Re: Multiarch interpreter names for traditional architectures

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 05/02/2018 05:33, Javier Serrano Polo wrote:
> El dl 05 de 02 de 2018 a les 07:01 +0100, Florian Weimer va escriure:
>> Please rephrase that in a way which separates what happens today from 
>> what should happen in the future.
> 
> We are still in the alpha on x86 example. What happens today on your
> systems:
> 
>      1. Kernel starts the alpha emulator.
>      2. The emulator looks for /lib/ld-linux.so.2.
>      3. The program fails.
> 
> What happens today on my systems:
> 
>      1. Kernel starts the alpha emulator.
>      2. The emulator looks for /lib/ld-linux.so.2.
>      3. User has configured the emulator to redirect all file operations
>         to /lib/ld-linux-alpha.so.2.
>      4. The program runs, but the path /lib/ld-linux.so.2 will not work
>         as expected.
> 
> What should happen in the future:
> 
>      1. Kernel starts the alpha emulator.
>      2. The emulator looks for /lib/ld-linux.so.2.
>      3. User has configured the emulator to use /lib/ld-linux-alpha.so.2
>         as the interpreter, even if /lib/ld-linux.so.2 exists.
>      4. The program runs.
> 
> What happens with multiarch binaries:
> 
>      1. Kernel starts the alpha emulator.
>      2. The emulator looks for /lib/ld-linux-alpha.so.2.
>      3. The program runs.
> 
>> Currently, the kernel maps both the ELF interpreter and the executable. 
>> Do you intend to change that?
> 
> The only ability I add to the kernel is to map an alternative
> interpreter if the requested one is not found.
> 
> But we are deviating from the topic: what should the multiarch
> interpreter names be? I like Zack's view. It does not follow the current
> practice of using infixes, but multiarch filesystems become cleaner and
> interpreter names are unique easily.
> 

My understanding is the names were defined back then without the idea to
have incompatible ABI to share a common filesystem (which is possible now
through emulation) and as Florian put changing them now is ABI break which
although fixable by user (through relink to adjust INTERP section) is not
an option imho.

I think we can try to push for newer ports an abis to have distinguish
names from now on with this requisite in mind and document that Debian
way is a possible alternative to this issue.

Also, I think Andreas questioning is why emulator has not been configured
to look into sysroot/lib/ instead of /lib/.