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KGTP (dynamic tracer for Linux kernel and applications) 20131218 release (support Uprobes to trace user applications)

From:  Hui Zhu <teawater@gmail.com>
To:  "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "gdb@sourceware.org" <gdb@sourceware.org>, kgtp <kgtp@freelists.org>
Subject:  KGTP (dynamic tracer for Linux kernel and applications) 20131218 release (support Uprobes to trace user applications)
Date:  Thu, 19 Dec 2013 12:07:39 +0800
Message-ID:  <52B2710B.8060107@gmail.com>
Cc:  Marc Khouzam <marc.khouzam@ericsson.com>, Thiago Jung Bauermann <thiago.bauermann@gmail.com>, Steven <mqyoung@gmail.com>, colyli@gmail.com, Christoph Hellwig <hch@infradead.org>, Geoff Levand <geoff@infradead.org>, Steven Rostedt <rostedt@goodmis.org>, Geunsik Lim <leemgs1@gmail.com>, "Andi Kleen" <andi@firstfloor.org>, "Tao Ma" <taoma.tm@gmail.com>, "Oliver Yang" <yangoliver@gmail.com>, "Dixon, Brad" <Brad_Dixon@mentor.com>
Archive-link:  Article

KGTP (http://kgtp.googlecode.com/) is a comprehensive dynamic tracer for
analysing Linux kernel and application (including Android) problems on
production systems in real time.
To use it, you don't need patch or rebuild the Linux kernel. Just build
KGTP module and insmod it is OK.
http://www.youtube.com/watch?v=7nfGAbNsEZY
or http://www.tudou.com/programs/view/fPu_koiKo38/ is the video that
introduced KGTP in English.
http://www.infoq.com/cn/presentations/gdb-sharp-knife-kgt...
is the video that introduced KGTP in Chinese.

Please goto https://code.google.com/p/kgtp/wiki/HOWTO (English)
or https://code.google.com/p/kgtp/wiki/HOWTOCN (Chinese) to get howto use KGTP.
Or download the pdf version in https://raw.github.com/teawater/kgtp/master/kgtp.pdf (English)
or https://raw.github.com/teawater/kgtp/master/kgtpcn.pdf(Chinese).

Now, KGTP 20131218 release.
To get it in github:
Get through https:
https://github.com/teawater/kgtp/archive/20131218.tar.gz
Get through git:
git clone https://github.com/teawater/kgtp.git
git checkout 20131218 -b 20131218

To get it in CSDN:
Get through https:
https://code.csdn.net/teawater/kgtp/repository/archive?re...
Get through git:
git clone git://code.csdn.net/teawater/kgtp.git
git checkout 20131218 -b 20131218

The main change of this release is:
Support Uprobes to trace user applications.  So now, you can use GDB
trace or access the memory of user applications through KGTP without
stop them like what KGTP can do with Linux kernel.  Please goto
https://code.google.com/p/kgtp/wiki/HOWTO#Use_KGTP_with_u...
get more info about howto use it.
Please goto https://github.com/teawater/kgtp/blob/20131218/UPDATE
get more info about this release.

The howto of KGTP doesn't introcue trace more than one user applications
or Linux kernel in same time.  This is because multiprocess support of
GDB tracepoint is not complete.  Without this support, KGTP need add
a special line in actions to support multiprocess tracepoint.  So I make
some patches for GDB to make it works:
https://sourceware.org/ml/gdb-patches/2013-12/msg00730.html
https://sourceware.org/ml/gdb-patches/2013-12/msg00731.html
https://sourceware.org/ml/gdb-patches/2013-12/msg00732.html
https://sourceware.org/ml/gdb-patches/2013-12/msg00733.html
Hope they can get review before GDB 7.7 release. Maybe I need add them
to https://code.google.com/p/gdbt/ first.
So in the next release of KGTP, GDB can very easy to trace user applications
and Linux kernel through KGTP in same time.

According to the comments of Christoph, Geoff and Andi.  I make KGTP
function lite patch for Linux kernel upstream.  Please goto
http://lkml.org/lkml/2013/11/21/7 to got it.
And I also post it with this mail.

Signed-off-by: Hui Zhu <teawater@gmail.com>
---
--- a/arch/arc/kernel/kgdb.c
+++ b/arch/arc/kernel/kgdb.c
@@ -61,6 +61,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	to_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
  		current->thread.callee_reg);
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
  {
--- a/arch/blackfin/kernel/kgdb.c
+++ b/arch/blackfin/kernel/kgdb.c
@@ -73,6 +73,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	gdb_regs[BFIN_EXTRA3] = 0;
  	gdb_regs[BFIN_IPEND] = regs->ipend;
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  /*
   * Extracts ebp, esp and eip values understandable by gdb from the values
--- a/arch/microblaze/kernel/kgdb.c
+++ b/arch/microblaze/kernel/kgdb.c
@@ -64,6 +64,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	__asm__ __volatile__ ("mfs %0, rtlbhi;" : "=r"(temp) : );
  	gdb_regs[GDB_RTLBHI] = temp;
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  {
--- a/arch/mn10300/kernel/kgdb.c
+++ b/arch/mn10300/kernel/kgdb.c
@@ -66,6 +66,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	gdb_regs[GDB_FR_DUMMY1]	= 0;
  	gdb_regs[GDB_FR_FS0]	= 0;
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  /*
   * Extracts kernel SP/PC values understandable by gdb from the values
--- a/arch/sparc/kernel/kgdb_32.c
+++ b/arch/sparc/kernel/kgdb_32.c
@@ -41,6 +41,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	gdb_regs[GDB_FSR] = 0;
  	gdb_regs[GDB_CSR] = 0;
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
  {
--- a/arch/sparc/kernel/kgdb_64.c
+++ b/arch/sparc/kernel/kgdb_64.c
@@ -37,6 +37,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  	gdb_regs[GDB_FPRS] = 0;
  	gdb_regs[GDB_Y] = regs->y;
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
  {
--- /dev/null
+++ b/arch/x86/include/asm/gtp.h
@@ -0,0 +1,16 @@
+#ifndef _ASM_X86_GTP_H_
+#define _ASM_X86_GTP_H_
+
+static inline void gtp_copy_and_adjuest_regs(struct pt_regs *dest,
+					     struct pt_regs *src)
+{
+	memcpy(dest, src, sizeof(struct pt_regs));
+
+#ifdef CONFIG_X86_32
+	dest->sp = (unsigned long)&src->sp;
+#endif	/* CONFIG_X86_32 */
+
+	dest->ip -= 1;
+}
+
+#endif
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -94,6 +94,8 @@ obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
  obj-$(CONFIG_JUMP_LABEL) += jump_label.o
  obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
  
+obj-$(CONFIG_GTP) += gtp.o
+
  $(obj)/configs.o: $(obj)/config_data.h
  
  # config_data.h contains the same information as ikconfig.h but gzipped.
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -258,6 +258,7 @@ char *kgdb_mem2hex(char *mem, char *buf,
  
  	return buf;
  }
+EXPORT_SYMBOL_GPL(kgdb_mem2hex);
  
  /*
   * Convert the hex array pointed to by buf into binary to be placed in
@@ -349,6 +350,7 @@ void pt_regs_to_gdb_regs(unsigned long *
  		idx += dbg_reg_def[i].size;
  	}
  }
+EXPORT_SYMBOL_GPL(pt_regs_to_gdb_regs);
  
  void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  {
--- /dev/null
+++ b/kernel/gtp.c
@@ -0,0 +1,876 @@
+/*
+ * KGTP is a realtime and lightweight Linux debugger and tracer.
+ * It makes Linux Kernel supply a GDB remote debug interface.
+ *
+ * Copyright(C) KGTP team (kgtp.googlecode.com), 2010-2013
+ *
+ */
+
+#include <linux/version.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/poll.h>
+#include <linux/kprobes.h>
+#include <linux/interrupt.h>
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/kgdb.h>
+#include <asm/gtp.h>
+
+#define GTP_RW_MAX		16384
+#define GTP_RW_BUFP_MAX		(GTP_RW_MAX - 4 - gtp_rw_size)
+
+#define GTP_FRAME_SIZE		5242880
+#define GTP_FRAME_HEAD_SIZE	(1 + sizeof(struct gtp_frame_head))
+#define GTP_FRAME_REG_SIZE	(1 + sizeof(struct gtp_frame_reg))
+
+#define TOHEX(h)		((h) > 9 ? (h) + 'a' - 10 : (h) + '0')
+
+struct action {
+	struct list_head	node;
+	char			type;
+	union {
+		uint64_t	reg_mask;
+	} u;
+};
+
+struct gtp_entry {
+	struct list_head	node;
+	uint64_t		num;
+	uint64_t		addr;
+	uint64_t		step;
+	uint64_t		pass;
+	int			nopass;
+	int			kpreg;
+	struct kprobe		kp;
+	struct list_head	action_list;
+};
+
+static LIST_HEAD(gtp_list);
+
+struct gtp_frame_head {
+	int		frame_num;
+	uint64_t	trace_num;
+	char		*next;
+};
+
+struct gtp_frame_reg {
+	struct pt_regs	regs;
+	char		*next;
+};
+
+static char			gtp_read_ack;
+static char			*gtp_rw_buf;
+static char			*gtp_rw_bufp;
+static size_t			gtp_rw_size;
+
+static int			gtp_start;
+
+static int			gtp_circular;
+
+static DEFINE_SPINLOCK(gtp_frame_lock);
+static int			gtp_frame_num;
+static char			*gtp_frame;
+static char			*gtp_frame_r_start;
+static char			*gtp_frame_w_start;
+static char			*gtp_frame_w_end;
+static char			*gtp_frame_r_cache;
+static int			gtp_frame_is_circular;
+static struct gtp_frame_head	*gtp_frame_current;
+
+static DEFINE_SEMAPHORE(gtp_rw_lock);
+static int	gtp_rw_count;
+
+static char *gtp_frame_alloc(size_t size)
+{
+	char	*ret = NULL;
+
+	if (size > GTP_FRAME_SIZE)
+		return NULL;
+
+	spin_lock(&gtp_frame_lock);
+
+	if (gtp_frame_w_start + size > gtp_frame_w_end) {
+		if (gtp_circular) {
+			gtp_frame_is_circular = 1;
+			gtp_frame_w_start = gtp_frame;
+			gtp_frame_r_start = gtp_frame;
+		} else
+			goto out;
+	}
+
+	if (gtp_frame_is_circular) {
+		/* Release some frame entry to get some place.
+		   When support new frame type, need add new handler
+		   to switch.  */
+		while (gtp_frame_w_start + size > gtp_frame_r_start) {
+			switch (gtp_frame_r_start[0]) {
+			case 'h':
+				gtp_frame_r_start += GTP_FRAME_HEAD_SIZE;
+				break;
+			case 'r':
+				gtp_frame_r_start += GTP_FRAME_REG_SIZE;
+				break;
+			default:
+				goto out;
+			}
+		}
+	}
+
+	ret = gtp_frame_w_start;
+	gtp_frame_w_start += size;
+
+out:
+	spin_unlock(&gtp_frame_lock);
+	return ret;
+}
+
+static inline char **gtp_action_r(struct pt_regs *regs, struct action *ae,
+				  char **next)
+{
+	struct gtp_frame_reg	*freg;
+	char			*tmp;
+
+	tmp = gtp_frame_alloc(GTP_FRAME_REG_SIZE);
+	if (!tmp)
+		return NULL;
+
+	*next = tmp;
+	tmp[0] = 'r';
+	freg = (struct gtp_frame_reg *) (tmp + 1);
+	gtp_copy_and_adjuest_regs(&freg->regs, regs);
+	freg->next = NULL;
+
+	return &freg->next;
+}
+
+static int gtp_kp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct gtp_entry	*tpe = container_of(p, struct gtp_entry, kp);
+	struct gtp_frame_head	*head;
+	char			*tmp;
+	struct action		*ae;
+	struct list_head	*cur;
+	char			**next;
+
+	pr_devel("gtp_kp_pre_handler: tracepoint %d\n", (int)tpe->num);
+
+	/* Get the head.  */
+	tmp = gtp_frame_alloc(GTP_FRAME_HEAD_SIZE);
+	if (!tmp)
+		goto no_memory;
+	tmp[0] = 'h';
+	head = (struct gtp_frame_head *) (tmp + 1);
+	/* Get a new frame num from gtp_frame_num.  */
+	spin_lock(&gtp_frame_lock);
+	if (gtp_frame_num < 0)
+		gtp_frame_num = head->frame_num = 0;
+	else
+		head->frame_num = gtp_frame_num++;
+	spin_unlock(&gtp_frame_lock);
+	head->trace_num = tpe->num;
+	head->next = NULL;
+	next = &head->next;
+
+	/* Handle actions.  */
+	list_for_each(cur, &tpe->action_list) {
+		ae = list_entry(cur, struct action, node);
+		switch (ae->type) {
+		case 'r':
+			next = gtp_action_r(regs, ae, next);
+			if (!next)
+				goto no_memory;
+			break;
+		}
+	}
+
+	return 0;
+
+no_memory:
+	pr_devel("gtp_kp_pre_handler: tracepoint %d no memory.\n",
+		 (int)tpe->num);
+	return 0;
+}
+
+static struct action *gtp_action_alloc(char type)
+{
+	struct action	*ret;
+
+	ret = kzalloc(sizeof(struct action), GFP_KERNEL);
+	if (!ret)
+		goto out;
+
+	ret->type = type;
+
+out:
+	return ret;
+}
+
+static struct gtp_entry *gtp_list_add(uint64_t num, uint64_t addr)
+{
+	struct gtp_entry	*ret = kzalloc(sizeof(struct gtp_entry),
+					       GFP_KERNEL);
+
+	if (!ret)
+		goto out;
+	ret->num = num;
+	ret->addr = addr;
+	ret->kp.addr = (kprobe_opcode_t *) (unsigned long)addr;
+	ret->kp.pre_handler = gtp_kp_pre_handler;
+	INIT_LIST_HEAD(&ret->action_list);
+
+	list_add(&ret->node, &gtp_list);
+
+out:
+	return ret;
+}
+
+static struct gtp_entry *gtp_list_find(uint64_t num, uint64_t addr)
+{
+	struct gtp_entry	*tpe;
+	struct list_head	*cur;
+
+	list_for_each(cur, &gtp_list) {
+		tpe = list_entry(cur, struct gtp_entry, node);
+		if (tpe->num == num && tpe->addr == addr)
+			return tpe;
+	}
+
+	return NULL;
+}
+
+static void gtp_list_release(void)
+{
+	struct gtp_entry	*tpe;
+	struct list_head	*cur, *next;
+
+	list_for_each_safe(cur, next, &gtp_list) {
+		struct action		*ae;
+		struct list_head	*cur_ae, *next_ae;
+
+		tpe = list_entry(cur, struct gtp_entry, node);
+
+		list_for_each_safe(cur_ae, next_ae, &tpe->action_list) {
+			ae = list_entry(cur_ae, struct action, node);
+			kfree(ae);
+		}
+
+		kfree(tpe);
+	}
+}
+
+static void gtp_frame_reset(void)
+{
+	gtp_frame_num = 0;
+	gtp_frame_r_start = gtp_frame;
+	gtp_frame_w_start = gtp_frame;
+	gtp_frame_w_end = gtp_frame + GTP_FRAME_SIZE;
+	gtp_frame_is_circular = 0;
+	gtp_frame_r_cache = NULL;
+	gtp_frame_current = NULL;
+}
+
+static int gtp_gdbrsp_qtinit(char *pkg)
+{
+	gtp_list_release();
+
+	if (gtp_frame)
+		gtp_frame_reset();
+
+	return 0;
+}
+
+static int gtp_gdbrsp_qtdp(char *pkg)
+{
+	int			addnew = 1;
+	uint64_t		num, addr;
+	struct gtp_entry	*tpe;
+
+	pr_devel("gtp_gdbrsp_qtdp: %s\n", pkg);
+
+	if (pkg[0] == '-') {
+		pkg++;
+		addnew = 0;
+	}
+
+	/* Get num and addr.  */
+	if (pkg[0] == '\0')
+		return -EINVAL;
+	num = simple_strtoull(pkg, &pkg, 16);
+	if (pkg[0] == '\0')
+		return -EINVAL;
+	pkg++;
+	addr = simple_strtoull(pkg, &pkg, 16);
+	if (pkg[0] == '\0')
+		return -EINVAL;
+	pkg++;
+
+	tpe = gtp_list_find(num, addr);
+	if (addnew) {
+		if (tpe)
+			return -EINVAL;
+		if (pkg[0] == 'D')
+			return 0;
+		if (pkg[0] == '\0')
+			return -EINVAL;
+		pkg++;
+
+		tpe = gtp_list_add(num, addr);
+		if (tpe == NULL)
+			return -ENOMEM;
+
+		/* Get step and pass.  */
+		if (pkg[0] == '\0')
+			return -EINVAL;
+		pkg++;
+		tpe->step = simple_strtoull(pkg, &pkg, 16);
+		if (pkg[0] == '\0')
+			return -EINVAL;
+		pkg++;
+		tpe->pass = simple_strtoull(pkg, &pkg, 16);
+		if (tpe->pass == 0)
+			tpe->nopass = 1;
+	} else if (tpe) {
+		/* Add action to tpe.  */
+		int	step_action = 0;
+
+		if (pkg[0] == 'S') {
+			pkg++;
+			step_action = 1;
+			/* Do not support step now.  */
+			return 1;
+		}
+		while (pkg[0]) {
+			struct action	*ae;
+
+			switch (pkg[0]) {
+			case 'R':
+				/* reg_mask is ignore because buffer just
+				   can record all regs.  */
+				ae = gtp_action_alloc(pkg[0]);
+				if (!ae)
+					return -ENOMEM;
+				pkg++;
+				ae->type = 'r';
+				ae->u.reg_mask = simple_strtoull(pkg, &pkg,
+								 16);
+				break;
+			default:
+				return 1;
+			}
+
+			if (ae)
+				list_add(&ae->node, &tpe->action_list);
+		}
+	} else
+		return -EINVAL;
+
+	return 0;
+}
+
+static int gtp_gdbrsp_qtdisconnected(char *pkg)
+{
+	/* Doesn't support disconnected-tracing.  */
+
+	return 1;
+}
+
+static int gtp_gdbrsp_qtbuffer(char *pkg)
+{
+	if (strncmp("circular:", pkg, 9) == 0) {
+		uint64_t setting;
+
+		pkg += 9;
+		if (pkg[0] == '\0')
+			return -EINVAL;
+		setting = simple_strtoull(pkg, NULL, 16);
+		gtp_circular = (int)setting;
+
+		return 0;
+	}
+
+	return 1;
+}
+
+static struct gtp_frame_head *gtp_frame_head_find(int num)
+{
+	struct gtp_frame_head	*ret = NULL;
+	char			*tmp;
+
+	if (gtp_frame_r_cache) {
+		tmp = gtp_frame_r_cache;
+
+		while (tmp < gtp_frame_w_start) {
+			switch (tmp[0]) {
+			case 'h':
+				ret = (struct gtp_frame_head *)(tmp + 1);
+				goto cache_check;
+				break;
+			case 'r':
+				tmp += GTP_FRAME_REG_SIZE;
+				break;
+			default:
+				goto cache_check;
+				break;
+			}
+		}
+
+cache_check:
+		if (ret && ret->frame_num == num)
+			goto out;
+	}
+
+	tmp = gtp_frame_r_start;
+	while (tmp < gtp_frame_w_start) {
+		switch (tmp[0]) {
+		case 'h':
+			ret = (struct gtp_frame_head *) (tmp + 1);
+			if (ret->frame_num == num)
+				goto out;
+			ret = NULL;
+			tmp += GTP_FRAME_HEAD_SIZE;
+			break;
+		case 'r':
+			tmp += GTP_FRAME_REG_SIZE;
+			break;
+		default:
+			goto out;
+		}
+	}
+
+out:
+	return ret;
+}
+
+static int gtp_gdbrsp_qtframe(char *pkg)
+{
+	if (strncmp(pkg, "pc:", 3) == 0)	/* Not support.  */
+		return 1;
+	else if (strncmp(pkg, "tdp:", 4) == 0)	/* Not support.  */
+		return 1;
+	else if (strncmp(pkg, "range:", 6) == 0)	/* Not support.  */
+		return 1;
+	else if (strncmp(pkg, "outside:", 8) == 0)	/* Not support.  */
+		return 1;
+	else {
+		uint64_t		num;
+		struct gtp_frame_head	*ret;
+
+		if (pkg[0] == '\0')
+			return -EINVAL;
+		num = simple_strtoull(pkg, NULL, 16);
+
+		pr_devel("gtp_gdbrsp_qtframe: %d\n", (int) num);
+
+		if (((int) num) < 0) {
+			/* Return to current.  */
+			gtp_frame_current = NULL;
+
+			return 0;
+		}
+		ret = gtp_frame_head_find((int) num);
+		if (ret) {
+			gtp_frame_current = ret;
+			gtp_frame_r_cache = (char *)ret;
+			gtp_frame_r_cache += sizeof(struct gtp_frame_head);
+			sprintf(gtp_rw_bufp, "F%xT%x",
+				gtp_frame_current->frame_num,
+				(unsigned int)gtp_frame_current->trace_num);
+			gtp_rw_size += strlen(gtp_rw_bufp);
+			gtp_rw_bufp += strlen(gtp_rw_bufp);
+		} else {
+			strcpy(gtp_rw_bufp, "F-1");
+			gtp_rw_bufp += 3;
+			gtp_rw_size += 3;
+		}
+	}
+
+	return 1;
+}
+
+static int gtp_gdbrsp_qtstop(char *pkg)
+{
+	struct gtp_entry	*tpe;
+	struct list_head	*cur;
+
+	if (!gtp_start)
+		return -EBUSY;
+
+	list_for_each(cur, &gtp_list) {
+		tpe = list_entry(cur, struct gtp_entry, node);
+		if (tpe->kpreg) {
+			unregister_kprobe(&tpe->kp);
+			tpe->kpreg = 0;
+		}
+	}
+
+	gtp_start = 0;
+
+	return 0;
+}
+
+static int gtp_gdbrsp_qtstart(char *pkg)
+{
+	struct gtp_entry	*tpe;
+	struct list_head	*cur;
+
+	if (!gtp_frame) {
+		gtp_frame = vmalloc(GTP_FRAME_SIZE);
+		if (!gtp_frame)
+			return -ENOMEM;
+
+		gtp_frame_reset();
+	}
+
+	list_for_each(cur, &gtp_list) {
+		tpe = list_entry(cur, struct gtp_entry, node);
+		if (!list_empty(&tpe->action_list)) {
+			int	ret = register_kprobe(&tpe->kp);
+			if (ret < 0) {
+				gtp_gdbrsp_qtstop(NULL);
+				return ret;
+			}
+			tpe->kpreg = 1;
+		}
+	}
+
+	gtp_start = 1;
+
+	return 0;
+}
+
+struct QTpkg_s {
+	const char	*header;
+
+	/* If size is bigger than 0, this is the size of package's header.
+	   And this package has some data after header need send to fun.
+	   If size is 0, this package just has a header.  */
+	int		size;
+
+	/* If check_start is true, before call fun, need check if gtp_start.
+	   If gtp_start, then return -EBUSY.  */
+	int		check_start;
+
+	int		(*fun)(char *pkg);
+};
+
+struct QTpkg_s QTpkgs[] = {
+	{"init", 		0, 1,	gtp_gdbrsp_qtinit},
+	{"DP:",			3, 1,	gtp_gdbrsp_qtdp},
+	{"Disconnected:",	13, 0,	gtp_gdbrsp_qtdisconnected},
+	{"Buffer:",		7, 0,	gtp_gdbrsp_qtbuffer},
+	{"Frame:",		6, 1,	gtp_gdbrsp_qtframe},
+	{"Start",		0, 1,	gtp_gdbrsp_qtstart},
+	{"Stop",			0, 0,	gtp_gdbrsp_qtstop},
+};
+
+static int gtp_gdbrsp_QT(char *pkg)
+{
+	int	ret = 1;
+	int	i;
+
+	pr_devel("gtp_gdbrsp_QT: %s\n", pkg);
+
+	for (i = 0; i < sizeof (QTpkgs) / sizeof (struct QTpkg_s); i++) {
+		int	not_same;
+
+		if (QTpkgs[i].size == 0)
+			not_same = strcmp(QTpkgs[i].header, pkg);
+		else
+			not_same = strncmp(QTpkgs[i].header, pkg,
+					       QTpkgs[i].size);
+		if (not_same)
+			continue;
+		if (QTpkgs[i].check_start && gtp_start)
+			ret = -EBUSY;
+		else
+			ret =  QTpkgs[i].fun(pkg + QTpkgs[i].size);
+	}
+
+	return ret;
+}
+
+static unsigned char	gtp_m_buffer[0xffff];
+
+static int gtp_gdbrsp_m(char *pkg)
+{
+	int		i;
+	uint64_t	addr, len;
+
+	/* Get add and len.  */
+	if (pkg[0] == '\0')
+		return -EINVAL;
+	addr = simple_strtoull(pkg, &pkg, 16);
+	if (pkg[0] != ',')
+		return -EINVAL;
+	pkg++;
+	len = simple_strtoull(pkg, &pkg, 16);
+	if (len == 0)
+		return -EINVAL;
+	len &= 0xffff;
+	len = (uint64_t) min((int)(GTP_RW_BUFP_MAX / 2),
+			     (int)len);
+
+	pr_devel("gtp_gdbrsp_m: addr = 0x%lx len = %d\n",
+		 (unsigned long) addr, (int) len);
+
+	if (probe_kernel_read(gtp_m_buffer, (void *)(unsigned long)addr,
+			      (size_t)len))
+		return -EFAULT;
+
+	for (i = 0; i < (int)len; i++) {
+		sprintf(gtp_rw_bufp, "%02x", gtp_m_buffer[i]);
+		gtp_rw_bufp += 2;
+		gtp_rw_size += 2;
+	}
+
+	return 1;
+}
+
+static int gtp_gdbrsp_g(void)
+{
+	char			*next;
+	struct gtp_frame_reg	*fr = NULL;
+
+	if (GTP_RW_BUFP_MAX < NUMREGBYTES * 2)
+		return -E2BIG;
+
+	if (gtp_start || !gtp_frame_current)
+		goto empty_out;
+
+	/* Get the fr.  */
+	next = gtp_frame_current->next;
+	if (next[0] == 'r') {
+		unsigned long		gdb_regs[(NUMREGBYTES +
+					sizeof(unsigned long) - 1) /
+					sizeof(unsigned long)];
+		fr = (struct gtp_frame_reg *) (next + 1);
+		pt_regs_to_gdb_regs(gdb_regs, &fr->regs);
+		kgdb_mem2hex((char *)gdb_regs, gtp_rw_bufp, NUMREGBYTES);
+	} else {
+empty_out:
+		memset(gtp_rw_bufp, '0', NUMREGBYTES * 2);
+	}
+	gtp_rw_bufp += NUMREGBYTES * 2;
+	gtp_rw_size += NUMREGBYTES * 2;
+	return 1;
+}
+
+static int gtp_open(struct inode *inode, struct file *file)
+{
+	int	ret = 0;
+
+	down(&gtp_rw_lock);
+
+	if (gtp_rw_count > 0) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	gtp_read_ack = 0;
+	gtp_rw_buf = vmalloc(GTP_RW_MAX);
+	if (!gtp_rw_buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	gtp_rw_count++;
+
+out:
+	up(&gtp_rw_lock);
+	return ret;
+}
+
+static int gtp_release(struct inode *inode, struct file *file)
+{
+	down(&gtp_rw_lock);
+	vfree(gtp_rw_buf);
+
+	gtp_gdbrsp_qtstop(NULL);
+	gtp_gdbrsp_qtinit(NULL);
+	vfree(gtp_frame);
+	gtp_frame = NULL;
+
+	gtp_rw_count--;
+
+	up(&gtp_rw_lock);
+
+	return 0;
+}
+
+static long gtp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	/* This function will make GDB happy.  */
+	pr_devel("gtp_ioctl: %x\n", cmd);
+
+	return 0;
+}
+
+static ssize_t gtp_write(struct file *file, const char __user *buf,
+			 size_t size, loff_t *ppos)
+{
+	char		*rsppkg = NULL;
+	int		i, ret;
+	unsigned char	csum = 0;
+
+	down(&gtp_rw_lock);
+
+	size = min_t(size_t, size, GTP_RW_MAX);
+	if (copy_from_user(gtp_rw_buf, buf, size)) {
+		size = -EFAULT;
+		goto out;
+	}
+
+	if (gtp_rw_buf[0] == '+' || gtp_rw_buf[0] == '-'
+	    || gtp_rw_buf[0] == '\3')
+		goto out;
+
+	/* Check format and crc and get the rsppkg.  */
+	for (i = 0; i < size - 2; i++) {
+		if (rsppkg == NULL) {
+			if (gtp_rw_buf[i] == '$')
+				rsppkg = gtp_rw_buf + i + 1;
+		} else {
+			if (gtp_rw_buf[i] == '#')
+				break;
+			else
+				csum += gtp_rw_buf[i];
+		}
+	}
+	if (rsppkg && gtp_rw_buf[i] == '#') {
+		/* Format is OK.  Check crc.  */
+		unsigned char	c1, c2;
+
+		gtp_rw_buf[i] = '\0';
+
+		c1 = gtp_rw_buf[i+1];
+		c2 = gtp_rw_buf[i+2];
+		if (csum == (c1 << 4) + c2) {
+			pr_devel("gtp_write: crc error\n");
+			gtp_read_ack = '-';
+			goto out;
+		}
+	} else {
+		pr_devel("gtp_write: format error\n");
+		gtp_read_ack = '-';
+		goto out;
+	}
+	gtp_read_ack = '+';
+
+	pr_devel("gtp_write: %s\n", rsppkg);
+
+	/* Handle rsppkg and put return to gtp_rw_buf.  */
+	gtp_rw_buf[0] = '$';
+	gtp_rw_bufp = gtp_rw_buf + 1;
+	gtp_rw_size = 0;
+	ret = 1;
+	switch (rsppkg[0]) {
+	case '?':
+		strcpy(gtp_rw_bufp, "S05");
+		gtp_rw_bufp += 3;
+		gtp_rw_size += 3;
+		break;
+	case 'g':
+		ret = gtp_gdbrsp_g();
+		break;
+	case 'm':
+		ret = gtp_gdbrsp_m(rsppkg + 1);
+		break;
+	case 'Q':
+		if (rsppkg[1] == 'T')
+			ret = gtp_gdbrsp_QT(rsppkg + 2);
+		break;
+	}
+	if (ret == 0) {
+		strcpy(gtp_rw_bufp, "OK");
+		gtp_rw_bufp += 2;
+		gtp_rw_size += 2;
+	} else if (ret < 0) {
+		sprintf(gtp_rw_bufp, "E%02x", -ret);
+		gtp_rw_bufp += 3;
+		gtp_rw_size += 3;
+	}
+
+	gtp_rw_bufp[0] = '#';
+	csum = 0;
+	for (i = 1; i < gtp_rw_size + 1; i++)
+		csum += gtp_rw_buf[i];
+	gtp_rw_bufp[1] = TOHEX(csum >> 4);
+	gtp_rw_bufp[2] = TOHEX(csum & 0x0f);
+	gtp_rw_bufp = gtp_rw_buf;
+	gtp_rw_size += 4;
+
+out:
+	up(&gtp_rw_lock);
+	return size;
+}
+
+static ssize_t gtp_read(struct file *file, char __user *buf, size_t size,
+	 loff_t *ppos)
+{
+	if (size == 0)
+		return 0;
+
+	down(&gtp_rw_lock);
+
+	if (gtp_read_ack) {
+		int err = put_user(gtp_read_ack, buf);
+		if (err) {
+			size = -err;
+			goto out;
+		}
+		gtp_read_ack = 0;
+		size = 1;
+		goto out;
+	}
+
+	size = min(gtp_rw_size, size);
+
+	if (copy_to_user(buf, gtp_rw_bufp, size)) {
+		size = -EFAULT;
+		goto out;
+	}
+	gtp_rw_bufp += size;
+	gtp_rw_size -= size;
+
+out:
+	up(&gtp_rw_lock);
+	return size;
+}
+
+static const struct file_operations gtp_operations = {
+	.owner		= THIS_MODULE,
+	.open		= gtp_open,
+	.release	= gtp_release,
+	.unlocked_ioctl	= gtp_ioctl,
+	.compat_ioctl	= gtp_ioctl,
+	.read		= gtp_read,
+	.write		= gtp_write,
+};
+
+struct dentry	*gtp_dir;
+
+static int __init gtp_init(void)
+{
+	gtp_dir = debugfs_create_file("gtp",
+				      S_IFREG | S_IRUSR | S_IWUSR,
+				      NULL, NULL, &gtp_operations);
+	if (gtp_dir == NULL || gtp_dir == ERR_PTR(-ENODEV))
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void __exit gtp_exit(void)
+{
+	if (gtp_dir)
+		debugfs_remove_recursive(gtp_dir);
+}
+
+module_init(gtp_init)
+module_exit(gtp_exit)
+
+MODULE_AUTHOR("Hui Zhu <teawater@gmail.com>");
+MODULE_LICENSE("GPL");
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1578,6 +1578,21 @@ config DMA_API_DEBUG
  	  This option causes a performance degredation.  Use only if you want
  	  to debug device drivers. If unsure, say N.
  
+config GTP
+	tristate "KGTP"
+	depends on X86
+	select KPROBES
+	select DEBUG_FS
+	select KGDB
+	---help---
+	  KGTP is a flexible, lightweight and realtime Linux (include
+	  Android) debugger and tracer.
+	  It makes Linux Kernel supply a GDB remote debug interface.
+	  Then GDB in current machine or remote machine can debug and
+	  trace Linux kernel and user space program through GDB tracepoint
+	  and some other functions without stopping the Linux Kernel.
+	  http://kgtp.googlecode.com/
+
  source "samples/Kconfig"
  
  source "lib/Kconfig.kgdb"
--
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