Linux内存分析(4) -- paging_init (setup_arch部分)

有了2和3的基础，我们来看一下setup_arch中的内存初始化函数：paging_init（）

 

void       __init     paging_init(

       struct meminfo             *mi,              //内存的描述信息

       struct machine_desc      *mdesc)         //机器信息，见“平台信息”

{

       void       *zero_page;

 

       build_mem_type_table();             //根据MEM的策略补充页表的属性

       prepare_page_table(mi);               //清除段映射（16K一级页表，从地址0开始的）

       bootmem_init(mi);                      //实现在arch\mm\init.c中，初始化bootmem分配信息

       //实际上是初始化引导阶段所使用的内存，当内核启动完成，将使用SLUB来管理内存，届时管理方法将和boot阶段会不一样。

 

       devicemaps_init(mdesc);              //映射中断向量表(一、二级)，注册模块时钟

 

       top_pmd = pmd_off_k(0xffff0000);     //获取中断向量的一级页表

 

       //在低端内存中申请一页内存并清0，注意返回的是虚拟地址

       zero_page = alloc_bootmem_low_pages(PAGE_SIZE);     

       memzero(zero_page, PAGE_SIZE);           

 

       //获取该虚拟地址对应的页描述符，注意empty_zero_page是全局变量                    

       empty_zero_page = virt_to_page(zero_page);

       flush_dcache_page(empty_zero_page);        //刷新D-CAHCE内容进RAM中

}

 

 

 

其中bootmem_init()函数见内存分析中，对bootmem.c文件的分析。其他的函数见我后一篇对arch\mmu.c文件的分析。

 

“平台信息”是我另外一篇文档，因为还未整理完，所以不便放出，先将其中相关部分的说明摘出：

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//include\asm-arm\proinfo.h

//处理器（CPU）信息

struct      proc_info_list {

       unsigned int                  cpu_val;                              //ID号

       unsigned int                  cpu_mask;                           //ID号中MASK的位

       unsigned long               __cpu_mm_mmu_flags;        /* used by head.S */

       unsigned long               __cpu_io_mmu_flags;           /* used by head.S */

       unsigned long               __cpu_flush;                        /* used by head.S */

       const char                     *arch_name;

       const char                     *elf_name;

       unsigned int                  elf_hwcap;

       const char                     *cpu_name;

       struct processor             *proc;

       struct cpu_tlb_fns          *tlb;

       struct cpu_user_fns        *user;

       struct cpu_cache_fns      *cache;

};

 

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//处理器信息：arch\arm\mm\proc-arm920.s

       .section   ".proc.info.init",    #alloc, #execinstr          //声明放入该段中

 

       .type              __arm920_proc_info,    #object

__arm920_proc_info:

       .long       0x41009200                                              //cpu value

       .long       0xff00fff0                                                //cpu mask

       .long   PMD_TYPE_SECT | \                                 //段描述

                     PMD_SECT_BUFFERABLE | \                  //B

                     PMD_SECT_CACHEABLE | \                   //C

                     PMD_BIT4 | \                                           //固定为1

                     PMD_SECT_AP_WRITE | \                       //权限读/写

                     PMD_SECT_AP_READ                     // __cpu_mm_mmu_flags(规格书P560)

 

       .long   PMD_TYPE_SECT | \

                     PMD_BIT4 | \

                     PMD_SECT_AP_WRITE | \

                     PMD_SECT_AP_READ                            // __cpu_io_mmu_flags

 

       b            __arm920_setup                                        // __cpu_flush

       .long       cpu_arch_name                                         // *arch_name

       .long       cpu_elf_name                                           // *elf_name

       .long       HWCAP_SWP | HWCAP_HALF | HWCAP_THUMB        // elf_hwcap

       .long       cpu_arm920_name                                    // *cpu_name

       .long       arm920_processor_functions                       // *proc

       .long       v4wbi_tlb_fns                                           // *tlb

       .long       v4wb_user_fns                                          // *user

 

#ifndef   CONFIG_CPU_DCACHE_WRITETHROUGH          //未定义

       .long       arm920_cache_fns

#else

       .long       v4wt_cache_fns                                         // *cache

#endif

 

       .size        __arm920_proc_info, . - __arm920_proc_info

 

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include\asm-arm\cpu-multi32.h

struct      processor {

       void (*_data_abort)(unsigned long pc);               // get data abort address/flags

       void (*_proc_init)(void);                                  // Set up any processor specifics

       void (*_proc_fin)(void);                                          // Disable any processor specifics

       void (*reset)(unsigned long addr) __attribute__((noreturn));             // Special stuff for a reset

       int (*_do_idle)(void);                                       // Idle the processor

       void (*dcache_clean_area)(void *addr, int size);  // Processor architecture specific

       void (*switch_mm)(unsigned long pgd_phys, struct mm_struct *mm);// Set the page table

       void (*set_pte_ext)(pte_t *ptep, pte_t pte, unsigned int ext);// Set a possibly extended PTE

} processor;

 

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//机器信息

//include\asm-arm\mach\arch.h

struct      machine_desc {

       unsigned int           nr;                        /* architecture number   */

       unsigned int           phys_io;                /* start of physical io     */

       unsigned int           io_pg_offst;           /* byte offset for io page tabe entry      */

 

       const char              *name;                  /* architecture name      */

       unsigned long        boot_params;         /* tagged list          */

 

       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                      (*map_io)(void);    /* IO mapping function  */

       void                      (*init_irq)(void);

       struct sys_timer      *timer;                  /* system tick timer       */

       void                      (*init_machine)(void);

};

 

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//arch\arm\mach-s3c2440\mach-utu2440.c

//machine_desc struct

MACHINE_START(UTU2440,    "UTU2440")

       .phys_io          = S3C2410_PA_UART,

    .io_pg_offst           = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,

    .boot_params      = S3C2410_SDRAM_PA + 0x100,

    .map_io         = utu2440_map_io,              //used in cpu.c

    .init_irq           = utu2440_init_irq,              //used in cpu.c

    .init_machine       = utu2440_init,                   //used in cpu.c

    .timer            = &s3c24xx_timer,

MACHINE_END

 

#define   MACHINE_START(_type,    _name)                         \

static const struct machine_desc    __mach_desc_UTU2440        \

 __used   __attribute__((__section__(".arch.info.init"))) = {             \

       .nr                 = MACH_TYPE_UTU2440,                       \

       .name             = UTU2440,

 

#define MACHINE_END                          \

};