lib: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

libc: Purge unneeded cdefs.h

These sys/cdefs.h are not needed. Purge them. They are mostly left-over
from the $FreeBSD$ removal. A few in libc are still required for macros
that cdefs.h defines. Keep those.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D42385

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

General further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Switch libc from using _sig{procmask,action,suspend} symbols, which
are aliases for the syscall stubs and are plt-interposed, to the
libc-private aliases of internally interposed sigprocmask() etc.

Since e.g. _sigaction is not interposed by libthr, calling signal()
removes thr_sighandler() from the handler slot etc. The result was
breaking signal semantic and rtld locking.

The added __libc_sigprocmask and other symbols are hidden, they are
not exported and cannot be called through PLT. The setjmp/longjmp
functions for x86 were changed to use direct calls, and since
PIC_PROLOGUE only needed for functional PLT indirection on i386, it is
removed as well.

The PowerPC bug of calling the syscall directly in the setjmp/longjmp
implementation is kept as is.

Reported by: Pete French <petefrench@ingresso.co.uk>
Tested by: Michiel Boland <boland37@xs4all.nl>
Reviewed by: jilles (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Fix known issues which blow up the process after dlopen("libthr.so")
(or loading a dso linked to libthr.so into process which was not
linked against threading library).

- Remove libthr interposers of the libc functions, including
__error(). Instead, functions calls are indirected through the
interposing table, similar to how pthread stubs in libc are already
done. Libc by default points either to syscall trampolines or to
existing libc implementations. On libthr load, libthr rewrites the
pointers to the cancellable implementations already in libthr. The
interposition table is separate from pthreads stubs indirection
table to not pull pthreads stubs into static binaries.

- Postpone the malloc(3) internal mutexes initialization until libthr
is loaded. This avoids recursion between calloc(3) and static
pthread_mutex_t initialization.

- Reinstall signal handlers with wrapper on libthr load. The
_rtld_is_dlopened(3) is used to avoid useless calls to sigaction(2)
when libthr is statically referenced from the main binary.

In the process, fix openat(2), swapcontext(2) and setcontext(2)
interposing. The libc symbols were exported at different versions
than libthr interposers. Export both libc and libthr versions from
libc now, with default set to the higher version from libthr.

Remove unused and disconnected swapcontext(3) userspace implementation
from libc/gen.

No objections from: deischen
Tested by: pho, antoine (exp-run) (previous versions)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

system(): Restore behaviour for SIGINT and SIGQUIT.

As mentioned in r16117 and the book "Advanced Programming in the Unix
Environment" by W. Richard Stevens, we should ignore SIGINT and SIGQUIT
before forking, since it is not guaranteed that the parent process starts
running soon enough.

To avoid calling sigaction() in the vforked child, instead block SIGINT and
SIGQUIT before vfork() and keep the sigaction() to ignore after vfork(). The
FreeBSD kernel discards ignored signals, even if they are blocked;
therefore, it is not necessary to unblock SIGINT and SIGQUIT earlier.

vfork(2) was listed as deprecated in 1994 (r1573) and was the false
reports of its impending demise were removed in 2009 (r199257).

However, in 1996 (r16117) system(3) was switched from vfork(2) to
fork(2) based partly on this. Switch back to vfork(2). This has a
dramatic effect in cases of extreme mmap use - such as excessive
abuse (500+) of shared libraries.

popen(3) has used vfork(2) for a while. vfork(2) isn't going anywhere.

Renumber clauses to reduce diffs to other versions

NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3,
so follow suit to make comparison easier.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

Fix many "function declaration isn't a prototype" warnings in libc.

I've only fixed code that seems to be written by `us'. There are still
many warnings like this present in resolv/, rpc/, stdtime/ and yp/.

- Import the HEAD csup code which is the basis for the cvsmode work.

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

Fix the style of the SCM ID's.
I believe have made all of libc .c's as consistent as possible.

Avoid getting stuck in system(3) when the internal call to wait4()
is interrupted by saving the pid.

The old code would assign the return value to pid which would trash
it, to fix the problem save a copy of the pid to be used as the
paramter to wait4().

Submitted by: Toshihiko ARAI <toshi@jp.FreeBSD.org>

Remove _THREAD_SAFE and make libc thread-safe by default by
adding (weak definitions to) stubs for some of the pthread
functions. If the threads library is linked in, the real
pthread functions will pulled in.

Use the following convention for system calls wrapped by the
threads library:
__sys_foo - actual system call
_foo - weak definition to __sys_foo
foo - weak definition to __sys_foo

Change all libc uses of system calls wrapped by the threads
library from foo to _foo. In order to define the prototypes
for _foo(), we introduce namespace.h and un-namespace.h
(suggested by bde). All files that need to reference these
system calls, should include namespace.h before any standard
includes, then include un-namespace.h after the standard
includes and before any local includes. <db.h> is an exception
and shouldn't be included in between namespace.h and
un-namespace.h namespace.h will define foo to _foo, and
un-namespace.h will undefine foo.

Try to eliminate some of the recursive calls to MT-safe
functions in libc/stdio in preparation for adding a mutex
to FILE. We have recursive mutexes, but would like to avoid
using them if possible.

Remove uneeded includes of <errno.h> from a few files.

Add $FreeBSD$ to a few files in order to pass commitprep.

Approved by: -arch

Take care to avoid having "strong" and "weak" symbols of the same name in
libc_r.

Simplify sytem call renaming. Instead of _foo() <-- _libc_foo <-- foo(),
just use _foo() <-- foo(). In the case of a libpthread that doesn't do
call conversion (such as linuxthreads and our upcoming libpthread), this
is adequate. In the case of libc_r, we still need three names, which are
now _thread_sys_foo() <-- _foo() <-- foo().

Convert all internal libc usage of: aio_suspend(), close(), fsync(), msync(),
nanosleep(), open(), fcntl(), read(), and write() to _foo() instead of foo().

Remove all internal libc usage of: creat(), pause(), sleep(), system(),
tcdrain(), wait(), and waitpid().

Make thread cancellation fully POSIX-compliant.

Suggested by: deischen

Add three-tier symbol naming in support of POSIX thread cancellation
points. For library functions, the pattern is __sleep() <--
_libc_sleep() <-- sleep(). The arrows represent weak aliases. For
system calls, the pattern is _read() <-- _libc_read() <-- read().

Oops, replace a rather important line that was lost in transit 8-(

Submitted by: (based on code in "Advanced Programming in the Unix Environment"
by W.Richard Ste vens. EINTR handling suggested by bde@freebsd.org).

Code cleanup:

1. Add missing return type.
2. Replace 'union wait' by int.
3. Use Posix-style signal handling instead of signal().
4. Use fork() instead of deprecated vfork().
5. Block signals before fork()'ing, instead of after.
6. Return -1 if fork() fails, instead of 0.
7. Add EINTR handling for waitpid() call.

Also add claim of Posix conformance to man page.

BSD 4.4 Lite Lib Sources