Messages in this thread | | | Subject | Re: [PATCH] x86 boot enhancements, Clean up the 32bit entry points 6/11 | From | (Eric W. Biederman) | Date | 18 Apr 2002 12:11:55 -0600 |
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Etienne Lorrain <etienne_lorrain@yahoo.fr> writes:
> 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
That is what you quoted, so I assumed that is what you were talking about.
> 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.
Well it should be easier I put an explicit pointer to it.
> 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.
Nope. LOADED_HIGH in loadflags is set at compile time. It determines where the bootloader must load the compressed part of the kernel.
> So is it possible to write somewhere how much code to skip or the offset > of the kernel GZIP signature?
Already done.
> 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.
Yep.
> Else whatever signature at whatever fixed address with the code+rodata > size following would make me happy.
Check out the code.
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