this is mostly useless for shared libs (though it could help for
prelink-like purposes); the intended use case is for adding support
for calling the dynamic linker directly to run a program, as in:
./libc.so ./a.out foo
this usage is not yet supported.
basically we temporarily make the library and all its dependencies
part of the global namespace but only for the duration of performing
relocations, then return them to their former state.
some of the code is not yet used, and is in preparation for dlopen
which needs to be able to handle failure loading libraries without
terminating the program.
the use of this test will be much stricter than glibc and other
typical implementations; the environment will not be honored
whatsoever unless the program is confirmed non-suid/sgid by the aux
vector the kernel passed in. no fallback to slow syscall-based
checking is used if the kernel fails to provide the information; we
simply assume the worst (suid) in this case and refuse to honor
environment.
some notes:
- library search path is hard coded
- x86_64 code is untested and may not work
- dlopen/dlsym is not yet implemented
- relocations in read-only memory won't work
Rich Felker