Export some more useful info about shared memory objects to userland

via procstat(1) and fstat(1):
- Change shm file descriptors to track the pathname they are associated
  with and add a shm_path() method to copy the path out to a caller-supplied
  buffer.
- Use the fo_stat() method of shared memory objects and shm_path() to
  export the path, mode, and size of a shared memory object via
  struct kinfo_file.
- Add a struct shmstat to the libprocstat(3) interface along with a
  procstat_get_shm_info() to export the mode and size of a shared memory
  object.
- Change procstat to always print out the path for a given object if it
  is valid.
- Teach fstat about shared memory objects and to display their path,
  mode, and size.

MFC after:	2 weeks

1 files changed, 28 insertions, 0 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 18fd937..251a558 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -58,6 +58,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
+#include <sys/mman.h>
 #include <sys/mount.h>
 #include <sys/mqueue.h>
 #include <sys/mutex.h>
@@ -126,6 +127,7 @@ static int	fill_pts_info(struct tty *tp, struct kinfo_file *kif);
 static int	fill_pipe_info(struct pipe *pi, struct kinfo_file *kif);
 static int	fill_procdesc_info(struct procdesc *pdp,
     struct kinfo_file *kif);
+static int	fill_shm_info(struct file *fp, struct kinfo_file *kif);
 
 /*
  * A process is initially started out with NDFILE descriptors stored within
@@ -2958,6 +2960,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 	struct kinfo_ofile *kif;
 	struct filedesc *fdp;
 	int error, i, *name;
+	struct shmfd *shmfd;
 	struct socket *so;
 	struct vnode *vp;
 	struct file *fp;
@@ -2995,6 +2998,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 		vp = NULL;
 		so = NULL;
 		tp = NULL;
+		shmfd = NULL;
 		kif->kf_fd = i;
 
 #ifdef CAPABILITIES
@@ -3046,6 +3050,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 
 		case DTYPE_SHM:
 			kif->kf_type = KF_TYPE_SHM;
+			shmfd = fp->f_data;
 			break;
 
 		case DTYPE_SEM:
@@ -3159,6 +3164,8 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 			strlcpy(kif->kf_path, tty_devname(tp),
 			    sizeof(kif->kf_path));
 		}
+		if (shmfd != NULL)
+			shm_path(shmfd, kif->kf_path, sizeof(kif->kf_path));
 		error = SYSCTL_OUT(req, kif, sizeof(*kif));
 		if (error)
 			break;
@@ -3229,6 +3236,9 @@ export_fd_for_sysctl(void *data, int type, int fd, int fflags, int refcnt,
 	case KF_TYPE_PROCDESC:
 		error = fill_procdesc_info((struct procdesc *)data, kif);
 		break;
+	case KF_TYPE_SHM:
+		error = fill_shm_info((struct file *)data, kif);
+		break;
 	default:
 		error = 0;
 	}
@@ -3398,6 +3408,7 @@ sysctl_kern_proc_filedesc(SYSCTL_HANDLER_ARGS)
 
 		case DTYPE_SHM:
 			type = KF_TYPE_SHM;
+			data = fp;
 			break;
 
 		case DTYPE_SEM:
@@ -3621,6 +3632,23 @@ fill_procdesc_info(struct procdesc *pdp, struct kinfo_file *kif)
 	return (0);
 }
 
+static int
+fill_shm_info(struct file *fp, struct kinfo_file *kif)
+{
+	struct thread *td;
+	struct stat sb;
+
+	td = curthread;
+	if (fp->f_data == NULL)
+		return (1);
+	if (fo_stat(fp, &sb, td->td_ucred, td) != 0)
+		return (1);
+	shm_path(fp->f_data, kif->kf_path, sizeof(kif->kf_path));
+	kif->kf_un.kf_file.kf_file_mode = sb.st_mode;
+	kif->kf_un.kf_file.kf_file_size = sb.st_size;
+	return (0);
+}
+
 static SYSCTL_NODE(_kern_proc, KERN_PROC_FILEDESC, filedesc, CTLFLAG_RD,
     sysctl_kern_proc_filedesc, "Process filedesc entries");