SIGRETURN(2)              FreeBSD System Calls Manual             SIGRETURN(2)

NAME
     sigreturn - return from signal

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <signal.h>

     int
     sigreturn(const ucontext_t *scp);

DESCRIPTION
     The sigreturn() system call allows users to atomically unmask, switch
     stacks, and return from a signal context.  The thread's signal mask and
     stack status are restored from the context structure pointed to by scp.
     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 specified pc.  This system call is
     used by the trampoline code and longjmp(3) when returning from a signal
     to the previously executing program.

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

ERRORS
     The sigreturn() system call will fail and the thread context will remain
     unchanged if one of the following occurs.

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

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

SEE ALSO
     sigaction(2), setjmp(3), ucontext(3)

HISTORY
     The sigreturn() system call appeared in 4.3BSD.

FreeBSD 13.1-RELEASE-p6        September 6, 2013       FreeBSD 13.1-RELEASE-p6