Introduction to Library Functions      sigsegv_install_handler(3)



NAME
     sigsegv_install_handler, sigsegv_deinstall_handler - Install
     and deinstall a global SIGSEGV handler


SYNOPSIS
     #include <sigsegv.h>

     int sigsegv_install_handler (sigsegv_handler_t handler);

     void sigsegv_deinstall_handler (void);


DESCRIPTION
     Pageable virtual memory is usually  done  in  the  operating
     system's kernel. This library helps in implementing the oth-
     ers.


     Installing a page fault handler is  usually  more  efficient
     than  doing  access  checks  in  software  at  every access,
     because it's effectively the hardware (the MMU) which checks
     whether a page is present or not.


     Note that if you use system calls  (like  read())  to  write
     into write-protected pages, the system will react by return-
     ing -1 and setting errno to EFAULT,  instead  of  signalling
     SIGSEGV  and  restarting  the system call. In this case, the
     program has to do what the SIGSEGV  handler  would  do,  and
     then restart the read() operation.


     Sigsegv_install_handler installs a global  SIGSEGV  handler.
     This  should  be called once only, and it ignores any previ-
     ously installed SIGSEGV handler.


     Sigsegv_deinstall_handler  deinstalls  the  global   SIGSEGV
     handler.  This  goes  back  to  the  state  where no SIGSEGV
     handler is installed.


OPERANDS
     typedef int (*sigsegv_handler_t) (void* fault_address,
                                       int serious);

     Sigsegv_handler_t  is  the  type   of   a   global   SIGSEGV
     handler.The  fault address is passed as argument. The access
     type (read access or  write  access)  is  not  passed;  your
     handler  has  to  know  itself  how to distinguish these two
     cases. The second argument is 0, meaning it could also be  a



SunOS 5.11          Last change: 13 Jan 2009                    1






Introduction to Library Functions      sigsegv_install_handler(3)



     stack  overflow,  or 1, meaning the handler should seriously
     try to fix the fault. The return value should be nonzero  if
     the  handler has done its job and no other handler should be
     called, or 0 if the handler declines responsibility for  the
     given address.


     The handler is run at a moment when nothing about the global
     state  of  the  program  is  known.  Therefore it cannot use
     facilities that manipulate global  variables  or  locks.  In
     particular,  it  cannot use malloc(); use mmap() instead. It
     cannot use fopen(); use  open()  instead.  Etc.  All  global
     variables  that are accessed by the handler should be marked
     'volatile'.


EXIT STATUS
     If success, sigsegv_install_handler returns 0, or -1 if  the
     system doesn't support catching SIGSEGV.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWlibsigsegv              |
    |_____________________________|_____________________________|
    | Interface Stability         | Uncommitted                 |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


SEE ALSO
     attributes(5), sigsegv(3), standards(5)


NOTES
     The     libsigsegv      project      is      located      at
     http://libsigsegv.sourceforge.net.

     Source     for     libsigsegv      is      available      on
     http://opensolaris.org.









SunOS 5.11          Last change: 13 Jan 2009                    2