[coreboot] x86 : Puzzles about reset code

[王翔]

source code like this:
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    .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

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

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王翔

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