勤学似春起之苗,不见其增,日有所长; 辍学如磨刀之石,不见其损,日所有亏!


[译]Kernel Memory Layout on ARM Linux


 Kernel Memory Layout on ARM Linux


  Russell King <rmk@arm.linux.org.uk>
       November 17, 2005 (2.6.15)

This document describes the virtual memory layout which the Linux kernel uses for ARM processors.  It indicates which regions are free for platforms to use, and which are used by generic code.


The ARM CPU is capable of addressing a maximum of 4GB virtual memory space, and this must be shared between user space processes, the kernel, and hardware devices.


As the ARM architecture matures, it becomes necessary to reserve certain regions of VM space for use for new facilities; therefore this document may reserve more VM space over time.


Start(开始地址)  End(结束地址)  Use(使用说明)
ffff8000 ffffffff copy_user_page / clear_user_page use. For SA11xx and Xscale, this is used to setup a minicache mapping.


ffff1000 ffff7fff Reserved.
    Platforms must not use this address range. 保留,ARM平台一定不使用这个区间。

ffff0000 ffff0fff CPU vector page. CPU向量表
    The CPU vectors are mapped here if the CPU supports vector relocation (control register V bit.)


ffc00000 fffeffff DMA memory mapping region.  Memory returned by the dma_alloc_xxx functions will be dynamically mapped here.


ff000000 ffbfffff Reserved for future expansion of DMA mapping region.


VMALLOC_END feffffff Free for platform use, recommended. 建议平台保留。
    VMALLOC_END must be aligned to a 2MB boundary. VMALLOC_END必须在2MB的边界上对齐。  

VMALLOC_START VMALLOC_END-1 vmalloc() / ioremap() space. vmalloc
    Memory returned by vmalloc/ioremap will be dynamically placed in this region. VMALLOC_START may be based upon the value of the high_memory variable.

  vmalloc/ioremap 函数返回的内存会被动态的放到该区间。VMALLOC_START 可能的值可能会基于high_memory变量的值而有所不同。

PAGE_OFFSET high_memory-1 Kernel direct-mapped RAM region. 内核直接映射内存区间。
    This maps the platforms RAM, and typically maps all platform RAM in a 1:1 relationship.


TASK_SIZE PAGE_OFFSET-1 Kernel module space    Kernel modules inserted via insmod are
    placed here using dynamic mappings.


00001000 TASK_SIZE-1 User space mappings 用户空间
    Per-thread mappings are placed here via
    the mmap() system call.每个进程通过mmap系统调用的映射放到这里。

00000000 00000fff CPU vector page / null pointer trap CPU向量表,NULL指针陷井
    CPUs which do not support vector remapping place their vector page here.  NULL pointer dereferences by both the kernel and user space are also caught via this mapping. 


Please note that mappings which collide with the above areas may result
in a non-bootable kernel, or may cause the kernel to (eventually) panic
at run time.

请注意:一些与上面冲突的映射会导致内核无法启动,或者可能在运行时会产生(最终)内核panic !

Since future CPUs may impact the kernel mapping layout, user programs
must not access any memory which is not mapped inside their 0x0001000
to TASK_SIZE address range.  If they wish to access these areas, they
must set up their own mappings using open() and mmap().


posted on 2009-10-25 21:25  Wu.Country@侠缘  阅读(1850)  评论(0编辑  收藏  举报