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                         error_packet(remcom_out_buffer, -EINVAL);
1006                         break;
1007                 }
1008
1009                 i = 0;
1010                 remcom_out_buffer[0] = 'm';
1011                 ptr = remcom_out_buffer + 1;
1012                 if (remcom_in_buffer[1] == 'f') {
1013                         /* Each cpu is a shadow thread */
1014                         for_each_online_cpu(cpu) {
1015                                 ks->thr_query = 0;
1016                                 int_to_threadref(thref, -cpu - 2);
1017                                 pack_threadid(ptr, thref);
1018                                 ptr += BUF_THREAD_ID_SIZE;
1019                                 *(ptr++) = ',';
1020                                 i++;
1021                         }
1022                 }
1023
1024                 do_each_thread(g, p) {
1025                         if (i >= ks->thr_query && !finished) {
1026                                 int_to_threadref(thref, p->pid);
1027                                 pack_threadid(ptr, thref);
1028                                 ptr += BUF_THREAD_ID_SIZE;
1029                                 *(ptr++) = ',';
1030                                 ks->thr_query++;
1031                                 if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
1032                                         finished = 1;
1033                         }
1034                         i++;
1035                 } while_each_thread(g, p);
1036
1037                 *(--ptr) = '\0';
1038                 break;
1039
1040         case 'C':
1041                 /* Current thread id */
1042                 strcpy(remcom_out_buffer, "QC");
1043                 ks->threadid = shadow_pid(current->pid);
1044                 int_to_threadref(thref, ks->threadid);
1045                 pack_threadid(remcom_out_buffer + 2, thref);
1046                 break;
1047         case 'T':
1048                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
1049                         error_packet(remcom_out_buffer, -EINVAL);
1050                         break;
1051                 }
1052                 ks->threadid = 0;
1053                 ptr = remcom_in_buffer + 17;
1054                 kgdb_hex2long(&ptr, &ks->threadid);
1055                 if (!getthread(ks->linux_regs, ks->threadid)) {
1056                         error_packet(remcom_out_buffer, -EINVAL);
1057                         break;
1058                 }
1059                 if ((int)ks->threadid > 0) {
1060                         kgdb_mem2hex(getthread(ks->linux_regs,
1061                                         ks->threadid)->comm,
1062                                         remcom_out_buffer, 16);
1063                 } else {
1064                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
1065
1066                         sprintf(tmpstr, "shadowCPU%d",
1067                                         (int)(-ks->threadid - 2));
1068                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
1069                 }
1070                 break;
1071         }
1072 }
1073
1074 /* Handle the 'H' task query packets */
1075 static void gdb_cmd_task(struct kgdb_state *ks)
1076 {
1077         struct task_struct *thread;
1078         char *ptr;
1079
1080         switch (remcom_in_buffer[1]) {
1081         case 'g':
1082                 ptr = &remcom_in_buffer[2];
1083                 kgdb_hex2long(&ptr, &ks->threadid);
1084                 thread = getthread(ks->linux_regs, ks->threadid);
1085                 if (!thread && ks->threadid > 0) {
1086                         error_packet(remcom_out_buffer, -EINVAL);
1087                         break;
1088                 }
1089                 kgdb_usethread = thread;
1090                 ks->kgdb_usethreadid = ks->threadid;
1091                 strcpy(remcom_out_buffer, "OK");
1092                 break;
1093         case 'c':
1094                 ptr = &remcom_in_buffer[2];
1095                 kgdb_hex2long(&ptr, &ks->threadid);
1096                 if (!ks->threadid) {
1097                         kgdb_contthread = NULL;
1098                 } else {
1099                         thread = getthread(ks->linux_regs, ks->threadid);
1100                         if (!thread && ks->threadid > 0) {
1101                                 error_packet(remcom_out_buffer, -EINVAL);
1102                                 break;
1103                         }
1104                         kgdb_contthread = thread;
1105                 }
1106                 strcpy(remcom_out_buffer, "OK");
1107                 break;
1108         }
1109 }
1110
1111 /* Handle the 'T' thread query packets */
1112 static void gdb_cmd_thread(struct kgdb_state *ks)
1113 {
1114         char *ptr = &remcom_in_buffer[1];
1115         struct task_struct *thread;
1116
1117         kgdb_hex2long(&ptr, &ks->threadid);
1118         thread = getthread(ks->linux_regs, ks->threadid);
1119         if (thread)
1120                 strcpy(remcom_out_buffer, "OK");
1121         else
1122                 error_packet(remcom_out_buffer, -EINVAL);
1123 }
1124
1125 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
1126 static void gdb_cmd_break(struct kgdb_state *ks)
1127 {
1128         /*
1129          * Since GDB-5.3, it's been drafted that '0' is a software
1130          * breakpoint, '1' is a hardware breakpoint, so let's do that.
1131          */
1132         char *bpt_type = &remcom_in_buffer[1];
1133         char *ptr = &remcom_in_buffer[2];
1134         unsigned long addr;
1135         unsigned long length;
1136         int error = 0;
1137
1138         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
1139                 /* Unsupported */
1140                 if (*bpt_type > '4')
1141                         return;
1142         } else {
1143                 if (*bpt_type != '0' && *bpt_type != '1')
1144                         /* Unsupported. */
1145                         return;
1146         }
1147
1148         /*
1149          * Test if this is a hardware breakpoint, and
1150          * if we support it:
1151          */
1152         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
1153                 /* Unsupported. */
1154                 return;
1155
1156         if (*(ptr++) != ',') {
1157                 error_packet(remcom_out_buffer, -EINVAL);
1158                 return;
1159         }
1160         if (!kgdb_hex2long(&ptr, &addr)) {
1161                 error_packet(remcom_out_buffer, -EINVAL);
1162                 return;
1163         }
1164         if (*(ptr++) != ',' ||
1165                 !kgdb_hex2long(&ptr, &length)) {
1166                 error_packet(remcom_out_buffer, -EINVAL);
1167                 return;
1168         }
1169
1170         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
1171                 error = kgdb_set_sw_break(addr);
1172         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
1173                 error = kgdb_remove_sw_break(addr);
1174         else if (remcom_in_buffer[0] == 'Z')
1175                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
1176                         (int)length, *bpt_type - '0');
1177         else if (remcom_in_buffer[0] == 'z')
1178                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
1179                         (int) length, *bpt_type - '0');
1180
1181         if (error == 0)
1182                 strcpy(remcom_out_buffer, "OK");
1183         else
1184                 error_packet(remcom_out_buffer, error);
1185 }
1186
1187 /* Handle the 'C' signal / exception passing packets */
1188 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
1189 {
1190         /* C09 == pass exception
1191          * C15 == detach kgdb, pass exception
1192          */
1193         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
1194
1195                 ks->pass_exception = 1;
1196                 remcom_in_buffer[0] = 'c';
1197
1198         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
1199
1200                 ks->pass_exception = 1;
1201                 remcom_in_buffer[0] = 'D';
1202                 remove_all_break();
1203                 kgdb_connected = 0;
1204                 return 1;
1205
1206         } else {
1207                 error_packet(remcom_out_buffer, -EINVAL);
1208                 return 0;
1209         }
1210
1211         /* Indicate fall through */
1212         return -1;
1213 }
1214
1215 /*
1216  * This function performs all gdbserial command procesing
1217  */
1218 static int gdb_serial_stub(struct kgdb_state *ks)
1219 {
1220         int error = 0;
1221         int tmp;
1222
1223         /* Clear the out buffer. */
1224         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1225
1226         if (kgdb_connected) {
1227                 unsigned char thref[8];
1228                 char *ptr;
1229
1230                 /* Reply to host that an exception has occurred */
1231                 ptr = remcom_out_buffer;
1232                 *ptr++ = 'T';
1233                 ptr = pack_hex_byte(ptr, ks->signo);
1234                 ptr += strlen(strcpy(ptr, "thread:"));
1235                 int_to_threadref(thref, shadow_pid(current->pid));
1236                 ptr = pack_threadid(ptr, thref);
1237                 *ptr++ = ';';
1238                 put_packet(remcom_out_buffer);
1239         }
1240
1241         kgdb_usethread = kgdb_info[ks->cpu].task;
1242         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
1243         ks->pass_exception = 0;
1244
1245         while (1) {
1246                 error = 0;
1247
1248                 /* Clear the out buffer. */
1249                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1250
1251                 get_packet(remcom_in_buffer);
1252
1253                 switch (remcom_in_buffer[0]) {
1254                 case '?': /* gdbserial status */
1255                         gdb_cmd_status(ks);
1256                         break;
1257                 case 'g': /* return the value of the CPU registers */
1258                         gdb_cmd_getregs(ks);
1259                         break;
1260                 case 'G': /* set the value of the CPU registers - return OK */
1261                         gdb_cmd_setregs(ks);
1262                         break;
1263                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1264                         gdb_cmd_memread(ks);
1265                         break;
1266                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1267                         gdb_cmd_memwrite(ks);
1268                         break;
1269                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1270                         gdb_cmd_binwrite(ks);
1271                         break;
1272                         /* kill or detach. KGDB should treat this like a
1273                          * continue.
1274                          */
1275                 case 'D': /* Debugger detach */
1276                 case 'k': /* Debugger detach via kill */
1277                         gdb_cmd_detachkill(ks);
1278                         goto default_handle;
1279                 case 'R': /* Reboot */
1280                         if (gdb_cmd_reboot(ks))
1281                                 goto default_handle;
1282                         break;
1283                 case 'q': /* query command */
1284                         gdb_cmd_query(ks);
1285                         break;
1286                 case 'H': /* task related */
1287                         gdb_cmd_task(ks);
1288                         break;
1289                 case 'T': /* Query thread status */
1290                         gdb_cmd_thread(ks);
1291                         break;
1292                 case 'z': /* Break point remove */
1293                 case 'Z': /* Break point set */
1294                         gdb_cmd_break(ks);
1295                         break;
1296                 case 'C': /* Exception passing */
1297                         tmp = gdb_cmd_exception_pass(ks);
1298                         if (tmp > 0)
1299                                 goto default_handle;
1300                         if (tmp == 0)
1301                                 break;
1302                         /* Fall through on tmp < 0 */
1303                 case 'c': /* Continue packet */
1304                 case 's': /* Single step packet */
1305                         if (kgdb_contthread && kgdb_contthread != current) {
1306                                 /* Can't switch threads in kgdb */
1307                                 error_packet(remcom_out_buffer, -EINVAL);
1308                                 break;
1309                         }
1310                         kgdb_activate_sw_breakpoints();
1311                         /* Fall through to default processing */
1312                 default:
1313 default_handle:
1314                         error = kgdb_arch_handle_exception(ks->ex_vector,
1315                                                 ks->signo,
1316                                                 ks->err_code,
1317                                                 remcom_in_buffer,
1318                                                 remcom_out_buffer,
1319                                                 ks->linux_regs);
1320                         /*
1321                          * Leave cmd processing on error, detach,
1322                          * kill, continue, or single step.
1323                          */
1324                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1325                             remcom_in_buffer[0] == 'k') {
1326                                 error = 0;
1327                                 goto kgdb_exit;
1328                         }
1329
1330                 }
1331
1332                 /* reply to the request */
1333                 put_packet(remcom_out_buffer);
1334         }
1335
1336 kgdb_exit:
1337         if (ks->pass_exception)
1338                 error = 1;
1339         return error;
1340 }
1341
1342 static int kgdb_reenter_check(struct kgdb_state *ks)
1343 {
1344         unsigned long addr;
1345
1346         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
1347                 return 0;
1348
1349         /* Panic on recursive debugger calls: */
1350         exception_level++;
1351         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
1352         kgdb_deactivate_sw_breakpoints();
1353
1354         /*
1355          * If the break point removed ok at the place exception
1356          * occurred, try to recover and print a warning to the end
1357          * user because the user planted a breakpoint in a place that
1358          * KGDB needs in order to function.
1359          */
1360         if (kgdb_remove_sw_break(addr) == 0) {
1361                 exception_level = 0;
1362                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1363                 kgdb_activate_sw_breakpoints();
1364                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
1365                         addr);
1366                 WARN_ON_ONCE(1);
1367
1368                 return 1;
1369         }
1370         remove_all_break();
1371         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1372
1373         if (exception_level > 1) {
1374                 dump_stack();
1375                 panic("Recursive entry to debugger");
1376         }
1377
1378         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
1379         dump_stack();
1380         panic("Recursive entry to debugger");
1381
1382         return 1;
1383 }
1384
1385 /*
1386  * kgdb_handle_exception() - main entry point from a kernel exception
1387  *
1388  * Locking hierarchy:
1389  *      interface locks, if any (begin_session)
1390  *      kgdb lock (kgdb_active)
1391  */
1392 int
1393 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
1394 {
1395         struct kgdb_state kgdb_var;
1396         struct kgdb_state *ks = &kgdb_var;
1397         unsigned long flags;
1398         int error = 0;
1399         int i, cpu;
1400
1401         ks->cpu                 = raw_smp_processor_id();
1402         ks->ex_vector           = evector;
1403         ks->signo               = signo;
1404         ks->ex_vector           = evector;
1405         ks->err_code            = ecode;
1406         ks->kgdb_usethreadid    = 0;
1407         ks->linux_regs          = regs;
1408
1409         if (kgdb_reenter_check(ks))
1410                 return 0; /* Ouch, double exception ! */
1411
1412 acquirelock:
1413         /*
1414          * Interrupts will be restored by the 'trap return' code, except when
1415          * single stepping.
1416          */
1417         local_irq_save(flags);
1418
1419         cpu = raw_smp_processor_id();
1420
1421         /*
1422          * Acquire the kgdb_active lock:
1423          */
1424         while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
1425                 cpu_relax();
1426
1427         /*
1428          * Do not start the debugger connection on this CPU if the last
1429          * instance of the exception handler wanted to come into the
1430          * debugger on a different CPU via a single step
1431          */
1432         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
1433             atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
1434
1435                 atomic_set(&kgdb_active, -1);
1436                 touch_softlockup_watchdog();
1437                 clocksource_touch_watchdog();
1438                 local_irq_restore(flags);
1439
1440                 goto acquirelock;
1441         }
1442
1443         if (!kgdb_io_ready(1)) {
1444                 error = 1;
1445                 goto kgdb_restore; /* No I/O connection, so resume the system */
1446         }
1447
1448         /*
1449          * Don't enter if we have hit a removed breakpoint.
1450          */
1451         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
1452                 goto kgdb_restore;
1453
1454         /* Call the I/O driver's pre_exception routine */
1455         if (kgdb_io_ops->pre_exception)
1456                 kgdb_io_ops->pre_exception();
1457
1458         kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
1459         kgdb_info[ks->cpu].task = current;
1460
1461         kgdb_disable_hw_debug(ks->linux_regs);
1462
1463         /*
1464          * Get the passive CPU lock which will hold all the non-primary
1465          * CPU in a spin state while the debugger is active
1466          */
1467         if (!kgdb_single_step) {
1468                 for (i = 0; i < NR_CPUS; i++)
1469                         atomic_set(&passive_cpu_wait[i], 1);
1470         }
1471
1472         /*
1473          * spin_lock code is good enough as a barrier so we don't
1474          * need one here:
1475          */
1476         atomic_set(&cpu_in_kgdb[ks->cpu], 1);
1477
1478 #ifdef CONFIG_SMP
1479         /* Signal the other CPUs to enter kgdb_wait() */
1480         if ((!kgdb_single_step) && kgdb_do_roundup)
1481                 kgdb_roundup_cpus(flags);
1482 #endif
1483
1484         /*
1485          * Wait for the other CPUs to be notified and be waiting for us:
1486          */
1487         for_each_online_cpu(i) {
1488                 while (!atomic_read(&cpu_in_kgdb[i]))
1489                         cpu_relax();
1490         }
1491
1492         /*
1493          * At this point the primary processor is completely
1494          * in the debugger and all secondary CPUs are quiescent
1495          */
1496         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
1497         kgdb_deactivate_sw_breakpoints();
1498         kgdb_single_step = 0;
1499         kgdb_contthread = current;
1500         exception_level = 0;
1501
1502         /* Talk to debugger with gdbserial protocol */
1503         error = gdb_serial_stub(ks);
1504
1505         /* Call the I/O driver's post_exception routine */
1506         if (kgdb_io_ops->post_exception)
1507                 kgdb_io_ops->post_exception();
1508
1509         kgdb_info[ks->cpu].debuggerinfo = NULL;
1510         kgdb_info[ks->cpu].task = NULL;
1511         atomic_set(&cpu_in_kgdb[ks->cpu], 0);
1512
1513         if (!kgdb_single_step) {
1514                 for (i = NR_CPUS-1; i >= 0; i--)
1515                         atomic_set(&passive_cpu_wait[i], 0);
1516                 /*
1517                  * Wait till all the CPUs have quit
1518                  * from the debugger.
1519                  */
1520                 for_each_online_cpu(i) {
1521                         while (atomic_read(&cpu_in_kgdb[i]))
1522                                 cpu_relax();
1523                 }
1524         }
1525
1526 kgdb_restore:
1527         /* Free kgdb_active */
1528         atomic_set(&kgdb_active, -1);
1529         touch_softlockup_watchdog();
1530         clocksource_touch_watchdog();
1531         local_irq_restore(flags);
1532
1533         return error;
1534 }
1535
1536 int kgdb_nmicallback(int cpu, void *regs)
1537 {
1538 #ifdef CONFIG_SMP
1539         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
1540                         atomic_read(&kgdb_active) != cpu &&
1541                         atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
1542                 kgdb_wait((struct pt_regs *)regs);
1543                 return 0;
1544         }
1545 #endif
1546         return 1;
1547 }
1548
1549 static void kgdb_console_write(struct console *co, const char *s,
1550    unsigned count)
1551 {
1552         unsigned long flags;
1553
1554         /* If we're debugging, or KGDB has not connected, don't try
1555          * and print. */
1556         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
1557                 return;
1558
1559         local_irq_save(flags);
1560         kgdb_msg_write(s, count);
1561         local_irq_restore(flags);
1562 }
1563
1564 static struct console kgdbcons = {
1565         .name           = "kgdb",
1566         .write          = kgdb_console_write,
1567         .flags          = CON_PRINTBUFFER | CON_ENABLED,
1568         .index          = -1,
1569 };
1570
1571 #ifdef CONFIG_MAGIC_SYSRQ
1572 static void sysrq_handle_gdb(int key, struct tty_struct *tty)
1573 {
1574         if (!kgdb_io_ops) {
1575                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
1576                 return;
1577         }
1578         if (!kgdb_connected)
1579                 printk(KERN_CRIT "Entering KGDB\n");
1580
1581         kgdb_breakpoint();
1582 }
1583
1584 static struct sysrq_key_op sysrq_gdb_op = {
1585         .handler        = sysrq_handle_gdb,
1586         .help_msg       = "debug(G)",
1587         .action_msg     = "DEBUG",
1588 };
1589 #endif
1590
1591 static void kgdb_register_callbacks(void)
1592 {
1593         if (!kgdb_io_module_registered) {
1594                 kgdb_io_module_registered = 1;
1595                 kgdb_arch_init();
1596 #ifdef CONFIG_MAGIC_SYSRQ
1597                 register_sysrq_key('g', &sysrq_gdb_op);
1598 #endif
1599                 if (kgdb_use_con && !kgdb_con_registered) {
1600                         register_console(&kgdbcons);
1601                         kgdb_con_registered = 1;
1602                 }
1603         }
1604 }
1605
1606 static void kgdb_unregister_callbacks(void)
1607 {
1608         /*
1609          * When this routine is called KGDB should unregister from the
1610          * panic handler and clean up, making sure it is not handling any
1611          * break exceptions at the time.
1612          */
1613         if (kgdb_io_module_registered) {
1614                 kgdb_io_module_registered = 0;
1615                 kgdb_arch_exit();
1616 #ifdef CONFIG_MAGIC_SYSRQ
1617                 unregister_sysrq_key('g', &sysrq_gdb_op);
1618 #endif
1619                 if (kgdb_con_registered) {
1620                         unregister_console(&kgdbcons);
1621                         kgdb_con_registered = 0;
1622                 }
1623         }
1624 }
1625
1626 static void kgdb_initial_breakpoint(void)
1627 {
1628         kgdb_break_asap = 0;
1629
1630         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
1631         kgdb_breakpoint();
1632 }
1633
1634 /**
1635  *      kgdb_register_io_module - register KGDB IO module
1636  *      @new_kgdb_io_ops: the io ops vector
1637  *
1638  *      Register it with the KGDB core.
1639  */
1640 int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
1641 {
1642         int err;
1643
1644         spin_lock(&kgdb_registration_lock);
1645
1646         if (kgdb_io_ops) {
1647                 spin_unlock(&kgdb_registration_lock);
1648
1649                 printk(KERN_ERR "kgdb: Another I/O driver is already "
1650                                 "registered with KGDB.\n");
1651                 return -EBUSY;
1652         }
1653
1654         if (new_kgdb_io_ops->init) {
1655                 err = new_kgdb_io_ops->init();
1656                 if (err) {
1657                         spin_unlock(&kgdb_registration_lock);
1658                         return err;
1659                 }
1660         }
1661
1662         kgdb_io_ops = new_kgdb_io_ops;
1663
1664         spin_unlock(&kgdb_registration_lock);
1665
1666         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
1667                new_kgdb_io_ops->name);
1668
1669         /* Arm KGDB now. */
1670         kgdb_register_callbacks();
1671
1672         if (kgdb_break_asap)
1673                 kgdb_initial_breakpoint();
1674
1675         return 0;
1676 }
1677 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1678
1679 /**
1680  *      kkgdb_unregister_io_module - unregister KGDB IO module
1681  *      @old_kgdb_io_ops: the io ops vector
1682  *
1683  *      Unregister it with the KGDB core.
1684  */
1685 void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
1686 {
1687         BUG_ON(kgdb_connected);
1688
1689         /*
1690          * KGDB is no longer able to communicate out, so
1691          * unregister our callbacks and reset state.
1692          */
1693         kgdb_unregister_callbacks();
1694
1695         spin_lock(&kgdb_registration_lock);
1696
1697         WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
1698         kgdb_io_ops = NULL;
1699
1700         spin_unlock(&kgdb_registration_lock);
1701
1702         printk(KERN_INFO
1703                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
1704                 old_kgdb_io_ops->name);
1705 }
1706 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1707
1708 /**
1709  * kgdb_breakpoint - generate breakpoint exception
1710  *
1711  * This function will generate a breakpoint exception.  It is used at the
1712  * beginning of a program to sync up with a debugger and can be used
1713  * otherwise as a quick means to stop program execution and "break" into
1714  * the debugger.
1715  */
1716 void kgdb_breakpoint(void)
1717 {
1718         atomic_set(&kgdb_setting_breakpoint, 1);
1719         wmb(); /* Sync point before breakpoint */
1720         arch_kgdb_breakpoint();
1721         wmb(); /* Sync point after breakpoint */
1722         atomic_set(&kgdb_setting_breakpoint, 0);
1723 }
1724 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1725
1726 static int __init opt_kgdb_wait(char *str)
1727 {
1728         kgdb_break_asap = 1;
1729
1730         if (kgdb_io_module_registered)
1731                 kgdb_initial_breakpoint();
1732
1733         return 0;
1734 }
1735
1736 early_param("kgdbwait", opt_kgdb_wait);