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  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   if ((_rip[0] & 0xf0) == 0x40)  /* REX byte present.  */               \
  51     {                                                                   \
  52       unsigned char _rex = _rip[0] & 0x0f;                              \
  53       _is_64_bit = (_rex & 0x08) != 0;                                  \
  54       _rip++;                                                           \
  55     }                                                                   \
  56                                                                         \
  57   /* Detect a signed division of Integer.MIN_VALUE or Long.MIN_VALUE.  */ \
  58   if (_rip[0] == 0xf7)                                                  \
  59     {                                                                   \
  60       bool _min_value_dividend = false;                                 \
  61       unsigned char _modrm = _rip[1];                                   \
  62                                                                         \
  63       if (((_modrm >> 3) & 7) == 7)                                     \
  64         {                                                               \
  65           if (_is_64_bit)                                               \
  66             _min_value_dividend =                                       \
  67               _gregs[REG_RAX] == (greg_t)0x8000000000000000UL;          \
  68           else                                                          \
  69             _min_value_dividend =                                       \
  70               (_gregs[REG_RAX] & 0xffffffff) == (greg_t)0x80000000UL;   \
  71         }                                                               \
  72                                                                         \
  73       if (_min_value_dividend)                                          \
  74         {                                                               \
  75           unsigned char _rm = _modrm & 7;                               \
  76           _gregs[REG_RDX] = 0; /* the remainder is zero */              \
  77           switch (_modrm >> 6)                                          \
  78             {                                                           \
  79             case 0:  /* register indirect */                            \
  80               if (_rm == 5)   /* 32-bit displacement */                 \
  81                 _rip += 4;                                              \
  82               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  83                 _rip += 1;                                              \
  84               break;                                                    \
  85             case 1:  /* register indirect + 8-bit displacement */       \
  86               _rip += 1;                                                \
  87               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  88                 _rip += 1;                                              \
  89               break;                                                    \
  90             case 2:  /* register indirect + 32-bit displacement */      \
  91               _rip += 4;                                                \
  92               if (_rm == 4)  /* A SIB byte follows the ModR/M byte */   \
  93                 _rip += 1;                                              \
  94               break;                                                    \
  95             case 3:                                                     \
  96               break;                                                    \
  97             }                                                           \
  98           _rip += 2;                                                    \
  99           _gregs[REG_RIP] = (greg_t)_rip;                               \
 100           return;                                                       \
 101         }                                                               \
 102     }                                                                   \
 103 }                                                                       \
 104 while (0)
 105
 106 extern "C"
 107 {
 108   struct kernel_sigaction
 109   {
 110     void (*k_sa_sigaction)(int,siginfo_t *,void *);
 111     unsigned long k_sa_flags;
 112     void (*k_sa_restorer) (void);
 113     sigset_t k_sa_mask;
 114   };
 115 }
 116
 117 #define MAKE_THROW_FRAME(_exception)
 118
 119 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 120 #define RESTORE2(name, syscall)                 \
 121 asm                                             \
 122   (                                             \
 123    ".text\n"                                    \
 124    ".byte 0  # Yes, this really is necessary\n" \
 125    ".align 16\n"                                \
 126    "__" #name ":\n"                             \
 127    "    movq $" #syscall ", %rax\n"             \
 128    "    syscall\n"                              \
 129    );
 130
 131 /* The return code for realtime-signals.  */
 132 RESTORE (restore_rt, __NR_rt_sigreturn)
 133 void restore_rt (void) asm ("__restore_rt")
 134   __attribute__ ((visibility ("hidden")));
 135
 136 #define INIT_SEGV                                               \
 137 do                                                              \
 138   {                                                             \
 139     struct kernel_sigaction act;                                \
 140     act.k_sa_sigaction = _Jv_catch_segv;                        \
 141     sigemptyset (&act.k_sa_mask);                               \
 142     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 143     act.k_sa_restorer = restore_rt;                             \
 144     syscall (SYS_rt_sigaction, SIGSEGV, &act, NULL, _NSIG / 8); \
 145   }                                                             \
 146 while (0)
 147
 148 #define INIT_FPE                                                \
 149 do                                                              \
 150   {                                                             \
 151     struct kernel_sigaction act;                                \
 152     act.k_sa_sigaction = _Jv_catch_fpe;                         \
 153     sigemptyset (&act.k_sa_mask);                               \
 154     act.k_sa_flags = SA_SIGINFO|0x4000000;                      \
 155     act.k_sa_restorer = restore_rt;                             \
 156     syscall (SYS_rt_sigaction, SIGFPE, &act, NULL, _NSIG / 8);  \
 157   }                                                             \
 158 while (0)
 159
 160 /* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
 161  * instead of the standard sigaction().  This is necessary because of
 162  * the shenanigans above where we increment the PC saved in the
 163  * context and then return.  This trick will only work when we are
 164  * called _directly_ by the kernel, because linuxthreads wraps signal
 165  * handlers and its wrappers do not copy the sigcontext struct back
 166  * when returning from a signal handler.  If we return from our divide
 167  * handler to a linuxthreads wrapper, we will lose the PC adjustment
 168  * we made and return to the faulting instruction again.  Using
 169  * syscall(SYS_sigaction) causes our handler to be called directly
 170  * by the kernel, bypassing any wrappers.  */
 171
 172 #endif /* JAVA_SIGNAL_H */
 173
 174 #else /* __x86_64__ */
 175
 176 /* This is for the 32-bit subsystem on x86-64.  */
 177
 178 #define sigcontext_struct sigcontext
 179 #include <java-signal-aux.h>
 180
 181 #endif /* __x86_64__ */