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, 2007, 2012  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   gregset_t &_gregs = _uc->uc_mcontext.gregs;                           \
  33   unsigned char *_rip = (unsigned char *)_gregs[REG_RIP];               \
  34                                                                         \
  35   /* According to the JVM spec, "if the dividend is the negative        \
  36    * integer of largest possible magnitude for the type and the         \
  37    * divisor is -1, then overflow occurs and the result is equal to     \
  38    * the dividend.  Despite the overflow, no exception occurs".         \
  39                                                                         \
  40    * We handle this by inspecting the instruction which generated the   \
  41    * signal and advancing ip 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   bool _is_64_bit = false;                                              \
  49                                                                         \
  50   /* Skip 67h address size prefix.  */                                  \
  51   if (_rip[0] == 0x67)                                                  \
  52     _rip++;                                                             \
  53                                                                         \
  54   if ((_rip[0] & 0xf0) == 0x40)  /* REX byte present.  */               \
  55     {                                                                   \
  56       unsigned char _rex = _rip[0] & 0x0f;                              \
  57       _is_64_bit = (_rex & 0x08) != 0;                                  \
  58       _rip++;                                                           \
  59     }                                                                   \
  60                                                                         \
  61   /* Detect a signed division of Integer.MIN_VALUE or Long.MIN_VALUE.  */ \
  62   if (_rip[0] == 0xf7)                                                  \
  63     {                                                                   \
  64       bool _min_value_dividend = false;                                 \
  65       unsigned char _modrm = _rip[1];                                   \
  66                                                                         \
  67       if (((_modrm >> 3) & 7) == 7)                                     \
  68         {                                                               \
  69           if (_is_64_bit)                                               \
  70             _min_value_dividend =                                       \
  71               _gregs[REG_RAX] == (greg_t)0x8000000000000000ULL;         \
  72           else                                                          \
  73             _min_value_dividend =                                       \
  74               (_gregs[REG_RAX] & 0xffffffff) == (greg_t)0x80000000ULL;  \
  75         }                                                               \
  76                                                                         \
  77       if (_min_value_dividend)                                          \
  78         {                                                               \
  79           unsigned char _rm = _modrm & 7;                               \
  80           _gregs[REG_RDX] = 0; /* the remainder is zero */              \
  81           switch (_modrm >> 6)                                          \
  82             {                                                           \
  83             case 0:  /* register indirect */                            \
  84               if (_rm == 5)   /* 32-bit displacement */                 \
  85                 _rip += 4;                                              \
  86               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  87                 _rip += 1;                                              \
  88               break;                                                    \
  89             case 1:  /* register indirect + 8-bit displacement */       \
  90               _rip += 1;                                                \
  91               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  92                 _rip += 1;                                              \
  93               break;                                                    \
  94             case 2:  /* register indirect + 32-bit displacement */      \
  95               _rip += 4;                                                \
  96               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  97                 _rip += 1;                                              \
  98               break;                                                    \
  99             case 3:                                                     \
 100               break;                                                    \
 101             }                                                           \
 102           _rip += 2;                                                    \
 103           _gregs[REG_RIP] = (greg_t)_rip;                               \
 104           return;                                                       \
 105         }                                                               \
 106     }                                                                   \
 107 }                                                                       \
 108 while (0)
 109
 110 extern "C"
 111 {
 112   struct kernel_sigaction
 113   {
 114     void (*k_sa_sigaction)(int,siginfo_t *,void *);
 115     unsigned long k_sa_flags;
 116     void (*k_sa_restorer) (void);
 117     sigset_t k_sa_mask;
 118   };
 119 }
 120
 121 #define MAKE_THROW_FRAME(_exception)
 122
 123 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 124 #define RESTORE2(name, syscall)                 \
 125 asm                                             \
 126   (                                             \
 127    ".text\n"                                    \
 128    ".byte 0  # Yes, this really is necessary\n" \
 129    ".align 16\n"                                \
 130    "__" #name ":\n"                             \
 131    "    movq $" #syscall ", %rax\n"             \
 132    "    syscall\n"                              \
 133    );
 134
 135 /* The return code for realtime-signals.  */
 136 RESTORE (restore_rt, __NR_rt_sigreturn)
 137 void restore_rt (void) asm ("__restore_rt")
 138   __attribute__ ((visibility ("hidden")));
 139
 140 #define INIT_SEGV                                               \
 141 do                                                              \
 142   {                                                             \
 143     struct kernel_sigaction act;                                \
 144     act.k_sa_sigaction = _Jv_catch_segv;                        \
 145     sigemptyset (&act.k_sa_mask);                               \
 146     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 147     act.k_sa_restorer = restore_rt;                             \
 148     syscall (SYS_rt_sigaction, SIGSEGV, &act, NULL, _NSIG / 8); \
 149   }                                                             \
 150 while (0)
 151
 152 #define INIT_FPE                                                \
 153 do                                                              \
 154   {                                                             \
 155     struct kernel_sigaction act;                                \
 156     act.k_sa_sigaction = _Jv_catch_fpe;                         \
 157     sigemptyset (&act.k_sa_mask);                               \
 158     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 159     act.k_sa_restorer = restore_rt;                             \
 160     syscall (SYS_rt_sigaction, SIGFPE, &act, NULL, _NSIG / 8);  \
 161   }                                                             \
 162 while (0)
 163
 164 /* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
 165  * instead of the standard sigaction().  This is necessary because of
 166  * the shenanigans above where we increment the PC saved in the
 167  * context and then return.  This trick will only work when we are
 168  * called _directly_ by the kernel, because linuxthreads wraps signal
 169  * handlers and its wrappers do not copy the sigcontext struct back
 170  * when returning from a signal handler.  If we return from our divide
 171  * handler to a linuxthreads wrapper, we will lose the PC adjustment
 172  * we made and return to the faulting instruction again.  Using
 173  * syscall(SYS_sigaction) causes our handler to be called directly
 174  * by the kernel, bypassing any wrappers.  */
 175
 176 #endif /* JAVA_SIGNAL_H */
 177
 178 #else /* __x86_64__ */
 179
 180 /* This is for the 32-bit subsystem on x86-64.  */
 181
 182 #define sigcontext_struct sigcontext
 183 #include <java-signal-aux.h>
 184
 185 #endif /* __x86_64__ */