BAT setting after bootrom? and where to load elf image?

BAT setting after bootrom? and where to load elf image?

[Tim Lai]

Hi, I am new to linux and trying to get some help from
some linux experts out here. I've been reading and
searching the mail list archive for the past few
weeks.
Here is what I have so far:

I have a ppc750 broad with vxWorks bootrom. I do not
have any device to reflash the broad. I read one of
the mail archive that someone write a program to
work with vxWorks bootrom. And this is what I want
to do. I plan to convert the vmlinux image to asm and
put it in the .text section of another elf file.
Load this elf file and relocate the vmlinux image to
0xC000000. Is this a feasible approach?

After the vxWorks bootrom come up, the BAT setting is
phy = virt. The board has 8Meg of RAM. Knowing the
linux kernel need to be at 0xC000000, should I change
the BAT setting to map 7-8M to 0xC0000000, then
copy the image to 0xC0000000?

I am a little confuse about the MMU in linux. Here is
what I understand:
after the bootrom, the CPU MMU should be phy = virt
after linux booted, linux MMU takes over, and kernel
space is 0xc0000000, and user space is 0x0 to
0xc0000000. What happened in between? Who is
responible for doing the mapping?

Thanks in advances.

Tim Lai


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Re: BAT setting after bootrom? and where to load elf image?

[Matt Porter]

On Tue, Jun 11, 2002 at 12:21:19PM -0700, Tim Lai wrote:
>
> Hi, I am new to linux and trying to get some help from
> some linux experts out here. I've been reading and
> searching the mail list archive for the past few
> weeks.
> Here is what I have so far:
>
> I have a ppc750 broad with vxWorks bootrom. I do not
> have any device to reflash the broad. I read one of
> the mail archive that someone write a program to
> work with vxWorks bootrom. And this is what I want
> to do. I plan to convert the vmlinux image to asm and
> put it in the .text section of another elf file.
> Load this elf file and relocate the vmlinux image to
> 0xC000000. Is this a feasible approach?
>
> After the vxWorks bootrom come up, the BAT setting is
> phy = virt. The board has 8Meg of RAM. Knowing the
> linux kernel need to be at 0xC000000, should I change
> the BAT setting to map 7-8M to 0xC0000000, then
> copy the image to 0xC0000000?
>
> I am a little confuse about the MMU in linux. Here is
> what I understand:
> after the bootrom, the CPU MMU should be phy = virt
> after linux booted, linux MMU takes over, and kernel
> space is 0xc0000000, and user space is 0x0 to
> 0xc0000000. What happened in between? Who is
> responible for doing the mapping?

However you want to do it, get the vmlinux located
at physical 0 and set r3-r7 as documented in head.S

Read head.S and you will see that it takes care of
(with some outside calls) all core MMU init for Linux.

Regards,
--
Matt Porter
porter@cox.net
This is Linux Country. On a quiet night, you can hear Windows reboot.

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