Hi Farid, Farid Zakaria <fmzak...@ucsc.edu> skribis:
[...] >> I guess the advantage is that you don’t need the ld.so patch. The >> downside is that PatchELF needs to be able to write longer NEEDED >> strings in the dynamic section, which it may not always be successful at >> (I think?). > > I can't claim to be a ELF specification guru but I have not > encountered that longer NEEDED strings to be a cause for failure. > The emacs example is a pretty good test case because the transitive > closure of all NEEDED libraries is quite large, which all seem to be > added successfully to the ELF header. Well, we’d need a closer look, but I think PatchELF may need to enlarge the relevant string table, and that may not always be possible. > The benefit to me seems: > 1 - does not need a glibc patch for functionality (although for other > libc such as musl it might in this case > https://www.openwall.com/lists/musl/2021/12/21/1) > 2 - understanding the dependencies of an application become simpler > 3 - there are esoteric cases where in fact libraries might link to the > wrong libraries (although they are correct at build time) given a > RUNPATH/RPATH since there are subtleties with the inheritance model. > > I'm actually researching ways to improve (3) as well through > mentorship with Tom Scogland by researching alternative ways to do > linking: > - RUNPATH per NEEDED > - the ability to specify whether a RUNPATH should be inherited or not > to downstream dependencies OK. >> Also, I wonder if the absolute file names in NEEDED interfere with uses >> of $LD_LIBRARY_PATH (making it impossible to force use of another >> libxyz.so than the one that would be found in RUNPATH.) > > Correct. For a system with reproducibility in mind this can perhaps be > a desired feature. > It is the current limitation of the proposal. I think it’s still useful to allow users to bypass normal mechanisms, be it via LD_LIBRARY_PATH or LD_PRELOAD. > In fact, Carlos brought up a great philosophical question: > "Is linking to libraries through a content-addressable value allowed > for LGPL software?" > What if the linked address also forced the content-address by having > it resolve to something on IPFS ? Oh you mean it could be thought of a static linking, conceptually? Good question. Ludo’.
