kernel/kgdb.c

   1 /*
   2  * KGDB stub.
   3  *
   4  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
   5  *
   6  * Copyright (C) 2000-2001 VERITAS Software Corporation.
   7  * Copyright (C) 2002-2004 Timesys Corporation
   8  * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
   9  * Copyright (C) 2004 Pavel Machek <pavel@suse.cz>
  10  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
  11  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
  12  * Copyright (C) 2005-2008 Wind River Systems, Inc.
  13  * Copyright (C) 2007 MontaVista Software, Inc.
  14  * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  15  *
  16  * Contributors at various stages not listed above:
  17  *  Jason Wessel ( jason.wessel@windriver.com )
  18  *  George Anzinger <george@mvista.com>
  19  *  Anurekh Saxena (anurekh.saxena@timesys.com)
  20  *  Lake Stevens Instrument Division (Glenn Engel)
  21  *  Jim Kingdon, Cygnus Support.
  22  *
  23  * Original KGDB stub: David Grothe <dave@gcom.com>,
  24  * Tigran Aivazian <tigran@sco.com>
  25  *
  26  * This file is licensed under the terms of the GNU General Public License
  27  * version 2. This program is licensed "as is" without any warranty of any
  28  * kind, whether express or implied.
  29  */
  30 #include <linux/pid_namespace.h>
  31 #include <linux/clocksource.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/console.h>
  35 #include <linux/threads.h>
  36 #include <linux/uaccess.h>
  37 #include <linux/kernel.h>
  38 #include <linux/module.h>
  39 #include <linux/ptrace.h>
  40 #include <linux/reboot.h>
  41 #include <linux/string.h>
  42 #include <linux/delay.h>
  43 #include <linux/sched.h>
  44 #include <linux/sysrq.h>
  45 #include <linux/init.h>
  46 #include <linux/kgdb.h>
  47 #include <linux/pid.h>
  48 #include <linux/smp.h>
  49 #include <linux/mm.h>
  50
  51 #include <asm/cacheflush.h>
  52 #include <asm/byteorder.h>
  53 #include <asm/atomic.h>
  54 #include <asm/system.h>
  55 #include <asm/unaligned.h>
  56
  57 static int kgdb_break_asap;
  58
  59 #define KGDB_MAX_THREAD_QUERY 17
  60 struct kgdb_state {
  61         int                     ex_vector;
  62         int                     signo;
  63         int                     err_code;
  64         int                     cpu;
  65         int                     pass_exception;
  66         unsigned long           thr_query;
  67         unsigned long           threadid;
  68         long                    kgdb_usethreadid;
  69         struct pt_regs          *linux_regs;
  70 };
  71
  72 static struct debuggerinfo_struct {
  73         void                    *debuggerinfo;
  74         struct task_struct      *task;
  75 } kgdb_info[NR_CPUS];
  76
  77 /**
  78  * kgdb_connected - Is a host GDB connected to us?
  79  */
  80 int                             kgdb_connected;
  81 EXPORT_SYMBOL_GPL(kgdb_connected);
  82
  83 /* All the KGDB handlers are installed */
  84 static int                      kgdb_io_module_registered;
  85
  86 /* Guard for recursive entry */
  87 static int                      exception_level;
  88
  89 static struct kgdb_io           *kgdb_io_ops;
  90 static DEFINE_SPINLOCK(kgdb_registration_lock);
  91
  92 /* kgdb console driver is loaded */
  93 static int kgdb_con_registered;
  94 /* determine if kgdb console output should be used */
  95 static int kgdb_use_con;
  96
  97 static int __init opt_kgdb_con(char *str)
  98 {
  99         kgdb_use_con = 1;
 100         return 0;
 101 }
 102
 103 early_param("kgdbcon", opt_kgdb_con);
 104
 105 module_param(kgdb_use_con, int, 0644);
 106
 107 /*
 108  * Holds information about breakpoints in a kernel. These breakpoints are
 109  * added and removed by gdb.
 110  */
 111 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
 112         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
 113 };
 114
 115 /*
 116  * The CPU# of the active CPU, or -1 if none:
 117  */
 118 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 119
 120 /*
 121  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 122  * bootup code (which might not have percpu set up yet):
 123  */
 124 static atomic_t                 passive_cpu_wait[NR_CPUS];
 125 static atomic_t                 cpu_in_kgdb[NR_CPUS];
 126 atomic_t                        kgdb_setting_breakpoint;
 127
 128 struct task_struct              *kgdb_usethread;
 129 struct task_struct              *kgdb_contthread;
 130
 131 int                             kgdb_single_step;
 132
 133 /* Our I/O buffers. */
 134 static char                     remcom_in_buffer[BUFMAX];
 135 static char                     remcom_out_buffer[BUFMAX];
 136
 137 /* Storage for the registers, in GDB format. */
 138 static unsigned long            gdb_regs[(NUMREGBYTES +
 139                                         sizeof(unsigned long) - 1) /
 140                                         sizeof(unsigned long)];
 141
 142 /* to keep track of the CPU which is doing the single stepping*/
 143 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 144
 145 /*
 146  * If you are debugging a problem where roundup (the collection of
 147  * all other CPUs) is a problem [this should be extremely rare],
 148  * then use the nokgdbroundup option to avoid roundup. In that case
 149  * the other CPUs might interfere with your debugging context, so
 150  * use this with care:
 151  */
 152 static int kgdb_do_roundup = 1;
 153
 154 static int __init opt_nokgdbroundup(char *str)
 155 {
 156         kgdb_do_roundup = 0;
 157
 158         return 0;
 159 }
 160
 161 early_param("nokgdbroundup", opt_nokgdbroundup);
 162
 163 /*
 164  * Finally, some KGDB code :-)
 165  */
 166
 167 /*
 168  * Weak aliases for breakpoint management,
 169  * can be overriden by architectures when needed:
 170  */
 171 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 172 {
 173         int err;
 174
 175         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
 176         if (err)
 177                 return err;
 178
 179         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
 180                                   BREAK_INSTR_SIZE);
 181 }
 182
 183 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 184 {
 185         return probe_kernel_write((char *)addr,
 186                                   (char *)bundle, BREAK_INSTR_SIZE);
 187 }
 188
 189 int __weak kgdb_validate_break_address(unsigned long addr)
 190 {
 191         char tmp_variable[BREAK_INSTR_SIZE];
 192         int err;
 193         /* Validate setting the breakpoint and then removing it.  In the
 194          * remove fails, the kernel needs to emit a bad message because we
 195          * are deep trouble not being able to put things back the way we
 196          * found them.
 197          */
 198         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
 199         if (err)
 200                 return err;
 201         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
 202         if (err)
 203                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 204                    "memory destroyed at: %lx", addr);
 205         return err;
 206 }
 207
 208 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 209 {
 210         return instruction_pointer(regs);
 211 }
 212
 213 int __weak kgdb_arch_init(void)
 214 {
 215         return 0;
 216 }
 217
 218 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 219 {
 220         return 0;
 221 }
 222
 223 void __weak
 224 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 225 {
 226         return;
 227 }
 228
 229 /**
 230  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 231  *      @regs: Current &struct pt_regs.
 232  *
 233  *      This function will be called if the particular architecture must
 234  *      disable hardware debugging while it is processing gdb packets or
 235  *      handling exception.
 236  */
 237 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
 238 {
 239 }
 240
 241 /*
 242  * GDB remote protocol parser:
 243  */
 244
 245 static int hex(char ch)
 246 {
 247         if ((ch >= 'a') && (ch <= 'f'))
 248                 return ch - 'a' + 10;
 249         if ((ch >= '0') && (ch <= '9'))
 250                 return ch - '0';
 251         if ((ch >= 'A') && (ch <= 'F'))
 252                 return ch - 'A' + 10;
 253         return -1;
 254 }
 255
 256 /* scan for the sequence $<data>#<checksum> */
 257 static void get_packet(char *buffer)
 258 {
 259         unsigned char checksum;
 260         unsigned char xmitcsum;
 261         int count;
 262         char ch;
 263
 264         do {
 265                 /*
 266                  * Spin and wait around for the start character, ignore all
 267                  * other characters:
 268                  */
 269                 while ((ch = (kgdb_io_ops->read_char())) != '$')
 270                         /* nothing */;
 271
 272                 kgdb_connected = 1;
 273                 checksum = 0;
 274                 xmitcsum = -1;
 275
 276                 count = 0;
 277
 278                 /*
 279                  * now, read until a # or end of buffer is found:
 280                  */
 281                 while (count < (BUFMAX - 1)) {
 282                         ch = kgdb_io_ops->read_char();
 283                         if (ch == '#')
 284                                 break;
 285                         checksum = checksum + ch;
 286                         buffer[count] = ch;
 287                         count = count + 1;
 288                 }
 289                 buffer[count] = 0;
 290
 291                 if (ch == '#') {
 292                         xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
 293                         xmitcsum += hex(kgdb_io_ops->read_char());
 294
 295                         if (checksum != xmitcsum)
 296                                 /* failed checksum */
 297                                 kgdb_io_ops->write_char('-');
 298                         else
 299                                 /* successful transfer */
 300                                 kgdb_io_ops->write_char('+');
 301                         if (kgdb_io_ops->flush)
 302                                 kgdb_io_ops->flush();
 303                 }
 304         } while (checksum != xmitcsum);
 305 }
 306
 307 /*
 308  * Send the packet in buffer.
 309  * Check for gdb connection if asked for.
 310  */
 311 static void put_packet(char *buffer)
 312 {
 313         unsigned char checksum;
 314         int count;
 315         char ch;
 316
 317         /*
 318          * $<packet info>#<checksum>.
 319          */
 320         while (1) {
 321                 kgdb_io_ops->write_char('$');
 322                 checksum = 0;
 323                 count = 0;
 324
 325                 while ((ch = buffer[count])) {
 326                         kgdb_io_ops->write_char(ch);
 327                         checksum += ch;
 328                         count++;
 329                 }
 330
 331                 kgdb_io_ops->write_char('#');
 332                 kgdb_io_ops->write_char(hex_asc_hi(checksum));
 333                 kgdb_io_ops->write_char(hex_asc_lo(checksum));
 334                 if (kgdb_io_ops->flush)
 335                         kgdb_io_ops->flush();
 336
 337                 /* Now see what we get in reply. */
 338                 ch = kgdb_io_ops->read_char();
 339
 340                 if (ch == 3)
 341                         ch = kgdb_io_ops->read_char();
 342
 343                 /* If we get an ACK, we are done. */
 344                 if (ch == '+')
 345                         return;
 346
 347                 /*
 348                  * If we get the start of another packet, this means
 349                  * that GDB is attempting to reconnect.  We will NAK
 350                  * the packet being sent, and stop trying to send this
 351                  * packet.
 352                  */
 353                 if (ch == '$') {
 354                         kgdb_io_ops->write_char('-');
 355                         if (kgdb_io_ops->flush)
 356                                 kgdb_io_ops->flush();
 357                         return;
 358                 }
 359         }
 360 }
 361
 362 /*
 363  * Convert the memory pointed to by mem into hex, placing result in buf.
 364  * Return a pointer to the last char put in buf (null). May return an error.
 365  */
 366 int kgdb_mem2hex(char *mem, char *buf, int count)
 367 {
 368         char *tmp;
 369         int err;
 370
 371         /*
 372          * We use the upper half of buf as an intermediate buffer for the
 373          * raw memory copy.  Hex conversion will work against this one.
 374          */
 375         tmp = buf + count;
 376
 377         err = probe_kernel_read(tmp, mem, count);
 378         if (!err) {
 379                 while (count > 0) {
 380                         buf = pack_hex_byte(buf, *tmp);
 381                         tmp++;
 382                         count--;
 383                 }
 384
 385                 *buf = 0;
 386         }
 387
 388         return err;
 389 }
 390
 391 /*
 392  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
 393  * 0x7d escaped with 0x7d.  Return a pointer to the character after
 394  * the last byte written.
 395  */
 396 static int kgdb_ebin2mem(char *buf, char *mem, int count)
 397 {
 398         int err = 0;
 399         char c;
 400
 401         while (count-- > 0) {
 402                 c = *buf++;
 403                 if (c == 0x7d)
 404                         c = *buf++ ^ 0x20;
 405
 406                 err = probe_kernel_write(mem, &c, 1);
 407                 if (err)
 408                         break;
 409
 410                 mem++;
 411         }
 412
 413         return err;
 414 }
 415
 416 /*
 417  * Convert the hex array pointed to by buf into binary to be placed in mem.
 418  * Return a pointer to the character AFTER the last byte written.
 419  * May return an error.
 420  */
 421 int kgdb_hex2mem(char *buf, char *mem, int count)
 422 {
 423         char *tmp_raw;
 424         char *tmp_hex;
 425
 426         /*
 427          * We use the upper half of buf as an intermediate buffer for the
 428          * raw memory that is converted from hex.
 429          */
 430         tmp_raw = buf + count * 2;
 431
 432         tmp_hex = tmp_raw - 1;
 433         while (tmp_hex >= buf) {
 434                 tmp_raw--;
 435                 *tmp_raw = hex(*tmp_hex--);
 436                 *tmp_raw |= hex(*tmp_hex--) << 4;
 437         }
 438
 439         return probe_kernel_write(mem, tmp_raw, count);
 440 }
 441
 442 /*
 443  * While we find nice hex chars, build a long_val.
 444  * Return number of chars processed.
 445  */
 446 int kgdb_hex2long(char **ptr, unsigned long *long_val)
 447 {
 448         int hex_val;
 449         int num = 0;
 450         int negate = 0;
 451
 452         *long_val = 0;
 453
 454         if (**ptr == '-') {
 455                 negate = 1;
 456                 (*ptr)++;
 457         }
 458         while (**ptr) {
 459                 hex_val = hex(**ptr);
 460                 if (hex_val < 0)
 461                         break;
 462
 463                 *long_val = (*long_val << 4) | hex_val;
 464                 num++;
 465                 (*ptr)++;
 466         }
 467
 468         if (negate)
 469                 *long_val = -*long_val;
 470
 471         return num;
 472 }
 473
 474 /* Write memory due to an 'M' or 'X' packet. */
 475 static int write_mem_msg(int binary)
 476 {
 477         char *ptr = &remcom_in_buffer[1];
 478         unsigned long addr;
 479         unsigned long length;
 480         int err;
 481
 482         if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
 483             kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
 484                 if (binary)
 485                         err = kgdb_ebin2mem(ptr, (char *)addr, length);
 486                 else
 487                         err = kgdb_hex2mem(ptr, (char *)addr, length);
 488                 if (err)
 489                         return err;
 490                 if (CACHE_FLUSH_IS_SAFE)
 491                         flush_icache_range(addr, addr + length);
 492                 return 0;
 493         }
 494
 495         return -EINVAL;
 496 }
 497
 498 static void error_packet(char *pkt, int error)
 499 {
 500         error = -error;
 501         pkt[0] = 'E';
 502         pkt[1] = hex_asc[(error / 10)];
 503         pkt[2] = hex_asc[(error % 10)];
 504         pkt[3] = '\0';
 505 }
 506
 507 /*
 508  * Thread ID accessors. We represent a flat TID space to GDB, where
 509  * the per CPU idle threads (which under Linux all have PID 0) are
 510  * remapped to negative TIDs.
 511  */
 512
 513 #define BUF_THREAD_ID_SIZE      16
 514
 515 static char *pack_threadid(char *pkt, unsigned char *id)
 516 {
 517         char *limit;
 518
 519         limit = pkt + BUF_THREAD_ID_SIZE;
 520         while (pkt < limit)
 521                 pkt = pack_hex_byte(pkt, *id++);
 522
 523         return pkt;
 524 }
 525
 526 static void int_to_threadref(unsigned char *id, int value)
 527 {
 528         unsigned char *scan;
 529         int i = 4;
 530
 531         scan = (unsigned char *)id;
 532         while (i--)
 533                 *scan++ = 0;
 534         put_unaligned_be32(value, scan);
 535 }
 536
 537 static struct task_struct *getthread(struct pt_regs *regs, int tid)
 538 {
 539         /*
 540          * Non-positive TIDs are remapped to the cpu shadow information
 541          */
 542         if (tid == 0 || tid == -1)
 543                 tid = -atomic_read(&kgdb_active) - 2;
 544         if (tid < 0) {
 545                 if (kgdb_info[-tid - 2].task)
 546                         return kgdb_info[-tid - 2].task;
 547                 else
 548                         return idle_task(-tid - 2);
 549         }
 550
 551         /*
 552          * find_task_by_pid_ns() does not take the tasklist lock anymore
 553          * but is nicely RCU locked - hence is a pretty resilient
 554          * thing to use:
 555          */
 556         return find_task_by_pid_ns(tid, &init_pid_ns);
 557 }
 558
 559 /*
 560  * CPU debug state control:
 561  */
 562
 563 #ifdef CONFIG_SMP
 564 static void kgdb_wait(struct pt_regs *regs)
 565 {
 566         unsigned long flags;
 567         int cpu;
 568
 569         local_irq_save(flags);
 570         cpu = raw_smp_processor_id();
 571         kgdb_info[cpu].debuggerinfo = regs;
 572         kgdb_info[cpu].task = current;
 573         /*
 574          * Make sure the above info reaches the primary CPU before
 575          * our cpu_in_kgdb[] flag setting does:
 576          */
 577         smp_wmb();
 578         atomic_set(&cpu_in_kgdb[cpu], 1);
 579
 580         /* Wait till primary CPU is done with debugging */
 581         while (atomic_read(&passive_cpu_wait[cpu]))
 582                 cpu_relax();
 583
 584         kgdb_info[cpu].debuggerinfo = NULL;
 585         kgdb_info[cpu].task = NULL;
 586
 587         /* fix up hardware debug registers on local cpu */
 588         if (arch_kgdb_ops.correct_hw_break)
 589                 arch_kgdb_ops.correct_hw_break();
 590
 591         /* Signal the primary CPU that we are done: */
 592         atomic_set(&cpu_in_kgdb[cpu], 0);
 593         touch_softlockup_watchdog();
 594         clocksource_touch_watchdog();
 595         local_irq_restore(flags);
 596 }
 597 #endif
 598
 599 /*
 600  * Some architectures need cache flushes when we set/clear a
 601  * breakpoint:
 602  */
 603 static void kgdb_flush_swbreak_addr(unsigned long addr)
 604 {
 605         if (!CACHE_FLUSH_IS_SAFE)
 606                 return;
 607
 608         if (current->mm && current->mm->mmap_cache) {
 609                 flush_cache_range(current->mm->mmap_cache,
 610                                   addr, addr + BREAK_INSTR_SIZE);
 611         }
 612         /* Force flush instruction cache if it was outside the mm */
 613         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 614 }
 615
 616 /*
 617  * SW breakpoint management:
 618  */
 619 static int kgdb_activate_sw_breakpoints(void)
 620 {
 621         unsigned long addr;
 622         int error = 0;
 623         int i;
 624
 625         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 626                 if (kgdb_break[i].state != BP_SET)
 627                         continue;
 628
 629                 addr = kgdb_break[i].bpt_addr;
 630                 error = kgdb_arch_set_breakpoint(addr,
 631                                 kgdb_break[i].saved_instr);
 632                 if (error)
 633                         return error;
 634
 635                 kgdb_flush_swbreak_addr(addr);
 636                 kgdb_break[i].state = BP_ACTIVE;
 637         }
 638         return 0;
 639 }
 640
 641 static int kgdb_set_sw_break(unsigned long addr)
 642 {
 643         int err = kgdb_validate_break_address(addr);
 644         int breakno = -1;
 645         int i;
 646
 647         if (err)
 648                 return err;
 649
 650         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 651                 if ((kgdb_break[i].state == BP_SET) &&
 652                                         (kgdb_break[i].bpt_addr == addr))
 653                         return -EEXIST;
 654         }
 655         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 656                 if (kgdb_break[i].state == BP_REMOVED &&
 657                                         kgdb_break[i].bpt_addr == addr) {
 658                         breakno = i;
 659                         break;
 660                 }
 661         }
 662
 663         if (breakno == -1) {
 664                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 665                         if (kgdb_break[i].state == BP_UNDEFINED) {
 666                                 breakno = i;
 667                                 break;
 668                         }
 669                 }
 670         }
 671
 672         if (breakno == -1)
 673                 return -E2BIG;
 674
 675         kgdb_break[breakno].state = BP_SET;
 676         kgdb_break[breakno].type = BP_BREAKPOINT;
 677         kgdb_break[breakno].bpt_addr = addr;
 678
 679         return 0;
 680 }
 681
 682 static int kgdb_deactivate_sw_breakpoints(void)
 683 {
 684         unsigned long addr;
 685         int error = 0;
 686         int i;
 687
 688         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 689                 if (kgdb_break[i].state != BP_ACTIVE)
 690                         continue;
 691                 addr = kgdb_break[i].bpt_addr;
 692                 error = kgdb_arch_remove_breakpoint(addr,
 693                                         kgdb_break[i].saved_instr);
 694                 if (error)
 695                         return error;
 696
 697                 kgdb_flush_swbreak_addr(addr);
 698                 kgdb_break[i].state = BP_SET;
 699         }
 700         return 0;
 701 }
 702
 703 static int kgdb_remove_sw_break(unsigned long addr)
 704 {
 705         int i;
 706
 707         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 708                 if ((kgdb_break[i].state == BP_SET) &&
 709                                 (kgdb_break[i].bpt_addr == addr)) {
 710                         kgdb_break[i].state = BP_REMOVED;
 711                         return 0;
 712                 }
 713         }
 714         return -ENOENT;
 715 }
 716
 717 int kgdb_isremovedbreak(unsigned long addr)
 718 {
 719         int i;
 720
 721         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 722                 if ((kgdb_break[i].state == BP_REMOVED) &&
 723                                         (kgdb_break[i].bpt_addr == addr))
 724                         return 1;
 725         }
 726         return 0;
 727 }
 728
 729 static int remove_all_break(void)
 730 {
 731         unsigned long addr;
 732         int error;
 733         int i;
 734
 735         /* Clear memory breakpoints. */
 736         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 737                 if (kgdb_break[i].state != BP_ACTIVE)
 738                         goto setundefined;
 739                 addr = kgdb_break[i].bpt_addr;
 740                 error = kgdb_arch_remove_breakpoint(addr,
 741                                 kgdb_break[i].saved_instr);
 742                 if (error)
 743                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 744                            addr);
 745 setundefined:
 746                 kgdb_break[i].state = BP_UNDEFINED;
 747         }
 748
 749         /* Clear hardware breakpoints. */
 750         if (arch_kgdb_ops.remove_all_hw_break)
 751                 arch_kgdb_ops.remove_all_hw_break();
 752
 753         return 0;
 754 }
 755
 756 /*
 757  * Remap normal tasks to their real PID,
 758  * CPU shadow threads are mapped to -CPU - 2
 759  */
 760 static inline int shadow_pid(int realpid)
 761 {
 762         if (realpid)
 763                 return realpid;
 764
 765         return -raw_smp_processor_id() - 2;
 766 }
 767
 768 static char gdbmsgbuf[BUFMAX + 1];
 769
 770 static void kgdb_msg_write(const char *s, int len)
 771 {
 772         char *bufptr;
 773         int wcount;
 774         int i;
 775
 776         /* 'O'utput */
 777         gdbmsgbuf[0] = 'O';
 778
 779         /* Fill and send buffers... */
 780         while (len > 0) {
 781                 bufptr = gdbmsgbuf + 1;
 782
 783                 /* Calculate how many this time */
 784                 if ((len << 1) > (BUFMAX - 2))
 785                         wcount = (BUFMAX - 2) >> 1;
 786                 else
 787                         wcount = len;
 788
 789                 /* Pack in hex chars */
 790                 for (i = 0; i < wcount; i++)
 791                         bufptr = pack_hex_byte(bufptr, s[i]);
 792                 *bufptr = '\0';
 793
 794                 /* Move up */
 795                 s += wcount;
 796                 len -= wcount;
 797
 798                 /* Write packet */
 799                 put_packet(gdbmsgbuf);
 800         }
 801 }
 802
 803 /*
 804  * Return true if there is a valid kgdb I/O module.  Also if no
 805  * debugger is attached a message can be printed to the console about
 806  * waiting for the debugger to attach.
 807  *
 808  * The print_wait argument is only to be true when called from inside
 809  * the core kgdb_handle_exception, because it will wait for the
 810  * debugger to attach.
 811  */
 812 static int kgdb_io_ready(int print_wait)
 813 {
 814         if (!kgdb_io_ops)
 815                 return 0;
 816         if (kgdb_connected)
 817                 return 1;
 818         if (atomic_read(&kgdb_setting_breakpoint))
 819                 return 1;
 820         if (print_wait)
 821                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 822         return 1;
 823 }
 824
 825 /*
 826  * All the functions that start with gdb_cmd are the various
 827  * operations to implement the handlers for the gdbserial protocol
 828  * where KGDB is communicating with an external debugger
 829  */
 830
 831 /* Handle the '?' status packets */
 832 static void gdb_cmd_status(struct kgdb_state *ks)
 833 {
 834         /*
 835          * We know that this packet is only sent
 836          * during initial connect.  So to be safe,
 837          * we clear out our breakpoints now in case
 838          * GDB is reconnecting.
 839          */
 840         remove_all_break();
 841
 842         remcom_out_buffer[0] = 'S';
 843         pack_hex_byte(&remcom_out_buffer[1], ks->signo);
 844 }
 845
 846 /* Handle the 'g' get registers request */
 847 static void gdb_cmd_getregs(struct kgdb_state *ks)
 848 {
 849         struct task_struct *thread;
 850         void *local_debuggerinfo;
 851         int i;
 852
 853         thread = kgdb_usethread;
 854         if (!thread) {
 855                 thread = kgdb_info[ks->cpu].task;
 856                 local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
 857         } else {
 858                 local_debuggerinfo = NULL;
 859                 for_each_online_cpu(i) {
 860                         /*
 861                          * Try to find the task on some other
 862                          * or possibly this node if we do not
 863                          * find the matching task then we try
 864                          * to approximate the results.
 865                          */
 866                         if (thread == kgdb_info[i].task)
 867                                 local_debuggerinfo = kgdb_info[i].debuggerinfo;
 868                 }
 869         }
 870
 871         /*
 872          * All threads that don't have debuggerinfo should be
 873          * in __schedule() sleeping, since all other CPUs
 874          * are in kgdb_wait, and thus have debuggerinfo.
 875          */
 876         if (local_debuggerinfo) {
 877                 pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
 878         } else {
 879                 /*
 880                  * Pull stuff saved during switch_to; nothing
 881                  * else is accessible (or even particularly
 882                  * relevant).
 883                  *
 884                  * This should be enough for a stack trace.
 885                  */
 886                 sleeping_thread_to_gdb_regs(gdb_regs, thread);
 887         }
 888         kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
 889 }
 890
 891 /* Handle the 'G' set registers request */
 892 static void gdb_cmd_setregs(struct kgdb_state *ks)
 893 {
 894         kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
 895
 896         if (kgdb_usethread && kgdb_usethread != current) {
 897                 error_packet(remcom_out_buffer, -EINVAL);
 898         } else {
 899                 gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
 900                 strcpy(remcom_out_buffer, "OK");
 901         }
 902 }
 903
 904 /* Handle the 'm' memory read bytes */
 905 static void gdb_cmd_memread(struct kgdb_state *ks)
 906 {
 907         char *ptr = &remcom_in_buffer[1];
 908         unsigned long length;
 909         unsigned long addr;
 910         int err;
 911
 912         if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
 913                                         kgdb_hex2long(&ptr, &length) > 0) {
 914                 err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
 915                 if (err)
 916                         error_packet(remcom_out_buffer, err);
 917         } else {
 918                 error_packet(remcom_out_buffer, -EINVAL);
 919         }
 920 }
 921
 922 /* Handle the 'M' memory write bytes */
 923 static void gdb_cmd_memwrite(struct kgdb_state *ks)
 924 {
 925         int err = write_mem_msg(0);
 926
 927         if (err)
 928                 error_packet(remcom_out_buffer, err);
 929         else
 930                 strcpy(remcom_out_buffer, "OK");
 931 }
 932
 933 /* Handle the 'X' memory binary write bytes */
 934 static void gdb_cmd_binwrite(struct kgdb_state *ks)
 935 {
 936         int err = write_mem_msg(1);
 937
 938         if (err)
 939                 error_packet(remcom_out_buffer, err);
 940         else
 941                 strcpy(remcom_out_buffer, "OK");
 942 }
 943
 944 /* Handle the 'D' or 'k', detach or kill packets */
 945 static void gdb_cmd_detachkill(struct kgdb_state *ks)
 946 {
 947         int error;
 948
 949         /* The detach case */
 950         if (remcom_in_buffer[0] == 'D') {
 951                 error = remove_all_break();
 952                 if (error < 0) {
 953                         error_packet(remcom_out_buffer, error);
 954                 } else {
 955                         strcpy(remcom_out_buffer, "OK");
 956                         kgdb_connected = 0;
 957                 }
 958                 put_packet(remcom_out_buffer);
 959         } else {
 960                 /*
 961                  * Assume the kill case, with no exit code checking,
 962                  * trying to force detach the debugger:
 963                  */
 964                 remove_all_break();
 965                 kgdb_connected = 0;
 966         }
 967 }
 968
 969 /* Handle the 'R' reboot packets */
 970 static int gdb_cmd_reboot(struct kgdb_state *ks)
 971 {
 972         /* For now, only honor R0 */
 973         if (strcmp(remcom_in_buffer, "R0") == 0) {
 974                 printk(KERN_CRIT "Executing emergency reboot\n");
 975                 strcpy(remcom_out_buffer, "OK");
 976                 put_packet(remcom_out_buffer);
 977
 978                 /*
 979                  * Execution should not return from
 980                  * machine_emergency_restart()
 981                  */
 982                 machine_emergency_restart();
 983                 kgdb_connected = 0;
 984
 985                 return 1;
 986         }
 987         return 0;
 988 }
 989
 990 /* Handle the 'q' query packets */
 991 static void gdb_cmd_query(struct kgdb_state *ks)
 992 {
 993         struct task_struct *g;
 994         struct task_struct *p;
 995         unsigned char thref[8];
 996         char *ptr;
 997         int i;
 998         int cpu;
 999         int finished = 0;
1000
1001         switch (remcom_in_buffer[1]) {
1002         case 's':
1003         case 'f':
1004                 if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10))
1005                         break;
1006
1007                 i = 0;
1008                 remcom_out_buffer[0] = 'm';
1009                 ptr = remcom_out_buffer + 1;
1010                 if (remcom_in_buffer[1] == 'f') {
1011                         /* Each cpu is a shadow thread */
1012                         for_each_online_cpu(cpu) {
1013                                 ks->thr_query = 0;
1014                                 int_to_threadref(thref, -cpu - 2);
1015                                 pack_threadid(ptr, thref);
1016                                 ptr += BUF_THREAD_ID_SIZE;
1017                                 *(ptr++) = ',';
1018                                 i++;
1019                         }
1020                 }
1021
1022                 do_each_thread(g, p) {
1023                         if (i >= ks->thr_query && !finished) {
1024                                 int_to_threadref(thref, p->pid);
1025                                 pack_threadid(ptr, thref);
1026                                 ptr += BUF_THREAD_ID_SIZE;
1027                                 *(ptr++) = ',';
1028                                 ks->thr_query++;
1029                                 if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
1030                                         finished = 1;
1031                         }
1032                         i++;
1033                 } while_each_thread(g, p);
1034
1035                 *(--ptr) = '\0';
1036                 break;
1037
1038         case 'C':
1039                 /* Current thread id */
1040                 strcpy(remcom_out_buffer, "QC");
1041                 ks->threadid = shadow_pid(current->pid);
1042                 int_to_threadref(thref, ks->threadid);
1043                 pack_threadid(remcom_out_buffer + 2, thref);
1044                 break;
1045         case 'T':
1046                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16))
1047                         break;
1048
1049                 ks->threadid = 0;
1050                 ptr = remcom_in_buffer + 17;
1051                 kgdb_hex2long(&ptr, &ks->threadid);
1052                 if (!getthread(ks->linux_regs, ks->threadid)) {
1053                         error_packet(remcom_out_buffer, -EINVAL);
1054                         break;
1055                 }
1056                 if ((int)ks->threadid > 0) {
1057                         kgdb_mem2hex(getthread(ks->linux_regs,
1058                                         ks->threadid)->comm,
1059                                         remcom_out_buffer, 16);
1060                 } else {
1061                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
1062
1063                         sprintf(tmpstr, "shadowCPU%d",
1064                                         (int)(-ks->threadid - 2));
1065                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
1066                 }
1067                 break;
1068         }
1069 }
1070
1071 /* Handle the 'H' task query packets */
1072 static void gdb_cmd_task(struct kgdb_state *ks)
1073 {
1074         struct task_struct *thread;
1075         char *ptr;
1076
1077         switch (remcom_in_buffer[1]) {
1078         case 'g':
1079                 ptr = &remcom_in_buffer[2];
1080                 kgdb_hex2long(&ptr, &ks->threadid);
1081                 thread = getthread(ks->linux_regs, ks->threadid);
1082                 if (!thread && ks->threadid > 0) {
1083                         error_packet(remcom_out_buffer, -EINVAL);
1084                         break;
1085                 }
1086                 kgdb_usethread = thread;
1087                 ks->kgdb_usethreadid = ks->threadid;
1088                 strcpy(remcom_out_buffer, "OK");
1089                 break;
1090         case 'c':
1091                 ptr = &remcom_in_buffer[2];
1092                 kgdb_hex2long(&ptr, &ks->threadid);
1093                 if (!ks->threadid) {
1094                         kgdb_contthread = NULL;
1095                 } else {
1096                         thread = getthread(ks->linux_regs, ks->threadid);
1097                         if (!thread && ks->threadid > 0) {
1098                                 error_packet(remcom_out_buffer, -EINVAL);
1099                                 break;
1100                         }
1101                         kgdb_contthread = thread;
1102                 }
1103                 strcpy(remcom_out_buffer, "OK");
1104                 break;
1105         }
1106 }
1107
1108 /* Handle the 'T' thread query packets */
1109 static void gdb_cmd_thread(struct kgdb_state *ks)
1110 {
1111         char *ptr = &remcom_in_buffer[1];
1112         struct task_struct *thread;
1113
1114         kgdb_hex2long(&ptr, &ks->threadid);
1115         thread = getthread(ks->linux_regs, ks->threadid);
1116         if (thread)
1117                 strcpy(remcom_out_buffer, "OK");
1118         else
1119                 error_packet(remcom_out_buffer, -EINVAL);
1120 }
1121
1122 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
1123 static void gdb_cmd_break(struct kgdb_state *ks)
1124 {
1125         /*
1126          * Since GDB-5.3, it's been drafted that '0' is a software
1127          * breakpoint, '1' is a hardware breakpoint, so let's do that.
1128          */
1129         char *bpt_type = &remcom_in_buffer[1];
1130         char *ptr = &remcom_in_buffer[2];
1131         unsigned long addr;
1132         unsigned long length;
1133         int error = 0;
1134
1135         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
1136                 /* Unsupported */
1137                 if (*bpt_type > '4')
1138                         return;
1139         } else {
1140                 if (*bpt_type != '0' && *bpt_type != '1')
1141                         /* Unsupported. */
1142                         return;
1143         }
1144
1145         /*
1146          * Test if this is a hardware breakpoint, and
1147          * if we support it:
1148          */
1149         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
1150                 /* Unsupported. */
1151                 return;
1152
1153         if (*(ptr++) != ',') {
1154                 error_packet(remcom_out_buffer, -EINVAL);
1155                 return;
1156         }
1157         if (!kgdb_hex2long(&ptr, &addr)) {
1158                 error_packet(remcom_out_buffer, -EINVAL);
1159                 return;
1160         }
1161         if (*(ptr++) != ',' ||
1162                 !kgdb_hex2long(&ptr, &length)) {
1163                 error_packet(remcom_out_buffer, -EINVAL);
1164                 return;
1165         }
1166
1167         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
1168                 error = kgdb_set_sw_break(addr);
1169         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
1170                 error = kgdb_remove_sw_break(addr);
1171         else if (remcom_in_buffer[0] == 'Z')
1172                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
1173                         (int)length, *bpt_type - '0');
1174         else if (remcom_in_buffer[0] == 'z')
1175                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
1176                         (int) length, *bpt_type - '0');
1177
1178         if (error == 0)
1179                 strcpy(remcom_out_buffer, "OK");
1180         else
1181                 error_packet(remcom_out_buffer, error);
1182 }
1183
1184 /* Handle the 'C' signal / exception passing packets */
1185 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
1186 {
1187         /* C09 == pass exception
1188          * C15 == detach kgdb, pass exception
1189          */
1190         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
1191
1192                 ks->pass_exception = 1;
1193                 remcom_in_buffer[0] = 'c';
1194
1195         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
1196
1197                 ks->pass_exception = 1;
1198                 remcom_in_buffer[0] = 'D';
1199                 remove_all_break();
1200                 kgdb_connected = 0;
1201                 return 1;
1202
1203         } else {
1204                 error_packet(remcom_out_buffer, -EINVAL);
1205                 return 0;
1206         }
1207
1208         /* Indicate fall through */
1209         return -1;
1210 }
1211
1212 /*
1213  * This function performs all gdbserial command procesing
1214  */
1215 static int gdb_serial_stub(struct kgdb_state *ks)
1216 {
1217         int error = 0;
1218         int tmp;
1219
1220         /* Clear the out buffer. */
1221         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1222
1223         if (kgdb_connected) {
1224                 unsigned char thref[8];
1225                 char *ptr;
1226
1227                 /* Reply to host that an exception has occurred */
1228                 ptr = remcom_out_buffer;
1229                 *ptr++ = 'T';
1230                 ptr = pack_hex_byte(ptr, ks->signo);
1231                 ptr += strlen(strcpy(ptr, "thread:"));
1232                 int_to_threadref(thref, shadow_pid(current->pid));
1233                 ptr = pack_threadid(ptr, thref);
1234                 *ptr++ = ';';
1235                 put_packet(remcom_out_buffer);
1236         }
1237
1238         kgdb_usethread = kgdb_info[ks->cpu].task;
1239         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
1240         ks->pass_exception = 0;
1241
1242         while (1) {
1243                 error = 0;
1244
1245                 /* Clear the out buffer. */
1246                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1247
1248                 get_packet(remcom_in_buffer);
1249
1250                 switch (remcom_in_buffer[0]) {
1251                 case '?': /* gdbserial status */
1252                         gdb_cmd_status(ks);
1253                         break;
1254                 case 'g': /* return the value of the CPU registers */
1255                         gdb_cmd_getregs(ks);
1256                         break;
1257                 case 'G': /* set the value of the CPU registers - return OK */
1258                         gdb_cmd_setregs(ks);
1259                         break;
1260                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1261                         gdb_cmd_memread(ks);
1262                         break;
1263                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1264                         gdb_cmd_memwrite(ks);
1265                         break;
1266                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1267                         gdb_cmd_binwrite(ks);
1268                         break;
1269                         /* kill or detach. KGDB should treat this like a
1270                          * continue.
1271                          */
1272                 case 'D': /* Debugger detach */
1273                 case 'k': /* Debugger detach via kill */
1274                         gdb_cmd_detachkill(ks);
1275                         goto default_handle;
1276                 case 'R': /* Reboot */
1277                         if (gdb_cmd_reboot(ks))
1278                                 goto default_handle;
1279                         break;
1280                 case 'q': /* query command */
1281                         gdb_cmd_query(ks);
1282                         break;
1283                 case 'H': /* task related */
1284                         gdb_cmd_task(ks);
1285                         break;
1286                 case 'T': /* Query thread status */
1287                         gdb_cmd_thread(ks);
1288                         break;
1289                 case 'z': /* Break point remove */
1290                 case 'Z': /* Break point set */
1291                         gdb_cmd_break(ks);
1292                         break;
1293                 case 'C': /* Exception passing */
1294                         tmp = gdb_cmd_exception_pass(ks);
1295                         if (tmp > 0)
1296                                 goto default_handle;
1297                         if (tmp == 0)
1298                                 break;
1299                         /* Fall through on tmp < 0 */
1300                 case 'c': /* Continue packet */
1301                 case 's': /* Single step packet */
1302                         if (kgdb_contthread && kgdb_contthread != current) {
1303                                 /* Can't switch threads in kgdb */
1304                                 error_packet(remcom_out_buffer, -EINVAL);
1305                                 break;
1306                         }
1307                         kgdb_activate_sw_breakpoints();
1308                         /* Fall through to default processing */
1309                 default:
1310 default_handle:
1311                         error = kgdb_arch_handle_exception(ks->ex_vector,
1312                                                 ks->signo,
1313                                                 ks->err_code,
1314                                                 remcom_in_buffer,
1315                                                 remcom_out_buffer,
1316                                                 ks->linux_regs);
1317                         /*
1318                          * Leave cmd processing on error, detach,
1319                          * kill, continue, or single step.
1320                          */
1321                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1322                             remcom_in_buffer[0] == 'k') {
1323                                 error = 0;
1324                                 goto kgdb_exit;
1325                         }
1326
1327                 }
1328
1329                 /* reply to the request */
1330                 put_packet(remcom_out_buffer);
1331         }
1332
1333 kgdb_exit:
1334         if (ks->pass_exception)
1335                 error = 1;
1336         return error;
1337 }
1338
1339 static int kgdb_reenter_check(struct kgdb_state *ks)
1340 {
1341         unsigned long addr;
1342
1343         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
1344                 return 0;
1345
1346         /* Panic on recursive debugger calls: */
1347         exception_level++;
1348         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
1349         kgdb_deactivate_sw_breakpoints();
1350
1351         /*
1352          * If the break point removed ok at the place exception
1353          * occurred, try to recover and print a warning to the end
1354          * user because the user planted a breakpoint in a place that
1355          * KGDB needs in order to function.
1356          */
1357         if (kgdb_remove_sw_break(addr) == 0) {
1358                 exception_level = 0;
1359                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1360                 kgdb_activate_sw_breakpoints();
1361                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
1362                         addr);
1363                 WARN_ON_ONCE(1);
1364
1365                 return 1;
1366         }
1367         remove_all_break();
1368         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1369
1370         if (exception_level > 1) {
1371                 dump_stack();
1372                 panic("Recursive entry to debugger");
1373         }
1374
1375         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
1376         dump_stack();
1377         panic("Recursive entry to debugger");
1378
1379         return 1;
1380 }
1381
1382 /*
1383  * kgdb_handle_exception() - main entry point from a kernel exception
1384  *
1385  * Locking hierarchy:
1386  *      interface locks, if any (begin_session)
1387  *      kgdb lock (kgdb_active)
1388  */
1389 int
1390 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
1391 {
1392         struct kgdb_state kgdb_var;
1393         struct kgdb_state *ks = &kgdb_var;
1394         unsigned long flags;
1395         int error = 0;
1396         int i, cpu;
1397
1398         ks->cpu                 = raw_smp_processor_id();
1399         ks->ex_vector           = evector;
1400         ks->signo               = signo;
1401         ks->ex_vector           = evector;
1402         ks->err_code            = ecode;
1403         ks->kgdb_usethreadid    = 0;
1404         ks->linux_regs          = regs;
1405
1406         if (kgdb_reenter_check(ks))
1407                 return 0; /* Ouch, double exception ! */
1408
1409 acquirelock:
1410         /*
1411          * Interrupts will be restored by the 'trap return' code, except when
1412          * single stepping.
1413          */
1414         local_irq_save(flags);
1415
1416         cpu = raw_smp_processor_id();
1417
1418         /*
1419          * Acquire the kgdb_active lock:
1420          */
1421         while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
1422                 cpu_relax();
1423
1424         /*
1425          * Do not start the debugger connection on this CPU if the last
1426          * instance of the exception handler wanted to come into the
1427          * debugger on a different CPU via a single step
1428          */
1429         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
1430             atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
1431
1432                 atomic_set(&kgdb_active, -1);
1433                 touch_softlockup_watchdog();
1434                 clocksource_touch_watchdog();
1435                 local_irq_restore(flags);
1436
1437                 goto acquirelock;
1438         }
1439
1440         if (!kgdb_io_ready(1)) {
1441                 error = 1;
1442                 goto kgdb_restore; /* No I/O connection, so resume the system */
1443         }
1444
1445         /*
1446          * Don't enter if we have hit a removed breakpoint.
1447          */
1448         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
1449                 goto kgdb_restore;
1450
1451         /* Call the I/O driver's pre_exception routine */
1452         if (kgdb_io_ops->pre_exception)
1453                 kgdb_io_ops->pre_exception();
1454
1455         kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
1456         kgdb_info[ks->cpu].task = current;
1457
1458         kgdb_disable_hw_debug(ks->linux_regs);
1459
1460         /*
1461          * Get the passive CPU lock which will hold all the non-primary
1462          * CPU in a spin state while the debugger is active
1463          */
1464         if (!kgdb_single_step) {
1465                 for (i = 0; i < NR_CPUS; i++)
1466                         atomic_set(&passive_cpu_wait[i], 1);
1467         }
1468
1469         /*
1470          * spin_lock code is good enough as a barrier so we don't
1471          * need one here:
1472          */
1473         atomic_set(&cpu_in_kgdb[ks->cpu], 1);
1474
1475 #ifdef CONFIG_SMP
1476         /* Signal the other CPUs to enter kgdb_wait() */
1477         if ((!kgdb_single_step) && kgdb_do_roundup)
1478                 kgdb_roundup_cpus(flags);
1479 #endif
1480
1481         /*
1482          * Wait for the other CPUs to be notified and be waiting for us:
1483          */
1484         for_each_online_cpu(i) {
1485                 while (!atomic_read(&cpu_in_kgdb[i]))
1486                         cpu_relax();
1487         }
1488
1489         /*
1490          * At this point the primary processor is completely
1491          * in the debugger and all secondary CPUs are quiescent
1492          */
1493         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
1494         kgdb_deactivate_sw_breakpoints();
1495         kgdb_single_step = 0;
1496         kgdb_contthread = current;
1497         exception_level = 0;
1498
1499         /* Talk to debugger with gdbserial protocol */
1500         error = gdb_serial_stub(ks);
1501
1502         /* Call the I/O driver's post_exception routine */
1503         if (kgdb_io_ops->post_exception)
1504                 kgdb_io_ops->post_exception();
1505
1506         kgdb_info[ks->cpu].debuggerinfo = NULL;
1507         kgdb_info[ks->cpu].task = NULL;
1508         atomic_set(&cpu_in_kgdb[ks->cpu], 0);
1509
1510         if (!kgdb_single_step) {
1511                 for (i = NR_CPUS-1; i >= 0; i--)
1512                         atomic_set(&passive_cpu_wait[i], 0);
1513                 /*
1514                  * Wait till all the CPUs have quit
1515                  * from the debugger.
1516                  */
1517                 for_each_online_cpu(i) {
1518                         while (atomic_read(&cpu_in_kgdb[i]))
1519                                 cpu_relax();
1520                 }
1521         }
1522
1523 kgdb_restore:
1524         /* Free kgdb_active */
1525         atomic_set(&kgdb_active, -1);
1526         touch_softlockup_watchdog();
1527         clocksource_touch_watchdog();
1528         local_irq_restore(flags);
1529
1530         return error;
1531 }
1532
1533 int kgdb_nmicallback(int cpu, void *regs)
1534 {
1535 #ifdef CONFIG_SMP
1536         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
1537                         atomic_read(&kgdb_active) != cpu &&
1538                         atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
1539                 kgdb_wait((struct pt_regs *)regs);
1540                 return 0;
1541         }
1542 #endif
1543         return 1;
1544 }
1545
1546 static void kgdb_console_write(struct console *co, const char *s,
1547    unsigned count)
1548 {
1549         unsigned long flags;
1550
1551         /* If we're debugging, or KGDB has not connected, don't try
1552          * and print. */
1553         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
1554                 return;
1555
1556         local_irq_save(flags);
1557         kgdb_msg_write(s, count);
1558         local_irq_restore(flags);
1559 }
1560
1561 static struct console kgdbcons = {
1562         .name           = "kgdb",
1563         .write          = kgdb_console_write,
1564         .flags          = CON_PRINTBUFFER | CON_ENABLED,
1565         .index          = -1,
1566 };
1567
1568 #ifdef CONFIG_MAGIC_SYSRQ
1569 static void sysrq_handle_gdb(int key, struct tty_struct *tty)
1570 {
1571         if (!kgdb_io_ops) {
1572                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
1573                 return;
1574         }
1575         if (!kgdb_connected)
1576                 printk(KERN_CRIT "Entering KGDB\n");
1577
1578         kgdb_breakpoint();
1579 }
1580
1581 static struct sysrq_key_op sysrq_gdb_op = {
1582         .handler        = sysrq_handle_gdb,
1583         .help_msg       = "debug(G)",
1584         .action_msg     = "DEBUG",
1585 };
1586 #endif
1587
1588 static void kgdb_register_callbacks(void)
1589 {
1590         if (!kgdb_io_module_registered) {
1591                 kgdb_io_module_registered = 1;
1592                 kgdb_arch_init();
1593 #ifdef CONFIG_MAGIC_SYSRQ
1594                 register_sysrq_key('g', &sysrq_gdb_op);
1595 #endif
1596                 if (kgdb_use_con && !kgdb_con_registered) {
1597                         register_console(&kgdbcons);
1598                         kgdb_con_registered = 1;
1599                 }
1600         }
1601 }
1602
1603 static void kgdb_unregister_callbacks(void)
1604 {
1605         /*
1606          * When this routine is called KGDB should unregister from the
1607          * panic handler and clean up, making sure it is not handling any
1608          * break exceptions at the time.
1609          */
1610         if (kgdb_io_module_registered) {
1611                 kgdb_io_module_registered = 0;
1612                 kgdb_arch_exit();
1613 #ifdef CONFIG_MAGIC_SYSRQ
1614                 unregister_sysrq_key('g', &sysrq_gdb_op);
1615 #endif
1616                 if (kgdb_con_registered) {
1617                         unregister_console(&kgdbcons);
1618                         kgdb_con_registered = 0;
1619                 }
1620         }
1621 }
1622
1623 static void kgdb_initial_breakpoint(void)
1624 {
1625         kgdb_break_asap = 0;
1626
1627         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
1628         kgdb_breakpoint();
1629 }
1630
1631 /**
1632  *      kgdb_register_io_module - register KGDB IO module
1633  *      @new_kgdb_io_ops: the io ops vector
1634  *
1635  *      Register it with the KGDB core.
1636  */
1637 int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
1638 {
1639         int err;
1640
1641         spin_lock(&kgdb_registration_lock);
1642
1643         if (kgdb_io_ops) {
1644                 spin_unlock(&kgdb_registration_lock);
1645
1646                 printk(KERN_ERR "kgdb: Another I/O driver is already "
1647                                 "registered with KGDB.\n");
1648                 return -EBUSY;
1649         }
1650
1651         if (new_kgdb_io_ops->init) {
1652                 err = new_kgdb_io_ops->init();
1653                 if (err) {
1654                         spin_unlock(&kgdb_registration_lock);
1655                         return err;
1656                 }
1657         }
1658
1659         kgdb_io_ops = new_kgdb_io_ops;
1660
1661         spin_unlock(&kgdb_registration_lock);
1662
1663         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
1664                new_kgdb_io_ops->name);
1665
1666         /* Arm KGDB now. */
1667         kgdb_register_callbacks();
1668
1669         if (kgdb_break_asap)
1670                 kgdb_initial_breakpoint();
1671
1672         return 0;
1673 }
1674 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1675
1676 /**
1677  *      kkgdb_unregister_io_module - unregister KGDB IO module
1678  *      @old_kgdb_io_ops: the io ops vector
1679  *
1680  *      Unregister it with the KGDB core.
1681  */
1682 void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
1683 {
1684         BUG_ON(kgdb_connected);
1685
1686         /*
1687          * KGDB is no longer able to communicate out, so
1688          * unregister our callbacks and reset state.
1689          */
1690         kgdb_unregister_callbacks();
1691
1692         spin_lock(&kgdb_registration_lock);
1693
1694         WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
1695         kgdb_io_ops = NULL;
1696
1697         spin_unlock(&kgdb_registration_lock);
1698
1699         printk(KERN_INFO
1700                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
1701                 old_kgdb_io_ops->name);
1702 }
1703 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1704
1705 /**
1706  * kgdb_breakpoint - generate breakpoint exception
1707  *
1708  * This function will generate a breakpoint exception.  It is used at the
1709  * beginning of a program to sync up with a debugger and can be used
1710  * otherwise as a quick means to stop program execution and "break" into
1711  * the debugger.
1712  */
1713 void kgdb_breakpoint(void)
1714 {
1715         atomic_set(&kgdb_setting_breakpoint, 1);
1716         wmb(); /* Sync point before breakpoint */
1717         arch_kgdb_breakpoint();
1718         wmb(); /* Sync point after breakpoint */
1719         atomic_set(&kgdb_setting_breakpoint, 0);
1720 }
1721 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1722
1723 static int __init opt_kgdb_wait(char *str)
1724 {
1725         kgdb_break_asap = 1;
1726
1727         if (kgdb_io_module_registered)
1728                 kgdb_initial_breakpoint();
1729
1730         return 0;
1731 }
1732
1733 early_param("kgdbwait", opt_kgdb_wait);