// x86_64-signal.h - Catch runtime signals and turn them into exceptions
// on an x86_64 based GNU/Linux system.
-/* Copyright (C) 2003 Free Software Foundation
+/* Copyright (C) 2003, 2006, 2007 Free Software Foundation
This file is part of libgcj.
#include <sys/syscall.h>
#define HANDLE_SEGV 1
-
-#define SIGNAL_HANDLER(_name) \
-static void _Jv_##_name (int, siginfo_t *, void *_p)
+#define HANDLE_FPE 1
+
+#define SIGNAL_HANDLER(_name) \
+static void _Jv_##_name (int, siginfo_t *, \
+ void *_p __attribute__ ((__unused__)))
+
+#define HANDLE_DIVIDE_OVERFLOW \
+do \
+{ \
+ struct ucontext *_uc = (struct ucontext *)_p; \
+ gregset_t &_gregs = _uc->uc_mcontext.gregs; \
+ unsigned char *_rip = (unsigned char *)_gregs[REG_RIP]; \
+ \
+ /* According to the JVM spec, "if the dividend is the negative \
+ * integer of largest possible magnitude for the type and the \
+ * divisor is -1, then overflow occurs and the result is equal to \
+ * the dividend. Despite the overflow, no exception occurs". \
+ \
+ * We handle this by inspecting the instruction which generated the \
+ * signal and advancing ip to point to the following instruction. \
+ * As the instructions are variable length it is necessary to do a \
+ * little calculation to figure out where the following instruction \
+ * actually is. \
+ \
+ */ \
+ \
+ bool _is_64_bit = false; \
+ \
+ if ((_rip[0] & 0xf0) == 0x40) /* REX byte present. */ \
+ { \
+ unsigned char _rex = _rip[0] & 0x0f; \
+ _is_64_bit = (_rex & 0x08) != 0; \
+ _rip++; \
+ } \
+ \
+ /* Detect a signed division of Integer.MIN_VALUE or Long.MIN_VALUE. */ \
+ if (_rip[0] == 0xf7) \
+ { \
+ bool _min_value_dividend = false; \
+ unsigned char _modrm = _rip[1]; \
+ \
+ if (((_modrm >> 3) & 7) == 7) \
+ { \
+ if (_is_64_bit) \
+ _min_value_dividend = \
+ _gregs[REG_RAX] == (greg_t)0x8000000000000000UL; \
+ else \
+ _min_value_dividend = \
+ (_gregs[REG_RAX] & 0xffffffff) == (greg_t)0x80000000UL; \
+ } \
+ \
+ if (_min_value_dividend) \
+ { \
+ unsigned char _rm = _modrm & 7; \
+ _gregs[REG_RDX] = 0; /* the remainder is zero */ \
+ switch (_modrm >> 6) \
+ { \
+ case 0: /* register indirect */ \
+ if (_rm == 5) /* 32-bit displacement */ \
+ _rip += 4; \
+ if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
+ _rip += 1; \
+ break; \
+ case 1: /* register indirect + 8-bit displacement */ \
+ _rip += 1; \
+ if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
+ _rip += 1; \
+ break; \
+ case 2: /* register indirect + 32-bit displacement */ \
+ _rip += 4; \
+ if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
+ _rip += 1; \
+ break; \
+ case 3: \
+ break; \
+ } \
+ _rip += 2; \
+ _gregs[REG_RIP] = (greg_t)_rip; \
+ return; \
+ } \
+ } \
+} \
+while (0)
extern "C"
{
};
}
-#define MAKE_THROW_FRAME(_exception) \
-do \
-{ \
- /* Advance the program counter so that it is after the start of the \
- instruction: the x86_64 exception handler expects \
- the PC to point to the instruction after a call. */ \
- struct ucontext *_uc = (struct ucontext *)_p; \
- volatile struct sigcontext *_sc = (struct sigcontext *) &_uc->uc_mcontext; \
- _sc->rip += 2; \
-} \
-while (0)
+#define MAKE_THROW_FRAME(_exception)
#define RESTORE(name, syscall) RESTORE2 (name, syscall)
#define RESTORE2(name, syscall) \
asm \
( \
+ ".text\n" \
".byte 0 # Yes, this really is necessary\n" \
".align 16\n" \
"__" #name ":\n" \
/* The return code for realtime-signals. */
RESTORE (restore_rt, __NR_rt_sigreturn)
-static void restore_rt (void) asm ("__restore_rt");
+void restore_rt (void) asm ("__restore_rt")
+ __attribute__ ((visibility ("hidden")));
#define INIT_SEGV \
do \
} \
while (0)
-/* We use syscall(SYS_rt_sigaction) in INIT_SEGV instead of
- * sigaction() because on some systems the pthreads wrappers for
- * signal handlers are not compiled with unwind information, so it's
- * not possible to unwind through them. This is a problem that will
- * go away if all systems ever have pthreads libraries that are
- * compiled with unwind info. */
+#define INIT_FPE \
+do \
+ { \
+ struct kernel_sigaction act; \
+ act.k_sa_sigaction = _Jv_catch_fpe; \
+ sigemptyset (&act.k_sa_mask); \
+ act.k_sa_flags = SA_SIGINFO|0x4000000; \
+ act.k_sa_restorer = restore_rt; \
+ syscall (SYS_rt_sigaction, SIGFPE, &act, NULL, _NSIG / 8); \
+ } \
+while (0)
+
+/* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
+ * instead of the standard sigaction(). This is necessary because of
+ * the shenanigans above where we increment the PC saved in the
+ * context and then return. This trick will only work when we are
+ * called _directly_ by the kernel, because linuxthreads wraps signal
+ * handlers and its wrappers do not copy the sigcontext struct back
+ * when returning from a signal handler. If we return from our divide
+ * handler to a linuxthreads wrapper, we will lose the PC adjustment
+ * we made and return to the faulting instruction again. Using
+ * syscall(SYS_sigaction) causes our handler to be called directly
+ * by the kernel, bypassing any wrappers. */
#endif /* JAVA_SIGNAL_H */
#else /* __x86_64__ */
-/* This is for the 32-bit subsystem on on x86-64. */
+/* This is for the 32-bit subsystem on x86-64. */
#define sigcontext_struct sigcontext
#include <java-signal-aux.h>
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