feat(kernel): implemented shared memory resource with a POSIX compatible api by FlareCoding · Pull Request #62 · FlareCoding/StelluxOS

FlareCoding · 2026-03-03T02:12:04Z

Note

High Risk
High risk because it introduces a new shared-memory backing implementation and changes core VMA unmap/merge behavior and mmap semantics, which can impact memory safety, refcounting, and page lifetime across processes.

Overview
Adds a new ref-counted shared-memory backing (mm::shmem) and a SHMEM resource type, including providers for anonymous memfd_create-style objects and named /dev/shm/<name> objects (with O_CREAT|O_EXCL and unlinkat support).

Extends the virtual memory subsystem to support MAP_SHARED mappings backed by shmem (mm_context_map_shared), tracks shared VMAs with backing/offset metadata, and updates unmap/coalescing/destruction paths to unmap without freeing pages for shared mappings.

Wires the feature through Linux syscalls on x86_64/aarch64: registers memfd_create, ftruncate (now truncates either SHMEM backings or filesystem nodes via new node::truncate/ramfs implementation), unlinkat, and updates mmap to accept and validate MAP_SHARED file-backed mappings (SHMEM-only) alongside existing private anonymous mappings. Includes new unit tests covering shmem lifecycle, resize, I/O, and shared mapping behavior.

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kernel/mm/shmem.cpp

kernel/fs/ramfs/ramfs.cpp

kernel/mm/shmem.cpp

kernel/mm/vma.cpp

kernel/resource/providers/shm_provider.cpp

kernel/syscall/handlers/sys_fd.cpp

kernel/mm/vma.cpp

kernel/mm/shmem.cpp

kernel/syscall/handlers/sys_memfd.cpp

kernel/resource/providers/shm_provider.cpp

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Cursor Bugbot has reviewed your changes and found 2 potential issues.

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kernel/resource/providers/shm_provider.cpp

kernel/fs/ramfs/ramfs.cpp

…ble api