libjava/include/x86_64-signal.h

   1 // x86_64-signal.h - Catch runtime signals and turn them into exceptions
   2 // on an x86_64 based GNU/Linux system.
   3
   4 /* Copyright (C) 2003, 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 #ifdef __x86_64__
  14
  15 #ifndef JAVA_SIGNAL_H
  16 #define JAVA_SIGNAL_H 1
  17
  18 #include <signal.h>
  19 #include <sys/syscall.h>
  20
  21 #define HANDLE_SEGV 1
  22 #define HANDLE_FPE 1
  23
  24 #define SIGNAL_HANDLER(_name)                                   \
  25 static void _Jv_##_name (int, siginfo_t *,                      \
  26                          void *_p __attribute__ ((__unused__)))
  27
  28 #define HANDLE_DIVIDE_OVERFLOW                                          \
  29 do                                                                      \
  30 {                                                                       \
  31   struct ucontext *_uc = (struct ucontext *)_p;                         \
  32   volatile struct sigcontext *_sc = (struct sigcontext *) &_uc->uc_mcontext; \
  33                                                                         \
  34   register unsigned char *_rip = (unsigned char *)_sc->rip;             \
  35                                                                         \
  36   /* According to the JVM spec, "if the dividend is the negative        \
  37    * integer of largest possible magnitude for the type and the         \
  38    * divisor is -1, then overflow occurs and the result is equal to     \
  39    * the dividend.  Despite the overflow, no exception occurs".         \
  40                                                                         \
  41    * We handle this by inspecting the instruction which generated the   \
  42    * signal and advancing ip to point to the following instruction.     \
  43    * As the instructions are variable length it is necessary to do a    \
  44    * little calculation to figure out where the following instruction   \
  45    * actually is.                                                       \
  46                                                                         \
  47    */                                                                   \
  48                                                                         \
  49   bool _is_64_bit = false;                                              \
  50                                                                         \
  51   if ((_rip[0] & 0xf0) == 0x40)  /* REX byte present.  */               \
  52     {                                                                   \
  53       unsigned char _rex = _rip[0] & 0x0f;                              \
  54       _is_64_bit = (_rex & 0x08) != 0;                                  \
  55       _rip++;                                                           \
  56     }                                                                   \
  57                                                                         \
  58   /* Detect a signed division of Integer.MIN_VALUE or Long.MIN_VALUE.  */ \
  59   if (_rip[0] == 0xf7)                                                  \
  60     {                                                                   \
  61       bool _min_value_dividend = false;                                 \
  62       unsigned char _modrm = _rip[1];                                   \
  63                                                                         \
  64       if (((_modrm >> 3) & 7) == 7)                                     \
  65         {                                                               \
  66           if (_is_64_bit)                                               \
  67             _min_value_dividend = (_sc->rax == 0x8000000000000000L);    \
  68           else                                                          \
  69             _min_value_dividend = ((_sc->rax & 0xffffffff) == 0x80000000); \
  70         }                                                               \
  71                                                                         \
  72       if (_min_value_dividend)                                          \
  73         {                                                               \
  74           unsigned char _rm = _modrm & 7;                               \
  75           _sc->rdx = 0; /* the remainder is zero */                     \
  76           switch (_modrm >> 6)                                          \
  77             {                                                           \
  78             case 0:  /* register indirect */                            \
  79               if (_rm == 5)   /* 32-bit displacement */                 \
  80                 _rip += 4;                                              \
  81               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  82                 _rip += 1;                                              \
  83               break;                                                    \
  84             case 1:  /* register indirect + 8-bit displacement */       \
  85               _rip += 1;                                                \
  86               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  87                 _rip += 1;                                              \
  88               break;                                                    \
  89             case 2:  /* register indirect + 32-bit displacement */      \
  90               _rip += 4;                                                \
  91               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  92                 _rip += 1;                                              \
  93               break;                                                    \
  94             case 3:                                                     \
  95               break;                                                    \
  96             }                                                           \
  97           _rip += 2;                                                    \
  98           _sc->rip = (unsigned long)_rip;                               \
  99           return;                                                       \
 100         }                                                               \
 101     }                                                                   \
 102 }                                                                       \
 103 while (0)
 104
 105 extern "C"
 106 {
 107   struct kernel_sigaction
 108   {
 109     void (*k_sa_sigaction)(int,siginfo_t *,void *);
 110     unsigned long k_sa_flags;
 111     void (*k_sa_restorer) (void);
 112     sigset_t k_sa_mask;
 113   };
 114 }
 115
 116 #define MAKE_THROW_FRAME(_exception)
 117
 118 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 119 #define RESTORE2(name, syscall)                 \
 120 asm                                             \
 121   (                                             \
 122    ".text\n"                                    \
 123    ".byte 0  # Yes, this really is necessary\n" \
 124    ".align 16\n"                                \
 125    "__" #name ":\n"                             \
 126    "    movq $" #syscall ", %rax\n"             \
 127    "    syscall\n"                              \
 128    );
 129
 130 /* The return code for realtime-signals.  */
 131 RESTORE (restore_rt, __NR_rt_sigreturn)
 132 void restore_rt (void) asm ("__restore_rt")
 133   __attribute__ ((visibility ("hidden")));
 134
 135 #define INIT_SEGV                                               \
 136 do                                                              \
 137   {                                                             \
 138     struct kernel_sigaction act;                                \
 139     act.k_sa_sigaction = _Jv_catch_segv;                        \
 140     sigemptyset (&act.k_sa_mask);                               \
 141     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 142     act.k_sa_restorer = restore_rt;                             \
 143     syscall (SYS_rt_sigaction, SIGSEGV, &act, NULL, _NSIG / 8); \
 144   }                                                             \
 145 while (0)
 146
 147 #define INIT_FPE                                                \
 148 do                                                              \
 149   {                                                             \
 150     struct kernel_sigaction act;                                \
 151     act.k_sa_sigaction = _Jv_catch_fpe;                         \
 152     sigemptyset (&act.k_sa_mask);                               \
 153     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 154     act.k_sa_restorer = restore_rt;                             \
 155     syscall (SYS_rt_sigaction, SIGFPE, &act, NULL, _NSIG / 8);  \
 156   }                                                             \
 157 while (0)
 158
 159 /* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
 160  * instead of the standard sigaction().  This is necessary because of
 161  * the shenanigans above where we increment the PC saved in the
 162  * context and then return.  This trick will only work when we are
 163  * called _directly_ by the kernel, because linuxthreads wraps signal
 164  * handlers and its wrappers do not copy the sigcontext struct back
 165  * when returning from a signal handler.  If we return from our divide
 166  * handler to a linuxthreads wrapper, we will lose the PC adjustment
 167  * we made and return to the faulting instruction again.  Using
 168  * syscall(SYS_sigaction) causes our handler to be called directly
 169  * by the kernel, bypassing any wrappers.  */
 170
 171 #endif /* JAVA_SIGNAL_H */
 172
 173 #else /* __x86_64__ */
 174
 175 /* This is for the 32-bit subsystem on x86-64.  */
 176
 177 #define sigcontext_struct sigcontext
 178 #include <java-signal-aux.h>
 179
 180 #endif /* __x86_64__ */