00a0\u00a0\u00a0\u00a0 r3, {r5 – r7} \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4ece3\u6807\u7b7e\u5904\u5f80\u4e0b\u8f7d\u5165\u5730\u5740\u5230r5,r6,r7\uff0c\u90fd\u662f\u865a\u62df\u5730\u5740\uff0c\u5c31\u662fr5=__proc_info_begin\uff0cr6=__proc_info_end\uff0cr7\uff1d\u6807\u7b7e3\u7684\u5730\u5740*\/<\/p><\/div>\n

\u00a0\u00a0\u00a0\u00a0 sub\u00a0\u00a0\u00a0\u00a0 r3, r3, r7\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get offset between virt&phys \u00a0\/*\u5f97\u5230\u7269\u7406\u5730\u5740\u548c\u865a\u62df\u5730\u5740\u7684\u504f\u79fb*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, r3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ convert virt addresses to \u00a0\/*\u5f97\u5230\u7269\u7406\u5730\u5740*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r6, r3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ physical address space
\n1:\u00a0\u00a0\u00a0\u00a0 ldmia\u00a0\u00a0\u00a0\u00a0 r5, {r3, r4}\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ value, mask \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u53d6\u5f97\u7ed3\u6784\u7684\u503c\uff0c r3\u4e3a\u503c\uff0cr4\u4e3a\u63a9\u7801*\/
\nand\u00a0\u00a0\u00a0\u00a0 r4, r4, r9\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ mask wanted bits \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u6839\u636ecpuid\u548c\u63a9\u7801\u5f97\u5230\u5b9e\u9645cpu\u6807\u8bb0*\/
\nteq\u00a0\u00a0\u00a0\u00a0 r3, r4 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u67e5\u770br3\u662f\u5426\u7b49\u4e8er4*\/
\nbeq\u00a0\u00a0\u00a0\u00a0 2f \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u67e5\u5230\u5219\u8fd4\u56de*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, #PROC_INFO_SZ\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ sizeof(proc_info_list) \u00a0\/*\u6307\u9488\u6307\u5411\u4e0b\u4e00\u4e2a\u7ed3\u6784*\/
\ncmp\u00a0\u00a0\u00a0\u00a0 r5, r6 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u7ed3\u6784\u6570\u7ec4\u662f\u5426\u5230\u5e95*\/
\nblo\u00a0\u00a0\u00a0\u00a0 1b \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u7ee7\u7eed\u5224\u65ad*\/
\nmov\u00a0\u00a0\u00a0\u00a0 r5, #0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ unknown processor \u00a0\/*\u6807\u8bb0\u6ca1\u627e\u5230*\/
\n2:\u00a0\u00a0\u00a0\u00a0 mov\u00a0\u00a0\u00a0\u00a0 pc, lr
\nENDPROC(__lookup_processor_type)<\/p>\n

\/*
\n* This provides a C-API version of the above function.
\n*\/
\nENTRY(lookup_processor_type) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*c\u8c03\u7528\u65b9\u5f0f*\/
\nstmfd\u00a0\u00a0\u00a0\u00a0 sp!, {r4 – r7, r9, lr}
\nmov\u00a0\u00a0\u00a0\u00a0 r9, r0
\nbl\u00a0\u00a0\u00a0\u00a0 __lookup_processor_type
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r5
\nldmfd\u00a0\u00a0\u00a0\u00a0 sp!, {r4 – r7, r9, pc}
\nENDPROC(lookup_processor_type)<\/p>\n

\/*
\n* Look in <asm\/procinfo.h> and arch\/arm\/kernel\/arch.[ch] for
\n* more information about the __proc_info and __arch_info structures.
\n*\/
\n.long\u00a0\u00a0\u00a0\u00a0 __proc_info_begin \u00a0 \/*3\u6807\u7b7e\u5f80\u4e0b\u5730\u5740\u662f__proc_info_begin\uff0c\u5b9a\u4e49\u5728vmlinux.lds.S\u7684.init\u6bb5\u7684proc.info.init\uff0c\u8fd9\u4e2a\u53c8\u5b9a\u4e49\u5728proc-(arch).S\u91cc\u9762\uff0c\u5bf9\u5e94\u7684c\u7ed3\u6784\u4e3aProcinfo.h\u7684proc_info_list\u3002*\/<\/p><\/div>\n

\u00a0\u00a0\u00a0\u00a0 .long\u00a0\u00a0\u00a0\u00a0 __proc_info_end
\n3:\u00a0\u00a0\u00a0\u00a0 .long\u00a0\u00a0\u00a0\u00a0 .
\n.long\u00a0\u00a0\u00a0\u00a0 __arch_info_begin \u00a0\/*3\u6807\u7b7e\u5f80\u4e0a\u5730\u5740\u662f__arch_info_begin\uff0c\u5b9a\u4e49\u5728vmlinux.lds.S\u7684.init\u6bb5\u7684arch.info.init\uff0c\u8fd9\u4e2a\u53c8\u5b9a\u4e49\u5728Arch.h\u7684MACHINE_START\u5904\uff0c\u5bf9\u5e94\u7684c\u7ed3\u6784\u4e3aArch.h\u7684machine_desc\u3002*\/<\/div>\n
\u00a0\u00a0\u00a0\u00a0 .long\u00a0\u00a0\u00a0\u00a0 __arch_info_end<\/p>\n

\/*
\n* Lookup machine architecture in the linker-build list of architectures.
\n* Note that we can’t use the absolute addresses for the __arch_info
\n* lists since we aren’t running with the MMU on (and therefore, we are
\n* not in the correct address space).\u00a0 We have to calculate the offset.
\n*
\n*\u00a0 r1 = machine architecture number
\n* Returns:
\n*\u00a0 r3, r4, r6 corrupted
\n*\u00a0 r5 = mach_info pointer in physical address space
\n*\/
\n__lookup_machine_type: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0\/*\u67e5\u627emachine_desc\u8fd9\u4e2a\u7ed3\u6784\u6570\u7ec4\uff0c\u53d6\u5f97\u5bf9\u5e94\u7684\u673a\u5668\u4fe1\u606f\uff0cr5\u8fd4\u56de\u6307\u9488\u6307\u5411\u7ed3\u6784*\/
\nadr\u00a0\u00a0\u00a0\u00a0 r3, 3b \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0\/*\u5f97\u5230\u4e0a\u97623\u6807\u7b7e\u5904\u7684\u5730\u5740*\/
\nldmia\u00a0\u00a0\u00a0\u00a0 r3, {r4, r5, r6} \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4ece3\u6807\u7b7e\u5904\u5f80\u4e0a\u8f7d\u5165\u5730\u5740\u5230r4,r5,r6\uff0c\u5c31\u662fr4=\u6807\u7b7e3\u7684\u5730\u5740\uff0cr5=__arch_info_begin\uff0cr6\uff1d__arch_info_end*\/<\/p><\/div>\n

\u00a0\u00a0\u00a0\u00a0 sub\u00a0\u00a0\u00a0\u00a0 r3, r3, r4\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ get offset between virt&phys \u00a0\/*\u5f97\u5230\u865a\u62df\u5730\u5740\u548c\u7269\u7406\u5730\u5740\u504f\u79fb*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, r3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ convert virt addresses to \u00a0 \u00a0 \u00a0 \u00a0\/*\u8f6c\u6362\u865a\u62df\u5730\u5740\u5230\u7269\u7406\u5730\u5740*\/
\nadd\u00a0\u00a0\u00a0\u00a0 r6, r6, r3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ physical address space
\n1:\u00a0\u00a0\u00a0\u00a0 ldr\u00a0\u00a0\u00a0\u00a0 r3, [r5, #MACHINFO_TYPE]\u00a0\u00a0\u00a0\u00a0 @ get machine type \u00a0 \/*\u53d6\u5f97\u7ed3\u6784\u4e2d\u7684\u673a\u5668\u7c7b\u578b*\/
\nteq\u00a0\u00a0\u00a0\u00a0 r3, r1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ matches loader number? \u00a0 \u00a0 \u00a0\/*\u673a\u5668\u7c7b\u578b\u662f\u5426\u4e00\u81f4*\/
\nbeq\u00a0\u00a0\u00a0\u00a0 2f\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ found
\nadd\u00a0\u00a0\u00a0\u00a0 r5, r5, #SIZEOF_MACHINE_DESC\u00a0\u00a0\u00a0\u00a0 @ next machine_desc
\ncmp\u00a0\u00a0\u00a0\u00a0 r5, r6
\nblo\u00a0\u00a0\u00a0\u00a0 1b
\nmov\u00a0\u00a0\u00a0\u00a0 r5, #0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ unknown machine
\n2:\u00a0\u00a0\u00a0\u00a0 mov\u00a0\u00a0\u00a0\u00a0 pc, lr
\nENDPROC(__lookup_machine_type)<\/p>\n

\/*
\n* This provides a C-API version of the above function.
\n*\/
\nENTRY(lookup_machine_type) \u00a0 \u00a0\/*c\u8c03\u7528\u65b9\u5f0f*\/
\nstmfd\u00a0\u00a0\u00a0\u00a0 sp!, {r4 – r6, lr}
\nmov\u00a0\u00a0\u00a0\u00a0 r1, r0
\nbl\u00a0\u00a0\u00a0\u00a0 __lookup_machine_type
\nmov\u00a0\u00a0\u00a0\u00a0 r0, r5
\nldmfd\u00a0\u00a0\u00a0\u00a0 sp!, {r4 – r6, pc}
\nENDPROC(lookup_machine_type)<\/p>\n

\/* Determine validity of the r2 atags pointer.\u00a0 The heuristic requires
\n* that the pointer be aligned, in the first 16k of physical RAM and
\n* that the ATAG_CORE marker is first and present.\u00a0 Future revisions
\n* of this function may be more lenient with the physical address and
\n* may also be able to move the ATAGS block if necessary.
\n*
\n* r8\u00a0 = machinfo
\n*
\n* Returns:
\n*\u00a0 r2 either valid atags pointer, or zero
\n*\u00a0 r5, r6 corrupted
\n*\/<\/p><\/div>\n

\n

\u5173\u4e8e\u53c2\u6570\u94fe\u8868\uff1a<\/span><\/p>\n

\u5185\u6838\u53c2\u6570\u94fe\u8868\u7684\u683c\u5f0f\u548c\u8bf4\u660e\u53ef\u4ee5\u4ece\u5185\u6838\u6e90\u4ee3\u7801\u76ee\u5f55\u6811\u4e2d\u7684\u00a0include\/asm-arm\/setup.h<\/span>\u4e2d<\/span><\/span><\/p>\n

\u627e\u5230\uff0c\u53c2\u6570\u94fe\u8868\u5fc5\u987b\u4ee5ATAG_CORE\u00a0<\/span>\u5f00\u59cb\uff0c\u4ee5<\/span>ATAG_NONE<\/span>\u7ed3\u675f\u3002\u8fd9\u91cc\u7684\u00a0<\/span>ATAG_CORE<\/span>\uff0c<\/span><\/span><\/p>\n

ATAG_NONE\u662f\u5404\u4e2a\u53c2\u6570\u7684\u6807\u8bb0\uff0c\u672c\u8eab\u662f\u4e00\u4e2a<\/span>32<\/span>\u4f4d\u503c\uff0c\u4f8b\u5982\uff1a<\/span>ATAG_CORE=0x54410001<\/span>\u3002<\/span><\/span><\/p>\n

\u5176\u5b83\u7684\u53c2\u6570\u6807\u8bb0\u8fd8\u5305\u62ec\uff1a\u00a0ATAG_MEM32\u00a0<\/span>\uff0c\u00a0<\/span>ATAG_INITRD\u00a0<\/span>\uff0c\u00a0<\/span>ATAG_RAMDISK\u00a0<\/span>\uff0c<\/span><\/span><\/p>\n

ATAG_COMDLINE\u00a0\u7b49\u3002\u6bcf\u4e2a\u53c2\u6570\u6807\u8bb0\u5c31\u4ee3\u8868\u4e00\u4e2a\u53c2\u6570\u7ed3\u6784\u4f53\uff0c\u7531\u5404\u4e2a\u53c2\u6570\u7ed3\u6784\u4f53\u6784\u6210\u4e86\u53c2<\/span><\/span><\/p>\n

\u6570\u94fe\u8868\u3002\u53c2\u6570\u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a\u00a0\u00a0<\/span><\/p>\n

\u00a0struct tag {
\nstruct\u00a0 tag_header\u00a0 hdr;
\nunion {
\nstruct tag_core\u00a0 core;
\nstruct tag_mem32\u00a0\u00a0 mem;
\nstruct tag_videotext videotext;
\nstruct tag_ramdisk\u00a0 ramdisk;
\nstruct tag_initrd\u00a0\u00a0\u00a0\u00a0 initrd;
\nstruct tag_serialnr\u00a0\u00a0\u00a0\u00a0 serialnr;
\nstruct tag_revision\u00a0 revision;
\nstruct tag_videolfb\u00a0 videolfb;
\nstruct tag_cmdline\u00a0 cmdline;
\nstruct tag_acorn\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 acorn;
\nstruct tag_memclk\u00a0\u00a0\u00a0 memclk;
\n} u;
\n};<\/span><\/p>\n

\u53c2\u6570\u7ed3\u6784\u4f53\u5305\u62ec\u4e24\u4e2a\u90e8\u5206\uff0c\u4e00\u4e2a\u662f\u00a0tag_header<\/span>\u7ed3\u6784\u4f53<\/span>,<\/span>\u4e00\u4e2a\u662f<\/span>u<\/span>\u8054\u5408\u4f53\u3002<\/span><\/span><\/p>\n

tag_header\u7ed3\u6784\u4f53\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a\u00a0<\/span><\/span><\/p>\n

\u00a0\u00a0\u00a0struct\u00a0tag_header\u00a0{\u00a0<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0u32\u00a0size;\u00a0\u00a0\u00a0<\/span><\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0u32\u00a0tag;\u00a0<\/span><\/p>\n

};\u00a0<\/span><\/p>\n

\u5176\u4e2d\u00a0size<\/span>\uff1a\u8868\u793a\u6574\u4e2a\u00a0<\/span>tag\u00a0<\/span>\u7ed3\u6784\u4f53\u7684\u5927\u5c0f<\/span>(<\/span>\u7528\u5b57\u7684\u4e2a\u6570\u6765\u8868\u793a\uff0c\u800c\u4e0d\u662f\u5b57\u8282\u7684\u4e2a\u6570<\/span>)<\/span>\uff0c\u7b49\u4e8e<\/span><\/span><\/p>\n

tag_header\u7684\u5927\u5c0f\u52a0\u4e0a\u00a0<\/span>u<\/span>\u8054\u5408\u4f53\u7684\u5927\u5c0f\uff0c\u4f8b\u5982\uff0c\u53c2\u6570\u7ed3\u6784\u4f53\u00a0<\/span>ATAG_CORE\u00a0<\/span>\u7684\u00a0<\/span><\/span><\/p>\n

size=(sizeof(tag->tag_header)+sizeof(tag->u.core))>>2\uff0c\u4e00\u822c\u901a\u8fc7\u51fd\u6570\u00a0<\/span>tag_size(struct\u00a0*\u00a0tag_xxx)<\/span><\/span><\/p>\n

\u6765\u83b7\u5f97\u6bcf\u4e2a\u53c2\u6570\u7ed3\u6784\u4f53\u7684\u00a0size<\/span>\u3002\u5176\u4e2d\u00a0<\/span>tag<\/span>\uff1a\u8868\u793a\u6574\u4e2a\u00a0<\/span>tag\u00a0<\/span>\u7ed3\u6784\u4f53\u7684\u6807\u8bb0\uff0c\u5982\uff1a<\/span>ATAG_CORE<\/span><\/span><\/p>\n

\u7b49\u3002\u00a0<\/span><\/p>\n

__vet_atags: \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u68c0\u67e5\u53c2\u6570\u94fe\u8868\u5408\u6cd5\u6027*\/
\ntst\u00a0\u00a0\u00a0\u00a0 r2, #0x3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ aligned? \u00a0\/*r2\u6307\u5411\u8be5\u53c2\u6570\u94fe\u8868\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u6b64\u5904\u5224\u65ad\u5b83\u662f\u5426\u5b57\u5bf9\u9f50*\/
\nbne\u00a0\u00a0\u00a0\u00a0 1f<\/p>\n

ldr\u00a0\u00a0\u00a0\u00a0 r5, [r2, #0]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ is first tag ATAG_CORE? \/*\u83b7\u53d6\u7b2c\u4e00\u4e2atag\u7ed3\u6784\u7684size\uff0c#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2) \u5224\u65ad\u8be5tag\u7684\u957f\u5ea6\u662f\u5426\u5408\u6cd5*\/
\nsubs\u00a0\u00a0\u00a0\u00a0 r5, r5, #ATAG_CORE_SIZE
\nbne\u00a0\u00a0\u00a0\u00a0 1f
\nldr\u00a0\u00a0\u00a0\u00a0 r5, [r2, #4] \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \/*\u83b7\u53d6\u7b2c\u4e00\u4e2atag\u7ed3\u6784\u4f53\u7684\u6807\u8bb0*\/
\nldr\u00a0\u00a0\u00a0\u00a0 r6, =ATAG_CORE \u00a0 \u00a0 \/*\u5224\u65ad\u7b2c\u4e00\u4e2atag\u7ed3\u6784\u4f53\u7684\u6807\u8bb0\u662f\u4e0d\u662fATAG_CORE*\/
\ncmp\u00a0\u00a0\u00a0\u00a0 r5, r6
\nbne\u00a0\u00a0\u00a0\u00a0 1f<\/p>\n

mov\u00a0\u00a0\u00a0\u00a0 pc, lr\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @ atag pointer is ok \u00a0\/*\u53c2\u6570\u94fe\u8868\u6b63\u5e38\uff0c\u9000\u51fa*\/<\/p>\n

1:\u00a0\u00a0\u00a0\u00a0 mov\u00a0\u00a0\u00a0\u00a0 r2, #0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\/*\u4e0d\u6b63\u5e38\uff0c\u8bbe\u7f6er2\u4e3a0\uff0c\u9000\u51fa*\/
\nmov\u00a0\u00a0\u00a0\u00a0 pc, lr
\nENDPROC(__vet_atags)<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

\u6700\u7ec8\u8c03\u7528c\u51fd\u6570start_kernel()\u6267\u884c\u5185\u6838\u8fdb\u7a0b #define ATAG_CORE 0x5441000 …<\/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":[264,9,243,244],"class_list":["post-343","post","type-post","status-publish","format-standard","hentry","category-linuxandroid","tag-head-common-s","tag-linux","tag-243","tag-244"],"views":2157,"_links":{"self":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/343","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=343"}],"version-history":[{"count":1,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/343\/revisions"}],"predecessor-version":[{"id":344,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/343\/revisions\/344"}],"wp:attachment":[{"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=343"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=343"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.max-shu.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=343"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}