BSD syscalls: Local ipc
Dispatch and catalog guide · Every number and configuration alternative
This page is generated from syscalls.master and authored descriptions.json. The signature is the master declaration, not the internal handler's (proc, args, retval) ABI. Descriptions identify selected local mechanisms; they do not claim every branch was audited.
251: semsys
int semsys(u_int which, int a2, int a3, int a4, int a5) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_SEM) · Audit event: AUE_SEMSYS.
Dispatch the historical SysV semaphore multiplexor.
Implementation: semsys. Bounds-checks which against semcalls and calls the selected handler with the packed trailing arguments; individual semctl/semget/semop handlers own locking and validation.
252: msgsys
int msgsys(u_int which, int a2, int a3, int a4, int a5) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGSYS.
Dispatch the historical SysV message-queue multiplexor.
Implementation: msgsys. Bounds-checks which against msgcalls, then invokes the selected message operation with packed trailing arguments; invalid selectors return EINVAL.
253: shmsys
int shmsys(u_int which, int a2, int a3, int a4) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_SHM) · Audit event: AUE_SHMSYS.
Dispatch the historical SysV shared-memory multiplexor.
Implementation: shmsys. Bounds-checks which against shmcalls and invokes the attachment/control/detachment/get handler; the selected operation performs its own locking.
254: semctl
int semctl(int semid, int semnum, int cmd, semun_t arg) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_SEM) · Audit event: AUE_SEMCTL.
Control a SysV semaphore set, including metadata, values and removal.
Implementation: semctl. Under SysV semaphore protection, validates ID/sequence and IPC/MAC permission, then executes the command; removal also clears relevant undo state and wakes affected waiters.
255: semget
int semget(key_t key, int nsems, int semflg);
Declaration: syscalls.master · Condition: (SYSV_SEM) · Audit event: AUE_SEMGET.
Find or allocate a SysV semaphore set by key.
Implementation: semget. Looks up existing identifiers/permissions or grows and initializes set/semaphore storage under subsystem protection, returning an ID with sequence identity.
256: semop
int semop(int semid, struct sembuf *sops, int nsops);
Declaration: syscalls.master · Condition: (SYSV_SEM) · Audit event: AUE_SEMOP.
Apply a vector of SysV semaphore operations with wait and undo semantics.
Implementation: semop. Imports operation records, validates set identity/permissions, evaluates the vector under subsystem locking and blocks/retries when values disallow progress; undo bookkeeping is tied to process exit.
258: msgctl
int msgctl(int msqid, int cmd, struct msqid_ds *buf) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGCTL.
Control a SysV message queue's metadata, limits or removal.
Implementation: msgctl. Validates queue index/sequence and command-specific IPC/MAC permission under the message-subsystem lock, then copies status, changes attributes or removes/wakes queue users.
259: msgget
int msgget(key_t key, int msgflg);
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGGET.
Find or create a SysV message queue by key.
Implementation: msgget. Initializes the subsystem as needed, searches/authorizes an existing queue or allocates an unused slot with ownership and sequence metadata.
260: msgsnd
int msgsnd(int msqid, void *msgp, size_t msgsz, int msgflg);
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGSND.
Append a typed message to a SysV queue, waiting for capacity when allowed.
Implementation: msgsnd. The common body validates queue identity/permissions, imports message segments and coordinates capacity waits/enqueue under subsystem protection; ordinary msgsnd first tests cancellation.
261: msgrcv
user_ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGRCV.
Receive a SysV message selected by type and flags.
Implementation: msgrcv. The common body searches the protected queue, waits when no eligible message exists, handles size/truncation policy and copies out/reclaims message storage; ordinary msgrcv first tests cancellation.
262: shmat
user_addr_t shmat(int shmid, void *shmaddr, int shmflg);
Declaration: syscalls.master · Condition: (SYSV_SHM) · Audit event: AUE_SHMAT.
Attach a SysV shared-memory segment into the calling process map.
Implementation: shmat. Validates segment ID/permission, chooses address/protection, installs the VM mapping and records per-process attachment state; failures unwind mapping/reference work.
263: shmctl
int shmctl(int shmid, int cmd, struct shmid_ds *buf) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_SHM) · Audit event: AUE_SHMCTL.
Control SysV shared-memory metadata, permissions or removal.
Implementation: shmctl. Validates segment identity and command authorization under subsystem protection, converts the user ABI and changes/query state; removal can defer backing destruction until attachments disappear.
264: shmdt
int shmdt(void *shmaddr);
Declaration: syscalls.master · Condition: (SYSV_SHM) · Audit event: AUE_SHMDT.
Detach a previously attached SysV shared-memory mapping.
Implementation: shmdt. Finds the caller's matching attachment, applies MAC checks and calls shm_delete_mapping, updating attachment counts and any pending segment-deletion lifetime.
265: shmget
int shmget(key_t key, size_t size, int shmflg);
Declaration: syscalls.master · Condition: (SYSV_SHM) · Audit event: AUE_SHMGET.
Find or create a SysV shared-memory segment by key and size.
Implementation: shmget. Under subsystem protection, chooses shmget_existing or shmget_allocate_segment, enforcing size/permission/ID sequence rules and creating memory backing for new segments.
266: shm_open
int shm_open(const char *name, int oflag, int mode) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: always · Audit event: AUE_SHMOPEN.
Open or create a named POSIX shared-memory object as a descriptor.
Implementation: shm_open. Imports the name, reserves fileproc state, searches/publishes a protected namespace entry and assigns typed descriptor operations; truncation and mapping later manage memory-entry-backed storage.
267: shm_unlink
int shm_unlink(const char *name);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SHMUNLINK.
Remove a POSIX shared-memory name from its namespace.
Implementation: shm_unlink. Looks up the name under the SHM lock, checks access/MAC and calls pshm_unlink_internal; existing descriptors/mappings can keep object storage alive after the name disappears.
268: sem_open
user_addr_t sem_open(const char *name, int oflag, int mode, int value) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMOPEN.
Open or create a named POSIX semaphore.
Implementation: sem_open. Imports/normalizes the name and team namespace, reserves descriptor state, creates a Mach semaphore when needed and publishes/reuses the protected POSIX object with ownership checks.
269: sem_close
int sem_close(sem_t *sem);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMCLOSE.
Close a POSIX semaphore descriptor.
Implementation: sem_close. Checks descriptor type under the fd lock and calls fp_close_and_unlock; namespace unlink and last backing-semaphore reference are separate events.
270: sem_unlink
int sem_unlink(const char *name);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMUNLINK.
Remove a POSIX semaphore name from the protected namespace.
Implementation: sem_unlink. Uses the team/name key, checks access/MAC and calls psem_unlink_internal; open descriptors retain their object references.
271: sem_wait
int sem_wait(sem_t *sem);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMWAIT.
Wait for a POSIX semaphore count.
Implementation: sem_wait. The common body pins a typed descriptor, checks object/MAC state and calls Mach semaphore_wait, translating its result before dropping the fileproc. Ordinary sem_wait tests cancellation.
272: sem_trywait
int sem_trywait(sem_t *sem);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMTRYWAIT.
Attempt a POSIX semaphore decrement without waiting.
Implementation: sem_trywait. Pins/checks the typed semaphore object and calls semaphore_timedwait with the immediate timeout policy, translating failure/status and releasing the fd reference.
273: sem_post
int sem_post(sem_t *sem);
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMPOST.
Increment/wake a POSIX semaphore.
Implementation: sem_post. Pins/checks the typed object and invokes Mach semaphore_signal, then translates status and drops the fileproc reference.
418: msgsnd_nocancel
int msgsnd_nocancel(int msqid, void *msgp, size_t msgsz, int msgflg) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGSND.
Append a typed message to a SysV queue, waiting for capacity when allowed.
Implementation: msgsnd_nocancel. The common body validates queue identity/permissions, imports message segments and coordinates capacity waits/enqueue under subsystem protection; ordinary msgsnd first tests cancellation.
419: msgrcv_nocancel
user_ssize_t msgrcv_nocancel(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: (SYSV_MSG) · Audit event: AUE_MSGRCV.
Receive a SysV message selected by type and flags.
Implementation: msgrcv_nocancel. The common body searches the protected queue, waits when no eligible message exists, handles size/truncation policy and copies out/reclaims message storage; ordinary msgrcv first tests cancellation.
420: sem_wait_nocancel
int sem_wait_nocancel(sem_t *sem) NO_SYSCALL_STUB;
Declaration: syscalls.master · Condition: always · Audit event: AUE_SEMWAIT.
Wait for a POSIX semaphore count.
Implementation: sem_wait_nocancel. The common body pins a typed descriptor, checks object/MAC state and calls Mach semaphore_wait, translating its result before dropping the fileproc. Ordinary sem_wait tests cancellation.