Booting from a different location

I am running Linux 2.6.26 on a PPC. I want to boot linux without using a bootloader to speed up the boot process but, due to the size of the kernel, I cannot put it at the reset vector. I was told that I have to put a branch instruction at the reset vector location and branch to the location where my kernel is.

How do I put a branch instruction at the reset vector?

Reply to
Washington Ratso
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No idea what you are talking about. Whatever you do, you need a bootloader. The kernel must be put into memory. Now if you do not like the 10 sec delay, put in a 1 sec delay, or 0 sec delay. (Not advised since that means you can never get at the boot sequence and alter things if something goes wrong).

Why in the world would you want to write your own bootloader? You do not have enough to do in your life, but want to spend half a year doing something others have already done far better?

Reply to
Unruh

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I was told bu a consultant that it is possible to boot Linux in about

3 seconds. All one has to do is put vmlinux.gz at the reset vector. He said he has done this. No bootloader is needed. But, I cannot put vmlinux.gz at the reset vector because there is not enough space for me to put vmlinux.gz there. So, he said to put a branch instruction at the reset vector that would say to branch to an address where I could put vmlinux.gz.
Reply to
Washington Ratso

But...that's the compressed kernel image. Compressed as in non-executable. Non-executable as in your processor can't treat it as instructions, and therefore shouldn't have a reset vector pointing into it. Unless I'm seriously mistaken you've either misunderstood your consultant or hired the wrong one.

--=20 Rob Gaddi, Highland Technology Email address is currently out of order

Reply to
Rob Gaddi

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Since you are posting this in comp.arch.embedded, I'll assume the consultant meant to put the images into ROM and boot from ROM. Even decompressing and loading to RAM will be a lot faster reading ROM than reading the image from disc. You would still need a boot loader.

As far as setting the boot vector, try reading the documentation of your motherboard hardware. Changing the boot vector possibly means changing the BIOS, or changing basic hardware settings. I'm guessing changing the BIOS (ROM).

Ed

Reply to
Ed Prochak

Maybe he meant XIP? Who knows, the OP is so vague.

Reply to
zwsdotcom

No comment on your purposes. To put a branch instruction in read the manual for the CPU, find out what the opcode is, how the operands are arranged, and install that in the code loaded. It's called assembly language.

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 [mail]: Chuck F (cbfalconer at maineline dot net) 
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Reply to
CBFalconer

That's one and the same thing. A consultant whose advice could not be understood was the wrong one to hire.

Reply to
Hans-Bernhard Bröker

You may be barking up the wrong tree here.

Please check that the main culprit of the boot-up speed is the bootloader. The Linux start-up contains much more and slower operations than loading the kernel (and maybe the initial root disk image).

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Tauno Voipio
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Reply to
Tauno Voipio

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