text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   */
  
  /*
   * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
   * Copyright (C) 2000-2001 VERITAS Software Corporation.
   * Copyright (C) 2002 Andi Kleen, SuSE Labs
   * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
   * Copyright (C) 2007 MontaVista Software, Inc.
   * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
   */
  /****************************************************************************
   *  Contributor:     Lake Stevens Instrument Division$
   *  Written by:      Glenn Engel $
   *  Updated by:	     Amit Kale<akale@veritas.com>
   *  Updated by:	     Tom Rini <trini@kernel.crashing.org>
   *  Updated by:	     Jason Wessel <jason.wessel@windriver.com>
   *  Modified for 386 by Jim Kingdon, Cygnus Support.
   *  Origianl kgdb, compatibility with 2.1.xx kernel by
   *  David Grothe <dave@gcom.com>
   *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
   *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
   */
  #include <linux/spinlock.h>
  #include <linux/kdebug.h>
  #include <linux/string.h>
  #include <linux/kernel.h>
  #include <linux/ptrace.h>
  #include <linux/sched.h>
  #include <linux/delay.h>
  #include <linux/kgdb.h>
  #include <linux/smp.h>
  #include <linux/nmi.h>
  #include <linux/hw_breakpoint.h>
  #include <linux/uaccess.h>
  #include <linux/memory.h>
  
  #include <asm/text-patching.h>
  #include <asm/debugreg.h>
  #include <asm/apicdef.h>
  #include <asm/apic.h>
  #include <asm/nmi.h>
  #include <asm/switch_to.h>
  
  struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
  {
  #ifdef CONFIG_X86_32
  	{ "ax", 4, offsetof(struct pt_regs, ax) },
  	{ "cx", 4, offsetof(struct pt_regs, cx) },
  	{ "dx", 4, offsetof(struct pt_regs, dx) },
  	{ "bx", 4, offsetof(struct pt_regs, bx) },
  	{ "sp", 4, offsetof(struct pt_regs, sp) },
  	{ "bp", 4, offsetof(struct pt_regs, bp) },
  	{ "si", 4, offsetof(struct pt_regs, si) },
  	{ "di", 4, offsetof(struct pt_regs, di) },
  	{ "ip", 4, offsetof(struct pt_regs, ip) },
  	{ "flags", 4, offsetof(struct pt_regs, flags) },
  	{ "cs", 4, offsetof(struct pt_regs, cs) },
  	{ "ss", 4, offsetof(struct pt_regs, ss) },
  	{ "ds", 4, offsetof(struct pt_regs, ds) },
  	{ "es", 4, offsetof(struct pt_regs, es) },
  #else
  	{ "ax", 8, offsetof(struct pt_regs, ax) },
  	{ "bx", 8, offsetof(struct pt_regs, bx) },
  	{ "cx", 8, offsetof(struct pt_regs, cx) },
  	{ "dx", 8, offsetof(struct pt_regs, dx) },
  	{ "si", 8, offsetof(struct pt_regs, si) },
  	{ "di", 8, offsetof(struct pt_regs, di) },
  	{ "bp", 8, offsetof(struct pt_regs, bp) },
  	{ "sp", 8, offsetof(struct pt_regs, sp) },
  	{ "r8", 8, offsetof(struct pt_regs, r8) },
  	{ "r9", 8, offsetof(struct pt_regs, r9) },
  	{ "r10", 8, offsetof(struct pt_regs, r10) },
  	{ "r11", 8, offsetof(struct pt_regs, r11) },
  	{ "r12", 8, offsetof(struct pt_regs, r12) },
  	{ "r13", 8, offsetof(struct pt_regs, r13) },
  	{ "r14", 8, offsetof(struct pt_regs, r14) },
  	{ "r15", 8, offsetof(struct pt_regs, r15) },
  	{ "ip", 8, offsetof(struct pt_regs, ip) },
  	{ "flags", 4, offsetof(struct pt_regs, flags) },
  	{ "cs", 4, offsetof(struct pt_regs, cs) },
  	{ "ss", 4, offsetof(struct pt_regs, ss) },
  	{ "ds", 4, -1 },
  	{ "es", 4, -1 },
  #endif
  	{ "fs", 4, -1 },
  	{ "gs", 4, -1 },
  };
  
  int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
  {
  	if (
  #ifdef CONFIG_X86_32
  	    regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
  #endif
  	    regno == GDB_SP || regno == GDB_ORIG_AX)
  		return 0;
  
  	if (dbg_reg_def[regno].offset != -1)
  		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
  		       dbg_reg_def[regno].size);
  	return 0;
  }
  
  char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
  {
  	if (regno == GDB_ORIG_AX) {
  		memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
  		return "orig_ax";
  	}
  	if (regno >= DBG_MAX_REG_NUM || regno < 0)
  		return NULL;
  
  	if (dbg_reg_def[regno].offset != -1)
  		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
  		       dbg_reg_def[regno].size);
  
  #ifdef CONFIG_X86_32
  	switch (regno) {
  	case GDB_SS:
  		if (!user_mode(regs))
  			*(unsigned long *)mem = __KERNEL_DS;
  		break;
  	case GDB_SP:
  		if (!user_mode(regs))
  			*(unsigned long *)mem = kernel_stack_pointer(regs);
  		break;
  	case GDB_GS:
  	case GDB_FS:
  		*(unsigned long *)mem = 0xFFFF;
  		break;
  	}
  #endif
  	return dbg_reg_def[regno].name;
  }
  
  /**
   *	sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
   *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
   *	@p: The &struct task_struct of the desired process.
   *
   *	Convert the register values of the sleeping process in @p to
   *	the format that GDB expects.
   *	This function is called when kgdb does not have access to the
   *	&struct pt_regs and therefore it should fill the gdb registers
   *	@gdb_regs with what has	been saved in &struct thread_struct
   *	thread field during switch_to.
   */
  void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
  {
  #ifndef CONFIG_X86_32
  	u32 *gdb_regs32 = (u32 *)gdb_regs;
  #endif
  	gdb_regs[GDB_AX]	= 0;
  	gdb_regs[GDB_BX]	= 0;
  	gdb_regs[GDB_CX]	= 0;
  	gdb_regs[GDB_DX]	= 0;
  	gdb_regs[GDB_SI]	= 0;
  	gdb_regs[GDB_DI]	= 0;
  	gdb_regs[GDB_BP]	= ((struct inactive_task_frame *)p->thread.sp)->bp;
  #ifdef CONFIG_X86_32
  	gdb_regs[GDB_DS]	= __KERNEL_DS;
  	gdb_regs[GDB_ES]	= __KERNEL_DS;
  	gdb_regs[GDB_PS]	= 0;
  	gdb_regs[GDB_CS]	= __KERNEL_CS;
  	gdb_regs[GDB_SS]	= __KERNEL_DS;
  	gdb_regs[GDB_FS]	= 0xFFFF;
  	gdb_regs[GDB_GS]	= 0xFFFF;
  #else
  	gdb_regs32[GDB_PS]	= 0;
  	gdb_regs32[GDB_CS]	= __KERNEL_CS;
  	gdb_regs32[GDB_SS]	= __KERNEL_DS;
  	gdb_regs[GDB_R8]	= 0;
  	gdb_regs[GDB_R9]	= 0;
  	gdb_regs[GDB_R10]	= 0;
  	gdb_regs[GDB_R11]	= 0;
  	gdb_regs[GDB_R12]	= 0;
  	gdb_regs[GDB_R13]	= 0;
  	gdb_regs[GDB_R14]	= 0;
  	gdb_regs[GDB_R15]	= 0;
  #endif
  	gdb_regs[GDB_PC]	= 0;
  	gdb_regs[GDB_SP]	= p->thread.sp;
  }
  
  static struct hw_breakpoint {
  	unsigned		enabled;
  	unsigned long		addr;
  	int			len;
  	int			type;
  	struct perf_event	* __percpu *pev;
  } breakinfo[HBP_NUM];
  
  static unsigned long early_dr7;
  
  static void kgdb_correct_hw_break(void)
  {
  	int breakno;
  
  	for (breakno = 0; breakno < HBP_NUM; breakno++) {
  		struct perf_event *bp;
  		struct arch_hw_breakpoint *info;
  		int val;
  		int cpu = raw_smp_processor_id();
  		if (!breakinfo[breakno].enabled)
  			continue;
  		if (dbg_is_early) {
  			set_debugreg(breakinfo[breakno].addr, breakno);
  			early_dr7 |= encode_dr7(breakno,
  						breakinfo[breakno].len,
  						breakinfo[breakno].type);
  			set_debugreg(early_dr7, 7);
  			continue;
  		}
  		bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
  		info = counter_arch_bp(bp);
  		if (bp->attr.disabled != 1)
  			continue;
  		bp->attr.bp_addr = breakinfo[breakno].addr;
  		bp->attr.bp_len = breakinfo[breakno].len;
  		bp->attr.bp_type = breakinfo[breakno].type;
  		info->address = breakinfo[breakno].addr;
  		info->len = breakinfo[breakno].len;
  		info->type = breakinfo[breakno].type;
  		val = arch_install_hw_breakpoint(bp);
  		if (!val)
  			bp->attr.disabled = 0;
  	}
  	if (!dbg_is_early)
  		hw_breakpoint_restore();
  }
  
  static int hw_break_reserve_slot(int breakno)
  {
  	int cpu;
  	int cnt = 0;
  	struct perf_event **pevent;
  
  	if (dbg_is_early)
  		return 0;
  
  	for_each_online_cpu(cpu) {
  		cnt++;
  		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
  		if (dbg_reserve_bp_slot(*pevent))
  			goto fail;
  	}
  
  	return 0;
  
  fail:
  	for_each_online_cpu(cpu) {
  		cnt--;
  		if (!cnt)
  			break;
  		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
  		dbg_release_bp_slot(*pevent);
  	}
  	return -1;
  }
  
  static int hw_break_release_slot(int breakno)
  {
  	struct perf_event **pevent;
  	int cpu;
  
  	if (dbg_is_early)
  		return 0;
  
  	for_each_online_cpu(cpu) {
  		pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
  		if (dbg_release_bp_slot(*pevent))
  			/*
  			 * The debugger is responsible for handing the retry on
  			 * remove failure.
  			 */
  			return -1;
  	}
  	return 0;
  }
  
  static int
  kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
  {
  	int i;
  
  	for (i = 0; i < HBP_NUM; i++)
  		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
  			break;
  	if (i == HBP_NUM)
  		return -1;
  
  	if (hw_break_release_slot(i)) {
  		printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
  		return -1;
  	}
  	breakinfo[i].enabled = 0;
  
  	return 0;
  }
  
  static void kgdb_remove_all_hw_break(void)
  {
  	int i;
  	int cpu = raw_smp_processor_id();
  	struct perf_event *bp;
  
  	for (i = 0; i < HBP_NUM; i++) {
  		if (!breakinfo[i].enabled)
  			continue;
  		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
  		if (!bp->attr.disabled) {
  			arch_uninstall_hw_breakpoint(bp);
  			bp->attr.disabled = 1;
  			continue;
  		}
  		if (dbg_is_early)
  			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
  						 breakinfo[i].type);
  		else if (hw_break_release_slot(i))
  			printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
  			       breakinfo[i].addr);
  		breakinfo[i].enabled = 0;
  	}
  }
  
  static int
  kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
  {
  	int i;
  
  	for (i = 0; i < HBP_NUM; i++)
  		if (!breakinfo[i].enabled)
  			break;
  	if (i == HBP_NUM)
  		return -1;
  
  	switch (bptype) {
  	case BP_HARDWARE_BREAKPOINT:
  		len = 1;
  		breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
  		break;
  	case BP_WRITE_WATCHPOINT:
  		breakinfo[i].type = X86_BREAKPOINT_WRITE;
  		break;
  	case BP_ACCESS_WATCHPOINT:
  		breakinfo[i].type = X86_BREAKPOINT_RW;
  		break;
  	default:
  		return -1;
  	}
  	switch (len) {
  	case 1:
  		breakinfo[i].len = X86_BREAKPOINT_LEN_1;
  		break;
  	case 2:
  		breakinfo[i].len = X86_BREAKPOINT_LEN_2;
  		break;
  	case 4:
  		breakinfo[i].len = X86_BREAKPOINT_LEN_4;
  		break;
  #ifdef CONFIG_X86_64
  	case 8:
  		breakinfo[i].len = X86_BREAKPOINT_LEN_8;
  		break;
  #endif
  	default:
  		return -1;
  	}
  	breakinfo[i].addr = addr;
  	if (hw_break_reserve_slot(i)) {
  		breakinfo[i].addr = 0;
  		return -1;
  	}
  	breakinfo[i].enabled = 1;
  
  	return 0;
  }
  
  /**
   *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
   *	@regs: Current &struct pt_regs.
   *
   *	This function will be called if the particular architecture must
   *	disable hardware debugging while it is processing gdb packets or
   *	handling exception.
   */
  static void kgdb_disable_hw_debug(struct pt_regs *regs)
  {
  	int i;
  	int cpu = raw_smp_processor_id();
  	struct perf_event *bp;
  
  	/* Disable hardware debugging while we are in kgdb: */
  	set_debugreg(0UL, 7);
  	for (i = 0; i < HBP_NUM; i++) {
  		if (!breakinfo[i].enabled)
  			continue;
  		if (dbg_is_early) {
  			early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
  						 breakinfo[i].type);
  			continue;
  		}
  		bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
  		if (bp->attr.disabled == 1)
  			continue;
  		arch_uninstall_hw_breakpoint(bp);
  		bp->attr.disabled = 1;
  	}
  }
  
  #ifdef CONFIG_SMP
  /**
   *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
   *
   *	On SMP systems, we need to get the attention of the other CPUs
   *	and get them be in a known state.  This should do what is needed
   *	to get the other CPUs to call kgdb_wait(). Note that on some arches,
   *	the NMI approach is not used for rounding up all the CPUs. For example,
   *	in case of MIPS, smp_call_function() is used to roundup CPUs.
   *
   *	On non-SMP systems, this is not called.
   */
  void kgdb_roundup_cpus(void)
  {
  	apic->send_IPI_allbutself(APIC_DM_NMI);
  }
  #endif
  
  /**
   *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
   *	@e_vector: The error vector of the exception that happened.
   *	@signo: The signal number of the exception that happened.
   *	@err_code: The error code of the exception that happened.
   *	@remcomInBuffer: The buffer of the packet we have read.
   *	@remcomOutBuffer: The buffer of %BUFMAX bytes to write a packet into.
   *	@linux_regs: The &struct pt_regs of the current process.
   *
   *	This function MUST handle the 'c' and 's' command packets,
   *	as well packets to set / remove a hardware breakpoint, if used.
   *	If there are additional packets which the hardware needs to handle,
   *	they are handled here.  The code should return -1 if it wants to
   *	process more packets, and a %0 or %1 if it wants to exit from the
   *	kgdb callback.
   */
  int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
  			       char *remcomInBuffer, char *remcomOutBuffer,
  			       struct pt_regs *linux_regs)
  {
  	unsigned long addr;
  	char *ptr;
  
  	switch (remcomInBuffer[0]) {
  	case 'c':
  	case 's':
  		/* try to read optional parameter, pc unchanged if no parm */
  		ptr = &remcomInBuffer[1];
  		if (kgdb_hex2long(&ptr, &addr))
  			linux_regs->ip = addr;
  		/* fall through */
  	case 'D':
  	case 'k':
  		/* clear the trace bit */
  		linux_regs->flags &= ~X86_EFLAGS_TF;
  		atomic_set(&kgdb_cpu_doing_single_step, -1);
  
  		/* set the trace bit if we're stepping */
  		if (remcomInBuffer[0] == 's') {
  			linux_regs->flags |= X86_EFLAGS_TF;
  			atomic_set(&kgdb_cpu_doing_single_step,
  				   raw_smp_processor_id());
  		}
  
  		return 0;
  	}
  
  	/* this means that we do not want to exit from the handler: */
  	return -1;
  }
  
  static inline int
  single_step_cont(struct pt_regs *regs, struct die_args *args)
  {
  	/*
  	 * Single step exception from kernel space to user space so
  	 * eat the exception and continue the process:
  	 */
  	printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
  			"resuming...\n");
  	kgdb_arch_handle_exception(args->trapnr, args->signr,
  				   args->err, "c", "", regs);
  	/*
  	 * Reset the BS bit in dr6 (pointed by args->err) to
  	 * denote completion of processing
  	 */
  	(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
  
  	return NOTIFY_STOP;
  }
  
  static DECLARE_BITMAP(was_in_debug_nmi, NR_CPUS);
  
  static int kgdb_nmi_handler(unsigned int cmd, struct pt_regs *regs)
  {
  	int cpu;
  
  	switch (cmd) {
  	case NMI_LOCAL:
  		if (atomic_read(&kgdb_active) != -1) {
  			/* KGDB CPU roundup */
  			cpu = raw_smp_processor_id();
  			kgdb_nmicallback(cpu, regs);
  			set_bit(cpu, was_in_debug_nmi);
  			touch_nmi_watchdog();
  
  			return NMI_HANDLED;
  		}
  		break;
  
  	case NMI_UNKNOWN:
  		cpu = raw_smp_processor_id();
  
  		if (__test_and_clear_bit(cpu, was_in_debug_nmi))
  			return NMI_HANDLED;
  
  		break;
  	default:
  		/* do nothing */
  		break;
  	}
  	return NMI_DONE;
  }
  
  static int __kgdb_notify(struct die_args *args, unsigned long cmd)
  {
  	struct pt_regs *regs = args->regs;
  
  	switch (cmd) {
  	case DIE_DEBUG:
  		if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
  			if (user_mode(regs))
  				return single_step_cont(regs, args);
  			break;
  		} else if (test_thread_flag(TIF_SINGLESTEP))
  			/* This means a user thread is single stepping
  			 * a system call which should be ignored
  			 */
  			return NOTIFY_DONE;
  		/* fall through */
  	default:
  		if (user_mode(regs))
  			return NOTIFY_DONE;
  	}
  
  	if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
  		return NOTIFY_DONE;
  
  	/* Must touch watchdog before return to normal operation */
  	touch_nmi_watchdog();
  	return NOTIFY_STOP;
  }
  
  int kgdb_ll_trap(int cmd, const char *str,
  		 struct pt_regs *regs, long err, int trap, int sig)
  {
  	struct die_args args = {
  		.regs	= regs,
  		.str	= str,
  		.err	= err,
  		.trapnr	= trap,
  		.signr	= sig,
  
  	};
  
  	if (!kgdb_io_module_registered)
  		return NOTIFY_DONE;
  
  	return __kgdb_notify(&args, cmd);
  }
  
  static int
  kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
  {
  	unsigned long flags;
  	int ret;
  
  	local_irq_save(flags);
  	ret = __kgdb_notify(ptr, cmd);
  	local_irq_restore(flags);
  
  	return ret;
  }
  
  static struct notifier_block kgdb_notifier = {
  	.notifier_call	= kgdb_notify,
  };
  
  /**
   *	kgdb_arch_init - Perform any architecture specific initialization.
   *
   *	This function will handle the initialization of any architecture
   *	specific callbacks.
   */
  int kgdb_arch_init(void)
  {
  	int retval;
  
  	retval = register_die_notifier(&kgdb_notifier);
  	if (retval)
  		goto out;
  
  	retval = register_nmi_handler(NMI_LOCAL, kgdb_nmi_handler,
  					0, "kgdb");
  	if (retval)
  		goto out1;
  
  	retval = register_nmi_handler(NMI_UNKNOWN, kgdb_nmi_handler,
  					0, "kgdb");
  
  	if (retval)
  		goto out2;
  
  	return retval;
  
  out2:
  	unregister_nmi_handler(NMI_LOCAL, "kgdb");
  out1:
  	unregister_die_notifier(&kgdb_notifier);
  out:
  	return retval;
  }
  
  static void kgdb_hw_overflow_handler(struct perf_event *event,
  		struct perf_sample_data *data, struct pt_regs *regs)
  {
  	struct task_struct *tsk = current;
  	int i;
  
  	for (i = 0; i < 4; i++)
  		if (breakinfo[i].enabled)
  			tsk->thread.debugreg6 |= (DR_TRAP0 << i);
  }
  
  void kgdb_arch_late(void)
  {
  	int i, cpu;
  	struct perf_event_attr attr;
  	struct perf_event **pevent;
  
  	/*
  	 * Pre-allocate the hw breakpoint structions in the non-atomic
  	 * portion of kgdb because this operation requires mutexs to
  	 * complete.
  	 */
  	hw_breakpoint_init(&attr);
  	attr.bp_addr = (unsigned long)kgdb_arch_init;
  	attr.bp_len = HW_BREAKPOINT_LEN_1;
  	attr.bp_type = HW_BREAKPOINT_W;
  	attr.disabled = 1;
  	for (i = 0; i < HBP_NUM; i++) {
  		if (breakinfo[i].pev)
  			continue;
  		breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
  		if (IS_ERR((void * __force)breakinfo[i].pev)) {
  			printk(KERN_ERR "kgdb: Could not allocate hw"
  			       "breakpoints\nDisabling the kernel debugger\n");
  			breakinfo[i].pev = NULL;
  			kgdb_arch_exit();
  			return;
  		}
  		for_each_online_cpu(cpu) {
  			pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
  			pevent[0]->hw.sample_period = 1;
  			pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
  			if (pevent[0]->destroy != NULL) {
  				pevent[0]->destroy = NULL;
  				release_bp_slot(*pevent);
  			}
  		}
  	}
  }
  
  /**
   *	kgdb_arch_exit - Perform any architecture specific uninitalization.
   *
   *	This function will handle the uninitalization of any architecture
   *	specific callbacks, for dynamic registration and unregistration.
   */
  void kgdb_arch_exit(void)
  {
  	int i;
  	for (i = 0; i < 4; i++) {
  		if (breakinfo[i].pev) {
  			unregister_wide_hw_breakpoint(breakinfo[i].pev);
  			breakinfo[i].pev = NULL;
  		}
  	}
  	unregister_nmi_handler(NMI_UNKNOWN, "kgdb");
  	unregister_nmi_handler(NMI_LOCAL, "kgdb");
  	unregister_die_notifier(&kgdb_notifier);
  }
  
  /**
   *
   *	kgdb_skipexception - Bail out of KGDB when we've been triggered.
   *	@exception: Exception vector number
   *	@regs: Current &struct pt_regs.
   *
   *	On some architectures we need to skip a breakpoint exception when
   *	it occurs after a breakpoint has been removed.
   *
   * Skip an int3 exception when it occurs after a breakpoint has been
   * removed. Backtrack eip by 1 since the int3 would have caused it to
   * increment by 1.
   */
  int kgdb_skipexception(int exception, struct pt_regs *regs)
  {
  	if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
  		regs->ip -= 1;
  		return 1;
  	}
  	return 0;
  }
  
  unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
  {
  	if (exception == 3)
  		return instruction_pointer(regs) - 1;
  	return instruction_pointer(regs);
  }
  
  void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
  {
  	regs->ip = ip;
  }
  
  int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
  {
  	int err;
  
  	bpt->type = BP_BREAKPOINT;
  	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
  				BREAK_INSTR_SIZE);
  	if (err)
  		return err;
  	err = probe_kernel_write((char *)bpt->bpt_addr,
  				 arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
  	if (!err)
  		return err;
  	/*
  	 * It is safe to call text_poke_kgdb() because normal kernel execution
  	 * is stopped on all cores, so long as the text_mutex is not locked.
  	 */
  	if (mutex_is_locked(&text_mutex))
  		return -EBUSY;
  	text_poke_kgdb((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
  		       BREAK_INSTR_SIZE);
  	bpt->type = BP_POKE_BREAKPOINT;
  
  	return 0;
  }
  
  int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
  {
  	if (bpt->type != BP_POKE_BREAKPOINT)
  		goto knl_write;
  	/*
  	 * It is safe to call text_poke_kgdb() because normal kernel execution
  	 * is stopped on all cores, so long as the text_mutex is not locked.
  	 */
  	if (mutex_is_locked(&text_mutex))
  		goto knl_write;
  	text_poke_kgdb((void *)bpt->bpt_addr, bpt->saved_instr,
  		       BREAK_INSTR_SIZE);
  	return 0;
  
  knl_write:
  	return probe_kernel_write((char *)bpt->bpt_addr,
  				  (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
  }
  
  const struct kgdb_arch arch_kgdb_ops = {
  	/* Breakpoint instruction: */
  	.gdb_bpt_instr		= { 0xcc },
  	.flags			= KGDB_HW_BREAKPOINT,
  	.set_hw_breakpoint	= kgdb_set_hw_break,
  	.remove_hw_breakpoint	= kgdb_remove_hw_break,
  	.disable_hw_break	= kgdb_disable_hw_debug,
  	.remove_all_hw_break	= kgdb_remove_all_hw_break,
  	.correct_hw_break	= kgdb_correct_hw_break,
  };
  