Re: [PATCH]KGTP (Linux Kernel debugger and tracer) lite patch for review

[Hui Zhu <teawater@gmail.com>]

Hi Andi,

Thanks for your help.
Sorry for late so much time.

On Thu, May 24, 2012 at 11:07 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> I remove them from asm files, and add:
>> #ifndef ULONGEST
>> #define ULONGEST              uint64_t
>> #endif
>> #ifndef CORE_ADDR
>> #define CORE_ADDR             unsigned long
>> #endif
>> in gtp.c
>> Then if not need, the arch didn't define ULONGEST and CORE_ADDR for itself.
>
> Which architecture needs it? Linux prefers to use "native" types.

I removed all of ULONGEST and CORE_ADDR.

>
>> For example ARM and MIPS have a lot of special reg that cannot be converted
>> by a for loop.
>>
>> After check the code the kgdb, I thought that good ways is use dbg_reg_def
>> of kgdb to convert the reg to gdb rsp format.  But use it directly will
>> make kgtp depend on kgdb.
>
> That's fine. Code reuse is good. Code duplication is bad.
>
>> What I thought is move this part of code out from kgdb, when kgdb or kgtp
>> need, select it too.  But I am not sure Jason is OK with that.
>
> Just send a patch.

I removed the GTP_REG_ASCII_SIZE and gtp_regs2ascii.
Now, to convert pt_reg to gdb format, KGTP use:
pt_regs_to_gdb_regs(gdb_regs, &fr->regs);
kgdb_mem2hex((char *)gdb_regs, gtp_rw_bufp, NUMREGBYTES);

>
>> >
>> >>+     memcpy(&freg->regs, regs, sizeof(struct pt_regs));
>> >>+#ifdef CONFIG_X86_32
>> >>+     freg->regs.sp = (unsigned long)&regs->sp;
>> >>+#endif       /* CONFIG_X86_32 */
>> >>+#ifdef CONFIG_X86
>> >>+     freg->regs.ip -= 1;
>> >>+#endif       /* CONFIG_X86 */
>> >
>> >What is that for? - 1?
>>
>> That is because when kprobe, the ip of X86 point will have a offset with
>> current ip.
>
> But a kprobe is not necessarily one byte. e.g. a jumper probe is longer.
>
> Anyways if that is really needed there should be some macros provided
> by kprobes to adjust IP. If it's not there it needs to be added.

I changed this part to a function gtp_copy_and_adjuest_regs.

>> >>+
>> >>+     if (gtp_start)
>> >>+             return -EBUSY;
>> >
>> >This is in a lot of places. Can you put it somewhere more central?
>>
>> Sorry I don't understand this part.  Do you want I change all "struct
>> gtp_entry        *tpe;" to "struct gtp_entry *tpe;"?
>
> I mean the if (gtp_start) return -EBUSY check.
>
>> >
>> >>+     pr_devel("gtp_gdbrsp_QT: %s\n", pkg);
>> >>+
>> >>+     if (strcmp("init", pkg) == 0)
>> >>+             ret = gtp_gdbrsp_qtinit();
>> >
>> >This if cascade should be probably a table walk
>>
>> I cannot find the examle about it in the Kernel, could you give me a
>> example?
>
>
> struct cmd {
>         char *name;
>         int (*init)(void);
> };
>
> struct cmd cmds[] = {
>         { "init", gtp_xyz_init }
>         ...
>         {}
> };
>
> int i;
> for (i = 0; cmds[i].name; i++)
>         if (!strcmp(cmds[i].name, pkg))
>                 ret = cmds->init();
>

OK.  I change gtp_gdbrsp_QT to this format and merge "return -EBUSY" to it together.

>
>> >Ok so what lock protects this buffer?
>>
>> No.  The gtp_frame_lock protects the vars that follow it:
>> 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;
>> It protects them all.
>>
>> gtp_m_buffer is protected by gtp_rw_lock that I just add in new patch.
>
> Then your comment was wrong/unclear?

This comment is not OK.  So I removed it.

>
>>
>>
>> OK.  Add some introduce.  checkpatch is OK with it.
>
> You must be using an old version?
>
> # check for Kconfig help text having a real description
> # Only applies when adding the entry originally, after that we do not have
> # sufficient context to determine whether it is indeed long enough.
> ...
>         WARN("CONFIG_DESCRIPTION",
>                              "please write a paragraph that describes the config symbol fully\n" . $herecurr) if ($is_start && $is_end && $length < 4);
>
> I wonder how you avoided that.


I am not sure.  I checked my checkpatch.py and it has check for description.
My desciption is:
+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/

I post a new version patch.
Please help me review it.

Thanks,
Hui

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
@@ -93,6 +93,8 @@ 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"