In message [ref] Steven Hanley wrote:
you seem to be confused anyway, yes the kernel is compressed for x86
machiens (it is however not compressed for other architectures, my ppc
box uses a normal uncompresased vmlinux image.
Well, on the (embedded) PowerPC systems we are running we use
compressed kernel images - saving lots of space in expensive FLASH
memory is reason enough.
wheras a kernel image (for ppc) will look like
[17:18:53] 1 innuendo sjh ~>file /mac/System\ Folder/Linux\
Kernels/vmlinux-2.2.15pre14
/mac/System Folder/Linux Kernels/vmlinux-2.2.15pre14: ELF 32-bit MSB
executable, PowerPC or cisco 4500, version 1, statically linked, not
stripped
This is what you see. Bat some things look different from what they
really are.
I see this:
-> file linux-2.2.13/arch/ppc/mbxboot/zvmlinux
linux-2.2.13/arch/ppc/mbxboot/zvmlinux: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1, statically linked, not stripped
Nevertheless, this file _contains_ a compressed (gzipped) Linux
kernel image as a special section "image":
-> powerpc-linux-objdump -h linux-2.2.13/arch/ppc/mbxboot/zvmlinux
linux-2.2.13/arch/ppc/mbxboot/zvmlinux: file format elf32-powerpc
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00004a90 00100000 00100000 00010000 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .rodata 000006a0 00104a90 00104a90 00014a90 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 .data 0000031c 00106000 00106000 00016000 2**2
CONTENTS, ALLOC, LOAD, DATA
3 .bss 000031fc 00107000 00107000 00017000 2**2
ALLOC
4 image 0005d3f8 00000000 00000000 00017000 2**0
CONTENTS, READONLY
which is a plain all ordinary elf binary pretty much
the compressed kernels found on x86 boxes will look like
There are more things in heaven and earth, Steven, / Than are dreamt
of in your philosophy. :-)
it may seem you can just gzip an uncompressed vmlinux and get a vmlinuz
that will boot, except if you notice the devel image just there is not a
gzip file. There is some executable code added on the front of the image
so the x86 box will run it on boot up, some of this code uncompresses
the image.
Same on (embedded) PowerPC
Now of course I wonder why you would need the ability as after all a
linux box is all you need to compile and make the image, or heck a
There are systems which are too slow and/or too limited to compile a
kernel (especially embedded systems).
And of course remember you dont need otr use compressed images on ppc
machines.
You do, in some cases.
Wolfgang Denk
--
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd@denx.de
Do not follow where the path may lead....go instead where there is no
path and leave a trail.
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