kernel/debug/kdb/kdb_io.c

   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/types.h>
  13 #include <linux/ctype.h>
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/kdev_t.h>
  17 #include <linux/console.h>
  18 #include <linux/string.h>
  19 #include <linux/sched.h>
  20 #include <linux/smp.h>
  21 #include <linux/nmi.h>
  22 #include <linux/delay.h>
  23 #include <linux/kgdb.h>
  24 #include <linux/kdb.h>
  25 #include <linux/kallsyms.h>
  26 #include "kdb_private.h"
  27
  28 #define CMD_BUFLEN 256
  29 char kdb_prompt_str[CMD_BUFLEN];
  30
  31 int kdb_trap_printk;
  32 int kdb_printf_cpu = -1;
  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 /**
  52  * kdb_handle_escape() - validity check on an accumulated escape sequence.
  53  * @buf:        Accumulated escape characters to be examined. Note that buf
  54  *              is not a string, it is an array of characters and need not be
  55  *              nil terminated.
  56  * @sz:         Number of accumulated escape characters.
  57  *
  58  * Return: -1 if the escape sequence is unwanted, 0 if it is incomplete,
  59  * otherwise it returns a mapped key value to pass to the upper layers.
  60  */
  61 static int kdb_handle_escape(char *buf, size_t sz)
  62 {
  63         char *lastkey = buf + sz - 1;
  64
  65         switch (sz) {
  66         case 1:
  67                 if (*lastkey == '\e')
  68                         return 0;
  69                 break;
  70
  71         case 2: /* \e<something> */
  72                 if (*lastkey == '[')
  73                         return 0;
  74                 break;
  75
  76         case 3:
  77                 switch (*lastkey) {
  78                 case 'A': /* \e[A, up arrow */
  79                         return 16;
  80                 case 'B': /* \e[B, down arrow */
  81                         return 14;
  82                 case 'C': /* \e[C, right arrow */
  83                         return 6;
  84                 case 'D': /* \e[D, left arrow */
  85                         return 2;
  86                 case '1': /* \e[<1,3,4>], may be home, del, end */
  87                 case '3':
  88                 case '4':
  89                         return 0;
  90                 }
  91                 break;
  92
  93         case 4:
  94                 if (*lastkey == '~') {
  95                         switch (buf[2]) {
  96                         case '1': /* \e[1~, home */
  97                                 return 1;
  98                         case '3': /* \e[3~, del */
  99                                 return 4;
 100                         case '4': /* \e[4~, end */
 101                                 return 5;
 102                         }
 103                 }
 104                 break;
 105         }
 106
 107         return -1;
 108 }
 109
 110 /**
 111  * kdb_getchar() - Read a single character from a kdb console (or consoles).
 112  *
 113  * Other than polling the various consoles that are currently enabled,
 114  * most of the work done in this function is dealing with escape sequences.
 115  *
 116  * An escape key could be the start of a vt100 control sequence such as \e[D
 117  * (left arrow) or it could be a character in its own right.  The standard
 118  * method for detecting the difference is to wait for 2 seconds to see if there
 119  * are any other characters.  kdb is complicated by the lack of a timer service
 120  * (interrupts are off), by multiple input sources. Escape sequence processing
 121  * has to be done as states in the polling loop.
 122  *
 123  * Return: The key pressed or a control code derived from an escape sequence.
 124  */
 125 char kdb_getchar(void)
 126 {
 127 #define ESCAPE_UDELAY 1000
 128 #define ESCAPE_DELAY (2*1000000/ESCAPE_UDELAY) /* 2 seconds worth of udelays */
 129         char buf[4];    /* longest vt100 escape sequence is 4 bytes */
 130         char *pbuf = buf;
 131         int escape_delay = 0;
 132         get_char_func *f, *f_prev = NULL;
 133         int key;
 134
 135         for (f = &kdb_poll_funcs[0]; ; ++f) {
 136                 if (*f == NULL) {
 137                         /* Reset NMI watchdog once per poll loop */
 138                         touch_nmi_watchdog();
 139                         f = &kdb_poll_funcs[0];
 140                 }
 141
 142                 key = (*f)();
 143                 if (key == -1) {
 144                         if (escape_delay) {
 145                                 udelay(ESCAPE_UDELAY);
 146                                 if (--escape_delay == 0)
 147                                         return '\e';
 148                         }
 149                         continue;
 150                 }
 151
 152                 /*
 153                  * When the first character is received (or we get a change
 154                  * input source) we set ourselves up to handle an escape
 155                  * sequences (just in case).
 156                  */
 157                 if (f_prev != f) {
 158                         f_prev = f;
 159                         pbuf = buf;
 160                         escape_delay = ESCAPE_DELAY;
 161                 }
 162
 163                 *pbuf++ = key;
 164                 key = kdb_handle_escape(buf, pbuf - buf);
 165                 if (key < 0) /* no escape sequence; return best character */
 166                         return buf[pbuf - buf == 2 ? 1 : 0];
 167                 if (key > 0)
 168                         return key;
 169         }
 170
 171         unreachable();
 172 }
 173
 174 /*
 175  * kdb_read
 176  *
 177  *      This function reads a string of characters, terminated by
 178  *      a newline, or by reaching the end of the supplied buffer,
 179  *      from the current kernel debugger console device.
 180  * Parameters:
 181  *      buffer  - Address of character buffer to receive input characters.
 182  *      bufsize - size, in bytes, of the character buffer
 183  * Returns:
 184  *      Returns a pointer to the buffer containing the received
 185  *      character string.  This string will be terminated by a
 186  *      newline character.
 187  * Locking:
 188  *      No locks are required to be held upon entry to this
 189  *      function.  It is not reentrant - it relies on the fact
 190  *      that while kdb is running on only one "master debug" cpu.
 191  * Remarks:
 192  *      The buffer size must be >= 2.
 193  */
 194
 195 static char *kdb_read(char *buffer, size_t bufsize)
 196 {
 197         char *cp = buffer;
 198         char *bufend = buffer+bufsize-2;        /* Reserve space for newline
 199                                                  * and null byte */
 200         char *lastchar;
 201         char *p_tmp;
 202         char tmp;
 203         static char tmpbuffer[CMD_BUFLEN];
 204         int len = strlen(buffer);
 205         int len_tmp;
 206         int tab = 0;
 207         int count;
 208         int i;
 209         int diag, dtab_count;
 210         int key, buf_size, ret;
 211
 212
 213         diag = kdbgetintenv("DTABCOUNT", &dtab_count);
 214         if (diag)
 215                 dtab_count = 30;
 216
 217         if (len > 0) {
 218                 cp += len;
 219                 if (*(buffer+len-1) == '\n')
 220                         cp--;
 221         }
 222
 223         lastchar = cp;
 224         *cp = '\0';
 225         kdb_printf("%s", buffer);
 226 poll_again:
 227         key = kdb_getchar();
 228         if (key != 9)
 229                 tab = 0;
 230         switch (key) {
 231         case 8: /* backspace */
 232                 if (cp > buffer) {
 233                         if (cp < lastchar) {
 234                                 memcpy(tmpbuffer, cp, lastchar - cp);
 235                                 memcpy(cp-1, tmpbuffer, lastchar - cp);
 236                         }
 237                         *(--lastchar) = '\0';
 238                         --cp;
 239                         kdb_printf("\b%s \r", cp);
 240                         tmp = *cp;
 241                         *cp = '\0';
 242                         kdb_printf(kdb_prompt_str);
 243                         kdb_printf("%s", buffer);
 244                         *cp = tmp;
 245                 }
 246                 break;
 247         case 13: /* enter */
 248                 *lastchar++ = '\n';
 249                 *lastchar++ = '\0';
 250                 if (!KDB_STATE(KGDB_TRANS)) {
 251                         KDB_STATE_SET(KGDB_TRANS);
 252                         kdb_printf("%s", buffer);
 253                 }
 254                 kdb_printf("\n");
 255                 return buffer;
 256         case 4: /* Del */
 257                 if (cp < lastchar) {
 258                         memcpy(tmpbuffer, cp+1, lastchar - cp - 1);
 259                         memcpy(cp, tmpbuffer, lastchar - cp - 1);
 260                         *(--lastchar) = '\0';
 261                         kdb_printf("%s \r", cp);
 262                         tmp = *cp;
 263                         *cp = '\0';
 264                         kdb_printf(kdb_prompt_str);
 265                         kdb_printf("%s", buffer);
 266                         *cp = tmp;
 267                 }
 268                 break;
 269         case 1: /* Home */
 270                 if (cp > buffer) {
 271                         kdb_printf("\r");
 272                         kdb_printf(kdb_prompt_str);
 273                         cp = buffer;
 274                 }
 275                 break;
 276         case 5: /* End */
 277                 if (cp < lastchar) {
 278                         kdb_printf("%s", cp);
 279                         cp = lastchar;
 280                 }
 281                 break;
 282         case 2: /* Left */
 283                 if (cp > buffer) {
 284                         kdb_printf("\b");
 285                         --cp;
 286                 }
 287                 break;
 288         case 14: /* Down */
 289                 memset(tmpbuffer, ' ',
 290                        strlen(kdb_prompt_str) + (lastchar-buffer));
 291                 *(tmpbuffer+strlen(kdb_prompt_str) +
 292                   (lastchar-buffer)) = '\0';
 293                 kdb_printf("\r%s\r", tmpbuffer);
 294                 *lastchar = (char)key;
 295                 *(lastchar+1) = '\0';
 296                 return lastchar;
 297         case 6: /* Right */
 298                 if (cp < lastchar) {
 299                         kdb_printf("%c", *cp);
 300                         ++cp;
 301                 }
 302                 break;
 303         case 16: /* Up */
 304                 memset(tmpbuffer, ' ',
 305                        strlen(kdb_prompt_str) + (lastchar-buffer));
 306                 *(tmpbuffer+strlen(kdb_prompt_str) +
 307                   (lastchar-buffer)) = '\0';
 308                 kdb_printf("\r%s\r", tmpbuffer);
 309                 *lastchar = (char)key;
 310                 *(lastchar+1) = '\0';
 311                 return lastchar;
 312         case 9: /* Tab */
 313                 if (tab < 2)
 314                         ++tab;
 315                 p_tmp = buffer;
 316                 while (*p_tmp == ' ')
 317                         p_tmp++;
 318                 if (p_tmp > cp)
 319                         break;
 320                 memcpy(tmpbuffer, p_tmp, cp-p_tmp);
 321                 *(tmpbuffer + (cp-p_tmp)) = '\0';
 322                 p_tmp = strrchr(tmpbuffer, ' ');
 323                 if (p_tmp)
 324                         ++p_tmp;
 325                 else
 326                         p_tmp = tmpbuffer;
 327                 len = strlen(p_tmp);
 328                 buf_size = sizeof(tmpbuffer) - (p_tmp - tmpbuffer);
 329                 count = kallsyms_symbol_complete(p_tmp, buf_size);
 330                 if (tab == 2 && count > 0) {
 331                         kdb_printf("\n%d symbols are found.", count);
 332                         if (count > dtab_count) {
 333                                 count = dtab_count;
 334                                 kdb_printf(" But only first %d symbols will"
 335                                            " be printed.\nYou can change the"
 336                                            " environment variable DTABCOUNT.",
 337                                            count);
 338                         }
 339                         kdb_printf("\n");
 340                         for (i = 0; i < count; i++) {
 341                                 ret = kallsyms_symbol_next(p_tmp, i, buf_size);
 342                                 if (WARN_ON(!ret))
 343                                         break;
 344                                 if (ret != -E2BIG)
 345                                         kdb_printf("%s ", p_tmp);
 346                                 else
 347                                         kdb_printf("%s... ", p_tmp);
 348                                 *(p_tmp + len) = '\0';
 349                         }
 350                         if (i >= dtab_count)
 351                                 kdb_printf("...");
 352                         kdb_printf("\n");
 353                         kdb_printf(kdb_prompt_str);
 354                         kdb_printf("%s", buffer);
 355                 } else if (tab != 2 && count > 0) {
 356                         len_tmp = strlen(p_tmp);
 357                         strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
 358                         len_tmp = strlen(p_tmp);
 359                         strncpy(cp, p_tmp+len, len_tmp-len + 1);
 360                         len = len_tmp - len;
 361                         kdb_printf("%s", cp);
 362                         cp += len;
 363                         lastchar += len;
 364                 }
 365                 kdb_nextline = 1; /* reset output line number */
 366                 break;
 367         default:
 368                 if (key >= 32 && lastchar < bufend) {
 369                         if (cp < lastchar) {
 370                                 memcpy(tmpbuffer, cp, lastchar - cp);
 371                                 memcpy(cp+1, tmpbuffer, lastchar - cp);
 372                                 *++lastchar = '\0';
 373                                 *cp = key;
 374                                 kdb_printf("%s\r", cp);
 375                                 ++cp;
 376                                 tmp = *cp;
 377                                 *cp = '\0';
 378                                 kdb_printf(kdb_prompt_str);
 379                                 kdb_printf("%s", buffer);
 380                                 *cp = tmp;
 381                         } else {
 382                                 *++lastchar = '\0';
 383                                 *cp++ = key;
 384                                 /* The kgdb transition check will hide
 385                                  * printed characters if we think that
 386                                  * kgdb is connecting, until the check
 387                                  * fails */
 388                                 if (!KDB_STATE(KGDB_TRANS)) {
 389                                         if (kgdb_transition_check(buffer))
 390                                                 return buffer;
 391                                 } else {
 392                                         kdb_printf("%c", key);
 393                                 }
 394                         }
 395                         /* Special escape to kgdb */
 396                         if (lastchar - buffer >= 5 &&
 397                             strcmp(lastchar - 5, "$?#3f") == 0) {
 398                                 kdb_gdb_state_pass(lastchar - 5);
 399                                 strcpy(buffer, "kgdb");
 400                                 KDB_STATE_SET(DOING_KGDB);
 401                                 return buffer;
 402                         }
 403                         if (lastchar - buffer >= 11 &&
 404                             strcmp(lastchar - 11, "$qSupported") == 0) {
 405                                 kdb_gdb_state_pass(lastchar - 11);
 406                                 strcpy(buffer, "kgdb");
 407                                 KDB_STATE_SET(DOING_KGDB);
 408                                 return buffer;
 409                         }
 410                 }
 411                 break;
 412         }
 413         goto poll_again;
 414 }
 415
 416 /*
 417  * kdb_getstr
 418  *
 419  *      Print the prompt string and read a command from the
 420  *      input device.
 421  *
 422  * Parameters:
 423  *      buffer  Address of buffer to receive command
 424  *      bufsize Size of buffer in bytes
 425  *      prompt  Pointer to string to use as prompt string
 426  * Returns:
 427  *      Pointer to command buffer.
 428  * Locking:
 429  *      None.
 430  * Remarks:
 431  *      For SMP kernels, the processor number will be
 432  *      substituted for %d, %x or %o in the prompt.
 433  */
 434
 435 char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
 436 {
 437         if (prompt && kdb_prompt_str != prompt)
 438                 strscpy(kdb_prompt_str, prompt, CMD_BUFLEN);
 439         kdb_printf(kdb_prompt_str);
 440         kdb_nextline = 1;       /* Prompt and input resets line number */
 441         return kdb_read(buffer, bufsize);
 442 }
 443
 444 /*
 445  * kdb_input_flush
 446  *
 447  *      Get rid of any buffered console input.
 448  *
 449  * Parameters:
 450  *      none
 451  * Returns:
 452  *      nothing
 453  * Locking:
 454  *      none
 455  * Remarks:
 456  *      Call this function whenever you want to flush input.  If there is any
 457  *      outstanding input, it ignores all characters until there has been no
 458  *      data for approximately 1ms.
 459  */
 460
 461 static void kdb_input_flush(void)
 462 {
 463         get_char_func *f;
 464         int res;
 465         int flush_delay = 1;
 466         while (flush_delay) {
 467                 flush_delay--;
 468 empty:
 469                 touch_nmi_watchdog();
 470                 for (f = &kdb_poll_funcs[0]; *f; ++f) {
 471                         res = (*f)();
 472                         if (res != -1) {
 473                                 flush_delay = 1;
 474                                 goto empty;
 475                         }
 476                 }
 477                 if (flush_delay)
 478                         mdelay(1);
 479         }
 480 }
 481
 482 /*
 483  * kdb_printf
 484  *
 485  *      Print a string to the output device(s).
 486  *
 487  * Parameters:
 488  *      printf-like format and optional args.
 489  * Returns:
 490  *      0
 491  * Locking:
 492  *      None.
 493  * Remarks:
 494  *      use 'kdbcons->write()' to avoid polluting 'log_buf' with
 495  *      kdb output.
 496  *
 497  *  If the user is doing a cmd args | grep srch
 498  *  then kdb_grepping_flag is set.
 499  *  In that case we need to accumulate full lines (ending in \n) before
 500  *  searching for the pattern.
 501  */
 502
 503 static char kdb_buffer[256];    /* A bit too big to go on stack */
 504 static char *next_avail = kdb_buffer;
 505 static int  size_avail;
 506 static int  suspend_grep;
 507
 508 /*
 509  * search arg1 to see if it contains arg2
 510  * (kdmain.c provides flags for ^pat and pat$)
 511  *
 512  * return 1 for found, 0 for not found
 513  */
 514 static int kdb_search_string(char *searched, char *searchfor)
 515 {
 516         char firstchar, *cp;
 517         int len1, len2;
 518
 519         /* not counting the newline at the end of "searched" */
 520         len1 = strlen(searched)-1;
 521         len2 = strlen(searchfor);
 522         if (len1 < len2)
 523                 return 0;
 524         if (kdb_grep_leading && kdb_grep_trailing && len1 != len2)
 525                 return 0;
 526         if (kdb_grep_leading) {
 527                 if (!strncmp(searched, searchfor, len2))
 528                         return 1;
 529         } else if (kdb_grep_trailing) {
 530                 if (!strncmp(searched+len1-len2, searchfor, len2))
 531                         return 1;
 532         } else {
 533                 firstchar = *searchfor;
 534                 cp = searched;
 535                 while ((cp = strchr(cp, firstchar))) {
 536                         if (!strncmp(cp, searchfor, len2))
 537                                 return 1;
 538                         cp++;
 539                 }
 540         }
 541         return 0;
 542 }
 543
 544 static void kdb_msg_write(const char *msg, int msg_len)
 545 {
 546         struct console *c;
 547         const char *cp;
 548         int cookie;
 549         int len;
 550
 551         if (msg_len == 0)
 552                 return;
 553
 554         cp = msg;
 555         len = msg_len;
 556
 557         while (len--) {
 558                 dbg_io_ops->write_char(*cp);
 559                 cp++;
 560         }
 561
 562         /*
 563          * The console_srcu_read_lock() only provides safe console list
 564          * traversal. The use of the ->write() callback relies on all other
 565          * CPUs being stopped at the moment and console drivers being able to
 566          * handle reentrance when @oops_in_progress is set.
 567          *
 568          * There is no guarantee that every console driver can handle
 569          * reentrance in this way; the developer deploying the debugger
 570          * is responsible for ensuring that the console drivers they
 571          * have selected handle reentrance appropriately.
 572          */
 573         cookie = console_srcu_read_lock();
 574         for_each_console_srcu(c) {
 575                 if (!(console_srcu_read_flags(c) & CON_ENABLED))
 576                         continue;
 577                 if (c == dbg_io_ops->cons)
 578                         continue;
 579                 /*
 580                  * Set oops_in_progress to encourage the console drivers to
 581                  * disregard their internal spin locks: in the current calling
 582                  * context the risk of deadlock is a bigger problem than risks
 583                  * due to re-entering the console driver. We operate directly on
 584                  * oops_in_progress rather than using bust_spinlocks() because
 585                  * the calls bust_spinlocks() makes on exit are not appropriate
 586                  * for this calling context.
 587                  */
 588                 ++oops_in_progress;
 589                 c->write(c, msg, msg_len);
 590                 --oops_in_progress;
 591                 touch_nmi_watchdog();
 592         }
 593         console_srcu_read_unlock(cookie);
 594 }
 595
 596 int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
 597 {
 598         int diag;
 599         int linecount;
 600         int colcount;
 601         int logging, saved_loglevel = 0;
 602         int retlen = 0;
 603         int fnd, len;
 604         int this_cpu, old_cpu;
 605         char *cp, *cp2, *cphold = NULL, replaced_byte = ' ';
 606         char *moreprompt = "more> ";
 607         unsigned long flags;
 608
 609         /* Serialize kdb_printf if multiple cpus try to write at once.
 610          * But if any cpu goes recursive in kdb, just print the output,
 611          * even if it is interleaved with any other text.
 612          */
 613         local_irq_save(flags);
 614         this_cpu = smp_processor_id();
 615         for (;;) {
 616                 old_cpu = cmpxchg(&kdb_printf_cpu, -1, this_cpu);
 617                 if (old_cpu == -1 || old_cpu == this_cpu)
 618                         break;
 619
 620                 cpu_relax();
 621         }
 622
 623         diag = kdbgetintenv("LINES", &linecount);
 624         if (diag || linecount <= 1)
 625                 linecount = 24;
 626
 627         diag = kdbgetintenv("COLUMNS", &colcount);
 628         if (diag || colcount <= 1)
 629                 colcount = 80;
 630
 631         diag = kdbgetintenv("LOGGING", &logging);
 632         if (diag)
 633                 logging = 0;
 634
 635         if (!kdb_grepping_flag || suspend_grep) {
 636                 /* normally, every vsnprintf starts a new buffer */
 637                 next_avail = kdb_buffer;
 638                 size_avail = sizeof(kdb_buffer);
 639         }
 640         vsnprintf(next_avail, size_avail, fmt, ap);
 641
 642         /*
 643          * If kdb_parse() found that the command was cmd xxx | grep yyy
 644          * then kdb_grepping_flag is set, and kdb_grep_string contains yyy
 645          *
 646          * Accumulate the print data up to a newline before searching it.
 647          * (vsnprintf does null-terminate the string that it generates)
 648          */
 649
 650         /* skip the search if prints are temporarily unconditional */
 651         if (!suspend_grep && kdb_grepping_flag) {
 652                 cp = strchr(kdb_buffer, '\n');
 653                 if (!cp) {
 654                         /*
 655                          * Special cases that don't end with newlines
 656                          * but should be written without one:
 657                          *   The "[nn]kdb> " prompt should
 658                          *   appear at the front of the buffer.
 659                          *
 660                          *   The "[nn]more " prompt should also be
 661                          *     (MOREPROMPT -> moreprompt)
 662                          *   written *   but we print that ourselves,
 663                          *   we set the suspend_grep flag to make
 664                          *   it unconditional.
 665                          *
 666                          */
 667                         if (next_avail == kdb_buffer) {
 668                                 /*
 669                                  * these should occur after a newline,
 670                                  * so they will be at the front of the
 671                                  * buffer
 672                                  */
 673                                 cp2 = kdb_buffer;
 674                                 len = strlen(kdb_prompt_str);
 675                                 if (!strncmp(cp2, kdb_prompt_str, len)) {
 676                                         /*
 677                                          * We're about to start a new
 678                                          * command, so we can go back
 679                                          * to normal mode.
 680                                          */
 681                                         kdb_grepping_flag = 0;
 682                                         goto kdb_printit;
 683                                 }
 684                         }
 685                         /* no newline; don't search/write the buffer
 686                            until one is there */
 687                         len = strlen(kdb_buffer);
 688                         next_avail = kdb_buffer + len;
 689                         size_avail = sizeof(kdb_buffer) - len;
 690                         goto kdb_print_out;
 691                 }
 692
 693                 /*
 694                  * The newline is present; print through it or discard
 695                  * it, depending on the results of the search.
 696                  */
 697                 cp++;                /* to byte after the newline */
 698                 replaced_byte = *cp; /* remember what/where it was */
 699                 cphold = cp;
 700                 *cp = '\0';          /* end the string for our search */
 701
 702                 /*
 703                  * We now have a newline at the end of the string
 704                  * Only continue with this output if it contains the
 705                  * search string.
 706                  */
 707                 fnd = kdb_search_string(kdb_buffer, kdb_grep_string);
 708                 if (!fnd) {
 709                         /*
 710                          * At this point the complete line at the start
 711                          * of kdb_buffer can be discarded, as it does
 712                          * not contain what the user is looking for.
 713                          * Shift the buffer left.
 714                          */
 715                         *cphold = replaced_byte;
 716                         strcpy(kdb_buffer, cphold);
 717                         len = strlen(kdb_buffer);
 718                         next_avail = kdb_buffer + len;
 719                         size_avail = sizeof(kdb_buffer) - len;
 720                         goto kdb_print_out;
 721                 }
 722                 if (kdb_grepping_flag >= KDB_GREPPING_FLAG_SEARCH) {
 723                         /*
 724                          * This was a interactive search (using '/' at more
 725                          * prompt) and it has completed. Replace the \0 with
 726                          * its original value to ensure multi-line strings
 727                          * are handled properly, and return to normal mode.
 728                          */
 729                         *cphold = replaced_byte;
 730                         kdb_grepping_flag = 0;
 731                 }
 732                 /*
 733                  * at this point the string is a full line and
 734                  * should be printed, up to the null.
 735                  */
 736         }
 737 kdb_printit:
 738
 739         /*
 740          * Write to all consoles.
 741          */
 742         retlen = strlen(kdb_buffer);
 743         cp = (char *) printk_skip_headers(kdb_buffer);
 744         if (!dbg_kdb_mode && kgdb_connected)
 745                 gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));
 746         else
 747                 kdb_msg_write(cp, retlen - (cp - kdb_buffer));
 748
 749         if (logging) {
 750                 saved_loglevel = console_loglevel;
 751                 console_loglevel = CONSOLE_LOGLEVEL_SILENT;
 752                 if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK)
 753                         printk("%s", kdb_buffer);
 754                 else
 755                         pr_info("%s", kdb_buffer);
 756         }
 757
 758         if (KDB_STATE(PAGER)) {
 759                 /*
 760                  * Check printed string to decide how to bump the
 761                  * kdb_nextline to control when the more prompt should
 762                  * show up.
 763                  */
 764                 int got = 0;
 765                 len = retlen;
 766                 while (len--) {
 767                         if (kdb_buffer[len] == '\n') {
 768                                 kdb_nextline++;
 769                                 got = 0;
 770                         } else if (kdb_buffer[len] == '\r') {
 771                                 got = 0;
 772                         } else {
 773                                 got++;
 774                         }
 775                 }
 776                 kdb_nextline += got / (colcount + 1);
 777         }
 778
 779         /* check for having reached the LINES number of printed lines */
 780         if (kdb_nextline >= linecount) {
 781                 char ch;
 782
 783                 /* Watch out for recursion here.  Any routine that calls
 784                  * kdb_printf will come back through here.  And kdb_read
 785                  * uses kdb_printf to echo on serial consoles ...
 786                  */
 787                 kdb_nextline = 1;       /* In case of recursion */
 788
 789                 /*
 790                  * Pause until cr.
 791                  */
 792                 moreprompt = kdbgetenv("MOREPROMPT");
 793                 if (moreprompt == NULL)
 794                         moreprompt = "more> ";
 795
 796                 kdb_input_flush();
 797                 kdb_msg_write(moreprompt, strlen(moreprompt));
 798
 799                 if (logging)
 800                         printk("%s", moreprompt);
 801
 802                 ch = kdb_getchar();
 803                 kdb_nextline = 1;       /* Really set output line 1 */
 804
 805                 /* empty and reset the buffer: */
 806                 kdb_buffer[0] = '\0';
 807                 next_avail = kdb_buffer;
 808                 size_avail = sizeof(kdb_buffer);
 809                 if ((ch == 'q') || (ch == 'Q')) {
 810                         /* user hit q or Q */
 811                         KDB_FLAG_SET(CMD_INTERRUPT); /* command interrupted */
 812                         KDB_STATE_CLEAR(PAGER);
 813                         /* end of command output; back to normal mode */
 814                         kdb_grepping_flag = 0;
 815                         kdb_printf("\n");
 816                 } else if (ch == ' ') {
 817                         kdb_printf("\r");
 818                         suspend_grep = 1; /* for this recursion */
 819                 } else if (ch == '\n' || ch == '\r') {
 820                         kdb_nextline = linecount - 1;
 821                         kdb_printf("\r");
 822                         suspend_grep = 1; /* for this recursion */
 823                 } else if (ch == '/' && !kdb_grepping_flag) {
 824                         kdb_printf("\r");
 825                         kdb_getstr(kdb_grep_string, KDB_GREP_STRLEN,
 826                                    kdbgetenv("SEARCHPROMPT") ?: "search> ");
 827                         *strchrnul(kdb_grep_string, '\n') = '\0';
 828                         kdb_grepping_flag += KDB_GREPPING_FLAG_SEARCH;
 829                         suspend_grep = 1; /* for this recursion */
 830                 } else if (ch) {
 831                         /* user hit something unexpected */
 832                         suspend_grep = 1; /* for this recursion */
 833                         if (ch != '/')
 834                                 kdb_printf(
 835                                     "\nOnly 'q', 'Q' or '/' are processed at "
 836                                     "more prompt, input ignored\n");
 837                         else
 838                                 kdb_printf("\n'/' cannot be used during | "
 839                                            "grep filtering, input ignored\n");
 840                 } else if (kdb_grepping_flag) {
 841                         /* user hit enter */
 842                         suspend_grep = 1; /* for this recursion */
 843                         kdb_printf("\n");
 844                 }
 845                 kdb_input_flush();
 846         }
 847
 848         /*
 849          * For grep searches, shift the printed string left.
 850          *  replaced_byte contains the character that was overwritten with
 851          *  the terminating null, and cphold points to the null.
 852          * Then adjust the notion of available space in the buffer.
 853          */
 854         if (kdb_grepping_flag && !suspend_grep) {
 855                 *cphold = replaced_byte;
 856                 strcpy(kdb_buffer, cphold);
 857                 len = strlen(kdb_buffer);
 858                 next_avail = kdb_buffer + len;
 859                 size_avail = sizeof(kdb_buffer) - len;
 860         }
 861
 862 kdb_print_out:
 863         suspend_grep = 0; /* end of what may have been a recursive call */
 864         if (logging)
 865                 console_loglevel = saved_loglevel;
 866         /* kdb_printf_cpu locked the code above. */
 867         smp_store_release(&kdb_printf_cpu, old_cpu);
 868         local_irq_restore(flags);
 869         return retlen;
 870 }
 871
 872 int kdb_printf(const char *fmt, ...)
 873 {
 874         va_list ap;
 875         int r;
 876
 877         va_start(ap, fmt);
 878         r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap);
 879         va_end(ap);
 880
 881         return r;
 882 }
 883 EXPORT_SYMBOL_GPL(kdb_printf);