Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Implement the linux syscalls
openat, mkdirat, mknodat, fchownat, futimesat, fstatat, unlinkat,
renameat, linkat, symlinkat, readlinkat, fchmodat, faccessat.

Submitted by: rdivacky
Sponsored by: Google Summer of Code 2007
Tested by: pho

Add the support for the AT_FDCWD and fd-relative name lookups to the
namei(9).

Based on the submission by rdivacky,
sponsored by Google Summer of Code 2007
Reviewed by: rwatson, rdivacky
Tested by: pho

- Implement ibcs2_emul_find() using kern_alternate_path(). This changes
the semantics in that the returned filename to use is now a kernel
pointer rather than a user space pointer. This required changing the
arguments to the CHECKALT*() macros some and changing the various system
calls that used pathnames to use the kern_foo() functions that can accept
kernel space filename pointers instead of calling the system call
directly.
- Use kern_open(), kern_access(), kern_execve(), kern_mkfifo(), kern_mknod(),
kern_setitimer(), kern_getrusage(), kern_utimes(), kern_unlink(),
kern_chdir(), kern_chmod(), kern_chown(), kern_symlink(), kern_readlink(),
kern_select(), kern_statfs(), kern_fstatfs(), kern_stat(), kern_lstat(),
kern_fstat().
- Drop the unused 'uap' argument from spx_open().
- Replace a stale duplication of vn_access() in xenix_access() lacking
recent additions such as MAC checks, etc. with a call to kern_access().

/* -> /*- for license, add FreeBSD tag

Fix a multitude of security bugs in the iBCS2 emulator:
- Return NULL instead of returning memory outside of the stackgap
in stackgap_alloc() (FreeBSD-SA-00:42.linux)
- Check for stackgap_alloc() returning NULL in ibcs2_emul_find();
other calls to stackgap_alloc() have not been changed since they
are small fixed-size allocations.
- Replace use of strcpy() with strlcpy() in exec_coff_imgact()
to avoid buffer overflow
- Use strlcat() instead of strcat() to avoid a one byte buffer
overflow in ibcs2_setipdomainname()
- Use copyinstr() instead of copyin() in ibcs2_setipdomainname()
to ensure that the string is null-terminated
- Avoid integer overflow in ibcs2_setgroups() and ibcs2_setgroups()
by checking that gidsetsize argument is non-negative and
no larger than NGROUPS_MAX.
- Range-check signal numbers in ibcs2_wait(), ibcs2_sigaction(),
ibcs2_sigsys() and ibcs2_kill() to avoid accessing array past
the end (or before the start)

Use __FBSDID().

Back out M_* changes, per decision of the TRB.

Approved by: trb

Remove M_TRYWAIT/M_WAITOK/M_WAIT. Callers should use 0.
Merge M_NOWAIT/M_DONTWAIT into a single flag M_NOWAIT.

Simple p_ucred -> td_ucred changes to start using the per-thread ucred
reference.

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

Fix typo: seperate -> separate.

Seperate does not exist in the english language.

Back out proc locking to protect p_ucred for obtaining additional
references along with the actual obtaining of additional references.

Proc locking.

Remove unneeded #include <vm/vm_zone.h>

Generated by: src/tools/tools/kerninclude

Introduce NDFREE (and remove VOP_ABORTOP)

Removed unused #includes.

Don't include <sys/ioctl.h> in the kernel. Stage 1: don't include
it when it is not used. In most cases, the reasons for including it
went away when the special ioctl headers became self-sufficient.

Changed type of ni_dirp in `struct namei' from caddr_t to `const char *'
so that the compiler can see that it is OK to use const strings in
NDINIT(). Some emulators want to use paths of the form "/compat/foo".
Removed the casts that hid the non-problem. Didn't fix the missing
consts in syscalls.master that hid the non-problem.

Change alternate space base name from /emul/ibcs2 to /compat/ibcs2,
in line with linux alt space of /compat/linux.
This was pointed out by Stefan Esser.

In cheching alt space for libraries in imgact_coff.c, use const
ibcs2_emul_path instead of its own local string. Also do a proper
malloc of temp name according to MAXPATHLEN.

Remove old files no longer needed.
Add new files created for emulator.
Modify NetBSD import to work with FreeBSD and add new features and
code. The complete emulator is essentially a combination of work/code
implemented by Sean Eric Fagan, Soren Schmidt, Scott Bartram, and myself,
Steven Wallace.

Features of this new emulator system include:

o "clean" code, including strict prototyping.
o Auto-generation of ibcs2 system calls, xenix system calls, isc system
calls. Generation includes system tables, structure definitions,
and prototyping of function calls.
o ibcs2 emulator does not rely on any COMPAT_43 system calls.
o embedded socksys support
o ibcs2 msgsys, semsys, shmsys calls supported if supported in kernel
o alternate /emul/ibcs2 namespace searched first for files in ibcs2
system. Usefull to keep sysv libraries, binaries in /emul/ibcs2.
o many other finer details and functions fixed or implemented.

This commit was generated by cvs2svn to compensate for changes in r11394,
which included commits to RCS files with non-trunk default branches.

Import of original NetBSD's ibcs2 emulator sources by Scott Bartram,
which is used as a basis for a more complete and cleaner ibcs2 emulator.
(snapshot about May 1995 with a few files from September 1995)

Some files and code from old emulator still remains.
New files, features, and changes have been implemented by myself,
which will be shown in following commits.