| // i386-signal.h - Catch runtime signals and turn them into exceptions |
| // on an i386 based Linux system. |
| |
| /* Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation |
| |
| This file is part of libgcj. |
| |
| This software is copyrighted work licensed under the terms of the |
| Libgcj License. Please consult the file "LIBGCJ_LICENSE" for |
| details. */ |
| |
| |
| #ifndef JAVA_SIGNAL_H |
| #define JAVA_SIGNAL_H 1 |
| |
| #include <signal.h> |
| #include <sys/syscall.h> |
| |
| #define HANDLE_SEGV 1 |
| #define HANDLE_FPE 1 |
| |
| #define SIGNAL_HANDLER(_name) \ |
| static void _name (int _dummy __attribute__ ((__unused__))) |
| |
| #define MAKE_THROW_FRAME(_exception) \ |
| do \ |
| { \ |
| void **_p = (void **)&_dummy; \ |
| volatile struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p; \ |
| \ |
| /* Advance the program counter so that it is after the start of the \ |
| instruction: the x86 exception handler expects \ |
| the PC to point to the instruction after a call. */ \ |
| _regs->eip += 2; \ |
| \ |
| } \ |
| while (0) |
| |
| #define HANDLE_DIVIDE_OVERFLOW \ |
| do \ |
| { \ |
| void **_p = (void **)&_dummy; \ |
| volatile struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p;\ |
| \ |
| register unsigned char *_eip = (unsigned char *)_regs->eip; \ |
| \ |
| /* According to the JVM spec, "if the dividend is the negative \ |
| * integer of the smallest magnitude 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 eip 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. \ |
| \ |
| */ \ |
| \ |
| if (_eip[0] == 0xf7) \ |
| { \ |
| unsigned char _modrm = _eip[1]; \ |
| \ |
| if (_regs->eax == 0x80000000 \ |
| && ((_modrm >> 3) & 7) == 7) /* Signed divide */ \ |
| { \ |
| _regs->edx = 0; /* the remainder is zero */ \ |
| switch (_modrm >> 6) \ |
| { \ |
| case 0: \ |
| if ((_modrm & 7) == 5) \ |
| _eip += 4; \ |
| break; \ |
| case 1: \ |
| _eip += 1; \ |
| break; \ |
| case 2: \ |
| _eip += 4; \ |
| break; \ |
| case 3: \ |
| break; \ |
| } \ |
| _eip += 2; \ |
| _regs->eip = (unsigned long)_eip; \ |
| return; \ |
| } \ |
| else \ |
| { \ |
| /* Advance the program counter so that it is after the start \ |
| of the instruction: this is because the x86 exception \ |
| handler expects the PC to point to the instruction after a \ |
| call. */ \ |
| _regs->eip += 2; \ |
| } \ |
| } \ |
| } \ |
| while (0) |
| |
| /* We use old_kernel_sigaction here because we're calling the kernel |
| directly rather than via glibc. The sigaction structure that the |
| syscall uses is a different shape from the one in userland and not |
| visible to us in a header file so we define it here. */ |
| |
| struct old_i386_kernel_sigaction { |
| void (*k_sa_handler) (int); |
| unsigned long k_sa_mask; |
| unsigned long k_sa_flags; |
| void (*sa_restorer) (void); |
| }; |
| |
| #define RESTORE(name, syscall) RESTORE2 (name, syscall) |
| # define RESTORE2(name, syscall) \ |
| asm \ |
| ( \ |
| ".text\n" \ |
| ".byte 0 # Yes, this really is necessary\n" \ |
| " .align 8\n" \ |
| "__" #name ":\n" \ |
| " popl %eax\n" \ |
| " movl $" #syscall ", %eax\n" \ |
| " int $0x80" \ |
| ); |
| |
| RESTORE (restore, __NR_sigreturn) |
| static void restore (void) asm ("__restore"); |
| |
| #define INIT_SEGV \ |
| do \ |
| { \ |
| struct old_i386_kernel_sigaction kact; \ |
| kact.k_sa_handler = catch_segv; \ |
| kact.k_sa_mask = 0; \ |
| kact.k_sa_flags = 0x4000000; \ |
| kact.sa_restorer = restore; \ |
| syscall (SYS_sigaction, SIGSEGV, &kact, NULL); \ |
| } \ |
| while (0) |
| |
| #define INIT_FPE \ |
| do \ |
| { \ |
| struct old_i386_kernel_sigaction kact; \ |
| kact.k_sa_handler = catch_fpe; \ |
| kact.k_sa_mask = 0; \ |
| kact.k_sa_flags = 0x4000000; \ |
| kact.sa_restorer = restore; \ |
| syscall (SYS_sigaction, SIGFPE, &kact, NULL); \ |
| } \ |
| 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. |
| |
| * Also, there is at the present time no unwind info in the |
| * linuxthreads library's signal handlers and so we can't unwind |
| * through them anyway. */ |
| |
| #endif /* JAVA_SIGNAL_H */ |
| |