kernel/kernel/debug/debug_core.c

   1 /*
   2  * Kernel Debug Core
   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@ucw.cz>
  10  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
  11  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
  12  * Copyright (C) 2005-2009 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
  31 #define pr_fmt(fmt) "KGDB: " fmt
  32
  33 #include <linux/pid_namespace.h>
  34 #include <linux/clocksource.h>
  35 #include <linux/serial_core.h>
  36 #include <linux/interrupt.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/console.h>
  39 #include <linux/threads.h>
  40 #include <linux/uaccess.h>
  41 #include <linux/kernel.h>
  42 #include <linux/module.h>
  43 #include <linux/ptrace.h>
  44 #include <linux/string.h>
  45 #include <linux/delay.h>
  46 #include <linux/sched.h>
  47 #include <linux/sysrq.h>
  48 #include <linux/reboot.h>
  49 #include <linux/init.h>
  50 #include <linux/kgdb.h>
  51 #include <linux/kdb.h>
  52 #include <linux/pid.h>
  53 #include <linux/smp.h>
  54 #include <linux/mm.h>
  55 #include <linux/vmacache.h>
  56 #include <linux/rcupdate.h>
  57
  58 #include <asm/cacheflush.h>
  59 #include <asm/byteorder.h>
  60 #include <linux/atomic.h>
  61
  62 #include "debug_core.h"
  63
  64 static int kgdb_break_asap;
  65
  66 struct debuggerinfo_struct kgdb_info[NR_CPUS];
  67
  68 /**
  69  * kgdb_connected - Is a host GDB connected to us?
  70  */
  71 int                             kgdb_connected;
  72 EXPORT_SYMBOL_GPL(kgdb_connected);
  73
  74 /* All the KGDB handlers are installed */
  75 int                     kgdb_io_module_registered;
  76
  77 /* Guard for recursive entry */
  78 static int                      exception_level;
  79
  80 struct kgdb_io          *dbg_io_ops;
  81 static DEFINE_SPINLOCK(kgdb_registration_lock);
  82
  83 /* Action for the reboot notifiter, a global allow kdb to change it */
  84 static int kgdbreboot;
  85 /* kgdb console driver is loaded */
  86 static int kgdb_con_registered;
  87 /* determine if kgdb console output should be used */
  88 static int kgdb_use_con;
  89 /* Flag for alternate operations for early debugging */
  90 bool dbg_is_early = true;
  91 /* Next cpu to become the master debug core */
  92 int dbg_switch_cpu;
  93
  94 /* Use kdb or gdbserver mode */
  95 int dbg_kdb_mode = 1;
  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 module_param(kgdbreboot, int, 0644);
 107
 108 /*
 109  * Holds information about breakpoints in a kernel. These breakpoints are
 110  * added and removed by gdb.
 111  */
 112 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
 113         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
 114 };
 115
 116 /*
 117  * The CPU# of the active CPU, or -1 if none:
 118  */
 119 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 120 EXPORT_SYMBOL_GPL(kgdb_active);
 121 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
 122 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
 123
 124 /*
 125  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 126  * bootup code (which might not have percpu set up yet):
 127  */
 128 static atomic_t                 masters_in_kgdb;
 129 static atomic_t                 slaves_in_kgdb;
 130 static atomic_t                 kgdb_break_tasklet_var;
 131 atomic_t                        kgdb_setting_breakpoint;
 132
 133 struct task_struct              *kgdb_usethread;
 134 struct task_struct              *kgdb_contthread;
 135
 136 int                             kgdb_single_step;
 137 static pid_t                    kgdb_sstep_pid;
 138
 139 /* to keep track of the CPU which is doing the single stepping*/
 140 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 141
 142 /*
 143  * If you are debugging a problem where roundup (the collection of
 144  * all other CPUs) is a problem [this should be extremely rare],
 145  * then use the nokgdbroundup option to avoid roundup. In that case
 146  * the other CPUs might interfere with your debugging context, so
 147  * use this with care:
 148  */
 149 static int kgdb_do_roundup = 1;
 150
 151 static int __init opt_nokgdbroundup(char *str)
 152 {
 153         kgdb_do_roundup = 0;
 154
 155         return 0;
 156 }
 157
 158 early_param("nokgdbroundup", opt_nokgdbroundup);
 159
 160 /*
 161  * Finally, some KGDB code :-)
 162  */
 163
 164 /*
 165  * Weak aliases for breakpoint management,
 166  * can be overriden by architectures when needed:
 167  */
 168 int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
 169 {
 170         int err;
 171
 172         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
 173                                 BREAK_INSTR_SIZE);
 174         if (err)
 175                 return err;
 176         err = probe_kernel_write((char *)bpt->bpt_addr,
 177                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
 178         return err;
 179 }
 180
 181 int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
 182 {
 183         return probe_kernel_write((char *)bpt->bpt_addr,
 184                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
 185 }
 186
 187 int __weak kgdb_validate_break_address(unsigned long addr)
 188 {
 189         struct kgdb_bkpt tmp;
 190         int err;
 191         /* Validate setting the breakpoint and then removing it.  If the
 192          * remove fails, the kernel needs to emit a bad message because we
 193          * are deep trouble not being able to put things back the way we
 194          * found them.
 195          */
 196         tmp.bpt_addr = addr;
 197         err = kgdb_arch_set_breakpoint(&tmp);
 198         if (err)
 199                 return err;
 200         err = kgdb_arch_remove_breakpoint(&tmp);
 201         if (err)
 202                 pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n",
 203                        addr);
 204         return err;
 205 }
 206
 207 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 208 {
 209         return instruction_pointer(regs);
 210 }
 211
 212 int __weak kgdb_arch_init(void)
 213 {
 214         return 0;
 215 }
 216
 217 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 218 {
 219         return 0;
 220 }
 221
 222 /*
 223  * Some architectures need cache flushes when we set/clear a
 224  * breakpoint:
 225  */
 226 static void kgdb_flush_swbreak_addr(unsigned long addr)
 227 {
 228         if (!CACHE_FLUSH_IS_SAFE)
 229                 return;
 230
 231         if (current->mm) {
 232                 int i;
 233
 234                 for (i = 0; i < VMACACHE_SIZE; i++) {
 235                         if (!current->vmacache[i])
 236                                 continue;
 237                         flush_cache_range(current->vmacache[i],
 238                                           addr, addr + BREAK_INSTR_SIZE);
 239                 }
 240         }
 241
 242         /* Force flush instruction cache if it was outside the mm */
 243         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 244 }
 245
 246 /*
 247  * SW breakpoint management:
 248  */
 249 int dbg_activate_sw_breakpoints(void)
 250 {
 251         int error;
 252         int ret = 0;
 253         int i;
 254
 255         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 256                 if (kgdb_break[i].state != BP_SET)
 257                         continue;
 258
 259                 error = kgdb_arch_set_breakpoint(&kgdb_break[i]);
 260                 if (error) {
 261                         ret = error;
 262                         pr_info("BP install failed: %lx\n",
 263                                 kgdb_break[i].bpt_addr);
 264                         continue;
 265                 }
 266
 267                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 268                 kgdb_break[i].state = BP_ACTIVE;
 269         }
 270         return ret;
 271 }
 272
 273 int dbg_set_sw_break(unsigned long addr)
 274 {
 275         int err = kgdb_validate_break_address(addr);
 276         int breakno = -1;
 277         int i;
 278
 279         if (err)
 280                 return err;
 281
 282         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 283                 if ((kgdb_break[i].state == BP_SET) &&
 284                                         (kgdb_break[i].bpt_addr == addr))
 285                         return -EEXIST;
 286         }
 287         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 288                 if (kgdb_break[i].state == BP_REMOVED &&
 289                                         kgdb_break[i].bpt_addr == addr) {
 290                         breakno = i;
 291                         break;
 292                 }
 293         }
 294
 295         if (breakno == -1) {
 296                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 297                         if (kgdb_break[i].state == BP_UNDEFINED) {
 298                                 breakno = i;
 299                                 break;
 300                         }
 301                 }
 302         }
 303
 304         if (breakno == -1)
 305                 return -E2BIG;
 306
 307         kgdb_break[breakno].state = BP_SET;
 308         kgdb_break[breakno].type = BP_BREAKPOINT;
 309         kgdb_break[breakno].bpt_addr = addr;
 310
 311         return 0;
 312 }
 313
 314 int dbg_deactivate_sw_breakpoints(void)
 315 {
 316         int error;
 317         int ret = 0;
 318         int i;
 319
 320         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 321                 if (kgdb_break[i].state != BP_ACTIVE)
 322                         continue;
 323                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 324                 if (error) {
 325                         pr_info("BP remove failed: %lx\n",
 326                                 kgdb_break[i].bpt_addr);
 327                         ret = error;
 328                 }
 329
 330                 kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr);
 331                 kgdb_break[i].state = BP_SET;
 332         }
 333         return ret;
 334 }
 335
 336 int dbg_remove_sw_break(unsigned long addr)
 337 {
 338         int i;
 339
 340         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 341                 if ((kgdb_break[i].state == BP_SET) &&
 342                                 (kgdb_break[i].bpt_addr == addr)) {
 343                         kgdb_break[i].state = BP_REMOVED;
 344                         return 0;
 345                 }
 346         }
 347         return -ENOENT;
 348 }
 349
 350 int kgdb_isremovedbreak(unsigned long addr)
 351 {
 352         int i;
 353
 354         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 355                 if ((kgdb_break[i].state == BP_REMOVED) &&
 356                                         (kgdb_break[i].bpt_addr == addr))
 357                         return 1;
 358         }
 359         return 0;
 360 }
 361
 362 int dbg_remove_all_break(void)
 363 {
 364         int error;
 365         int i;
 366
 367         /* Clear memory breakpoints. */
 368         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 369                 if (kgdb_break[i].state != BP_ACTIVE)
 370                         goto setundefined;
 371                 error = kgdb_arch_remove_breakpoint(&kgdb_break[i]);
 372                 if (error)
 373                         pr_err("breakpoint remove failed: %lx\n",
 374                                kgdb_break[i].bpt_addr);
 375 setundefined:
 376                 kgdb_break[i].state = BP_UNDEFINED;
 377         }
 378
 379         /* Clear hardware breakpoints. */
 380         if (arch_kgdb_ops.remove_all_hw_break)
 381                 arch_kgdb_ops.remove_all_hw_break();
 382
 383         return 0;
 384 }
 385
 386 /*
 387  * Return true if there is a valid kgdb I/O module.  Also if no
 388  * debugger is attached a message can be printed to the console about
 389  * waiting for the debugger to attach.
 390  *
 391  * The print_wait argument is only to be true when called from inside
 392  * the core kgdb_handle_exception, because it will wait for the
 393  * debugger to attach.
 394  */
 395 static int kgdb_io_ready(int print_wait)
 396 {
 397         if (!dbg_io_ops)
 398                 return 0;
 399         if (kgdb_connected)
 400                 return 1;
 401         if (atomic_read(&kgdb_setting_breakpoint))
 402                 return 1;
 403         if (print_wait) {
 404 #ifdef CONFIG_KGDB_KDB
 405                 if (!dbg_kdb_mode)
 406                         pr_crit("waiting... or $3#33 for KDB\n");
 407 #else
 408                 pr_crit("Waiting for remote debugger\n");
 409 #endif
 410         }
 411         return 1;
 412 }
 413
 414 static int kgdb_reenter_check(struct kgdb_state *ks)
 415 {
 416         unsigned long addr;
 417
 418         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 419                 return 0;
 420
 421         /* Panic on recursive debugger calls: */
 422         exception_level++;
 423         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 424         dbg_deactivate_sw_breakpoints();
 425
 426         /*
 427          * If the break point removed ok at the place exception
 428          * occurred, try to recover and print a warning to the end
 429          * user because the user planted a breakpoint in a place that
 430          * KGDB needs in order to function.
 431          */
 432         if (dbg_remove_sw_break(addr) == 0) {
 433                 exception_level = 0;
 434                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 435                 dbg_activate_sw_breakpoints();
 436                 pr_crit("re-enter error: breakpoint removed %lx\n", addr);
 437                 WARN_ON_ONCE(1);
 438
 439                 return 1;
 440         }
 441         dbg_remove_all_break();
 442         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 443
 444         if (exception_level > 1) {
 445                 dump_stack();
 446                 panic("Recursive entry to debugger");
 447         }
 448
 449         pr_crit("re-enter exception: ALL breakpoints killed\n");
 450 #ifdef CONFIG_KGDB_KDB
 451         /* Allow kdb to debug itself one level */
 452         return 0;
 453 #endif
 454         dump_stack();
 455         panic("Recursive entry to debugger");
 456
 457         return 1;
 458 }
 459
 460 static void dbg_touch_watchdogs(void)
 461 {
 462         touch_softlockup_watchdog_sync();
 463         clocksource_touch_watchdog();
 464         rcu_cpu_stall_reset();
 465 }
 466
 467 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 468                 int exception_state)
 469 {
 470         unsigned long flags;
 471         int sstep_tries = 100;
 472         int error;
 473         int cpu;
 474         int trace_on = 0;
 475         int online_cpus = num_online_cpus();
 476         u64 time_left;
 477
 478         kgdb_info[ks->cpu].enter_kgdb++;
 479         kgdb_info[ks->cpu].exception_state |= exception_state;
 480
 481         if (exception_state == DCPU_WANT_MASTER)
 482                 atomic_inc(&masters_in_kgdb);
 483         else
 484                 atomic_inc(&slaves_in_kgdb);
 485
 486         if (arch_kgdb_ops.disable_hw_break)
 487                 arch_kgdb_ops.disable_hw_break(regs);
 488
 489 acquirelock:
 490         /*
 491          * Interrupts will be restored by the 'trap return' code, except when
 492          * single stepping.
 493          */
 494         local_irq_save(flags);
 495
 496         cpu = ks->cpu;
 497         kgdb_info[cpu].debuggerinfo = regs;
 498         kgdb_info[cpu].task = current;
 499         kgdb_info[cpu].ret_state = 0;
 500         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 501
 502         /* Make sure the above info reaches the primary CPU */
 503         smp_mb();
 504
 505         if (exception_level == 1) {
 506                 if (raw_spin_trylock(&dbg_master_lock))
 507                         atomic_xchg(&kgdb_active, cpu);
 508                 goto cpu_master_loop;
 509         }
 510
 511         /*
 512          * CPU will loop if it is a slave or request to become a kgdb
 513          * master cpu and acquire the kgdb_active lock:
 514          */
 515         while (1) {
 516 cpu_loop:
 517                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 518                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 519                         goto cpu_master_loop;
 520                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 521                         if (raw_spin_trylock(&dbg_master_lock)) {
 522                                 atomic_xchg(&kgdb_active, cpu);
 523                                 break;
 524                         }
 525                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 526                         if (!raw_spin_is_locked(&dbg_slave_lock))
 527                                 goto return_normal;
 528                 } else {
 529 return_normal:
 530                         /* Return to normal operation by executing any
 531                          * hw breakpoint fixup.
 532                          */
 533                         if (arch_kgdb_ops.correct_hw_break)
 534                                 arch_kgdb_ops.correct_hw_break();
 535                         if (trace_on)
 536                                 tracing_on();
 537                         kgdb_info[cpu].exception_state &=
 538                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 539                         kgdb_info[cpu].enter_kgdb--;
 540                         smp_mb__before_atomic();
 541                         atomic_dec(&slaves_in_kgdb);
 542                         dbg_touch_watchdogs();
 543                         local_irq_restore(flags);
 544                         return 0;
 545                 }
 546                 cpu_relax();
 547         }
 548
 549         /*
 550          * For single stepping, try to only enter on the processor
 551          * that was single stepping.  To guard against a deadlock, the
 552          * kernel will only try for the value of sstep_tries before
 553          * giving up and continuing on.
 554          */
 555         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 556             (kgdb_info[cpu].task &&
 557              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 558                 atomic_set(&kgdb_active, -1);
 559                 raw_spin_unlock(&dbg_master_lock);
 560                 dbg_touch_watchdogs();
 561                 local_irq_restore(flags);
 562
 563                 goto acquirelock;
 564         }
 565
 566         if (!kgdb_io_ready(1)) {
 567                 kgdb_info[cpu].ret_state = 1;
 568                 goto kgdb_restore; /* No I/O connection, resume the system */
 569         }
 570
 571         /*
 572          * Don't enter if we have hit a removed breakpoint.
 573          */
 574         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 575                 goto kgdb_restore;
 576
 577         /* Call the I/O driver's pre_exception routine */
 578         if (dbg_io_ops->pre_exception)
 579                 dbg_io_ops->pre_exception();
 580
 581         /*
 582          * Get the passive CPU lock which will hold all the non-primary
 583          * CPU in a spin state while the debugger is active
 584          */
 585         if (!kgdb_single_step)
 586                 raw_spin_lock(&dbg_slave_lock);
 587
 588 #ifdef CONFIG_SMP
 589         /* If send_ready set, slaves are already waiting */
 590         if (ks->send_ready)
 591                 atomic_set(ks->send_ready, 1);
 592
 593         /* Signal the other CPUs to enter kgdb_wait() */
 594         else if ((!kgdb_single_step) && kgdb_do_roundup)
 595                 kgdb_roundup_cpus(flags);
 596 #endif
 597
 598         /*
 599          * Wait for the other CPUs to be notified and be waiting for us:
 600          */
 601         time_left = loops_per_jiffy * HZ;
 602         while (kgdb_do_roundup && --time_left &&
 603                (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) !=
 604                    online_cpus)
 605                 cpu_relax();
 606         if (!time_left)
 607                 pr_crit("Timed out waiting for secondary CPUs.\n");
 608
 609         /*
 610          * At this point the primary processor is completely
 611          * in the debugger and all secondary CPUs are quiescent
 612          */
 613         dbg_deactivate_sw_breakpoints();
 614         kgdb_single_step = 0;
 615         kgdb_contthread = current;
 616         exception_level = 0;
 617         trace_on = tracing_is_on();
 618         if (trace_on)
 619                 tracing_off();
 620
 621         while (1) {
 622 cpu_master_loop:
 623                 if (dbg_kdb_mode) {
 624                         kgdb_connected = 1;
 625                         error = kdb_stub(ks);
 626                         if (error == -1)
 627                                 continue;
 628                         kgdb_connected = 0;
 629                 } else {
 630                         error = gdb_serial_stub(ks);
 631                 }
 632
 633                 if (error == DBG_PASS_EVENT) {
 634                         dbg_kdb_mode = !dbg_kdb_mode;
 635                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 636                         kgdb_info[dbg_switch_cpu].exception_state |=
 637                                 DCPU_NEXT_MASTER;
 638                         goto cpu_loop;
 639                 } else {
 640                         kgdb_info[cpu].ret_state = error;
 641                         break;
 642                 }
 643         }
 644
 645         /* Call the I/O driver's post_exception routine */
 646         if (dbg_io_ops->post_exception)
 647                 dbg_io_ops->post_exception();
 648
 649         if (!kgdb_single_step) {
 650                 raw_spin_unlock(&dbg_slave_lock);
 651                 /* Wait till all the CPUs have quit from the debugger. */
 652                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
 653                         cpu_relax();
 654         }
 655
 656 kgdb_restore:
 657         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 658                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 659                 if (kgdb_info[sstep_cpu].task)
 660                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 661                 else
 662                         kgdb_sstep_pid = 0;
 663         }
 664         if (arch_kgdb_ops.correct_hw_break)
 665                 arch_kgdb_ops.correct_hw_break();
 666         if (trace_on)
 667                 tracing_on();
 668
 669         kgdb_info[cpu].exception_state &=
 670                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 671         kgdb_info[cpu].enter_kgdb--;
 672         smp_mb__before_atomic();
 673         atomic_dec(&masters_in_kgdb);
 674         /* Free kgdb_active */
 675         atomic_set(&kgdb_active, -1);
 676         raw_spin_unlock(&dbg_master_lock);
 677         dbg_touch_watchdogs();
 678         local_irq_restore(flags);
 679
 680         return kgdb_info[cpu].ret_state;
 681 }
 682
 683 /*
 684  * kgdb_handle_exception() - main entry point from a kernel exception
 685  *
 686  * Locking hierarchy:
 687  *      interface locks, if any (begin_session)
 688  *      kgdb lock (kgdb_active)
 689  */
 690 int
 691 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 692 {
 693         struct kgdb_state kgdb_var;
 694         struct kgdb_state *ks = &kgdb_var;
 695         int ret = 0;
 696
 697         if (arch_kgdb_ops.enable_nmi)
 698                 arch_kgdb_ops.enable_nmi(0);
 699         /*
 700          * Avoid entering the debugger if we were triggered due to an oops
 701          * but panic_timeout indicates the system should automatically
 702          * reboot on panic. We don't want to get stuck waiting for input
 703          * on such systems, especially if its "just" an oops.
 704          */
 705         if (signo != SIGTRAP && panic_timeout)
 706                 return 1;
 707
 708         memset(ks, 0, sizeof(struct kgdb_state));
 709         ks->cpu                 = raw_smp_processor_id();
 710         ks->ex_vector           = evector;
 711         ks->signo               = signo;
 712         ks->err_code            = ecode;
 713         ks->linux_regs          = regs;
 714
 715         if (kgdb_reenter_check(ks))
 716                 goto out; /* Ouch, double exception ! */
 717         if (kgdb_info[ks->cpu].enter_kgdb != 0)
 718                 goto out;
 719
 720         ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 721 out:
 722         if (arch_kgdb_ops.enable_nmi)
 723                 arch_kgdb_ops.enable_nmi(1);
 724         return ret;
 725 }
 726
 727 /*
 728  * GDB places a breakpoint at this function to know dynamically
 729  * loaded objects. It's not defined static so that only one instance with this
 730  * name exists in the kernel.
 731  */
 732
 733 static int module_event(struct notifier_block *self, unsigned long val,
 734         void *data)
 735 {
 736         return 0;
 737 }
 738
 739 static struct notifier_block dbg_module_load_nb = {
 740         .notifier_call  = module_event,
 741 };
 742
 743 int kgdb_nmicallback(int cpu, void *regs)
 744 {
 745 #ifdef CONFIG_SMP
 746         struct kgdb_state kgdb_var;
 747         struct kgdb_state *ks = &kgdb_var;
 748
 749         memset(ks, 0, sizeof(struct kgdb_state));
 750         ks->cpu                 = cpu;
 751         ks->linux_regs          = regs;
 752
 753         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
 754                         raw_spin_is_locked(&dbg_master_lock)) {
 755                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
 756                 return 0;
 757         }
 758 #endif
 759         return 1;
 760 }
 761
 762 int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code,
 763                                                         atomic_t *send_ready)
 764 {
 765 #ifdef CONFIG_SMP
 766         if (!kgdb_io_ready(0) || !send_ready)
 767                 return 1;
 768
 769         if (kgdb_info[cpu].enter_kgdb == 0) {
 770                 struct kgdb_state kgdb_var;
 771                 struct kgdb_state *ks = &kgdb_var;
 772
 773                 memset(ks, 0, sizeof(struct kgdb_state));
 774                 ks->cpu                 = cpu;
 775                 ks->ex_vector           = trapnr;
 776                 ks->signo               = SIGTRAP;
 777                 ks->err_code            = err_code;
 778                 ks->linux_regs          = regs;
 779                 ks->send_ready          = send_ready;
 780                 kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 781                 return 0;
 782         }
 783 #endif
 784         return 1;
 785 }
 786
 787 static void kgdb_console_write(struct console *co, const char *s,
 788    unsigned count)
 789 {
 790         unsigned long flags;
 791
 792         /* If we're debugging, or KGDB has not connected, don't try
 793          * and print. */
 794         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 795                 return;
 796
 797         local_irq_save(flags);
 798         gdbstub_msg_write(s, count);
 799         local_irq_restore(flags);
 800 }
 801
 802 static struct console kgdbcons = {
 803         .name           = "kgdb",
 804         .write          = kgdb_console_write,
 805         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 806         .index          = -1,
 807 };
 808
 809 #ifdef CONFIG_MAGIC_SYSRQ
 810 static void sysrq_handle_dbg(int key)
 811 {
 812         if (!dbg_io_ops) {
 813                 pr_crit("ERROR: No KGDB I/O module available\n");
 814                 return;
 815         }
 816         if (!kgdb_connected) {
 817 #ifdef CONFIG_KGDB_KDB
 818                 if (!dbg_kdb_mode)
 819                         pr_crit("KGDB or $3#33 for KDB\n");
 820 #else
 821                 pr_crit("Entering KGDB\n");
 822 #endif
 823         }
 824
 825         kgdb_breakpoint();
 826 }
 827
 828 static struct sysrq_key_op sysrq_dbg_op = {
 829         .handler        = sysrq_handle_dbg,
 830         .help_msg       = "debug(g)",
 831         .action_msg     = "DEBUG",
 832 };
 833 #endif
 834
 835 static int kgdb_panic_event(struct notifier_block *self,
 836                             unsigned long val,
 837                             void *data)
 838 {
 839         /*
 840          * Avoid entering the debugger if we were triggered due to a panic
 841          * We don't want to get stuck waiting for input from user in such case.
 842          * panic_timeout indicates the system should automatically
 843          * reboot on panic.
 844          */
 845         if (panic_timeout)
 846                 return NOTIFY_DONE;
 847
 848         if (dbg_kdb_mode)
 849                 kdb_printf("PANIC: %s\n", (char *)data);
 850         kgdb_breakpoint();
 851         return NOTIFY_DONE;
 852 }
 853
 854 static struct notifier_block kgdb_panic_event_nb = {
 855        .notifier_call   = kgdb_panic_event,
 856        .priority        = INT_MAX,
 857 };
 858
 859 void __weak kgdb_arch_late(void)
 860 {
 861 }
 862
 863 void __init dbg_late_init(void)
 864 {
 865         dbg_is_early = false;
 866         if (kgdb_io_module_registered)
 867                 kgdb_arch_late();
 868         kdb_init(KDB_INIT_FULL);
 869 }
 870
 871 static int
 872 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
 873 {
 874         /*
 875          * Take the following action on reboot notify depending on value:
 876          *    1 == Enter debugger
 877          *    0 == [the default] detatch debug client
 878          *   -1 == Do nothing... and use this until the board resets
 879          */
 880         switch (kgdbreboot) {
 881         case 1:
 882                 kgdb_breakpoint();
 883         case -1:
 884                 goto done;
 885         }
 886         if (!dbg_kdb_mode)
 887                 gdbstub_exit(code);
 888 done:
 889         return NOTIFY_DONE;
 890 }
 891
 892 static struct notifier_block dbg_reboot_notifier = {
 893         .notifier_call          = dbg_notify_reboot,
 894         .next                   = NULL,
 895         .priority               = INT_MAX,
 896 };
 897
 898 static void kgdb_register_callbacks(void)
 899 {
 900         if (!kgdb_io_module_registered) {
 901                 kgdb_io_module_registered = 1;
 902                 kgdb_arch_init();
 903                 if (!dbg_is_early)
 904                         kgdb_arch_late();
 905                 register_module_notifier(&dbg_module_load_nb);
 906                 register_reboot_notifier(&dbg_reboot_notifier);
 907                 atomic_notifier_chain_register(&panic_notifier_list,
 908                                                &kgdb_panic_event_nb);
 909 #ifdef CONFIG_MAGIC_SYSRQ
 910                 register_sysrq_key('g', &sysrq_dbg_op);
 911 #endif
 912                 if (kgdb_use_con && !kgdb_con_registered) {
 913                         register_console(&kgdbcons);
 914                         kgdb_con_registered = 1;
 915                 }
 916         }
 917 }
 918
 919 static void kgdb_unregister_callbacks(void)
 920 {
 921         /*
 922          * When this routine is called KGDB should unregister from the
 923          * panic handler and clean up, making sure it is not handling any
 924          * break exceptions at the time.
 925          */
 926         if (kgdb_io_module_registered) {
 927                 kgdb_io_module_registered = 0;
 928                 unregister_reboot_notifier(&dbg_reboot_notifier);
 929                 unregister_module_notifier(&dbg_module_load_nb);
 930                 atomic_notifier_chain_unregister(&panic_notifier_list,
 931                                                &kgdb_panic_event_nb);
 932                 kgdb_arch_exit();
 933 #ifdef CONFIG_MAGIC_SYSRQ
 934                 unregister_sysrq_key('g', &sysrq_dbg_op);
 935 #endif
 936                 if (kgdb_con_registered) {
 937                         unregister_console(&kgdbcons);
 938                         kgdb_con_registered = 0;
 939                 }
 940         }
 941 }
 942
 943 /*
 944  * There are times a tasklet needs to be used vs a compiled in
 945  * break point so as to cause an exception outside a kgdb I/O module,
 946  * such as is the case with kgdboe, where calling a breakpoint in the
 947  * I/O driver itself would be fatal.
 948  */
 949 static void kgdb_tasklet_bpt(unsigned long ing)
 950 {
 951         kgdb_breakpoint();
 952         atomic_set(&kgdb_break_tasklet_var, 0);
 953 }
 954
 955 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
 956
 957 void kgdb_schedule_breakpoint(void)
 958 {
 959         if (atomic_read(&kgdb_break_tasklet_var) ||
 960                 atomic_read(&kgdb_active) != -1 ||
 961                 atomic_read(&kgdb_setting_breakpoint))
 962                 return;
 963         atomic_inc(&kgdb_break_tasklet_var);
 964         tasklet_schedule(&kgdb_tasklet_breakpoint);
 965 }
 966 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 967
 968 static void kgdb_initial_breakpoint(void)
 969 {
 970         kgdb_break_asap = 0;
 971
 972         pr_crit("Waiting for connection from remote gdb...\n");
 973         kgdb_breakpoint();
 974 }
 975
 976 /**
 977  *      kgdb_register_io_module - register KGDB IO module
 978  *      @new_dbg_io_ops: the io ops vector
 979  *
 980  *      Register it with the KGDB core.
 981  */
 982 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 983 {
 984         int err;
 985
 986         spin_lock(&kgdb_registration_lock);
 987
 988         if (dbg_io_ops) {
 989                 spin_unlock(&kgdb_registration_lock);
 990
 991                 pr_err("Another I/O driver is already registered with KGDB\n");
 992                 return -EBUSY;
 993         }
 994
 995         if (new_dbg_io_ops->init) {
 996                 err = new_dbg_io_ops->init();
 997                 if (err) {
 998                         spin_unlock(&kgdb_registration_lock);
 999                         return err;
1000                 }
1001         }
1002
1003         dbg_io_ops = new_dbg_io_ops;
1004
1005         spin_unlock(&kgdb_registration_lock);
1006
1007         pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name);
1008
1009         /* Arm KGDB now. */
1010         kgdb_register_callbacks();
1011
1012         if (kgdb_break_asap)
1013                 kgdb_initial_breakpoint();
1014
1015         return 0;
1016 }
1017 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1018
1019 /**
1020  *      kkgdb_unregister_io_module - unregister KGDB IO module
1021  *      @old_dbg_io_ops: the io ops vector
1022  *
1023  *      Unregister it with the KGDB core.
1024  */
1025 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
1026 {
1027         BUG_ON(kgdb_connected);
1028
1029         /*
1030          * KGDB is no longer able to communicate out, so
1031          * unregister our callbacks and reset state.
1032          */
1033         kgdb_unregister_callbacks();
1034
1035         spin_lock(&kgdb_registration_lock);
1036
1037         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
1038         dbg_io_ops = NULL;
1039
1040         spin_unlock(&kgdb_registration_lock);
1041
1042         pr_info("Unregistered I/O driver %s, debugger disabled\n",
1043                 old_dbg_io_ops->name);
1044 }
1045 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1046
1047 int dbg_io_get_char(void)
1048 {
1049         int ret = dbg_io_ops->read_char();
1050         if (ret == NO_POLL_CHAR)
1051                 return -1;
1052         if (!dbg_kdb_mode)
1053                 return ret;
1054         if (ret == 127)
1055                 return 8;
1056         return ret;
1057 }
1058
1059 /**
1060  * kgdb_breakpoint - generate breakpoint exception
1061  *
1062  * This function will generate a breakpoint exception.  It is used at the
1063  * beginning of a program to sync up with a debugger and can be used
1064  * otherwise as a quick means to stop program execution and "break" into
1065  * the debugger.
1066  */
1067 noinline void kgdb_breakpoint(void)
1068 {
1069         atomic_inc(&kgdb_setting_breakpoint);
1070         wmb(); /* Sync point before breakpoint */
1071         arch_kgdb_breakpoint();
1072         wmb(); /* Sync point after breakpoint */
1073         atomic_dec(&kgdb_setting_breakpoint);
1074 }
1075 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1076
1077 static int __init opt_kgdb_wait(char *str)
1078 {
1079         kgdb_break_asap = 1;
1080
1081         kdb_init(KDB_INIT_EARLY);
1082         if (kgdb_io_module_registered)
1083                 kgdb_initial_breakpoint();
1084
1085         return 0;
1086 }
1087
1088 early_param("kgdbwait", opt_kgdb_wait);