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?
(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".
(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.
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
--
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Greg Ungerer -- Principal Engineer EMAIL: g...@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
8 Gardner Close FAX: +61 7 3217 5323
Milton, QLD, 4064, Australia WEB: http://www.SnapGear.com
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