Add support for displaying a process' current working directory, root

directory, and jail directory within procstat.  While this functionality
is available already in fstat, encapsulating it in the kern.proc.filedesc
sysctl makes it accessible without using kvm and thus without needing
elevated permissions.

The new procstat output looks like:

  PID COMM               FD T V FLAGS    REF  OFFSET PRO NAME
  76792 tcsh              cwd v d --------   -       - -   /usr/src
  76792 tcsh             root v d --------   -       - -   /
  76792 tcsh               15 v c rw------  16    9130 -   -
  76792 tcsh               16 v c rw------  16    9130 -   -
  76792 tcsh               17 v c rw------  16    9130 -   -
  76792 tcsh               18 v c rw------  16    9130 -   -
  76792 tcsh               19 v c rw------  16    9130 -   -

I am also bumping __FreeBSD_version for this as this new feature will be
used in at least one port.

Reviewed by:	rwatson
Approved by:	rwatson

4 files changed, 82 insertions, 6 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 4914804..7e53062 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -2446,6 +2446,47 @@ sysctl_kern_file(SYSCTL_HANDLER_ARGS)
 SYSCTL_PROC(_kern, KERN_FILE, file, CTLTYPE_OPAQUE|CTLFLAG_RD,
     0, 0, sysctl_kern_file, "S,xfile", "Entire file table");
 
+static int
+export_vnode_for_sysctl(struct vnode *vp, int type,
+    struct kinfo_file *kif, struct filedesc *fdp, struct sysctl_req *req)
+{
+	int error;
+	char *fullpath, *freepath;
+	int vfslocked;
+
+	bzero(kif, sizeof(*kif));
+	kif->kf_structsize = sizeof(*kif);
+
+	vref(vp);
+	kif->kf_fd = type;
+	kif->kf_type = KF_TYPE_VNODE;
+	/* This function only handles directories. */
+	KASSERT(vp->v_type == VDIR, ("export_vnode_for_sysctl: vnode not directory"));
+	kif->kf_vnode_type = KF_VTYPE_VDIR;
+
+	/*
+	 * This is not a true file descriptor, so we set a bogus refcount
+	 * and offset to indicate these fields should be ignored.
+	 */
+	kif->kf_ref_count = -1;
+	kif->kf_offset = -1;
+
+	freepath = NULL;
+	fullpath = "-";
+	FILEDESC_SUNLOCK(fdp);
+	vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+	vn_fullpath(curthread, vp, &fullpath, &freepath);
+	vput(vp);
+	VFS_UNLOCK_GIANT(vfslocked);
+	strlcpy(kif->kf_path, fullpath, sizeof(kif->kf_path));
+	if (freepath != NULL)
+		free(freepath, M_TEMP);
+	error = SYSCTL_OUT(req, kif, sizeof(*kif));
+	FILEDESC_SLOCK(fdp);
+	return (error);
+}
+
 /*
  * Get per-process file descriptors for use by procstat(1), et al.
  */
@@ -2473,6 +2514,15 @@ sysctl_kern_proc_filedesc(SYSCTL_HANDLER_ARGS)
 	PROC_UNLOCK(p);
 	kif = malloc(sizeof(*kif), M_TEMP, M_WAITOK);
 	FILEDESC_SLOCK(fdp);
+	if (fdp->fd_cdir != NULL)
+		export_vnode_for_sysctl(fdp->fd_cdir, KF_FD_TYPE_CWD, kif,
+				fdp, req);
+	if (fdp->fd_rdir != NULL)
+		export_vnode_for_sysctl(fdp->fd_rdir, KF_FD_TYPE_ROOT, kif,
+				fdp, req);
+	if (fdp->fd_jdir != NULL)
+		export_vnode_for_sysctl(fdp->fd_jdir, KF_FD_TYPE_JAIL, kif,
+				fdp, req);
 	for (i = 0; i < fdp->fd_nfiles; i++) {
 		if ((fp = fdp->fd_ofiles[i]) == NULL)
 			continue;
diff --git a/sys/sys/param.h b/sys/sys/param.h
index a7ff20a..1a21dc2 100644
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -57,7 +57,7 @@
  *		is created, otherwise 1.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 800018	/* Master, propagated to newvers */
+#define __FreeBSD_version 800019	/* Master, propagated to newvers */
 
 #ifndef LOCORE
 #include <sys/types.h>
diff --git a/sys/sys/user.h b/sys/sys/user.h
index 8177b1b..5595476 100644
--- a/sys/sys/user.h
+++ b/sys/sys/user.h
@@ -234,7 +234,7 @@ struct user {
 };
 
 /*
- * The KERN_PROC_FILE sysctl allows a process to dumpt the file descriptor
+ * The KERN_PROC_FILE sysctl allows a process to dump the file descriptor
  * array of another process.
  */
 #define	KF_TYPE_NONE	0
@@ -259,6 +259,10 @@ struct user {
 #define	KF_VTYPE_VBAD	8
 #define	KF_VTYPE_UNKNOWN	255
 
+#define	KF_FD_TYPE_CWD	-1	/* Current working directory */
+#define	KF_FD_TYPE_ROOT	-2	/* Root directory */
+#define	KF_FD_TYPE_JAIL	-3	/* Jail directory */
+
 #define	KF_FLAG_READ		0x00000001
 #define	KF_FLAG_WRITE		0x00000002
 #define	KF_FLAG_APPEND		0x00000004
diff --git a/usr.bin/procstat/procstat_files.c b/usr.bin/procstat/procstat_files.c
index 98e4ef6..950b70d 100644
--- a/usr.bin/procstat/procstat_files.c
+++ b/usr.bin/procstat/procstat_files.c
@@ -140,7 +140,7 @@ procstat_files(pid_t pid, struct kinfo_proc *kipp)
 	size_t len;
 
 	if (!hflag)
-		printf("%5s %-16s %3s %1s %1s %-8s %3s %7s %-3s %-12s\n",
+		printf("%5s %-16s %4s %1s %1s %-8s %3s %7s %-3s %-12s\n",
 		    "PID", "COMM", "FD", "T", "V", "FLAGS", "REF", "OFFSET",
 		    "PRO", "NAME");
 
@@ -172,7 +172,23 @@ procstat_files(pid_t pid, struct kinfo_proc *kipp)
 			errx(-1, "kinfo_file mismatch");
 		printf("%5d ", pid);
 		printf("%-16s ", kipp->ki_comm);
-		printf("%3d ", kif->kf_fd);
+		switch (kif->kf_fd) {
+		case KF_FD_TYPE_CWD:
+			printf(" cwd ");
+			break;
+
+		case KF_FD_TYPE_ROOT:
+			printf("root ");
+			break;
+
+		case KF_FD_TYPE_JAIL:
+			printf("jail ");
+			break;
+
+		default:
+			printf("%4d ", kif->kf_fd);
+			break;
+		}
 		switch (kif->kf_type) {
 		case KF_TYPE_VNODE:
 			str = "v";
@@ -264,8 +280,14 @@ procstat_files(pid_t pid, struct kinfo_proc *kipp)
 		printf("%s", kif->kf_flags & KF_FLAG_NONBLOCK ? "n" : "-");
 		printf("%s", kif->kf_flags & KF_FLAG_DIRECT ? "d" : "-");
 		printf("%s ", kif->kf_flags & KF_FLAG_HASLOCK ? "l" : "-");
-		printf("%3d ", kif->kf_ref_count);
-		printf("%7jd ", (intmax_t)kif->kf_offset);
+		if (kif->kf_ref_count > -1)
+			printf("%3d ", kif->kf_ref_count);
+		else
+			printf("%3c ", '-');
+		if (kif->kf_offset > -1)
+			printf("%7jd ", (intmax_t)kif->kf_offset);
+		else
+			printf("%7c ", '-');
 
 		switch (kif->kf_type) {
 		case KF_TYPE_VNODE: