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

1 files changed, 18 insertions, 1 deletions

diff --git a/sys/kern/uipc_sem.c b/sys/kern/uipc_sem.c
index 509f32e909b7..a9f60f1e538d 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);