Make procstat(1) recognize process descriptors, so that it shows

"P" instead of "?" in "procstat -af" output. Note that there are
still a few more DTYPE_* kinds we don't decode yet.

Reported by:	rwatson
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D12426

lib/libprocstat/libprocstat.c

@@ -582,6 +582,10 @@ procstat_getfiles_kvm(struct procstat *procstat, struct kinfo_proc *kp, int mmap
 			type = PS_FST_TYPE_SHM;
 			data = file.f_data;
 			break;
+		case DTYPE_PROCDESC:
+			type = PS_FST_TYPE_PROCDESC;
+			data = file.f_data;
+			break;
 		default:
 			continue;
 		}
@@ -665,6 +669,7 @@ kinfo_type2fst(int kftype)
 		int	kf_type;
 		int	fst_type;
 	} kftypes2fst[] = {
+		{ KF_TYPE_PROCDESC, PS_FST_TYPE_PROCDESC },
 		{ KF_TYPE_CRYPTO, PS_FST_TYPE_CRYPTO },
 		{ KF_TYPE_FIFO, PS_FST_TYPE_FIFO },
 		{ KF_TYPE_KQUEUE, PS_FST_TYPE_KQUEUE },

lib/libprocstat/libprocstat.h

@@ -68,6 +68,7 @@
 #define	PS_FST_TYPE_SEM		10
 #define	PS_FST_TYPE_UNKNOWN	11
 #define	PS_FST_TYPE_NONE	12
+#define	PS_FST_TYPE_PROCDESC	13
 
 /*
  * Special descriptor numbers.

usr.bin/procstat/procstat.1

@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 26, 2017
+.Dd October 3, 2017
 .Dt PROCSTAT 1
 .Os
 .Sh NAME
@@ -212,6 +212,8 @@ shared memory
 kqueue
 .It m
 message queue
+.It P
+process descriptor
 .It p
 pipe
 .It s

usr.bin/procstat/procstat_files.c

@@ -400,6 +400,11 @@ procstat_files(struct procstat *procstat, struct kinfo_proc *kipp)
 			xo_emit("{eq:fd_type/sem}");
 			break;
 
+		case PS_FST_TYPE_PROCDESC:
+			str = "P";
+			xo_emit("{eq:fd_type/procdesc}");
+			break;
+
 		case PS_FST_TYPE_NONE:
 			str = "?";
 			xo_emit("{eq:fd_type/none}");