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.

As with the previous commit, accept() was calling inner_get_name() and
assuming only "tcp:" or "udp:" addresses would be received. Thus, in
order to support AF_UNIX sockets, inner_get_name() was split into two,
inner_af_inet() and inner_af_unix() - where the former keeps the
previous logic, dealing with "tcp:" and "udp:" addresses, and the latter
deals now with "chan:" addresses and filling in the sockaddr_un
appropriately.

Previously, domain AF_INET was assumed while processing bind() /
connect(), which end up calling bind_or_connect!. Instead, match on the
domain type and process the path for AF_UNIX domains.

To add support for UNIX sockets (AF_UNIX), of SOCK_STREAM type, the
"chan:" scheme is used, which will be supportedby the ipcd running in
userspace.

Later commits add similar AF_UNIX support for the rest of the methods in
impl PalSocket.

Future commits will make use of this, in order to support AF_UNIX
sockets.

AdminXVII authored 5 years ago and Jeremy Soller committed 5 years ago

mem::uninitialized is deprecated, so move over the not-UB MaybeUninit.

needed for ssize_t

libiconv expects program_invocation_name to be an lvalue