[coreboot] x86 : Puzzles about reset code

[王翔]

source code like this:
-----------------------------------------------------------------------------------------------------
        .section ".reset", "ax", %progbits
        .code16
.globl  _start
_start:
        .byte  0xe9
        .int   _start16bit - ( . + 2 )
        /* Note: The above jump is hand coded to work around bugs in binutils.
         * 5 byte are used for a 3 byte instruction.  This works because x86
         * is little endian and allows us to use supported 32bit relocations
         * instead of the weird 16 bit relocations that binutils does not
         * handle consistently between versions because they are used so rarely.
         */
        .previous

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I tried to modify the code and passed test (use qemu test).
My code like this:
-----------------------------------------------------------------------------------------------------
        .section ".reset", "ax", %progbits
        .code16
.globl  _start
_start:
        jmp   _start16bit
        .previous

-----------------------------------------------------------------------------------------------------



What is the meaning of hand coding?  In 16-bit mode, the last two bytes are 
ignored.




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王翔

安全研究员

广州市腾御安信息科技有限公司





广州市天河区珠江新城华穗路406号保利克洛维二期中景A座1020-1024
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