Richard Sandiford <rdsandiford@xxxxxxxxxxxxxx> writes: > MIPS multigots are a trick. The ABI only defines a single GOT, > which I'll call the "ABI-defined" GOT. As you say, this GOT needs > no relocations. The information is instead provided in two ways: > > (a) Dymamic tags give the limits of the local and global parts > of the GOT. > > (b) The global part of the GOT is directly mapped to the end > of the dynamic symbol table. > > But what do you do if you need multiple GOTs, and several GOTs > need to refer to the same symbol S? S appears only once in the > dynamic symbol table, so it can only appear once in the ABI-defined GOT. > > Multigots could only share GOT entries like this if you were able to > sort the symbols in such a way that every multigot represented a 64k > (or smaller) window into the ABI-defined GOT. And that isn't possible > in the general case. Objects often refer to both common symbols (like > stdio routines) and object-specific symbols. Once you get >128k of > object-specific symbols, it isn't possible for all of them to be in > a 64k window that also contains the ABI GOT entries for the stdio > routines. I forgot an even more important restriction: the local part of the ABI-defined GOT has to come before the global part. In practice, almost all GOTs have some local entries, so this would restrict the windows even further. Richard
