Need help with the Uncompressed kernel be overriden after decompress_kernel called?

Hi all.

In arch/x86/boot/compressed/head_32.S

before the call of decompress_kernel()
it load the address of z_extract_offset_negative(%ebx) as the output address
and actually the output_len of the decompressed kernel is larger than  extract_offset
so the decompressed data will override the uncompressed data begin at input_data
Is that the case?
How does it worked as the the input buffer is covered by the output buffer while uncompressing?
It confused me a lot.
or I'd made some misunderstanding on the decompressing routine?

Thanks. 


2011-08-27 
jiangtao.jit