Similar to 233760 and 236717, export some more useful info about the

kernel-based POSIX semaphore descriptors to userland via procstat(1) and
fstat(1):
- Change sem file descriptors to track the pathname they are associated
  with and add a ksem_info() method to copy the path out to a
  caller-supplied buffer.
- Use the fo_stat() method of shared memory objects and ksem_info() to
  export the path, mode, and value of a semaphore via struct kinfo_file.
- Add a struct semstat to the libprocstat(3) interface along with a
  procstat_get_sem_info() to export the mode and value of a semaphore.
- Teach fstat about semaphores and to display their path, mode, and value.

MFC after:	2 weeks

2 files changed, 49 insertions, 1 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index a9795ca..c0ecf15 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/filio.h>
 #include <sys/jail.h>
 #include <sys/kernel.h>
+#include <sys/ksem.h>
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
@@ -111,6 +112,7 @@ MALLOC_DECLARE(M_FADVISE);
 
 static uma_zone_t file_zone;
 
+void	(*ksem_info)(struct ksem *ks, char *path, size_t size, uint32_t *value);
 
 static int	closefp(struct filedesc *fdp, int fd, struct file *fp,
 		    struct thread *td, int holdleaders);
@@ -123,6 +125,7 @@ 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_pts_info(struct tty *tp, struct kinfo_file *kif);
+static int	fill_sem_info(struct file *fp, struct kinfo_file *kif);
 static int	fill_shm_info(struct file *fp, struct kinfo_file *kif);
 static int	fill_socket_info(struct socket *so, struct kinfo_file *kif);
 static int	fill_vnode_info(struct vnode *vp, struct kinfo_file *kif);
@@ -2968,6 +2971,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 	struct shmfd *shmfd;
 	struct socket *so;
 	struct vnode *vp;
+	struct ksem *ks;
 	struct file *fp;
 	struct proc *p;
 	struct tty *tp;
@@ -2996,6 +3000,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 			continue;
 		bzero(kif, sizeof(*kif));
 		kif->kf_structsize = sizeof(*kif);
+		ks = NULL;
 		vp = NULL;
 		so = NULL;
 		tp = NULL;
@@ -3041,6 +3046,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 
 		case DTYPE_SEM:
 			kif->kf_type = KF_TYPE_SEM;
+			ks = fp->f_data;
 			break;
 
 		case DTYPE_PTS:
@@ -3150,6 +3156,8 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS)
 		}
 		if (shmfd != NULL)
 			shm_path(shmfd, kif->kf_path, sizeof(kif->kf_path));
+		if (ks != NULL && ksem_info != NULL)
+			ksem_info(ks, kif->kf_path, sizeof(kif->kf_path), NULL);
 		error = SYSCTL_OUT(req, kif, sizeof(*kif));
 		if (error)
 			break;
@@ -3220,6 +3228,9 @@ export_fd_to_sb(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_SEM:
+		error = fill_sem_info((struct file *)data, kif);
+		break;
 	case KF_TYPE_SHM:
 		error = fill_shm_info((struct file *)data, kif);
 		break;
@@ -3387,6 +3398,7 @@ kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
 
 		case DTYPE_SEM:
 			type = KF_TYPE_SEM;
+			data = fp;
 			break;
 
 		case DTYPE_PTS:
@@ -3621,6 +3633,25 @@ fill_procdesc_info(struct procdesc *pdp, struct kinfo_file *kif)
 }
 
 static int
+fill_sem_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);
+	if (ksem_info == NULL)
+		return (1);
+	ksem_info(fp->f_data, kif->kf_path, sizeof(kif->kf_path),
+	    &kif->kf_un.kf_sem.kf_sem_value);
+	kif->kf_un.kf_sem.kf_sem_mode = sb.st_mode;
+	return (0);
+}
+
+static int
 fill_shm_info(struct file *fp, struct kinfo_file *kif)
 {
 	struct thread *td;
diff --git a/sys/kern/uipc_sem.c b/sys/kern/uipc_sem.c
index 509f32e..a9f60f1 100644
--- a/sys/kern/uipc_sem.c
+++ b/sys/kern/uipc_sem.c
@@ -71,7 +71,6 @@ FEATURE(p1003_1b_semaphores, "POSIX P1003.1B semaphores support");
  * TODO
  *
  * - Resource limits?
- * - Update fstat(1)
  * - Replace global sem_lock with mtx_pool locks?
  * - Add a MAC check_create() hook for creating new named semaphores.
  */
@@ -407,6 +406,7 @@ ksem_insert(char *path, Fnv32_t fnv, struct ksem *ks)
 	map->km_path = path;
 	map->km_fnv = fnv;
 	map->km_ksem = ksem_hold(ks);
+	ks->ks_path = path;
 	LIST_INSERT_HEAD(KSEM_HASH(fnv), map, km_link);
 }
 
@@ -428,6 +428,7 @@ ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
 			error = ksem_access(map->km_ksem, ucred);
 			if (error)
 				return (error);
+			map->km_ksem->ks_path = NULL;
 			LIST_REMOVE(map, km_link);
 			ksem_drop(map->km_ksem);
 			free(map->km_path, M_KSEM);
@@ -439,6 +440,20 @@ ksem_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
 	return (ENOENT);
 }
 
+static void
+ksem_info_impl(struct ksem *ks, char *path, size_t size, uint32_t *value)
+{
+
+	if (ks->ks_path == NULL)
+		return;
+	sx_slock(&ksem_dict_lock);
+	if (ks->ks_path != NULL)
+		strlcpy(path, ks->ks_path, size);
+	if (value != NULL)
+		*value = ks->ks_value;
+	sx_sunlock(&ksem_dict_lock);
+}
+
 static int
 ksem_create_copyout_semid(struct thread *td, semid_t *semidp, int fd,
     int compat32)
@@ -1014,6 +1029,7 @@ ksem_module_init(void)
 	p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 200112L);
 	p31b_setcfg(CTL_P1003_1B_SEM_NSEMS_MAX, SEM_MAX);
 	p31b_setcfg(CTL_P1003_1B_SEM_VALUE_MAX, SEM_VALUE_MAX);
+	ksem_info = ksem_info_impl;
 
 	error = syscall_helper_register(ksem_syscalls);
 	if (error)
@@ -1035,6 +1051,7 @@ ksem_module_destroy(void)
 #endif
 	syscall_helper_unregister(ksem_syscalls);
 
+	ksem_info = NULL;
 	p31b_setcfg(CTL_P1003_1B_SEMAPHORES, 0);
 	hashdestroy(ksem_dictionary, M_KSEM, ksem_hash);
 	sx_destroy(&ksem_dict_lock);