With this change, gcc can now successfully compile a tiny program that
printfs an integer returned from a function, from a dynamically linked
library that it compiled as well.
Rustc however, is orders of magnitude more complex, and the next step is
to fix constructors which require access to `environ`, in ld.so
Introduction:
The original implementation of `relibc_ld_so_start` assumes that
ld.so will always be invoked manually as in "/lib/ld64.so ./a.out"
The problem is regarding this snippet.
if sp.argc < 2 {
eprintln!("ld.so [executable] [arguments...]");
unistd::_exit(1);
loop {}
}
As such, In linux when user types "./a.out" he will recieve the message
ld.so [executable] [arguments...]
This patch makes use of AUXV, specifically AT_ENTRY. When invoking ld.so
manually, AT_ENTRY happens to be the entry point of ld.so. But when
running `./a.out` directly, AT_ENTRY becomes the entry point of `a.out`
this patch compares AT_ENTRY to the entry point of ld.so, if they are
equal only then it will assume that argv[1] is the real program and
adjust the stack, otherwise it will proceed with the stack unadjusted.
auronandace