kernel/debug/gdbstub.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  * Kernel Debug Core
  *
  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
  *
  * Copyright (C) 2000-2001 VERITAS Software Corporation.
  * Copyright (C) 2002-2004 Timesys Corporation
  * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
  * Copyright (C) 2004 Pavel Machek <pavel@suse.cz>
  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
  * Copyright (C) 2005-2009 Wind River Systems, Inc.
  * Copyright (C) 2007 MontaVista Software, Inc.
  * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  *
  * Contributors at various stages not listed above:
  *  Jason Wessel ( jason.wessel@windriver.com )
  *  George Anzinger <george@mvista.com>
  *  Anurekh Saxena (anurekh.saxena@timesys.com)
  *  Lake Stevens Instrument Division (Glenn Engel)
  *  Jim Kingdon, Cygnus Support.
  *
  * Original KGDB stub: David Grothe <dave@gcom.com>,
  * Tigran Aivazian <tigran@sco.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/kernel.h>
 #include <linux/kgdb.h>
 #include <linux/reboot.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
 #include <asm/unaligned.h>
 #include "debug_core.h"

 #define KGDB_MAX_THREAD_QUERY 17

 /* 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)];

 /*
  * GDB remote protocol parser:
  */

 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 = (dbg_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 = dbg_io_ops->read_char();
 			if (ch == '#')
 				break;
 			checksum = checksum + ch;
 			buffer[count] = ch;
 			count = count + 1;
 		}
 		buffer[count] = 0;

 		if (ch == '#') {
 			xmitcsum = hex(dbg_io_ops->read_char()) << 4;
 			xmitcsum += hex(dbg_io_ops->read_char());

 			if (checksum != xmitcsum)
 				/* failed checksum */
 				dbg_io_ops->write_char('-');
 			else
 				/* successful transfer */
 				dbg_io_ops->write_char('+');
 			if (dbg_io_ops->flush)
 				dbg_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;

 	/*
 	 * $<packet info>#<checksum>.
 	 */
 	while (1) {
 		dbg_io_ops->write_char('$');
 		checksum = 0;
 		count = 0;

 		while ((ch = buffer[count])) {
 			dbg_io_ops->write_char(ch);
 			checksum += ch;
 			count++;
 		}

 		dbg_io_ops->write_char('#');
 		dbg_io_ops->write_char(hex_asc_hi(checksum));
 		dbg_io_ops->write_char(hex_asc_lo(checksum));
 		if (dbg_io_ops->flush)
 			dbg_io_ops->flush();

 		/* Now see what we get in reply. */
 		ch = dbg_io_ops->read_char();

 		if (ch == 3)
 			ch = dbg_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 == '$') {
 			dbg_io_ops->write_char('-');
 			if (dbg_io_ops->flush)
 				dbg_io_ops->flush();
 			return;
 		}
 	}
 }

 static char gdbmsgbuf[BUFMAX + 1];

 void gdbstub_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);
 	}
 }

 /*
  * 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;
 }

 /*
  * 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, unsigned long *long_val)
 {
 	int hex_val;
 	int num = 0;
 	int negate = 0;

 	*long_val = 0;

 	if (**ptr == '-') {
 		negate = 1;
 		(*ptr)++;
 	}
 	while (**ptr) {
 		hex_val = hex(**ptr);
 		if (hex_val < 0)
 			break;

 		*long_val = (*long_val << 4) | hex_val;
 		num++;
 		(*ptr)++;
 	}

 	if (negate)
 		*long_val = -*long_val;

 	return num;
 }

 /*
  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
  * 0x7d escaped with 0x7d. Return -EFAULT on failure or 0 on success.
  * The input buf is overwitten with the result to write to mem.
  */
 static int kgdb_ebin2mem(char *buf, char *mem, int count)
 {
 	int size = 0;
 	char *c = buf;

 	while (count-- > 0) {
 		c[size] = *buf++;
 		if (c[size] == 0x7d)
 			c[size] = *buf++ ^ 0x20;
 		size++;
 	}

 	return probe_kernel_write(mem, c, size);
 }

 /* 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);
 		return 0;
 	}

 	return -EINVAL;
 }

 static void error_packet(char *pkt, int error)
 {
 	error = -error;
 	pkt[0] = 'E';
 	pkt[1] = hex_asc[(error / 10)];
 	pkt[2] = hex_asc[(error % 10)];
 	pkt[3] = '\0';
 }

 /*
  * Thread ID accessors. We represent a flat TID space to GDB, where
  * the per CPU idle threads (which under Linux all have PID 0) are
  * remapped to negative TIDs.
  */

 #define BUF_THREAD_ID_SIZE	16

 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;
 	put_unaligned_be32(value, scan);
 }

 static struct task_struct *getthread(struct pt_regs *regs, int tid)
 {
 	/*
 	 * Non-positive TIDs are remapped to the cpu shadow information
 	 */
 	if (tid == 0 || tid == -1)
 		tid = -atomic_read(&kgdb_active) - 2;
 	if (tid < -1 && tid > -NR_CPUS - 2) {
 		if (kgdb_info[-tid - 2].task)
 			return kgdb_info[-tid - 2].task;
 		else
 			return idle_task(-tid - 2);
 	}
 	if (tid <= 0) {
 		printk(KERN_ERR "KGDB: Internal thread select error\n");
 		dump_stack();
 		return NULL;
 	}

 	/*
 	 * find_task_by_pid_ns() 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_ns(tid, &init_pid_ns);
 }


 /*
  * Remap normal tasks to their real PID,
  * CPU shadow threads are mapped to -CPU - 2
  */
 static inline int shadow_pid(int realpid)
 {
 	if (realpid)
 		return realpid;

 	return -raw_smp_processor_id() - 2;
 }

 /*
  * 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.
 	 */
 	dbg_remove_all_break();

 	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 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_each_online_cpu(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 (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 = dbg_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:
 		 */
 		dbg_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 emergency reboot\n");
 		strcpy(remcom_out_buffer, "OK");
 		put_packet(remcom_out_buffer);

 		/*
 		 * Execution should not return from
 		 * machine_emergency_restart()
 		 */
 		machine_emergency_restart();
 		kgdb_connected = 0;

 		return 1;
 	}
 	return 0;
 }

 /* Handle the 'q' query packets */
 static void gdb_cmd_query(struct kgdb_state *ks)
 {
 	struct task_struct *g;
 	struct task_struct *p;
 	unsigned char thref[8];
 	char *ptr;
 	int i;
 	int cpu;
 	int finished = 0;

 	switch (remcom_in_buffer[1]) {
 	case 's':
 	case 'f':
 		if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
 			error_packet(remcom_out_buffer, -EINVAL);
 			break;
 		}

 		i = 0;
 		remcom_out_buffer[0] = 'm';
 		ptr = remcom_out_buffer + 1;
 		if (remcom_in_buffer[1] == 'f') {
 			/* Each cpu is a shadow thread */
 			for_each_online_cpu(cpu) {
 				ks->thr_query = 0;
 				int_to_threadref(thref, -cpu - 2);
 				pack_threadid(ptr, thref);
 				ptr += BUF_THREAD_ID_SIZE;
 				*(ptr++) = ',';
 				i++;
 			}
 		}

 		do_each_thread(g, p) {
 			if (i >= ks->thr_query && !finished) {
 				int_to_threadref(thref, p->pid);
 				pack_threadid(ptr, thref);
 				ptr += BUF_THREAD_ID_SIZE;
 				*(ptr++) = ',';
 				ks->thr_query++;
 				if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
 					finished = 1;
 			}
 			i++;
 		} while_each_thread(g, p);

 		*(--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 ((int)ks->threadid > 0) {
 			kgdb_mem2hex(getthread(ks->linux_regs,
 					ks->threadid)->comm,
 					remcom_out_buffer, 16);
 		} else {
 			static char tmpstr[23 + BUF_THREAD_ID_SIZE];

 			sprintf(tmpstr, "shadowCPU%d",
 					(int)(-ks->threadid - 2));
 			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 = dbg_set_sw_break(addr);
 	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
 		error = dbg_remove_sw_break(addr);
 	else if (remcom_in_buffer[0] == 'Z')
 		error = arch_kgdb_ops.set_hw_breakpoint(addr,
 			(int)length, *bpt_type - '0');
 	else if (remcom_in_buffer[0] == 'z')
 		error = arch_kgdb_ops.remove_hw_breakpoint(addr,
 			(int) length, *bpt_type - '0');

 	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';
 		dbg_remove_all_break();
 		kgdb_connected = 0;
 		return 1;

 	} else {
 		gdbstub_msg_write("KGDB only knows signal 9 (pass)"
 			" and 15 (pass and disconnect)\n"
 			"Executing a continue without signal passing\n", 0);
 		remcom_in_buffer[0] = 'c';
 	}

 	/* Indicate fall through */
 	return -1;
 }

 /*
  * This function performs all gdbserial command procesing
  */
 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;

 		/* 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;
 			}
 			dbg_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;
 }
	/*
	* Kernel Debug Core
	*
	* Maintainer: Jason Wessel <jason.wessel@windriver.com>
	*
	* Copyright (C) 2000-2001 VERITAS Software Corporation.
	* Copyright (C) 2002-2004 Timesys Corporation
	* Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
	* Copyright (C) 2004 Pavel Machek <pavel@suse.cz>
	* Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
	* Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
	* Copyright (C) 2005-2009 Wind River Systems, Inc.
	* Copyright (C) 2007 MontaVista Software, Inc.
	* Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
	*
	* Contributors at various stages not listed above:
	* Jason Wessel ( jason.wessel@windriver.com )
	* George Anzinger <george@mvista.com>
	* Anurekh Saxena (anurekh.saxena@timesys.com)
	* Lake Stevens Instrument Division (Glenn Engel)
	* Jim Kingdon, Cygnus Support.
	*
	* Original KGDB stub: David Grothe <dave@gcom.com>,
	* Tigran Aivazian <tigran@sco.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/kernel.h>
	#include <linux/kgdb.h>
	#include <linux/reboot.h>
	#include <linux/uaccess.h>
	#include <asm/cacheflush.h>
	#include <asm/unaligned.h>
	#include "debug_core.h"

	#define KGDB_MAX_THREAD_QUERY 17

	/* 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)];

	/*
	* GDB remote protocol parser:
	*/

	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 = (dbg_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 = dbg_io_ops->read_char();
	if (ch == '#')
	break;
	checksum = checksum + ch;
	buffer[count] = ch;
	count = count + 1;
	}
	buffer[count] = 0;

	if (ch == '#') {
	xmitcsum = hex(dbg_io_ops->read_char()) << 4;
	xmitcsum += hex(dbg_io_ops->read_char());

	if (checksum != xmitcsum)
	/* failed checksum */
	dbg_io_ops->write_char('-');
	else
	/* successful transfer */
	dbg_io_ops->write_char('+');
	if (dbg_io_ops->flush)
	dbg_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;

	/*
	* $<packet info>#<checksum>.
	*/
	while (1) {
	dbg_io_ops->write_char('$');
	checksum = 0;
	count = 0;

	while ((ch = buffer[count])) {
	dbg_io_ops->write_char(ch);
	checksum += ch;
	count++;
	}

	dbg_io_ops->write_char('#');
	dbg_io_ops->write_char(hex_asc_hi(checksum));
	dbg_io_ops->write_char(hex_asc_lo(checksum));
	if (dbg_io_ops->flush)
	dbg_io_ops->flush();

	/* Now see what we get in reply. */
	ch = dbg_io_ops->read_char();

	if (ch == 3)
	ch = dbg_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 == '$') {
	dbg_io_ops->write_char('-');
	if (dbg_io_ops->flush)
	dbg_io_ops->flush();
	return;
	}
	}
	}

	static char gdbmsgbuf[BUFMAX + 1];

	void gdbstub_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);
	}
	}

	/*
	* 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;
	}

	/*
	* 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, unsigned long long_val)
	{
	int hex_val;
	int num = 0;
	int negate = 0;

	*long_val = 0;

	if (**ptr == '-') {
	negate = 1;
	(*ptr)++;
	}
	while (**ptr) {
	hex_val = hex(**ptr);
	if (hex_val < 0)
	break;

	long_val = (long_val << 4) \| hex_val;
	num++;
	(*ptr)++;
	}

	if (negate)
	long_val = -long_val;

	return num;
	}

	/*
	* Copy the binary array pointed to by buf into mem. Fix $, #, and
	* 0x7d escaped with 0x7d. Return -EFAULT on failure or 0 on success.
	* The input buf is overwitten with the result to write to mem.
	*/
	static int kgdb_ebin2mem(char buf, char mem, int count)
	{
	int size = 0;
	char *c = buf;

	while (count-- > 0) {
	c[size] = *buf++;
	if (c[size] == 0x7d)
	c[size] = *buf++ ^ 0x20;
	size++;
	}

	return probe_kernel_write(mem, c, size);
	}

	/* 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);
	return 0;
	}

	return -EINVAL;
	}

	static void error_packet(char *pkt, int error)
	{
	error = -error;
	pkt[0] = 'E';
	pkt[1] = hex_asc[(error / 10)];
	pkt[2] = hex_asc[(error % 10)];
	pkt[3] = '\0';
	}

	/*
	* Thread ID accessors. We represent a flat TID space to GDB, where
	* the per CPU idle threads (which under Linux all have PID 0) are
	* remapped to negative TIDs.
	*/

	#define BUF_THREAD_ID_SIZE 16

	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;
	put_unaligned_be32(value, scan);
	}

	static struct task_struct getthread(struct pt_regs regs, int tid)
	{
	/*
	* Non-positive TIDs are remapped to the cpu shadow information
	*/
	if (tid == 0 \|\| tid == -1)
	tid = -atomic_read(&kgdb_active) - 2;
	if (tid < -1 && tid > -NR_CPUS - 2) {
	if (kgdb_info[-tid - 2].task)
	return kgdb_info[-tid - 2].task;
	else
	return idle_task(-tid - 2);
	}
	if (tid <= 0) {
	printk(KERN_ERR "KGDB: Internal thread select error\n");
	dump_stack();
	return NULL;
	}

	/*
	* find_task_by_pid_ns() 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_ns(tid, &init_pid_ns);
	}


	/*
	* Remap normal tasks to their real PID,
	* CPU shadow threads are mapped to -CPU - 2
	*/
	static inline int shadow_pid(int realpid)
	{
	if (realpid)
	return realpid;

	return -raw_smp_processor_id() - 2;
	}

	/*
	* 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.
	*/
	dbg_remove_all_break();

	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 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_each_online_cpu(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 (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 = dbg_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:
	*/
	dbg_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 emergency reboot\n");
	strcpy(remcom_out_buffer, "OK");
	put_packet(remcom_out_buffer);

	/*
	* Execution should not return from
	* machine_emergency_restart()
	*/
	machine_emergency_restart();
	kgdb_connected = 0;

	return 1;
	}
	return 0;
	}

	/* Handle the 'q' query packets */
	static void gdb_cmd_query(struct kgdb_state *ks)
	{
	struct task_struct *g;
	struct task_struct *p;
	unsigned char thref[8];
	char *ptr;
	int i;
	int cpu;
	int finished = 0;

	switch (remcom_in_buffer[1]) {
	case 's':
	case 'f':
	if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
	error_packet(remcom_out_buffer, -EINVAL);
	break;
	}

	i = 0;
	remcom_out_buffer[0] = 'm';
	ptr = remcom_out_buffer + 1;
	if (remcom_in_buffer[1] == 'f') {
	/* Each cpu is a shadow thread */
	for_each_online_cpu(cpu) {
	ks->thr_query = 0;
	int_to_threadref(thref, -cpu - 2);
	pack_threadid(ptr, thref);
	ptr += BUF_THREAD_ID_SIZE;
	*(ptr++) = ',';
	i++;
	}
	}

	do_each_thread(g, p) {
	if (i >= ks->thr_query && !finished) {
	int_to_threadref(thref, p->pid);
	pack_threadid(ptr, thref);
	ptr += BUF_THREAD_ID_SIZE;
	*(ptr++) = ',';
	ks->thr_query++;
	if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
	finished = 1;
	}
	i++;
	} while_each_thread(g, p);

	*(--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 ((int)ks->threadid > 0) {
	kgdb_mem2hex(getthread(ks->linux_regs,
	ks->threadid)->comm,
	remcom_out_buffer, 16);
	} else {
	static char tmpstr[23 + BUF_THREAD_ID_SIZE];

	sprintf(tmpstr, "shadowCPU%d",
	(int)(-ks->threadid - 2));
	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 = dbg_set_sw_break(addr);
	else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
	error = dbg_remove_sw_break(addr);
	else if (remcom_in_buffer[0] == 'Z')
	error = arch_kgdb_ops.set_hw_breakpoint(addr,
	(int)length, *bpt_type - '0');
	else if (remcom_in_buffer[0] == 'z')
	error = arch_kgdb_ops.remove_hw_breakpoint(addr,
	(int) length, *bpt_type - '0');

	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';
	dbg_remove_all_break();
	kgdb_connected = 0;
	return 1;

	} else {
	gdbstub_msg_write("KGDB only knows signal 9 (pass)"
	" and 15 (pass and disconnect)\n"
	"Executing a continue without signal passing\n", 0);
	remcom_in_buffer[0] = 'c';
	}

	/* Indicate fall through */
	return -1;
	}

	/*
	* This function performs all gdbserial command procesing
	*/
	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;

	/* 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;
	}
	dbg_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;
	}