Pileus Git - ~andy/linux/blob - 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 #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/string.h>
  41 #include <linux/delay.h>
  42 #include <linux/sched.h>
  43 #include <linux/sysrq.h>
  44 #include <linux/reboot.h>
  45 #include <linux/init.h>
  46 #include <linux/kgdb.h>
  47 #include <linux/kdb.h>
  48 #include <linux/pid.h>
  49 #include <linux/smp.h>
  50 #include <linux/mm.h>
  51 #include <linux/rcupdate.h>
  52
  53 #include <asm/cacheflush.h>
  54 #include <asm/byteorder.h>
  55 #include <linux/atomic.h>
  56 #include <asm/system.h>
  57
  58 #include "debug_core.h"
  59
  60 static int kgdb_break_asap;
  61
  62 struct debuggerinfo_struct kgdb_info[NR_CPUS];
  63
  64 /**
  65  * kgdb_connected - Is a host GDB connected to us?
  66  */
  67 int                             kgdb_connected;
  68 EXPORT_SYMBOL_GPL(kgdb_connected);
  69
  70 /* All the KGDB handlers are installed */
  71 int                     kgdb_io_module_registered;
  72
  73 /* Guard for recursive entry */
  74 static int                      exception_level;
  75
  76 struct kgdb_io          *dbg_io_ops;
  77 static DEFINE_SPINLOCK(kgdb_registration_lock);
  78
  79 /* Action for the reboot notifiter, a global allow kdb to change it */
  80 static int kgdbreboot;
  81 /* kgdb console driver is loaded */
  82 static int kgdb_con_registered;
  83 /* determine if kgdb console output should be used */
  84 static int kgdb_use_con;
  85 /* Flag for alternate operations for early debugging */
  86 bool dbg_is_early = true;
  87 /* Next cpu to become the master debug core */
  88 int dbg_switch_cpu;
  89
  90 /* Use kdb or gdbserver mode */
  91 int dbg_kdb_mode = 1;
  92
  93 static int __init opt_kgdb_con(char *str)
  94 {
  95         kgdb_use_con = 1;
  96         return 0;
  97 }
  98
  99 early_param("kgdbcon", opt_kgdb_con);
 100
 101 module_param(kgdb_use_con, int, 0644);
 102 module_param(kgdbreboot, int, 0644);
 103
 104 /*
 105  * Holds information about breakpoints in a kernel. These breakpoints are
 106  * added and removed by gdb.
 107  */
 108 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
 109         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
 110 };
 111
 112 /*
 113  * The CPU# of the active CPU, or -1 if none:
 114  */
 115 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 116 EXPORT_SYMBOL_GPL(kgdb_active);
 117 static DEFINE_RAW_SPINLOCK(dbg_master_lock);
 118 static DEFINE_RAW_SPINLOCK(dbg_slave_lock);
 119
 120 /*
 121  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 122  * bootup code (which might not have percpu set up yet):
 123  */
 124 static atomic_t                 masters_in_kgdb;
 125 static atomic_t                 slaves_in_kgdb;
 126 static atomic_t                 kgdb_break_tasklet_var;
 127 atomic_t                        kgdb_setting_breakpoint;
 128
 129 struct task_struct              *kgdb_usethread;
 130 struct task_struct              *kgdb_contthread;
 131
 132 int                             kgdb_single_step;
 133 static pid_t                    kgdb_sstep_pid;
 134
 135 /* to keep track of the CPU which is doing the single stepping*/
 136 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 137
 138 /*
 139  * If you are debugging a problem where roundup (the collection of
 140  * all other CPUs) is a problem [this should be extremely rare],
 141  * then use the nokgdbroundup option to avoid roundup. In that case
 142  * the other CPUs might interfere with your debugging context, so
 143  * use this with care:
 144  */
 145 static int kgdb_do_roundup = 1;
 146
 147 static int __init opt_nokgdbroundup(char *str)
 148 {
 149         kgdb_do_roundup = 0;
 150
 151         return 0;
 152 }
 153
 154 early_param("nokgdbroundup", opt_nokgdbroundup);
 155
 156 /*
 157  * Finally, some KGDB code :-)
 158  */
 159
 160 /*
 161  * Weak aliases for breakpoint management,
 162  * can be overriden by architectures when needed:
 163  */
 164 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 165 {
 166         int err;
 167
 168         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
 169         if (err)
 170                 return err;
 171
 172         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
 173                                   BREAK_INSTR_SIZE);
 174 }
 175
 176 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 177 {
 178         return probe_kernel_write((char *)addr,
 179                                   (char *)bundle, BREAK_INSTR_SIZE);
 180 }
 181
 182 int __weak kgdb_validate_break_address(unsigned long addr)
 183 {
 184         char tmp_variable[BREAK_INSTR_SIZE];
 185         int err;
 186         /* Validate setting the breakpoint and then removing it.  In the
 187          * remove fails, the kernel needs to emit a bad message because we
 188          * are deep trouble not being able to put things back the way we
 189          * found them.
 190          */
 191         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
 192         if (err)
 193                 return err;
 194         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
 195         if (err)
 196                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 197                    "memory destroyed at: %lx", addr);
 198         return err;
 199 }
 200
 201 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 202 {
 203         return instruction_pointer(regs);
 204 }
 205
 206 int __weak kgdb_arch_init(void)
 207 {
 208         return 0;
 209 }
 210
 211 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 212 {
 213         return 0;
 214 }
 215
 216 /*
 217  * Some architectures need cache flushes when we set/clear a
 218  * breakpoint:
 219  */
 220 static void kgdb_flush_swbreak_addr(unsigned long addr)
 221 {
 222         if (!CACHE_FLUSH_IS_SAFE)
 223                 return;
 224
 225         if (current->mm && current->mm->mmap_cache) {
 226                 flush_cache_range(current->mm->mmap_cache,
 227                                   addr, addr + BREAK_INSTR_SIZE);
 228         }
 229         /* Force flush instruction cache if it was outside the mm */
 230         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 231 }
 232
 233 /*
 234  * SW breakpoint management:
 235  */
 236 int dbg_activate_sw_breakpoints(void)
 237 {
 238         unsigned long addr;
 239         int error;
 240         int ret = 0;
 241         int i;
 242
 243         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 244                 if (kgdb_break[i].state != BP_SET)
 245                         continue;
 246
 247                 addr = kgdb_break[i].bpt_addr;
 248                 error = kgdb_arch_set_breakpoint(addr,
 249                                 kgdb_break[i].saved_instr);
 250                 if (error) {
 251                         ret = error;
 252                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
 253                         continue;
 254                 }
 255
 256                 kgdb_flush_swbreak_addr(addr);
 257                 kgdb_break[i].state = BP_ACTIVE;
 258         }
 259         return ret;
 260 }
 261
 262 int dbg_set_sw_break(unsigned long addr)
 263 {
 264         int err = kgdb_validate_break_address(addr);
 265         int breakno = -1;
 266         int i;
 267
 268         if (err)
 269                 return err;
 270
 271         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 272                 if ((kgdb_break[i].state == BP_SET) &&
 273                                         (kgdb_break[i].bpt_addr == addr))
 274                         return -EEXIST;
 275         }
 276         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 277                 if (kgdb_break[i].state == BP_REMOVED &&
 278                                         kgdb_break[i].bpt_addr == addr) {
 279                         breakno = i;
 280                         break;
 281                 }
 282         }
 283
 284         if (breakno == -1) {
 285                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 286                         if (kgdb_break[i].state == BP_UNDEFINED) {
 287                                 breakno = i;
 288                                 break;
 289                         }
 290                 }
 291         }
 292
 293         if (breakno == -1)
 294                 return -E2BIG;
 295
 296         kgdb_break[breakno].state = BP_SET;
 297         kgdb_break[breakno].type = BP_BREAKPOINT;
 298         kgdb_break[breakno].bpt_addr = addr;
 299
 300         return 0;
 301 }
 302
 303 int dbg_deactivate_sw_breakpoints(void)
 304 {
 305         unsigned long addr;
 306         int error;
 307         int ret = 0;
 308         int i;
 309
 310         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 311                 if (kgdb_break[i].state != BP_ACTIVE)
 312                         continue;
 313                 addr = kgdb_break[i].bpt_addr;
 314                 error = kgdb_arch_remove_breakpoint(addr,
 315                                         kgdb_break[i].saved_instr);
 316                 if (error) {
 317                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
 318                         ret = error;
 319                 }
 320
 321                 kgdb_flush_swbreak_addr(addr);
 322                 kgdb_break[i].state = BP_SET;
 323         }
 324         return ret;
 325 }
 326
 327 int dbg_remove_sw_break(unsigned long addr)
 328 {
 329         int i;
 330
 331         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 332                 if ((kgdb_break[i].state == BP_SET) &&
 333                                 (kgdb_break[i].bpt_addr == addr)) {
 334                         kgdb_break[i].state = BP_REMOVED;
 335                         return 0;
 336                 }
 337         }
 338         return -ENOENT;
 339 }
 340
 341 int kgdb_isremovedbreak(unsigned long addr)
 342 {
 343         int i;
 344
 345         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 346                 if ((kgdb_break[i].state == BP_REMOVED) &&
 347                                         (kgdb_break[i].bpt_addr == addr))
 348                         return 1;
 349         }
 350         return 0;
 351 }
 352
 353 int dbg_remove_all_break(void)
 354 {
 355         unsigned long addr;
 356         int error;
 357         int i;
 358
 359         /* Clear memory breakpoints. */
 360         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 361                 if (kgdb_break[i].state != BP_ACTIVE)
 362                         goto setundefined;
 363                 addr = kgdb_break[i].bpt_addr;
 364                 error = kgdb_arch_remove_breakpoint(addr,
 365                                 kgdb_break[i].saved_instr);
 366                 if (error)
 367                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 368                            addr);
 369 setundefined:
 370                 kgdb_break[i].state = BP_UNDEFINED;
 371         }
 372
 373         /* Clear hardware breakpoints. */
 374         if (arch_kgdb_ops.remove_all_hw_break)
 375                 arch_kgdb_ops.remove_all_hw_break();
 376
 377         return 0;
 378 }
 379
 380 /*
 381  * Return true if there is a valid kgdb I/O module.  Also if no
 382  * debugger is attached a message can be printed to the console about
 383  * waiting for the debugger to attach.
 384  *
 385  * The print_wait argument is only to be true when called from inside
 386  * the core kgdb_handle_exception, because it will wait for the
 387  * debugger to attach.
 388  */
 389 static int kgdb_io_ready(int print_wait)
 390 {
 391         if (!dbg_io_ops)
 392                 return 0;
 393         if (kgdb_connected)
 394                 return 1;
 395         if (atomic_read(&kgdb_setting_breakpoint))
 396                 return 1;
 397         if (print_wait) {
 398 #ifdef CONFIG_KGDB_KDB
 399                 if (!dbg_kdb_mode)
 400                         printk(KERN_CRIT "KGDB: waiting... or $3#33 for KDB\n");
 401 #else
 402                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 403 #endif
 404         }
 405         return 1;
 406 }
 407
 408 static int kgdb_reenter_check(struct kgdb_state *ks)
 409 {
 410         unsigned long addr;
 411
 412         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 413                 return 0;
 414
 415         /* Panic on recursive debugger calls: */
 416         exception_level++;
 417         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 418         dbg_deactivate_sw_breakpoints();
 419
 420         /*
 421          * If the break point removed ok at the place exception
 422          * occurred, try to recover and print a warning to the end
 423          * user because the user planted a breakpoint in a place that
 424          * KGDB needs in order to function.
 425          */
 426         if (dbg_remove_sw_break(addr) == 0) {
 427                 exception_level = 0;
 428                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 429                 dbg_activate_sw_breakpoints();
 430                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 431                         addr);
 432                 WARN_ON_ONCE(1);
 433
 434                 return 1;
 435         }
 436         dbg_remove_all_break();
 437         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 438
 439         if (exception_level > 1) {
 440                 dump_stack();
 441                 panic("Recursive entry to debugger");
 442         }
 443
 444         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 445 #ifdef CONFIG_KGDB_KDB
 446         /* Allow kdb to debug itself one level */
 447         return 0;
 448 #endif
 449         dump_stack();
 450         panic("Recursive entry to debugger");
 451
 452         return 1;
 453 }
 454
 455 static void dbg_touch_watchdogs(void)
 456 {
 457         touch_softlockup_watchdog_sync();
 458         clocksource_touch_watchdog();
 459         rcu_cpu_stall_reset();
 460 }
 461
 462 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 463                 int exception_state)
 464 {
 465         unsigned long flags;
 466         int sstep_tries = 100;
 467         int error;
 468         int cpu;
 469         int trace_on = 0;
 470         int online_cpus = num_online_cpus();
 471
 472         kgdb_info[ks->cpu].enter_kgdb++;
 473         kgdb_info[ks->cpu].exception_state |= exception_state;
 474
 475         if (exception_state == DCPU_WANT_MASTER)
 476                 atomic_inc(&masters_in_kgdb);
 477         else
 478                 atomic_inc(&slaves_in_kgdb);
 479
 480         if (arch_kgdb_ops.disable_hw_break)
 481                 arch_kgdb_ops.disable_hw_break(regs);
 482
 483 acquirelock:
 484         /*
 485          * Interrupts will be restored by the 'trap return' code, except when
 486          * single stepping.
 487          */
 488         local_irq_save(flags);
 489
 490         cpu = ks->cpu;
 491         kgdb_info[cpu].debuggerinfo = regs;
 492         kgdb_info[cpu].task = current;
 493         kgdb_info[cpu].ret_state = 0;
 494         kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT;
 495
 496         /* Make sure the above info reaches the primary CPU */
 497         smp_mb();
 498
 499         if (exception_level == 1) {
 500                 if (raw_spin_trylock(&dbg_master_lock))
 501                         atomic_xchg(&kgdb_active, cpu);
 502                 goto cpu_master_loop;
 503         }
 504
 505         /*
 506          * CPU will loop if it is a slave or request to become a kgdb
 507          * master cpu and acquire the kgdb_active lock:
 508          */
 509         while (1) {
 510 cpu_loop:
 511                 if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) {
 512                         kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER;
 513                         goto cpu_master_loop;
 514                 } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 515                         if (raw_spin_trylock(&dbg_master_lock)) {
 516                                 atomic_xchg(&kgdb_active, cpu);
 517                                 break;
 518                         }
 519                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 520                         if (!raw_spin_is_locked(&dbg_slave_lock))
 521                                 goto return_normal;
 522                 } else {
 523 return_normal:
 524                         /* Return to normal operation by executing any
 525                          * hw breakpoint fixup.
 526                          */
 527                         if (arch_kgdb_ops.correct_hw_break)
 528                                 arch_kgdb_ops.correct_hw_break();
 529                         if (trace_on)
 530                                 tracing_on();
 531                         kgdb_info[cpu].exception_state &=
 532                                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 533                         kgdb_info[cpu].enter_kgdb--;
 534                         smp_mb__before_atomic_dec();
 535                         atomic_dec(&slaves_in_kgdb);
 536                         dbg_touch_watchdogs();
 537                         local_irq_restore(flags);
 538                         return 0;
 539                 }
 540                 cpu_relax();
 541         }
 542
 543         /*
 544          * For single stepping, try to only enter on the processor
 545          * that was single stepping.  To guard against a deadlock, the
 546          * kernel will only try for the value of sstep_tries before
 547          * giving up and continuing on.
 548          */
 549         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 550             (kgdb_info[cpu].task &&
 551              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 552                 atomic_set(&kgdb_active, -1);
 553                 raw_spin_unlock(&dbg_master_lock);
 554                 dbg_touch_watchdogs();
 555                 local_irq_restore(flags);
 556
 557                 goto acquirelock;
 558         }
 559
 560         if (!kgdb_io_ready(1)) {
 561                 kgdb_info[cpu].ret_state = 1;
 562                 goto kgdb_restore; /* No I/O connection, resume the system */
 563         }
 564
 565         /*
 566          * Don't enter if we have hit a removed breakpoint.
 567          */
 568         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 569                 goto kgdb_restore;
 570
 571         /* Call the I/O driver's pre_exception routine */
 572         if (dbg_io_ops->pre_exception)
 573                 dbg_io_ops->pre_exception();
 574
 575         /*
 576          * Get the passive CPU lock which will hold all the non-primary
 577          * CPU in a spin state while the debugger is active
 578          */
 579         if (!kgdb_single_step)
 580                 raw_spin_lock(&dbg_slave_lock);
 581
 582 #ifdef CONFIG_SMP
 583         /* Signal the other CPUs to enter kgdb_wait() */
 584         if ((!kgdb_single_step) && kgdb_do_roundup)
 585                 kgdb_roundup_cpus(flags);
 586 #endif
 587
 588         /*
 589          * Wait for the other CPUs to be notified and be waiting for us:
 590          */
 591         while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) +
 592                                 atomic_read(&slaves_in_kgdb)) != online_cpus)
 593                 cpu_relax();
 594
 595         /*
 596          * At this point the primary processor is completely
 597          * in the debugger and all secondary CPUs are quiescent
 598          */
 599         dbg_deactivate_sw_breakpoints();
 600         kgdb_single_step = 0;
 601         kgdb_contthread = current;
 602         exception_level = 0;
 603         trace_on = tracing_is_on();
 604         if (trace_on)
 605                 tracing_off();
 606
 607         while (1) {
 608 cpu_master_loop:
 609                 if (dbg_kdb_mode) {
 610                         kgdb_connected = 1;
 611                         error = kdb_stub(ks);
 612                         if (error == -1)
 613                                 continue;
 614                         kgdb_connected = 0;
 615                 } else {
 616                         error = gdb_serial_stub(ks);
 617                 }
 618
 619                 if (error == DBG_PASS_EVENT) {
 620                         dbg_kdb_mode = !dbg_kdb_mode;
 621                 } else if (error == DBG_SWITCH_CPU_EVENT) {
 622                         kgdb_info[dbg_switch_cpu].exception_state |=
 623                                 DCPU_NEXT_MASTER;
 624                         goto cpu_loop;
 625                 } else {
 626                         kgdb_info[cpu].ret_state = error;
 627                         break;
 628                 }
 629         }
 630
 631         /* Call the I/O driver's post_exception routine */
 632         if (dbg_io_ops->post_exception)
 633                 dbg_io_ops->post_exception();
 634
 635         if (!kgdb_single_step) {
 636                 raw_spin_unlock(&dbg_slave_lock);
 637                 /* Wait till all the CPUs have quit from the debugger. */
 638                 while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb))
 639                         cpu_relax();
 640         }
 641
 642 kgdb_restore:
 643         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 644                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 645                 if (kgdb_info[sstep_cpu].task)
 646                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 647                 else
 648                         kgdb_sstep_pid = 0;
 649         }
 650         if (arch_kgdb_ops.correct_hw_break)
 651                 arch_kgdb_ops.correct_hw_break();
 652         if (trace_on)
 653                 tracing_on();
 654
 655         kgdb_info[cpu].exception_state &=
 656                 ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
 657         kgdb_info[cpu].enter_kgdb--;
 658         smp_mb__before_atomic_dec();
 659         atomic_dec(&masters_in_kgdb);
 660         /* Free kgdb_active */
 661         atomic_set(&kgdb_active, -1);
 662         raw_spin_unlock(&dbg_master_lock);
 663         dbg_touch_watchdogs();
 664         local_irq_restore(flags);
 665
 666         return kgdb_info[cpu].ret_state;
 667 }
 668
 669 /*
 670  * kgdb_handle_exception() - main entry point from a kernel exception
 671  *
 672  * Locking hierarchy:
 673  *      interface locks, if any (begin_session)
 674  *      kgdb lock (kgdb_active)
 675  */
 676 int
 677 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 678 {
 679         struct kgdb_state kgdb_var;
 680         struct kgdb_state *ks = &kgdb_var;
 681
 682         ks->cpu                 = raw_smp_processor_id();
 683         ks->ex_vector           = evector;
 684         ks->signo               = signo;
 685         ks->err_code            = ecode;
 686         ks->kgdb_usethreadid    = 0;
 687         ks->linux_regs          = regs;
 688
 689         if (kgdb_reenter_check(ks))
 690                 return 0; /* Ouch, double exception ! */
 691         if (kgdb_info[ks->cpu].enter_kgdb != 0)
 692                 return 0;
 693
 694         return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
 695 }
 696
 697 int kgdb_nmicallback(int cpu, void *regs)
 698 {
 699 #ifdef CONFIG_SMP
 700         struct kgdb_state kgdb_var;
 701         struct kgdb_state *ks = &kgdb_var;
 702
 703         memset(ks, 0, sizeof(struct kgdb_state));
 704         ks->cpu                 = cpu;
 705         ks->linux_regs          = regs;
 706
 707         if (kgdb_info[ks->cpu].enter_kgdb == 0 &&
 708                         raw_spin_is_locked(&dbg_master_lock)) {
 709                 kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE);
 710                 return 0;
 711         }
 712 #endif
 713         return 1;
 714 }
 715
 716 static void kgdb_console_write(struct console *co, const char *s,
 717    unsigned count)
 718 {
 719         unsigned long flags;
 720
 721         /* If we're debugging, or KGDB has not connected, don't try
 722          * and print. */
 723         if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode)
 724                 return;
 725
 726         local_irq_save(flags);
 727         gdbstub_msg_write(s, count);
 728         local_irq_restore(flags);
 729 }
 730
 731 static struct console kgdbcons = {
 732         .name           = "kgdb",
 733         .write          = kgdb_console_write,
 734         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 735         .index          = -1,
 736 };
 737
 738 #ifdef CONFIG_MAGIC_SYSRQ
 739 static void sysrq_handle_dbg(int key)
 740 {
 741         if (!dbg_io_ops) {
 742                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
 743                 return;
 744         }
 745         if (!kgdb_connected) {
 746 #ifdef CONFIG_KGDB_KDB
 747                 if (!dbg_kdb_mode)
 748                         printk(KERN_CRIT "KGDB or $3#33 for KDB\n");
 749 #else
 750                 printk(KERN_CRIT "Entering KGDB\n");
 751 #endif
 752         }
 753
 754         kgdb_breakpoint();
 755 }
 756
 757 static struct sysrq_key_op sysrq_dbg_op = {
 758         .handler        = sysrq_handle_dbg,
 759         .help_msg       = "debug(G)",
 760         .action_msg     = "DEBUG",
 761 };
 762 #endif
 763
 764 static int kgdb_panic_event(struct notifier_block *self,
 765                             unsigned long val,
 766                             void *data)
 767 {
 768         if (dbg_kdb_mode)
 769                 kdb_printf("PANIC: %s\n", (char *)data);
 770         kgdb_breakpoint();
 771         return NOTIFY_DONE;
 772 }
 773
 774 static struct notifier_block kgdb_panic_event_nb = {
 775        .notifier_call   = kgdb_panic_event,
 776        .priority        = INT_MAX,
 777 };
 778
 779 void __weak kgdb_arch_late(void)
 780 {
 781 }
 782
 783 void __init dbg_late_init(void)
 784 {
 785         dbg_is_early = false;
 786         if (kgdb_io_module_registered)
 787                 kgdb_arch_late();
 788         kdb_init(KDB_INIT_FULL);
 789 }
 790
 791 static int
 792 dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x)
 793 {
 794         /*
 795          * Take the following action on reboot notify depending on value:
 796          *    1 == Enter debugger
 797          *    0 == [the default] detatch debug client
 798          *   -1 == Do nothing... and use this until the board resets
 799          */
 800         switch (kgdbreboot) {
 801         case 1:
 802                 kgdb_breakpoint();
 803         case -1:
 804                 goto done;
 805         }
 806         if (!dbg_kdb_mode)
 807                 gdbstub_exit(code);
 808 done:
 809         return NOTIFY_DONE;
 810 }
 811
 812 static struct notifier_block dbg_reboot_notifier = {
 813         .notifier_call          = dbg_notify_reboot,
 814         .next                   = NULL,
 815         .priority               = INT_MAX,
 816 };
 817
 818 static void kgdb_register_callbacks(void)
 819 {
 820         if (!kgdb_io_module_registered) {
 821                 kgdb_io_module_registered = 1;
 822                 kgdb_arch_init();
 823                 if (!dbg_is_early)
 824                         kgdb_arch_late();
 825                 register_reboot_notifier(&dbg_reboot_notifier);
 826                 atomic_notifier_chain_register(&panic_notifier_list,
 827                                                &kgdb_panic_event_nb);
 828 #ifdef CONFIG_MAGIC_SYSRQ
 829                 register_sysrq_key('g', &sysrq_dbg_op);
 830 #endif
 831                 if (kgdb_use_con && !kgdb_con_registered) {
 832                         register_console(&kgdbcons);
 833                         kgdb_con_registered = 1;
 834                 }
 835         }
 836 }
 837
 838 static void kgdb_unregister_callbacks(void)
 839 {
 840         /*
 841          * When this routine is called KGDB should unregister from the
 842          * panic handler and clean up, making sure it is not handling any
 843          * break exceptions at the time.
 844          */
 845         if (kgdb_io_module_registered) {
 846                 kgdb_io_module_registered = 0;
 847                 unregister_reboot_notifier(&dbg_reboot_notifier);
 848                 atomic_notifier_chain_unregister(&panic_notifier_list,
 849                                                &kgdb_panic_event_nb);
 850                 kgdb_arch_exit();
 851 #ifdef CONFIG_MAGIC_SYSRQ
 852                 unregister_sysrq_key('g', &sysrq_dbg_op);
 853 #endif
 854                 if (kgdb_con_registered) {
 855                         unregister_console(&kgdbcons);
 856                         kgdb_con_registered = 0;
 857                 }
 858         }
 859 }
 860
 861 /*
 862  * There are times a tasklet needs to be used vs a compiled in
 863  * break point so as to cause an exception outside a kgdb I/O module,
 864  * such as is the case with kgdboe, where calling a breakpoint in the
 865  * I/O driver itself would be fatal.
 866  */
 867 static void kgdb_tasklet_bpt(unsigned long ing)
 868 {
 869         kgdb_breakpoint();
 870         atomic_set(&kgdb_break_tasklet_var, 0);
 871 }
 872
 873 static DECLARE_TASKLET(kgdb_tasklet_breakpoint, kgdb_tasklet_bpt, 0);
 874
 875 void kgdb_schedule_breakpoint(void)
 876 {
 877         if (atomic_read(&kgdb_break_tasklet_var) ||
 878                 atomic_read(&kgdb_active) != -1 ||
 879                 atomic_read(&kgdb_setting_breakpoint))
 880                 return;
 881         atomic_inc(&kgdb_break_tasklet_var);
 882         tasklet_schedule(&kgdb_tasklet_breakpoint);
 883 }
 884 EXPORT_SYMBOL_GPL(kgdb_schedule_breakpoint);
 885
 886 static void kgdb_initial_breakpoint(void)
 887 {
 888         kgdb_break_asap = 0;
 889
 890         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 891         kgdb_breakpoint();
 892 }
 893
 894 /**
 895  *      kgdb_register_io_module - register KGDB IO module
 896  *      @new_dbg_io_ops: the io ops vector
 897  *
 898  *      Register it with the KGDB core.
 899  */
 900 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 901 {
 902         int err;
 903
 904         spin_lock(&kgdb_registration_lock);
 905
 906         if (dbg_io_ops) {
 907                 spin_unlock(&kgdb_registration_lock);
 908
 909                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 910                                 "registered with KGDB.\n");
 911                 return -EBUSY;
 912         }
 913
 914         if (new_dbg_io_ops->init) {
 915                 err = new_dbg_io_ops->init();
 916                 if (err) {
 917                         spin_unlock(&kgdb_registration_lock);
 918                         return err;
 919                 }
 920         }
 921
 922         dbg_io_ops = new_dbg_io_ops;
 923
 924         spin_unlock(&kgdb_registration_lock);
 925
 926         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 927                new_dbg_io_ops->name);
 928
 929         /* Arm KGDB now. */
 930         kgdb_register_callbacks();
 931
 932         if (kgdb_break_asap)
 933                 kgdb_initial_breakpoint();
 934
 935         return 0;
 936 }
 937 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 938
 939 /**
 940  *      kkgdb_unregister_io_module - unregister KGDB IO module
 941  *      @old_dbg_io_ops: the io ops vector
 942  *
 943  *      Unregister it with the KGDB core.
 944  */
 945 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 946 {
 947         BUG_ON(kgdb_connected);
 948
 949         /*
 950          * KGDB is no longer able to communicate out, so
 951          * unregister our callbacks and reset state.
 952          */
 953         kgdb_unregister_callbacks();
 954
 955         spin_lock(&kgdb_registration_lock);
 956
 957         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 958         dbg_io_ops = NULL;
 959
 960         spin_unlock(&kgdb_registration_lock);
 961
 962         printk(KERN_INFO
 963                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 964                 old_dbg_io_ops->name);
 965 }
 966 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 967
 968 int dbg_io_get_char(void)
 969 {
 970         int ret = dbg_io_ops->read_char();
 971         if (ret == NO_POLL_CHAR)
 972                 return -1;
 973         if (!dbg_kdb_mode)
 974                 return ret;
 975         if (ret == 127)
 976                 return 8;
 977         return ret;
 978 }
 979
 980 /**
 981  * kgdb_breakpoint - generate breakpoint exception
 982  *
 983  * This function will generate a breakpoint exception.  It is used at the
 984  * beginning of a program to sync up with a debugger and can be used
 985  * otherwise as a quick means to stop program execution and "break" into
 986  * the debugger.
 987  */
 988 void kgdb_breakpoint(void)
 989 {
 990         atomic_inc(&kgdb_setting_breakpoint);
 991         wmb(); /* Sync point before breakpoint */
 992         arch_kgdb_breakpoint();
 993         wmb(); /* Sync point after breakpoint */
 994         atomic_dec(&kgdb_setting_breakpoint);
 995 }
 996 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
 997
 998 static int __init opt_kgdb_wait(char *str)
 999 {
1000         kgdb_break_asap = 1;
1001
1002         kdb_init(KDB_INIT_EARLY);
1003         if (kgdb_io_module_registered)
1004                 kgdb_initial_breakpoint();
1005
1006         return 0;
1007 }
1008
1009 early_param("kgdbwait", opt_kgdb_wait);