NOTE: This project is unmaintained

CloudABI is no longer being maintained. It was an awesome experiment, but it never got enough traction to be sustainable. If you like the idea behind CloudABI, please consider looking into the WebAssembly System Interface (WASI). WASI's design has been inspired by CloudABI.

The author of CloudABI (Ed Schouten) would like to thank all of the people who contributed to this project. Let's hope CloudABI lives on in spirit and influences the way software is designed in the future!

Nuxi CloudABI

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

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

Cloudlibc is an implementation of the C standard library, without all CloudABI-incompatible functions. For example, Cloudlibc does not have printf, but does have fprintf. It does not have open, but does have openat.

CloudABI-Ports

CloudABI-Ports is a collection of ports of commonly used libraries and applications to CloudABI. It contains software such as zlib, libpng, boost, memcached, and much more. The software is patched to not depend on any global state, such as files in /etc or /dev, using open(), etc.

Using CloudABI

Instructions for using CloudABI (including kernel modules/patches, toolchain, and ports) are available for several operating systems:

• FreeBSD
• Linux
• macOS

Specification of the ABI

The entire ABI is specified in a file called cloudabi.txt, from which all headers and documentation (including the one you're reading now) is generated.

System calls

• cloudabi_sys_clock_res_get()
• cloudabi_sys_clock_time_get()
• cloudabi_sys_condvar_signal()
• cloudabi_sys_fd_close()
• cloudabi_sys_fd_create1()
• cloudabi_sys_fd_create2()
• cloudabi_sys_fd_datasync()
• cloudabi_sys_fd_dup()
• cloudabi_sys_fd_pread()
• cloudabi_sys_fd_pwrite()
• cloudabi_sys_fd_read()
• cloudabi_sys_fd_replace()
• cloudabi_sys_fd_seek()
• cloudabi_sys_fd_stat_get()
• cloudabi_sys_fd_stat_put()
• cloudabi_sys_fd_sync()
• cloudabi_sys_fd_write()
• cloudabi_sys_file_advise()
• cloudabi_sys_file_allocate()
• cloudabi_sys_file_create()
• cloudabi_sys_file_link()
• cloudabi_sys_file_open()
• cloudabi_sys_file_readdir()
• cloudabi_sys_file_readlink()
• cloudabi_sys_file_rename()
• cloudabi_sys_file_stat_fget()
• cloudabi_sys_file_stat_fput()
• cloudabi_sys_file_stat_get()
• cloudabi_sys_file_stat_put()
• cloudabi_sys_file_symlink()
• cloudabi_sys_file_unlink()
• cloudabi_sys_lock_unlock()
• cloudabi_sys_mem_advise()
• cloudabi_sys_mem_map()
• cloudabi_sys_mem_protect()
• cloudabi_sys_mem_sync()
• cloudabi_sys_mem_unmap()
• cloudabi_sys_poll()
• cloudabi_sys_proc_exec()
• cloudabi_sys_proc_exit()
• cloudabi_sys_proc_fork()
• cloudabi_sys_proc_raise()
• cloudabi_sys_random_get()
• cloudabi_sys_sock_recv()
• cloudabi_sys_sock_send()
• cloudabi_sys_sock_shutdown()
• cloudabi_sys_thread_create()
• cloudabi_sys_thread_exit()
• cloudabi_sys_thread_yield()

cloudabi_sys_clock_res_get()

Obtains the resolution of a clock.

Inputs:

• cloudabi_clockid_t clock_id

  The clock for which the resolution needs to be returned.

Outputs:

• cloudabi_timestamp_t resolution

  The resolution of the clock.

cloudabi_sys_clock_time_get()

Obtains the time value of a clock.

Inputs:

• cloudabi_clockid_t clock_id

  The clock for which the time needs to be returned.

• cloudabi_timestamp_t precision

  The maximum lag (exclusive) that the returned time value may have, compared to its actual value.

Outputs:

• cloudabi_timestamp_t time

  The time value of the clock.

cloudabi_sys_condvar_signal()

Wakes up threads waiting on a userspace condition variable.

If an invocation of this system call causes all waiting threads to be woken up, the value of the condition variable is set to CLOUDABI_CONDVAR_HAS_NO_WAITERS. As long as the condition variable is set to this value, it is not needed to invoke this system call.

Inputs:

• _Atomic(cloudabi_condvar_t) *condvar

  The userspace condition variable that has waiting threads.

• cloudabi_scope_t scope

  Whether the condition variable is stored in private or shared memory.

• cloudabi_nthreads_t nwaiters

  The number of threads that need to be woken up. If it exceeds the number of waiting threads, all threads are woken up.

cloudabi_sys_fd_close()

Closes a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor that needs to be closed.

cloudabi_sys_fd_create1()

Creates a file descriptor.

Inputs:

• cloudabi_filetype_t type

  Possible values:

  • CLOUDABI_FILETYPE_SHARED_MEMORY

    Creates an anonymous shared memory object.

Outputs:

• cloudabi_fd_t fd

  The file descriptor that has been created.

cloudabi_sys_fd_create2()

Creates a pair of file descriptors.

Inputs:

• cloudabi_filetype_t type

  Possible values:

  • CLOUDABI_FILETYPE_SOCKET_DGRAM

    Creates a UNIX datagram socket pair.

  • CLOUDABI_FILETYPE_SOCKET_STREAM

    Creates a UNIX byte-stream socket pair.

Outputs:

• cloudabi_fd_t fd1

  The first file descriptor of the pair.

• cloudabi_fd_t fd2

  The second file descriptor of the pair.

cloudabi_sys_fd_datasync()

Synchronizes the data of a file to disk.

Inputs:

• cloudabi_fd_t fd

  The file descriptor of the file whose data needs to be synchronized to disk.

cloudabi_sys_fd_dup()

Duplicates a file descriptor.

Inputs:

• cloudabi_fd_t from

  The file descriptor that needs to be duplicated.

Outputs:

• cloudabi_fd_t fd

  The new file descriptor.

cloudabi_sys_fd_pread()

Reads from a file descriptor, without using and updating the file descriptor's offset.

Inputs:

• cloudabi_fd_t fd

  The file descriptor from which data should be read.

• const cloudabi_iovec_t *iovs and size_t iovs_len

  List of scatter/gather vectors where data should be stored.

• cloudabi_filesize_t offset

  The offset within the file at which reading should start.

Outputs:

• size_t nread

  The number of bytes read.

cloudabi_sys_fd_pwrite()

Writes to a file descriptor, without using and updating the file descriptor's offset.

Inputs:

• cloudabi_fd_t fd

  The file descriptor to which data should be written.

• const cloudabi_ciovec_t *iovs and size_t iovs_len

  List of scatter/gather vectors where data should be retrieved.

• cloudabi_filesize_t offset

  The offset within the file at which writing should start.

Outputs:

• size_t nwritten

  The number of bytes written.

cloudabi_sys_fd_read()

Reads from a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor from which data should be read.

• const cloudabi_iovec_t *iovs and size_t iovs_len

  List of scatter/gather vectors where data should be stored.

Outputs:

• size_t nread

  The number of bytes read.

cloudabi_sys_fd_replace()

Atomically replaces a file descriptor by a copy of another file descriptor.

Due to the strong focus on thread safety, this environment does not provide a mechanism to duplicate a file descriptor to an arbitrary number, like dup2(). This would be prone to race conditions, as an actual file descriptor with the same number could be allocated by a different thread at the same time.

This system call provides a way to atomically replace file descriptors, which would disappear if dup2() were to be removed entirely.

Inputs:

• cloudabi_fd_t from

  The file descriptor that needs to be copied.

• cloudabi_fd_t to

  The file descriptor that needs to be overwritten.

cloudabi_sys_fd_seek()

Moves the offset of the file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor whose offset has to be moved.

• cloudabi_filedelta_t offset

  The number of bytes to move.

• cloudabi_whence_t whence

  Relative to which position the move should take place.

Outputs:

• cloudabi_filesize_t newoffset

  The new offset of the file descriptor, relative to the start of the file.

cloudabi_sys_fd_stat_get()

Gets attributes of a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor whose attributes have to be obtained.

• cloudabi_fdstat_t *buf

  The buffer where the file descriptor's attributes are stored.

cloudabi_sys_fd_stat_put()

Adjusts attributes of a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor whose attributes have to be adjusted.

• const cloudabi_fdstat_t *buf

  The desired values of the file descriptor attributes that are adjusted.

• cloudabi_fdsflags_t flags

  A bitmask indicating which attributes have to be adjusted.

cloudabi_sys_fd_sync()

Synchronizes the data and metadata of a file to disk.

Inputs:

• cloudabi_fd_t fd

  The file descriptor of the file whose data and metadata needs to be synchronized to disk.

cloudabi_sys_fd_write()

Writes to a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor to which data should be written.

• const cloudabi_ciovec_t *iovs and size_t iovs_len

  List of scatter/gather vectors where data should be retrieved.

Outputs:

• size_t nwritten

  The number of bytes written.

cloudabi_sys_file_advise()

Provides file advisory information on a file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor for which to provide file advisory information.

• cloudabi_filesize_t offset

  The offset within the file to which the advisory applies.

• cloudabi_filesize_t len

  The length of the region to which the advisory applies.

• cloudabi_advice_t advice

  The advice.

cloudabi_sys_file_allocate()

Forces the allocation of space in a file.

Inputs:

• cloudabi_fd_t fd

  The file in which the space should be allocated.

• cloudabi_filesize_t offset

  The offset at which the allocation should start.

• cloudabi_filesize_t len

  The length of the area that is allocated.

cloudabi_sys_file_create()

Creates a file of a specified type.

Inputs:

• cloudabi_fd_t fd

  The working directory at which the resolution of the file to be created starts.

• const char *path and size_t path_len

  The path at which the file should be created.

• cloudabi_filetype_t type

  Possible values:

  • CLOUDABI_FILETYPE_DIRECTORY

    Creates a directory.

cloudabi_sys_file_link()

Creates a hard link.

Inputs:

• cloudabi_lookup_t fd1

  The working directory at which the resolution of the source path starts.

• const char *path1 and size_t path1_len

  The source path of the file that should be hard linked.

• cloudabi_fd_t fd2

  The working directory at which the resolution of the destination path starts.

• const char *path2 and size_t path2_len

  The destination path at which the hard link should be created.

cloudabi_sys_file_open()

Opens a file.

Inputs:

• cloudabi_lookup_t dirfd

  The working directory at which the resolution of the file to be opened starts.

• const char *path and size_t path_len

  The path of the file that should be opened.

• cloudabi_oflags_t oflags

  The method at which the file should be opened.

• const cloudabi_fdstat_t *fds

  cloudabi_fdstat_t::fs_rights_base and cloudabi_fdstat_t::fs_rights_inheriting specify the initial rights of the newly created file descriptor. The operating system is allowed to return a file descriptor with fewer rights than specified, if and only if those rights do not apply to the type of file being opened.

  cloudabi_fdstat_t::fs_flags specifies the initial flags of the file descriptor.

  cloudabi_fdstat_t::fs_filetype is ignored.

Outputs:

• cloudabi_fd_t fd

  The file descriptor of the file that has been opened.

cloudabi_sys_file_readdir()

Reads directory entries from a directory.

When successful, the contents of the output buffer consist of a sequence of directory entries. Each directory entry consists of a cloudabi_dirent_t object, followed by cloudabi_dirent_t::d_namlen bytes holding the name of the directory entry.

This system call fills the output buffer as much as possible, potentially truncating the last directory entry. This allows the caller to grow its read buffer size in case it's too small to fit a single large directory entry, or skip the oversized directory entry.

Inputs:

• cloudabi_fd_t fd

  The directory from which to read the directory entries.

• void *buf and size_t buf_len

  The buffer where directory entries are stored.

• cloudabi_dircookie_t cookie

  The location within the directory to start reading.

Outputs:

• size_t bufused

  The number of bytes stored in the read buffer. If less than the size of the read buffer, the end of the directory has been reached.

cloudabi_sys_file_readlink()

Reads the contents of a symbolic link.

Inputs:

• cloudabi_fd_t fd

  The working directory at which the resolution of the path of the symbolic starts.

• const char *path and size_t path_len

  The path of the symbolic link whose contents should be read.

• char *buf and size_t buf_len

  The buffer where the contents of the symbolic link should be stored.

Outputs:

• size_t bufused

  The number of bytes placed in the buffer.

cloudabi_sys_file_rename()

Renames a file.

Inputs:

• cloudabi_fd_t fd1

  The working directory at which the resolution of the source path starts.

• const char *path1 and size_t path1_len

  The source path of the file that should be renamed.

• cloudabi_fd_t fd2

  The working directory at which the resolution of the destination path starts.

• const char *path2 and size_t path2_len

  The destination path to which the file should be renamed.

cloudabi_sys_file_stat_fget()

Gets attributes of a file by file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor whose attributes have to be obtained.

• cloudabi_filestat_t *buf

  The buffer where the file's attributes are stored.

cloudabi_sys_file_stat_fput()

Adjusts attributes of a file by file descriptor.

Inputs:

• cloudabi_fd_t fd

  The file descriptor whose attributes have to be adjusted.

• const cloudabi_filestat_t *buf

  The desired values of the file attributes that are adjusted.

• cloudabi_fsflags_t flags

  A bitmask indicating which attributes have to be adjusted.

cloudabi_sys_file_stat_get()

Gets attributes of a file by path.

Inputs:

• cloudabi_lookup_t fd

  The working directory at which the resolution of the path whose attributes have to be obtained starts.

• const char *path and size_t path_len

  The path of the file whose attributes have to be obtained.

• cloudabi_filestat_t *buf

  The buffer where the file's attributes are stored.

cloudabi_sys_file_stat_put()

Adjusts attributes of a file by path.

Inputs:

• cloudabi_lookup_t fd

  The working directory at which the resolution of the path whose attributes have to be adjusted starts.

• const char *path and size_t path_len

  The path of the file whose attributes have to be adjusted.

• const cloudabi_filestat_t *buf

  The desired values of the file attributes that are adjusted.

• cloudabi_fsflags_t flags

  A bitmask indicating which attributes have to be adjusted.

cloudabi_sys_file_symlink()

Creates a symbolic link.

Inputs:

• const char *path1 and size_t path1_len

  The contents of the symbolic link.

• cloudabi_fd_t fd

  The working directory at which the resolution of the destination path starts.

• const char *path2 and size_t path2_len

  The destination path at which the symbolic link should be created.

cloudabi_sys_file_unlink()

Unlinks a file, or removes a directory.

Inputs:

• cloudabi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *path and size_t path_len

  The path that needs to be unlinked or removed.

• cloudabi_ulflags_t flags

  Possible values:

  • CLOUDABI_UNLINK_REMOVEDIR

    If set, attempt to remove a directory. Otherwise, unlink a file.

cloudabi_sys_lock_unlock()

Unlocks a write-locked userspace lock.

If a userspace lock is unlocked while having its CLOUDABI_LOCK_KERNEL_MANAGED flag set, the lock cannot be unlocked in userspace directly. This system call needs to be performed instead, so that any waiting threads can be woken up.

To prevent spurious invocations of this system call, the lock must be locked for writing. This prevents other threads from acquiring additional read locks while the system call is in progress. If the lock is acquired for reading, it must first be upgraded to a write lock.

Inputs:

• _Atomic(cloudabi_lock_t) *lock

  The userspace lock that is locked for writing by the calling thread.

• cloudabi_scope_t scope

  Whether the lock is stored in private or shared memory.

cloudabi_sys_mem_advise()

Provides memory advisory information on a region of memory.

Inputs:

• void *mapping and size_t mapping_len

  The pages for which to provide memory advisory information.

• cloudabi_advice_t advice

  The advice.

cloudabi_sys_mem_map()

Creates a memory mapping, making the contents of a file accessible through memory.

Inputs:

• void *addr

  If CLOUDABI_MAP_FIXED is set, specifies to which address the file region is mapped. Otherwise, the mapping is performed at an unused location.

• size_t len

  The length of the memory mapping to be created.

• cloudabi_mprot_t prot

  Initial memory protection options for the memory mapping.

• cloudabi_mflags_t flags

  Memory mapping flags.

• cloudabi_fd_t fd

  If CLOUDABI_MAP_ANON is set, this argument must be CLOUDABI_MAP_ANON_FD. Otherwise, this argument specifies the file whose contents need to be mapped.

• cloudabi_filesize_t off

  If CLOUDABI_MAP_ANON is set, this argument must be zero. Otherwise, this argument specifies the offset within the file at which the mapping starts.

Outputs:

• void *mem

  The starting address of the memory mapping.

cloudabi_sys_mem_protect()

Change the protection of a memory mapping.

Inputs:

• void *mapping and size_t mapping_len

  The pages that need their protection changed.

• cloudabi_mprot_t prot

  New protection options.

cloudabi_sys_mem_sync()

Synchronize a region of memory with its physical storage.

Inputs:

• void *mapping and size_t mapping_len

  The pages that need to be synchronized.

• cloudabi_msflags_t flags

  The method of synchronization.

cloudabi_sys_mem_unmap()

Unmaps a region of memory.

Inputs:

• void *mapping and size_t mapping_len

  The pages that needs to be unmapped.

cloudabi_sys_poll()

Concurrently polls for the occurrence of a set of events.

Inputs:

• const cloudabi_subscription_t *in

  The events to which to subscribe.

• cloudabi_event_t *out

  The events that have occurred.

• size_t nsubscriptions

  Both the number of subscriptions and events.

Outputs:

• size_t nevents

  The number of events stored.

cloudabi_sys_proc_exec()

Replaces the process by a new executable.

Process execution in CloudABI differs from POSIX in two ways: handling of arguments and inheritance of file descriptors.

CloudABI does not use string command line arguments. Instead, a buffer with binary data is copied into the address space of the new executable. The kernel does not enforce any specific structure to this data, although CloudABI's C library uses it to store a tree structure that is semantically identical to YAML.

Due to the strong focus on thread safety, file descriptors aren't inherited through close-on-exec flags. An explicit list of file descriptors that need to be retained needs to be provided. After execution, file descriptors are placed in the order in which they are stored in the array. This not only makes the execution process deterministic. It also prevents potential information disclosures about the layout of the original process.

Inputs:

• cloudabi_fd_t fd

  A file descriptor of the new executable.

• const void *data and size_t data_len

  Binary argument data that is passed on to the new executable.

• const cloudabi_fd_t *fds and size_t fds_len

  The layout of the file descriptor table after execution.

cloudabi_sys_proc_exit()

Terminates the process normally.

Inputs:

• cloudabi_exitcode_t rval

  The exit code returned by the process. The exit code can be obtained by other processes through cloudabi_event_t::proc_terminate.exitcode.

Does not return.

cloudabi_sys_proc_fork()

Forks the process of the calling thread.

After forking, a new process shall be created, having only a copy of the calling thread. The parent process will obtain a process descriptor. When closed, the child process is automatically signaled with CLOUDABI_SIGKILL.

Outputs:

• cloudabi_fd_t fd

  In the parent process: the file descriptor number of the process descriptor.

  In the child process: CLOUDABI_PROCESS_CHILD.

• cloudabi_tid_t tid

  In the parent process: undefined.

  In the child process: the thread ID of the initial thread of the child process.

cloudabi_sys_proc_raise()

Sends a signal to the process of the calling thread.

Inputs:

• cloudabi_signal_t sig

  The signal condition that should be triggered. If the signal causes the process to terminate, its condition can be obtained by other processes through cloudabi_event_t::proc_terminate.signal.

cloudabi_sys_random_get()

Obtains random data from the kernel random number generator.

As this interface is not guaranteed to be fast, it is advised that the random data obtained through this system call is used as the seed for a userspace pseudo-random number generator.

Inputs:

• void *buf and size_t buf_len

  The buffer that needs to be filled with random data.

cloudabi_sys_sock_recv()

Receives a message on a socket.

Inputs:

• cloudabi_fd_t sock

  The socket on which a message should be received.

• const cloudabi_recv_in_t *in

  Input parameters.

• cloudabi_recv_out_t *out

  Output parameters.

cloudabi_sys_sock_send()

Sends a message on a socket.

Inputs:

• cloudabi_fd_t sock

  The socket on which a message should be sent.

• const cloudabi_send_in_t *in

  Input parameters.

• cloudabi_send_out_t *out

  Output parameters.

cloudabi_sys_sock_shutdown()

Shuts down socket send and receive channels.

Inputs:

• cloudabi_fd_t sock

  The socket that needs its channels shut down.

• cloudabi_sdflags_t how

  Which channels on the socket need to be shut down.

cloudabi_sys_thread_create()

Creates a new thread within the current process.

Inputs:

• cloudabi_threadattr_t *attr

  The desired attributes of the new thread.

Outputs:

• cloudabi_tid_t tid

  The thread ID of the new thread.

cloudabi_sys_thread_exit()

Terminates the calling thread.

This system call can also unlock a single userspace lock after termination, which can be used to implement thread joining.

Inputs:

• _Atomic(cloudabi_lock_t) *lock

  Userspace lock that is locked for writing by the calling thread.

• cloudabi_scope_t scope

  Whether the lock is stored in private or shared memory.

Does not return.

cloudabi_sys_thread_yield()

Temporarily yields execution of the calling thread.

Types

cloudabi_advice_t (uint8_t)

File or memory access pattern advisory information.

Used by cloudabi_sys_file_advise() and cloudabi_sys_mem_advise().

Possible values:

• CLOUDABI_ADVICE_DONTNEED

  The application expects that it will not access the specified data in the near future.

• CLOUDABI_ADVICE_NOREUSE

  The application expects to access the specified data once and then not reuse it thereafter.

• CLOUDABI_ADVICE_NORMAL

  The application has no advice to give on its behavior with respect to the specified data.

• CLOUDABI_ADVICE_RANDOM

  The application expects to access the specified data in a random order.

• CLOUDABI_ADVICE_SEQUENTIAL

  The application expects to access the specified data sequentially from lower offsets to higher offsets.

• CLOUDABI_ADVICE_WILLNEED

  The application expects to access the specified data in the near future.

cloudabi_auxtype_t (uint32_t)

Enumeration describing the kind of value stored in cloudabi_auxv_t.

Possible values:

• CLOUDABI_AT_ARGDATA

  Base address of the binary argument data provided to cloudabi_sys_proc_exec().

• CLOUDABI_AT_ARGDATALEN

  Length of the binary argument data provided to cloudabi_sys_proc_exec().

• CLOUDABI_AT_BASE

  Base address at which the executable is placed in memory.

• CLOUDABI_AT_CANARY

  Base address of a buffer of random data that may be used for non-cryptographic purposes, for example as a canary for stack smashing protection.

• CLOUDABI_AT_CANARYLEN

  Length of a buffer of random data that may be used for non-cryptographic purposes, for example as a canary for stack smashing protection.

• CLOUDABI_AT_NCPUS

  Number of CPUs that the system this process is running on has.

• CLOUDABI_AT_NULL

  Terminator of the auxiliary vector.

• CLOUDABI_AT_PAGESZ

  Smallest memory object size for which individual memory protection controls can be configured.

• CLOUDABI_AT_PHDR

  Address of the first ELF program header of the executable.

• CLOUDABI_AT_PHNUM

  Number of ELF program headers of the executable.

• CLOUDABI_AT_PID

  Identifier of the process.

  This environment does not provide any simple numerical process identifiers, for the reason that these are not useful in distributed contexts. Instead, processes are identified by a UUID.

  This record should point to sixteen bytes of binary data, containing a version 4 UUID (fully random).

• CLOUDABI_AT_SYSINFO_EHDR

  Address of the ELF header of the vDSO.

  The vDSO is a shared library that is mapped in the address space of the process. It provides entry points for every system call supported by the environment, all having a corresponding symbol that is prefixed with cloudabi_sys_. System calls should be invoked through these entry points.

  The first advantage of letting processes call into a vDSO to perform system calls instead of raising hardware traps is that it allows for easy emulation of executables on top of existing operating systems. The second advantage is that in cases where an operating system provides native support for CloudABI executables, it may still implement partial userspace implementations of these system calls to improve performance (e.g., cloudabi_sys_clock_time_get()). It also provides a more dynamic way of adding, removing or replacing system calls.

• CLOUDABI_AT_TID

  Thread ID of the initial thread of the process.

cloudabi_auxv_t (struct)

Auxiliary vector entry.

The auxiliary vector is a list of key-value pairs that is provided to the process on startup. Unlike structures, it is extensible, as it is possible to add new records later on. The auxiliary vector is always terminated by an entry having type CLOUDABI_AT_NULL.

The auxiliary vector is part of the x86-64 ABI, but is used by this environment on all architectures.

Used by cloudabi_processentry_t.

Members:

• cloudabi_auxtype_t a_type

  The type of the auxiliary vector entry.

• When a_type is CLOUDABI_AT_ARGDATALEN, CLOUDABI_AT_CANARYLEN, CLOUDABI_AT_NCPUS, CLOUDABI_AT_PAGESZ, CLOUDABI_AT_PHNUM, or CLOUDABI_AT_TID:

  • size_t a_val

    A numerical value.

• When a_type is CLOUDABI_AT_ARGDATA, CLOUDABI_AT_BASE, CLOUDABI_AT_CANARY, CLOUDABI_AT_PHDR, CLOUDABI_AT_PID, or CLOUDABI_AT_SYSINFO_EHDR:

  • void *a_ptr

    A pointer value.

cloudabi_ciovec_t (struct)

A region of memory for scatter/gather writes.

Used by cloudabi_send_in_t, cloudabi_sys_fd_pwrite(), and cloudabi_sys_fd_write().

Members:

• const void *buf and size_t buf_len

  The address and length of the buffer to be written.

cloudabi_clockid_t (uint32_t)

Identifiers for clocks.

Used by cloudabi_subscription_t, cloudabi_sys_clock_res_get(), and cloudabi_sys_clock_time_get().

Possible values:

• CLOUDABI_CLOCK_MONOTONIC

  The system-wide monotonic clock, which is defined as a clock measuring real time, whose value cannot be adjusted and which cannot have negative clock jumps.

  The epoch of this clock is undefined. The absolute time value of this clock therefore has no meaning.

• CLOUDABI_CLOCK_PROCESS_CPUTIME_ID

  The CPU-time clock associated with the current process.

• CLOUDABI_CLOCK_REALTIME

  The system-wide clock measuring real time. Time value zero corresponds with 1970-01-01T00:00:00Z.

• CLOUDABI_CLOCK_THREAD_CPUTIME_ID

  The CPU-time clock associated with the current thread.

cloudabi_condvar_t (uint32_t)

A userspace condition variable.

Used by cloudabi_subscription_t and cloudabi_sys_condvar_signal().

Special values:

• CLOUDABI_CONDVAR_HAS_NO_WAITERS

  The condition variable is in its initial state. There are no threads waiting to be woken up. If the condition variable has any other value, the kernel must be called to wake up any sleeping threads.

cloudabi_device_t (uint64_t)

Identifier for a device containing a file system. Can be used in combination with cloudabi_inode_t to uniquely identify a file on the local system.

Used by cloudabi_filestat_t.

cloudabi_dircookie_t (uint64_t)

A reference to the offset of a directory entry.

Used by cloudabi_dirent_t and cloudabi_sys_file_readdir().

Special values:

• CLOUDABI_DIRCOOKIE_START

  Permanent reference to the first directory entry within a directory.

cloudabi_dirent_t (struct)

A directory entry.

Members:

• cloudabi_dircookie_t d_next

  The offset of the next directory entry stored in this directory.

• cloudabi_inode_t d_ino

  The serial number of the file referred to by this directory entry.

• uint32_t d_namlen

  The length of the name of the directory entry.

• cloudabi_filetype_t d_type

  The type of the file referred to by this directory entry.

cloudabi_errno_t (uint16_t)

Error codes returned by system calls.

Not all of these error codes are returned by the system calls provided by this environment, but are either used in userspace exclusively or merely provided for alignment with POSIX.

Used by cloudabi_event_t.

Possible values:

• CLOUDABI_ESUCCESS

  No error occurred. System call completed successfully.

• CLOUDABI_E2BIG

  Argument list too long.

• CLOUDABI_EACCES

  Permission denied.

• CLOUDABI_EADDRINUSE

  Address in use.

• CLOUDABI_EADDRNOTAVAIL

  Address not available.

• CLOUDABI_EAFNOSUPPORT

  Address family not supported.

• CLOUDABI_EAGAIN

  Resource unavailable, or operation would block.

• CLOUDABI_EALREADY

  Connection already in progress.

• CLOUDABI_EBADF

  Bad file descriptor.

• CLOUDABI_EBADMSG

  Bad message.

• CLOUDABI_EBUSY

  Device or resource busy.

• CLOUDABI_ECANCELED

  Operation canceled.

• CLOUDABI_ECHILD

  No child processes.

• CLOUDABI_ECONNABORTED

  Connection aborted.

• CLOUDABI_ECONNREFUSED

  Connection refused.

• CLOUDABI_ECONNRESET

  Connection reset.

• CLOUDABI_EDEADLK

  Resource deadlock would occur.

• CLOUDABI_EDESTADDRREQ

  Destination address required.

• CLOUDABI_EDOM

  Mathematics argument out of domain of function.

• CLOUDABI_EDQUOT

  Reserved.

• CLOUDABI_EEXIST

  File exists.

• CLOUDABI_EFAULT

  Bad address.

• CLOUDABI_EFBIG

  File too large.

• CLOUDABI_EHOSTUNREACH

  Host is unreachable.

• CLOUDABI_EIDRM

  Identifier removed.

• CLOUDABI_EILSEQ

  Illegal byte sequence.

• CLOUDABI_EINPROGRESS

  Operation in progress.

• CLOUDABI_EINTR

  Interrupted function.

• CLOUDABI_EINVAL

  Invalid argument.

• CLOUDABI_EIO

  I/O error.

• CLOUDABI_EISCONN

  Socket is connected.

• CLOUDABI_EISDIR

  Is a directory.

• CLOUDABI_ELOOP

  Too many levels of symbolic links.

• CLOUDABI_EMFILE

  File descriptor value too large.

• CLOUDABI_EMLINK

  Too many links.

• CLOUDABI_EMSGSIZE

  Message too large.

• CLOUDABI_EMULTIHOP

  Reserved.

• CLOUDABI_ENAMETOOLONG

  Filename too long.

• CLOUDABI_ENETDOWN

  Network is down.

• CLOUDABI_ENETRESET

  Connection aborted by network.

• CLOUDABI_ENETUNREACH

  Network unreachable.

• CLOUDABI_ENFILE

  Too many files open in system.

• CLOUDABI_ENOBUFS

  No buffer space available.

• CLOUDABI_ENODEV

  No such device.

• CLOUDABI_ENOENT

  No such file or directory.

• CLOUDABI_ENOEXEC

  Executable file format error.

• CLOUDABI_ENOLCK

  No locks available.

• CLOUDABI_ENOLINK

  Reserved.

• CLOUDABI_ENOMEM

  Not enough space.

• CLOUDABI_ENOMSG

  No message of the desired type.

• CLOUDABI_ENOPROTOOPT

  Protocol not available.

• CLOUDABI_ENOSPC

  No space left on device.

• CLOUDABI_ENOSYS

  Function not supported.

• CLOUDABI_ENOTCONN

  The socket is not connected.

• CLOUDABI_ENOTDIR

  Not a directory or a symbolic link to a directory.

• CLOUDABI_ENOTEMPTY

  Directory not empty.

• CLOUDABI_ENOTRECOVERABLE

  State not recoverable.

• CLOUDABI_ENOTSOCK

  Not a socket.

• CLOUDABI_ENOTSUP

  Not supported, or operation not supported on socket.

• CLOUDABI_ENOTTY

  Inappropriate I/O control operation.

• CLOUDABI_ENXIO

  No such device or address.

• CLOUDABI_EOVERFLOW

  Value too large to be stored in data type.

• CLOUDABI_EOWNERDEAD

  Previous owner died.

• CLOUDABI_EPERM

  Operation not permitted.

• CLOUDABI_EPIPE

  Broken pipe.

• CLOUDABI_EPROTO

  Protocol error.

• CLOUDABI_EPROTONOSUPPORT

  Protocol not supported.

• CLOUDABI_EPROTOTYPE

  Protocol wrong type for socket.

• CLOUDABI_ERANGE

  Result too large.

• CLOUDABI_EROFS

  Read-only file system.

• CLOUDABI_ESPIPE

  Invalid seek.

• CLOUDABI_ESRCH

  No such process.

• CLOUDABI_ESTALE

  Reserved.

• CLOUDABI_ETIMEDOUT

  Connection timed out.

• CLOUDABI_ETXTBSY

  Text file busy.

• CLOUDABI_EXDEV

  Cross-device link.

• CLOUDABI_ENOTCAPABLE

  Extension: Capabilities insufficient.

cloudabi_event_t (struct)

An event that occurred.

Used by cloudabi_sys_poll().

Members:

• cloudabi_userdata_t userdata

  User-provided value that got attached to cloudabi_subscription_t::userdata.

• cloudabi_errno_t error

  If non-zero, an error that occurred while processing the subscription request.

• cloudabi_eventtype_t type

  The type of the event that occurred.

• When type is CLOUDABI_EVENTTYPE_FD_READ or CLOUDABI_EVENTTYPE_FD_WRITE:

  • fd_readwrite

    • cloudabi_filesize_t nbytes

      The number of bytes available for reading or writing.

    • char unused[4]

      Obsolete.

    • cloudabi_eventrwflags_t flags

      The state of the file descriptor.

• When type is CLOUDABI_EVENTTYPE_PROC_TERMINATE:

  • proc_terminate

    • char unused[4]

      Obsolete.

    • cloudabi_signal_t signal

      If zero, the process has exited. Otherwise, the signal condition causing it to terminated.

    • cloudabi_exitcode_t exitcode

      If exited, the exit code of the process.

cloudabi_eventrwflags_t (uint16_t bitfield)

The state of the file descriptor subscribed to with CLOUDABI_EVENTTYPE_FD_READ or CLOUDABI_EVENTTYPE_FD_WRITE.

Used by cloudabi_event_t.

Possible values:

• CLOUDABI_EVENT_FD_READWRITE_HANGUP

  The peer of this socket has closed or disconnected.

cloudabi_eventtype_t (uint8_t)

Type of a subscription to an event or its occurrence.

Used by cloudabi_event_t and cloudabi_subscription_t.

Possible values:

• CLOUDABI_EVENTTYPE_CLOCK

  The time value of clock cloudabi_subscription_t::clock.clock_id has reached timestamp cloudabi_subscription_t::clock.timeout.

• CLOUDABI_EVENTTYPE_CONDVAR

  Condition variable cloudabi_subscription_t::condvar.condvar has been woken up and cloudabi_subscription_t::condvar.lock has been acquired for writing.

• CLOUDABI_EVENTTYPE_FD_READ

  File descriptor cloudabi_subscription_t::fd_readwrite.fd has data available for reading. This event always triggers for regular files.

• CLOUDABI_EVENTTYPE_FD_WRITE

  File descriptor cloudabi_subscription_t::fd_readwrite.fd has capacity available for writing. This event always triggers for regular files.

• CLOUDABI_EVENTTYPE_LOCK_RDLOCK

  Lock cloudabi_subscription_t::lock.lock has been acquired for reading.

• CLOUDABI_EVENTTYPE_LOCK_WRLOCK

  Lock cloudabi_subscription_t::lock.lock has been acquired for writing.

• CLOUDABI_EVENTTYPE_PROC_TERMINATE

  The process associated with process descriptor cloudabi_subscription_t::proc_terminate.fd has terminated.

cloudabi_exitcode_t (uint32_t)

Exit code generated by a process when exiting.

Used by cloudabi_event_t and cloudabi_sys_proc_exit().

cloudabi_fd_t (uint32_t)

A file descriptor number.

Unlike on POSIX-compliant systems, none of the file descriptor numbers are reserved for a purpose (e.g., stdin, stdout, stderr). Operating systems are not required to allocate new file descriptors in ascending order.

Special values:

• CLOUDABI_PROCESS_CHILD

  Returned to the child process by cloudabi_sys_proc_fork().

• CLOUDABI_MAP_ANON_FD

  Passed to cloudabi_sys_mem_map() when creating a mapping to anonymous memory.

cloudabi_fdflags_t (uint16_t bitfield)

File descriptor flags.

Used by cloudabi_fdstat_t.

Possible values:

• CLOUDABI_FDFLAG_APPEND

  Append mode: Data written to the file is always appended to the file's end.

• CLOUDABI_FDFLAG_DSYNC

  Write according to synchronized I/O data integrity completion. Only the data stored in the file is synchronized.

• CLOUDABI_FDFLAG_NONBLOCK

  Non-blocking mode.

• CLOUDABI_FDFLAG_RSYNC

  Synchronized read I/O operations.

• CLOUDABI_FDFLAG_SYNC

  Write according to synchronized I/O file integrity completion. In addition to synchronizing the data stored in the file, the system may also synchronously update the file's metadata.

cloudabi_fdsflags_t (uint16_t bitfield)

Which file descriptor attributes to adjust.

Used by cloudabi_sys_fd_stat_put().

Possible values:

• CLOUDABI_FDSTAT_FLAGS

  Adjust the file descriptor flags stored in cloudabi_fdstat_t::fs_flags.

• CLOUDABI_FDSTAT_RIGHTS

  Restrict the rights of the file descriptor to the rights stored in cloudabi_fdstat_t::fs_rights_base and cloudabi_fdstat_t::fs_rights_inheriting.

cloudabi_fdstat_t (struct)

File descriptor attributes.

Used by cloudabi_sys_fd_stat_get(), cloudabi_sys_fd_stat_put(), and cloudabi_sys_file_open().

Members:

• cloudabi_filetype_t fs_filetype

  File type.

• cloudabi_fdflags_t fs_flags

  File descriptor flags.

• cloudabi_rights_t fs_rights_base

  Rights that apply to this file descriptor.

• cloudabi_rights_t fs_rights_inheriting

  Maximum set of rights that can be installed on new file descriptors that are created through this file descriptor, e.g., through cloudabi_sys_file_open().

cloudabi_filedelta_t (int64_t)

Relative offset within a file.

Used by cloudabi_sys_fd_seek().

cloudabi_filesize_t (uint64_t)

Non-negative file size or length of a region within a file.

Used by cloudabi_event_t, cloudabi_filestat_t, cloudabi_sys_fd_pread(), cloudabi_sys_fd_pwrite(), cloudabi_sys_fd_seek(), cloudabi_sys_file_advise(), cloudabi_sys_file_allocate(), and cloudabi_sys_mem_map().

cloudabi_filestat_t (struct)

File attributes.

Used by cloudabi_sys_file_stat_fget(), cloudabi_sys_file_stat_fput(), cloudabi_sys_file_stat_get(), and cloudabi_sys_file_stat_put().

Members:

• cloudabi_device_t st_dev

  Device ID of device containing the file.

• cloudabi_inode_t st_ino

  File serial number.

• cloudabi_filetype_t st_filetype

  File type.

• cloudabi_linkcount_t st_nlink

  Number of hard links to the file.

• cloudabi_filesize_t st_size

  For regular files, the file size in bytes. For symbolic links, the length in bytes of the pathname contained in the symbolic link.

• cloudabi_timestamp_t st_atim

  Last data access timestamp.

• cloudabi_timestamp_t st_mtim

  Last data modification timestamp.

• cloudabi_timestamp_t st_ctim

  Last file status change timestamp.

cloudabi_filetype_t (uint8_t)

The type of a file descriptor or file.

Used by cloudabi_dirent_t, cloudabi_fdstat_t, cloudabi_filestat_t, cloudabi_sys_fd_create1(), cloudabi_sys_fd_create2(), and cloudabi_sys_file_create().

Possible values:

• CLOUDABI_FILETYPE_UNKNOWN

  The type of the file descriptor or file is unknown or is different from any of the other types specified.

• CLOUDABI_FILETYPE_BLOCK_DEVICE

  The file descriptor or file refers to a block device inode.

• CLOUDABI_FILETYPE_CHARACTER_DEVICE

  The file descriptor or file refers to a character device inode.

• CLOUDABI_FILETYPE_DIRECTORY

  The file descriptor or file refers to a directory inode.

• CLOUDABI_FILETYPE_PROCESS

  The file descriptor refers to a process handle.

• CLOUDABI_FILETYPE_REGULAR_FILE

  The file descriptor or file refers to a regular file inode.

• CLOUDABI_FILETYPE_SHARED_MEMORY

  The file descriptor refers to a shared memory object.

• CLOUDABI_FILETYPE_SOCKET_DGRAM

  The file descriptor or file refers to a datagram socket.

• CLOUDABI_FILETYPE_SOCKET_STREAM

  The file descriptor or file refers to a byte-stream socket.

• CLOUDABI_FILETYPE_SYMBOLIC_LINK

  The file refers to a symbolic link inode.

cloudabi_fsflags_t (uint16_t bitfield)

Which file attributes to adjust.

Used by cloudabi_sys_file_stat_fput() and cloudabi_sys_file_stat_put().

Possible values:

• CLOUDABI_FILESTAT_ATIM

  Adjust the last data access timestamp to the value stored in cloudabi_filestat_t::st_atim.

• CLOUDABI_FILESTAT_ATIM_NOW

  Adjust the last data access timestamp to the time of clock CLOUDABI_CLOCK_REALTIME.

• CLOUDABI_FILESTAT_MTIM

  Adjust the last data modification timestamp to the value stored in cloudabi_filestat_t::st_mtim.

• CLOUDABI_FILESTAT_MTIM_NOW

  Adjust the last data modification timestamp to the time of clock CLOUDABI_CLOCK_REALTIME.

• CLOUDABI_FILESTAT_SIZE

  Truncate or extend the file to the size stored in cloudabi_filestat_t::st_size.

cloudabi_inode_t (uint64_t)

File serial number that is unique within its file system.

Used by cloudabi_dirent_t and cloudabi_filestat_t.

cloudabi_iovec_t (struct)

A region of memory for scatter/gather reads.

Used by cloudabi_recv_in_t, cloudabi_sys_fd_pread(), and cloudabi_sys_fd_read().

Members:

• void *buf and size_t buf_len

  The address and length of the buffer to be filled.

cloudabi_linkcount_t (uint32_t)

Number of hard links to an inode.

Used by cloudabi_filestat_t.

cloudabi_lock_t (uint32_t)

A userspace read-recursive readers-writer lock, similar to a Linux futex or a FreeBSD umtx.

Used by cloudabi_subscription_t, cloudabi_sys_lock_unlock(), and cloudabi_sys_thread_exit().

Special values:

• CLOUDABI_LOCK_UNLOCKED

  Value indicating that the lock is in its initial unlocked state.

• CLOUDABI_LOCK_WRLOCKED

  Bitmask indicating that the lock is write-locked. If set, the lower 30 bits of the lock contain the identifier of the thread that owns the write lock. Otherwise, the lower 30 bits of the lock contain the number of acquired read locks.

• CLOUDABI_LOCK_KERNEL_MANAGED

  Bitmask indicating that the lock is either read locked or write locked, and that one or more threads have their execution suspended, waiting to acquire the lock. The last owner of the lock must call the kernel to unlock.

  When the lock is acquired for reading and this bit is set, it means that one or more threads are attempting to acquire this lock for writing. In that case, other threads should only acquire additional read locks if suspending execution would cause a deadlock. It is preferred to suspend execution, as this prevents starvation of writers.

• CLOUDABI_LOCK_BOGUS

  Value indicating that the lock is in an incorrect state. A lock cannot be in its initial unlocked state, while also managed by the kernel.

cloudabi_lookup_t (struct)

Path lookup properties.

Used by cloudabi_sys_file_link(), cloudabi_sys_file_open(), cloudabi_sys_file_stat_get(), and cloudabi_sys_file_stat_put().

Members:

• cloudabi_fd_t fd

  The working directory at which the resolution of the path starts.

• cloudabi_lookupflags_t flags

  Flags determining the method of how the path is resolved.

cloudabi_lookupflags_t (uint32_t bitfield)

Flags determining the method of how paths are resolved.

Used by cloudabi_lookup_t.

Possible values:

• CLOUDABI_LOOKUP_SYMLINK_FOLLOW

  As long as the resolved path corresponds to a symbolic link, it is expanded.

cloudabi_mflags_t (uint8_t bitfield)

Memory mapping flags.

Used by cloudabi_sys_mem_map().

Possible values:

• CLOUDABI_MAP_ANON

  Instead of mapping the contents of the file provided, create a mapping to anonymous memory. The file descriptor argument must be set to CLOUDABI_MAP_ANON_FD, and the offset must be set to zero.

• CLOUDABI_MAP_FIXED

  Require that the mapping is performed at the base address provided.

• CLOUDABI_MAP_PRIVATE

  Changes are private.

• CLOUDABI_MAP_SHARED

  Changes are shared.

cloudabi_mprot_t (uint8_t bitfield)

Memory page protection options.

This implementation enforces the W^X property: Pages cannot be mapped for execution while also mapped for writing.

Used by cloudabi_sys_mem_map() and cloudabi_sys_mem_protect().

Possible values:

• CLOUDABI_PROT_EXEC

  Page can be executed.

• CLOUDABI_PROT_WRITE

  Page can be written.

• CLOUDABI_PROT_READ

  Page can be read.

cloudabi_msflags_t (uint8_t bitfield)

Methods of synchronizing memory with physical storage.

Used by cloudabi_sys_mem_sync().

Possible values:

• CLOUDABI_MS_ASYNC

  Perform asynchronous writes.

• CLOUDABI_MS_INVALIDATE

  Invalidate cached data.

• CLOUDABI_MS_SYNC

  Perform synchronous writes.

cloudabi_nthreads_t (uint32_t)

Specifies the number of threads sleeping on a condition variable that should be woken up.

Used by cloudabi_sys_condvar_signal().

cloudabi_oflags_t (uint16_t bitfield)

Open flags used by cloudabi_sys_file_open().

Possible values:

• CLOUDABI_O_CREAT

  Create file if it does not exist.

• CLOUDABI_O_DIRECTORY

  Fail if not a directory.

• CLOUDABI_O_EXCL

  Fail if file already exists.

• CLOUDABI_O_TRUNC

  Truncate file to size 0.

cloudabi_processentry_t (function type)

Entry point for a process (_start).

Parameters:

• const cloudabi_auxv_t *auxv

  The auxiliary vector. See cloudabi_auxv_t.

cloudabi_recv_in_t (struct)

Arguments of cloudabi_sys_sock_recv().

Members:

• const cloudabi_iovec_t *ri_data and size_t ri_data_len

  List of scatter/gather vectors where message data should be stored.

• cloudabi_fd_t *ri_fds and size_t ri_fds_len

  Buffer where numbers of incoming file descriptors should be stored.

• cloudabi_riflags_t ri_flags

  Message flags.

cloudabi_recv_out_t (struct)

Results of cloudabi_sys_sock_recv().

Members:

• size_t ro_datalen

  Number of bytes stored in cloudabi_recv_in_t::ri_data.

• size_t ro_fdslen

  Number of file descriptors stored in cloudabi_recv_in_t::ri_fds.

• char ro_unused[40]

  Fields that were used by previous implementations.

• cloudabi_roflags_t ro_flags

  Message flags.

cloudabi_riflags_t (uint16_t bitfield)

Flags provided to cloudabi_sys_sock_recv().

Used by cloudabi_recv_in_t.

Possible values:

• CLOUDABI_SOCK_RECV_PEEK

  Returns the message without removing it from the socket's receive queue.

• CLOUDABI_SOCK_RECV_WAITALL

  On byte-stream sockets, block until the full amount of data can be returned.

cloudabi_rights_t (uint64_t bitfield)

File descriptor rights, determining which actions may be performed.

Used by cloudabi_fdstat_t.

Possible values:

• CLOUDABI_RIGHT_FD_DATASYNC

  The right to invoke cloudabi_sys_fd_datasync().

  If CLOUDABI_RIGHT_FILE_OPEN is set, includes the right to invoke cloudabi_sys_file_open() with CLOUDABI_FDFLAG_DSYNC.

• CLOUDABI_RIGHT_FD_READ

  The right to invoke cloudabi_sys_fd_read() and cloudabi_sys_sock_recv().

  If CLOUDABI_RIGHT_MEM_MAP is set, includes the right to invoke cloudabi_sys_mem_map() with memory protection option CLOUDABI_PROT_READ.

  If CLOUDABI_RIGHT_FD_SEEK is set, includes the right to invoke cloudabi_sys_fd_pread().

• CLOUDABI_RIGHT_FD_SEEK

  The right to invoke cloudabi_sys_fd_seek(). This flag implies CLOUDABI_RIGHT_FD_TELL.

• CLOUDABI_RIGHT_FD_STAT_PUT_FLAGS

  The right to invoke cloudabi_sys_fd_stat_put() with CLOUDABI_FDSTAT_FLAGS.

• CLOUDABI_RIGHT_FD_SYNC

  The right to invoke cloudabi_sys_fd_sync().

  If CLOUDABI_RIGHT_FILE_OPEN is set, includes the right to invoke cloudabi_sys_file_open() with CLOUDABI_FDFLAG_RSYNC and CLOUDABI_FDFLAG_DSYNC.

• CLOUDABI_RIGHT_FD_TELL

  The right to invoke cloudabi_sys_fd_seek() in such a way that the file offset remains unaltered (i.e., CLOUDABI_WHENCE_CUR with offset zero).

• CLOUDABI_RIGHT_FD_WRITE

  The right to invoke cloudabi_sys_fd_write() and cloudabi_sys_sock_send().

  If CLOUDABI_RIGHT_MEM_MAP is set, includes the right to invoke cloudabi_sys_mem_map() with memory protection option CLOUDABI_PROT_WRITE.

  If CLOUDABI_RIGHT_FD_SEEK is set, includes the right to invoke cloudabi_sys_fd_pwrite().

• CLOUDABI_RIGHT_FILE_ADVISE

  The right to invoke cloudabi_sys_file_advise().

• CLOUDABI_RIGHT_FILE_ALLOCATE

  The right to invoke cloudabi_sys_file_allocate().

• CLOUDABI_RIGHT_FILE_CREATE_DIRECTORY

  The right to invoke cloudabi_sys_file_create() with CLOUDABI_FILETYPE_DIRECTORY.

• CLOUDABI_RIGHT_FILE_CREATE_FILE

  If CLOUDABI_RIGHT_FILE_OPEN is set, the right to invoke cloudabi_sys_file_open() with CLOUDABI_O_CREAT.

• CLOUDABI_RIGHT_FILE_LINK_SOURCE

  The right to invoke cloudabi_sys_file_link() with the file descriptor as the source directory.

• CLOUDABI_RIGHT_FILE_LINK_TARGET

  The right to invoke cloudabi_sys_file_link() with the file descriptor as the target directory.

• CLOUDABI_RIGHT_FILE_OPEN

  The right to invoke cloudabi_sys_file_open().

• CLOUDABI_RIGHT_FILE_READDIR

  The right to invoke cloudabi_sys_file_readdir().

• CLOUDABI_RIGHT_FILE_READLINK

  The right to invoke cloudabi_sys_file_readlink().

• CLOUDABI_RIGHT_FILE_RENAME_SOURCE

  The right to invoke cloudabi_sys_file_rename() with the file descriptor as the source directory.

• CLOUDABI_RIGHT_FILE_RENAME_TARGET

  The right to invoke cloudabi_sys_file_rename() with the file descriptor as the target directory.

• CLOUDABI_RIGHT_FILE_STAT_FGET

  The right to invoke cloudabi_sys_file_stat_fget().

• CLOUDABI_RIGHT_FILE_STAT_FPUT_SIZE

  The right to invoke cloudabi_sys_file_stat_fput() with CLOUDABI_FILESTAT_SIZE.

  If CLOUDABI_RIGHT_FILE_OPEN is set, includes the right to invoke cloudabi_sys_file_open() with CLOUDABI_O_TRUNC.

• CLOUDABI_RIGHT_FILE_STAT_FPUT_TIMES

  The right to invoke cloudabi_sys_file_stat_fput() with CLOUDABI_FILESTAT_ATIM, CLOUDABI_FILESTAT_ATIM_NOW, CLOUDABI_FILESTAT_MTIM, and CLOUDABI_FILESTAT_MTIM_NOW.

• CLOUDABI_RIGHT_FILE_STAT_GET

  The right to invoke cloudabi_sys_file_stat_get().

• CLOUDABI_RIGHT_FILE_STAT_PUT_TIMES

  The right to invoke cloudabi_sys_file_stat_put() with CLOUDABI_FILESTAT_ATIM, CLOUDABI_FILESTAT_ATIM_NOW, CLOUDABI_FILESTAT_MTIM, and CLOUDABI_FILESTAT_MTIM_NOW.

• CLOUDABI_RIGHT_FILE_SYMLINK

  The right to invoke cloudabi_sys_file_symlink().

• CLOUDABI_RIGHT_FILE_UNLINK

  The right to invoke cloudabi_sys_file_unlink().

• CLOUDABI_RIGHT_MEM_MAP

  The right to invoke cloudabi_sys_mem_map() with cloudabi_mprot_t set to zero.

• CLOUDABI_RIGHT_MEM_MAP_EXEC

  If CLOUDABI_RIGHT_MEM_MAP is set, the right to invoke cloudabi_sys_mem_map() with CLOUDABI_PROT_EXEC.

• CLOUDABI_RIGHT_POLL_FD_READWRITE

  If CLOUDABI_RIGHT_FD_READ is set, includes the right to invoke cloudabi_sys_poll() to subscribe to CLOUDABI_EVENTTYPE_FD_READ.

  If CLOUDABI_RIGHT_FD_WRITE is set, includes the right to invoke cloudabi_sys_poll() to subscribe to CLOUDABI_EVENTTYPE_FD_WRITE.

• CLOUDABI_RIGHT_POLL_PROC_TERMINATE

  The right to invoke cloudabi_sys_poll() to subscribe to CLOUDABI_EVENTTYPE_PROC_TERMINATE.

• CLOUDABI_RIGHT_PROC_EXEC

  The right to invoke cloudabi_sys_proc_exec().

• CLOUDABI_RIGHT_SOCK_SHUTDOWN

  The right to invoke cloudabi_sys_sock_shutdown().

cloudabi_roflags_t (uint16_t bitfield)

Flags returned by cloudabi_sys_sock_recv().

Used by cloudabi_recv_out_t.

Possible values:

• CLOUDABI_SOCK_RECV_FDS_TRUNCATED

  Returned by cloudabi_sys_sock_recv(): List of file descriptors has been truncated.

• CLOUDABI_SOCK_RECV_DATA_TRUNCATED

  Returned by cloudabi_sys_sock_recv(): Message data has been truncated.

cloudabi_scope_t (uint8_t)

Indicates whether an object is stored in private or shared memory.

Used by cloudabi_subscription_t, cloudabi_sys_condvar_signal(), cloudabi_sys_lock_unlock(), and cloudabi_sys_thread_exit().

Possible values:

• CLOUDABI_SCOPE_PRIVATE

  The object is stored in private memory.

• CLOUDABI_SCOPE_SHARED

  The object is stored in shared memory.

cloudabi_sdflags_t (uint8_t bitfield)

Which channels on a socket need to be shut down.

Used by cloudabi_sys_sock_shutdown().

Possible values:

• CLOUDABI_SHUT_RD

  Disables further receive operations.

• CLOUDABI_SHUT_WR

  Disables further send operations.

cloudabi_send_in_t (struct)

Arguments of cloudabi_sys_sock_send().

Members:

• const cloudabi_ciovec_t *si_data and size_t si_data_len

  List of scatter/gather vectors where message data should be retrieved.

• const cloudabi_fd_t *si_fds and size_t si_fds_len

  File descriptors that need to be attached to the message.

• cloudabi_siflags_t si_flags

  Message flags.

cloudabi_send_out_t (struct)

Results of cloudabi_sys_sock_send().

Members:

• size_t so_datalen

  Number of bytes transmitted.

cloudabi_siflags_t (uint16_t bitfield)

Flags provided to cloudabi_sys_sock_send(). As there are currently no flags defined, it must be set to zero.

Used by cloudabi_send_in_t.

cloudabi_signal_t (uint8_t)

Signal condition.

Used by cloudabi_event_t and cloudabi_sys_proc_raise().

Possible values:

• CLOUDABI_SIGABRT

  Process abort signal.

  Action: Terminates the process.

• CLOUDABI_SIGALRM

  Alarm clock.

  Action: Terminates the process.

• CLOUDABI_SIGBUS

  Access to an undefined portion of a memory object.

  Action: Terminates the process.

• CLOUDABI_SIGCHLD

  Child process terminated, stopped, or continued.

  Action: Ignored.

• CLOUDABI_SIGCONT

  Continue executing, if stopped.

  Action: Continues executing, if stopped.

• CLOUDABI_SIGFPE

  Erroneous arithmetic operation.

  Action: Terminates the process.

• CLOUDABI_SIGHUP

  Hangup.

  Action: Terminates the process.

• CLOUDABI_SIGILL

  Illegal instruction.

  Action: Terminates the process.

• CLOUDABI_SIGINT

  Terminate interrupt signal.

  Action: Terminates the process.

• CLOUDABI_SIGKILL

  Kill.

  Action: Terminates the process.

• CLOUDABI_SIGPIPE

  Write on a pipe with no one to read it.

  Action: Ignored.

• CLOUDABI_SIGQUIT

  Terminal quit signal.

  Action: Terminates the process.

• CLOUDABI_SIGSEGV

  Invalid memory reference.

  Action: Terminates the process.

• CLOUDABI_SIGSTOP

  Stop executing.

  Action: Stops executing.

• CLOUDABI_SIGSYS

  Bad system call.

  Action: Terminates the process.

• CLOUDABI_SIGTERM

  Termination signal.

  Action: Terminates the process.

• CLOUDABI_SIGTRAP

  Trace/breakpoint trap.

  Action: Terminates the process.

• CLOUDABI_SIGTSTP

  Terminal stop signal.

  Action: Stops executing.

• CLOUDABI_SIGTTIN

  Background process attempting read.

  Action: Stops executing.

• CLOUDABI_SIGTTOU

  Background process attempting write.

  Action: Stops executing.

• CLOUDABI_SIGURG

  High bandwidth data is available at a socket.

  Action: Ignored.

• CLOUDABI_SIGUSR1

  User-defined signal 1.

  Action: Terminates the process.

• CLOUDABI_SIGUSR2

  User-defined signal 2.

  Action: Terminates the process.

• CLOUDABI_SIGVTALRM

  Virtual timer expired.

  Action: Terminates the process.

• CLOUDABI_SIGXCPU

  CPU time limit exceeded.

  Action: Terminates the process.

• CLOUDABI_SIGXFSZ

  File size limit exceeded.

  Action: Terminates the process.

cloudabi_subclockflags_t (uint16_t bitfield)

Flags determining how the timestamp provided in cloudabi_subscription_t::clock.timeout should be interpreted.

Used by cloudabi_subscription_t.

Possible values:

• CLOUDABI_SUBSCRIPTION_CLOCK_ABSTIME

  If set, treat the timestamp provided in cloudabi_subscription_t::clock.timeout as an absolute timestamp of clock cloudabi_subscription_t::clock.clock_id.

  If clear, treat the timestamp provided in cloudabi_subscription_t::clock.timeout relative to the current time value of clock cloudabi_subscription_t::clock.clock_id.

cloudabi_subrwflags_t (uint16_t bitfield)

Flags influencing the method of polling for read or writing on a file descriptor.

Used by cloudabi_subscription_t.

Possible values:

• CLOUDABI_SUBSCRIPTION_FD_READWRITE_POLL

  Deprecated. Must be set by callers and ignored by implementations.

cloudabi_subscription_t (struct)

Subscription to an event.

Used by cloudabi_sys_poll().

Members:

• cloudabi_userdata_t userdata

  User-provided value that is attached to the subscription in the kernel and returned through cloudabi_event_t::userdata.

• uint16_t unused

  Used by previous implementations. Ignored.

• cloudabi_eventtype_t type

  The type of the event to which to subscribe.

  Currently, CLOUDABI_EVENTTYPE_CONDVAR, CLOUDABI_EVENTTYPE_LOCK_RDLOCK, and CLOUDABI_EVENTTYPE_LOCK_WRLOCK must be provided as the first subscription and may only be followed by up to one other subscription, having type CLOUDABI_EVENTTYPE_CLOCK.

• When type is CLOUDABI_EVENTTYPE_CLOCK:

  • clock

    • cloudabi_userdata_t identifier

      The user-defined unique identifier of the clock.

    • cloudabi_clockid_t clock_id

      The clock against which the timestamp should be compared.

    • cloudabi_timestamp_t timeout

      The absolute or relative timestamp.

    • cloudabi_timestamp_t precision

      The amount of time that the kernel may wait additionally to coalesce with other events.

    • cloudabi_subclockflags_t flags

      Flags specifying whether the timeout is absolute or relative.

• When type is CLOUDABI_EVENTTYPE_CONDVAR:

  • condvar

    • _Atomic(cloudabi_condvar_t) *condvar

      The condition variable on which to wait to be woken up.

    • _Atomic(cloudabi_lock_t) *lock

      The lock that will be released while waiting.

      The lock will be reacquired for writing when the condition variable triggers.

    • cloudabi_scope_t condvar_scope

      Whether the condition variable is stored in private or shared memory.

    • cloudabi_scope_t lock_scope

      Whether the lock is stored in private or shared memory.

• When type is CLOUDABI_EVENTTYPE_FD_READ or CLOUDABI_EVENTTYPE_FD_WRITE:

  • fd_readwrite

    • cloudabi_fd_t fd

      The file descriptor on which to wait for it to become ready for reading or writing.

    • cloudabi_subrwflags_t flags

      Under which conditions to trigger.

• When type is CLOUDABI_EVENTTYPE_LOCK_RDLOCK or CLOUDABI_EVENTTYPE_LOCK_WRLOCK:

  • lock

    • _Atomic(cloudabi_lock_t) *lock

      The lock that will be acquired for reading or writing.

    • cloudabi_scope_t lock_scope

      Whether the lock is stored in private or shared memory.

• When type is CLOUDABI_EVENTTYPE_PROC_TERMINATE:

  • proc_terminate

    • cloudabi_fd_t fd

      The process descriptor on which to wait for process termination.

cloudabi_tcb_t (struct)

The Thread Control Block (TCB).

After a thread begins execution (at program startup or when created through cloudabi_sys_thread_create()), the CPU's registers controlling Thread-Local Storage (TLS) will already be initialized. They will point to an area only containing the TCB.

If the thread needs space for storing thread-specific variables, the thread may allocate a larger area and adjust the CPU's registers to point to that area instead. However, it does need to make sure that the TCB is copied over to the new TLS area.

The purpose of the TCB is that it allows light-weight emulators to store information related to individual threads. For example, it may be used to store a copy of the CPU registers prior emulation, so that TLS for the host system can be restored if needed.

Members:

• void *parent

  Pointer that may be freely assigned by the system. Its value cannot be interpreted by the application.

cloudabi_threadattr_t (struct)

Attributes for thread creation.

Used by cloudabi_sys_thread_create().

Members:

• cloudabi_threadentry_t *entry_point

  Initial program counter value.

• void *stack and size_t stack_len

  Region allocated to serve as stack space.

• void *argument

  Argument to be forwarded to the entry point function.

cloudabi_threadentry_t (function type)

Entry point for additionally created threads.

Used by cloudabi_threadattr_t.

Parameters:

• cloudabi_tid_t tid

  Thread ID of the current thread.

• void *aux

  Copy of the value stored in cloudabi_threadattr_t::argument.

cloudabi_tid_t (uint32_t)

Unique system-local identifier of a thread. This identifier is only valid during the lifetime of the thread.

Threads must be aware of their thread identifier, as it is written it into locks when acquiring them for writing. It is not advised to use these identifiers for any other purpose.

As the thread identifier is also stored in cloudabi_lock_t when CLOUDABI_LOCK_WRLOCKED is set, the top two bits of the thread must always be set to zero.

Used by cloudabi_threadentry_t, cloudabi_sys_proc_fork(), and cloudabi_sys_thread_create().

cloudabi_timestamp_t (uint64_t)

Timestamp in nanoseconds.

Used by cloudabi_filestat_t, cloudabi_subscription_t, cloudabi_sys_clock_res_get(), and cloudabi_sys_clock_time_get().

cloudabi_ulflags_t (uint8_t bitfield)

Specifies whether files are unlinked or directories are removed.

Used by cloudabi_sys_file_unlink().

Possible values:

• CLOUDABI_UNLINK_REMOVEDIR

  If set, removes a directory. Otherwise, unlinks any non-directory file.

cloudabi_userdata_t (uint64_t)

User-provided value that can be attached to objects that is retained when extracted from the kernel.

Used by cloudabi_event_t and cloudabi_subscription_t.

cloudabi_whence_t (uint8_t)

Relative to which position the offset of the file descriptor should be set.

Used by cloudabi_sys_fd_seek().

Possible values:

• CLOUDABI_WHENCE_CUR

  Seek relative to current position.

• CLOUDABI_WHENCE_END

  Seek relative to end-of-file.

• CLOUDABI_WHENCE_SET

  Seek relative to start-of-file.