Seems that previous message did not go through, rewrite.
I am sorry I did not check enough your patch.
You are speaking of: arch/i386/boot/compressed/head.S
I am speaking of: arch/i386/kernel/head.S
Gujin skip completely arch/i386/boot/compressed/* and really
boots the file '$$tmppiggy.gz' line 44 of file:
arch/i386/boot/compressed/Makefile
So you can do whatever you want with the "first" 32 bits entry point,
I am just concerned by the "second" kernel 32 bits entry point, in
arch/i386/kernel/head.S
I still have a problem to detect the size of your decompressor, and that
is my use of the "lss" instruction.
This "lss SYMBOL_NAME(stack_start),%esp" gives an access to the symbol
'stack_start', so it is quite easy to find back the GZIP signature
of the initial '$$tmppiggy.gz' in what I call my "compatibility" mode,
i.e. booting the legacy vmlinuz files - and skipping all of the real mode
code and the decompressor code.
This "lss" line has not always been at the same offset, but is around
since maybe even the 0.01 kernel, it is quite easy to find it from its
hexadecimal form. (function vmlinuz_header_treat() in vmlinuz.c of
Gujin).
The loaded high/loaded low stuff is just to know if I have to remove
0x100000 or 0x1000 from this symbol to have the number of bytes
to skip on the file.
By the way, the bit in the kernel header is set by the bootloader to say
where it has loaded the kernel, not by the compiler/linker chain.
So is it possible to write somewhere how much code to skip or the offset
of the kernel GZIP signature?
Something like:
jmp next
lss SYMBOL_NAME(stack_start),%esp
next:
Would make me really happy, but is dirty.
Changing the 'tmppiggy.lnk' in the Makefile can be done, but the value
(to know the length of the decompressor code) has to be _before_ the code
itself in the raw file.
Else whatever signature at whatever fixed address with the code+rodata
size following would make me happy.
Sorry again for the confusion,
Etienne.
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