linux 解壓後會跳轉到，kernel執行地址： head.S中入口執行。解壓之前的操作流程呢？

1. linux kernel 被uboot load到記憶體後的入口函式

arch/arm/boot/compressed/vmlinux.lds.in中定義了linux 入口：

OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{

....

這裡的start定義在 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實現在misc.c中，可以看到，misc中同樣定義了

unsigned int __machine_arch_type; 這個在kernel的setup.c中已經有定義了？unsigned int __machine_arch_type __read_mostly;

因此， 可以看到arch\arm\boot\compressed中程式碼編譯是獨立於kernel image的
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作者：thegameisfives
來源：CSDN
原文：https://blog.csdn.net/thegameisfives/article/details/9019503
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