[U-Boot-Users] directly execute linux zImage: cmd_bootz

[U-Boot-Users] directly execute linux zImage: cmd_bootz

[Holger Schurig]

Hi !

Attached is a patch for armboot that directly calls a Linux zImage. It has 
been tested on my PXA250 platform.

Prerequisites:

- works only on arm, because it takes stuff from asm_arm/armlinux.c
- set CONFIG_KERNEL_RAM_BASE to where the zImage is in Flash

Problems:

- I have no clue if the tag list get's correctly set up, I'm using a kernel 
2.4 which doesn't use the tags anyway.
- how can I pass the cmdline?
- Kernel 2.4. clobbers r2, the pointer to the tag list. In your fixup code you 
can have 

        MACHINE_START(...)
        BOOT_PARAMS(0xa0000100)
        ...
        MACHINE_END

but how put I *params to some fixed address?



I guess this is rather ugly, so comments on how to do it better are welcomed 
:-)
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[U-Boot-Users] directly execute linux zImage: cmd_bootz

["David Müller (ELSOFT AG)"]

Hello

Holger Schurig wrote:
> Hi !
> 
> Attached is a patch for armboot that directly calls a Linux zImage. It has 
> been tested on my PXA250 platform.
> 
> Prerequisites:
> 
> - works only on arm, because it takes stuff from asm_arm/armlinux.c
> - set CONFIG_KERNEL_RAM_BASE to where the zImage is in Flash
> 
> Problems:
> 
> - I have no clue if the tag list get's correctly set up, I'm using a kernel 
> 2.4 which doesn't use the tags anyway.

AFAICS 2.4 uses the tag list if there is one prepared by the bootloader.

> - how can I pass the cmdline?

By using the "ATAG_CMDLINE" in the tag list. Make sure you have defined 
"CONFIG_CMDLINE_TAG" in your u-boot config file.

> - Kernel 2.4. clobbers r2, the pointer to the tag list. In your fixup code you 
> can have 
> 
>         MACHINE_START(...)
>         BOOT_PARAMS(0xa0000100)
>         ...
>         MACHINE_END
> 
> but how put I *params to some fixed address?
> 

See 
http://sourceforge.net/mailarchive/forum.php?thread_id=1531608&forum_id=12898


Dave

[U-Boot-Users] directly execute linux zImage: cmd_bootz

[Robert Schwebel]

On Thu, Jan 23, 2003 at 08:58:18AM +0100, "David M?ller (ELSOFT AG)" wrote:
> AFAICS 2.4 uses the tag list if there is one prepared by the bootloader.

Nope. You have to pass BOOT_PARAMS(). See recent discussion on
arm-linux-kernel. 

Robert 
-- 
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[U-Boot-Users] directly execute linux zImage: cmd_bootz

[Holger Schurig]

> AFAICS 2.4 uses the tag list if there is one prepared by the bootloader.

No, it doesn't. See

http://www.arm.linux.org.uk/developer/booting.php

to find out that a boot loader should pass the address of the tag list in r2 
to the kernel. It's near the end. And then see

http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2003-January/013126.html

to see that 2.4-kernels currently don't use r2 and can't use in order to stay 
compatible. In fact, a 2.4. kernel trashes r2 right at the start, see

http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2003-January/013140.html



However, 2.5-kernels already employ the r2-rule.

I'm not sure, but I think that only Kernels for ARM (and for XScale) use this 
tagging at all, correct?

> See
> http://sourceforge.net/mailarchive/forum.php?thread_id=1531608&forum_id=128
>98

Ahh, here is the trick, use gd->bd->bi_boot_params

Thanks.

[U-Boot-Users] directly execute linux zImage: cmd_bootz

["David Müller (ELSOFT AG)"]

Hi

Holger Schurig wrote:
>>AFAICS 2.4 uses the tag list if there is one prepared by the bootloader.
> 
> 
> No, it doesn't. See
> 
> http://www.arm.linux.org.uk/developer/booting.php
>

I'm not speaking about the pointer to the tag list (which should be 
passed in r2, Linux 2.4 uses BOOT_PARAMS instead), i'm speacking about 
the tag list itself. Parameter passing from the bootloader to the kernel 
via the tag list is working, at least for me (using linux-2.4.19-rmk4 
kernel).


Dave