请教：内核模块变量问题

EZWORD

请教内核模块中的一个全局变量，其存储地址以0xbf000000开头，是为什么？
谢谢。

accessory

are you sure it is 0xbf000000? It should be something bigger than 0xc0000000.

Godbach

LZ先搞清楚应用空间和内核空间对内存的划分和使用

EZWORD

LZ先搞清楚应用空间和内核空间对内存的划分和使用
Godbach 发表于 2010-08-28 11:51

    请指教，对于内存的使用确实不太清楚。

Godbach

呵呵，那就建议你先查一下相关的资料，有看不明白的，再发帖与大家交流。

zyr-linux

去找对应ARCH的地址映射说明，这个是X86_64的：

<previous description obsolete, deleted>

Virtual memory map with 4 level page tables:

0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
hole caused by [48:63] sign extension
ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
... unused hole ...
ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
ffffffffa0000000 - fffffffffff00000 (=1536 MB) module mapping space

The direct mapping covers all memory in the system up to the highest
memory address (this means in some cases it can also include PCI memory
holes).

vmalloc space is lazily synchronized into the different PML4 pages of
the processes using the page fault handler, with init_level4_pgt as
reference.

Current X86-64 implementations only support 40 bits of address space,
but we support up to 46 bits. This expands into MBZ space in the page tables.

-Andi Kleen, Jul 2004

wmmy2008

可能是映射了user space memory，然后在kernel直接操作这个user space memory.

linyunxian

正常的。动态加载的内核模块 text 段从 0xbf000000 开始