Split the symlook_obj1 into a loop iterating over the ELF object symbol
hash elements, and a helper matched_symbol() which match the given hash
entry and request, performing needed type and version checks.

MFC r234841:
Add GNU hash support for rtld.

MFC r235054:
Work around a situation where symlook_obj() could be called for the
object for which digest_dynamic1() was not done yet. Just return
EINVAL and do not try to dereference NULL buckets hash array.

Remove superfluous extern keywords.

Use xmalloc() instead of malloc() in the places where malloc() calls
are assumed to not fail.

Make the xcalloc() calling conventions follow the calloc(3) calling
conventions and replace unchecked calls to calloc() with calls to
xcalloc().

Remove redundand declarations from xmalloc.c, which are already
present in rtld.h.

Prevent rtld_verify_object_versions() from being called several times
for the same object.

Fix several problems with our ELF filters implementation.

Do not relocate twice an object which happens to be needed by loaded
binary (or dso) and some filtee opened due to symbol resolution when
relocating need objects.  Record the state of the relocation
processing in Obj_Entry and short-circuit relocate_objects() if
current object already processed.

Do not call constructors for filtees loaded during the early
relocation processing before image is initialized enough to run
user-provided code.  Filtees are loaded using dlopen_object(), which
normally performs relocation and initialization.  If filtee is
lazy-loaded during the relocation of dso needed by the main object,
dlopen_object() runs too earlier, when most runtime services are not
yet ready.

Postpone the constructors call to the time when main binary and
depended libraries constructors are run, passing the new flag
RTLD_LO_EARLY to dlopen_object().  Symbol lookups callers inform
symlook_* functions about early stage of initialization with
SYMLOOK_EARLY.  Pass flags through all functions participating in
object relocation.

Use the opportunity and fix flags argument to find_symdef() in
arch-specific reloc.c to use proper name SYMLOOK_IN_PLT instead of
true, which happen to have the same numeric value.

MFC r233777 (by kan):
Do not try to adjust stacks if dlopen_object is called too early.

MFC r233778 (by kan):
Remove extra blank line from revious commit.

MFC note: the ARM and MIPS TLS support is not merged back, so the chunks
from r233231 which fix misuse of flags in calls to find_symdef() in
the corresponding relocation type handlers were not applied. When TLS
support is merged, the rest of r233231 should be applied too.

Stop using strerror(3) in rtld, which brings in msgcat and stdio.
Directly access sys_errlist array of errno messages with private
rtld_strerror() function.

Add support for preinit, init and fini arrays to rtld.
Only binaries marked with proper ABI note gets array ctr/dtrs called.

MFC r232856:
When iterating over the dso program headers, the object is not initialized
yet, and object segments are not yet mapped.  Only parse the notes that
appear in the first page of the dso (as it should be anyway), and use
the preloaded page content.

MFC r232857 (by dim):
Fix a warning/error with clang.

MFC r232859 (by dim):
Amend r232857, now dropping the casts entirely, as they were not
necessary at all.

Add support for GNU RELRO.

Add support for STT_GNU_IFUNC and R_MACHINE_IRELATIVE GNU extensions to
rtld on 386 and amd64.

MFC r228503:
Postpone the resolution for irelative/ifunc right before initializers
are called, and drop bind lock around calls to dispatcher.  Use
initlist to iterate over the objects instead of the ->next, due to
drop of the bind lock in iteration.

For i386/reloc.c:reloc_iresolve(), fix calculation of the dispatch
function address for dso, by taking into account possible non-zero
relocbase.

MFC r228635 (by nwhitehorn):
Fix RTLD on PowerPC after r228435. Changing the order of init_pltgot()
caused the icache to be invalidated at the wrong time, resulting in
an icache full of nonsense in the PLT section.

Typo.