libjava/include/i386-signal.h

   1 // i386-signal.h - Catch runtime signals and turn them into exceptions
   2 // on an i386 based Linux system.
   3
   4 /* Copyright (C) 1998, 1999, 2001, 2002, 2006  Free Software Foundation
   5
   6    This file is part of libgcj.
   7
   8 This software is copyrighted work licensed under the terms of the
   9 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
  10 details.  */
  11
  12
  13 #ifndef JAVA_SIGNAL_H
  14 #define JAVA_SIGNAL_H 1
  15
  16 #include <signal.h>
  17 #include <sys/syscall.h>
  18
  19 #define HANDLE_SEGV 1
  20 #define HANDLE_FPE 1
  21
  22 #define SIGNAL_HANDLER(_name)   \
  23 static void _name (int _dummy __attribute__ ((__unused__)))
  24
  25 #define MAKE_THROW_FRAME(_exception)
  26
  27 #define HANDLE_DIVIDE_OVERFLOW                                          \
  28 do                                                                      \
  29 {                                                                       \
  30   void **_p = (void **)&_dummy;                                         \
  31   volatile struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;\
  32                                                                         \
  33   register unsigned char *_eip = (unsigned char *)_regs->eip;           \
  34                                                                         \
  35   /* According to the JVM spec, "if the dividend is the negative        \
  36    * integer of the smallest magnitude and the divisor is -1, then      \
  37    * overflow occurs and the result is equal to the dividend.  Despite  \
  38    * the overflow, no exception occurs".                                \
  39                                                                         \
  40    * We handle this by inspecting the instruction which generated the   \
  41    * signal and advancing eip to point to the following instruction.    \
  42    * As the instructions are variable length it is necessary to do a    \
  43    * little calculation to figure out where the following instruction   \
  44    * actually is.                                                       \
  45                                                                         \
  46    */                                                                   \
  47                                                                         \
  48   if (_eip[0] == 0xf7)                                                  \
  49     {                                                                   \
  50       unsigned char _modrm = _eip[1];                                   \
  51                                                                         \
  52       if (_regs->eax == 0x80000000                                      \
  53           && ((_modrm >> 3) & 7) == 7) /* Signed divide */              \
  54         {                                                               \
  55           unsigned char _rm = _modrm & 7;                               \
  56           _regs->edx = 0; /* the remainder is zero */                   \
  57           switch (_modrm >> 6)                                          \
  58             {                                                           \
  59             case 0:  /* register indirect */                            \
  60               if (_rm == 5)   /* 32-bit displacement */                 \
  61                 _eip += 4;                                              \
  62               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  63                 _eip += 1;                                              \
  64               break;                                                    \
  65             case 1:  /* register indirect + 8-bit displacement */       \
  66               _eip += 1;                                                \
  67               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  68                 _eip += 1;                                              \
  69               break;                                                    \
  70             case 2:  /* register indirect + 32-bit displacement */      \
  71               _eip += 4;                                                \
  72               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  73                 _eip += 1;                                              \
  74               break;                                                    \
  75             case 3:                                                     \
  76               break;                                                    \
  77             }                                                           \
  78           _eip += 2;                                                    \
  79           _regs->eip = (unsigned long)_eip;                             \
  80           return;                                                       \
  81         }                                                               \
  82     }                                                                   \
  83 }                                                                       \
  84 while (0)
  85
  86 /* We use old_kernel_sigaction here because we're calling the kernel
  87    directly rather than via glibc.  The sigaction structure that the
  88    syscall uses is a different shape from the one in userland and not
  89    visible to us in a header file so we define it here.  */
  90
  91 struct old_i386_kernel_sigaction {
  92         void (*k_sa_handler) (int);
  93         unsigned long k_sa_mask;
  94         unsigned long k_sa_flags;
  95         void (*sa_restorer) (void);
  96 };
  97
  98 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
  99 # define RESTORE2(name, syscall) \
 100 asm                                             \
 101   (                                             \
 102    ".text\n"                                    \
 103    ".byte 0  # Yes, this really is necessary\n" \
 104    "    .align 8\n"                             \
 105    "__" #name ":\n"                             \
 106    "    popl %eax\n"                            \
 107    "    movl $" #syscall ", %eax\n"             \
 108    "    int  $0x80"                             \
 109    );
 110
 111 RESTORE (restore, __NR_sigreturn)
 112 static void restore (void) asm ("__restore");
 113
 114 #define INIT_SEGV                                       \
 115 do                                                      \
 116   {                                                     \
 117     struct old_i386_kernel_sigaction kact;              \
 118     kact.k_sa_handler = catch_segv;                     \
 119     kact.k_sa_mask = 0;                                 \
 120     kact.k_sa_flags = 0x4000000;                        \
 121     kact.sa_restorer = restore;                         \
 122     syscall (SYS_sigaction, SIGSEGV, &kact, NULL);      \
 123   }                                                     \
 124 while (0)
 125
 126 #define INIT_FPE                                        \
 127 do                                                      \
 128   {                                                     \
 129     struct old_i386_kernel_sigaction kact;              \
 130     kact.k_sa_handler = catch_fpe;                      \
 131     kact.k_sa_mask = 0;                                 \
 132     kact.k_sa_flags = 0x4000000;                        \
 133     kact.sa_restorer = restore;                         \
 134     syscall (SYS_sigaction, SIGFPE, &kact, NULL);       \
 135   }                                                     \
 136 while (0)
 137
 138 /* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
 139  * instead of the standard sigaction().  This is necessary because of
 140  * the shenanigans above where we increment the PC saved in the
 141  * context and then return.  This trick will only work when we are
 142  * called _directly_ by the kernel, because linuxthreads wraps signal
 143  * handlers and its wrappers do not copy the sigcontext struct back
 144  * when returning from a signal handler.  If we return from our divide
 145  * handler to a linuxthreads wrapper, we will lose the PC adjustment
 146  * we made and return to the faulting instruction again.  Using
 147  * syscall(SYS_sigaction) causes our handler to be called directly
 148  * by the kernel, bypassing any wrappers.
 149
 150  * Also, there is at the present time no unwind info in the
 151  * linuxthreads library's signal handlers and so we can't unwind
 152  * through them anyway.  */
 153
 154 #endif /* JAVA_SIGNAL_H */
 155