/*
       *  linux/arch/i386/traps.c
       *
       *  Copyright (C) 1991, 1992  Linus Torvalds
       *
       *  Pentium III FXSR, SSE support
       *	Gareth Hughes <gareth@valinux.com>, May 2000
       */
      
      /*
       * 'Traps.c' handles hardware traps and faults after we have saved some
       * state in 'asm.s'.
       */
      #include <linux/config.h>
      #include <linux/sched.h>
      #include <linux/kernel.h>
      #include <linux/string.h>
      #include <linux/errno.h>
      #include <linux/ptrace.h>
      #include <linux/timer.h>
      #include <linux/mm.h>
      #include <linux/init.h>
      #include <linux/delay.h>
      #include <linux/spinlock.h>
      #include <linux/interrupt.h>
      
      #ifdef CONFIG_MCA
      #include <linux/mca.h>
      #include <asm/processor.h>
      #endif
      
      #include <asm/system.h>
      #include <asm/uaccess.h>
      #include <asm/io.h>
      #include <asm/atomic.h>
      #include <asm/debugreg.h>
      #include <asm/desc.h>
      #include <asm/i387.h>
      
      #include <asm/smp.h>
      #include <asm/pgalloc.h>
      
      #ifdef CONFIG_X86_VISWS_APIC
      #include <asm/fixmap.h>
      #include <asm/cobalt.h>
      #include <asm/lithium.h>
      #endif
      
      #include <linux/irq.h>
      
      asmlinkage int system_call(void);
      asmlinkage void lcall7(void);
      asmlinkage void lcall27(void);
      
      struct desc_struct default_ldt[] = { { 0, 0 }, { 0, 0 }, { 0, 0 },
      		{ 0, 0 }, { 0, 0 } };
      
      /*
       * The IDT has to be page-aligned to simplify the Pentium
       * F0 0F bug workaround.. We have a special link segment
       * for this.
       */
      struct desc_struct idt_table[256] __attribute__((__section__(".data.idt"))) = { {0, 0}, };
      
      extern void bust_spinlocks(void);
      
      asmlinkage void divide_error(void);
      asmlinkage void debug(void);
      asmlinkage void nmi(void);
      asmlinkage void int3(void);
      asmlinkage void overflow(void);
      asmlinkage void bounds(void);
      asmlinkage void invalid_op(void);
      asmlinkage void device_not_available(void);
      asmlinkage void double_fault(void);
      asmlinkage void coprocessor_segment_overrun(void);
      asmlinkage void invalid_TSS(void);
      asmlinkage void segment_not_present(void);
      asmlinkage void stack_segment(void);
      asmlinkage void general_protection(void);
      asmlinkage void page_fault(void);
      asmlinkage void coprocessor_error(void);
      asmlinkage void simd_coprocessor_error(void);
      asmlinkage void alignment_check(void);
      asmlinkage void spurious_interrupt_bug(void);
      asmlinkage void machine_check(void);
      
      int kstack_depth_to_print = 24;
      
      /*
       * These constants are for searching for possible module text
       * segments.
       */
      
  95  void show_trace(unsigned long * stack)
      {
      	int i;
      	unsigned long addr, module_start, module_end;
      
 100  	if (!stack)
      		stack = (unsigned long*)&stack;
      
      	printk("Call Trace: ");
      	i = 1;
      	module_start = VMALLOC_START;
      	module_end = VMALLOC_END;
 107  	while (((long) stack & (THREAD_SIZE-1)) != 0) {
      		addr = *stack++;
      		/*
      		 * If the address is either in the text segment of the
      		 * kernel, or in the region which contains vmalloc'ed
      		 * memory, it *may* be the address of a calling
      		 * routine; if so, print it so that someone tracing
      		 * down the cause of the crash will be able to figure
      		 * out the call path that was taken.
      		 */
      		if (((addr >= (unsigned long) &_stext) &&
      		     (addr <= (unsigned long) &_etext)) ||
 119  		    ((addr >= module_start) && (addr <= module_end))) {
 120  			if (i && ((i % 8) == 0))
      				printk("\n       ");
      			printk("[<%08lx>] ", addr);
      			i++;
      		}
      	}
      	printk("\n");
      }
      
 129  void show_stack(unsigned long * esp)
      {
      	unsigned long *stack;
      	int i;
      
      	// debugging aid: "show_stack(NULL);" prints the
      	// back trace for this cpu.
      
 137  	if(esp==NULL)
      		esp=(unsigned long*)&esp;
      
      	stack = esp;
 141  	for(i=0; i < kstack_depth_to_print; i++) {
 142  		if (((long) stack & (THREAD_SIZE-1)) == 0)
 143  			break;
 144  		if (i && ((i % 8) == 0))
      			printk("\n       ");
      		printk("%08lx ", *stack++);
      	}
      	printk("\n");
      	show_trace(esp);
      }
      
 152  static void show_registers(struct pt_regs *regs)
      {
      	int i;
      	int in_kernel = 1;
      	unsigned long esp;
      	unsigned short ss;
      
      	esp = (unsigned long) (®s->esp);
      	ss = __KERNEL_DS;
 161  	if (regs->xcs & 3) {
      		in_kernel = 0;
      		esp = regs->esp;
      		ss = regs->xss & 0xffff;
      	}
      	printk("CPU:    %d\nEIP:    %04x:[<%08lx>]\nEFLAGS: %08lx\n",
      		smp_processor_id(), 0xffff & regs->xcs, regs->eip, regs->eflags);
      	printk("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
      		regs->eax, regs->ebx, regs->ecx, regs->edx);
      	printk("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
      		regs->esi, regs->edi, regs->ebp, esp);
      	printk("ds: %04x   es: %04x   ss: %04x\n",
      		regs->xds & 0xffff, regs->xes & 0xffff, ss);
      	printk("Process %s (pid: %d, stackpage=%08lx)",
      		current->comm, current->pid, 4096+(unsigned long)current);
      	/*
      	 * When in-kernel, we also print out the stack and code at the
      	 * time of the fault..
      	 */
 180  	if (in_kernel) {
      
      		printk("\nStack: ");
      		show_stack((unsigned long*)esp);
      
      		printk("\nCode: ");
 186  		if(regs->eip < PAGE_OFFSET)
 187  			goto bad;
      
 189  		for(i=0;i<20;i++)
      		{
      			unsigned char c;
 192  			if(__get_user(c, &((unsigned char*)regs->eip)[i])) {
      bad:
      				printk(" Bad EIP value.");
 195  				break;
      			}
      			printk("%02x ", c);
      		}
      	}
      	printk("\n");
      }	
      
      spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
      
 205  void die(const char * str, struct pt_regs * regs, long err)
      {
      	console_verbose();
 208  	spin_lock_irq(&die_lock);
      	printk("%s: %04lx\n", str, err & 0xffff);
      	show_registers(regs);
      
 212  	spin_unlock_irq(&die_lock);
      	do_exit(SIGSEGV);
      }
      
 216  static inline void die_if_kernel(const char * str, struct pt_regs * regs, long err)
      {
 218  	if (!(regs->eflags & VM_MASK) && !(3 & regs->xcs))
      		die(str, regs, err);
      }
      
 222  static inline unsigned long get_cr2(void)
      {
      	unsigned long address;
      
      	/* get the address */
      	__asm__("movl %%cr2,%0":"=r" (address));
 228  	return address;
      }
      
 231  static void inline do_trap(int trapnr, int signr, char *str, int vm86,
      			   struct pt_regs * regs, long error_code, siginfo_t *info)
      {
 234  	if (vm86 && regs->eflags & VM_MASK)
 235  		goto vm86_trap;
 236  	if (!(regs->xcs & 3))
 237  		goto kernel_trap;
      
      	trap_signal: {
      		struct task_struct *tsk = current;
      		tsk->thread.error_code = error_code;
      		tsk->thread.trap_no = trapnr;
 243  		if (info)
      			force_sig_info(signr, info, tsk);
 245  		else
      			force_sig(signr, tsk);
 247  		return;
      	}
      
      	kernel_trap: {
      		unsigned long fixup = search_exception_table(regs->eip);
 252  		if (fixup)
      			regs->eip = fixup;
 254  		else	
      			die(str, regs, error_code);
 256  		return;
      	}
      
      	vm86_trap: {
      		int ret = handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, trapnr);
 261  		if (ret) goto trap_signal;
 262  		return;
      	}
      }
      
      #define DO_ERROR(trapnr, signr, str, name) \
      asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
      { \
      	do_trap(trapnr, signr, str, 0, regs, error_code, NULL); \
      }
      
      #define DO_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr) \
      asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
      { \
      	siginfo_t info; \
      	info.si_signo = signr; \
      	info.si_errno = 0; \
      	info.si_code = sicode; \
      	info.si_addr = (void *)siaddr; \
      	do_trap(trapnr, signr, str, 0, regs, error_code, &info); \
      }
      
      #define DO_VM86_ERROR(trapnr, signr, str, name) \
      asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
      { \
      	do_trap(trapnr, signr, str, 1, regs, error_code, NULL); \
      }
      
      #define DO_VM86_ERROR_INFO(trapnr, signr, str, name, sicode, siaddr) \
      asmlinkage void do_##name(struct pt_regs * regs, long error_code) \
      { \
      	siginfo_t info; \
      	info.si_signo = signr; \
      	info.si_errno = 0; \
      	info.si_code = sicode; \
      	info.si_addr = (void *)siaddr; \
      	do_trap(trapnr, signr, str, 1, regs, error_code, &info); \
      }
      
 300  DO_VM86_ERROR_INFO( 0, SIGFPE,  "divide error", divide_error, FPE_INTDIV, regs->eip)
 301  DO_VM86_ERROR( 3, SIGTRAP, "int3", int3)
 302  DO_VM86_ERROR( 4, SIGSEGV, "overflow", overflow)
 303  DO_VM86_ERROR( 5, SIGSEGV, "bounds", bounds)
 304  DO_ERROR_INFO( 6, SIGILL,  "invalid operand", invalid_op, ILL_ILLOPN, regs->eip)
 305  DO_VM86_ERROR( 7, SIGSEGV, "device not available", device_not_available)
 306  DO_ERROR( 8, SIGSEGV, "double fault", double_fault)
 307  DO_ERROR( 9, SIGFPE,  "coprocessor segment overrun", coprocessor_segment_overrun)
 308  DO_ERROR(10, SIGSEGV, "invalid TSS", invalid_TSS)
 309  DO_ERROR(11, SIGBUS,  "segment not present", segment_not_present)
 310  DO_ERROR(12, SIGBUS,  "stack segment", stack_segment)
 311  DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, get_cr2())
      
 313  asmlinkage void do_general_protection(struct pt_regs * regs, long error_code)
      {
 315  	if (regs->eflags & VM_MASK)
 316  		goto gp_in_vm86;
      
 318  	if (!(regs->xcs & 3))
 319  		goto gp_in_kernel;
      
      	current->thread.error_code = error_code;
      	current->thread.trap_no = 13;
      	force_sig(SIGSEGV, current);
 324  	return;
      
      gp_in_vm86:
      	handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
 328  	return;
      
      gp_in_kernel:
      	{
      		unsigned long fixup;
      		fixup = search_exception_table(regs->eip);
 334  		if (fixup) {
      			regs->eip = fixup;
 336  			return;
      		}
      		die("general protection fault", regs, error_code);
      	}
      }
      
 342  static void mem_parity_error(unsigned char reason, struct pt_regs * regs)
      {
      	printk("Uhhuh. NMI received. Dazed and confused, but trying to continue\n");
      	printk("You probably have a hardware problem with your RAM chips\n");
      
      	/* Clear and disable the memory parity error line. */
      	reason = (reason & 0xf) | 4;
      	outb(reason, 0x61);
      }
      
 352  static void io_check_error(unsigned char reason, struct pt_regs * regs)
      {
      	unsigned long i;
      
      	printk("NMI: IOCK error (debug interrupt?)\n");
      	show_registers(regs);
      
      	/* Re-enable the IOCK line, wait for a few seconds */
      	reason = (reason & 0xf) | 8;
      	outb(reason, 0x61);
      	i = 2000;
 363  	while (--i) udelay(1000);
      	reason &= ~8;
      	outb(reason, 0x61);
      }
      
 368  static void unknown_nmi_error(unsigned char reason, struct pt_regs * regs)
      {
      #ifdef CONFIG_MCA
      	/* Might actually be able to figure out what the guilty party
      	* is. */
      	if( MCA_bus ) {
      		mca_handle_nmi();
      		return;
      	}
      #endif
      	printk("Uhhuh. NMI received for unknown reason %02x.\n", reason);
      	printk("Dazed and confused, but trying to continue\n");
      	printk("Do you have a strange power saving mode enabled?\n");
      }
      
      #if CONFIG_X86_IO_APIC
      
      int nmi_watchdog = 1;
      
      static int __init setup_nmi_watchdog(char *str)
      {
              get_option(&str, &nmi_watchdog);
              return 1;
      }
      
      __setup("nmi_watchdog=", setup_nmi_watchdog);
      
      static spinlock_t nmi_print_lock = SPIN_LOCK_UNLOCKED;
      
      inline void nmi_watchdog_tick(struct pt_regs * regs)
      {
      	/*
      	 * the best way to detect wether a CPU has a 'hard lockup' problem
      	 * is to check it's local APIC timer IRQ counts. If they are not
      	 * changing then that CPU has some problem.
      	 *
      	 * as these watchdog NMI IRQs are broadcasted to every CPU, here
      	 * we only have to check the current processor.
      	 *
      	 * since NMIs dont listen to _any_ locks, we have to be extremely
      	 * careful not to rely on unsafe variables. The printk might lock
      	 * up though, so we have to break up console_lock first ...
      	 * [when there will be more tty-related locks, break them up
      	 *  here too!]
      	 */
      
      	static unsigned int last_irq_sums [NR_CPUS],
      				alert_counter [NR_CPUS];
      
      	/*
      	 * Since current-> is always on the stack, and we always switch
      	 * the stack NMI-atomically, it's safe to use smp_processor_id().
      	 */
      	int sum, cpu = smp_processor_id();
      
      	sum = apic_timer_irqs[cpu];
      
      	if (last_irq_sums[cpu] == sum) {
      		/*
      		 * Ayiee, looks like this CPU is stuck ...
      		 * wait a few IRQs (5 seconds) before doing the oops ...
      		 */
      		alert_counter[cpu]++;
      		if (alert_counter[cpu] == 5*HZ) {
      			spin_lock(&nmi_print_lock);
      			/*
      			 * We are in trouble anyway, lets at least try
      			 * to get a message out.
      			 */
      			bust_spinlocks();
      			printk("NMI Watchdog detected LOCKUP on CPU%d, registers:\n", cpu);
      			show_registers(regs);
      			printk("console shuts up ...\n");
      			console_silent();
      			spin_unlock(&nmi_print_lock);
      			do_exit(SIGSEGV);
      		}
      	} else {
      		last_irq_sums[cpu] = sum;
      		alert_counter[cpu] = 0;
      	}
      }
      #endif
      
 452  asmlinkage void do_nmi(struct pt_regs * regs, long error_code)
      {
      	unsigned char reason = inb(0x61);
      
      
      	++nmi_count(smp_processor_id());
 458  	if (!(reason & 0xc0)) {
      #if CONFIG_X86_IO_APIC
      		/*
      		 * Ok, so this is none of the documented NMI sources,
      		 * so it must be the NMI watchdog.
      		 */
      		if (nmi_watchdog) {
      			nmi_watchdog_tick(regs);
      			return;
      		} else
      			unknown_nmi_error(reason, regs);
      #else
      		unknown_nmi_error(reason, regs);
      #endif
 472  		return;
      	}
 474  	if (reason & 0x80)
      		mem_parity_error(reason, regs);
 476  	if (reason & 0x40)
      		io_check_error(reason, regs);
      	/*
      	 * Reassert NMI in case it became active meanwhile
      	 * as it's edge-triggered.
      	 */
      	outb(0x8f, 0x70);
      	inb(0x71);		/* dummy */
      	outb(0x0f, 0x70);
      	inb(0x71);		/* dummy */
      }
      
      /*
       * Our handling of the processor debug registers is non-trivial.
       * We do not clear them on entry and exit from the kernel. Therefore
       * it is possible to get a watchpoint trap here from inside the kernel.
       * However, the code in ./ptrace.c has ensured that the user can
       * only set watchpoints on userspace addresses. Therefore the in-kernel
       * watchpoint trap can only occur in code which is reading/writing
       * from user space. Such code must not hold kernel locks (since it
       * can equally take a page fault), therefore it is safe to call
       * force_sig_info even though that claims and releases locks.
       * 
       * Code in ./signal.c ensures that the debug control register
       * is restored before we deliver any signal, and therefore that
       * user code runs with the correct debug control register even though
       * we clear it here.
       *
       * Being careful here means that we don't have to be as careful in a
       * lot of more complicated places (task switching can be a bit lazy
       * about restoring all the debug state, and ptrace doesn't have to
       * find every occurrence of the TF bit that could be saved away even
       * by user code)
       */
 510  asmlinkage void do_debug(struct pt_regs * regs, long error_code)
      {
      	unsigned int condition;
      	struct task_struct *tsk = current;
      	siginfo_t info;
      
      	__asm__ __volatile__("movl %%db6,%0" : "=r" (condition));
      
      	/* Mask out spurious debug traps due to lazy DR7 setting */
 519  	if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
 520  		if (!tsk->thread.debugreg[7])
 521  			goto clear_dr7;
      	}
      
 524  	if (regs->eflags & VM_MASK)
 525  		goto debug_vm86;
      
      	/* Save debug status register where ptrace can see it */
      	tsk->thread.debugreg[6] = condition;
      
      	/* Mask out spurious TF errors due to lazy TF clearing */
 531  	if (condition & DR_STEP) {
      		/*
      		 * The TF error should be masked out only if the current
      		 * process is not traced and if the TRAP flag has been set
      		 * previously by a tracing process (condition detected by
      		 * the PT_DTRACE flag); remember that the i386 TRAP flag
      		 * can be modified by the process itself in user mode,
      		 * allowing programs to debug themselves without the ptrace()
      		 * interface.
      		 */
 541  		if ((tsk->ptrace & (PT_DTRACE|PT_PTRACED)) == PT_DTRACE)
 542  			goto clear_TF;
      	}
      
      	/* Ok, finally something we can handle */
      	tsk->thread.trap_no = 1;
      	tsk->thread.error_code = error_code;
      	info.si_signo = SIGTRAP;
      	info.si_errno = 0;
      	info.si_code = TRAP_BRKPT;
      	
      	/* If this is a kernel mode trap, save the user PC on entry to 
      	 * the kernel, that's what the debugger can make sense of.
      	 */
      	info.si_addr = ((regs->xcs & 3) == 0) ? (void *)tsk->thread.eip : 
      	                                        (void *)regs->eip;
      	force_sig_info(SIGTRAP, &info, tsk);
      
      	/* Disable additional traps. They'll be re-enabled when
      	 * the signal is delivered.
      	 */
      clear_dr7:
      	__asm__("movl %0,%%db7"
      		: /* no output */
      		: "r" (0));
 566  	return;
      
      debug_vm86:
      	handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
 570  	return;
      
      clear_TF:
      	regs->eflags &= ~TF_MASK;
 574  	return;
      }
      
      /*
       * Note that we play around with the 'TS' bit in an attempt to get
       * the correct behaviour even in the presence of the asynchronous
       * IRQ13 behaviour
       */
 582  void math_error(void *eip)
      {
      	struct task_struct * task;
      	siginfo_t info;
      	unsigned short cwd, swd;
      
      	/*
      	 * Save the info for the exception handler and clear the error.
      	 */
      	task = current;
      	save_init_fpu(task);
      	task->thread.trap_no = 16;
      	task->thread.error_code = 0;
      	info.si_signo = SIGFPE;
      	info.si_errno = 0;
      	info.si_code = __SI_FAULT;
      	info.si_addr = eip;
      	/*
      	 * (~cwd & swd) will mask out exceptions that are not set to unmasked
      	 * status.  0x3f is the exception bits in these regs, 0x200 is the
      	 * C1 reg you need in case of a stack fault, 0x040 is the stack
      	 * fault bit.  We should only be taking one exception at a time,
      	 * so if this combination doesn't produce any single exception,
      	 * then we have a bad program that isn't syncronizing its FPU usage
      	 * and it will suffer the consequences since we won't be able to
      	 * fully reproduce the context of the exception
      	 */
      	cwd = get_fpu_cwd(task);
      	swd = get_fpu_swd(task);
 611  	switch (((~cwd) & swd & 0x3f) | (swd & 0x240)) {
 612  		case 0x000:
 613  		default:
 614  			break;
 615  		case 0x001: /* Invalid Op */
 616  		case 0x040: /* Stack Fault */
 617  		case 0x240: /* Stack Fault | Direction */
      			info.si_code = FPE_FLTINV;
 619  			break;
 620  		case 0x002: /* Denormalize */
 621  		case 0x010: /* Underflow */
      			info.si_code = FPE_FLTUND;
 623  			break;
 624  		case 0x004: /* Zero Divide */
      			info.si_code = FPE_FLTDIV;
 626  			break;
 627  		case 0x008: /* Overflow */
      			info.si_code = FPE_FLTOVF;
 629  			break;
 630  		case 0x020: /* Precision */
      			info.si_code = FPE_FLTRES;
 632  			break;
      	}
      	force_sig_info(SIGFPE, &info, task);
      }
      
 637  asmlinkage void do_coprocessor_error(struct pt_regs * regs, long error_code)
      {
      	ignore_irq13 = 1;
      	math_error((void *)regs->eip);
      }
      
 643  void simd_math_error(void *eip)
      {
      	struct task_struct * task;
      	siginfo_t info;
      	unsigned short mxcsr;
      
      	/*
      	 * Save the info for the exception handler and clear the error.
      	 */
      	task = current;
      	save_init_fpu(task);
      	task->thread.trap_no = 19;
      	task->thread.error_code = 0;
      	info.si_signo = SIGFPE;
      	info.si_errno = 0;
      	info.si_code = __SI_FAULT;
      	info.si_addr = eip;
      	/*
      	 * The SIMD FPU exceptions are handled a little differently, as there
      	 * is only a single status/control register.  Thus, to determine which
      	 * unmasked exception was caught we must mask the exception mask bits
      	 * at 0x1f80, and then use these to mask the exception bits at 0x3f.
      	 */
      	mxcsr = get_fpu_mxcsr(task);
 667  	switch (~((mxcsr & 0x1f80) >> 7) & (mxcsr & 0x3f)) {
 668  		case 0x000:
 669  		default:
 670  			break;
 671  		case 0x001: /* Invalid Op */
      			info.si_code = FPE_FLTINV;
 673  			break;
 674  		case 0x002: /* Denormalize */
 675  		case 0x010: /* Underflow */
      			info.si_code = FPE_FLTUND;
 677  			break;
 678  		case 0x004: /* Zero Divide */
      			info.si_code = FPE_FLTDIV;
 680  			break;
 681  		case 0x008: /* Overflow */
      			info.si_code = FPE_FLTOVF;
 683  			break;
 684  		case 0x020: /* Precision */
      			info.si_code = FPE_FLTRES;
 686  			break;
      	}
      	force_sig_info(SIGFPE, &info, task);
      }
      
 691  asmlinkage void do_simd_coprocessor_error(struct pt_regs * regs,
      					  long error_code)
      {
 694  	if (cpu_has_xmm) {
      		/* Handle SIMD FPU exceptions on PIII+ processors. */
      		ignore_irq13 = 1;
      		simd_math_error((void *)regs->eip);
 698  	} else {
      		/*
      		 * Handle strange cache flush from user space exception
      		 * in all other cases.  This is undocumented behaviour.
      		 */
 703  		if (regs->eflags & VM_MASK) {
      			handle_vm86_fault((struct kernel_vm86_regs *)regs,
      					  error_code);
 706  			return;
      		}
      		die_if_kernel("cache flush denied", regs, error_code);
      		current->thread.trap_no = 19;
      		current->thread.error_code = error_code;
      		force_sig(SIGSEGV, current);
      	}
      }
      
 715  asmlinkage void do_spurious_interrupt_bug(struct pt_regs * regs,
      					  long error_code)
      {
      #if 0
      	/* No need to warn about this any longer. */
      	printk("Ignoring P6 Local APIC Spurious Interrupt Bug...\n");
      #endif
      }
      
      /*
       *  'math_state_restore()' saves the current math information in the
       * old math state array, and gets the new ones from the current task
       *
       * Careful.. There are problems with IBM-designed IRQ13 behaviour.
       * Don't touch unless you *really* know how it works.
       */
 731  asmlinkage void math_state_restore(struct pt_regs regs)
      {
      	__asm__ __volatile__("clts");		/* Allow maths ops (or we recurse) */
      
 735  	if (current->used_math) {
      		restore_fpu(current);
 737  	} else {
      		init_fpu();
      	}
      	current->flags |= PF_USEDFPU;	/* So we fnsave on switch_to() */
      }
      
      #ifndef CONFIG_MATH_EMULATION
      
 745  asmlinkage void math_emulate(long arg)
      {
      	printk("math-emulation not enabled and no coprocessor found.\n");
      	printk("killing %s.\n",current->comm);
      	force_sig(SIGFPE,current);
      	schedule();
      }
      
      #endif /* CONFIG_MATH_EMULATION */
      
      #ifndef CONFIG_M686
 756  void __init trap_init_f00f_bug(void)
      {
      	unsigned long page;
      	pgd_t * pgd;
      	pmd_t * pmd;
      	pte_t * pte;
      
      	/*
      	 * Allocate a new page in virtual address space, 
      	 * move the IDT into it and write protect this page.
      	 */
      	page = (unsigned long) vmalloc(PAGE_SIZE);
      	pgd = pgd_offset(&init_mm, page);
      	pmd = pmd_offset(pgd, page);
      	pte = pte_offset(pmd, page);
      	__free_page(pte_page(*pte));
      	*pte = mk_pte_phys(__pa(&idt_table), PAGE_KERNEL_RO);
      	/*
      	 * Not that any PGE-capable kernel should have the f00f bug ...
      	 */
 776  	__flush_tlb_all();
      
      	/*
      	 * "idt" is magic - it overlaps the idt_descr
      	 * variable so that updating idt will automatically
      	 * update the idt descriptor..
      	 */
      	idt = (struct desc_struct *)page;
      	__asm__ __volatile__("lidt %0": "=m" (idt_descr));
      }
      #endif
      
      #define _set_gate(gate_addr,type,dpl,addr) \
      do { \
        int __d0, __d1; \
        __asm__ __volatile__ ("movw %%dx,%%ax\n\t" \
      	"movw %4,%%dx\n\t" \
      	"movl %%eax,%0\n\t" \
      	"movl %%edx,%1" \
      	:"=m" (*((long *) (gate_addr))), \
      	 "=m" (*(1+(long *) (gate_addr))), "=&a" (__d0), "=&d" (__d1) \
      	:"i" ((short) (0x8000+(dpl<<13)+(type<<8))), \
      	 "3" ((char *) (addr)),"2" (__KERNEL_CS << 16)); \
      } while (0)
      
      
      /*
       * This needs to use 'idt_table' rather than 'idt', and
       * thus use the _nonmapped_ version of the IDT, as the
       * Pentium F0 0F bugfix can have resulted in the mapped
       * IDT being write-protected.
       */
 808  void set_intr_gate(unsigned int n, void *addr)
      {
 810  	_set_gate(idt_table+n,14,0,addr);
      }
      
 813  static void __init set_trap_gate(unsigned int n, void *addr)
      {
 815  	_set_gate(idt_table+n,15,0,addr);
      }
      
 818  static void __init set_system_gate(unsigned int n, void *addr)
      {
 820  	_set_gate(idt_table+n,15,3,addr);
      }
      
 823  static void __init set_call_gate(void *a, void *addr)
      {
 825  	_set_gate(a,12,3,addr);
      }
      
      #define _set_seg_desc(gate_addr,type,dpl,base,limit) {\
      	*((gate_addr)+1) = ((base) & 0xff000000) | \
      		(((base) & 0x00ff0000)>>16) | \
      		((limit) & 0xf0000) | \
      		((dpl)<<13) | \
      		(0x00408000) | \
      		((type)<<8); \
      	*(gate_addr) = (((base) & 0x0000ffff)<<16) | \
      		((limit) & 0x0ffff); }
      
      #define _set_tssldt_desc(n,addr,limit,type) \
      __asm__ __volatile__ ("movw %w3,0(%2)\n\t" \
      	"movw %%ax,2(%2)\n\t" \
      	"rorl $16,%%eax\n\t" \
      	"movb %%al,4(%2)\n\t" \
      	"movb %4,5(%2)\n\t" \
      	"movb $0,6(%2)\n\t" \
      	"movb %%ah,7(%2)\n\t" \
      	"rorl $16,%%eax" \
      	: "=m"(*(n)) : "a" (addr), "r"(n), "ir"(limit), "i"(type))
      
 849  void set_tss_desc(unsigned int n, void *addr)
      {
      	_set_tssldt_desc(gdt_table+__TSS(n), (int)addr, 235, 0x89);
      }
      
 854  void set_ldt_desc(unsigned int n, void *addr, unsigned int size)
      {
      	_set_tssldt_desc(gdt_table+__LDT(n), (int)addr, ((size << 3)-1), 0x82);
      }
      
      #ifdef CONFIG_X86_VISWS_APIC
      
      /*
       * On Rev 005 motherboards legacy device interrupt lines are wired directly
       * to Lithium from the 307.  But the PROM leaves the interrupt type of each
       * 307 logical device set appropriate for the 8259.  Later we'll actually use
       * the 8259, but for now we have to flip the interrupt types to
       * level triggered, active lo as required by Lithium.
       */
      
      #define	REG	0x2e	/* The register to read/write */
      #define	DEV	0x07	/* Register: Logical device select */
      #define	VAL	0x2f	/* The value to read/write */
      
      static void
      superio_outb(int dev, int reg, int val)
      {
      	outb(DEV, REG);
      	outb(dev, VAL);
      	outb(reg, REG);
      	outb(val, VAL);
      }
      
      static int __attribute__ ((unused))
      superio_inb(int dev, int reg)
      {
      	outb(DEV, REG);
      	outb(dev, VAL);
      	outb(reg, REG);
      	return inb(VAL);
      }
      
      #define	FLOP	3	/* floppy logical device */
      #define	PPORT	4	/* parallel logical device */
      #define	UART5	5	/* uart2 logical device (not wired up) */
      #define	UART6	6	/* uart1 logical device (THIS is the serial port!) */
      #define	IDEST	0x70	/* int. destination (which 307 IRQ line) reg. */
      #define	ITYPE	0x71	/* interrupt type register */
      
      /* interrupt type bits */
      #define	LEVEL	0x01	/* bit 0, 0 == edge triggered */
      #define	ACTHI	0x02	/* bit 1, 0 == active lo */
      
      static void
      superio_init(void)
      {
      	if (visws_board_type == VISWS_320 && visws_board_rev == 5) {
      		superio_outb(UART6, IDEST, 0);	/* 0 means no intr propagated */
      		printk("SGI 320 rev 5: disabling 307 uart1 interrupt\n");
      	}
      }
      
      static void
      lithium_init(void)
      {
      	set_fixmap(FIX_LI_PCIA, LI_PCI_A_PHYS);
      	printk("Lithium PCI Bridge A, Bus Number: %d\n",
      				li_pcia_read16(LI_PCI_BUSNUM) & 0xff);
      	set_fixmap(FIX_LI_PCIB, LI_PCI_B_PHYS);
      	printk("Lithium PCI Bridge B (PIIX4), Bus Number: %d\n",
      				li_pcib_read16(LI_PCI_BUSNUM) & 0xff);
      
      	/* XXX blindly enables all interrupts */
      	li_pcia_write16(LI_PCI_INTEN, 0xffff);
      	li_pcib_write16(LI_PCI_INTEN, 0xffff);
      }
      
      static void
      cobalt_init(void)
      {
      	/*
      	 * On normal SMP PC this is used only with SMP, but we have to
      	 * use it and set it up here to start the Cobalt clock
      	 */
      	set_fixmap(FIX_APIC_BASE, APIC_DEFAULT_PHYS_BASE);
      	printk("Local APIC ID %lx\n", apic_read(APIC_ID));
      	printk("Local APIC Version %lx\n", apic_read(APIC_LVR));
      
      	set_fixmap(FIX_CO_CPU, CO_CPU_PHYS);
      	printk("Cobalt Revision %lx\n", co_cpu_read(CO_CPU_REV));
      
      	set_fixmap(FIX_CO_APIC, CO_APIC_PHYS);
      	printk("Cobalt APIC ID %lx\n", co_apic_read(CO_APIC_ID));
      
      	/* Enable Cobalt APIC being careful to NOT change the ID! */
      	co_apic_write(CO_APIC_ID, co_apic_read(CO_APIC_ID)|CO_APIC_ENABLE);
      
      	printk("Cobalt APIC enabled: ID reg %lx\n", co_apic_read(CO_APIC_ID));
      }
      #endif
 949  void __init trap_init(void)
      {
      #ifdef CONFIG_EISA
      	if (isa_readl(0x0FFFD9) == 'E'+('I'<<8)+('S'<<16)+('A'<<24))
      		EISA_bus = 1;
      #endif
      
      	set_trap_gate(0,÷_error);
      	set_trap_gate(1,&debug);
      	set_intr_gate(2,&nmi);
      	set_system_gate(3,&int3);	/* int3-5 can be called from all */
      	set_system_gate(4,&overflow);
      	set_system_gate(5,&bounds);
      	set_trap_gate(6,&invalid_op);
      	set_trap_gate(7,&device_not_available);
      	set_trap_gate(8,&double_fault);
      	set_trap_gate(9,&coprocessor_segment_overrun);
      	set_trap_gate(10,&invalid_TSS);
      	set_trap_gate(11,&segment_not_present);
      	set_trap_gate(12,&stack_segment);
      	set_trap_gate(13,&general_protection);
      	set_trap_gate(14,&page_fault);
      	set_trap_gate(15,&spurious_interrupt_bug);
      	set_trap_gate(16,&coprocessor_error);
      	set_trap_gate(17,&alignment_check);
      	set_trap_gate(18,&machine_check);
      	set_trap_gate(19,&simd_coprocessor_error);
      
      	set_system_gate(SYSCALL_VECTOR,&system_call);
      
      	/*
      	 * default LDT is a single-entry callgate to lcall7 for iBCS
      	 * and a callgate to lcall27 for Solaris/x86 binaries
      	 */
      	set_call_gate(&default_ldt[0],lcall7);
      	set_call_gate(&default_ldt[4],lcall27);
      
      	/*
      	 * Should be a barrier for any external CPU state.
      	 */
      	cpu_init();
      
      #ifdef CONFIG_X86_VISWS_APIC
      	superio_init();
      	lithium_init();
      	cobalt_init();
      #endif
      }