LMA != VMA when compiling a kernel

[M. Warner Losh]

In message: <fd183dc60905211318v67d77378t4100f3a0035124ed at mail.gmail.com>
            Guillaume Ballet <gballet at gmail.com> writes:
: I am still working on a port of FreeBSD to the beagleboard, and am
: currently working on enabling the VM. So far, I have loaded the kernel
: at phys_addr = virt_addr = 0x80000000, because that is where the RAM
: is. However, when enabling the VM, I would like the kernel virtual
: addresses to start with 0xC0000000 as they do on most other platform.

This isn't a bad idea...

: Hence, I have been trying to set the ELF file sections' VMAs to
: something starting with 0xC and the LMAs to something starting with
: 0x8. It turns out that just setting KERNPHYSADDR and KERNVIRTADDR is
: not enough >.< If found a way to do this by chaning the script linker
: and adding AT after each section declaration, and it works fine. But
: it's tedious, hacky and lots of hardcoded values only work with my
: platform.

Want to share?

: Googling for ideas, I found that there has been some discussion about
: it barely a year ago. Yet, it doesn't seem to have yielded any
: tangible result. Would someone have addressed the progress in the mean
: time?
: 
: I guess another way to look at it would be to work it around by also
: porting a full-fledged loader(8). A task which I have delayed to until
: I get a booting kernel - maybe not the wisest move :) Still, I'm
: curious about the possibility of specifying distinct LMAs and VMAs for
: the kernel executable.

Its already there, but requires a lot of code in the primary boot
loader to call back into to do things like loading files and doing
network I/O.

Also, while a secondary boot loader makes sense in the higher end
booting environment where you have lots of storage (say an SD or CF
card), it doesn't make so much sense for a more constrained boot a
ramdisk from flash setup.

Warner