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jeremybenn |
// i386-signal.h - Catch runtime signals and turn them into exceptions
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// on an i386 based Linux system.
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/* Copyright (C) 1998, 1999, 2001, 2002, 2006, 2007, 2011
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Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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#ifdef __i386__
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#ifndef JAVA_SIGNAL_H
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#define JAVA_SIGNAL_H 1
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#include <signal.h>
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#include <sys/syscall.h>
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#define HANDLE_SEGV 1
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#define HANDLE_FPE 1
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#define SIGNAL_HANDLER(_name) \
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static void _Jv_##_name (int, siginfo_t *, \
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void *_p __attribute__ ((__unused__)))
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#define HANDLE_DIVIDE_OVERFLOW \
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do \
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{ \
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struct ucontext *_uc = (struct ucontext *)_p; \
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gregset_t &_gregs = _uc->uc_mcontext.gregs; \
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unsigned char *_eip = (unsigned char *)_gregs[REG_EIP]; \
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\
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/* According to the JVM spec, "if the dividend is the negative \
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* integer of largest possible magnitude for the type and the \
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* divisor is -1, then overflow occurs and the result is equal to \
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* the dividend. Despite the overflow, no exception occurs". \
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\
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* We handle this by inspecting the instruction which generated the \
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* signal and advancing ip to point to the following instruction. \
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* As the instructions are variable length it is necessary to do a \
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* little calculation to figure out where the following instruction \
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* actually is. \
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\
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*/ \
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\
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/* Detect a signed division of Integer.MIN_VALUE. */ \
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if (_eip[0] == 0xf7) \
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{ \
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bool _min_value_dividend = false; \
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unsigned char _modrm = _eip[1]; \
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\
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if (((_modrm >> 3) & 7) == 7) /* Signed divide */ \
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{ \
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_min_value_dividend = \
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_gregs[REG_EAX] == (greg_t)0x80000000UL; \
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} \
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\
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if (_min_value_dividend) \
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{ \
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unsigned char _rm = _modrm & 7; \
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_gregs[REG_EDX] = 0; /* the remainder is zero */ \
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switch (_modrm >> 6) \
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{ \
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case 0: /* register indirect */ \
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if (_rm == 5) /* 32-bit displacement */ \
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_eip += 4; \
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if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
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_eip += 1; \
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break; \
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case 1: /* register indirect + 8-bit displacement */ \
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_eip += 1; \
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if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
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_eip += 1; \
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break; \
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case 2: /* register indirect + 32-bit displacement */ \
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_eip += 4; \
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if (_rm == 4) /* A SIB byte follows the ModR/M byte */ \
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_eip += 1; \
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break; \
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case 3: \
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break; \
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} \
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_eip += 2; \
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_gregs[REG_EIP] = (greg_t)_eip; \
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return; \
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} \
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} \
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} \
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while (0)
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/* We use kernel_sigaction here because we're calling the kernel
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directly rather than via glibc. The sigaction structure that the
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syscall uses is a different shape from the one in userland and not
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visible to us in a header file so we define it here. */
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extern "C"
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{
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struct kernel_sigaction
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{
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void (*k_sa_sigaction)(int,siginfo_t *,void *);
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unsigned long k_sa_flags;
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void (*k_sa_restorer) (void);
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sigset_t k_sa_mask;
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};
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}
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#define MAKE_THROW_FRAME(_exception)
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#define RESTORE(name, syscall) RESTORE2 (name, syscall)
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#define RESTORE2(name, syscall) \
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asm \
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( \
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".text\n" \
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".byte 0 # Yes, this really is necessary\n" \
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" .align 16\n" \
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"__" #name ":\n" \
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" movl $" #syscall ", %eax\n" \
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" int $0x80" \
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);
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/* The return code for realtime-signals. */
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RESTORE (restore_rt, __NR_rt_sigreturn)
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void restore_rt (void) asm ("__restore_rt")
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__attribute__ ((visibility ("hidden")));
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#define INIT_SEGV \
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do \
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{ \
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struct kernel_sigaction act; \
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act.k_sa_sigaction = _Jv_catch_segv; \
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sigemptyset (&act.k_sa_mask); \
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act.k_sa_flags = SA_SIGINFO|0x4000000; \
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act.k_sa_restorer = restore_rt; \
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syscall (SYS_rt_sigaction, SIGSEGV, &act, NULL, _NSIG / 8); \
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} \
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while (0)
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#define INIT_FPE \
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do \
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{ \
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struct kernel_sigaction act; \
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act.k_sa_sigaction = _Jv_catch_fpe; \
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sigemptyset (&act.k_sa_mask); \
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act.k_sa_flags = SA_SIGINFO|0x4000000; \
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act.k_sa_restorer = restore_rt; \
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syscall (SYS_rt_sigaction, SIGFPE, &act, NULL, _NSIG / 8); \
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} \
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while (0)
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/* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
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* instead of the standard sigaction(). This is necessary because of
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* the shenanigans above where we increment the PC saved in the
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* context and then return. This trick will only work when we are
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* called _directly_ by the kernel, because linuxthreads wraps signal
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* handlers and its wrappers do not copy the sigcontext struct back
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* when returning from a signal handler. If we return from our divide
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* handler to a linuxthreads wrapper, we will lose the PC adjustment
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* we made and return to the faulting instruction again. Using
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* syscall(SYS_sigaction) causes our handler to be called directly
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* by the kernel, bypassing any wrappers.
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* Also, there may not be any unwind info in the linuxthreads
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* library's signal handlers and so we can't unwind through them
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* anyway. */
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#endif /* JAVA_SIGNAL_H */
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#else /* __i386__ */
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/* This is for the 64-bit subsystem on i386. */
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#define sigcontext_struct sigcontext
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#include <java-signal-aux.h>
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#endif /* __i386__ */
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