On Sun, Nov 10, 2019 at 11:37 PM Caveman Al Toraboran <toraboracave...@protonmail.com> wrote: > > hi - is it possible to have some kind of fancy links that > know the name of the process that is trying to access > it, and based on its name, it links it to a file?
Yes, and that's used pretty extensively in busybox. Symlinks named any of its tools that point to it directly call into *that* tool. > i think if we have this, we can solve slotting in a simpler > way. e.g. we install libs in their own non-conflicting > locations, and then install for them such fancy sym links > with access that routes accessing processes to the right > version of the lib. I'm not entirely sure about the library level. Your goal sounds like one link to many library versions instead of many links to one library. A symlink itself can only point at one thing, so the filesystem level can't do that. So you would have to have a shim library that gets loaded, then loads the version the calling process needs... based on either an exhaustive table of the mappings of every binary to the versions they need, or some other magic.You wouldn't be able to just pick any version of a library and hand it back to a process, since major versions on libraries tend to break the interfaces they present, so you would end up having a 1:1 mapping of any particular binary calling a singular library version. That already happens based on the linker, and even works for less specific versioning in many cases with symlinks from, say, libc.so.6 and libc.so.6.2 pointing to libc.so.6.2.13 (which is actually a many links to one library technique that's already used). To change what interface a calling process *can* work with will require rebuilding it against the new major version of the library, and if it's one of those circular situations where it's part of the build process, you have to have both the old and new library available (one of the reason slots exist). The binary itself should contain enough detail to load the version *it* needs already, and then should be requesting that from the dynamic linker already... -- Poison [BLX] Joshua M. Murphy
