Hi Greg
Le 05/08/2012 06:50 AM, Greg Ungerer a écrit :
Hi Paul,
On 02/05/12 01:24, Paul Chavent wrote:
I'd like to try linux on an AT91SAM9G20 (i have a linuxstamp board), with MMU
disabled (the Hyok-Sung Choi& Hee-Chul Yun paper demonstrate that it could be
possible).
All the code seems to be present in the kernel...
So i would like to share my experience.
(1) I had to make two little changes in the kernel code :
- I'm not able to change the REMAP_VECTOR_TO_DRAM. I have submitted the problem
to the kbuild mailing list
(http://www.spinics.net/lists/linux-kbuild/msg06153.html).
Odd. Is it because DRAM_BASE is a numerical value?
- The soc_detect code that init the at91_soc_initdata structure is never
called. Later this structure is used unitialized.
I'm currently using the joined patch as a workaround. Someone can review it
please ?
It looks ok to me.
(2) I used to run the module with a "classic system" based on linux + eglibc,
and i needed only one toolchain (arm-xxx-linux-gnueabi) for the kernel and the userspace
apps.
I found that for the nommu case i wasn't able to build the kernel with the
userspace toolchain.
So I had to build 2 toolchain, based on binutils 2.22, gcc 4.7, uclibc 0.9.33.1
and linux 3.2.14 :
- an arm-xxx-eabi toolchain for the kernel
- an arm-xxx-uclinux-uclibceabi for the userspace apps
Do you confirm that it is not possible to compile the kernel with
arm-xxx-uclinux-uclibceabi ? Or, may i have misconfigured the toolchain (i join
the toolchain build procedure) ?
I build non-mmu ARM systems with the same toolchain. What was the failure
condition
when building the kernel with the arm-yyy-uclinux-uclibceabi tool chain?
When i build the kernel with the arm-yyy-uclinux-uclibceabi tool chain it builds without
error. But the kernel don't display anything when booting (not even the
"decompressing kernel" message).
(3) The arm-xxx-uclinux-uclibceabi with elf2flt seems to produce running bins
only if it is build with the uClibc DOPIC not set.
Is it required to disable DOPIC ?
Moreover, i can't run bins produced with a arm-xxx-linux-uclibceabi toolchain
and -Wl,-elf2flt (not uclinux one). Is it the expected behavior ?
Is it actually producing a FLAT format binary?
Maybe it is silently ignoring the "-Wl,-elf2flt".
Yes it produce flat binaries with the gotpic flag enabled...
(4) The elf2flt needs to be updated to be aware of the exidx section, and some
reloc types. I join the patch i currently use.
You shouldn't include a whole new elft2flt.ld for this. It is generated
(via autoconf) from the elf2flt.ld.in file. You should add your new
exidx section to that. If you want to generate a new patch with doing
it that way I can add it to the elf2flt CVS on uclinux.org.
In the previous mail, i joined a patch with an arm specific ld script derived
from the generic one.
I added the missing (exidx) sections, but i didn't remove other specific sections. For
example, It still contains "microblaze" comments, i'm not sure what we could
remove...
The patch would need some reviews.
Given these observations, i've been able to run a linux with an hello world as
the /init process.
My next tests will be to run threaded programs, c++ programs, then busybox.
A good start at least.
Regards
Greg
Thanks.
Paul.
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