ucontext - user context
The thread of control within an executing process is specified by the ucon-
text structure. This structure contains at least the following members:
The values for each member is as follows:
Points to the context that is to continue when this context returns. If
uc_link is equal to zero (0), this is the main context, and the process
exits when this context returns.
Specifies the set of signals that are blocked when this context is
active. See sigprocmask(2) for more information.
Specifies the stack used by this context. See sigaltstack(2) for more
Contains the saved machine registers and any implementation-specific
Portable applications should not access or modify the uc_mcontext value in
the ucontext structure.
Functions: getcontext(2), sigaction(2), sigprocmask(2), sigaltstack(2).