On Mon 20 May 2013 18:37, l...@gnu.org (Ludovic Courtès) writes: > Andy Wingo <wi...@pobox.com> skribis: > >> On Sun 19 May 2013 23:52, l...@gnu.org (Ludovic Courtès) writes: >> >>> I guess literal strings would go out as per ‘SCM_IMMUTABLE_STRING’ >>> (which needs relocation), right? >> >> Yep. Right now the stringbuf goes into read-only memory, but the string >> itself goes in writable memory as it needs its link to the stringbuf >> fixed up (relocated) at runtime. > > OK. It could be in a PT_GNU_RELRO segment, which the loader (well, the > other one, from glibc ;-)) remaps read-only after relocation. > > [A moment of enlightenment when one realizes what it means to have our > own ELF toolchain. :-)]
Right :) We don't need to rely on the loader, and in fact should not in general do so. Some "relocations" are actually more complicated than what glibc does; for example, for symbols or keywords. >> (I suppose we should be careful about embedded NUL characters; perhaps >> we should use some other format for the string tables.) > > NULs in string contents should not be a problem, as long as there’s > info somewhere about the string length, no? There isn't -- not in ELF string tables. They're NUL-terminated. > UTF-8-encoded ELF symbols may be more of a problem. How could NULs in > symbols be handled? Well we can just use some other data structure that's not a standard ELF string table; since we have the linker and loader and we are defining custom sections (.guile.docstrs for example) we can do what we like. A -- http://wingolog.org/
