linux kernel 自解压过程

来源：互联网发布：mysql 语句优化编辑：程序博客网时间：2024/06/05 14:18

linux 解压后会跳转到，kernel执行地址： head.S中入口执行。解压之前的操作流程呢？

1. linux kernel 被uboot load到内存后的入口函数

arch/arm/boot/compressed/vmlinux.lds.in中定义了linux 入口：

OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{

....

这里的start定义在 arch/arm/boot/compressed／head.s中

start:
       .type   start,#function
       .rept   7
       mov   r0, r0
       .endr
   ARM(       mov   r0, r0       )
   ARM(       b   1f       )
THUMB(       adr   r12, BSYM(1f)   )
THUMB(       bx   r12       )

THUMB(       bx   r12       )

       .word   0x016f2818       @ Magic numbers to help the loader
       .word   start           @ absolute load/run zImage address
       .word   _edata           @ zImage end address
THUMB(       .thumb           )
1:       mov   r7, r1           @ save architecture ID
       mov   r8, r2           @ save atags pointer

......

*
* The C runtime environment should now be setup sufficiently.
* Set up some pointers, and start decompressing.
*   r4 = kernel execution address
*   r7 = architecture ID
*   r8 = atags pointer
*/
       mov   r0, r4
       mov   r1, sp           @ malloc space above stack
       add   r2, sp, #0x10000   @ 64k max
       mov   r3, r7
       bl   decompress_kernel
       bl   cache_clean_flush
       bl   cache_off
       mov   r0, #0           @ must be zero
       mov   r1, r7           @ restore architecture number
       mov   r2, r8           @ restore atags pointer
       mov   pc, r4           @ call kernel

decompress_kernel实现在misc.c中，可以看到，misc中同样定义了

unsigned int __machine_arch_type; 这个在kernel的setup.c中已经有定义了？unsigned int __machine_arch_type __read_mostly;

因此，可以看到arch\arm\boot\compressed中代码编译是独立于kernel image的