sigreturn(2) [freebsd man page]

SIGRETURN(2)						      BSD 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.

BSD
								 September 6, 2013							       BSD

SIGRETURN(2)						     Linux Programmer's Manual						      SIGRETURN(2)

NAME

       sigreturn - return from signal handler and cleanup stack frame

SYNOPSIS

       int sigreturn(unsigned long __unused);

DESCRIPTION

       When  the  Linux  kernel  creates the stack frame for a signal handler, a call to sigreturn() is inserted into the stack frame so that upon
       return from the signal handler, sigreturn() will be called.

       This sigreturn() call undoes everything that was done--changing the process's signal mask, switching stacks (see sigaltstack(2))--in  order
       to  invoke  the signal handler: it restores the process's signal mask, switches stacks, and restores the process's context (registers, pro-
       cessor flags), so that the process directly resumes execution at the point where it was interrupted by the signal.

RETURN VALUE

       sigreturn() never returns.

FILES

       /usr/src/linux/arch/i386/kernel/signal.c
       /usr/src/linux/arch/alpha/kernel/entry.S

CONFORMING TO

       sigreturn() is specific to Linux and should not be used in programs intended to be portable.

NOTES

       The sigreturn() call is used by the kernel to implement signal handlers.  It should never be called directly.  Better yet, the specific use
       of the __unused argument varies depending on the architecture.

SEE ALSO

       kill(2), sigaltstack(2), signal(2), signal(7)

COLOPHON

       This  page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-06-26							      SIGRETURN(2)