traps.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1994 - 1999, 2000, 01, 06 Ralf Baechle
 * Copyright (C) 1995, 1996 Paul M. Antoine
 * Copyright (C) 1998 Ulf Carlsson
 * Copyright (C) 1999 Silicon Graphics, Inc.
 * Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
 * Copyright (C) 2002, 2003, 2004, 2005, 2007  Maciej W. Rozycki
 * Copyright (C) 2000, 2001, 2012 MIPS Technologies, Inc.  All rights reserved.
 * Copyright (C) 2014, Imagination Technologies Ltd.
 */
#include <linux/bitops.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/context_tracking.h>
#include <linux/cpu_pm.h>
#include <linux/kexec.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/extable.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/sched/debug.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/memblock.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/kgdb.h>
#include <linux/kdebug.h>
#include <linux/kprobes.h>
#include <linux/notifier.h>
#include <linux/kdb.h>
#include <linux/irq.h>
#include <linux/perf_event.h>

#include <asm/addrspace.h>
#include <asm/bootinfo.h>
#include <asm/branch.h>
#include <asm/break.h>
#include <asm/cop2.h>
#include <asm/cpu.h>
#include <asm/cpu-type.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/fpu_emulator.h>
#include <asm/idle.h>
#include <asm/mips-cps.h>
#include <asm/mips-r2-to-r6-emul.h>
#include <asm/mipsregs.h>
#include <asm/mipsmtregs.h>
#include <asm/module.h>
#include <asm/msa.h>
#include <asm/pgtable.h>
#include <asm/ptrace.h>
#include <asm/sections.h>
#include <asm/siginfo.h>
#include <asm/tlbdebug.h>
#include <asm/traps.h>
#include <linux/uaccess.h>
#include <asm/watch.h>
#include <asm/mmu_context.h>
#include <asm/types.h>
#include <asm/stacktrace.h>
#include <asm/tlbex.h>
#include <asm/uasm.h>

extern void check_wait(void);
extern asmlinkage void rollback_handle_int(void);
extern asmlinkage void handle_int(void);
extern asmlinkage void handle_adel(void);
extern asmlinkage void handle_ades(void);
extern asmlinkage void handle_ibe(void);
extern asmlinkage void handle_dbe(void);
extern asmlinkage void handle_sys(void);
extern asmlinkage void handle_bp(void);
extern asmlinkage void handle_ri(void);
extern asmlinkage void handle_ri_rdhwr_tlbp(void);
extern asmlinkage void handle_ri_rdhwr(void);
extern asmlinkage void handle_cpu(void);
extern asmlinkage void handle_ov(void);
extern asmlinkage void handle_tr(void);
extern asmlinkage void handle_msa_fpe(void);
extern asmlinkage void handle_fpe(void);
extern asmlinkage void handle_ftlb(void);
extern asmlinkage void handle_msa(void);
extern asmlinkage void handle_mdmx(void);
extern asmlinkage void handle_watch(void);
extern asmlinkage void handle_mt(void);
extern asmlinkage void handle_dsp(void);
extern asmlinkage void handle_mcheck(void);
extern asmlinkage void handle_reserved(void);
extern void tlb_do_page_fault_0(void);

void (*board_be_init)(void);
int (*board_be_handler)(struct pt_regs *regs, int is_fixup);
void (*board_nmi_handler_setup)(void);
void (*board_ejtag_handler_setup)(void);
void (*board_bind_eic_interrupt)(int irq, int regset);
void (*board_ebase_setup)(void);
void(*board_cache_error_setup)(void);

static void show_raw_backtrace(unsigned long reg29)
{
	unsigned long *sp = (unsigned long *)(reg29 & ~3);
	unsigned long addr;

	printk("Call Trace:");
#ifdef CONFIG_KALLSYMS
	printk("\n");
#endif
	while (!kstack_end(sp)) {
		unsigned long __user *p =
			(unsigned long __user *)(unsigned long)sp++;
		if (__get_user(addr, p)) {
			printk(" (Bad stack address)");
			break;
		}
		if (__kernel_text_address(addr))
			print_ip_sym(addr);
	}
	printk("\n");
}

#ifdef CONFIG_KALLSYMS
int raw_show_trace;
static int __init set_raw_show_trace(char *str)
{
	raw_show_trace = 1;
	return 1;
}
__setup("raw_show_trace", set_raw_show_trace);
#endif

static void show_backtrace(struct task_struct *task, const struct pt_regs *regs)
{
	unsigned long sp = regs->regs[29];
	unsigned long ra = regs->regs[31];
	unsigned long pc = regs->cp0_epc;

	if (!task)
		task = current;

	if (raw_show_trace || user_mode(regs) || !__kernel_text_address(pc)) {
		show_raw_backtrace(sp);
		return;
	}
	printk("Call Trace:\n");
	do {
		print_ip_sym(pc);
		pc = unwind_stack(task, &sp, pc, &ra);
	} while (pc);
	pr_cont("\n");
}

/*
 * This routine abuses get_user()/put_user() to reference pointers
 * with at least a bit of error checking ...
 */
static void show_stacktrace(struct task_struct *task,
	const struct pt_regs *regs)
{
	const int field = 2 * sizeof(unsigned long);
	long stackdata;
	int i;
	unsigned long __user *sp = (unsigned long __user *)regs->regs[29];

	printk("Stack :");
	i = 0;
	while ((unsigned long) sp & (PAGE_SIZE - 1)) {
		if (i && ((i % (64 / field)) == 0)) {
			pr_cont("\n");
			printk("       ");
		}
		if (i > 39) {
			pr_cont(" ...");
			break;
		}

		if (__get_user(stackdata, sp++)) {
			pr_cont(" (Bad stack address)");
			break;
		}

		pr_cont(" %0*lx", field, stackdata);
		i++;
	}
	pr_cont("\n");
	show_backtrace(task, regs);
}

void show_stack(struct task_struct *task, unsigned long *sp)
{
	struct pt_regs regs;
	mm_segment_t old_fs = get_fs();

	regs.cp0_status = KSU_KERNEL;
	if (sp) {
		regs.regs[29] = (unsigned long)sp;
		regs.regs[31] = 0;
		regs.cp0_epc = 0;
	} else {
		if (task && task != current) {
			regs.regs[29] = task->thread.reg29;
			regs.regs[31] = 0;
			regs.cp0_epc = task->thread.reg31;
#ifdef CONFIG_KGDB_KDB
		} else if (atomic_read(&kgdb_active) != -1 &&
			   kdb_current_regs) {
			memcpy(&regs, kdb_current_regs, sizeof(regs));
#endif /* CONFIG_KGDB_KDB */
		} else {
			prepare_frametrace(&regs);
		}
	}
	/*
	 * show_stack() deals exclusively with kernel mode, so be sure to access
	 * the stack in the kernel (not user) address space.
	 */
	set_fs(KERNEL_DS);
	show_stacktrace(task, &regs);
	set_fs(old_fs);
}

static void show_code(unsigned int __user *pc)
{
	long i;
	unsigned short __user *pc16 = NULL;

	printk("Code:");

	if ((unsigned long)pc & 1)
		pc16 = (unsigned short __user *)((unsigned long)pc & ~1);
	for(i = -3 ; i < 6 ; i++) {
		unsigned int insn;
		if (pc16 ? __get_user(insn, pc16 + i) : __get_user(insn, pc + i)) {
			pr_cont(" (Bad address in epc)\n");
			break;
		}
		pr_cont("%c%0*x%c", (i?' ':'<'), pc16 ? 4 : 8, insn, (i?' ':'>'));
	}
	pr_cont("\n");
}

static void __show_regs(const struct pt_regs *regs)
{
	const int field = 2 * sizeof(unsigned long);
	unsigned int cause = regs->cp0_cause;
	unsigned int exccode;
	int i;

	show_regs_print_info(KERN_DEFAULT);

	/*
	 * Saved main processor registers
	 */
	for (i = 0; i < 32; ) {
		if ((i % 4) == 0)
			printk("$%2d   :", i);
		if (i == 0)
			pr_cont(" %0*lx", field, 0UL);
		else if (i == 26 || i == 27)
			pr_cont(" %*s", field, "");
		else
			pr_cont(" %0*lx", field, regs->regs[i]);

		i++;
		if ((i % 4) == 0)
			pr_cont("\n");
	}

#ifdef CONFIG_CPU_HAS_SMARTMIPS
	printk("Acx    : %0*lx\n", field, regs->acx);
#endif
	printk("Hi    : %0*lx\n", field, regs->hi);
	printk("Lo    : %0*lx\n", field, regs->lo);

	/*
	 * Saved cp0 registers
	 */
	printk("epc   : %0*lx %pS\n", field, regs->cp0_epc,
	       (void *) regs->cp0_epc);
	printk("ra    : %0*lx %pS\n", field, regs->regs[31],
	       (void *) regs->regs[31]);

	printk("Status: %08x	", (uint32_t) regs->cp0_status);

	if (cpu_has_3kex) {
		if (regs->cp0_status & ST0_KUO)
			pr_cont("KUo ");
		if (regs->cp0_status & ST0_IEO)
			pr_cont("IEo ");
		if (regs->cp0_status & ST0_KUP)
			pr_cont("KUp ");
		if (regs->cp0_status & ST0_IEP)
			pr_cont("IEp ");
		if (regs->cp0_status & ST0_KUC)
			pr_cont("KUc ");
		if (regs->cp0_status & ST0_IEC)
			pr_cont("IEc ");
	} else if (cpu_has_4kex) {
		if (regs->cp0_status & ST0_KX)
			pr_cont("KX ");
		if (regs->cp0_status & ST0_SX)
			pr_cont("SX ");
		if (regs->cp0_status & ST0_UX)
			pr_cont("UX ");
		switch (regs->cp0_status & ST0_KSU) {
		case KSU_USER:
			pr_cont("USER ");
			break;
		case KSU_SUPERVISOR:
			pr_cont("SUPERVISOR ");
			break;
		case KSU_KERNEL:
			pr_cont("KERNEL ");
			break;
		default:
			pr_cont("BAD_MODE ");
			break;
		}
		if (regs->cp0_status & ST0_ERL)
			pr_cont("ERL ");
		if (regs->cp0_status & ST0_EXL)
			pr_cont("EXL ");
		if (regs->cp0_status & ST0_IE)
			pr_cont("IE ");
	}
	pr_cont("\n");

	exccode = (cause & CAUSEF_EXCCODE) >> CAUSEB_EXCCODE;
	printk("Cause : %08x (ExcCode %02x)\n", cause, exccode);

	if (1 <= exccode && exccode <= 5)
		printk("BadVA : %0*lx\n", field, regs->cp0_badvaddr);

	printk("PrId  : %08x (%s)\n", read_c0_prid(),
	       cpu_name_string());
}

/*
 * FIXME: really the generic show_regs should take a const pointer argument.
 */
void show_regs(struct pt_regs *regs)
{
	__show_regs(regs);
	dump_stack();
}

void show_registers(struct pt_regs *regs)
{
	const int field = 2 * sizeof(unsigned long);
	mm_segment_t old_fs = get_fs();

	__show_regs(regs);
	print_modules();
	printk("Process %s (pid: %d, threadinfo=%p, task=%p, tls=%0*lx)\n",
	       current->comm, current->pid, current_thread_info(), current,
	      field, current_thread_info()->tp_value);
	if (cpu_has_userlocal) {
		unsigned long tls;

		tls = read_c0_userlocal();
		if (tls != current_thread_info()->tp_value)
			printk("*HwTLS: %0*lx\n", field, tls);
	}

	if (!user_mode(regs))
		/* Necessary for getting the correct stack content */
		set_fs(KERNEL_DS);
	show_stacktrace(current, regs);
	show_code((unsigned int __user *) regs->cp0_epc);
	printk("\n");
	set_fs(old_fs);
}

static DEFINE_RAW_SPINLOCK(die_lock);

void __noreturn die(const char *str, struct pt_regs *regs)
{
	static int die_counter;
	int sig = SIGSEGV;

	oops_enter();

	if (notify_die(DIE_OOPS, str, regs, 0, current->thread.trap_nr,
		       SIGSEGV) == NOTIFY_STOP)
		sig = 0;

	console_verbose();
	raw_spin_lock_irq(&die_lock);
	bust_spinlocks(1);

	printk("%s[#%d]:\n", str, ++die_counter);
	show_registers(regs);
	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
	raw_spin_unlock_irq(&die_lock);

	oops_exit();

	if (in_interrupt())
		panic("Fatal exception in interrupt");

	if (panic_on_oops)
		panic("Fatal exception");

	if (regs && kexec_should_crash(current))
		crash_kexec(regs);

	do_exit(sig);
}

extern struct exception_table_entry __start___dbe_table[];
extern struct exception_table_entry __stop___dbe_table[];

__asm__(
"	.section	__dbe_table, \"a\"\n"
"	.previous			\n");

/* Given an address, look for it in the exception tables. */
static const struct exception_table_entry *search_dbe_tables(unsigned long addr)
{
	const struct exception_table_entry *e;

	e = search_extable(__start___dbe_table,
			   __stop___dbe_table - __start___dbe_table, addr);
	if (!e)
		e = search_module_dbetables(addr);
	return e;
}

asmlinkage void do_be(struct pt_regs *regs)
{
	const int field = 2 * sizeof(unsigned long);
	const struct exception_table_entry *fixup = NULL;
	int data = regs->cp0_cause & 4;
	int action = MIPS_BE_FATAL;
	enum ctx_state prev_state;

	prev_state = exception_enter();
	/* XXX For now.	 Fixme, this searches the wrong table ...  */
	if (data && !user_mode(regs))
		fixup = search_dbe_tables(exception_epc(regs));

	if (fixup)
		action = MIPS_BE_FIXUP;

	if (board_be_handler)
		action = board_be_handler(regs, fixup != NULL);
	else
		mips_cm_error_report();

	switch (action) {
	case MIPS_BE_DISCARD:
		goto out;
	case MIPS_BE_FIXUP:
		if (fixup) {
			regs->cp0_epc = fixup->nextinsn;
			goto out;
		}
		break;
	default:
		break;
	}

	/*
	 * Assume it would be too dangerous to continue ...
	 */
	printk(KERN_ALERT "%s bus error, epc == %0*lx, ra == %0*lx\n",
	       data ? "Data" : "Instruction",
	       field, regs->cp0_epc, field, regs->regs[31]);
	if (notify_die(DIE_OOPS, "bus error", regs, 0, current->thread.trap_nr,
		       SIGBUS) == NOTIFY_STOP)
		goto out;

	die_if_kernel("Oops", regs);
	force_sig(SIGBUS, current);

out:
	exception_exit(prev_state);
}

/*
 * ll/sc, rdhwr, sync emulation
 */

#define OPCODE 0xfc000000
#define BASE   0x03e00000
#define RT     0x001f0000
#define OFFSET 0x0000ffff
#define LL     0xc0000000
#define SC     0xe0000000
#define SPEC0  0x00000000
#define SPEC3  0x7c000000
#define RD     0x0000f800
#define FUNC   0x0000003f
#define SYNC   0x0000000f
#define RDHWR  0x0000003b

/*  microMIPS definitions   */
#define MM_POOL32A_FUNC 0xfc00ffff
#define MM_RDHWR        0x00006b3c
#define MM_RS           0x001f0000
#define MM_RT           0x03e00000

/*
 * The ll_bit is cleared by r*_switch.S
 */

unsigned int ll_bit;
struct task_struct *ll_task;

static inline int simulate_ll(struct pt_regs *regs, unsigned int opcode)
{
	unsigned long value, __user *vaddr;
	long offset;

	/*
	 * analyse the ll instruction that just caused a ri exception
	 * and put the referenced address to addr.
	 */

	/* sign extend offset */
	offset = opcode & OFFSET;
	offset <<= 16;
	offset >>= 16;

	vaddr = (unsigned long __user *)
		((unsigned long)(regs->regs[(opcode & BASE) >> 21]) + offset);

	if ((unsigned long)vaddr & 3)
		return SIGBUS;
	if (get_user(value, vaddr))
		return SIGSEGV;

	preempt_disable();

	if (ll_task == NULL || ll_task == current) {
		ll_bit = 1;
	} else {
		ll_bit = 0;
	}
	ll_task = current;

	preempt_enable();

	regs->regs[(opcode & RT) >> 16] = value;

	return 0;
}

static inline int simulate_sc(struct pt_regs *regs, unsigned int opcode)
{
	unsigned long __user *vaddr;
	unsigned long reg;
	long offset;

	/*
	 * analyse the sc instruction that just caused a ri exception
	 * and put the referenced address to addr.
	 */

	/* sign extend offset */
	offset = opcode & OFFSET;
	offset <<= 16;
	offset >>= 16;

	vaddr = (unsigned long __user *)
		((unsigned long)(regs->regs[(opcode & BASE) >> 21]) + offset);
	reg = (opcode & RT) >> 16;

	if ((unsigned long)vaddr & 3)
		return SIGBUS;

	preempt_disable();

	if (ll_bit == 0 || ll_task != current) {
		regs->regs[reg] = 0;
		preempt_enable();
		return 0;
	}

	preempt_enable();

	if (put_user(regs->regs[reg], vaddr))
		return SIGSEGV;

	regs->regs[reg] = 1;

	return 0;
}

/*
 * ll uses the opcode of lwc0 and sc uses the opcode of swc0.  That is both
 * opcodes are supposed to result in coprocessor unusable exceptions if
 * executed on ll/sc-less processors.  That's the theory.  In practice a
 * few processors such as NEC's VR4100 throw reserved instruction exceptions
 * instead, so we're doing the emulation thing in both exception handlers.
 */
static int simulate_llsc(struct pt_regs *regs, unsigned int opcode)
{
	if ((opcode & OPCODE) == LL) {
		perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS,
				1, regs, 0);
		return simulate_ll(regs, opcode);
	}
	if ((opcode & OPCODE) == SC) {
		perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS,
				1, regs, 0);
		return simulate_sc(regs, opcode);
	}

	return -1;			/* Must be something else ... */
}

/*
 * Simulate trapping 'rdhwr' instructions to provide user accessible
 * registers not implemented in hardware.
 */
static int simulate_rdhwr(struct pt_regs *regs, int rd, int rt)
{
	struct thread_info *ti = task_thread_info(current);

	perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS,
			1, regs, 0);
	switch (rd) {
	case MIPS_HWR_CPUNUM:		/* CPU number */
		regs->regs[rt] = smp_processor_id();
		return 0;
	case MIPS_HWR_SYNCISTEP:	/* SYNCI length */
		regs->regs[rt] = min(current_cpu_data.dcache.linesz,
				     current_cpu_data.icache.linesz);
		return 0;
	case MIPS_HWR_CC:		/* Read count register */
		regs->regs[rt] = read_c0_count();
		return 0;
	case MIPS_HWR_CCRES:		/* Count register resolution */
		switch (current_cpu_type()) {
		case CPU_20KC:
		case CPU_25KF:
			regs->regs[rt] = 1;
			break;
		default:
			regs->regs[rt] = 2;
		}
		return 0;
	case MIPS_HWR_ULR:		/* Read UserLocal register */
		regs->regs[rt] = ti->tp_value;
		return 0;
	default:
		return -1;
	}
}

static int simulate_rdhwr_normal(struct pt_regs *regs, unsigned int opcode)
{
	if ((opcode & OPCODE) == SPEC3 && (opcode & FUNC) == RDHWR) {
		int rd = (opcode & RD) >> 11;
		int rt = (opcode & RT) >> 16;

		simulate_rdhwr(regs, rd, rt);
		return 0;
	}

	/* Not ours.  */
	return -1;
}

static int simulate_rdhwr_mm(struct pt_regs *regs, unsigned int opcode)
{
	if ((opcode & MM_POOL32A_FUNC) == MM_RDHWR) {
		int rd = (opcode & MM_RS) >> 16;
		int rt = (opcode & MM_RT) >> 21;
		simulate_rdhwr(regs, rd, rt);
		return 0;
	}

	/* Not ours.  */
	return -1;
}

static int simulate_sync(struct pt_regs *regs, unsigned int opcode)
{
	if ((opcode & OPCODE) == SPEC0 && (opcode & FUNC) == SYNC) {
		perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS,
				1, regs, 0);
		return 0;
	}

	return -1;			/* Must be something else ... */
}

asmlinkage void do_ov(struct pt_regs *regs)
{
	enum ctx_state prev_state;

	prev_state = exception_enter();
	die_if_kernel("Integer overflow", regs);

	force_sig_fault(SIGFPE, FPE_INTOVF, (void __user *)regs->cp0_epc, current);
	exception_exit(prev_state);
}

/*
 * Send SIGFPE according to FCSR Cause bits, which must have already
 * been masked against Enable bits.  This is impotant as Inexact can
 * happen together with Overflow or Underflow, and `ptrace' can set
 * any bits.
 */
void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
		     struct task_struct *tsk)
{
	int si_code = FPE_FLTUNK;

	if (fcr31 & FPU_CSR_INV_X)
		si_code = FPE_FLTINV;
	else if (fcr31 & FPU_CSR_DIV_X)
		si_code = FPE_FLTDIV;
	else if (fcr31 & FPU_CSR_OVF_X)
		si_code = FPE_FLTOVF;
	else if (fcr31 & FPU_CSR_UDF_X)
		si_code = FPE_FLTUND;
	else if (fcr31 & FPU_CSR_INE_X)
		si_code = FPE_FLTRES;

	force_sig_fault(SIGFPE, si_code, fault_addr, tsk);
}

int process_fpemu_return(int sig, void __user *fault_addr, unsigned long fcr31)
{
	int si_code;
	struct vm_area_struct *vma;

	switch (sig) {
	case 0:
		return 0;

	case SIGFPE:
		force_fcr31_sig(fcr31, fault_addr, current);
		return 1;

	case SIGBUS:
		force_sig_fault(SIGBUS, BUS_ADRERR, fault_addr, current);
		return 1;

	case SIGSEGV:
		down_read(&current->mm->mmap_sem);
		vma = find_vma(current->mm, (unsigned long)fault_addr);
		if (vma && (vma->vm_start <= (unsigned long)fault_addr))
			si_code = SEGV_ACCERR;
		else
			si_code = SEGV_MAPERR;
		up_read(&current->mm->mmap_sem);
		force_sig_fault(SIGSEGV, si_code, fault_addr, current);
		return 1;

	default:
		force_sig(sig, current);
		return 1;
	}
}

static int simulate_fp(struct pt_regs *regs, unsigned int opcode,
		       unsigned long old_epc, unsigned long old_ra)
{
	union mips_instruction inst = { .word = opcode };
	void __user *fault_addr;
	unsigned long fcr31;
	int sig;

	/* If it's obviously not an FP instruction, skip it */
	switch (inst.i_format.opcode) {
	case cop1_op:
	case cop1x_op:
	case lwc1_op:
	case ldc1_op:
	case swc1_op:
	case sdc1_op:
		break;

	default:
		return -1;
	}

	/*
	 * do_ri skipped over the instruction via compute_return_epc, undo
	 * that for the FPU emulator.
	 */
	regs->cp0_epc = old_epc;
	regs->regs[31] = old_ra;

	/* Run the emulator */
	sig = fpu_emulator_cop1Handler(regs, &current->thread.fpu, 1,
				       &fault_addr);

	/*
	 * We can't allow the emulated instruction to leave any
	 * enabled Cause bits set in $fcr31.
	 */
	fcr31 = mask_fcr31_x(current->thread.fpu.fcr31);
	current->thread.fpu.fcr31 &= ~fcr31;

	/* Restore the hardware register state */
	own_fpu(1);

	/* Send a signal if required.  */
	process_fpemu_return(sig, fault_addr, fcr31);

	return 0;
}

/*
 * XXX Delayed fp exceptions when doing a lazy ctx switch XXX
 */
asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
{
	enum ctx_state prev_state;
	void __user *fault_addr;
	int sig;

	prev_state = exception_enter();
	if (notify_die(DIE_FP, "FP exception", regs, 0, current->thread.trap_nr,
		       SIGFPE) == NOTIFY_STOP)
		goto out;

	/* Clear FCSR.Cause before enabling interrupts */
	write_32bit_cp1_register(CP1_STATUS, fcr31 & ~mask_fcr31_x(fcr31));
	local_irq_enable();

	die_if_kernel("FP exception in kernel code", regs);

	if (fcr31 & FPU_CSR_UNI_X) {
		/*
		 * Unimplemented operation exception.  If we've got the full
		 * software emulator on-board, let's use it...
		 *
		 * Force FPU to dump state into task/thread context.  We're
		 * moving a lot of data here for what is probably a single
		 * instruction, but the alternative is to pre-decode the FP
		 * register operands before invoking the emulator, which seems
		 * a bit extreme for what should be an infrequent event.
		 */

		/* Run the emulator */
		sig = fpu_emulator_cop1Handler(regs, &current->thread.fpu, 1,
					       &fault_addr);

		/*
		 * We can't allow the emulated instruction to leave any
		 * enabled Cause bits set in $fcr31.
		 */
		fcr31 = mask_fcr31_x(current->thread.fpu.fcr31);
		current->thread.fpu.fcr31 &= ~fcr31;

		/* Restore the hardware register state */
		own_fpu(1);	/* Using the FPU again.	 */
	} else {
		sig = SIGFPE;
		fault_addr = (void __user *) regs->cp0_epc;
	}

	/* Send a signal if required.  */
	process_fpemu_return(sig, fault_addr, fcr31);

out:
	exception_exit(prev_state);
}

void do_trap_or_bp(struct pt_regs *regs, unsigned int code, int si_code,
	const char *str)
{
	char b[40];

#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
	if (kgdb_ll_trap(DIE_TRAP, str, regs, code, current->thread.trap_nr,
			 SIGTRAP) == NOTIFY_STOP)
		return;
#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */

	if (notify_die(DIE_TRAP, str, regs, code, current->thread.trap_nr,
		       SIGTRAP) == NOTIFY_STOP)
		return;

	/*
	 * A short test says that IRIX 5.3 sends SIGTRAP for all trap
	 * insns, even for trap and break codes that indicate arithmetic
	 * failures.  Weird ...
	 * But should we continue the brokenness???  --macro
	 */
	switch (code) {
	case BRK_OVERFLOW:
	case BRK_DIVZERO:
		scnprintf(b, sizeof(b), "%s instruction in kernel code", str);
		die_if_kernel(b, regs);
		force_sig_fault(SIGFPE,
				code == BRK_DIVZERO ? FPE_INTDIV : FPE_INTOVF,
				(void __user *) regs->cp0_epc, current);
		break;
	case BRK_BUG:
		die_if_kernel("Kernel bug detected", regs);
		force_sig(SIGTRAP, current);
		break;
	case BRK_MEMU:
		/*
		 * This breakpoint code is used by the FPU emulator to retake
		 * control of the CPU after executing the instruction from the
		 * delay slot of an emulated branch.
		 *
		 * Terminate if exception was recognized as a delay slot return
		 * otherwise handle as normal.
		 */
		if (do_dsemulret(regs))
			return;

		die_if_kernel("Math emu break/trap", regs);
		force_sig(SIGTRAP, current);
		break;
	default:
		scnprintf(b, sizeof(b), "%s instruction in kernel code", str);
		die_if_kernel(b, regs);
		if (si_code) {
			force_sig_fault(SIGTRAP, si_code, NULL,	current);
		} else {
			force_sig(SIGTRAP, current);
		}
	}
}

asmlinkage void do_bp(struct pt_regs *regs)
{
	unsigned long epc = msk_isa16_mode(exception_epc(regs));
	unsigned int opcode, bcode;
	enum ctx_state prev_state;
	mm_segment_t seg;

	seg = get_fs();
	if (!user_mode(regs))
		set_fs(KERNEL_DS);

	prev_state = exception_enter();
	current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
	if (get_isa16_mode(regs->cp0_epc)) {
		u16 instr[2];

		if (__get_user(instr[0], (u16 __user *)epc))
			goto out_sigsegv;

		if (!cpu_has_mmips) {
			/* MIPS16e mode */
			bcode = (instr[0] >> 5) & 0x3f;
		} else if (mm_insn_16bit(instr[0])) {
			/* 16-bit microMIPS BREAK */
			bcode = instr[0] & 0xf;
		} else {
			/* 32-bit microMIPS BREAK */
			if (__get_user(instr[1], (u16 __user *)(epc + 2)))
				goto out_sigsegv;
			opcode = (instr[0] << 16) | instr[1];
			bcode = (opcode >> 6) & ((1 << 20) - 1);
		}
	} else {
		if (__get_user(opcode, (unsigned int __user *)epc))
			goto out_sigsegv;
		bcode = (opcode >> 6) & ((1 << 20) - 1);
	}

	/*
	 * There is the ancient bug in the MIPS assemblers that the break
	 * code starts left to bit 16 instead to bit 6 in the opcode.
	 * Gas is bug-compatible, but not always, grrr...
	 * We handle both cases with a simple heuristics.  --macro
	 */
	if (bcode >= (1 << 10))
		bcode = ((bcode & ((1 << 10) - 1)) << 10) | (bcode >> 10);

	/*
	 * notify the kprobe handlers, if instruction is likely to
	 * pertain to them.
	 */
	switch (bcode) {
	case BRK_UPROBE:
		if (notify_die(DIE_UPROBE, "uprobe", regs, bcode,
			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
			goto out;
		else
			break;
	case BRK_UPROBE_XOL:
		if (notify_die(DIE_UPROBE_XOL, "uprobe_xol", regs, bcode,
			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
			goto out;
		else
			break;
	case BRK_KPROBE_BP:
		if (notify_die(DIE_BREAK, "debug", regs, bcode,
			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)