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The Linux kernel user-space API guide

While much of the kernel’s user-space API is documented elsewhere (particularly in the man-pages project), some user-space information can also be found in the kernel tree itself. This manual is intended to be the place where this information is gathered.

System calls

• unshare system call
• futex2
• eBPF Userspace API
• IOCTLs
• Introduction of mseal

Security-related interfaces

• No New Privileges Flag
• Seccomp BPF (SECure COMPuting with filters)
• Landlock: unprivileged access control
• Linux Security Modules
• Introduction of non-executable mfd
• Speculation Control
• TEE (Trusted Execution Environment) Userspace API
• Executability check

Devices and I/O

• OpenCAPI (Open Coherent Accelerator Processor Interface)
• Allocating dma-buf using heaps
• Exchanging pixel buffers
• Firmware Control (FWCTL) Userspace API
• GPIO
• IOMMUFD
• Linux Media Infrastructure userspace API
• Dell Systems Management Base Driver
• VDUSE - “vDPA Device in Userspace”
• ISA Plug & Play support

Everything else

• Linux-specific ELF idiosyncrasies
• Netlink Handbook
• Platform Profile Selection (e.g. /sys/firmware/acpi/platform_profile)
• VDUSE - “vDPA Device in Userspace”
• futex2
• Perf ring buffer
• NT synchronization primitive driver