Re: broken linuxulator in -current as of Jan 8 17:51:45 CET

On Wednesday 10 January 2007 13:21, Alexander Leidinger wrote:
> Quoting Tijl Coosemans <tijl_at_ulyssis.org>
>> On Wednesday 10 January 2007 07:53, Alexander Leidinger wrote:
>>> That's not possible. The way the linuxulator works is:
>>>   - the linker in userland calls open("/foo/bar")
>>>   - kernel looks for "/compat/linux/foo/bar"
>>>     * it is there -> return it
>>>     * it is not there -> look for "/foo/bar"
>>>       + if it is there -> return it
>>>       + if it is not there -> return error
>>>   - the userland get's something which may be linux or FreeBSD stuff
>>>   - the linker read()s this
>>>   - the linker sees a wrong ELF ABI and bails out
>>
>> That means the linker tries to open /usr/lib/librt.so.1 instead of
>> /lib/librt.so.1 which doesn't exist under /compat/linux. So I added a
>> symlink there.
>>
>> ln -s ../../lib/librt-2.3.6.so /compat/linux/usr/lib/librt.so.1
>>
>> And now everything works.
>>
>> % ldd /compat/linux/bin/ls
>> /compat/linux/bin/ls:
>>         librt.so.1 => /lib/obsolete/linuxthreads/librt.so.1 (0x4807c000)
>>
>> I think this is an easier solution than changing the runtime linker.
> 
> Does it still work with 2.6.16 (can't test ATM)? If yes: I agree, it
> is more easy and we can change this in the linux base port very fast

Yes, it works with 2.6.16. Here's what I think is happening:

ls is linked against librt.so.1 with /lib and /usr/lib as runtime
search paths and thus:

- linker calls open("/lib/librt.so.1")
- kernel returns "/compat/linux/lib/librt.so.1"
- linker reads and sees it requires kernel ABI 2.4.20
  * when osrelease=2.6.16, this is ok, all done
  * when osrelease=2.4.2
    + linker calls open("/usr/lib/librt.so.1")
    + kernel returns "/compat/linux/usr/lib/librt.so.1" (symlink)
      (previously kernel returned FreeBSD "/usr/lib/librt.so.1" here,
       which caused linker error)
    + linker reads and sees it requires kernel ABI 2.4.20, not ok
    + linker calls open("/lib/obsolete/linuxthreads/librt.so.1")
    + kernel returns "/compat/linux/lib/obsolete/linuxthreads/librt.so.1"
    + linker reads and sees it requires kernel ABI 2.2.5, ok, all done