169 lines
5.2 KiB
C
169 lines
5.2 KiB
C
// 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 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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#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 _name (int _dummy __attribute__ ((__unused__)))
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#define MAKE_THROW_FRAME(_exception) \
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do \
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{ \
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void **_p = (void **)&_dummy; \
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volatile struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p; \
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\
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/* Advance the program counter so that it is after the start of the \
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instruction: the x86 exception handler expects \
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the PC to point to the instruction after a call. */ \
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_regs->eip += 2; \
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\
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} \
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while (0)
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#define HANDLE_DIVIDE_OVERFLOW \
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do \
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{ \
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void **_p = (void **)&_dummy; \
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volatile struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;\
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\
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register unsigned char *_eip = (unsigned char *)_regs->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 the smallest magnitude and the divisor is -1, then \
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* overflow occurs and the result is equal to the dividend. Despite \
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* 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 eip 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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if (_eip[0] == 0xf7) \
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{ \
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unsigned char _modrm = _eip[1]; \
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\
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if (_regs->eax == 0x80000000 \
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&& ((_modrm >> 3) & 7) == 7) /* Signed divide */ \
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{ \
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_regs->edx = 0; /* the remainder is zero */ \
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switch (_modrm >> 6) \
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{ \
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case 0: \
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if ((_modrm & 7) == 5) \
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_eip += 4; \
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break; \
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case 1: \
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_eip += 1; \
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break; \
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case 2: \
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_eip += 4; \
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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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_regs->eip = (unsigned long)_eip; \
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return; \
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} \
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else \
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{ \
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/* Advance the program counter so that it is after the start \
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of the instruction: this is because the x86 exception \
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handler expects the PC to point to the instruction after a \
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call. */ \
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_regs->eip += 2; \
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} \
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} \
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} \
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while (0)
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/* We use old_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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struct old_i386_kernel_sigaction {
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void (*k_sa_handler) (int);
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unsigned long k_sa_mask;
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unsigned long k_sa_flags;
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void (*sa_restorer) (void);
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};
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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 8\n" \
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"__" #name ":\n" \
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" popl %eax\n" \
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" movl $" #syscall ", %eax\n" \
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" int $0x80" \
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);
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RESTORE (restore, __NR_sigreturn)
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static void restore (void) asm ("__restore");
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#define INIT_SEGV \
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do \
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{ \
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struct old_i386_kernel_sigaction kact; \
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kact.k_sa_handler = catch_segv; \
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kact.k_sa_mask = 0; \
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kact.k_sa_flags = 0x4000000; \
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kact.sa_restorer = restore; \
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syscall (SYS_sigaction, SIGSEGV, &kact, NULL); \
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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 old_i386_kernel_sigaction kact; \
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kact.k_sa_handler = catch_fpe; \
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kact.k_sa_mask = 0; \
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kact.k_sa_flags = 0x4000000; \
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kact.sa_restorer = restore; \
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syscall (SYS_sigaction, SIGFPE, &kact, NULL); \
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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 is at the present time no unwind info in the
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* linuxthreads library's signal handlers and so we can't unwind
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* through them anyway. */
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#endif /* JAVA_SIGNAL_H */
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