[systemd-devel] Add ARCH parameter to /etc/os-release

[Koen Kooi]

Op 17 apr. 2013, om 20:19 heeft Lennart Poettering <lennart at poettering.net> het volgende geschreven:

> On Mon, 08.04.13 22:09, Askar Safin (safinaskar at mail.ru) wrote:
> 
>> 
>>> I'm not sure what problem the proposal is trying to solve.  Maybe it'd
>>> be clearer if that was provided.
>> I want to know what is the arches of the systems on my computer. I. e. I want to do the following:
>> 
>> for DISK in /dev/sd*; do
>>  mount "$DISK" /mnt
>>  source /mnt/etc/os-release
>>  echo "Arch of $DISK is $ARCH"
>> done
>> 
>> And I want to use this $ARCH to do "setarch", i. e.:
>>  mount /dev/some-dev /mnt
>>  source /mnt/etc/os-release
>>  setarch "$ARCH" chroot /mnt
>> So, this /mnt system will see "uname -m" output which is meaningful for the system.
> 
> My suggestion would be to write a little tool that does the equivalent
> to this:
> 
> readelf -h /usr/lib*/libdl*.so | grep Machine | cut -c38- | uniq
> 
> This will list you the architectures for which you have dynamic loaders
> installed. Since the dynamic loaders are hardcoded in all dynamic ELF
> binaries this list will tell you binaries of which archs you can execute
> on your system.

On my i7 laptop:

[koen at rrMBP mplayer2]$ readelf -h /usr/lib*/libdl*.so | grep Machine | cut -c38- | uniq
Advanced Micro Devices X86-64
Intel 80386

And on a cortex A8 device:

root at beaglebone:~# readelf -h /usr/lib*/libdl*.so | grep Machine | cut -c38- | uniq
ARM

So it returns something that could be considered usefull on my laptop, but the output on the beaglebone is useless. On ARM you need to know the following to see if you can execute the binary:

1) instruction set revision (armvX, e.g. armv5te, armv6, armv7a)
2) OABI or EABI
3) floating point calling conventions, softp vs hardfp

The first item is like i386, i486 etc. It's compatible only one way. The second is academical at this point, only luddites running kernel 2.4 are interested in OABI.
And then we get to the clusterfuck, floatingpoint ABI. I need to install binutils on my hardfloat system to see if that also says 'ARM', I bet it does.

But it does answer the "can I nspawn into this rootfs?" question for different architectures like powerpc vs x86 :)

regards,

Koen