Module posix_shm 

POSIX Shared Memory (shm_open / shm_unlink)

Provides named shared memory objects accessible via /dev/shm semantics. Used by Wayland compositors and other IPC-heavy applications for zero-copy buffer sharing between processes.

This module implements the kernel-side of the POSIX shared memory API:

• shm_open(): Create or open a named shared memory object
• shm_unlink(): Remove a named shared memory object
• ftruncate(): Set the size of the shared memory object
• mmap(MAP_SHARED): Map the shared memory into a process address space

Named objects are stored in a global registry keyed by name. Each object tracks its physical backing frames and per-process virtual mappings.

Structs

ShmMapping

A per-process mapping of a shared memory object.

ShmObject

A named shared memory object.

ShmOpenFlags

Open flags for shm_open (mirror POSIX O_CREAT, O_EXCL, O_RDONLY, O_RDWR).

Constants

SHM_MAX_OBJECTS

Maximum number of concurrent shared memory objects.

SHM_MAX_SIZE

Maximum size of a single shared memory object (256 MB).

SHM_NAME_MAX

Maximum name length for a shared memory object.

Functions

shm_close

Close a reference to a shared memory object.

shm_count

Get the number of active shared memory objects.

shm_open

Create or open a named shared memory object.

shm_stat

Get information about a shared memory object.

shm_truncate

Set the size of a shared memory object (analogous to ftruncate).

shm_unlink

Remove a named shared memory object.