I used to do this by padding initially with extra dots and slashes. (On Mac, the linker had a flag -headerpad_max_install_names that did something similar.) On Sun, Nov 28, 2021, 06:32 Jacob Kroon via Gcc-help <gcc-help@xxxxxxxxxxx> wrote: > On 11/28/21 12:44, Florian Weimer wrote: > > * Jacob Kroon via Gcc-help: > > > >> As part of an effort to make binaries reproducible regardless of their > >> build path, I need to enforce the same size of the RUNPATH entry in the > >> dynamic section during linking, even though I don't fill it completely. > >> Is it possible to give some flag to gnu ld that allows me to set it to a > >> specific size ? Or is there a way to patch the elf file after linking, > >> so that the entry has a specified size ? > > > > Do you want to allocate specific size so that you can patch in a > > different value later? > > > > Yes exactly, but see below. > > > The RUNPATH strings are in the string table, so it's necessary to > > allocate space there, and be able to find it during patching. > > > > Solaris offers this mechanism: > > > > | DT_SUNW_STRPAD > > | > > | The total size, in bytes, of the unused reserved space at the end > of > > | the dynamic string table. If DT_SUNW_STRPAD is not present in an > > | object, no reserved space is available. > > > > Would that help in your case as well? > > > > The problem is that for two different build I pass two different > -Wl,--rpath=<path>, and they are of different length. So I'd like to > reserve a maximum size, at link-time, which becomes the same in both > builds, so that when I later remove the rpath's, the binaries become > identical. > > Jacob >
