4.3BSD - /usr/man/cat2/sigreturn.0

SIGRETURN(2)                                                      SIGRETURN(2)


NAME
       sigreturn - return from signal

SYNOPSIS
       #include <signal.h>

       struct    sigcontext {
            int  sc_onstack;
            int  sc_mask;
            int  sc_sp;
            int  sc_fp;
            int  sc_ap;
            int  sc_pc;
            int  sc_ps;
       };

       sigreturn(scp);
       struct sigcontext *scp;

DESCRIPTION
       Sigreturn  allows users to atomically unmask, switch stacks, and return
       from a signal context.  The processes signal mask and stack status  are
       restored  from the context.  The system call does not return; the users
       stack pointer, frame pointer, argument pointer,  and  processor  status
       longword are restored from the context.  Execution resumes at the spec‐
       ified pc.  This system  call  is  used  by  the  trampoline  code,  and
       longjmp(3)  when  returning  from  a signal to the previously executing
       program.

NOTES
       This system call is not available in 4.2BSD, hence  it  should  not  be
       used if backward compatibility is needed.

RETURN VALUE
       If  successful, the system call does not return.  Otherwise, a value of
       -1 is returned and errno is set to indicate the error.

ERRORS
       Sigreturn will fail and the process context will  remain  unchanged  if
       one of the following occurs.

       [EFAULT]       Scp  points  to  memory  that is not a valid part of the
                      process address space.

       [EINVAL]       The process status longword is invalid or would  improp‐
                      erly raise the privilege level of the process.

SEE ALSO
       sigvec(2), setjmp(3)


4.3 Berkeley Distribution        June 30, 1985                    SIGRETURN(2)