According arch/x86/boot/compressed/head_32.S and some comments:
======================================
/*
* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
*/
pushl %esi
leal (_bss-4)(%ebp), %esi
...
/*
* Jump to the relocated address.
*/
leal relocated(%ebx), %eax
jmp *%eax
ENDPROC(startup_32)
.text
relocated:
...
==========================
We can see the kernel moves itself, including both compressed and uncompressed
to the new location, and after finish moving, kernel also jump to the new
location.
And the below code in this file, uncompressed part will decompress compressed
part in-place, so it seems that uncompressed part is overwritten ...
At 2013-03-09 11:12:26,"leo kirotawa" <[email protected]> wrote:
I don't know if it can help you, but let's try. [1]
What I understand about that is. The compressed kernel is in fact a bzImage or
some zImage kernel, and it is a file. As the link says in that compressed file
we have this header that makes some early configurations. The kernel is
uncompressed into the memory and the compressed kernel remains in the place it
was before. Just what matter by the compressed kernel is that header info that
it use to setup the stack to the new kernel.
I'm no sure if I'm talking some nosense, but that was what I saw in kernel boot
files. Maybe some others mate here can complement or fix my thoughts here.
[1] http://www.ibm.com/developerworks/library/l-linuxboot/
On Fri, Mar 8, 2013 at 10:12 PM, Jacky <[email protected]> wrote:
Dear All,
Before, kernel first decompressed to other memory location and then merged and
put at final destination. Now, kernel decompression are decompressed in-place,
so-called in-place decompression.
But the compressed part is encompassed by uncompressed part. So, after
decompression, will the uncompressed part be overwritten by the decompressed
kernel ? If so, some uncompressed part such as deal with kernel relocation will
be overwritten by the decompressed kernel, which don't make sense, am I missed
something ?
Regards,
Jacky
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Leônidas S. Barbosa (Kirotawa)
Engenheiro de Software - IBM (LTC - Linux Technology Center)
MsC Sistemas e Computação
Bacharel em Ciências da Computação.
blog nerd: corecode.wordpress.com/
User linux : #480879
"Mais sábio é aquele que sabe que não sabe" (Sócrates)
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