Previously dlsym resolved to the version in crt0.o or libc which would
mean that the caller's shared object couldn't be determined correctly
using __builtin_return_address(0).
Mainly from FreeBSD, but adapted by me. Benefits of this solutions are:
- backward comptibility maintained
- existing broken binaries are fixed with a new ld.elf_so
- __mainprog_obj can be removed from crt0.o
- we do the same thing as FreeBSD
Fixes PR 22067.
OKed by Jason and Christos.
and utilize it. This greatly reduces the number of calls to open(2) and
malloc(3) for programs like mozilla that depend on many shared objects
while it doesn't affect performance of small programs.
* Rename _rtld_find_library() to _rtld_load_library(). It now calls
_rtld_load_object() if necessary to actually load the object, rather
than having the caller do it. To do this, it also takes the `mode'
argument that gets passed to _rtld_load_object().
* On a related note, remove _rtld_check_library(), and instead call
_rtld_load_object() to instead try actually loading the object. We
save two extra namei's and a bunch of redundant work (almost
literally the same code) this way.
* In _rtld_map_object(), mmap(2) the first page read-only, rather than
read(2)ing it.
* In _rtld_symlook_obj(), compare the *second* character of the symbol
name before calling strcmp(). (This first character is too
frequently `_', and turns out to not be helpful, in libc.)
* Also in _rtld_symlook_obj(), remove the bogus STT_FUNC special case
-- this also allows removing the `in_plt' argument to
_rtld_symlook_list() and _rtld_symlook_obj().
Also:
* In _rtld_obj_from_addr(), rather than trying to look up `_end' in
the each object, instead use obj->mapsize as the upper bound.
runpath > built-in default; this is the behaviour of the SVR4 shared loader,
and gives users the opportunity to override the runpath. (Addresses a report
on current-users by John Kohl.)
kit, then hacked on by Matt Thomas <matt@3am-software.com>, then by me (to
make it work with new versions of the toolchain, etc.). This runs, but it's
in serious need of cleaning and/or a fair bit of reworking. See the README
file for more information, and a list of things to do.
