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

sys/compat/linprocfs/linprocfs.c

@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/blist.h>
 #include <sys/conf.h>
 #include <sys/exec.h>
+#include <sys/fcntl.h>
 #include <sys/filedesc.h>
 #include <sys/jail.h>
 #include <sys/kernel.h>

sys/compat/linux/linux_uid16.c

@@ -29,6 +29,7 @@ __FBSDID("$FreeBSD$");
 
 #include "opt_compat.h"
 
+#include <sys/fcntl.h>
 #include <sys/param.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/compat/linux/linux_util.c

@@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/bus.h>
+#include <sys/fcntl.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/linker_set.h>

sys/compat/pecoff/imgact_pecoff.c

@@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/fcntl.h>
 #include <sys/imgact.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/compat/svr4/svr4_sysvec.c

@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysent.h>
 #include <sys/imgact.h>
 #include <sys/imgact_elf.h>
+#include <sys/fcntl.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/module.h>

sys/fs/coda/coda_vfsops.c

@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/conf.h>
+#include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/fs/msdosfs/msdosfs_vfsops.c

@@ -52,6 +52,7 @@
 #include <sys/systm.h>
 #include <sys/buf.h>
 #include <sys/conf.h>
+#include <sys/fcntl.h>
 #include <sys/iconv.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>

sys/fs/nullfs/null_vfsops.c

@@ -42,6 +42,7 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/fs/unionfs/union_vfsops.c

@@ -39,6 +39,7 @@
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/kdb.h>
+#include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/i386/ibcs2/ibcs2_util.c

@@ -32,6 +32,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <sys/fcntl.h>
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/syscallsubr.h>

sys/i386/linux/linux_sysvec.c

@@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/exec.h>
+#include <sys/fcntl.h>
 #include <sys/imgact.h>
 #include <sys/imgact_aout.h>
 #include <sys/imgact_elf.h>

sys/kern/kern_jail.c

@@ -22,6 +22,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/priv.h>
 #include <sys/proc.h>
 #include <sys/taskqueue.h>
+#include <sys/fcntl.h>
 #include <sys/jail.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>

sys/kern/vfs_acl.c

@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/sysproto.h>
+#include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/malloc.h>
 #include <sys/mount.h>

sys/kern/vfs_extattr.c

@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mount.h>
 #include <sys/mutex.h>
 #include <sys/sysproto.h>
+#include <sys/fcntl.h>
 #include <sys/namei.h>
 #include <sys/filedesc.h>
 #include <sys/limits.h>

sys/kern/vfs_lookup.c

@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/kernel.h>
+#include <sys/fcntl.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/namei.h>
@@ -192,10 +193,29 @@ namei(struct nameidata *ndp)
 	ndp->ni_rootdir = fdp->fd_rdir;
 	ndp->ni_topdir = fdp->fd_jdir;
 
-	dp = fdp->fd_cdir;
+	if (cnp->cn_pnbuf[0] != '/' && ndp->ni_dirfd != AT_FDCWD) {
+		error = fgetvp(td, ndp->ni_dirfd, &dp);
+		FILEDESC_SUNLOCK(fdp);
+		if (error == 0 && dp->v_type != VDIR) {
+			vfslocked = VFS_LOCK_GIANT(dp->v_mount);
+			vrele(dp);
+			VFS_UNLOCK_GIANT(vfslocked);
+			error = ENOTDIR;
+		}
+		if (error) {
+			uma_zfree(namei_zone, cnp->cn_pnbuf);
+#ifdef DIAGNOSTIC
+			cnp->cn_pnbuf = NULL;
+			cnp->cn_nameptr = NULL;
+#endif
+			return (error);
+		}
+	} else {
+		dp = fdp->fd_cdir;
+		VREF(dp);
+		FILEDESC_SUNLOCK(fdp);
+	}
 	vfslocked = VFS_LOCK_GIANT(dp->v_mount);
-	VREF(dp);
-	FILEDESC_SUNLOCK(fdp);
 	for (;;) {
 		/*
 		 * Check if root directory should replace current directory.

sys/kern/vfs_mount.c

@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/conf.h>
 #include <sys/clock.h>
+#include <sys/fcntl.h>
 #include <sys/jail.h>
 #include <sys/kernel.h>
 #include <sys/libkern.h>

sys/security/mac/mac_syscalls.c

@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include "opt_mac.h"
 
 #include <sys/param.h>
+#include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>

sys/sys/namei.h

@@ -69,6 +69,7 @@ struct nameidata {
 	struct	vnode *ni_startdir;	/* starting directory */
 	struct	vnode *ni_rootdir;	/* logical root directory */
 	struct	vnode *ni_topdir;	/* logical top directory */
+	int	ni_dirfd;		/* starting directory for *at functions */
 	/*
 	 * Results: returned from/manipulated by lookup
 	 */
@@ -148,19 +149,22 @@ struct nameidata {
 /*
  * Initialization of a nameidata structure.
  */
-static void NDINIT(struct nameidata *, u_long, u_long, enum uio_seg,
-	    const char *, struct thread *);
+#define	NDINIT(ndp, op, flags, segflg, namep, td)	\
+	NDINIT_AT(ndp, op, flags, segflg, namep, AT_FDCWD, td)
+
 static __inline void
-NDINIT(struct nameidata *ndp,
+NDINIT_AT(struct nameidata *ndp,
 	u_long op, u_long flags,
 	enum uio_seg segflg,
 	const char *namep,
+	int dirfd,
 	struct thread *td)
 {
 	ndp->ni_cnd.cn_nameiop = op;
 	ndp->ni_cnd.cn_flags = flags;
 	ndp->ni_segflg = segflg;
 	ndp->ni_dirp = namep;
+	ndp->ni_dirfd = dirfd;
 	ndp->ni_cnd.cn_thread = td;
 }
 

sys/ufs/ffs/ffs_snapshot.c

@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
+#include <sys/fcntl.h>
 #include <sys/proc.h>
 #include <sys/namei.h>
 #include <sys/sched.h>