xref: /openbmc/linux/kernel/debug/kdb/kdb_io.c (revision 95e9fd10)
1 /*
2  * Kernel Debugger Architecture Independent Console I/O handler
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (c) 1999-2006 Silicon Graphics, Inc.  All Rights Reserved.
9  * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/ctype.h>
15 #include <linux/kernel.h>
16 #include <linux/init.h>
17 #include <linux/kdev_t.h>
18 #include <linux/console.h>
19 #include <linux/string.h>
20 #include <linux/sched.h>
21 #include <linux/smp.h>
22 #include <linux/nmi.h>
23 #include <linux/delay.h>
24 #include <linux/kgdb.h>
25 #include <linux/kdb.h>
26 #include <linux/kallsyms.h>
27 #include "kdb_private.h"
28 
29 #define CMD_BUFLEN 256
30 char kdb_prompt_str[CMD_BUFLEN];
31 
32 int kdb_trap_printk;
33 
34 static int kgdb_transition_check(char *buffer)
35 {
36 	if (buffer[0] != '+' && buffer[0] != '$') {
37 		KDB_STATE_SET(KGDB_TRANS);
38 		kdb_printf("%s", buffer);
39 	} else {
40 		int slen = strlen(buffer);
41 		if (slen > 3 && buffer[slen - 3] == '#') {
42 			kdb_gdb_state_pass(buffer);
43 			strcpy(buffer, "kgdb");
44 			KDB_STATE_SET(DOING_KGDB);
45 			return 1;
46 		}
47 	}
48 	return 0;
49 }
50 
51 static int kdb_read_get_key(char *buffer, size_t bufsize)
52 {
53 #define ESCAPE_UDELAY 1000
54 #define ESCAPE_DELAY (2*1000000/ESCAPE_UDELAY) /* 2 seconds worth of udelays */
55 	char escape_data[5];	/* longest vt100 escape sequence is 4 bytes */
56 	char *ped = escape_data;
57 	int escape_delay = 0;
58 	get_char_func *f, *f_escape = NULL;
59 	int key;
60 
61 	for (f = &kdb_poll_funcs[0]; ; ++f) {
62 		if (*f == NULL) {
63 			/* Reset NMI watchdog once per poll loop */
64 			touch_nmi_watchdog();
65 			f = &kdb_poll_funcs[0];
66 		}
67 		if (escape_delay == 2) {
68 			*ped = '\0';
69 			ped = escape_data;
70 			--escape_delay;
71 		}
72 		if (escape_delay == 1) {
73 			key = *ped++;
74 			if (!*ped)
75 				--escape_delay;
76 			break;
77 		}
78 		key = (*f)();
79 		if (key == -1) {
80 			if (escape_delay) {
81 				udelay(ESCAPE_UDELAY);
82 				--escape_delay;
83 			}
84 			continue;
85 		}
86 		if (bufsize <= 2) {
87 			if (key == '\r')
88 				key = '\n';
89 			*buffer++ = key;
90 			*buffer = '\0';
91 			return -1;
92 		}
93 		if (escape_delay == 0 && key == '\e') {
94 			escape_delay = ESCAPE_DELAY;
95 			ped = escape_data;
96 			f_escape = f;
97 		}
98 		if (escape_delay) {
99 			*ped++ = key;
100 			if (f_escape != f) {
101 				escape_delay = 2;
102 				continue;
103 			}
104 			if (ped - escape_data == 1) {
105 				/* \e */
106 				continue;
107 			} else if (ped - escape_data == 2) {
108 				/* \e<something> */
109 				if (key != '[')
110 					escape_delay = 2;
111 				continue;
112 			} else if (ped - escape_data == 3) {
113 				/* \e[<something> */
114 				int mapkey = 0;
115 				switch (key) {
116 				case 'A': /* \e[A, up arrow */
117 					mapkey = 16;
118 					break;
119 				case 'B': /* \e[B, down arrow */
120 					mapkey = 14;
121 					break;
122 				case 'C': /* \e[C, right arrow */
123 					mapkey = 6;
124 					break;
125 				case 'D': /* \e[D, left arrow */
126 					mapkey = 2;
127 					break;
128 				case '1': /* dropthrough */
129 				case '3': /* dropthrough */
130 				/* \e[<1,3,4>], may be home, del, end */
131 				case '4':
132 					mapkey = -1;
133 					break;
134 				}
135 				if (mapkey != -1) {
136 					if (mapkey > 0) {
137 						escape_data[0] = mapkey;
138 						escape_data[1] = '\0';
139 					}
140 					escape_delay = 2;
141 				}
142 				continue;
143 			} else if (ped - escape_data == 4) {
144 				/* \e[<1,3,4><something> */
145 				int mapkey = 0;
146 				if (key == '~') {
147 					switch (escape_data[2]) {
148 					case '1': /* \e[1~, home */
149 						mapkey = 1;
150 						break;
151 					case '3': /* \e[3~, del */
152 						mapkey = 4;
153 						break;
154 					case '4': /* \e[4~, end */
155 						mapkey = 5;
156 						break;
157 					}
158 				}
159 				if (mapkey > 0) {
160 					escape_data[0] = mapkey;
161 					escape_data[1] = '\0';
162 				}
163 				escape_delay = 2;
164 				continue;
165 			}
166 		}
167 		break;	/* A key to process */
168 	}
169 	return key;
170 }
171 
172 /*
173  * kdb_read
174  *
175  *	This function reads a string of characters, terminated by
176  *	a newline, or by reaching the end of the supplied buffer,
177  *	from the current kernel debugger console device.
178  * Parameters:
179  *	buffer	- Address of character buffer to receive input characters.
180  *	bufsize - size, in bytes, of the character buffer
181  * Returns:
182  *	Returns a pointer to the buffer containing the received
183  *	character string.  This string will be terminated by a
184  *	newline character.
185  * Locking:
186  *	No locks are required to be held upon entry to this
187  *	function.  It is not reentrant - it relies on the fact
188  *	that while kdb is running on only one "master debug" cpu.
189  * Remarks:
190  *
191  * The buffer size must be >= 2.  A buffer size of 2 means that the caller only
192  * wants a single key.
193  *
194  * An escape key could be the start of a vt100 control sequence such as \e[D
195  * (left arrow) or it could be a character in its own right.  The standard
196  * method for detecting the difference is to wait for 2 seconds to see if there
197  * are any other characters.  kdb is complicated by the lack of a timer service
198  * (interrupts are off), by multiple input sources and by the need to sometimes
199  * return after just one key.  Escape sequence processing has to be done as
200  * states in the polling loop.
201  */
202 
203 static char *kdb_read(char *buffer, size_t bufsize)
204 {
205 	char *cp = buffer;
206 	char *bufend = buffer+bufsize-2;	/* Reserve space for newline
207 						 * and null byte */
208 	char *lastchar;
209 	char *p_tmp;
210 	char tmp;
211 	static char tmpbuffer[CMD_BUFLEN];
212 	int len = strlen(buffer);
213 	int len_tmp;
214 	int tab = 0;
215 	int count;
216 	int i;
217 	int diag, dtab_count;
218 	int key;
219 
220 
221 	diag = kdbgetintenv("DTABCOUNT", &dtab_count);
222 	if (diag)
223 		dtab_count = 30;
224 
225 	if (len > 0) {
226 		cp += len;
227 		if (*(buffer+len-1) == '\n')
228 			cp--;
229 	}
230 
231 	lastchar = cp;
232 	*cp = '\0';
233 	kdb_printf("%s", buffer);
234 poll_again:
235 	key = kdb_read_get_key(buffer, bufsize);
236 	if (key == -1)
237 		return buffer;
238 	if (key != 9)
239 		tab = 0;
240 	switch (key) {
241 	case 8: /* backspace */
242 		if (cp > buffer) {
243 			if (cp < lastchar) {
244 				memcpy(tmpbuffer, cp, lastchar - cp);
245 				memcpy(cp-1, tmpbuffer, lastchar - cp);
246 			}
247 			*(--lastchar) = '\0';
248 			--cp;
249 			kdb_printf("\b%s \r", cp);
250 			tmp = *cp;
251 			*cp = '\0';
252 			kdb_printf(kdb_prompt_str);
253 			kdb_printf("%s", buffer);
254 			*cp = tmp;
255 		}
256 		break;
257 	case 13: /* enter */
258 		*lastchar++ = '\n';
259 		*lastchar++ = '\0';
260 		if (!KDB_STATE(KGDB_TRANS)) {
261 			KDB_STATE_SET(KGDB_TRANS);
262 			kdb_printf("%s", buffer);
263 		}
264 		kdb_printf("\n");
265 		return buffer;
266 	case 4: /* Del */
267 		if (cp < lastchar) {
268 			memcpy(tmpbuffer, cp+1, lastchar - cp - 1);
269 			memcpy(cp, tmpbuffer, lastchar - cp - 1);
270 			*(--lastchar) = '\0';
271 			kdb_printf("%s \r", cp);
272 			tmp = *cp;
273 			*cp = '\0';
274 			kdb_printf(kdb_prompt_str);
275 			kdb_printf("%s", buffer);
276 			*cp = tmp;
277 		}
278 		break;
279 	case 1: /* Home */
280 		if (cp > buffer) {
281 			kdb_printf("\r");
282 			kdb_printf(kdb_prompt_str);
283 			cp = buffer;
284 		}
285 		break;
286 	case 5: /* End */
287 		if (cp < lastchar) {
288 			kdb_printf("%s", cp);
289 			cp = lastchar;
290 		}
291 		break;
292 	case 2: /* Left */
293 		if (cp > buffer) {
294 			kdb_printf("\b");
295 			--cp;
296 		}
297 		break;
298 	case 14: /* Down */
299 		memset(tmpbuffer, ' ',
300 		       strlen(kdb_prompt_str) + (lastchar-buffer));
301 		*(tmpbuffer+strlen(kdb_prompt_str) +
302 		  (lastchar-buffer)) = '\0';
303 		kdb_printf("\r%s\r", tmpbuffer);
304 		*lastchar = (char)key;
305 		*(lastchar+1) = '\0';
306 		return lastchar;
307 	case 6: /* Right */
308 		if (cp < lastchar) {
309 			kdb_printf("%c", *cp);
310 			++cp;
311 		}
312 		break;
313 	case 16: /* Up */
314 		memset(tmpbuffer, ' ',
315 		       strlen(kdb_prompt_str) + (lastchar-buffer));
316 		*(tmpbuffer+strlen(kdb_prompt_str) +
317 		  (lastchar-buffer)) = '\0';
318 		kdb_printf("\r%s\r", tmpbuffer);
319 		*lastchar = (char)key;
320 		*(lastchar+1) = '\0';
321 		return lastchar;
322 	case 9: /* Tab */
323 		if (tab < 2)
324 			++tab;
325 		p_tmp = buffer;
326 		while (*p_tmp == ' ')
327 			p_tmp++;
328 		if (p_tmp > cp)
329 			break;
330 		memcpy(tmpbuffer, p_tmp, cp-p_tmp);
331 		*(tmpbuffer + (cp-p_tmp)) = '\0';
332 		p_tmp = strrchr(tmpbuffer, ' ');
333 		if (p_tmp)
334 			++p_tmp;
335 		else
336 			p_tmp = tmpbuffer;
337 		len = strlen(p_tmp);
338 		count = kallsyms_symbol_complete(p_tmp,
339 						 sizeof(tmpbuffer) -
340 						 (p_tmp - tmpbuffer));
341 		if (tab == 2 && count > 0) {
342 			kdb_printf("\n%d symbols are found.", count);
343 			if (count > dtab_count) {
344 				count = dtab_count;
345 				kdb_printf(" But only first %d symbols will"
346 					   " be printed.\nYou can change the"
347 					   " environment variable DTABCOUNT.",
348 					   count);
349 			}
350 			kdb_printf("\n");
351 			for (i = 0; i < count; i++) {
352 				if (kallsyms_symbol_next(p_tmp, i) < 0)
353 					break;
354 				kdb_printf("%s ", p_tmp);
355 				*(p_tmp + len) = '\0';
356 			}
357 			if (i >= dtab_count)
358 				kdb_printf("...");
359 			kdb_printf("\n");
360 			kdb_printf(kdb_prompt_str);
361 			kdb_printf("%s", buffer);
362 		} else if (tab != 2 && count > 0) {
363 			len_tmp = strlen(p_tmp);
364 			strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
365 			len_tmp = strlen(p_tmp);
366 			strncpy(cp, p_tmp+len, len_tmp-len + 1);
367 			len = len_tmp - len;
368 			kdb_printf("%s", cp);
369 			cp += len;
370 			lastchar += len;
371 		}
372 		kdb_nextline = 1; /* reset output line number */
373 		break;
374 	default:
375 		if (key >= 32 && lastchar < bufend) {
376 			if (cp < lastchar) {
377 				memcpy(tmpbuffer, cp, lastchar - cp);
378 				memcpy(cp+1, tmpbuffer, lastchar - cp);
379 				*++lastchar = '\0';
380 				*cp = key;
381 				kdb_printf("%s\r", cp);
382 				++cp;
383 				tmp = *cp;
384 				*cp = '\0';
385 				kdb_printf(kdb_prompt_str);
386 				kdb_printf("%s", buffer);
387 				*cp = tmp;
388 			} else {
389 				*++lastchar = '\0';
390 				*cp++ = key;
391 				/* The kgdb transition check will hide
392 				 * printed characters if we think that
393 				 * kgdb is connecting, until the check
394 				 * fails */
395 				if (!KDB_STATE(KGDB_TRANS)) {
396 					if (kgdb_transition_check(buffer))
397 						return buffer;
398 				} else {
399 					kdb_printf("%c", key);
400 				}
401 			}
402 			/* Special escape to kgdb */
403 			if (lastchar - buffer >= 5 &&
404 			    strcmp(lastchar - 5, "$?#3f") == 0) {
405 				kdb_gdb_state_pass(lastchar - 5);
406 				strcpy(buffer, "kgdb");
407 				KDB_STATE_SET(DOING_KGDB);
408 				return buffer;
409 			}
410 			if (lastchar - buffer >= 11 &&
411 			    strcmp(lastchar - 11, "$qSupported") == 0) {
412 				kdb_gdb_state_pass(lastchar - 11);
413 				strcpy(buffer, "kgdb");
414 				KDB_STATE_SET(DOING_KGDB);
415 				return buffer;
416 			}
417 		}
418 		break;
419 	}
420 	goto poll_again;
421 }
422 
423 /*
424  * kdb_getstr
425  *
426  *	Print the prompt string and read a command from the
427  *	input device.
428  *
429  * Parameters:
430  *	buffer	Address of buffer to receive command
431  *	bufsize Size of buffer in bytes
432  *	prompt	Pointer to string to use as prompt string
433  * Returns:
434  *	Pointer to command buffer.
435  * Locking:
436  *	None.
437  * Remarks:
438  *	For SMP kernels, the processor number will be
439  *	substituted for %d, %x or %o in the prompt.
440  */
441 
442 char *kdb_getstr(char *buffer, size_t bufsize, char *prompt)
443 {
444 	if (prompt && kdb_prompt_str != prompt)
445 		strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
446 	kdb_printf(kdb_prompt_str);
447 	kdb_nextline = 1;	/* Prompt and input resets line number */
448 	return kdb_read(buffer, bufsize);
449 }
450 
451 /*
452  * kdb_input_flush
453  *
454  *	Get rid of any buffered console input.
455  *
456  * Parameters:
457  *	none
458  * Returns:
459  *	nothing
460  * Locking:
461  *	none
462  * Remarks:
463  *	Call this function whenever you want to flush input.  If there is any
464  *	outstanding input, it ignores all characters until there has been no
465  *	data for approximately 1ms.
466  */
467 
468 static void kdb_input_flush(void)
469 {
470 	get_char_func *f;
471 	int res;
472 	int flush_delay = 1;
473 	while (flush_delay) {
474 		flush_delay--;
475 empty:
476 		touch_nmi_watchdog();
477 		for (f = &kdb_poll_funcs[0]; *f; ++f) {
478 			res = (*f)();
479 			if (res != -1) {
480 				flush_delay = 1;
481 				goto empty;
482 			}
483 		}
484 		if (flush_delay)
485 			mdelay(1);
486 	}
487 }
488 
489 /*
490  * kdb_printf
491  *
492  *	Print a string to the output device(s).
493  *
494  * Parameters:
495  *	printf-like format and optional args.
496  * Returns:
497  *	0
498  * Locking:
499  *	None.
500  * Remarks:
501  *	use 'kdbcons->write()' to avoid polluting 'log_buf' with
502  *	kdb output.
503  *
504  *  If the user is doing a cmd args | grep srch
505  *  then kdb_grepping_flag is set.
506  *  In that case we need to accumulate full lines (ending in \n) before
507  *  searching for the pattern.
508  */
509 
510 static char kdb_buffer[256];	/* A bit too big to go on stack */
511 static char *next_avail = kdb_buffer;
512 static int  size_avail;
513 static int  suspend_grep;
514 
515 /*
516  * search arg1 to see if it contains arg2
517  * (kdmain.c provides flags for ^pat and pat$)
518  *
519  * return 1 for found, 0 for not found
520  */
521 static int kdb_search_string(char *searched, char *searchfor)
522 {
523 	char firstchar, *cp;
524 	int len1, len2;
525 
526 	/* not counting the newline at the end of "searched" */
527 	len1 = strlen(searched)-1;
528 	len2 = strlen(searchfor);
529 	if (len1 < len2)
530 		return 0;
531 	if (kdb_grep_leading && kdb_grep_trailing && len1 != len2)
532 		return 0;
533 	if (kdb_grep_leading) {
534 		if (!strncmp(searched, searchfor, len2))
535 			return 1;
536 	} else if (kdb_grep_trailing) {
537 		if (!strncmp(searched+len1-len2, searchfor, len2))
538 			return 1;
539 	} else {
540 		firstchar = *searchfor;
541 		cp = searched;
542 		while ((cp = strchr(cp, firstchar))) {
543 			if (!strncmp(cp, searchfor, len2))
544 				return 1;
545 			cp++;
546 		}
547 	}
548 	return 0;
549 }
550 
551 int vkdb_printf(const char *fmt, va_list ap)
552 {
553 	int diag;
554 	int linecount;
555 	int logging, saved_loglevel = 0;
556 	int saved_trap_printk;
557 	int got_printf_lock = 0;
558 	int retlen = 0;
559 	int fnd, len;
560 	char *cp, *cp2, *cphold = NULL, replaced_byte = ' ';
561 	char *moreprompt = "more> ";
562 	struct console *c = console_drivers;
563 	static DEFINE_SPINLOCK(kdb_printf_lock);
564 	unsigned long uninitialized_var(flags);
565 
566 	preempt_disable();
567 	saved_trap_printk = kdb_trap_printk;
568 	kdb_trap_printk = 0;
569 
570 	/* Serialize kdb_printf if multiple cpus try to write at once.
571 	 * But if any cpu goes recursive in kdb, just print the output,
572 	 * even if it is interleaved with any other text.
573 	 */
574 	if (!KDB_STATE(PRINTF_LOCK)) {
575 		KDB_STATE_SET(PRINTF_LOCK);
576 		spin_lock_irqsave(&kdb_printf_lock, flags);
577 		got_printf_lock = 1;
578 		atomic_inc(&kdb_event);
579 	} else {
580 		__acquire(kdb_printf_lock);
581 	}
582 
583 	diag = kdbgetintenv("LINES", &linecount);
584 	if (diag || linecount <= 1)
585 		linecount = 24;
586 
587 	diag = kdbgetintenv("LOGGING", &logging);
588 	if (diag)
589 		logging = 0;
590 
591 	if (!kdb_grepping_flag || suspend_grep) {
592 		/* normally, every vsnprintf starts a new buffer */
593 		next_avail = kdb_buffer;
594 		size_avail = sizeof(kdb_buffer);
595 	}
596 	vsnprintf(next_avail, size_avail, fmt, ap);
597 
598 	/*
599 	 * If kdb_parse() found that the command was cmd xxx | grep yyy
600 	 * then kdb_grepping_flag is set, and kdb_grep_string contains yyy
601 	 *
602 	 * Accumulate the print data up to a newline before searching it.
603 	 * (vsnprintf does null-terminate the string that it generates)
604 	 */
605 
606 	/* skip the search if prints are temporarily unconditional */
607 	if (!suspend_grep && kdb_grepping_flag) {
608 		cp = strchr(kdb_buffer, '\n');
609 		if (!cp) {
610 			/*
611 			 * Special cases that don't end with newlines
612 			 * but should be written without one:
613 			 *   The "[nn]kdb> " prompt should
614 			 *   appear at the front of the buffer.
615 			 *
616 			 *   The "[nn]more " prompt should also be
617 			 *     (MOREPROMPT -> moreprompt)
618 			 *   written *   but we print that ourselves,
619 			 *   we set the suspend_grep flag to make
620 			 *   it unconditional.
621 			 *
622 			 */
623 			if (next_avail == kdb_buffer) {
624 				/*
625 				 * these should occur after a newline,
626 				 * so they will be at the front of the
627 				 * buffer
628 				 */
629 				cp2 = kdb_buffer;
630 				len = strlen(kdb_prompt_str);
631 				if (!strncmp(cp2, kdb_prompt_str, len)) {
632 					/*
633 					 * We're about to start a new
634 					 * command, so we can go back
635 					 * to normal mode.
636 					 */
637 					kdb_grepping_flag = 0;
638 					goto kdb_printit;
639 				}
640 			}
641 			/* no newline; don't search/write the buffer
642 			   until one is there */
643 			len = strlen(kdb_buffer);
644 			next_avail = kdb_buffer + len;
645 			size_avail = sizeof(kdb_buffer) - len;
646 			goto kdb_print_out;
647 		}
648 
649 		/*
650 		 * The newline is present; print through it or discard
651 		 * it, depending on the results of the search.
652 		 */
653 		cp++;	 	     /* to byte after the newline */
654 		replaced_byte = *cp; /* remember what/where it was */
655 		cphold = cp;
656 		*cp = '\0';	     /* end the string for our search */
657 
658 		/*
659 		 * We now have a newline at the end of the string
660 		 * Only continue with this output if it contains the
661 		 * search string.
662 		 */
663 		fnd = kdb_search_string(kdb_buffer, kdb_grep_string);
664 		if (!fnd) {
665 			/*
666 			 * At this point the complete line at the start
667 			 * of kdb_buffer can be discarded, as it does
668 			 * not contain what the user is looking for.
669 			 * Shift the buffer left.
670 			 */
671 			*cphold = replaced_byte;
672 			strcpy(kdb_buffer, cphold);
673 			len = strlen(kdb_buffer);
674 			next_avail = kdb_buffer + len;
675 			size_avail = sizeof(kdb_buffer) - len;
676 			goto kdb_print_out;
677 		}
678 		/*
679 		 * at this point the string is a full line and
680 		 * should be printed, up to the null.
681 		 */
682 	}
683 kdb_printit:
684 
685 	/*
686 	 * Write to all consoles.
687 	 */
688 	retlen = strlen(kdb_buffer);
689 	if (!dbg_kdb_mode && kgdb_connected) {
690 		gdbstub_msg_write(kdb_buffer, retlen);
691 	} else {
692 		if (dbg_io_ops && !dbg_io_ops->is_console) {
693 			len = strlen(kdb_buffer);
694 			cp = kdb_buffer;
695 			while (len--) {
696 				dbg_io_ops->write_char(*cp);
697 				cp++;
698 			}
699 		}
700 		while (c) {
701 			c->write(c, kdb_buffer, retlen);
702 			touch_nmi_watchdog();
703 			c = c->next;
704 		}
705 	}
706 	if (logging) {
707 		saved_loglevel = console_loglevel;
708 		console_loglevel = 0;
709 		printk(KERN_INFO "%s", kdb_buffer);
710 	}
711 
712 	if (KDB_STATE(PAGER) && strchr(kdb_buffer, '\n'))
713 		kdb_nextline++;
714 
715 	/* check for having reached the LINES number of printed lines */
716 	if (kdb_nextline == linecount) {
717 		char buf1[16] = "";
718 
719 		/* Watch out for recursion here.  Any routine that calls
720 		 * kdb_printf will come back through here.  And kdb_read
721 		 * uses kdb_printf to echo on serial consoles ...
722 		 */
723 		kdb_nextline = 1;	/* In case of recursion */
724 
725 		/*
726 		 * Pause until cr.
727 		 */
728 		moreprompt = kdbgetenv("MOREPROMPT");
729 		if (moreprompt == NULL)
730 			moreprompt = "more> ";
731 
732 		kdb_input_flush();
733 		c = console_drivers;
734 
735 		if (dbg_io_ops && !dbg_io_ops->is_console) {
736 			len = strlen(moreprompt);
737 			cp = moreprompt;
738 			while (len--) {
739 				dbg_io_ops->write_char(*cp);
740 				cp++;
741 			}
742 		}
743 		while (c) {
744 			c->write(c, moreprompt, strlen(moreprompt));
745 			touch_nmi_watchdog();
746 			c = c->next;
747 		}
748 
749 		if (logging)
750 			printk("%s", moreprompt);
751 
752 		kdb_read(buf1, 2); /* '2' indicates to return
753 				    * immediately after getting one key. */
754 		kdb_nextline = 1;	/* Really set output line 1 */
755 
756 		/* empty and reset the buffer: */
757 		kdb_buffer[0] = '\0';
758 		next_avail = kdb_buffer;
759 		size_avail = sizeof(kdb_buffer);
760 		if ((buf1[0] == 'q') || (buf1[0] == 'Q')) {
761 			/* user hit q or Q */
762 			KDB_FLAG_SET(CMD_INTERRUPT); /* command interrupted */
763 			KDB_STATE_CLEAR(PAGER);
764 			/* end of command output; back to normal mode */
765 			kdb_grepping_flag = 0;
766 			kdb_printf("\n");
767 		} else if (buf1[0] == ' ') {
768 			kdb_printf("\n");
769 			suspend_grep = 1; /* for this recursion */
770 		} else if (buf1[0] == '\n') {
771 			kdb_nextline = linecount - 1;
772 			kdb_printf("\r");
773 			suspend_grep = 1; /* for this recursion */
774 		} else if (buf1[0] && buf1[0] != '\n') {
775 			/* user hit something other than enter */
776 			suspend_grep = 1; /* for this recursion */
777 			kdb_printf("\nOnly 'q' or 'Q' are processed at more "
778 				   "prompt, input ignored\n");
779 		} else if (kdb_grepping_flag) {
780 			/* user hit enter */
781 			suspend_grep = 1; /* for this recursion */
782 			kdb_printf("\n");
783 		}
784 		kdb_input_flush();
785 	}
786 
787 	/*
788 	 * For grep searches, shift the printed string left.
789 	 *  replaced_byte contains the character that was overwritten with
790 	 *  the terminating null, and cphold points to the null.
791 	 * Then adjust the notion of available space in the buffer.
792 	 */
793 	if (kdb_grepping_flag && !suspend_grep) {
794 		*cphold = replaced_byte;
795 		strcpy(kdb_buffer, cphold);
796 		len = strlen(kdb_buffer);
797 		next_avail = kdb_buffer + len;
798 		size_avail = sizeof(kdb_buffer) - len;
799 	}
800 
801 kdb_print_out:
802 	suspend_grep = 0; /* end of what may have been a recursive call */
803 	if (logging)
804 		console_loglevel = saved_loglevel;
805 	if (KDB_STATE(PRINTF_LOCK) && got_printf_lock) {
806 		got_printf_lock = 0;
807 		spin_unlock_irqrestore(&kdb_printf_lock, flags);
808 		KDB_STATE_CLEAR(PRINTF_LOCK);
809 		atomic_dec(&kdb_event);
810 	} else {
811 		__release(kdb_printf_lock);
812 	}
813 	kdb_trap_printk = saved_trap_printk;
814 	preempt_enable();
815 	return retlen;
816 }
817 
818 int kdb_printf(const char *fmt, ...)
819 {
820 	va_list ap;
821 	int r;
822 
823 	va_start(ap, fmt);
824 	r = vkdb_printf(fmt, ap);
825 	va_end(ap);
826 
827 	return r;
828 }
829 EXPORT_SYMBOL_GPL(kdb_printf);
830