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