libjava/include/i386-signal.h

   1 // i386-signal.h - Catch runtime signals and turn them into exceptions.
   2
   3 /* Copyright (C) 1998, 1999  Free Software Foundation
   4
   5    This file is part of libgcj.
   6
   7 This software is copyrighted work licensed under the terms of the
   8 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   9 details.  */
  10
  11 /* This technique should work for all i386 based Unices which conform
  12  * to iBCS2.  This includes all versions of Linux more recent than 1.3
  13  */
  14
  15
  16 #ifndef JAVA_SIGNAL_H
  17 #define JAVA_SIGNAL_H 1
  18
  19 #include <signal.h>
  20
  21 #define HANDLE_SEGV 1
  22 #define HANDLE_FPE 1
  23
  24 #define SIGNAL_HANDLER(_name)   \
  25 static void _name (int _dummy)
  26
  27 #define MAKE_THROW_FRAME                                                \
  28 do                                                                      \
  29 {                                                                       \
  30   void **_p = (void **)&_dummy;                                         \
  31   struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;   \
  32                                                                         \
  33   register unsigned long _ebp = _regs->ebp;                             \
  34   register unsigned char *_eip = (unsigned char *)_regs->eip;           \
  35                                                                         \
  36   /* Advance the program counter so that it is after the start of the   \
  37      instruction:  the x86 exception handler expects                    \
  38      the PC to point to the instruction after a call. */                \
  39   _eip += 2;                                                            \
  40                                                                         \
  41   asm volatile ("mov %0, (%%ebp); mov %1, 4(%%ebp)"                     \
  42                 : : "r"(_ebp), "r"(_eip));                              \
  43 }                                                                       \
  44 while (0)
  45
  46 #define HANDLE_DIVIDE_OVERFLOW                                          \
  47 do                                                                      \
  48 {                                                                       \
  49   void **_p = (void **)&_dummy;                                         \
  50   struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;   \
  51                                                                         \
  52   register unsigned long *_ebp = (unsigned long *)_regs->ebp;           \
  53   register unsigned char *_eip = (unsigned char *)_regs->eip;           \
  54                                                                         \
  55   /* According to the JVM spec, "if the dividend is the negative        \
  56    * integer of the smallest magnitude and the divisor is -1, then      \
  57    * overflow occurs and the result is equal to the dividend.  Despite  \
  58    * the overflow, no exception occurs".                                \
  59                                                                         \
  60    * We handle this by inspecting the instruction which generated the   \
  61    * signal and advancing eip to point to the following instruction.    \
  62    * As the instructions are variable length it is necessary to do a    \
  63    * little calculation to figure out where the following instruction   \
  64    * actually is.                                                       \
  65                                                                         \
  66    */                                                                   \
  67                                                                         \
  68   if (_eip[0] == 0xf7)                                                  \
  69     {                                                                   \
  70       unsigned char _modrm = _eip[1];                                   \
  71                                                                         \
  72       if (_regs->eax == 0x80000000                                      \
  73           && ((_modrm >> 3) & 7) == 7) /* Signed divide */              \
  74         {                                                               \
  75           _regs->edx = 0; /* the remainder is zero */                   \
  76           switch (_modrm >> 6)                                          \
  77             {                                                           \
  78             case 0:                                                     \
  79               if ((_modrm & 7) == 5)                                    \
  80                 _eip += 4;                                              \
  81               break;                                                    \
  82             case 1:                                                     \
  83               _eip += 1;                                                \
  84               break;                                                    \
  85             case 2:                                                     \
  86               _eip += 4;                                                \
  87               break;                                                    \
  88             case 3:                                                     \
  89               break;                                                    \
  90             }                                                           \
  91           _eip += 2;                                                    \
  92           _regs->eip = (unsigned long)_eip;                             \
  93           return;                                                       \
  94         }                                                               \
  95       else if (((_modrm >> 3) & 7) == 6) /* Unsigned divide */          \
  96         {                                                               \
  97           /* We assume that unsigned divisions are in library code, so  \
  98            * we throw one level down the stack, which was hopefully     \
  99            * the place that called the library routine.  This will      \
 100            * break if the library is ever compiled with                 \
 101            * -fomit-frame-pointer, but at least this way we've got a    \
 102            * good chance of finding the exception handler. */           \
 103                                                                         \
 104           _eip = (unsigned char *)_ebp[1];                              \
 105           _ebp = (unsigned long *)_ebp[0];                              \
 106         }                                                               \
 107       else                                                              \
 108         {                                                               \
 109           /* Advance the program counter so that it is after the start  \
 110              of the instruction: this is because the x86 exception      \
 111              handler expects the PC to point to the instruction after a \
 112              call. */                                                   \
 113           _eip += 2;                                                    \
 114         }                                                               \
 115     }                                                                   \
 116                                                                         \
 117   asm volatile ("mov %0, (%%ebp); mov %1, 4(%%ebp)"                     \
 118                 : : "r"(_ebp), "r"(_eip));                              \
 119 }                                                                       \
 120 while (0)
 121
 122 #define INIT_SEGV                                               \
 123 do                                                              \
 124   {                                                             \
 125     nullp = new java::lang::NullPointerException ();            \
 126     struct sigaction act;                                       \
 127     act.sa_handler = catch_segv;                                \
 128     sigemptyset (&act.sa_mask);                                 \
 129     act.sa_flags = 0;                                           \
 130     __sigaction (SIGSEGV, &act, NULL);                          \
 131   }                                                             \
 132 while (0)
 133
 134 #define INIT_FPE                                                \
 135 do                                                              \
 136   {                                                             \
 137     arithexception = new java::lang::ArithmeticException        \
 138       (JvNewStringLatin1 ("/ by zero"));                        \
 139     struct sigaction act;                                       \
 140     act.sa_handler = catch_fpe;                                 \
 141     sigemptyset (&act.sa_mask);                                 \
 142     act.sa_flags = 0;                                           \
 143     __sigaction (SIGFPE, &act, NULL);                           \
 144   }                                                             \
 145 while (0)
 146
 147 #endif /* JAVA_SIGNAL_H */
 148