PLEASE NOTE: This entire crate including this
documentation is automatically generated from
CloudABI is what you get if you take POSIX, add capability-based security, and remove everything that's incompatible with that. The result is a minimal ABI consisting of only 49 syscalls.
CloudABI doesn't have its own kernel, but instead is implemented in existing kernels: FreeBSD has CloudABI support for x86-64 and arm64, and a patch-set for NetBSD and a patch-set for Linux are available as well. This means that CloudABI binaries can be executed on different operating systems, without any modification.
Capability-based security means that processes can only perform actions that have no global impact. Processes cannot open files by their absolute path, cannot open network connections, and cannot observe global system state such as the process table.
The capabilities of a process are fully determined by its set of open file descriptors (fds). For example, files can only be opened if the process already has a file descriptor to a directory the file is in.
Unlike in POSIX, where processes are normally started with file descriptors 0, 1, and 2 reserved for standard input, output, and error, CloudABI does not reserve any file descriptor numbers for specific purposes.
In CloudABI, a process depends on its parent process to launch it with the right set of resources, since the process will not be able to open any new resources. For example, a simple static web server would need to be started with a file descriptor to a TCP listener, and a file descriptor to the directory for which to serve files. The web server will then be unable to do anything other than reading files in that directory, and process incoming network connections.
So, unknown CloudABI binaries can safely be executed without the need for containers, virtual machines, or other sandboxing technologies.
Watch Ed Schouten's Talk at 32C3 for more information about what capability-based security for UNIX means.
Cloudlibc is an implementation
of the C standard library, without all CloudABI-incompatible
functions. For example, Cloudlibc does not have
printf, but does
fprintf. It does not have
open, but does have
CloudABI-Ports is a
collection of ports of commonly used libraries and applications to
CloudABI. It contains software such as
memcached, and much more. The software is patched to not depend on
any global state, such as files in
Instructions for using CloudABI (including kernel modules/patches, toolchain, and ports) are available for several operating systems:
- Arch Linux
- Debian, Ubuntu, and other Debian derivatives
- FreeBSD, PC-BSD and DragonFly BSD
- Mac OS X
Specification of the ABI
The entire ABI is specified in a a file called
from which all
and documentation (including the one you're reading now) is generated.