source: branches/libc-0.6/src/gcc/libjava/include/powerpc-signal.h

// powerpc-signal.h - Catch runtime signals and turn them into exceptions
// on a powerpc based Linux system.

/* Copyright (C) 2003  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */


#ifndef JAVA_SIGNAL_H
# define JAVA_SIGNAL_H 1

# include <signal.h>
# include <sys/syscall.h>

# define HANDLE_SEGV 1
# undef HANDLE_FPE

# define SIGNAL_HANDLER(_name)                                          \
  static void _name (int /* _signal */, struct sigcontext *_sc)

/* PPC either leaves PC pointing at a faulting instruction or the
   following instruction, depending on the signal.  SEGV always does
   the former, so we adjust the saved PC to point to the following
   instruction. This is what the handler in libgcc expects.  */

# define MAKE_THROW_FRAME(_exception)                                   \
do                                                                      \
  {                                                                     \
    _sc->regs->nip += 4;                                                \
  }                                                                     \
while (0)
  
/* For an explanation why we cannot simply use sigaction to
   install the handlers, see i386-signal.h.  */

/* We use kernel_old_sigaction here because we're calling the kernel
   directly rather than via glibc. The sigaction structure that the
   syscall uses is a different shape from the one in userland and not
   visible to us in a header file so we define it here.
   Additionally we want a proper prototype for the handler function
   with the struct sigcontext pointer passed by the kernel as the 2nd
   argument, which isn't there in userland headers.

   Note that we explicitly avoid the SA_SIGINFO flag in INIT_SEGV and
   INIT_FPE below. Using the ucontext pointer passed as 3rd argument
   of a SA_SIGINFO type handler would need complicated backwards
   compatibility hacks in MAKE_THROW_FRAME, as the ucontext layout
   on PPC changed during the 2.5 kernel series.  */

struct kernel_old_sigaction {
  void (*k_sa_handler) (int, struct sigcontext *);
  unsigned long k_sa_mask;
  unsigned long k_sa_flags;
  void (*k_sa_restorer) (void);
};

# define INIT_SEGV                                                      \
do                                                                      \
  {                                                                     \
    nullp = new java::lang::NullPointerException ();                    \
    struct kernel_old_sigaction kact;                                   \
    kact.k_sa_handler = catch_segv;                                     \
    kact.k_sa_mask = 0;                                                 \
    kact.k_sa_flags = 0;                                                \
    syscall (SYS_sigaction, SIGSEGV, &kact, NULL);                      \
  }                                                                     \
while (0)  

# define INIT_FPE                                                       \
do                                                                      \
  {                                                                     \
    arithexception = new java::lang::ArithmeticException                \
      (JvNewStringLatin1 ("/ by zero"));                                \
    struct kernel_old_sigaction kact;                                   \
    kact.k_sa_handler = catch_fpe;                                      \
    kact.k_sa_mask = 0;                                                 \
    kact.k_sa_flags = 0;                                                \
    syscall (SYS_sigaction, SIGFPE, &kact, NULL);                       \
  }                                                                     \
while (0)  

#endif /* JAVA_SIGNAL_H */