Message-ID: <20080210224047.GA21420@elte.hu>
Date:	Sun, 10 Feb 2008 23:40:47 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jan Kiszka <jan.kiszka@....de>
Cc:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@....com.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Wessel <jason.wessel@...driver.com>
Subject: Re: [patch] kgdb light, v6


* Jan Kiszka <jan.kiszka@....de> wrote:

> Ingo, please keep the original annotations, they where correct and 
> should have been optimal (under the given constraints or runtime 
> reconfiguration).

agreed. I've regenerated the -v7 tree with this trivial revert. Tip is 
commit 04b94b1dd5197bf737073ebbd4189ffdfdcea534, updated shortlog, 
diffstat and patch can be found below. Tree is at:

  git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-kgdb.git

	Ingo

------------------>
Ingo Molnar (3):
      pids: add pid_max prototype
      uaccess: add probe_kernel_write()
      x86: kgdb support

Jason Wessel (3):
      kgdb: core
      consoles: polling support, kgdboc
      kgdb: document parameters

 Documentation/kernel-parameters.txt |    5 +
 arch/x86/Kconfig                    |    2 +
 arch/x86/kernel/Makefile            |    1 +
 arch/x86/kernel/kgdb.c              |  654 +++++++++++++
 drivers/char/tty_io.c               |   47 +
 drivers/serial/8250.c               |   58 ++
 drivers/serial/Kconfig              |    3 +
 drivers/serial/Makefile             |    1 +
 drivers/serial/kgdboc.c             |  163 +++
 drivers/serial/serial_core.c        |   70 ++-
 include/asm-x86/kgdb.h              |   81 ++
 include/linux/kgdb.h                |  314 ++++++
 include/linux/pid.h                 |    2 +
 include/linux/serial_core.h         |    4 +
 include/linux/tty_driver.h          |   12 +
 include/linux/uaccess.h             |   22 +
 kernel/Makefile                     |    1 +
 kernel/kgdb.c                       | 1838 +++++++++++++++++++++++++++++++++++
 kernel/sysctl.c                     |    2 +-
 lib/Kconfig.debug                   |    2 +
 lib/Kconfig.kgdb                    |   40 +
 mm/Makefile                         |    2 +-
 mm/maccess.c                        |   49 +
 23 files changed, 3368 insertions(+), 5 deletions(-)
 create mode 100644 arch/x86/kernel/kgdb.c
 create mode 100644 drivers/serial/kgdboc.c
 create mode 100644 include/asm-x86/kgdb.h
 create mode 100644 include/linux/kgdb.h
 create mode 100644 kernel/kgdb.c
 create mode 100644 lib/Kconfig.kgdb
 create mode 100644 mm/maccess.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a4fc7fc..6e97307 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -930,6 +930,11 @@ and is between 256 and 4096 characters. It is defined in the file
 	kstack=N	[X86-32,X86-64] Print N words from the kernel stack
 			in oops dumps.
 
+	kgdboc=		[HW] kgdb over consoles.
+			Requires a tty driver that supports console polling.
+			(only serial suported for now)
+			Format: <serial_device>[,baud]
+
 	l2cr=		[PPC]
 
 	lapic		[X86-32,APIC] Enable the local APIC even if BIOS
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index aaed1a3..5e0fab5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -14,6 +14,7 @@ config X86_32
 
 config X86_64
 	def_bool 64BIT
+	select HAVE_ARCH_KGDB_SHADOW_INFO
 
 ### Arch settings
 config X86
@@ -21,6 +22,7 @@ config X86
 	select HAVE_IDE
 	select HAVE_OPROFILE
 	select HAVE_KPROBES
+	select HAVE_ARCH_KGDB
 
 config GENERIC_LOCKBREAK
 	def_bool n
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 76ec0f8..4cd39cd 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_MODULES)		+= module_$(BITS).o
 obj-$(CONFIG_ACPI_SRAT) 	+= srat_32.o
 obj-$(CONFIG_EFI) 		+= efi.o efi_$(BITS).o efi_stub_$(BITS).o
 obj-$(CONFIG_DOUBLEFAULT) 	+= doublefault_32.o
+obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_VM86)		+= vm86_32.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
new file mode 100644
index 0000000..51002f8
--- /dev/null
+++ b/arch/x86/kernel/kgdb.c
@@ -0,0 +1,654 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ */
+
+/*
+ * Copyright (C) 2004 Amit S. Kale <amitkale@...syssoft.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@...itas.com>
+ *  Updated by:	     Tom Rini <trini@...nel.crashing.org>
+ *  Updated by:	     Jason Wessel <jason.wessel@...driver.com>
+ *  Modified for 386 by Jim Kingdon, Cygnus Support.
+ *  Origianl kgdb, compatibility with 2.1.xx kernel by
+ *  David Grothe <dave@...m.com>
+ *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@....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/init.h>
+#include <linux/smp.h>
+
+#include <asm/apicdef.h>
+#include <asm/system.h>
+
+#ifdef CONFIG_X86_32
+# include <mach_ipi.h>
+#else
+# include <asm/mach_apic.h>
+#endif
+
+/*
+ * Put the error code here just in case the user cares:
+ */
+static int gdb_x86errcode;
+
+/*
+ * Likewise, the vector number here (since GDB only gets the signal
+ * number through the usual means, and that's not very specific):
+ */
+static int gdb_x86vector = -1;
+
+/**
+ *	pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
+ *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
+ *	@regs: The &struct pt_regs of the current process.
+ *
+ *	Convert the pt_regs in @regs into the format for registers that
+ *	GDB expects, stored in @gdb_regs.
+ */
+void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+	gdb_regs[GDB_AX]	= regs->ax;
+	gdb_regs[GDB_BX]	= regs->bx;
+	gdb_regs[GDB_CX]	= regs->cx;
+	gdb_regs[GDB_DX]	= regs->dx;
+	gdb_regs[GDB_SI]	= regs->si;
+	gdb_regs[GDB_DI]	= regs->di;
+	gdb_regs[GDB_BP]	= regs->bp;
+	gdb_regs[GDB_PS]	= regs->flags;
+	gdb_regs[GDB_PC]	= regs->ip;
+#ifdef CONFIG_X86_32
+	gdb_regs[GDB_DS]	= regs->ds;
+	gdb_regs[GDB_ES]	= regs->es;
+	gdb_regs[GDB_CS]	= regs->cs;
+	gdb_regs[GDB_SS]	= __KERNEL_DS;
+	gdb_regs[GDB_FS]	= 0xFFFF;
+	gdb_regs[GDB_GS]	= 0xFFFF;
+#else
+	gdb_regs[GDB_R8]	= regs->r8;
+	gdb_regs[GDB_R9]	= regs->r9;
+	gdb_regs[GDB_R10]	= regs->r10;
+	gdb_regs[GDB_R11]	= regs->r11;
+	gdb_regs[GDB_R12]	= regs->r12;
+	gdb_regs[GDB_R13]	= regs->r13;
+	gdb_regs[GDB_R14]	= regs->r14;
+	gdb_regs[GDB_R15]	= regs->r15;
+#endif
+	gdb_regs[GDB_SP]	= regs->sp;
+}
+
+/**
+ *	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)
+{
+	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]	= *(unsigned long *)p->thread.sp;
+#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_PC]	= p->thread.ip;
+	gdb_regs[GDB_SS]	= __KERNEL_DS;
+	gdb_regs[GDB_FS]	= 0xFFFF;
+	gdb_regs[GDB_GS]	= 0xFFFF;
+#else
+	gdb_regs[GDB_PS]	= *(unsigned long *)(p->thread.sp + 8);
+	gdb_regs[GDB_PC]	= 0;
+	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_SP]	= p->thread.sp;
+}
+
+/**
+ *	gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
+ *	@gdb_regs: A pointer to hold the registers we've received from GDB.
+ *	@regs: A pointer to a &struct pt_regs to hold these values in.
+ *
+ *	Convert the GDB regs in @gdb_regs into the pt_regs, and store them
+ *	in @regs.
+ */
+void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+	regs->ax		= gdb_regs[GDB_AX];
+	regs->bx		= gdb_regs[GDB_BX];
+	regs->cx		= gdb_regs[GDB_CX];
+	regs->dx		= gdb_regs[GDB_DX];
+	regs->si		= gdb_regs[GDB_SI];
+	regs->di		= gdb_regs[GDB_DI];
+	regs->bp		= gdb_regs[GDB_BP];
+	regs->flags		= gdb_regs[GDB_PS];
+	regs->ip		= gdb_regs[GDB_PC];
+#ifdef CONFIG_X86_32
+	regs->ds		= gdb_regs[GDB_DS];
+	regs->es		= gdb_regs[GDB_ES];
+	regs->cs		= gdb_regs[GDB_CS];
+#else
+	regs->r8		= gdb_regs[GDB_R8];
+	regs->r9		= gdb_regs[GDB_R9];
+	regs->r10		= gdb_regs[GDB_R10];
+	regs->r11		= gdb_regs[GDB_R11];
+	regs->r12		= gdb_regs[GDB_R12];
+	regs->r13		= gdb_regs[GDB_R13];
+	regs->r14		= gdb_regs[GDB_R14];
+	regs->r15		= gdb_regs[GDB_R15];
+#endif
+}
+
+static struct hw_breakpoint {
+	unsigned		enabled;
+	unsigned		type;
+	unsigned		len;
+	unsigned long		addr;
+} breakinfo[4];
+
+static void kgdb_correct_hw_break(void)
+{
+	unsigned long dr7;
+	int correctit = 0;
+	int breakbit;
+	int breakno;
+
+	get_debugreg(dr7, 7);
+	for (breakno = 0; breakno < 4; breakno++) {
+		breakbit = 2 << (breakno << 1);
+		if (!(dr7 & breakbit) && breakinfo[breakno].enabled) {
+			correctit = 1;
+			dr7 |= breakbit;
+			dr7 &= ~(0xf0000 << (breakno << 2));
+			dr7 |= ((breakinfo[breakno].len << 2) |
+				 breakinfo[breakno].type) <<
+			       ((breakno << 2) + 16);
+			if (breakno >= 0 && breakno <= 3)
+				set_debugreg(breakinfo[breakno].addr, breakno);
+
+		} else {
+			if ((dr7 & breakbit) && !breakinfo[breakno].enabled) {
+				correctit = 1;
+				dr7 &= ~breakbit;
+				dr7 &= ~(0xf0000 << (breakno << 2));
+			}
+		}
+	}
+	if (correctit)
+		set_debugreg(dr7, 7);
+}
+
+static int
+kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
+{
+	int i;
+
+	for (i = 0; i < 4; i++)
+		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
+			break;
+	if (i == 4)
+		return -1;
+
+	breakinfo[i].enabled = 0;
+
+	return 0;
+}
+
+static void kgdb_remove_all_hw_break(void)
+{
+	int i;
+
+	for (i = 0; i < 4; i++)
+		memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint));
+}
+
+static int
+kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
+{
+	unsigned type;
+	int i;
+
+	for (i = 0; i < 4; i++)
+		if (!breakinfo[i].enabled)
+			break;
+	if (i == 4)
+		return -1;
+
+	switch (bptype) {
+	case BP_HARDWARE_BREAKPOINT:
+		type = 0;
+		len  = 1;
+		break;
+	case BP_WRITE_WATCHPOINT:
+		type = 1;
+		break;
+	case BP_ACCESS_WATCHPOINT:
+		type = 3;
+		break;
+	default:
+		return -1;
+	}
+
+	if (len == 1 || len == 2 || len == 4)
+		breakinfo[i].len  = len - 1;
+	else
+		return -1;
+
+	breakinfo[i].enabled = 1;
+	breakinfo[i].addr = addr;
+	breakinfo[i].type = type;
+
+	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.
+ */
+void kgdb_disable_hw_debug(struct pt_regs *regs)
+{
+	/* Disable hardware debugging while we are in kgdb: */
+	set_debugreg(0UL, 7);
+}
+
+/**
+ *	kgdb_post_master_code - Save error vector/code numbers.
+ *	@regs: Original pt_regs.
+ *	@e_vector: Original error vector.
+ *	@err_code: Original error code.
+ *
+ *	This is needed on architectures which support SMP and KGDB.
+ *	This function is called after all the slave cpus have been put
+ *	to a know spin state and the master CPU has control over KGDB.
+ */
+void kgdb_post_master_code(struct pt_regs *regs, int e_vector, int err_code)
+{
+	/* Master processor is completely in the debugger */
+	gdb_x86vector = e_vector;
+	gdb_x86errcode = err_code;
+}
+
+#ifdef CONFIG_SMP
+/**
+ *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
+ *	@flags: Current IRQ state
+ *
+ *	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. In
+ *	this case, we have to make sure that interrupts are enabled before
+ *	calling smp_call_function(). The argument to this function is
+ *	the flags that will be used when restoring the interrupts. There is
+ *	local_irq_save() call before kgdb_roundup_cpus().
+ *
+ *	On non-SMP systems, this is not called.
+ */
+void kgdb_roundup_cpus(unsigned long flags)
+{
+	send_IPI_allbutself(APIC_DM_NMI);
+}
+#endif
+
+/**
+ *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
+ *	@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.
+ *	@remcom_in_buffer: The buffer of the packet we have read.
+ *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
+ *	@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;
+	unsigned long dr6;
+	char *ptr;
+	int newPC;
+
+	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;
+		newPC = linux_regs->ip;
+
+		/* clear the trace bit */
+		linux_regs->flags &= ~TF_MASK;
+		atomic_set(&kgdb_cpu_doing_single_step, -1);
+
+		/* set the trace bit if we're stepping */
+		if (remcomInBuffer[0] == 's') {
+			linux_regs->flags |= TF_MASK;
+			kgdb_single_step = 1;
+			if (kgdb_contthread) {
+				atomic_set(&kgdb_cpu_doing_single_step,
+					   raw_smp_processor_id());
+			}
+		}
+
+		get_debugreg(dr6, 6);
+		if (!(dr6 & 0x4000)) {
+			int breakno;
+
+			for (breakno = 0; breakno < 4; breakno++) {
+				if (dr6 & (1 << breakno) &&
+				    breakinfo[breakno].type == 0) {
+					/* Set restore flag: */
+					linux_regs->flags |= X86_EFLAGS_RF;
+					break;
+				}
+			}
+		}
+		set_debugreg(0UL, 6);
+		kgdb_correct_hw_break();
+
+		return 0;
+	}
+
+	/* this means that we do not want to exit from the handler: */
+	return -1;
+}
+
+#ifdef CONFIG_X86_64
+
+static struct pt_regs *in_interrupt_stack(unsigned long rsp, int cpu)
+{
+	struct pt_regs *regs = NULL;
+	unsigned long end = (unsigned long)cpu_pda(cpu)->irqstackptr;
+
+	if (rsp <= end && rsp >= end - IRQSTACKSIZE + 8)
+		regs = *(((struct pt_regs **)end) - 1);
+
+	return regs;
+}
+
+static struct pt_regs *in_exception_stack(unsigned long rsp, int cpu)
+{
+	struct tss_struct *init_tss = &__get_cpu_var(init_tss);
+	struct pt_regs *regs;
+	int i;
+
+	for (i = 0; i < N_EXCEPTION_STACKS; i++)
+		if (rsp >= init_tss[cpu].x86_tss.ist[i] &&
+		    rsp <= init_tss[cpu].x86_tss.ist[i] + EXCEPTION_STKSZ) {
+			regs = (void *) init_tss[cpu].x86_tss.ist[i] +\
+				EXCEPTION_STKSZ;
+			return regs - 1;
+		}
+
+	return NULL;
+}
+
+/**
+ *	kgdb_shadowinfo - Get shadowed information on @threadid.
+ *	@regs: The &struct pt_regs of the current process.
+ *	@buffer: A buffer of %BUFMAX size.
+ *	@threadid: The thread id of the shadowed process to get information on.
+ */
+void kgdb_shadowinfo(struct pt_regs *regs, char *buffer, unsigned threadid)
+{
+	static char intr_desc[] = "Stack at interrupt entrypoint";
+	static char exc_desc[] = "Stack at exception entrypoint";
+	int cpu = raw_smp_processor_id();
+	struct pt_regs *stregs;
+
+	stregs = in_interrupt_stack(regs->sp, cpu);
+	if (stregs) {
+		kgdb_mem2hex(intr_desc, buffer, strlen(intr_desc));
+	} else {
+		stregs = in_exception_stack(regs->sp, cpu);
+		if (stregs)
+			kgdb_mem2hex(exc_desc, buffer, strlen(exc_desc));
+	}
+}
+
+/**
+ *	kgdb_get_shadow_thread - Get the shadowed &task_struct of @threadid.
+ *	@regs: The &struct pt_regs of the current thread.
+ *	@threadid: The thread id of the shadowed process to get information on.
+ *
+ *	RETURN:
+ *	This returns a pointer to the &struct task_struct of the shadowed
+ *	thread, @threadid.
+ */
+struct task_struct *kgdb_get_shadow_thread(struct pt_regs *regs, int threadid)
+{
+	int cpu = raw_smp_processor_id();
+	struct pt_regs *stregs;
+
+	stregs = in_interrupt_stack(regs->sp, cpu);
+	if (stregs) {
+		return current;
+	} else {
+		stregs = in_exception_stack(regs->sp, cpu);
+		if (stregs)
+			return current;
+	}
+
+	return NULL;
+}
+
+/**
+ *	kgdb_shadow_regs - Return the shadowed registers of @threadid.
+ *	@regs: The &struct pt_regs of the current thread.
+ *	@threadid: The thread id we want the &struct pt_regs for.
+ *
+ *	RETURN:
+ *	The a pointer to the &struct pt_regs of the shadowed thread @threadid.
+ */
+struct pt_regs *kgdb_shadow_regs(struct pt_regs *regs, int threadid)
+{
+	int cpu = raw_smp_processor_id();
+	struct pt_regs *stregs;
+
+	stregs = in_interrupt_stack(regs->sp, cpu);
+	if (stregs) {
+		return stregs;
+	} else {
+		stregs = in_exception_stack(regs->sp, cpu);
+		if (stregs)
+			return stregs;
+	}
+
+	return NULL;
+}
+
+#endif /* CONFIG_X86_64 */
+
+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);
+
+	return NOTIFY_STOP;
+}
+
+static int
+kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
+{
+	struct die_args *args = ptr;
+	struct pt_regs *regs = args->regs;
+
+	switch (cmd) {
+	case DIE_NMI:
+		if (atomic_read(&kgdb_active)) {
+			/* KGDB CPU roundup */
+			kgdb_nmicallback(raw_smp_processor_id(), regs);
+			return NOTIFY_STOP;
+		}
+		return NOTIFY_DONE;
+
+	case DIE_NMI_IPI:
+		if (atomic_read(&kgdb_active)) {
+			/* KGDB CPU roundup: */
+			if (kgdb_nmicallback(raw_smp_processor_id(), regs))
+				return NOTIFY_DONE;
+			return NOTIFY_STOP;
+		}
+		return NOTIFY_DONE;
+
+	case DIE_NMIWATCHDOG:
+		if (atomic_read(&kgdb_active)) {
+			/* KGDB CPU roundup: */
+			kgdb_nmicallback(raw_smp_processor_id(), regs);
+			return NOTIFY_STOP;
+		}
+		/* Enter debugger: */
+		break;
+
+	case DIE_DEBUG:
+		if (atomic_read(&kgdb_cpu_doing_single_step) ==
+			raw_smp_processor_id() &&
+			user_mode(regs))
+			return single_step_cont(regs, args);
+		/* fall through */
+	default:
+		if (user_mode(regs))
+			return NOTIFY_DONE;
+	}
+
+	if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
+		return NOTIFY_DONE;
+
+	return NOTIFY_STOP;
+}
+
+static struct notifier_block kgdb_notifier = {
+	.notifier_call	= kgdb_notify,
+
+	/*
+	 * Lowest-prio notifier priority, we want to be notified last:
+	 */
+	.priority	= -INT_MAX,
+};
+
+/**
+ *	kgdb_arch_init - Perform any architecture specific initalization.
+ *
+ *	This function will handle the initalization of any architecture
+ *	specific callbacks.
+ */
+int kgdb_arch_init(void)
+{
+	return register_die_notifier(&kgdb_notifier);
+}
+
+
+/**
+ *	kgdb_arch_uninit - Perform any architecture specific uninitalization.
+ *
+ *	This function will handle the uninitalization of any architecture
+ *	specific callbacks, for dynamic registration and unregistration.
+ */
+void kgdb_arch_uninit(void)
+{
+	unregister_die_notifier(&kgdb_notifier);
+}
+
+/**
+ *
+ *	kgdb_skipexception - Bail of 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);
+}
+
+struct kgdb_arch arch_kgdb_ops = {
+	/* Breakpoint instruction: */
+	.gdb_bpt_instr		= { 0xcc },
+	.flags			= KGDB_HW_BREAKPOINT,
+#ifndef CONFIG_X86_32
+	.shadowth		= 1,
+#endif
+	.set_hw_breakpoint	= kgdb_set_hw_break,
+	.remove_hw_breakpoint	= kgdb_remove_hw_break,
+	.remove_all_hw_break	= kgdb_remove_all_hw_break,
+	.correct_hw_break	= kgdb_correct_hw_break,
+};
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 613ec81..4d3c701 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1155,6 +1155,48 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
 	return NULL;
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+
+/**
+ *	tty_find_polling_driver	-	find device of a polled tty
+ *	@name: name string to match
+ *	@line: pointer to resulting tty line nr
+ *
+ *	This routine returns a tty driver structure, given a name
+ *	and the condition that the tty driver is capable of polled
+ *	operation.
+ */
+struct tty_driver *tty_find_polling_driver(char *name, int *line)
+{
+	struct tty_driver *p, *res = NULL;
+	int tty_line = 0;
+	char *str;
+
+	mutex_lock(&tty_mutex);
+	/* Search through the tty devices to look for a match */
+	list_for_each_entry(p, &tty_drivers, tty_drivers) {
+		str = name + strlen(p->name);
+		tty_line = simple_strtoul(str, &str, 10);
+		if (*str == ',')
+			str++;
+		if (*str == '\0')
+			str = 0;
+
+		if (tty_line >= 0 && tty_line <= p->num && p->poll_init &&
+				!p->poll_init(p, tty_line, str)) {
+
+			res = p;
+			*line = tty_line;
+			break;
+		}
+	}
+	mutex_unlock(&tty_mutex);
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(tty_find_polling_driver);
+#endif
+
 /**
  *	tty_check_change	-	check for POSIX terminal changes
  *	@tty: tty to check
@@ -3850,6 +3892,11 @@ void tty_set_operations(struct tty_driver *driver,
 	driver->write_proc = op->write_proc;
 	driver->tiocmget = op->tiocmget;
 	driver->tiocmset = op->tiocmset;
+#ifdef CONFIG_CONSOLE_POLL
+	driver->poll_init = op->poll_init;
+	driver->poll_get_char = op->poll_get_char;
+	driver->poll_put_char = op->poll_put_char;
+#endif
 }
 
 
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 77f7a7f..96a585e 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -1740,6 +1740,60 @@ static inline void wait_for_xmitr(struct uart_8250_port *up, int bits)
 	}
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+/*
+ * Console polling routines for writing and reading from the uart while
+ * in an interrupt or debug context.
+ */
+
+static int serial8250_get_poll_char(struct uart_port *port)
+{
+	struct uart_8250_port *up = (struct uart_8250_port *)port;
+	unsigned char lsr = serial_inp(up, UART_LSR);
+
+	while (!(lsr & UART_LSR_DR))
+		lsr = serial_inp(up, UART_LSR);
+
+	return serial_inp(up, UART_RX);
+}
+
+
+static void serial8250_put_poll_char(struct uart_port *port,
+			 unsigned char c)
+{
+	unsigned int ier;
+	struct uart_8250_port *up = (struct uart_8250_port *)port;
+
+	/*
+	 *	First save the IER then disable the interrupts
+	 */
+	ier = serial_in(up, UART_IER);
+	if (up->capabilities & UART_CAP_UUE)
+		serial_out(up, UART_IER, UART_IER_UUE);
+	else
+		serial_out(up, UART_IER, 0);
+
+	wait_for_xmitr(up, BOTH_EMPTY);
+	/*
+	 *	Send the character out.
+	 *	If a LF, also do CR...
+	 */
+	serial_out(up, UART_TX, c);
+	if (c == 10) {
+		wait_for_xmitr(up, BOTH_EMPTY);
+		serial_out(up, UART_TX, 13);
+	}
+
+	/*
+	 *	Finally, wait for transmitter to become empty
+	 *	and restore the IER
+	 */
+	wait_for_xmitr(up, BOTH_EMPTY);
+	serial_out(up, UART_IER, ier);
+}
+
+#endif /* CONFIG_CONSOLE_POLL */
+
 static int serial8250_startup(struct uart_port *port)
 {
 	struct uart_8250_port *up = (struct uart_8250_port *)port;
@@ -2386,6 +2440,10 @@ static struct uart_ops serial8250_pops = {
 	.request_port	= serial8250_request_port,
 	.config_port	= serial8250_config_port,
 	.verify_port	= serial8250_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_get_char = serial8250_get_poll_char,
+	.poll_put_char = serial8250_put_poll_char,
+#endif
 };
 
 static struct uart_8250_port serial8250_ports[UART_NR];
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index b82595c..5d9667c 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -961,6 +961,9 @@ config SERIAL_CORE
 config SERIAL_CORE_CONSOLE
 	bool
 
+config CONSOLE_POLL
+	bool
+
 config SERIAL_68328
 	bool "68328 serial support"
 	depends on M68328 || M68EZ328 || M68VZ328
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 640cfe4..3cbea54 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -66,4 +66,5 @@ obj-$(CONFIG_SERIAL_UARTLITE) += uartlite.o
 obj-$(CONFIG_SERIAL_NETX) += netx-serial.o
 obj-$(CONFIG_SERIAL_OF_PLATFORM) += of_serial.o
 obj-$(CONFIG_SERIAL_KS8695) += serial_ks8695.o
+obj-$(CONFIG_KGDB_SERIAL_CONSOLE) += kgdboc.o
 obj-$(CONFIG_SERIAL_QE) += ucc_uart.o
diff --git a/drivers/serial/kgdboc.c b/drivers/serial/kgdboc.c
new file mode 100644
index 0000000..3418307
--- /dev/null
+++ b/drivers/serial/kgdboc.c
@@ -0,0 +1,163 @@
+/*
+ * Based on the same principle as kgdboe using the NETPOLL api, this
+ * driver uses a console polling api to implement a gdb serial inteface
+ * which is multiplexed on a console port.
+ *
+ * Maintainer: Jason Wessel <jason.wessel@...driver.com>
+ *
+ * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/kgdb.h>
+#include <linux/tty.h>
+
+#define MAX_CONFIG_LEN		40
+
+static struct kgdb_io		kgdboc_io_ops;
+
+/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
+static int configured		= -1;
+
+static char config[MAX_CONFIG_LEN];
+static struct kparam_string kps = {
+	.string			= config,
+	.maxlen			= MAX_CONFIG_LEN,
+};
+
+static struct tty_driver	*kgdb_tty_driver;
+static int			kgdb_tty_line;
+
+static int kgdboc_option_setup(char *opt)
+{
+	if (strlen(opt) > MAX_CONFIG_LEN) {
+		printk(KERN_ERR "kgdboc: config string too long\n");
+		return -ENOSPC;
+	}
+	strcpy(config, opt);
+
+	return 0;
+}
+
+__setup("kgdboc=", kgdboc_option_setup);
+
+static int configure_kgdboc(void)
+{
+	struct tty_driver *p;
+	int tty_line = 0;
+	int err;
+
+	err = kgdboc_option_setup(config);
+	if (err || !strlen(config) || isspace(config[0]))
+		goto noconfig;
+
+	err = -ENODEV;
+
+	p = tty_find_polling_driver(config, &tty_line);
+	if (!p)
+		goto noconfig;
+
+	kgdb_tty_driver = p;
+	kgdb_tty_line = tty_line;
+
+	err = kgdb_register_io_module(&kgdboc_io_ops);
+	if (err)
+		goto noconfig;
+
+	configured = 1;
+
+	return 0;
+
+noconfig:
+	config[0] = 0;
+	configured = 0;
+
+	return err;
+}
+
+static int __init init_kgdboc(void)
+{
+	/* Already configured? */
+	if (configured == 1)
+		return 0;
+
+	return configure_kgdboc();
+}
+
+static void cleanup_kgdboc(void)
+{
+	if (configured == 1)
+		kgdb_unregister_io_module(&kgdboc_io_ops);
+}
+
+static int kgdboc_get_char(void)
+{
+	return kgdb_tty_driver->poll_get_char(kgdb_tty_driver, kgdb_tty_line);
+}
+
+static void kgdboc_put_char(u8 chr)
+{
+	kgdb_tty_driver->poll_put_char(kgdb_tty_driver, kgdb_tty_line, chr);
+}
+
+static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
+{
+	if (strlen(kmessage) >= MAX_CONFIG_LEN) {
+		printk(KERN_ERR "kgdboc: config string too long\n");
+		return -ENOSPC;
+	}
+
+	/* Only copy in the string if the init function has not run yet */
+	if (configured < 0) {
+		strcpy(config, kmessage);
+		return 0;
+	}
+
+	if (kgdb_connected) {
+		printk(KERN_ERR
+		       "kgdboc: Cannot reconfigure while KGDB is connected.\n");
+
+		return -EBUSY;
+	}
+
+	strcpy(config, kmessage);
+
+	if (configured == 1)
+		cleanup_kgdboc();
+
+	/* Go and configure with the new params. */
+	return configure_kgdboc();
+}
+
+static void kgdboc_pre_exp_handler(void)
+{
+	/* Increment the module count when the debugger is active */
+	if (!kgdb_connected)
+		try_module_get(THIS_MODULE);
+}
+
+static void kgdboc_post_exp_handler(void)
+{
+	/* decrement the module count when the debugger detaches */
+	if (!kgdb_connected)
+		module_put(THIS_MODULE);
+}
+
+static struct kgdb_io kgdboc_io_ops = {
+	.name			= "kgdboc",
+	.read_char		= kgdboc_get_char,
+	.write_char		= kgdboc_put_char,
+	.pre_exception		= kgdboc_pre_exp_handler,
+	.post_exception		= kgdboc_post_exp_handler,
+};
+
+module_init(init_kgdboc);
+module_exit(cleanup_kgdboc);
+module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
+MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
+MODULE_DESCRIPTION("KGDB Console TTY Driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 0f5a179..cec193b 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1827,7 +1827,7 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
  *	options.  The format of the string is <baud><parity><bits><flow>,
  *	eg: 115200n8r
  */
-void __init
+void
 uart_parse_options(char *options, int *baud, int *parity, int *bits, int *flow)
 {
 	char *s = options;
@@ -1872,7 +1872,7 @@ static const struct baud_rates baud_rates[] = {
  *	@bits: number of data bits
  *	@flow: flow control character - 'r' (rts)
  */
-int __init
+int
 uart_set_options(struct uart_port *port, struct console *co,
 		 int baud, int parity, int bits, int flow)
 {
@@ -1924,7 +1924,12 @@ uart_set_options(struct uart_port *port, struct console *co,
 	port->mctrl |= TIOCM_DTR;
 
 	port->ops->set_termios(port, &termios, &dummy);
-	co->cflag = termios.c_cflag;
+	/*
+	 * Allow the setting of the UART parameters with a NULL console
+	 * too:
+	 */
+	if (co)
+		co->cflag = termios.c_cflag;
 
 	return 0;
 }
@@ -2182,6 +2187,60 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 	}
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+
+static int uart_poll_init(struct tty_driver *driver, int line, char *options)
+{
+	struct uart_driver *drv = driver->driver_state;
+	struct uart_state *state = drv->state + line;
+	struct uart_port *port;
+	int baud = 9600;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (!state || !state->port)
+		return -1;
+
+	port = state->port;
+	if (!(port->ops->poll_get_char && port->ops->poll_put_char))
+		return -1;
+
+	if (options) {
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+		return uart_set_options(port, NULL, baud, parity, bits, flow);
+	}
+
+	return 0;
+}
+
+static int uart_poll_get_char(struct tty_driver *driver, int line)
+{
+	struct uart_driver *drv = driver->driver_state;
+	struct uart_state *state = drv->state + line;
+	struct uart_port *port;
+
+	if (!state || !state->port)
+		return -1;
+
+	port = state->port;
+	return port->ops->poll_get_char(port);
+}
+
+static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
+{
+	struct uart_driver *drv = driver->driver_state;
+	struct uart_state *state = drv->state + line;
+	struct uart_port *port;
+
+	if (!state || !state->port)
+		return;
+
+	port = state->port;
+	port->ops->poll_put_char(port, ch);
+}
+#endif
+
 static const struct tty_operations uart_ops = {
 	.open		= uart_open,
 	.close		= uart_close,
@@ -2206,6 +2265,11 @@ static const struct tty_operations uart_ops = {
 #endif
 	.tiocmget	= uart_tiocmget,
 	.tiocmset	= uart_tiocmset,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_init	= uart_poll_init,
+	.poll_get_char	= uart_poll_get_char,
+	.poll_put_char	= uart_poll_put_char,
+#endif
 };
 
 /**
diff --git a/include/asm-x86/kgdb.h b/include/asm-x86/kgdb.h
new file mode 100644
index 0000000..484c475
--- /dev/null
+++ b/include/asm-x86/kgdb.h
@@ -0,0 +1,81 @@
+#ifndef _ASM_KGDB_H_
+#define _ASM_KGDB_H_
+
+/*
+ * Copyright (C) 2001-2004 Amit S. Kale
+ * Copyright (C) 2008 Wind River Systems, Inc.
+ */
+
+/*
+ * BUFMAX defines the maximum number of characters in inbound/outbound
+ * buffers at least NUMREGBYTES*2 are needed for register packets
+ * Longer buffer is needed to list all threads
+ */
+#define BUFMAX			1024
+
+/*
+ *  Note that this register image is in a different order than
+ *  the register image that Linux produces at interrupt time.
+ *
+ *  Linux's register image is defined by struct pt_regs in ptrace.h.
+ *  Just why GDB uses a different order is a historical mystery.
+ */
+#ifdef CONFIG_X86_32
+enum regnames {
+	GDB_AX,			/* 0 */
+	GDB_CX,			/* 1 */
+	GDB_DX,			/* 2 */
+	GDB_BX,			/* 3 */
+	GDB_SP,			/* 4 */
+	GDB_BP,			/* 5 */
+	GDB_SI,			/* 6 */
+	GDB_DI,			/* 7 */
+	GDB_PC,			/* 8 also known as eip */
+	GDB_PS,			/* 9 also known as eflags */
+	GDB_CS,			/* 10 */
+	GDB_SS,			/* 11 */
+	GDB_DS,			/* 12 */
+	GDB_ES,			/* 13 */
+	GDB_FS,			/* 14 */
+	GDB_GS,			/* 15 */
+};
+#else /* ! CONFIG_X86_32 */
+enum regnames {
+	GDB_AX,			/* 0 */
+	GDB_DX,			/* 1 */
+	GDB_CX,			/* 2 */
+	GDB_BX,			/* 3 */
+	GDB_SI,			/* 4 */
+	GDB_DI,			/* 5 */
+	GDB_BP,			/* 6 */
+	GDB_SP,			/* 7 */
+	GDB_R8,			/* 8 */
+	GDB_R9,			/* 9 */
+	GDB_R10,		/* 10 */
+	GDB_R11,		/* 11 */
+	GDB_R12,		/* 12 */
+	GDB_R13,		/* 13 */
+	GDB_R14,		/* 14 */
+	GDB_R15,		/* 15 */
+	GDB_PC,			/* 16 */
+	GDB_PS,			/* 17 */
+};
+#endif /* CONFIG_X86_32 */
+
+/*
+ * Number of bytes of registers:
+ */
+#ifdef CONFIG_X86_32
+# define NUMREGBYTES		64
+#else
+# define NUMREGBYTES		((GDB_PS+1)*8)
+#endif
+
+static inline void arch_kgdb_breakpoint(void)
+{
+	asm("   int $3");
+}
+#define BREAK_INSTR_SIZE	1
+#define CACHE_FLUSH_IS_SAFE	1
+
+#endif				/* _ASM_KGDB_H_ */
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
new file mode 100644
index 0000000..67a40b9
--- /dev/null
+++ b/include/linux/kgdb.h
@@ -0,0 +1,314 @@
+/*
+ * This provides the callbacks and functions that KGDB needs to share between
+ * the core, I/O and arch-specific portions.
+ *
+ * Author: Amit Kale <amitkale@...syssoft.com> and
+ *         Tom Rini <trini@...nel.crashing.org>
+ *
+ * 2001-2004 (c) Amit S. Kale and 2003-2005 (c) MontaVista Software, Inc.
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+#ifndef _KGDB_H_
+#define _KGDB_H_
+
+#include <linux/serial_8250.h>
+#include <linux/linkage.h>
+#include <linux/init.h>
+
+#include <asm/atomic.h>
+#include <asm/kgdb.h>
+
+struct pt_regs;
+
+/*
+ *	kgdb_skipexception - Bail of 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.
+ */
+extern int kgdb_skipexception(int exception, struct pt_regs *regs);
+
+/*
+ *	kgdb_post_master_code - Save error vector/code numbers.
+ *	@regs: Original pt_regs.
+ *	@e_vector: Original error vector.
+ *	@err_code: Original error code.
+ *
+ *	This is needed on architectures which support SMP and KGDB.
+ *	This function is called after all the slave cpus have been put
+ *	to a know spin state and the master CPU has control over KGDB.
+ */
+extern void kgdb_post_master_code(struct pt_regs *regs, int e_vector,
+				  int err_code);
+
+/*
+ *	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.
+ */
+extern void kgdb_disable_hw_debug(struct pt_regs *regs);
+
+#ifdef CONFIG_HAVE_ARCH_KGDB_SHADOW_INFO
+/*
+ *	kgdb_shadowinfo - Get shadowed information on @threadid.
+ *	@regs: The &struct pt_regs of the current process.
+ *	@buffer: A buffer of %BUFMAX size.
+ *	@threadid: The thread id of the shadowed process to get information on.
+ */
+extern void kgdb_shadowinfo(struct pt_regs *regs, char *buffer,
+			    unsigned threadid);
+
+/*
+ *	kgdb_get_shadow_thread - Get the shadowed &task_struct of @threadid.
+ *	@regs: The &struct pt_regs of the current thread.
+ *	@threadid: The thread id of the shadowed process to get information on.
+ *
+ *	RETURN:
+ *	This returns a pointer to the &struct task_struct of the shadowed
+ *	thread, @threadid.
+ */
+extern struct task_struct *kgdb_get_shadow_thread(struct pt_regs *regs,
+						  int threadid);
+
+/*
+ *	kgdb_shadow_regs - Return the shadowed registers of @threadid.
+ *	@regs: The &struct pt_regs of the current thread.
+ *	@threadid: The thread id we want the &struct pt_regs for.
+ *
+ *	RETURN:
+ *	The a pointer to the &struct pt_regs of the shadowed thread @threadid.
+ */
+extern struct pt_regs *kgdb_shadow_regs(struct pt_regs *regs, int threadid);
+#else
+#define kgdb_shadowinfo(regs, buf, threadid)		do { } while (0)
+#define kgdb_get_shadow_thread(regs, threadid)		NULL
+#define kgdb_shadow_regs(regs, threadid)		NULL
+#endif
+
+struct tasklet_struct;
+struct task_struct;
+struct uart_port;
+
+/* To enter the debugger explicitly. */
+void kgdb_breakpoint(void);
+
+extern int kgdb_connected;
+
+extern atomic_t			kgdb_setting_breakpoint;
+extern atomic_t			kgdb_cpu_doing_single_step;
+
+extern struct task_struct	*kgdb_usethread;
+extern struct task_struct	*kgdb_contthread;
+
+enum kgdb_bptype {
+	BP_BREAKPOINT = 0,
+	BP_HARDWARE_BREAKPOINT,
+	BP_WRITE_WATCHPOINT,
+	BP_READ_WATCHPOINT,
+	BP_ACCESS_WATCHPOINT
+};
+
+enum kgdb_bpstate {
+	BP_UNDEFINED = 0,
+	BP_REMOVED,
+	BP_SET,
+	BP_ACTIVE
+};
+
+struct kgdb_bkpt {
+	unsigned long		bpt_addr;
+	unsigned char		saved_instr[BREAK_INSTR_SIZE];
+	enum kgdb_bptype	type;
+	enum kgdb_bpstate	state;
+};
+
+#ifndef KGDB_MAX_BREAKPOINTS
+# define KGDB_MAX_BREAKPOINTS	1000
+#endif
+
+#define KGDB_HW_BREAKPOINT	1
+
+/*
+ * Functions each KGDB-supporting architecture must provide:
+ */
+
+/*
+ *	kgdb_arch_init - Perform any architecture specific initalization.
+ *
+ *	This function will handle the initalization of any architecture
+ *	specific callbacks.
+ */
+extern int kgdb_arch_init(void);
+
+/*
+ *	kgdb_arch_uninit - Perform any architecture specific uninitalization.
+ *
+ *	This function will handle the uninitalization of any architecture
+ *	specific callbacks, for dynamic registration and unregistration.
+ */
+extern void kgdb_arch_uninit(void);
+
+/*
+ *	pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
+ *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
+ *	@regs: The &struct pt_regs of the current process.
+ *
+ *	Convert the pt_regs in @regs into the format for registers that
+ *	GDB expects, stored in @gdb_regs.
+ */
+extern void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs);
+
+/*
+ *	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.
+ */
+extern void
+sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p);
+
+/*
+ *	gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
+ *	@gdb_regs: A pointer to hold the registers we've received from GDB.
+ *	@regs: A pointer to a &struct pt_regs to hold these values in.
+ *
+ *	Convert the GDB regs in @gdb_regs into the pt_regs, and store them
+ *	in @regs.
+ */
+extern void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs);
+
+/*
+ *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
+ *	@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.
+ *	@remcom_in_buffer: The buffer of the packet we have read.
+ *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
+ *	@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.
+ */
+extern int
+kgdb_arch_handle_exception(int vector, int signo, int err_code,
+			   char *remcom_in_buffer,
+			   char *remcom_out_buffer,
+			   struct pt_regs *regs);
+
+/*
+ *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
+ *	@flags: Current IRQ state
+ *
+ *	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. In
+ *	this case, we have to make sure that interrupts are enabled before
+ *	calling smp_call_function(). The argument to this function is
+ *	the flags that will be used when restoring the interrupts. There is
+ *	local_irq_save() call before kgdb_roundup_cpus().
+ *
+ *	On non-SMP systems, this is not called.
+ */
+extern void kgdb_roundup_cpus(unsigned long flags);
+
+/* Optional functions. */
+extern int kgdb_validate_break_address(unsigned long addr);
+extern int kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr);
+extern int kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle);
+
+/*
+ * struct kgdb_arch - Describe architecture specific values.
+ * @gdb_bpt_instr: The instruction to trigger a breakpoint.
+ * @flags: Flags for the breakpoint, currently just %KGDB_HW_BREAKPOINT.
+ * @shadowth: A value of %1 indicates we shadow information on processes.
+ * @set_breakpoint: Allow an architecture to specify how to set a software
+ * breakpoint.
+ * @remove_breakpoint: Allow an architecture to specify how to remove a
+ * software breakpoint.
+ * @set_hw_breakpoint: Allow an architecture to specify how to set a hardware
+ * breakpoint.
+ * @remove_hw_breakpoint: Allow an architecture to specify how to remove a
+ * hardware breakpoint.
+ * @remove_all_hw_break: Allow an architecture to specify how to remove all
+ * hardware breakpoints.
+ * @correct_hw_break: Allow an architecture to specify how to correct the
+ * hardware debug registers.
+ *
+ * The @shadowth flag is an option to shadow information not retrievable by
+ * gdb otherwise.  This is deprecated in favor of a binutils which supports
+ * CFI macros.
+ */
+struct kgdb_arch {
+	unsigned char		gdb_bpt_instr[BREAK_INSTR_SIZE];
+	unsigned long		flags;
+	unsigned		shadowth;
+
+	int	(*set_breakpoint)(unsigned long, char *);
+	int	(*remove_breakpoint)(unsigned long, char *);
+	int	(*set_hw_breakpoint)(unsigned long, int, enum kgdb_bptype);
+	int	(*remove_hw_breakpoint)(unsigned long, int, enum kgdb_bptype);
+	void	(*remove_all_hw_break)(void);
+	void	(*correct_hw_break)(void);
+};
+
+/*
+ * struct kgdb_io - Describe the interface for an I/O driver to talk with KGDB.
+ * @name: Name of the I/O driver.
+ * @read_char: Pointer to a function that will return one char.
+ * @write_char: Pointer to a function that will write one char.
+ * @flush: Pointer to a function that will flush any pending writes.
+ * @init: Pointer to a function that will initialize the device.
+ * @pre_exception: Pointer to a function that will do any prep work for
+ * the I/O driver.
+ * @post_exception: Pointer to a function that will do any cleanup work
+ * for the I/O driver.
+ */
+struct kgdb_io {
+	const char		*name;
+	int			(*read_char) (void);
+	void			(*write_char) (u8);
+	void			(*flush) (void);
+	int			(*init) (void);
+	void			(*pre_exception) (void);
+	void			(*post_exception) (void);
+};
+
+extern struct kgdb_arch		arch_kgdb_ops;
+
+extern int kgdb_register_io_module(struct kgdb_io *local_kgdb_io_ops);
+extern void kgdb_unregister_io_module(struct kgdb_io *local_kgdb_io_ops);
+
+extern int kgdb_hex2long(char **ptr, long *long_val);
+extern int kgdb_mem2hex(char *mem, char *buf, int count);
+extern int kgdb_hex2mem(char *buf, char *mem, int count);
+
+extern int kgdb_isremovedbreak(unsigned long addr);
+
+extern int
+kgdb_handle_exception(int ex_vector, int signo, int err_code,
+		      struct pt_regs *regs);
+extern int kgdb_nmicallback(int cpu, void *regs);
+
+extern int			kgdb_single_step;
+extern atomic_t			kgdb_active;
+
+#endif /* _KGDB_H_ */
diff --git a/include/linux/pid.h b/include/linux/pid.h
index f84d532..e066d3d 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -86,6 +86,8 @@ extern struct task_struct *FASTCALL(get_pid_task(struct pid *pid,
 
 extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
 
+extern int pid_max;
+
 /*
  * attach_pid() and detach_pid() must be called with the tasklist_lock
  * write-held.
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 1a0b6cf..7d1a46b 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -211,6 +211,10 @@ struct uart_ops {
 	void		(*config_port)(struct uart_port *, int);
 	int		(*verify_port)(struct uart_port *, struct serial_struct *);
 	int		(*ioctl)(struct uart_port *, unsigned int, unsigned long);
+#ifdef CONFIG_CONSOLE_POLL
+	void	(*poll_put_char)(struct uart_port *, unsigned char);
+	int		(*poll_get_char)(struct uart_port *);
+#endif
 };
 
 #define UART_CONFIG_TYPE	(1 << 0)
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index 85c95cd..21f69ac 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -125,6 +125,7 @@
 #include <linux/cdev.h>
 
 struct tty_struct;
+struct tty_driver;
 
 struct tty_operations {
 	int  (*open)(struct tty_struct * tty, struct file * filp);
@@ -157,6 +158,11 @@ struct tty_operations {
 	int (*tiocmget)(struct tty_struct *tty, struct file *file);
 	int (*tiocmset)(struct tty_struct *tty, struct file *file,
 			unsigned int set, unsigned int clear);
+#ifdef CONFIG_CONSOLE_POLL
+	int (*poll_init)(struct tty_driver *driver, int line, char *options);
+	int (*poll_get_char)(struct tty_driver *driver, int line);
+	void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
+#endif
 };
 
 struct tty_driver {
@@ -220,6 +226,11 @@ struct tty_driver {
 	int (*tiocmget)(struct tty_struct *tty, struct file *file);
 	int (*tiocmset)(struct tty_struct *tty, struct file *file,
 			unsigned int set, unsigned int clear);
+#ifdef CONFIG_CONSOLE_POLL
+	int (*poll_init)(struct tty_driver *driver, int line, char *options);
+	int (*poll_get_char)(struct tty_driver *driver, int line);
+	void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
+#endif
 
 	struct list_head tty_drivers;
 };
@@ -230,6 +241,7 @@ struct tty_driver *alloc_tty_driver(int lines);
 void put_tty_driver(struct tty_driver *driver);
 void tty_set_operations(struct tty_driver *driver,
 			const struct tty_operations *op);
+extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
 
 /* tty driver magic number */
 #define TTY_DRIVER_MAGIC		0x5402
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 975c963..fec6dec 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -84,4 +84,26 @@ static inline unsigned long __copy_from_user_nocache(void *to,
 		ret;					\
 	})
 
+/*
+ * probe_kernel_read(): safely attempt to read from a location
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from
+ * @size: size of the data chunk
+ *
+ * Safely read from address @src to the buffer at @dst.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long probe_kernel_read(void *dst, void *src, size_t size);
+
+/*
+ * probe_kernel_write(): safely attempt to write to a location
+ * @dst: address to write to
+ * @src: pointer to the data that shall be written
+ * @size: size of the data chunk
+ *
+ * Safely write to address @dst from the buffer at @src.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long probe_kernel_write(void *dst, void *src, size_t size);
+
 #endif		/* __LINUX_UACCESS_H__ */
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c584c5..05c8003 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
 obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
 obj-$(CONFIG_KPROBES) += kprobes.o
+obj-$(CONFIG_KGDB) += kgdb.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 obj-$(CONFIG_SECCOMP) += seccomp.o
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
new file mode 100644
index 0000000..dce89d1
--- /dev/null
+++ b/kernel/kgdb.c
@@ -0,0 +1,1838 @@
+/*
+ * KGDB stub.
+ *
+ * Maintainer: Jason Wessel <jason.wessel@...driver.com>
+ *
+ * Copyright (C) 2000-2001 VERITAS Software Corporation.
+ * Copyright (C) 2002-2004 Timesys Corporation
+ * Copyright (C) 2003-2004 Amit S. Kale <amitkale@...syssoft.com>
+ * Copyright (C) 2004 Pavel Machek <pavel@...e.cz>
+ * Copyright (C) 2004-2006 Tom Rini <trini@...nel.crashing.org>
+ * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
+ * Copyright (C) 2005-2008 Wind River Systems, Inc.
+ * Copyright (C) 2007 MontaVista Software, Inc.
+ * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@...hat.com>
+ *
+ * Contributors at various stages not listed above:
+ *  Jason Wessel ( jason.wessel@...driver.com )
+ *  George Anzinger <george@...sta.com>
+ *  Anurekh Saxena (anurekh.saxena@...esys.com)
+ *  Lake Stevens Instrument Division (Glenn Engel)
+ *  Jim Kingdon, Cygnus Support.
+ *
+ * Original KGDB stub: David Grothe <dave@...m.com>,
+ * Tigran Aivazian <tigran@....com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+#include <linux/pid_namespace.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/spinlock.h>
+#include <linux/console.h>
+#include <linux/threads.h>
+#include <linux/uaccess.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/ptrace.h>
+#include <linux/reboot.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+#include <linux/sched.h>
+#include <linux/sysrq.h>
+#include <linux/init.h>
+#include <linux/kgdb.h>
+#include <linux/pid.h>
+#include <linux/smp.h>
+#include <linux/mm.h>
+
+#include <asm/cacheflush.h>
+#include <asm/byteorder.h>
+#include <asm/atomic.h>
+#include <asm/system.h>
+
+static int kgdb_break_asap;
+
+struct kgdb_state {
+	int			all_cpus_synced;
+	int			ex_vector;
+	int			signo;
+	int			err_code;
+	int			cpu;
+	int			pass_exception;
+	long			threadid;
+	long			kgdb_usethreadid;
+	struct pt_regs		*linux_regs;
+};
+
+static struct debuggerinfo_struct {
+	void			*debuggerinfo;
+	struct task_struct	*task;
+} kgdb_info[NR_CPUS];
+
+/**
+ * kgdb_connected - Is a host GDB connected to us?
+ */
+int				kgdb_connected;
+EXPORT_SYMBOL_GPL(kgdb_connected);
+
+/* All the KGDB handlers are installed */
+static int			kgdb_io_module_registered;
+
+/* Guard for recursive entry */
+static int			exception_level;
+
+static struct kgdb_io		*kgdb_io_ops;
+static DEFINE_SPINLOCK(kgdb_registration_lock);
+
+/*
+ * Holds information about breakpoints in a kernel. These breakpoints are
+ * added and removed by gdb.
+ */
+static struct kgdb_bkpt		kgdb_break[KGDB_MAX_BREAKPOINTS] = {
+	[0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
+};
+
+/*
+ * KGDB locking is really nasty at places - but we really can only
+ * do sane debugging if all processors are in a controlled state.
+ *
+ * So we go through painful cycles of wait and see, with every
+ * CPU having a lock:
+ */
+
+/* How many times to count all of the waiting CPUs */
+#define ROUNDUP_WAIT		640000	/* Arbitrary, increase if needed. */
+#define BUF_THREAD_ID_SIZE	16
+
+static spinlock_t		slave_cpu_locks[NR_CPUS] = {
+	[0 ... NR_CPUS-1] = __SPIN_LOCK_UNLOCKED(slave_cpu_locks)
+};
+static atomic_t			cpu_in_kgdb[NR_CPUS];
+atomic_t			kgdb_setting_breakpoint;
+
+struct task_struct		*kgdb_usethread;
+struct task_struct		*kgdb_contthread;
+
+int				kgdb_single_step;
+static atomic_t			kgdb_sync = ATOMIC_INIT(-1);
+atomic_t			kgdb_active;
+
+/* Our I/O buffers. */
+static char			remcom_in_buffer[BUFMAX];
+static char			remcom_out_buffer[BUFMAX];
+
+/* Storage for the registers, in GDB format. */
+static unsigned long		gdb_regs[(NUMREGBYTES +
+					sizeof(unsigned long) - 1) /
+					sizeof(unsigned long)];
+
+/* to keep track of the CPU which is doing the single stepping*/
+atomic_t			kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
+
+static int
+kgdb_notify_reboot(struct notifier_block *this, unsigned long code, void *x);
+
+/* reboot notifier block */
+static struct notifier_block kgdb_reboot_notifier = {
+	.notifier_call		= kgdb_notify_reboot,
+	.priority		= INT_MAX,
+};
+
+/*
+ * Finally, some KGDB code :-)
+ */
+
+/*
+ * Weak aliases for breakpoint management,
+ * can be overriden by architectures when needed:
+ */
+int __weak kgdb_validate_break_address(unsigned long addr)
+{
+	char tmp_variable[BREAK_INSTR_SIZE];
+
+	return probe_kernel_read((char *)addr, tmp_variable, BREAK_INSTR_SIZE);
+}
+
+int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
+{
+	int err;
+
+	err = probe_kernel_read((char *)addr, saved_instr, BREAK_INSTR_SIZE);
+	if (err)
+		return err;
+
+	return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
+				  BREAK_INSTR_SIZE);
+}
+
+int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
+{
+	return probe_kernel_write((char *)addr,
+				  (char *)bundle, BREAK_INSTR_SIZE);
+}
+
+unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
+{
+	return instruction_pointer(regs);
+}
+
+/*
+ * GDB remote protocol parser:
+ */
+
+static const char	hexchars[] = "0123456789abcdef";
+
+static int hex(char ch)
+{
+	if ((ch >= 'a') && (ch <= 'f'))
+		return ch - 'a' + 10;
+	if ((ch >= '0') && (ch <= '9'))
+		return ch - '0';
+	if ((ch >= 'A') && (ch <= 'F'))
+		return ch - 'A' + 10;
+	return -1;
+}
+
+/* scan for the sequence $<data>#<checksum> */
+static void get_packet(char *buffer)
+{
+	unsigned char checksum;
+	unsigned char xmitcsum;
+	int count;
+	char ch;
+
+	do {
+		/*
+		 * Spin and wait around for the start character, ignore all
+		 * other characters:
+		 */
+		while ((ch = (kgdb_io_ops->read_char())) != '$')
+			/* nothing */;
+
+		kgdb_connected = 1;
+		checksum = 0;
+		xmitcsum = -1;
+
+		count = 0;
+
+		/*
+		 * now, read until a # or end of buffer is found:
+		 */
+		while (count < (BUFMAX - 1)) {
+			ch = kgdb_io_ops->read_char();
+			if (ch == '#')
+				break;
+			checksum = checksum + ch;
+			buffer[count] = ch;
+			count = count + 1;
+		}
+		buffer[count] = 0;
+
+		if (ch == '#') {
+			xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
+			xmitcsum += hex(kgdb_io_ops->read_char());
+
+			if (checksum != xmitcsum)
+				/* failed checksum */
+				kgdb_io_ops->write_char('-');
+			else
+				/* successful transfer */
+				kgdb_io_ops->write_char('+');
+			if (kgdb_io_ops->flush)
+				kgdb_io_ops->flush();
+		}
+	} while (checksum != xmitcsum);
+}
+
+/*
+ * Send the packet in buffer.
+ * Check for gdb connection if asked for.
+ */
+static void put_packet(char *buffer)
+{
+	unsigned char checksum;
+	int count;
+	char ch;
+
+	/*
+	 * $<packet info>#<checksum>.
+	 */
+	while (1) {
+		kgdb_io_ops->write_char('$');
+		checksum = 0;
+		count = 0;
+
+		while ((ch = buffer[count])) {
+			kgdb_io_ops->write_char(ch);
+			checksum += ch;
+			count++;
+		}
+
+		kgdb_io_ops->write_char('#');
+		kgdb_io_ops->write_char(hexchars[checksum >> 4]);
+		kgdb_io_ops->write_char(hexchars[checksum & 0xf]);
+		if (kgdb_io_ops->flush)
+			kgdb_io_ops->flush();
+
+		/* Now see what we get in reply. */
+		ch = kgdb_io_ops->read_char();
+
+		if (ch == 3)
+			ch = kgdb_io_ops->read_char();
+
+		/* If we get an ACK, we are done. */
+		if (ch == '+')
+			return;
+
+		/*
+		 * If we get the start of another packet, this means
+		 * that GDB is attempting to reconnect.  We will NAK
+		 * the packet being sent, and stop trying to send this
+		 * packet.
+		 */
+		if (ch == '$') {
+			kgdb_io_ops->write_char('-');
+			if (kgdb_io_ops->flush)
+				kgdb_io_ops->flush();
+			return;
+		}
+	}
+}
+
+static char *pack_hex_byte(char *pkt, u8 byte)
+{
+	*pkt++ = hexchars[byte >> 4];
+	*pkt++ = hexchars[byte & 0xf];
+
+	return pkt;
+}
+
+/*
+ * Convert the memory pointed to by mem into hex, placing result in buf.
+ * Return a pointer to the last char put in buf (null). May return an error.
+ */
+int kgdb_mem2hex(char *mem, char *buf, int count)
+{
+	char *tmp;
+	int err;
+
+	/*
+	 * We use the upper half of buf as an intermediate buffer for the
+	 * raw memory copy.  Hex conversion will work against this one.
+	 */
+	tmp = buf + count;
+
+	err = probe_kernel_read(tmp, mem, count);
+	if (!err) {
+		while (count > 0) {
+			buf = pack_hex_byte(buf, *tmp);
+			tmp++;
+			count--;
+		}
+
+		*buf = 0;
+	}
+
+	return err;
+}
+
+/*
+ * Copy the binary array pointed to by buf into mem.  Fix $, #, and
+ * 0x7d escaped with 0x7d.  Return a pointer to the character after
+ * the last byte written.
+ */
+static int kgdb_ebin2mem(char *buf, char *mem, int count)
+{
+	int err = 0;
+	char c;
+
+	while (count-- > 0) {
+		c = *buf++;
+		if (c == 0x7d)
+			c = *buf++ ^ 0x20;
+
+		err = probe_kernel_write(mem, &c, 1);
+		if (err)
+			break;
+
+		mem++;
+	}
+
+	return err;
+}
+
+/*
+ * Convert the hex array pointed to by buf into binary to be placed in mem.
+ * Return a pointer to the character AFTER the last byte written.
+ * May return an error.
+ */
+int kgdb_hex2mem(char *buf, char *mem, int count)
+{
+	char *tmp_raw;
+	char *tmp_hex;
+
+	/*
+	 * We use the upper half of buf as an intermediate buffer for the
+	 * raw memory that is converted from hex.
+	 */
+	tmp_raw = buf + count * 2;
+
+	tmp_hex = tmp_raw - 1;
+	while (tmp_hex >= buf) {
+		tmp_raw--;
+		*tmp_raw = hex(*tmp_hex--);
+		*tmp_raw |= hex(*tmp_hex--) << 4;
+	}
+
+	return probe_kernel_write(mem, tmp_raw, count);
+}
+
+/*
+ * While we find nice hex chars, build a long_val.
+ * Return number of chars processed.
+ */
+int kgdb_hex2long(char **ptr, long *long_val)
+{
+	int hex_val;
+	int num = 0;
+
+	*long_val = 0;
+
+	while (**ptr) {
+		hex_val = hex(**ptr);
+		if (hex_val < 0)
+			break;
+
+		*long_val = (*long_val << 4) | hex_val;
+		num++;
+		(*ptr)++;
+	}
+
+	return num;
+}
+
+/* Write memory due to an 'M' or 'X' packet. */
+static int write_mem_msg(int binary)
+{
+	char *ptr = &remcom_in_buffer[1];
+	unsigned long addr;
+	unsigned long length;
+	int err;
+
+	if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
+	    kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
+		if (binary)
+			err = kgdb_ebin2mem(ptr, (char *)addr, length);
+		else
+			err = kgdb_hex2mem(ptr, (char *)addr, length);
+		if (err)
+			return err;
+		if (CACHE_FLUSH_IS_SAFE)
+			flush_icache_range(addr, addr + length + 1);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static void error_packet(char *pkt, int error)
+{
+	error = -error;
+	pkt[0] = 'E';
+	pkt[1] = hexchars[(error / 10)];
+	pkt[2] = hexchars[(error % 10)];
+	pkt[3] = '\0';
+}
+
+/*
+ * Black magic portion #2. Thread ID accessors.
+ */
+
+static char *pack_threadid(char *pkt, unsigned char *id)
+{
+	char *limit;
+
+	limit = pkt + BUF_THREAD_ID_SIZE;
+	while (pkt < limit)
+		pkt = pack_hex_byte(pkt, *id++);
+
+	return pkt;
+}
+
+static void int_to_threadref(unsigned char *id, int value)
+{
+	unsigned char *scan;
+	int i = 4;
+
+	scan = (unsigned char *)id;
+	while (i--)
+		*scan++ = 0;
+	*scan++ = (value >> 24) & 0xff;
+	*scan++ = (value >> 16) & 0xff;
+	*scan++ = (value >> 8) & 0xff;
+	*scan++ = (value & 0xff);
+}
+
+static struct task_struct *getthread(struct pt_regs *regs, int tid)
+{
+	if (init_pid_ns.last_pid == 0)
+		return current;
+
+	if (num_online_cpus() && (tid >= pid_max + num_online_cpus() +
+							arch_kgdb_ops.shadowth))
+		return NULL;
+
+	if (arch_kgdb_ops.shadowth && (tid >= pid_max + num_online_cpus())) {
+		return kgdb_get_shadow_thread(regs, tid - pid_max -
+					      num_online_cpus());
+	}
+
+	if (tid >= pid_max)
+		return idle_task(tid - pid_max);
+
+	if (!tid)
+		return NULL;
+
+	/*
+	 * find_task_by_pid() does not take the tasklist lock anymore
+	 * but is nicely RCU locked - hence is a pretty resilient
+	 * thing to use:
+	 */
+	return find_task_by_pid(tid);
+}
+
+/*
+ * CPU debug state control:
+ */
+
+#ifdef CONFIG_SMP
+static void kgdb_wait(struct pt_regs *regs)
+{
+	unsigned long flags;
+	int cpu;
+
+	local_irq_save(flags);
+	cpu = raw_smp_processor_id();
+	kgdb_info[cpu].debuggerinfo = regs;
+	kgdb_info[cpu].task = current;
+	atomic_set(&cpu_in_kgdb[cpu], 1);
+
+	/*
+	 * The master CPU must be active to enter here, but this is
+	 * gaurd in case the master CPU had not been selected if
+	 * this was an entry via nmi.
+	 */
+	while (!atomic_read(&kgdb_active))
+		cpu_relax();
+
+	/* Wait till master CPU goes completely into the debugger. */
+	while (!atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active) - 1])) {
+		int i = 10;	/* an arbitrary number. Be nice. A bit. */
+
+		while (--i)
+			cpu_relax();
+	}
+
+	/* Wait till master CPU is done with debugging */
+	spin_lock(&slave_cpu_locks[cpu]);
+
+	kgdb_info[cpu].debuggerinfo = NULL;
+	kgdb_info[cpu].task = NULL;
+
+	/* fix up hardware debug registers on local cpu */
+	if (arch_kgdb_ops.correct_hw_break)
+		arch_kgdb_ops.correct_hw_break();
+
+	/* Signal the master CPU that we are done: */
+	atomic_set(&cpu_in_kgdb[cpu], 0);
+	spin_unlock(&slave_cpu_locks[cpu]);
+	local_irq_restore(flags);
+}
+#endif
+
+/*
+ * Some architectures need cache flushes when we set/clear a
+ * breakpoint:
+ */
+static void kgdb_flush_swbreak_addr(unsigned long addr)
+{
+	if (!CACHE_FLUSH_IS_SAFE)
+		return;
+
+	if (current->mm) {
+		flush_cache_range(current->mm->mmap_cache,
+				  addr, addr + BREAK_INSTR_SIZE);
+	} else {
+		flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
+	}
+}
+
+/*
+ * SW breakpoint management:
+ */
+static int kgdb_activate_sw_breakpoints(void)
+{
+	unsigned long addr;
+	int error = 0;
+	int i;
+
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if (kgdb_break[i].state != BP_SET)
+			continue;
+
+		addr = kgdb_break[i].bpt_addr;
+		error = kgdb_arch_set_breakpoint(addr,
+				kgdb_break[i].saved_instr);
+		if (error)
+			return error;
+
+		kgdb_flush_swbreak_addr(addr);
+		kgdb_break[i].state = BP_ACTIVE;
+	}
+	return 0;
+}
+
+static int kgdb_set_sw_break(unsigned long addr)
+{
+	int err = kgdb_validate_break_address(addr);
+	int breakno = -1;
+	int i;
+
+	if (err)
+		return err;
+
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if ((kgdb_break[i].state == BP_SET) &&
+					(kgdb_break[i].bpt_addr == addr))
+			return -EEXIST;
+	}
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if (kgdb_break[i].state == BP_REMOVED &&
+					kgdb_break[i].bpt_addr == addr) {
+			breakno = i;
+			break;
+		}
+	}
+
+	if (breakno == -1) {
+		for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+			if (kgdb_break[i].state == BP_UNDEFINED) {
+				breakno = i;
+				break;
+			}
+		}
+	}
+
+	if (breakno == -1)
+		return -E2BIG;
+
+	kgdb_break[breakno].state = BP_SET;
+	kgdb_break[breakno].type = BP_BREAKPOINT;
+	kgdb_break[breakno].bpt_addr = addr;
+
+	return 0;
+}
+
+static int kgdb_deactivate_sw_breakpoints(void)
+{
+	unsigned long addr;
+	int error = 0;
+	int i;
+
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if (kgdb_break[i].state != BP_ACTIVE)
+			continue;
+		addr = kgdb_break[i].bpt_addr;
+		error = kgdb_arch_remove_breakpoint(addr,
+					kgdb_break[i].saved_instr);
+		if (error)
+			return error;
+
+		kgdb_flush_swbreak_addr(addr);
+		kgdb_break[i].state = BP_SET;
+	}
+	return 0;
+}
+
+static int kgdb_remove_sw_break(unsigned long addr)
+{
+	int i;
+
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if ((kgdb_break[i].state == BP_SET) &&
+				(kgdb_break[i].bpt_addr == addr)) {
+			kgdb_break[i].state = BP_REMOVED;
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+
+int kgdb_isremovedbreak(unsigned long addr)
+{
+	int i;
+
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if ((kgdb_break[i].state == BP_REMOVED) &&
+					(kgdb_break[i].bpt_addr == addr))
+			return 1;
+	}
+	return 0;
+}
+
+int remove_all_break(void)
+{
+	unsigned long addr;
+	int error;
+	int i;
+
+	/* Clear memory breakpoints. */
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if (kgdb_break[i].state != BP_SET)
+			continue;
+		addr = kgdb_break[i].bpt_addr;
+		error = kgdb_arch_remove_breakpoint(addr,
+				kgdb_break[i].saved_instr);
+		if (error)
+			return error;
+		kgdb_break[i].state = BP_REMOVED;
+	}
+
+	/* Clear hardware breakpoints. */
+	if (arch_kgdb_ops.remove_all_hw_break)
+		arch_kgdb_ops.remove_all_hw_break();
+
+	return 0;
+}
+
+static inline int shadow_pid(int realpid)
+{
+	if (realpid)
+		return realpid;
+
+	return pid_max + raw_smp_processor_id();
+}
+
+static char gdbmsgbuf[BUFMAX + 1];
+
+static void kgdb_msg_write(const char *s, int len)
+{
+	char *bufptr;
+	int wcount;
+	int i;
+
+	/* 'O'utput */
+	gdbmsgbuf[0] = 'O';
+
+	/* Fill and send buffers... */
+	while (len > 0) {
+		bufptr = gdbmsgbuf + 1;
+
+		/* Calculate how many this time */
+		if ((len << 1) > (BUFMAX - 2))
+			wcount = (BUFMAX - 2) >> 1;
+		else
+			wcount = len;
+
+		/* Pack in hex chars */
+		for (i = 0; i < wcount; i++)
+			bufptr = pack_hex_byte(bufptr, s[i]);
+		*bufptr = '\0';
+
+		/* Move up */
+		s += wcount;
+		len -= wcount;
+
+		/* Write packet */
+		put_packet(gdbmsgbuf);
+	}
+}
+
+/*
+ * Return true if there is a valid kgdb I/O module.  Also if no
+ * debugger is attached a message can be printed to the console about
+ * waiting for the debugger to attach.
+ *
+ * The print_wait argument is only to be true when called from inside
+ * the core kgdb_handle_exception, because it will wait for the
+ * debugger to attach.
+ */
+static int kgdb_io_ready(int print_wait)
+{
+	if (!kgdb_io_ops)
+		return 0;
+	if (kgdb_connected)
+		return 1;
+	if (atomic_read(&kgdb_setting_breakpoint))
+		return 1;
+	if (print_wait)
+		printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
+	return 1;
+}
+
+/*
+ * All the functions that start with gdb_cmd are the various
+ * operations to implement the handlers for the gdbserial protocol
+ * where KGDB is communicating with an external debugger
+ */
+
+/* Handle the '?' status packets */
+static void gdb_cmd_status(struct kgdb_state *ks)
+{
+	/*
+	 * We know that this packet is only sent
+	 * during initial connect.  So to be safe,
+	 * we clear out our breakpoints now in case
+	 * GDB is reconnecting.
+	 */
+	remove_all_break();
+
+	/*
+	 * Also, if we haven't been able to roundup all
+	 * CPUs, send an 'O' packet informing the user
+	 * as much.  Only need to do this once.
+	 */
+	if (!ks->all_cpus_synced)
+		kgdb_msg_write("Not all CPUs have been synced for KGDB\n", 39);
+
+	remcom_out_buffer[0] = 'S';
+	pack_hex_byte(&remcom_out_buffer[1], ks->signo);
+}
+
+/* Handle the 'g' get registers request */
+static void gdb_cmd_getregs(struct kgdb_state *ks)
+{
+	struct pt_regs *shadowregs;
+	struct task_struct *thread;
+	void *local_debuggerinfo;
+	int i;
+
+	thread = kgdb_usethread;
+	if (!thread) {
+		thread = kgdb_info[ks->cpu].task;
+		local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
+	} else {
+		local_debuggerinfo = NULL;
+		for (i = 0; i < NR_CPUS; i++) {
+			/*
+			 * Try to find the task on some other
+			 * or possibly this node if we do not
+			 * find the matching task then we try
+			 * to approximate the results.
+			 */
+			if (thread == kgdb_info[i].task)
+				local_debuggerinfo = kgdb_info[i].debuggerinfo;
+		}
+	}
+
+	/*
+	 * All threads that don't have debuggerinfo should be
+	 * in __schedule() sleeping, since all other CPUs
+	 * are in kgdb_wait, and thus have debuggerinfo.
+	 */
+	if (arch_kgdb_ops.shadowth &&
+			ks->kgdb_usethreadid >= pid_max + num_online_cpus()) {
+
+		shadowregs = kgdb_shadow_regs(ks->linux_regs,
+					  ks->kgdb_usethreadid -
+					  pid_max -
+					  num_online_cpus());
+		if (!shadowregs) {
+			error_packet(remcom_out_buffer, -EINVAL);
+			return;
+		}
+		pt_regs_to_gdb_regs(gdb_regs, shadowregs);
+	} else {
+		if (local_debuggerinfo) {
+			pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
+		} else {
+			/*
+			 * Pull stuff saved during switch_to; nothing
+			 * else is accessible (or even particularly
+			 * relevant).
+			 *
+			 * This should be enough for a stack trace.
+			 */
+			sleeping_thread_to_gdb_regs(gdb_regs, thread);
+		}
+	}
+	kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
+}
+
+/* Handle the 'G' set registers request */
+static void gdb_cmd_setregs(struct kgdb_state *ks)
+{
+	kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
+
+	if (kgdb_usethread && kgdb_usethread != current) {
+		error_packet(remcom_out_buffer, -EINVAL);
+	} else {
+		gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
+		strcpy(remcom_out_buffer, "OK");
+	}
+}
+
+/* Handle the 'm' memory read bytes */
+static void gdb_cmd_memread(struct kgdb_state *ks)
+{
+	char *ptr = &remcom_in_buffer[1];
+	unsigned long length;
+	unsigned long addr;
+	int err;
+
+	if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
+					kgdb_hex2long(&ptr, &length) > 0) {
+		err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
+		if (err)
+			error_packet(remcom_out_buffer, err);
+	} else {
+		error_packet(remcom_out_buffer, -EINVAL);
+	}
+}
+
+/* Handle the 'M' memory write bytes */
+static void gdb_cmd_memwrite(struct kgdb_state *ks)
+{
+	int err = write_mem_msg(0);
+
+	if (err)
+		error_packet(remcom_out_buffer, err);
+	else
+		strcpy(remcom_out_buffer, "OK");
+}
+
+/* Handle the 'X' memory binary write bytes */
+static void gdb_cmd_binwrite(struct kgdb_state *ks)
+{
+	int err = write_mem_msg(1);
+
+	if (err)
+		error_packet(remcom_out_buffer, err);
+	else
+		strcpy(remcom_out_buffer, "OK");
+}
+
+/* Handle the 'D' or 'k', detach or kill packets */
+static void gdb_cmd_detachkill(struct kgdb_state *ks)
+{
+	int error;
+
+	/* The detach case */
+	if (remcom_in_buffer[0] == 'D') {
+		error = remove_all_break();
+		if (error < 0) {
+			error_packet(remcom_out_buffer, error);
+		} else {
+			strcpy(remcom_out_buffer, "OK");
+			kgdb_connected = 0;
+		}
+		put_packet(remcom_out_buffer);
+	} else {
+		/*
+		 * Assume the kill case, with no exit code checking,
+		 * trying to force detach the debugger:
+		 */
+		remove_all_break();
+		kgdb_connected = 0;
+	}
+}
+
+/* Handle the 'R' reboot packets */
+static int gdb_cmd_reboot(struct kgdb_state *ks)
+{
+	/* For now, only honor R0 */
+	if (strcmp(remcom_in_buffer, "R0") == 0) {
+		printk(KERN_CRIT "Executing reboot\n");
+		strcpy(remcom_out_buffer, "OK");
+		put_packet(remcom_out_buffer);
+		emergency_sync();
+
+		/*
+		 * Execution should not return from
+		 * machine_restart()
+		 */
+		machine_restart(NULL);
+		kgdb_connected = 0;
+
+		return 1;
+	}
+	return 0;
+}
+
+/* Handle the 'q' query packets */
+static void gdb_cmd_query(struct kgdb_state *ks)
+{
+	int numshadowth = num_online_cpus() + arch_kgdb_ops.shadowth;
+	struct task_struct *thread;
+	unsigned char thref[8];
+	char *ptr;
+	int i;
+
+	switch (remcom_in_buffer[1]) {
+	case 's':
+	case 'f':
+		if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
+			error_packet(remcom_out_buffer, -EINVAL);
+			break;
+		}
+
+		/*
+		 * If we have not yet completed in
+		 * pidhash_init() there isn't much we
+		 * can give back.
+		 */
+		if (init_pid_ns.last_pid == 0) {
+			if (remcom_in_buffer[1] == 'f')
+				strcpy(remcom_out_buffer, "m0000000000000001");
+			break;
+		}
+
+		if (remcom_in_buffer[1] == 'f')
+			ks->threadid = 1;
+
+		remcom_out_buffer[0] = 'm';
+		ptr = remcom_out_buffer + 1;
+
+		for (i = 0; i < 17 && ks->threadid < pid_max + numshadowth;
+							ks->threadid++) {
+
+			thread = getthread(ks->linux_regs, ks->threadid);
+			if (thread) {
+				int_to_threadref(thref, ks->threadid);
+				pack_threadid(ptr, thref);
+				ptr += 16;
+				*(ptr++) = ',';
+				i++;
+			}
+		}
+		*(--ptr) = '\0';
+		break;
+
+	case 'C':
+		/* Current thread id */
+		strcpy(remcom_out_buffer, "QC");
+		ks->threadid = shadow_pid(current->pid);
+		int_to_threadref(thref, ks->threadid);
+		pack_threadid(remcom_out_buffer + 2, thref);
+		break;
+	case 'T':
+		if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
+			error_packet(remcom_out_buffer, -EINVAL);
+			break;
+		}
+		ks->threadid = 0;
+		ptr = remcom_in_buffer + 17;
+		kgdb_hex2long(&ptr, &ks->threadid);
+		if (!getthread(ks->linux_regs, ks->threadid)) {
+			error_packet(remcom_out_buffer, -EINVAL);
+			break;
+		}
+		if (ks->threadid < pid_max) {
+			kgdb_mem2hex(getthread(ks->linux_regs,
+					ks->threadid)->comm,
+					remcom_out_buffer, 16);
+		} else {
+			if (ks->threadid >= pid_max + num_online_cpus()) {
+				kgdb_shadowinfo(ks->linux_regs,
+					remcom_out_buffer,
+					ks->threadid - pid_max -
+					num_online_cpus());
+			} else {
+				static char tmpstr[23 + BUF_THREAD_ID_SIZE];
+				sprintf(tmpstr, "Shadow task %d for pid 0",
+						(int)(ks->threadid - pid_max));
+				kgdb_mem2hex(tmpstr, remcom_out_buffer,
+							 strlen(tmpstr));
+			}
+		}
+		break;
+	}
+}
+
+/* Handle the 'H' task query packets */
+static void gdb_cmd_task(struct kgdb_state *ks)
+{
+	struct task_struct *thread;
+	char *ptr;
+
+	switch (remcom_in_buffer[1]) {
+	case 'g':
+		ptr = &remcom_in_buffer[2];
+		kgdb_hex2long(&ptr, &ks->threadid);
+		thread = getthread(ks->linux_regs, ks->threadid);
+		if (!thread && ks->threadid > 0) {
+			error_packet(remcom_out_buffer, -EINVAL);
+			break;
+		}
+		kgdb_usethread = thread;
+		ks->kgdb_usethreadid = ks->threadid;
+		strcpy(remcom_out_buffer, "OK");
+		break;
+	case 'c':
+		ptr = &remcom_in_buffer[2];
+		kgdb_hex2long(&ptr, &ks->threadid);
+		if (!ks->threadid) {
+			kgdb_contthread = NULL;
+		} else {
+			thread = getthread(ks->linux_regs, ks->threadid);
+			if (!thread && ks->threadid > 0) {
+				error_packet(remcom_out_buffer, -EINVAL);
+				break;
+			}
+			kgdb_contthread = thread;
+		}
+		strcpy(remcom_out_buffer, "OK");
+		break;
+	}
+}
+
+/* Handle the 'T' thread query packets */
+static void gdb_cmd_thread(struct kgdb_state *ks)
+{
+	char *ptr = &remcom_in_buffer[1];
+	struct task_struct *thread;
+
+	kgdb_hex2long(&ptr, &ks->threadid);
+	thread = getthread(ks->linux_regs, ks->threadid);
+	if (thread)
+		strcpy(remcom_out_buffer, "OK");
+	else
+		error_packet(remcom_out_buffer, -EINVAL);
+}
+
+/* Handle the 'z' or 'Z' breakpoint remove or set packets */
+static void gdb_cmd_break(struct kgdb_state *ks)
+{
+	/*
+	 * Since GDB-5.3, it's been drafted that '0' is a software
+	 * breakpoint, '1' is a hardware breakpoint, so let's do that.
+	 */
+	char *bpt_type = &remcom_in_buffer[1];
+	char *ptr = &remcom_in_buffer[2];
+	unsigned long addr;
+	unsigned long length;
+	int error = 0;
+
+	if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
+		/* Unsupported */
+		if (*bpt_type > '4')
+			return;
+	} else {
+		if (*bpt_type != '0' && *bpt_type != '1')
+			/* Unsupported. */
+			return;
+	}
+
+	/*
+	 * Test if this is a hardware breakpoint, and
+	 * if we support it:
+	 */
+	if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
+		/* Unsupported. */
+		return;
+
+	if (*(ptr++) != ',') {
+		error_packet(remcom_out_buffer, -EINVAL);
+		return;
+	}
+	if (!kgdb_hex2long(&ptr, &addr)) {
+		error_packet(remcom_out_buffer, -EINVAL);
+		return;
+	}
+	if (*(ptr++) != ',' ||
+		!kgdb_hex2long(&ptr, &length)) {
+		error_packet(remcom_out_buffer, -EINVAL);
+		return;
+	}
+
+	if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
+		error = kgdb_set_sw_break(addr);
+	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
+		error = kgdb_remove_sw_break(addr);
+	else if (remcom_in_buffer[0] == 'Z')
+		error = arch_kgdb_ops.set_hw_breakpoint(addr,
+			(int)length, *bpt_type);
+	else if (remcom_in_buffer[0] == 'z')
+		error = arch_kgdb_ops.remove_hw_breakpoint(addr,
+			(int) length, *bpt_type);
+
+	if (error == 0)
+		strcpy(remcom_out_buffer, "OK");
+	else
+		error_packet(remcom_out_buffer, error);
+}
+
+/* Handle the 'C' signal / exception passing packets */
+static int gdb_cmd_exception_pass(struct kgdb_state *ks)
+{
+	/* C09 == pass exception
+	 * C15 == detach kgdb, pass exception
+	 */
+	if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
+
+		ks->pass_exception = 1;
+		remcom_in_buffer[0] = 'c';
+
+	} else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
+
+		ks->pass_exception = 1;
+		remcom_in_buffer[0] = 'D';
+		remove_all_break();
+		kgdb_connected = 0;
+		return 1;
+
+	} else {
+		error_packet(remcom_out_buffer, -EINVAL);
+		return 0;
+	}
+
+	/* Indicate fall through */
+	return -1;
+}
+
+/*
+ * This function performs all gdbserial command procesing
+ */
+static int gdb_serial_stub(struct kgdb_state *ks)
+{
+	int error = 0;
+	int tmp;
+
+	/* Clear the out buffer. */
+	memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
+
+	if (kgdb_connected) {
+		unsigned char thref[8];
+		char *ptr;
+
+		/*
+		 * Warn debugger if the CPUs are not synced with an 'O'
+		 * packet:
+		 */
+		if (!ks->all_cpus_synced) {
+			kgdb_msg_write("Not all CPUs have been synced for "
+			       "KGDB\n", 39);
+		}
+		/* Reply to host that an exception has occurred */
+		ptr = remcom_out_buffer;
+		*ptr++ = 'T';
+		ptr = pack_hex_byte(ptr, ks->signo);
+		ptr += strlen(strcpy(ptr, "thread:"));
+		int_to_threadref(thref, shadow_pid(current->pid));
+		ptr = pack_threadid(ptr, thref);
+		*ptr++ = ';';
+		put_packet(remcom_out_buffer);
+	}
+
+	kgdb_usethread = kgdb_info[ks->cpu].task;
+	ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
+	ks->pass_exception = 0;
+
+	while (1) {
+		error = 0;
+
+		/* Clear the out buffer. */
+		memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
+
+		get_packet(remcom_in_buffer);
+
+		switch (remcom_in_buffer[0]) {
+		case '?': /* gdbserial status */
+			gdb_cmd_status(ks);
+			break;
+		case 'g': /* return the value of the CPU registers */
+			gdb_cmd_getregs(ks);
+			break;
+		case 'G': /* set the value of the CPU registers - return OK */
+			gdb_cmd_setregs(ks);
+			break;
+		case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
+			gdb_cmd_memread(ks);
+			break;
+		case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
+			gdb_cmd_memwrite(ks);
+			break;
+		case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
+			gdb_cmd_binwrite(ks);
+			break;
+			/* kill or detach. KGDB should treat this like a
+			 * continue.
+			 */
+		case 'D': /* Debugger detach */
+		case 'k': /* Debugger detach via kill */
+			gdb_cmd_detachkill(ks);
+			goto default_handle;
+		case 'R': /* Reboot */
+			if (gdb_cmd_reboot(ks))
+				goto default_handle;
+			break;
+		case 'q': /* query command */
+			gdb_cmd_query(ks);
+			break;
+		case 'H': /* task related */
+			gdb_cmd_task(ks);
+			break;
+		case 'T': /* Query thread status */
+			gdb_cmd_thread(ks);
+			break;
+		case 'z': /* Break point remove */
+		case 'Z': /* Break point set */
+			gdb_cmd_break(ks);
+			break;
+		case 'C': /* Exception passing */
+			tmp = gdb_cmd_exception_pass(ks);
+			if (tmp > 0)
+				goto default_handle;
+			if (tmp == 0)
+				break;
+			/* Fall through on tmp < 0 */
+		case 'c': /* Continue packet */
+		case 's': /* Single step packet */
+			if (kgdb_contthread && kgdb_contthread != current) {
+				/* Can't switch threads in kgdb */
+				error_packet(remcom_out_buffer, -EINVAL);
+				break;
+			}
+			kgdb_activate_sw_breakpoints();
+			/* Fall through to default processing */
+		default:
+default_handle:
+			error = kgdb_arch_handle_exception(ks->ex_vector,
+						ks->signo,
+						ks->err_code,
+						remcom_in_buffer,
+						remcom_out_buffer,
+						ks->linux_regs);
+			/*
+			 * Leave cmd processing on error, detach,
+			 * kill, continue, or single step.
+			 */
+			if (error >= 0 || remcom_in_buffer[0] == 'D' ||
+			    remcom_in_buffer[0] == 'k') {
+				error = 0;
+				goto kgdb_exit;
+			}
+
+		}
+
+		/* reply to the request */
+		put_packet(remcom_out_buffer);
+	}
+
+kgdb_exit:
+	if (ks->pass_exception)
+		error = 1;
+	return error;
+}
+
+static int kgdb_reenter_check(struct kgdb_state *ks)
+{
+	unsigned long addr;
+
+	if (atomic_read(&kgdb_active) != raw_smp_processor_id() + 1)
+		return 0;
+
+	/* Panic on recursive debugger calls: */
+	exception_level++;
+	addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
+	kgdb_deactivate_sw_breakpoints();
+
+	/*
+	 * If the break point removed ok at the place exception
+	 * occurred, try to recover and print a warning to the end
+	 * user because the user planted a breakpoint in a place that
+	 * KGDB needs in order to function.
+	 */
+	if (kgdb_remove_sw_break(addr) == 0) {
+		exception_level = 0;
+		kgdb_skipexception(ks->ex_vector, ks->linux_regs);
+		kgdb_activate_sw_breakpoints();
+		printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed\n");
+		WARN_ON_ONCE(1);
+
+		return 1;
+	}
+	remove_all_break();
+	kgdb_skipexception(ks->ex_vector, ks->linux_regs);
+
+	if (exception_level > 1) {
+		dump_stack();
+		panic("Recursive entry to debugger");
+	}
+
+	printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
+	dump_stack();
+	panic("Recursive entry to debugger");
+
+	return 1;
+}
+
+/*
+ * kgdb_handle_exception() - main entry point from a kernel exception
+ *
+ * Locking hierarchy:
+ *	interface locks, if any (begin_session)
+ *	kgdb lock (kgdb_active)
+ *
+ * Note that since we can be in here prior to our cpumask being filled
+ * out, we err on the side of caution and loop over NR_CPUS instead
+ * of a for_each_online_cpu.
+ */
+int
+kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
+{
+	struct kgdb_state kgdb_var;
+	struct kgdb_state *ks = &kgdb_var;
+	unsigned long flags;
+	int error = 0;
+	int i, cpu;
+
+	ks->cpu			= raw_smp_processor_id();
+	ks->all_cpus_synced	= 0;
+	ks->ex_vector		= evector;
+	ks->signo		= signo;
+	ks->ex_vector		= evector;
+	ks->err_code		= ecode;
+	ks->kgdb_usethreadid	= 0;
+	ks->linux_regs		= regs;
+
+	if (kgdb_reenter_check(ks))
+		return 0; /* Ouch, double exception ! */
+
+acquirelock:
+	/*
+	 * Interrupts will be restored by the 'trap return' code, except when
+	 * single stepping.
+	 */
+	local_irq_save(flags);
+
+	cpu = raw_smp_processor_id();
+
+	/*
+	 * Being the process of declaring a master debug processor, the
+	 * goal is to have only one single processor set kgdb_active
+	 * to the number of the cpu + 1.  The atomic variable kgdb_sync is
+	 * used to control the selection.
+	 */
+	while (1) {
+		i = 25;	/* an arbitrary number */
+		if (atomic_read(&kgdb_sync) < 0 &&
+			atomic_inc_and_test(&kgdb_sync)) {
+			atomic_set(&kgdb_active, cpu + 1);
+			break;
+		}
+
+		while (--i)
+			cpu_relax();
+
+		if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
+				atomic_read(&kgdb_cpu_doing_single_step) != cpu)
+			udelay(1);
+	}
+
+	/*
+	 * Do not start the debugger connection on this CPU if the last
+	 * instance of the exception handler wanted to come into the
+	 * debugger on a different CPU via a single step
+	 */
+	if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
+	    atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
+
+		atomic_set(&kgdb_active, 0);
+		atomic_set(&kgdb_sync, -1);
+		local_irq_restore(flags);
+
+		goto acquirelock;
+	}
+
+	if (!kgdb_io_ready(1)) {
+		error = 1;
+		goto kgdb_restore; /* No I/O connection, so resume the system */
+	}
+
+	/*
+	 * Don't enter if we have hit a removed breakpoint.
+	 */
+	if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
+		goto kgdb_restore;
+
+	/* Call the I/O driver's pre_exception routine */
+	if (kgdb_io_ops->pre_exception)
+		kgdb_io_ops->pre_exception();
+
+	kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
+	kgdb_info[ks->cpu].task = current;
+
+	kgdb_disable_hw_debug(ks->linux_regs);
+
+	/*
+	 * Get the slave CPU lock which will hold all the non-master
+	 * CPU in a spin state while the debugger is active
+	 */
+	if (!kgdb_single_step || !kgdb_contthread) {
+		for (i = 0; i < NR_CPUS; i++)
+			spin_lock(&slave_cpu_locks[i]);
+	}
+
+#ifdef CONFIG_SMP
+	/* Signal the other CPUs to enter kgdb_wait() */
+	if (!kgdb_single_step || !kgdb_contthread)
+		kgdb_roundup_cpus(flags);
+#endif
+
+	/*
+	 * spin_lock code is good enough as a barrier so we don't
+	 * need one here:
+	 */
+	atomic_set(&cpu_in_kgdb[ks->cpu], 1);
+
+	/*
+	 * Wait a reasonable time for the other CPUs to be notified and
+	 * be waiting for us.  Very early on this could be imperfect
+	 * as num_online_cpus() could be 0.
+	 */
+	for (i = 0; i < ROUNDUP_WAIT; i++) {
+		int num = 0;
+		int n;
+
+		for (n = 0; n < NR_CPUS; n++) {
+			if (atomic_read(&cpu_in_kgdb[n]))
+				num++;
+		}
+		if (num >= num_online_cpus()) {
+			ks->all_cpus_synced = 1;
+			break;
+		}
+	}
+
+	/* Master processor is completely in the debugger */
+	kgdb_post_master_code(ks->linux_regs, ks->ex_vector, ks->err_code);
+	kgdb_deactivate_sw_breakpoints();
+	kgdb_single_step = 0;
+	kgdb_contthread = NULL;
+	exception_level = 0;
+
+	/* Talk to debugger with gdbserial protocol */
+	error = gdb_serial_stub(ks);
+
+	/* Call the I/O driver's post_exception routine */
+	if (kgdb_io_ops->post_exception)
+		kgdb_io_ops->post_exception();
+
+	kgdb_info[ks->cpu].debuggerinfo = NULL;
+	kgdb_info[ks->cpu].task = NULL;
+	atomic_set(&cpu_in_kgdb[ks->cpu], 0);
+
+	if (!kgdb_single_step || !kgdb_contthread) {
+		for (i = NR_CPUS-1; i >= 0; i--)
+			spin_unlock(&slave_cpu_locks[i]);
+		/*
+		 * Wait till all the CPUs have quit
+		 * from the debugger.
+		 */
+		for (i = 0; i < NR_CPUS; i++) {
+			while (atomic_read(&cpu_in_kgdb[i])) {
+				int j = 10;	/* an arbitrary number */
+
+				while (--j)
+					cpu_relax();
+			}
+		}
+	}
+
+#ifdef CONFIG_SMP
+	/*
+	 * This delay has a real purpose.  The problem is that if you
+	 * are single-stepping, you are sending an NMI to all the
+	 * other CPUs to stop them.  Interrupts come in, but don't get
+	 * handled.  Then you let them go just long enough to get into
+	 * their interrupt routines and use up some stack. You stop them
+	 * again, and then do the same thing.  After a while you blow
+	 * the stack on the other CPUs. This delay gives some time for
+	 * interrupts to be cleared out on the other CPUs.
+	 */
+	if (kgdb_single_step)
+		mdelay(2);
+#endif
+kgdb_restore:
+	/* Free kgdb_active */
+	atomic_set(&kgdb_active, 0);
+	atomic_set(&kgdb_sync, -1);
+	local_irq_restore(flags);
+
+	return error;
+}
+
+/*
+ * GDB places a breakpoint at this function to know dynamically
+ * loaded objects. It's not defined static so that only one instance with this
+ * name exists in the kernel.
+ */
+
+int module_event(struct notifier_block *self, unsigned long val, void *data)
+{
+	return 0;
+}
+
+static struct notifier_block kgdb_module_load_nb = {
+	.notifier_call	= module_event,
+};
+
+int kgdb_nmicallback(int cpu, void *regs)
+{
+#ifdef CONFIG_SMP
+	if (!atomic_read(&cpu_in_kgdb[cpu]) &&
+		atomic_read(&kgdb_active) != (cpu + 1)) {
+		kgdb_wait((struct pt_regs *)regs);
+		return 0;
+	}
+#endif
+	return 1;
+}
+
+/*
+ * This is called when a panic happens.  All we need to do is
+ * kgdb_breakpoint().
+ */
+static int
+kgdb_panic_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
+{
+	if (atomic_read(&kgdb_active) != 0) {
+		printk(KERN_ERR "KGDB: Cannot handle panic while"
+				"debugger active\n");
+		dump_stack();
+		return NOTIFY_DONE;
+	}
+	printk(KERN_ERR "kgdb panic point\n");
+	kgdb_breakpoint();
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block kgdb_panic_notifier = {
+	.notifier_call	= kgdb_panic_notify,
+};
+
+#ifdef CONFIG_KGDB_CONSOLE_OUTPUT
+
+void kgdb_console_write(struct console *co, const char *s, unsigned count)
+{
+	unsigned long flags;
+
+	/* If we're debugging, or KGDB has not connected, don't try
+	 * and print. */
+	if (!kgdb_connected || atomic_read(&kgdb_active) != 0)
+		return;
+
+	local_irq_save(flags);
+	kgdb_msg_write(s, count);
+	local_irq_restore(flags);
+}
+
+static struct console kgdbcons = {
+	.name		= "kgdb",
+	.write		= kgdb_console_write,
+	.flags		= CON_PRINTBUFFER | CON_ENABLED,
+	.index		= -1,
+}
+;
+#endif
+
+#ifdef CONFIG_MAGIC_SYSRQ
+static void sysrq_handle_gdb(int key, struct tty_struct *tty)
+{
+	if (!kgdb_io_ops) {
+		printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
+		return;
+	}
+	if (!kgdb_connected)
+		printk(KERN_CRIT "Entering KGDB\n");
+
+	kgdb_breakpoint();
+}
+
+static struct sysrq_key_op sysrq_gdb_op = {
+	.handler	= sysrq_handle_gdb,
+	.help_msg	= "Gdb",
+	.action_msg	= "GDB",
+};
+#endif
+
+static void kgdb_register_callbacks(void)
+{
+	if (!kgdb_io_module_registered) {
+		kgdb_io_module_registered = 1;
+		kgdb_arch_init();
+		atomic_notifier_chain_register(&panic_notifier_list,
+					&kgdb_panic_notifier);
+		register_module_notifier(&kgdb_module_load_nb);
+		register_reboot_notifier(&kgdb_reboot_notifier);
+#ifdef CONFIG_MAGIC_SYSRQ
+		register_sysrq_key('g', &sysrq_gdb_op);
+#endif
+#ifdef CONFIG_KGDB_CONSOLE_OUTPUT
+		/* Initialize the console registration */
+		register_console(&kgdbcons);
+#endif
+	}
+}
+
+static void kgdb_unregister_callbacks(void)
+{
+	/*
+	 * When this routine is called KGDB should unregister from the
+	 * panic handler and clean up, making sure it is not handling any
+	 * break exceptions at the time.
+	 */
+	if (kgdb_io_module_registered) {
+		kgdb_io_module_registered = 0;
+		kgdb_arch_uninit();
+		atomic_notifier_chain_unregister(&panic_notifier_list,
+					  &kgdb_panic_notifier);
+		unregister_module_notifier(&kgdb_module_load_nb);
+		unregister_reboot_notifier(&kgdb_reboot_notifier);
+#ifdef CONFIG_MAGIC_SYSRQ
+		unregister_sysrq_key('g', &sysrq_gdb_op);
+#endif
+#ifdef CONFIG_KGDB_CONSOLE_OUTPUT
+		/* Initialize the console registration */
+		unregister_console(&kgdbcons);
+#endif
+	}
+}
+
+static void kgdb_initial_breakpoint(void)
+{
+	kgdb_break_asap = 0;
+
+	printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
+	kgdb_breakpoint();
+}
+
+/**
+ *	kkgdb_register_io_module - register KGDB IO module
+ *	@new_kgdb_io_ops: the io ops vector
+ *
+ *	Register it with the KGDB core.
+ */
+int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
+{
+	int err;
+
+	spin_lock(&kgdb_registration_lock);
+
+	if (kgdb_io_ops) {
+		spin_unlock(&kgdb_registration_lock);
+
+		printk(KERN_ERR "kgdb: Another I/O driver is already "
+				"registered with KGDB.\n");
+		return -EBUSY;
+	}
+
+	if (new_kgdb_io_ops->init) {
+		err = new_kgdb_io_ops->init();
+		if (err) {
+			spin_unlock(&kgdb_registration_lock);
+			return err;
+		}
+	}
+
+	kgdb_io_ops = new_kgdb_io_ops;
+
+	spin_unlock(&kgdb_registration_lock);
+
+	printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
+	       new_kgdb_io_ops->name);
+
+	/* Arm KGDB now. */
+	kgdb_register_callbacks();
+
+	if (kgdb_break_asap)
+		kgdb_initial_breakpoint();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kgdb_register_io_module);
+
+/**
+ *	kkgdb_unregister_io_module - unregister KGDB IO module
+ *	@old_kgdb_io_ops: the io ops vector
+ *
+ *	Unregister it with the KGDB core.
+ */
+void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
+{
+	BUG_ON(kgdb_connected);
+
+	/*
+	 * KGDB is no longer able to communicate out, so
+	 * unregister our callbacks and reset state.
+	 */
+	kgdb_unregister_callbacks();
+
+	spin_lock(&kgdb_registration_lock);
+
+	WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
+	kgdb_io_ops = NULL;
+
+	spin_unlock(&kgdb_registration_lock);
+
+	printk(KERN_INFO
+		"kgdb: Unregistered I/O driver %s, debugger disabled.\n",
+		old_kgdb_io_ops->name);
+}
+EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
+
+/**
+ * kgdb_breakpoint - generate breakpoint exception
+ *
+ * This function will generate a breakpoint exception.  It is used at the
+ * beginning of a program to sync up with a debugger and can be used
+ * otherwise as a quick means to stop program execution and "break" into
+ * the debugger.
+ */
+void kgdb_breakpoint(void)
+{
+	atomic_set(&kgdb_setting_breakpoint, 1);
+	wmb(); /* Sync point before breakpoint */
+	arch_kgdb_breakpoint();
+	wmb(); /* Sync point after breakpoint */
+	atomic_set(&kgdb_setting_breakpoint, 0);
+}
+EXPORT_SYMBOL_GPL(kgdb_breakpoint);
+
+static int
+kgdb_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
+{
+	unsigned long flags;
+
+	/*
+	 * If we're debugging, or KGDB has not connected, don't try
+	 * and print:
+	 */
+	if (!kgdb_connected || atomic_read(&kgdb_active) != 0)
+		return 0;
+
+	if (code == SYS_RESTART || code == SYS_HALT || code == SYS_POWER_OFF) {
+		local_irq_save(flags);
+		put_packet("X00");
+		kgdb_connected = 0;
+		local_irq_restore(flags);
+	}
+	return NOTIFY_DONE;
+}
+
+static int __init opt_kgdb_wait(char *str)
+{
+	kgdb_break_asap = 1;
+
+	if (kgdb_io_module_registered)
+		kgdb_initial_breakpoint();
+
+	return 0;
+}
+
+early_param("kgdbwait", opt_kgdb_wait);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index d41ef6b..97a152c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -32,6 +32,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/kobject.h>
+#include <linux/pid.h>
 #include <linux/net.h>
 #include <linux/sysrq.h>
 #include <linux/highuid.h>
@@ -71,7 +72,6 @@ extern int max_threads;
 extern int core_uses_pid;
 extern int suid_dumpable;
 extern char core_pattern[];
-extern int pid_max;
 extern int min_free_kbytes;
 extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a370fe8..a904916 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -618,3 +618,5 @@ config PROVIDE_OHCI1394_DMA_INIT
 	  See Documentation/debugging-via-ohci1394.txt for more information.
 
 source "samples/Kconfig"
+
+source "lib/Kconfig.kgdb"
diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
new file mode 100644
index 0000000..a739e9d
--- /dev/null
+++ b/lib/Kconfig.kgdb
@@ -0,0 +1,40 @@
+
+menuconfig KGDB
+	bool "KGDB: kernel debugging with remote gdb"
+	select FRAME_POINTER
+	depends on HAVE_ARCH_KGDB
+	depends on DEBUG_KERNEL && EXPERIMENTAL
+	help
+	  If you say Y here, it will be possible to remotely debug the
+	  kernel using gdb.  Documentation of kernel debugger is available
+	  at http://kgdb.sourceforge.net as well as in DocBook form
+	  in Documentation/DocBook/.  If unsure, say N.
+
+config HAVE_ARCH_KGDB_SHADOW_INFO
+	bool
+
+config HAVE_ARCH_KGDB
+	bool
+
+config KGDB_CONSOLE_OUTPUT
+	bool "KGDB: Console messages through gdb"
+	depends on KGDB
+	help
+	  If you say Y here, console messages will appear through gdb.
+	  Other consoles such as tty or ttyS will continue to work as usual.
+	  Note that if you use this in conjunction with KGDBOE, if the
+	  ethernet driver runs into an error condition during use with KGDB,
+	  it is possible to hit an infinite recursion, causing the kernel
+	  to crash, and typically reboot.  For this reason, it is preferable
+	  to use NETCONSOLE in conjunction with KGDBOE instead of
+	  KGDB_CONSOLE.
+
+config KGDB_SERIAL_CONSOLE
+	tristate "KGDB: use kgdb over the serial console"
+	depends on KGDB
+	select CONSOLE_POLL
+	select MAGIC_SYSRQ
+	default y
+	help
+	  Share a serial console with kgdb. Sysrq-g must be used
+	  to break in initially.
diff --git a/mm/Makefile b/mm/Makefile
index 9f117ba..fb9e7ac 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -8,7 +8,7 @@ mmu-$(CONFIG_MMU)	:= fremap.o highmem.o madvise.o memory.o mincore.o \
 			   vmalloc.o
 
 obj-y			:= bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
-			   page_alloc.o page-writeback.o pdflush.o \
+			   maccess.o page_alloc.o page-writeback.o pdflush.o \
 			   readahead.o swap.o truncate.o vmscan.o \
 			   prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
 			   page_isolation.o $(mmu-y)
diff --git a/mm/maccess.c b/mm/maccess.c
new file mode 100644
index 0000000..24f81b9
--- /dev/null
+++ b/mm/maccess.c
@@ -0,0 +1,49 @@
+/*
+ * Access kernel memory without faulting.
+ */
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <linux/mm.h>
+
+/**
+ * probe_kernel_read(): safely attempt to read from a location
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from
+ * @size: size of the data chunk
+ *
+ * Safely read from address @src to the buffer at @dst.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+long probe_kernel_read(void *dst, void *src, size_t size)
+{
+	long ret;
+
+	pagefault_disable();
+	ret = __copy_from_user_inatomic(dst,
+			(__force const void __user *)src, size);
+	pagefault_enable();
+
+	return ret ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(probe_kernel_read);
+
+/**
+ * probe_kernel_write(): safely attempt to write to a location
+ * @dst: address to write to
+ * @src: pointer to the data that shall be written
+ * @size: size of the data chunk
+ *
+ * Safely write to address @dst from the buffer at @src.  If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+long probe_kernel_write(void *dst, void *src, size_t size)
+{
+	long ret;
+
+	pagefault_disable();
+	ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
+	pagefault_enable();
+
+	return ret ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(probe_kernel_write);

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