kernel/debug/kdb/kdb_io.c - linux - Git at Google

 /*
  * Kernel Debugger Architecture Independent Console I/O handler
  *
  * This file is subject to the terms and conditions of the GNU General Public
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
  * Copyright (c) 1999-2006 Silicon Graphics, Inc.  All Rights Reserved.
  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
  */

 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/kdev_t.h>
 #include <linux/console.h>
 #include <linux/string.h>
 #include <linux/sched.h>
 #include <linux/smp.h>
 #include <linux/nmi.h>
 #include <linux/delay.h>
 #include <linux/kgdb.h>
 #include <linux/kdb.h>
 #include <linux/kallsyms.h>
 #include "kdb_private.h"

 #define CMD_BUFLEN 256
 char kdb_prompt_str[CMD_BUFLEN];

 int kdb_trap_printk;
 int kdb_printf_cpu = -1;

 static int kgdb_transition_check(char *buffer)
 {
 	if (buffer[0] != '+' && buffer[0] != '$') {
 		KDB_STATE_SET(KGDB_TRANS);
 		kdb_printf("%s", buffer);
 	} else {
 		int slen = strlen(buffer);
 		if (slen > 3 && buffer[slen - 3] == '#') {
 			kdb_gdb_state_pass(buffer);
 			strcpy(buffer, "kgdb");
 			KDB_STATE_SET(DOING_KGDB);
 			return 1;
 		}
 	}
 	return 0;
 }

 /**
  * kdb_handle_escape() - validity check on an accumulated escape sequence.
  * @buf:	Accumulated escape characters to be examined. Note that buf
  *		is not a string, it is an array of characters and need not be
  *		nil terminated.
  * @sz:		Number of accumulated escape characters.
  *
  * Return: -1 if the escape sequence is unwanted, 0 if it is incomplete,
  * otherwise it returns a mapped key value to pass to the upper layers.
  */
 static int kdb_handle_escape(char *buf, size_t sz)
 {
 	char *lastkey = buf + sz - 1;

 	switch (sz) {
 	case 1:
 		if (*lastkey == '\e')
 			return 0;
 		break;

 	case 2: /* \e<something> */
 		if (*lastkey == '[')
 			return 0;
 		break;

 	case 3:
 		switch (*lastkey) {
 		case 'A': /* \e[A, up arrow */
 			return 16;
 		case 'B': /* \e[B, down arrow */
 			return 14;
 		case 'C': /* \e[C, right arrow */
 			return 6;
 		case 'D': /* \e[D, left arrow */
 			return 2;
 		case '1': /* \e[<1,3,4>], may be home, del, end */
 		case '3':
 		case '4':
 			return 0;
 		}
 		break;

 	case 4:
 		if (*lastkey == '~') {
 			switch (buf[2]) {
 			case '1': /* \e[1~, home */
 				return 1;
 			case '3': /* \e[3~, del */
 				return 4;
 			case '4': /* \e[4~, end */
 				return 5;
 			}
 		}
 		break;
 	}

 	return -1;
 }

 /**
  * kdb_getchar() - Read a single character from a kdb console (or consoles).
  *
  * Other than polling the various consoles that are currently enabled,
  * most of the work done in this function is dealing with escape sequences.
  *
  * An escape key could be the start of a vt100 control sequence such as \e[D
  * (left arrow) or it could be a character in its own right.  The standard
  * method for detecting the difference is to wait for 2 seconds to see if there
  * are any other characters.  kdb is complicated by the lack of a timer service
  * (interrupts are off), by multiple input sources. Escape sequence processing
  * has to be done as states in the polling loop.
  *
  * Return: The key pressed or a control code derived from an escape sequence.
  */
 char kdb_getchar(void)
 {
 #define ESCAPE_UDELAY 1000
 #define ESCAPE_DELAY (2*1000000/ESCAPE_UDELAY) /* 2 seconds worth of udelays */
 	char buf[4];	/* longest vt100 escape sequence is 4 bytes */
 	char *pbuf = buf;
 	int escape_delay = 0;
 	get_char_func *f, *f_prev = NULL;
 	int key;

 	for (f = &kdb_poll_funcs[0]; ; ++f) {
 		if (*f == NULL) {
 			/* Reset NMI watchdog once per poll loop */
 			touch_nmi_watchdog();
 			f = &kdb_poll_funcs[0];
 		}

 		key = (*f)();
 		if (key == -1) {
 			if (escape_delay) {
 				udelay(ESCAPE_UDELAY);
 				if (--escape_delay == 0)
 					return '\e';
 			}
 			continue;
 		}

 		/*
 		 * When the first character is received (or we get a change
 		 * input source) we set ourselves up to handle an escape
 		 * sequences (just in case).
 		 */
 		if (f_prev != f) {
 			f_prev = f;
 			pbuf = buf;
 			escape_delay = ESCAPE_DELAY;
 		}

 		*pbuf++ = key;
 		key = kdb_handle_escape(buf, pbuf - buf);
 		if (key < 0) /* no escape sequence; return best character */
 			return buf[pbuf - buf == 2 ? 1 : 0];
 		if (key > 0)
 			return key;
 	}

 	unreachable();
 }

 /*
  * kdb_read
  *
  *	This function reads a string of characters, terminated by
  *	a newline, or by reaching the end of the supplied buffer,
  *	from the current kernel debugger console device.
  * Parameters:
  *	buffer	- Address of character buffer to receive input characters.
  *	bufsize - size, in bytes, of the character buffer
  * Returns:
  *	Returns a pointer to the buffer containing the received
  *	character string.  This string will be terminated by a
  *	newline character.
  * Locking:
  *	No locks are required to be held upon entry to this
  *	function.  It is not reentrant - it relies on the fact
  *	that while kdb is running on only one "master debug" cpu.
  * Remarks:
  *	The buffer size must be >= 2.
  */

 static char *kdb_read(char *buffer, size_t bufsize)
 {
 	char *cp = buffer;
 	char *bufend = buffer+bufsize-2;	/* Reserve space for newline
 						 * and null byte */
 	char *lastchar;
 	char *p_tmp;
 	char tmp;
 	static char tmpbuffer[CMD_BUFLEN];
 	int len = strlen(buffer);
 	int len_tmp;
 	int tab = 0;
 	int count;
 	int i;
 	int diag, dtab_count;
 	int key, buf_size, ret;


 	diag = kdbgetintenv("DTABCOUNT", &dtab_count);
 	if (diag)
 		dtab_count = 30;

 	if (len > 0) {
 		cp += len;
 		if (*(buffer+len-1) == '\n')
 			cp--;
 	}

 	lastchar = cp;
 	*cp = '\0';
 	kdb_printf("%s", buffer);
 poll_again:
 	key = kdb_getchar();
 	if (key != 9)
 		tab = 0;
 	switch (key) {
 	case 8: /* backspace */
 		if (cp > buffer) {
 			if (cp < lastchar) {
 				memcpy(tmpbuffer, cp, lastchar - cp);
 				memcpy(cp-1, tmpbuffer, lastchar - cp);
 			}
 			*(--lastchar) = '\0';
 			--cp;
 			kdb_printf("\b%s \r", cp);
 			tmp = *cp;
 			*cp = '\0';
 			kdb_printf(kdb_prompt_str);
 			kdb_printf("%s", buffer);
 			*cp = tmp;
 		}
 		break;
 	case 13: /* enter */
 		*lastchar++ = '\n';
 		*lastchar++ = '\0';
 		if (!KDB_STATE(KGDB_TRANS)) {
 			KDB_STATE_SET(KGDB_TRANS);
 			kdb_printf("%s", buffer);
 		}
 		kdb_printf("\n");
 		return buffer;
 	case 4: /* Del */
 		if (cp < lastchar) {
 			memcpy(tmpbuffer, cp+1, lastchar - cp - 1);
 			memcpy(cp, tmpbuffer, lastchar - cp - 1);
 			*(--lastchar) = '\0';
 			kdb_printf("%s \r", cp);
 			tmp = *cp;
 			*cp = '\0';
 			kdb_printf(kdb_prompt_str);
 			kdb_printf("%s", buffer);
 			*cp = tmp;
 		}
 		break;
 	case 1: /* Home */
 		if (cp > buffer) {
 			kdb_printf("\r");
 			kdb_printf(kdb_prompt_str);
 			cp = buffer;
 		}
 		break;
 	case 5: /* End */
 		if (cp < lastchar) {
 			kdb_printf("%s", cp);
 			cp = lastchar;
 		}
 		break;
 	case 2: /* Left */
 		if (cp > buffer) {
 			kdb_printf("\b");
 			--cp;
 		}
 		break;
 	case 14: /* Down */
 		memset(tmpbuffer, ' ',
 		       strlen(kdb_prompt_str) + (lastchar-buffer));
 		*(tmpbuffer+strlen(kdb_prompt_str) +
 		  (lastchar-buffer)) = '\0';
 		kdb_printf("\r%s\r", tmpbuffer);
 		*lastchar = (char)key;
 		*(lastchar+1) = '\0';
 		return lastchar;
 	case 6: /* Right */
 		if (cp < lastchar) {
 			kdb_printf("%c", *cp);
 			++cp;
 		}
 		break;
 	case 16: /* Up */
 		memset(tmpbuffer, ' ',
 		       strlen(kdb_prompt_str) + (lastchar-buffer));
 		*(tmpbuffer+strlen(kdb_prompt_str) +
 		  (lastchar-buffer)) = '\0';
 		kdb_printf("\r%s\r", tmpbuffer);
 		*lastchar = (char)key;
 		*(lastchar+1) = '\0';
 		return lastchar;
 	case 9: /* Tab */
 		if (tab < 2)
 			++tab;
 		p_tmp = buffer;
 		while (*p_tmp == ' ')
 			p_tmp++;
 		if (p_tmp > cp)
 			break;
 		memcpy(tmpbuffer, p_tmp, cp-p_tmp);
 		*(tmpbuffer + (cp-p_tmp)) = '\0';
 		p_tmp = strrchr(tmpbuffer, ' ');
 		if (p_tmp)
 			++p_tmp;
 		else
 			p_tmp = tmpbuffer;
 		len = strlen(p_tmp);
 		buf_size = sizeof(tmpbuffer) - (p_tmp - tmpbuffer);
 		count = kallsyms_symbol_complete(p_tmp, buf_size);
 		if (tab == 2 && count > 0) {
 			kdb_printf("\n%d symbols are found.", count);
 			if (count > dtab_count) {
 				count = dtab_count;
 				kdb_printf(" But only first %d symbols will"
 					   " be printed.\nYou can change the"
 					   " environment variable DTABCOUNT.",
 					   count);
 			}
 			kdb_printf("\n");
 			for (i = 0; i < count; i++) {
 				ret = kallsyms_symbol_next(p_tmp, i, buf_size);
 				if (WARN_ON(!ret))
 					break;
 				if (ret != -E2BIG)
 					kdb_printf("%s ", p_tmp);
 				else
 					kdb_printf("%s... ", p_tmp);
 				*(p_tmp + len) = '\0';
 			}
 			if (i >= dtab_count)
 				kdb_printf("...");
 			kdb_printf("\n");
 			kdb_printf(kdb_prompt_str);
 			kdb_printf("%s", buffer);
 		} else if (tab != 2 && count > 0) {
 			len_tmp = strlen(p_tmp);
 			strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
 			len_tmp = strlen(p_tmp);
 			strncpy(cp, p_tmp+len, len_tmp-len + 1);
 			len = len_tmp - len;
 			kdb_printf("%s", cp);
 			cp += len;
 			lastchar += len;
 		}
 		kdb_nextline = 1; /* reset output line number */
 		break;
 	default:
 		if (key >= 32 && lastchar < bufend) {
 			if (cp < lastchar) {
 				memcpy(tmpbuffer, cp, lastchar - cp);
 				memcpy(cp+1, tmpbuffer, lastchar - cp);
 				*++lastchar = '\0';
 				*cp = key;
 				kdb_printf("%s\r", cp);
 				++cp;
 				tmp = *cp;
 				*cp = '\0';
 				kdb_printf(kdb_prompt_str);
 				kdb_printf("%s", buffer);
 				*cp = tmp;
 			} else {
 				*++lastchar = '\0';
 				*cp++ = key;
 				/* The kgdb transition check will hide
 				 * printed characters if we think that
 				 * kgdb is connecting, until the check
 				 * fails */
 				if (!KDB_STATE(KGDB_TRANS)) {
 					if (kgdb_transition_check(buffer))
 						return buffer;
 				} else {
 					kdb_printf("%c", key);
 				}
 			}
 			/* Special escape to kgdb */
 			if (lastchar - buffer >= 5 &&
 			    strcmp(lastchar - 5, "$?#3f") == 0) {
 				kdb_gdb_state_pass(lastchar - 5);
 				strcpy(buffer, "kgdb");
 				KDB_STATE_SET(DOING_KGDB);
 				return buffer;
 			}
 			if (lastchar - buffer >= 11 &&
 			    strcmp(lastchar - 11, "$qSupported") == 0) {
 				kdb_gdb_state_pass(lastchar - 11);
 				strcpy(buffer, "kgdb");
 				KDB_STATE_SET(DOING_KGDB);
 				return buffer;
 			}
 		}
 		break;
 	}
 	goto poll_again;
 }

 /*
  * kdb_getstr
  *
  *	Print the prompt string and read a command from the
  *	input device.
  *
  * Parameters:
  *	buffer	Address of buffer to receive command
  *	bufsize Size of buffer in bytes
  *	prompt	Pointer to string to use as prompt string
  * Returns:
  *	Pointer to command buffer.
  * Locking:
  *	None.
  * Remarks:
  *	For SMP kernels, the processor number will be
  *	substituted for %d, %x or %o in the prompt.
  */

 char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
 {
 	if (prompt && kdb_prompt_str != prompt)
 		strscpy(kdb_prompt_str, prompt, CMD_BUFLEN);
 	kdb_printf(kdb_prompt_str);
 	kdb_nextline = 1;	/* Prompt and input resets line number */
 	return kdb_read(buffer, bufsize);
 }

 /*
  * kdb_input_flush
  *
  *	Get rid of any buffered console input.
  *
  * Parameters:
  *	none
  * Returns:
  *	nothing
  * Locking:
  *	none
  * Remarks:
  *	Call this function whenever you want to flush input.  If there is any
  *	outstanding input, it ignores all characters until there has been no
  *	data for approximately 1ms.
  */

 static void kdb_input_flush(void)
 {
 	get_char_func *f;
 	int res;
 	int flush_delay = 1;
 	while (flush_delay) {
 		flush_delay--;
 empty:
 		touch_nmi_watchdog();
 		for (f = &kdb_poll_funcs[0]; *f; ++f) {
 			res = (*f)();
 			if (res != -1) {
 				flush_delay = 1;
 				goto empty;
 			}
 		}
 		if (flush_delay)
 			mdelay(1);
 	}
 }

 /*
  * kdb_printf
  *
  *	Print a string to the output device(s).
  *
  * Parameters:
  *	printf-like format and optional args.
  * Returns:
  *	0
  * Locking:
  *	None.
  * Remarks:
  *	use 'kdbcons->write()' to avoid polluting 'log_buf' with
  *	kdb output.
  *
  *  If the user is doing a cmd args | grep srch
  *  then kdb_grepping_flag is set.
  *  In that case we need to accumulate full lines (ending in \n) before
  *  searching for the pattern.
  */

 static char kdb_buffer[256];	/* A bit too big to go on stack */
 static char *next_avail = kdb_buffer;
 static int  size_avail;
 static int  suspend_grep;

 /*
  * search arg1 to see if it contains arg2
  * (kdmain.c provides flags for ^pat and pat$)
  *
  * return 1 for found, 0 for not found
  */
 static int kdb_search_string(char *searched, char *searchfor)
 {
 	char firstchar, *cp;
 	int len1, len2;

 	/* not counting the newline at the end of "searched" */
 	len1 = strlen(searched)-1;
 	len2 = strlen(searchfor);
 	if (len1 < len2)
 		return 0;
 	if (kdb_grep_leading && kdb_grep_trailing && len1 != len2)
 		return 0;
 	if (kdb_grep_leading) {
 		if (!strncmp(searched, searchfor, len2))
 			return 1;
 	} else if (kdb_grep_trailing) {
 		if (!strncmp(searched+len1-len2, searchfor, len2))
 			return 1;
 	} else {
 		firstchar = *searchfor;
 		cp = searched;
 		while ((cp = strchr(cp, firstchar))) {
 			if (!strncmp(cp, searchfor, len2))
 				return 1;
 			cp++;
 		}
 	}
 	return 0;
 }

 static void kdb_msg_write(const char *msg, int msg_len)
 {
 	struct console *c;
 	const char *cp;
 	int len;

 	if (msg_len == 0)
 		return;

 	cp = msg;
 	len = msg_len;

 	while (len--) {
 		dbg_io_ops->write_char(*cp);
 		cp++;
 	}

 	for_each_console(c) {
 		if (!(c->flags & CON_ENABLED))
 			continue;
 		if (c == dbg_io_ops->cons)
 			continue;
 		/*
 		 * Set oops_in_progress to encourage the console drivers to
 		 * disregard their internal spin locks: in the current calling
 		 * context the risk of deadlock is a bigger problem than risks
 		 * due to re-entering the console driver. We operate directly on
 		 * oops_in_progress rather than using bust_spinlocks() because
 		 * the calls bust_spinlocks() makes on exit are not appropriate
 		 * for this calling context.
 		 */
 		++oops_in_progress;
 		c->write(c, msg, msg_len);
 		--oops_in_progress;
 		touch_nmi_watchdog();
 	}
 }

 int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
 {
 	int diag;
 	int linecount;
 	int colcount;
 	int logging, saved_loglevel = 0;
 	int retlen = 0;
 	int fnd, len;
 	int this_cpu, old_cpu;
 	char *cp, *cp2, *cphold = NULL, replaced_byte = ' ';
 	char *moreprompt = "more> ";
 	unsigned long flags;

 	/* Serialize kdb_printf if multiple cpus try to write at once.
 	 * But if any cpu goes recursive in kdb, just print the output,
 	 * even if it is interleaved with any other text.
 	 */
 	local_irq_save(flags);
 	this_cpu = smp_processor_id();
 	for (;;) {
 		old_cpu = cmpxchg(&kdb_printf_cpu, -1, this_cpu);
 		if (old_cpu == -1 || old_cpu == this_cpu)
 			break;

 		cpu_relax();
 	}

 	diag = kdbgetintenv("LINES", &linecount);
 	if (diag || linecount <= 1)
 		linecount = 24;

 	diag = kdbgetintenv("COLUMNS", &colcount);
 	if (diag || colcount <= 1)
 		colcount = 80;

 	diag = kdbgetintenv("LOGGING", &logging);
 	if (diag)
 		logging = 0;

 	if (!kdb_grepping_flag || suspend_grep) {
 		/* normally, every vsnprintf starts a new buffer */
 		next_avail = kdb_buffer;
 		size_avail = sizeof(kdb_buffer);
 	}
 	vsnprintf(next_avail, size_avail, fmt, ap);

 	/*
 	 * If kdb_parse() found that the command was cmd xxx | grep yyy
 	 * then kdb_grepping_flag is set, and kdb_grep_string contains yyy
 	 *
 	 * Accumulate the print data up to a newline before searching it.
 	 * (vsnprintf does null-terminate the string that it generates)
 	 */

 	/* skip the search if prints are temporarily unconditional */
 	if (!suspend_grep && kdb_grepping_flag) {
 		cp = strchr(kdb_buffer, '\n');
 		if (!cp) {
 			/*
 			 * Special cases that don't end with newlines
 			 * but should be written without one:
 			 *   The "[nn]kdb> " prompt should
 			 *   appear at the front of the buffer.
 			 *
 			 *   The "[nn]more " prompt should also be
 			 *     (MOREPROMPT -> moreprompt)
 			 *   written *   but we print that ourselves,
 			 *   we set the suspend_grep flag to make
 			 *   it unconditional.
 			 *
 			 */
 			if (next_avail == kdb_buffer) {
 				/*
 				 * these should occur after a newline,
 				 * so they will be at the front of the
 				 * buffer
 				 */
 				cp2 = kdb_buffer;
 				len = strlen(kdb_prompt_str);
 				if (!strncmp(cp2, kdb_prompt_str, len)) {
 					/*
 					 * We're about to start a new
 					 * command, so we can go back
 					 * to normal mode.
 					 */
 					kdb_grepping_flag = 0;
 					goto kdb_printit;
 				}
 			}
 			/* no newline; don't search/write the buffer
 			   until one is there */
 			len = strlen(kdb_buffer);
 			next_avail = kdb_buffer + len;
 			size_avail = sizeof(kdb_buffer) - len;
 			goto kdb_print_out;
 		}

 		/*
 		 * The newline is present; print through it or discard
 		 * it, depending on the results of the search.
 		 */
 		cp++;	 	     /* to byte after the newline */
 		replaced_byte = *cp; /* remember what/where it was */
 		cphold = cp;
 		*cp = '\0';	     /* end the string for our search */

 		/*
 		 * We now have a newline at the end of the string
 		 * Only continue with this output if it contains the
 		 * search string.
 		 */
 		fnd = kdb_search_string(kdb_buffer, kdb_grep_string);
 		if (!fnd) {
 			/*
 			 * At this point the complete line at the start
 			 * of kdb_buffer can be discarded, as it does
 			 * not contain what the user is looking for.
 			 * Shift the buffer left.
 			 */
 			*cphold = replaced_byte;
 			strcpy(kdb_buffer, cphold);
 			len = strlen(kdb_buffer);
 			next_avail = kdb_buffer + len;
 			size_avail = sizeof(kdb_buffer) - len;
 			goto kdb_print_out;
 		}
 		if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH) {
 			/*
 			 * This was a interactive search (using '/' at more
 			 * prompt) and it has completed. Replace the \0 with
 			 * its original value to ensure multi-line strings
 			 * are handled properly, and return to normal mode.
 			 */
 			*cphold = replaced_byte;
 			kdb_grepping_flag = 0;
 		}
 		/*
 		 * at this point the string is a full line and
 		 * should be printed, up to the null.
 		 */
 	}
 kdb_printit:

 	/*
 	 * Write to all consoles.
 	 */
 	retlen = strlen(kdb_buffer);
 	cp = (char *) printk_skip_headers(kdb_buffer);
 	if (!dbg_kdb_mode && kgdb_connected)
 		gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));
 	else
 		kdb_msg_write(cp, retlen - (cp - kdb_buffer));

 	if (logging) {
 		saved_loglevel = console_loglevel;
 		console_loglevel = CONSOLE_LOGLEVEL_SILENT;
 		if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK)
 			printk("%s", kdb_buffer);
 		else
 			pr_info("%s", kdb_buffer);
 	}

 	if (KDB_STATE(PAGER)) {
 		/*
 		 * Check printed string to decide how to bump the
 		 * kdb_nextline to control when the more prompt should
 		 * show up.
 		 */
 		int got = 0;
 		len = retlen;
 		while (len--) {
 			if (kdb_buffer[len] == '\n') {
 				kdb_nextline++;
 				got = 0;
 			} else if (kdb_buffer[len] == '\r') {
 				got = 0;
 			} else {
 				got++;
 			}
 		}
 		kdb_nextline += got / (colcount + 1);
 	}

 	/* check for having reached the LINES number of printed lines */
 	if (kdb_nextline >= linecount) {
 		char ch;

 		/* Watch out for recursion here.  Any routine that calls
 		 * kdb_printf will come back through here.  And kdb_read
 		 * uses kdb_printf to echo on serial consoles ...
 		 */
 		kdb_nextline = 1;	/* In case of recursion */

 		/*
 		 * Pause until cr.
 		 */
 		moreprompt = kdbgetenv("MOREPROMPT");
 		if (moreprompt == NULL)
 			moreprompt = "more> ";

 		kdb_input_flush();
 		kdb_msg_write(moreprompt, strlen(moreprompt));

 		if (logging)
 			printk("%s", moreprompt);

 		ch = kdb_getchar();
 		kdb_nextline = 1;	/* Really set output line 1 */

 		/* empty and reset the buffer: */
 		kdb_buffer[0] = '\0';
 		next_avail = kdb_buffer;
 		size_avail = sizeof(kdb_buffer);
 		if ((ch == 'q') || (ch == 'Q')) {
 			/* user hit q or Q */
 			KDB_FLAG_SET(CMD_INTERRUPT); /* command interrupted */
 			KDB_STATE_CLEAR(PAGER);
 			/* end of command output; back to normal mode */
 			kdb_grepping_flag = 0;
 			kdb_printf("\n");
 		} else if (ch == ' ') {
 			kdb_printf("\r");
 			suspend_grep = 1; /* for this recursion */
 		} else if (ch == '\n' || ch == '\r') {
 			kdb_nextline = linecount - 1;
 			kdb_printf("\r");
 			suspend_grep = 1; /* for this recursion */
 		} else if (ch == '/' && !kdb_grepping_flag) {
 			kdb_printf("\r");
 			kdb_getstr(kdb_grep_string, KDB_GREP_STRLEN,
 				   kdbgetenv("SEARCHPROMPT") ?: "search> ");
 			*strchrnul(kdb_grep_string, '\n') = '\0';
 			kdb_grepping_flag += KDB_GREPPING_FLAG_SEARCH;
 			suspend_grep = 1; /* for this recursion */
 		} else if (ch) {
 			/* user hit something unexpected */
 			suspend_grep = 1; /* for this recursion */
 			if (ch != '/')
 				kdb_printf(
 				    "\nOnly 'q', 'Q' or '/' are processed at "
 				    "more prompt, input ignored\n");
 			else
 				kdb_printf("\n'/' cannot be used during | "
 					   "grep filtering, input ignored\n");
 		} else if (kdb_grepping_flag) {
 			/* user hit enter */
 			suspend_grep = 1; /* for this recursion */
 			kdb_printf("\n");
 		}
 		kdb_input_flush();
 	}

 	/*
 	 * For grep searches, shift the printed string left.
 	 *  replaced_byte contains the character that was overwritten with
 	 *  the terminating null, and cphold points to the null.
 	 * Then adjust the notion of available space in the buffer.
 	 */
 	if (kdb_grepping_flag && !suspend_grep) {
 		*cphold = replaced_byte;
 		strcpy(kdb_buffer, cphold);
 		len = strlen(kdb_buffer);
 		next_avail = kdb_buffer + len;
 		size_avail = sizeof(kdb_buffer) - len;
 	}

 kdb_print_out:
 	suspend_grep = 0; /* end of what may have been a recursive call */
 	if (logging)
 		console_loglevel = saved_loglevel;
 	/* kdb_printf_cpu locked the code above. */
 	smp_store_release(&kdb_printf_cpu, old_cpu);
 	local_irq_restore(flags);
 	return retlen;
 }

 int kdb_printf(const char *fmt, ...)
 {
 	va_list ap;
 	int r;

 	va_start(ap, fmt);
 	r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap);
 	va_end(ap);

 	return r;
 }
 EXPORT_SYMBOL_GPL(kdb_printf);
	/*
	* Kernel Debugger Architecture Independent Console I/O handler
	*
	* This file is subject to the terms and conditions of the GNU General Public
	* License. See the file "COPYING" in the main directory of this archive
	* for more details.
	*
	* Copyright (c) 1999-2006 Silicon Graphics, Inc. All Rights Reserved.
	* Copyright (c) 2009 Wind River Systems, Inc. All Rights Reserved.
	*/

	#include <linux/module.h>
	#include <linux/types.h>
	#include <linux/ctype.h>
	#include <linux/kernel.h>
	#include <linux/init.h>
	#include <linux/kdev_t.h>
	#include <linux/console.h>
	#include <linux/string.h>
	#include <linux/sched.h>
	#include <linux/smp.h>
	#include <linux/nmi.h>
	#include <linux/delay.h>
	#include <linux/kgdb.h>
	#include <linux/kdb.h>
	#include <linux/kallsyms.h>
	#include "kdb_private.h"

	#define CMD_BUFLEN 256
	char kdb_prompt_str[CMD_BUFLEN];

	int kdb_trap_printk;
	int kdb_printf_cpu = -1;

	static int kgdb_transition_check(char *buffer)
	{
	if (buffer[0] != '+' && buffer[0] != '$') {
	KDB_STATE_SET(KGDB_TRANS);
	kdb_printf("%s", buffer);
	} else {
	int slen = strlen(buffer);
	if (slen > 3 && buffer[slen - 3] == '#') {
	kdb_gdb_state_pass(buffer);
	strcpy(buffer, "kgdb");
	KDB_STATE_SET(DOING_KGDB);
	return 1;
	}
	}
	return 0;
	}

	/**
	* kdb_handle_escape() - validity check on an accumulated escape sequence.
	* @buf: Accumulated escape characters to be examined. Note that buf
	* is not a string, it is an array of characters and need not be
	* nil terminated.
	* @sz: Number of accumulated escape characters.
	*
	* Return: -1 if the escape sequence is unwanted, 0 if it is incomplete,
	* otherwise it returns a mapped key value to pass to the upper layers.
	*/
	static int kdb_handle_escape(char *buf, size_t sz)
	{
	char *lastkey = buf + sz - 1;

	switch (sz) {
	case 1:
	if (*lastkey == '\e')
	return 0;
	break;

	case 2: /* \e<something> */
	if (*lastkey == '[')
	return 0;
	break;

	case 3:
	switch (*lastkey) {
	case 'A': /* \e[A, up arrow */
	return 16;
	case 'B': /* \e[B, down arrow */
	return 14;
	case 'C': /* \e[C, right arrow */
	return 6;
	case 'D': /* \e[D, left arrow */
	return 2;
	case '1': /* \e[<1,3,4>], may be home, del, end */
	case '3':
	case '4':
	return 0;
	}
	break;

	case 4:
	if (*lastkey == '~') {
	switch (buf[2]) {
	case '1': /* \e[1~, home */
	return 1;
	case '3': /* \e[3~, del */
	return 4;
	case '4': /* \e[4~, end */
	return 5;
	}
	}
	break;
	}

	return -1;
	}

	/**
	* kdb_getchar() - Read a single character from a kdb console (or consoles).
	*
	* Other than polling the various consoles that are currently enabled,
	* most of the work done in this function is dealing with escape sequences.
	*
	* An escape key could be the start of a vt100 control sequence such as \e[D
	* (left arrow) or it could be a character in its own right. The standard
	* method for detecting the difference is to wait for 2 seconds to see if there
	* are any other characters. kdb is complicated by the lack of a timer service
	* (interrupts are off), by multiple input sources. Escape sequence processing
	* has to be done as states in the polling loop.
	*
	* Return: The key pressed or a control code derived from an escape sequence.
	*/
	char kdb_getchar(void)
	{
	#define ESCAPE_UDELAY 1000
	#define ESCAPE_DELAY (21000000/ESCAPE_UDELAY) / 2 seconds worth of udelays */
	char buf[4]; /* longest vt100 escape sequence is 4 bytes */
	char *pbuf = buf;
	int escape_delay = 0;
	get_char_func f, f_prev = NULL;
	int key;

	for (f = &kdb_poll_funcs[0]; ; ++f) {
	if (*f == NULL) {
	/* Reset NMI watchdog once per poll loop */
	touch_nmi_watchdog();
	f = &kdb_poll_funcs[0];
	}

	key = (*f)();
	if (key == -1) {
	if (escape_delay) {
	udelay(ESCAPE_UDELAY);
	if (--escape_delay == 0)
	return '\e';
	}
	continue;
	}

	/*
	* When the first character is received (or we get a change
	* input source) we set ourselves up to handle an escape
	* sequences (just in case).
	*/
	if (f_prev != f) {
	f_prev = f;
	pbuf = buf;
	escape_delay = ESCAPE_DELAY;
	}

	*pbuf++ = key;
	key = kdb_handle_escape(buf, pbuf - buf);
	if (key < 0) /* no escape sequence; return best character */
	return buf[pbuf - buf == 2 ? 1 : 0];
	if (key > 0)
	return key;
	}

	unreachable();
	}

	/*
	* kdb_read
	*
	* This function reads a string of characters, terminated by
	* a newline, or by reaching the end of the supplied buffer,
	* from the current kernel debugger console device.
	* Parameters:
	* buffer - Address of character buffer to receive input characters.
	* bufsize - size, in bytes, of the character buffer
	* Returns:
	* Returns a pointer to the buffer containing the received
	* character string. This string will be terminated by a
	* newline character.
	* Locking:
	* No locks are required to be held upon entry to this
	* function. It is not reentrant - it relies on the fact
	* that while kdb is running on only one "master debug" cpu.
	* Remarks:
	* The buffer size must be >= 2.
	*/

	static char kdb_read(char buffer, size_t bufsize)
	{
	char *cp = buffer;
	char bufend = buffer+bufsize-2; / Reserve space for newline
	* and null byte */
	char *lastchar;
	char *p_tmp;
	char tmp;
	static char tmpbuffer[CMD_BUFLEN];
	int len = strlen(buffer);
	int len_tmp;
	int tab = 0;
	int count;
	int i;
	int diag, dtab_count;
	int key, buf_size, ret;


	diag = kdbgetintenv("DTABCOUNT", &dtab_count);
	if (diag)
	dtab_count = 30;

	if (len > 0) {
	cp += len;
	if (*(buffer+len-1) == '\n')
	cp--;
	}

	lastchar = cp;
	*cp = '\0';
	kdb_printf("%s", buffer);
	poll_again:
	key = kdb_getchar();
	if (key != 9)
	tab = 0;
	switch (key) {
	case 8: /* backspace */
	if (cp > buffer) {
	if (cp < lastchar) {
	memcpy(tmpbuffer, cp, lastchar - cp);
	memcpy(cp-1, tmpbuffer, lastchar - cp);
	}
	*(--lastchar) = '\0';
	--cp;
	kdb_printf("\b%s \r", cp);
	tmp = *cp;
	*cp = '\0';
	kdb_printf(kdb_prompt_str);
	kdb_printf("%s", buffer);
	*cp = tmp;
	}
	break;
	case 13: /* enter */
	*lastchar++ = '\n';
	*lastchar++ = '\0';
	if (!KDB_STATE(KGDB_TRANS)) {
	KDB_STATE_SET(KGDB_TRANS);
	kdb_printf("%s", buffer);
	}
	kdb_printf("\n");
	return buffer;
	case 4: /* Del */
	if (cp < lastchar) {
	memcpy(tmpbuffer, cp+1, lastchar - cp - 1);
	memcpy(cp, tmpbuffer, lastchar - cp - 1);
	*(--lastchar) = '\0';
	kdb_printf("%s \r", cp);
	tmp = *cp;
	*cp = '\0';
	kdb_printf(kdb_prompt_str);
	kdb_printf("%s", buffer);
	*cp = tmp;
	}
	break;
	case 1: /* Home */
	if (cp > buffer) {
	kdb_printf("\r");
	kdb_printf(kdb_prompt_str);
	cp = buffer;
	}
	break;
	case 5: /* End */
	if (cp < lastchar) {
	kdb_printf("%s", cp);
	cp = lastchar;
	}
	break;
	case 2: /* Left */
	if (cp > buffer) {
	kdb_printf("\b");
	--cp;
	}
	break;
	case 14: /* Down */
	memset(tmpbuffer, ' ',
	strlen(kdb_prompt_str) + (lastchar-buffer));
	*(tmpbuffer+strlen(kdb_prompt_str) +
	(lastchar-buffer)) = '\0';
	kdb_printf("\r%s\r", tmpbuffer);
	*lastchar = (char)key;
	*(lastchar+1) = '\0';
	return lastchar;
	case 6: /* Right */
	if (cp < lastchar) {
	kdb_printf("%c", *cp);
	++cp;
	}
	break;
	case 16: /* Up */
	memset(tmpbuffer, ' ',
	strlen(kdb_prompt_str) + (lastchar-buffer));
	*(tmpbuffer+strlen(kdb_prompt_str) +
	(lastchar-buffer)) = '\0';
	kdb_printf("\r%s\r", tmpbuffer);
	*lastchar = (char)key;
	*(lastchar+1) = '\0';
	return lastchar;
	case 9: /* Tab */
	if (tab < 2)
	++tab;
	p_tmp = buffer;
	while (*p_tmp == ' ')
	p_tmp++;
	if (p_tmp > cp)
	break;
	memcpy(tmpbuffer, p_tmp, cp-p_tmp);
	*(tmpbuffer + (cp-p_tmp)) = '\0';
	p_tmp = strrchr(tmpbuffer, ' ');
	if (p_tmp)
	++p_tmp;
	else
	p_tmp = tmpbuffer;
	len = strlen(p_tmp);
	buf_size = sizeof(tmpbuffer) - (p_tmp - tmpbuffer);
	count = kallsyms_symbol_complete(p_tmp, buf_size);
	if (tab == 2 && count > 0) {
	kdb_printf("\n%d symbols are found.", count);
	if (count > dtab_count) {
	count = dtab_count;
	kdb_printf(" But only first %d symbols will"
	" be printed.\nYou can change the"
	" environment variable DTABCOUNT.",
	count);
	}
	kdb_printf("\n");
	for (i = 0; i < count; i++) {
	ret = kallsyms_symbol_next(p_tmp, i, buf_size);
	if (WARN_ON(!ret))
	break;
	if (ret != -E2BIG)
	kdb_printf("%s ", p_tmp);
	else
	kdb_printf("%s... ", p_tmp);
	*(p_tmp + len) = '\0';
	}
	if (i >= dtab_count)
	kdb_printf("...");
	kdb_printf("\n");
	kdb_printf(kdb_prompt_str);
	kdb_printf("%s", buffer);
	} else if (tab != 2 && count > 0) {
	len_tmp = strlen(p_tmp);
	strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
	len_tmp = strlen(p_tmp);
	strncpy(cp, p_tmp+len, len_tmp-len + 1);
	len = len_tmp - len;
	kdb_printf("%s", cp);
	cp += len;
	lastchar += len;
	}
	kdb_nextline = 1; /* reset output line number */
	break;
	default:
	if (key >= 32 && lastchar < bufend) {
	if (cp < lastchar) {
	memcpy(tmpbuffer, cp, lastchar - cp);
	memcpy(cp+1, tmpbuffer, lastchar - cp);
	*++lastchar = '\0';
	*cp = key;
	kdb_printf("%s\r", cp);
	++cp;
	tmp = *cp;
	*cp = '\0';
	kdb_printf(kdb_prompt_str);
	kdb_printf("%s", buffer);
	*cp = tmp;
	} else {
	*++lastchar = '\0';
	*cp++ = key;
	/* The kgdb transition check will hide
	* printed characters if we think that
	* kgdb is connecting, until the check
	* fails */
	if (!KDB_STATE(KGDB_TRANS)) {
	if (kgdb_transition_check(buffer))
	return buffer;
	} else {
	kdb_printf("%c", key);
	}
	}
	/* Special escape to kgdb */
	if (lastchar - buffer >= 5 &&
	strcmp(lastchar - 5, "$?#3f") == 0) {
	kdb_gdb_state_pass(lastchar - 5);
	strcpy(buffer, "kgdb");
	KDB_STATE_SET(DOING_KGDB);
	return buffer;
	}
	if (lastchar - buffer >= 11 &&
	strcmp(lastchar - 11, "$qSupported") == 0) {
	kdb_gdb_state_pass(lastchar - 11);
	strcpy(buffer, "kgdb");
	KDB_STATE_SET(DOING_KGDB);
	return buffer;
	}
	}
	break;
	}
	goto poll_again;
	}

	/*
	* kdb_getstr
	*
	* Print the prompt string and read a command from the
	* input device.
	*
	* Parameters:
	* buffer Address of buffer to receive command
	* bufsize Size of buffer in bytes
	* prompt Pointer to string to use as prompt string
	* Returns:
	* Pointer to command buffer.
	* Locking:
	* None.
	* Remarks:
	* For SMP kernels, the processor number will be
	* substituted for %d, %x or %o in the prompt.
	*/

	char kdb_getstr(char buffer, size_t bufsize, const char *prompt)
	{
	if (prompt && kdb_prompt_str != prompt)
	strscpy(kdb_prompt_str, prompt, CMD_BUFLEN);
	kdb_printf(kdb_prompt_str);
	kdb_nextline = 1; /* Prompt and input resets line number */
	return kdb_read(buffer, bufsize);
	}

	/*
	* kdb_input_flush
	*
	* Get rid of any buffered console input.
	*
	* Parameters:
	* none
	* Returns:
	* nothing
	* Locking:
	* none
	* Remarks:
	* Call this function whenever you want to flush input. If there is any
	* outstanding input, it ignores all characters until there has been no
	* data for approximately 1ms.
	*/

	static void kdb_input_flush(void)
	{
	get_char_func *f;
	int res;
	int flush_delay = 1;
	while (flush_delay) {
	flush_delay--;
	empty:
	touch_nmi_watchdog();
	for (f = &kdb_poll_funcs[0]; *f; ++f) {
	res = (*f)();
	if (res != -1) {
	flush_delay = 1;
	goto empty;
	}
	}
	if (flush_delay)
	mdelay(1);
	}
	}

	/*
	* kdb_printf
	*
	* Print a string to the output device(s).
	*
	* Parameters:
	* printf-like format and optional args.
	* Returns:
	* 0
	* Locking:
	* None.
	* Remarks:
	* use 'kdbcons->write()' to avoid polluting 'log_buf' with
	* kdb output.
	*
	* If the user is doing a cmd args \| grep srch
	* then kdb_grepping_flag is set.
	* In that case we need to accumulate full lines (ending in \n) before
	* searching for the pattern.
	*/

	static char kdb_buffer[256]; /* A bit too big to go on stack */
	static char *next_avail = kdb_buffer;
	static int size_avail;
	static int suspend_grep;

	/*
	* search arg1 to see if it contains arg2
	* (kdmain.c provides flags for ^pat and pat$)
	*
	* return 1 for found, 0 for not found
	*/
	static int kdb_search_string(char searched, char searchfor)
	{
	char firstchar, *cp;
	int len1, len2;

	/* not counting the newline at the end of "searched" */
	len1 = strlen(searched)-1;
	len2 = strlen(searchfor);
	if (len1 < len2)
	return 0;
	if (kdb_grep_leading && kdb_grep_trailing && len1 != len2)
	return 0;
	if (kdb_grep_leading) {
	if (!strncmp(searched, searchfor, len2))
	return 1;
	} else if (kdb_grep_trailing) {
	if (!strncmp(searched+len1-len2, searchfor, len2))
	return 1;
	} else {
	firstchar = *searchfor;
	cp = searched;
	while ((cp = strchr(cp, firstchar))) {
	if (!strncmp(cp, searchfor, len2))
	return 1;
	cp++;
	}
	}
	return 0;
	}

	static void kdb_msg_write(const char *msg, int msg_len)
	{
	struct console *c;
	const char *cp;
	int len;

	if (msg_len == 0)
	return;

	cp = msg;
	len = msg_len;

	while (len--) {
	dbg_io_ops->write_char(*cp);
	cp++;
	}

	for_each_console(c) {
	if (!(c->flags & CON_ENABLED))
	continue;
	if (c == dbg_io_ops->cons)
	continue;
	/*
	* Set oops_in_progress to encourage the console drivers to
	* disregard their internal spin locks: in the current calling
	* context the risk of deadlock is a bigger problem than risks
	* due to re-entering the console driver. We operate directly on
	* oops_in_progress rather than using bust_spinlocks() because
	* the calls bust_spinlocks() makes on exit are not appropriate
	* for this calling context.
	*/
	++oops_in_progress;
	c->write(c, msg, msg_len);
	--oops_in_progress;
	touch_nmi_watchdog();
	}
	}

	int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
	{
	int diag;
	int linecount;
	int colcount;
	int logging, saved_loglevel = 0;
	int retlen = 0;
	int fnd, len;
	int this_cpu, old_cpu;
	char cp, cp2, *cphold = NULL, replaced_byte = ' ';
	char *moreprompt = "more> ";
	unsigned long flags;

	/* Serialize kdb_printf if multiple cpus try to write at once.
	* But if any cpu goes recursive in kdb, just print the output,
	* even if it is interleaved with any other text.
	*/
	local_irq_save(flags);
	this_cpu = smp_processor_id();
	for (;;) {
	old_cpu = cmpxchg(&kdb_printf_cpu, -1, this_cpu);
	if (old_cpu == -1 \|\| old_cpu == this_cpu)
	break;

	cpu_relax();
	}

	diag = kdbgetintenv("LINES", &linecount);
	if (diag \|\| linecount <= 1)
	linecount = 24;

	diag = kdbgetintenv("COLUMNS", &colcount);
	if (diag \|\| colcount <= 1)
	colcount = 80;

	diag = kdbgetintenv("LOGGING", &logging);
	if (diag)
	logging = 0;

	if (!kdb_grepping_flag \|\| suspend_grep) {
	/* normally, every vsnprintf starts a new buffer */
	next_avail = kdb_buffer;
	size_avail = sizeof(kdb_buffer);
	}
	vsnprintf(next_avail, size_avail, fmt, ap);

	/*
	* If kdb_parse() found that the command was cmd xxx \| grep yyy
	* then kdb_grepping_flag is set, and kdb_grep_string contains yyy
	*
	* Accumulate the print data up to a newline before searching it.
	* (vsnprintf does null-terminate the string that it generates)
	*/

	/* skip the search if prints are temporarily unconditional */
	if (!suspend_grep && kdb_grepping_flag) {
	cp = strchr(kdb_buffer, '\n');
	if (!cp) {
	/*
	* Special cases that don't end with newlines
	* but should be written without one:
	* The "[nn]kdb> " prompt should
	* appear at the front of the buffer.
	*
	* The "[nn]more " prompt should also be
	* (MOREPROMPT -> moreprompt)
	* written * but we print that ourselves,
	* we set the suspend_grep flag to make
	* it unconditional.
	*
	*/
	if (next_avail == kdb_buffer) {
	/*
	* these should occur after a newline,
	* so they will be at the front of the
	* buffer
	*/
	cp2 = kdb_buffer;
	len = strlen(kdb_prompt_str);
	if (!strncmp(cp2, kdb_prompt_str, len)) {
	/*
	* We're about to start a new
	* command, so we can go back
	* to normal mode.
	*/
	kdb_grepping_flag = 0;
	goto kdb_printit;
	}
	}
	/* no newline; don't search/write the buffer
	until one is there */
	len = strlen(kdb_buffer);
	next_avail = kdb_buffer + len;
	size_avail = sizeof(kdb_buffer) - len;
	goto kdb_print_out;
	}

	/*
	* The newline is present; print through it or discard
	* it, depending on the results of the search.
	*/
	cp++; /* to byte after the newline */
	replaced_byte = cp; / remember what/where it was */
	cphold = cp;
	cp = '\0'; / end the string for our search */

	/*
	* We now have a newline at the end of the string
	* Only continue with this output if it contains the
	* search string.
	*/
	fnd = kdb_search_string(kdb_buffer, kdb_grep_string);
	if (!fnd) {
	/*
	* At this point the complete line at the start
	* of kdb_buffer can be discarded, as it does
	* not contain what the user is looking for.
	* Shift the buffer left.
	*/
	*cphold = replaced_byte;
	strcpy(kdb_buffer, cphold);
	len = strlen(kdb_buffer);
	next_avail = kdb_buffer + len;
	size_avail = sizeof(kdb_buffer) - len;
	goto kdb_print_out;
	}
	if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH) {
	/*
	* This was a interactive search (using '/' at more
	* prompt) and it has completed. Replace the \0 with
	* its original value to ensure multi-line strings
	* are handled properly, and return to normal mode.
	*/
	*cphold = replaced_byte;
	kdb_grepping_flag = 0;
	}
	/*
	* at this point the string is a full line and
	* should be printed, up to the null.
	*/
	}
	kdb_printit:

	/*
	* Write to all consoles.
	*/
	retlen = strlen(kdb_buffer);
	cp = (char *) printk_skip_headers(kdb_buffer);
	if (!dbg_kdb_mode && kgdb_connected)
	gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));
	else
	kdb_msg_write(cp, retlen - (cp - kdb_buffer));

	if (logging) {
	saved_loglevel = console_loglevel;
	console_loglevel = CONSOLE_LOGLEVEL_SILENT;
	if (printk_get_level(kdb_buffer) \|\| src == KDB_MSGSRC_PRINTK)
	printk("%s", kdb_buffer);
	else
	pr_info("%s", kdb_buffer);
	}

	if (KDB_STATE(PAGER)) {
	/*
	* Check printed string to decide how to bump the
	* kdb_nextline to control when the more prompt should
	* show up.
	*/
	int got = 0;
	len = retlen;
	while (len--) {
	if (kdb_buffer[len] == '\n') {
	kdb_nextline++;
	got = 0;
	} else if (kdb_buffer[len] == '\r') {
	got = 0;
	} else {
	got++;
	}
	}
	kdb_nextline += got / (colcount + 1);
	}

	/* check for having reached the LINES number of printed lines */
	if (kdb_nextline >= linecount) {
	char ch;

	/* Watch out for recursion here. Any routine that calls
	* kdb_printf will come back through here. And kdb_read
	* uses kdb_printf to echo on serial consoles ...
	*/
	kdb_nextline = 1; /* In case of recursion */

	/*
	* Pause until cr.
	*/
	moreprompt = kdbgetenv("MOREPROMPT");
	if (moreprompt == NULL)
	moreprompt = "more> ";

	kdb_input_flush();
	kdb_msg_write(moreprompt, strlen(moreprompt));

	if (logging)
	printk("%s", moreprompt);

	ch = kdb_getchar();
	kdb_nextline = 1; /* Really set output line 1 */

	/* empty and reset the buffer: */
	kdb_buffer[0] = '\0';
	next_avail = kdb_buffer;
	size_avail = sizeof(kdb_buffer);
	if ((ch == 'q') \|\| (ch == 'Q')) {
	/* user hit q or Q */
	KDB_FLAG_SET(CMD_INTERRUPT); /* command interrupted */
	KDB_STATE_CLEAR(PAGER);
	/* end of command output; back to normal mode */
	kdb_grepping_flag = 0;
	kdb_printf("\n");
	} else if (ch == ' ') {
	kdb_printf("\r");
	suspend_grep = 1; /* for this recursion */
	} else if (ch == '\n' \|\| ch == '\r') {
	kdb_nextline = linecount - 1;
	kdb_printf("\r");
	suspend_grep = 1; /* for this recursion */
	} else if (ch == '/' && !kdb_grepping_flag) {
	kdb_printf("\r");
	kdb_getstr(kdb_grep_string, KDB_GREP_STRLEN,
	kdbgetenv("SEARCHPROMPT") ?: "search> ");
	*strchrnul(kdb_grep_string, '\n') = '\0';
	kdb_grepping_flag += KDB_GREPPING_FLAG_SEARCH;
	suspend_grep = 1; /* for this recursion */
	} else if (ch) {
	/* user hit something unexpected */
	suspend_grep = 1; /* for this recursion */
	if (ch != '/')
	kdb_printf(
	"\nOnly 'q', 'Q' or '/' are processed at "
	"more prompt, input ignored\n");
	else
	kdb_printf("\n'/' cannot be used during \| "
	"grep filtering, input ignored\n");
	} else if (kdb_grepping_flag) {
	/* user hit enter */
	suspend_grep = 1; /* for this recursion */
	kdb_printf("\n");
	}
	kdb_input_flush();
	}

	/*
	* For grep searches, shift the printed string left.
	* replaced_byte contains the character that was overwritten with
	* the terminating null, and cphold points to the null.
	* Then adjust the notion of available space in the buffer.
	*/
	if (kdb_grepping_flag && !suspend_grep) {
	*cphold = replaced_byte;
	strcpy(kdb_buffer, cphold);
	len = strlen(kdb_buffer);
	next_avail = kdb_buffer + len;
	size_avail = sizeof(kdb_buffer) - len;
	}

	kdb_print_out:
	suspend_grep = 0; /* end of what may have been a recursive call */
	if (logging)
	console_loglevel = saved_loglevel;
	/* kdb_printf_cpu locked the code above. */
	smp_store_release(&kdb_printf_cpu, old_cpu);
	local_irq_restore(flags);
	return retlen;
	}

	int kdb_printf(const char *fmt, ...)
	{
	va_list ap;
	int r;

	va_start(ap, fmt);
	r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap);
	va_end(ap);

	return r;
	}
	EXPORT_SYMBOL_GPL(kdb_printf);