SAFE public projects git trees. - safe/jmp/linux-2.6/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@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) 2005-2009 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/init.h>
  45 #include <linux/kgdb.h>
  46 #include <linux/pid.h>
  47 #include <linux/smp.h>
  48 #include <linux/mm.h>
  49
  50 #include <asm/cacheflush.h>
  51 #include <asm/byteorder.h>
  52 #include <asm/atomic.h>
  53 #include <asm/system.h>
  54
  55 #include "debug_core.h"
  56
  57 static int kgdb_break_asap;
  58
  59 struct debuggerinfo_struct kgdb_info[NR_CPUS];
  60
  61 /**
  62  * kgdb_connected - Is a host GDB connected to us?
  63  */
  64 int                             kgdb_connected;
  65 EXPORT_SYMBOL_GPL(kgdb_connected);
  66
  67 /* All the KGDB handlers are installed */
  68 static int                      kgdb_io_module_registered;
  69
  70 /* Guard for recursive entry */
  71 static int                      exception_level;
  72
  73 struct kgdb_io          *dbg_io_ops;
  74 static DEFINE_SPINLOCK(kgdb_registration_lock);
  75
  76 /* kgdb console driver is loaded */
  77 static int kgdb_con_registered;
  78 /* determine if kgdb console output should be used */
  79 static int kgdb_use_con;
  80
  81 static int __init opt_kgdb_con(char *str)
  82 {
  83         kgdb_use_con = 1;
  84         return 0;
  85 }
  86
  87 early_param("kgdbcon", opt_kgdb_con);
  88
  89 module_param(kgdb_use_con, int, 0644);
  90
  91 /*
  92  * Holds information about breakpoints in a kernel. These breakpoints are
  93  * added and removed by gdb.
  94  */
  95 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
  96         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
  97 };
  98
  99 /*
 100  * The CPU# of the active CPU, or -1 if none:
 101  */
 102 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
 103
 104 /*
 105  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
 106  * bootup code (which might not have percpu set up yet):
 107  */
 108 static atomic_t                 passive_cpu_wait[NR_CPUS];
 109 static atomic_t                 cpu_in_kgdb[NR_CPUS];
 110 atomic_t                        kgdb_setting_breakpoint;
 111
 112 struct task_struct              *kgdb_usethread;
 113 struct task_struct              *kgdb_contthread;
 114
 115 int                             kgdb_single_step;
 116 static pid_t                    kgdb_sstep_pid;
 117
 118 /* to keep track of the CPU which is doing the single stepping*/
 119 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
 120
 121 /*
 122  * If you are debugging a problem where roundup (the collection of
 123  * all other CPUs) is a problem [this should be extremely rare],
 124  * then use the nokgdbroundup option to avoid roundup. In that case
 125  * the other CPUs might interfere with your debugging context, so
 126  * use this with care:
 127  */
 128 static int kgdb_do_roundup = 1;
 129
 130 static int __init opt_nokgdbroundup(char *str)
 131 {
 132         kgdb_do_roundup = 0;
 133
 134         return 0;
 135 }
 136
 137 early_param("nokgdbroundup", opt_nokgdbroundup);
 138
 139 /*
 140  * Finally, some KGDB code :-)
 141  */
 142
 143 /*
 144  * Weak aliases for breakpoint management,
 145  * can be overriden by architectures when needed:
 146  */
 147 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 148 {
 149         int err;
 150
 151         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
 152         if (err)
 153                 return err;
 154
 155         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
 156                                   BREAK_INSTR_SIZE);
 157 }
 158
 159 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 160 {
 161         return probe_kernel_write((char *)addr,
 162                                   (char *)bundle, BREAK_INSTR_SIZE);
 163 }
 164
 165 int __weak kgdb_validate_break_address(unsigned long addr)
 166 {
 167         char tmp_variable[BREAK_INSTR_SIZE];
 168         int err;
 169         /* Validate setting the breakpoint and then removing it.  In the
 170          * remove fails, the kernel needs to emit a bad message because we
 171          * are deep trouble not being able to put things back the way we
 172          * found them.
 173          */
 174         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
 175         if (err)
 176                 return err;
 177         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
 178         if (err)
 179                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
 180                    "memory destroyed at: %lx", addr);
 181         return err;
 182 }
 183
 184 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 185 {
 186         return instruction_pointer(regs);
 187 }
 188
 189 int __weak kgdb_arch_init(void)
 190 {
 191         return 0;
 192 }
 193
 194 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
 195 {
 196         return 0;
 197 }
 198
 199 void __weak
 200 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
 201 {
 202         return;
 203 }
 204
 205 /**
 206  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 207  *      @regs: Current &struct pt_regs.
 208  *
 209  *      This function will be called if the particular architecture must
 210  *      disable hardware debugging while it is processing gdb packets or
 211  *      handling exception.
 212  */
 213 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
 214 {
 215 }
 216
 217 /*
 218  * Some architectures need cache flushes when we set/clear a
 219  * breakpoint:
 220  */
 221 static void kgdb_flush_swbreak_addr(unsigned long addr)
 222 {
 223         if (!CACHE_FLUSH_IS_SAFE)
 224                 return;
 225
 226         if (current->mm && current->mm->mmap_cache) {
 227                 flush_cache_range(current->mm->mmap_cache,
 228                                   addr, addr + BREAK_INSTR_SIZE);
 229         }
 230         /* Force flush instruction cache if it was outside the mm */
 231         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 232 }
 233
 234 /*
 235  * SW breakpoint management:
 236  */
 237 int dbg_activate_sw_breakpoints(void)
 238 {
 239         unsigned long addr;
 240         int error;
 241         int ret = 0;
 242         int i;
 243
 244         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 245                 if (kgdb_break[i].state != BP_SET)
 246                         continue;
 247
 248                 addr = kgdb_break[i].bpt_addr;
 249                 error = kgdb_arch_set_breakpoint(addr,
 250                                 kgdb_break[i].saved_instr);
 251                 if (error) {
 252                         ret = error;
 253                         printk(KERN_INFO "KGDB: BP install failed: %lx", addr);
 254                         continue;
 255                 }
 256
 257                 kgdb_flush_swbreak_addr(addr);
 258                 kgdb_break[i].state = BP_ACTIVE;
 259         }
 260         return ret;
 261 }
 262
 263 int dbg_set_sw_break(unsigned long addr)
 264 {
 265         int err = kgdb_validate_break_address(addr);
 266         int breakno = -1;
 267         int i;
 268
 269         if (err)
 270                 return err;
 271
 272         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 273                 if ((kgdb_break[i].state == BP_SET) &&
 274                                         (kgdb_break[i].bpt_addr == addr))
 275                         return -EEXIST;
 276         }
 277         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 278                 if (kgdb_break[i].state == BP_REMOVED &&
 279                                         kgdb_break[i].bpt_addr == addr) {
 280                         breakno = i;
 281                         break;
 282                 }
 283         }
 284
 285         if (breakno == -1) {
 286                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 287                         if (kgdb_break[i].state == BP_UNDEFINED) {
 288                                 breakno = i;
 289                                 break;
 290                         }
 291                 }
 292         }
 293
 294         if (breakno == -1)
 295                 return -E2BIG;
 296
 297         kgdb_break[breakno].state = BP_SET;
 298         kgdb_break[breakno].type = BP_BREAKPOINT;
 299         kgdb_break[breakno].bpt_addr = addr;
 300
 301         return 0;
 302 }
 303
 304 static int kgdb_deactivate_sw_breakpoints(void)
 305 {
 306         unsigned long addr;
 307         int error;
 308         int ret = 0;
 309         int i;
 310
 311         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 312                 if (kgdb_break[i].state != BP_ACTIVE)
 313                         continue;
 314                 addr = kgdb_break[i].bpt_addr;
 315                 error = kgdb_arch_remove_breakpoint(addr,
 316                                         kgdb_break[i].saved_instr);
 317                 if (error) {
 318                         printk(KERN_INFO "KGDB: BP remove failed: %lx\n", addr);
 319                         ret = error;
 320                 }
 321
 322                 kgdb_flush_swbreak_addr(addr);
 323                 kgdb_break[i].state = BP_SET;
 324         }
 325         return ret;
 326 }
 327
 328 int dbg_remove_sw_break(unsigned long addr)
 329 {
 330         int i;
 331
 332         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 333                 if ((kgdb_break[i].state == BP_SET) &&
 334                                 (kgdb_break[i].bpt_addr == addr)) {
 335                         kgdb_break[i].state = BP_REMOVED;
 336                         return 0;
 337                 }
 338         }
 339         return -ENOENT;
 340 }
 341
 342 int kgdb_isremovedbreak(unsigned long addr)
 343 {
 344         int i;
 345
 346         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 347                 if ((kgdb_break[i].state == BP_REMOVED) &&
 348                                         (kgdb_break[i].bpt_addr == addr))
 349                         return 1;
 350         }
 351         return 0;
 352 }
 353
 354 int dbg_remove_all_break(void)
 355 {
 356         unsigned long addr;
 357         int error;
 358         int i;
 359
 360         /* Clear memory breakpoints. */
 361         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
 362                 if (kgdb_break[i].state != BP_ACTIVE)
 363                         goto setundefined;
 364                 addr = kgdb_break[i].bpt_addr;
 365                 error = kgdb_arch_remove_breakpoint(addr,
 366                                 kgdb_break[i].saved_instr);
 367                 if (error)
 368                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
 369                            addr);
 370 setundefined:
 371                 kgdb_break[i].state = BP_UNDEFINED;
 372         }
 373
 374         /* Clear hardware breakpoints. */
 375         if (arch_kgdb_ops.remove_all_hw_break)
 376                 arch_kgdb_ops.remove_all_hw_break();
 377
 378         return 0;
 379 }
 380
 381 /*
 382  * Return true if there is a valid kgdb I/O module.  Also if no
 383  * debugger is attached a message can be printed to the console about
 384  * waiting for the debugger to attach.
 385  *
 386  * The print_wait argument is only to be true when called from inside
 387  * the core kgdb_handle_exception, because it will wait for the
 388  * debugger to attach.
 389  */
 390 static int kgdb_io_ready(int print_wait)
 391 {
 392         if (!dbg_io_ops)
 393                 return 0;
 394         if (kgdb_connected)
 395                 return 1;
 396         if (atomic_read(&kgdb_setting_breakpoint))
 397                 return 1;
 398         if (print_wait)
 399                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
 400         return 1;
 401 }
 402
 403 static int kgdb_reenter_check(struct kgdb_state *ks)
 404 {
 405         unsigned long addr;
 406
 407         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
 408                 return 0;
 409
 410         /* Panic on recursive debugger calls: */
 411         exception_level++;
 412         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
 413         kgdb_deactivate_sw_breakpoints();
 414
 415         /*
 416          * If the break point removed ok at the place exception
 417          * occurred, try to recover and print a warning to the end
 418          * user because the user planted a breakpoint in a place that
 419          * KGDB needs in order to function.
 420          */
 421         if (dbg_remove_sw_break(addr) == 0) {
 422                 exception_level = 0;
 423                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 424                 dbg_activate_sw_breakpoints();
 425                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
 426                         addr);
 427                 WARN_ON_ONCE(1);
 428
 429                 return 1;
 430         }
 431         dbg_remove_all_break();
 432         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
 433
 434         if (exception_level > 1) {
 435                 dump_stack();
 436                 panic("Recursive entry to debugger");
 437         }
 438
 439         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
 440         dump_stack();
 441         panic("Recursive entry to debugger");
 442
 443         return 1;
 444 }
 445
 446 static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
 447 {
 448         unsigned long flags;
 449         int sstep_tries = 100;
 450         int error = 0;
 451         int i, cpu;
 452         int trace_on = 0;
 453 acquirelock:
 454         /*
 455          * Interrupts will be restored by the 'trap return' code, except when
 456          * single stepping.
 457          */
 458         local_irq_save(flags);
 459
 460         cpu = ks->cpu;
 461         kgdb_info[cpu].debuggerinfo = regs;
 462         kgdb_info[cpu].task = current;
 463         /*
 464          * Make sure the above info reaches the primary CPU before
 465          * our cpu_in_kgdb[] flag setting does:
 466          */
 467         atomic_inc(&cpu_in_kgdb[cpu]);
 468
 469         /*
 470          * CPU will loop if it is a slave or request to become a kgdb
 471          * master cpu and acquire the kgdb_active lock:
 472          */
 473         while (1) {
 474                 if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
 475                         if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
 476                                 break;
 477                 } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
 478                         if (!atomic_read(&passive_cpu_wait[cpu]))
 479                                 goto return_normal;
 480                 } else {
 481 return_normal:
 482                         /* Return to normal operation by executing any
 483                          * hw breakpoint fixup.
 484                          */
 485                         if (arch_kgdb_ops.correct_hw_break)
 486                                 arch_kgdb_ops.correct_hw_break();
 487                         if (trace_on)
 488                                 tracing_on();
 489                         atomic_dec(&cpu_in_kgdb[cpu]);
 490                         touch_softlockup_watchdog_sync();
 491                         clocksource_touch_watchdog();
 492                         local_irq_restore(flags);
 493                         return 0;
 494                 }
 495                 cpu_relax();
 496         }
 497
 498         /*
 499          * For single stepping, try to only enter on the processor
 500          * that was single stepping.  To gaurd against a deadlock, the
 501          * kernel will only try for the value of sstep_tries before
 502          * giving up and continuing on.
 503          */
 504         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
 505             (kgdb_info[cpu].task &&
 506              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
 507                 atomic_set(&kgdb_active, -1);
 508                 touch_softlockup_watchdog_sync();
 509                 clocksource_touch_watchdog();
 510                 local_irq_restore(flags);
 511
 512                 goto acquirelock;
 513         }
 514
 515         if (!kgdb_io_ready(1)) {
 516                 error = 1;
 517                 goto kgdb_restore; /* No I/O connection, resume the system */
 518         }
 519
 520         /*
 521          * Don't enter if we have hit a removed breakpoint.
 522          */
 523         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
 524                 goto kgdb_restore;
 525
 526         /* Call the I/O driver's pre_exception routine */
 527         if (dbg_io_ops->pre_exception)
 528                 dbg_io_ops->pre_exception();
 529
 530         kgdb_disable_hw_debug(ks->linux_regs);
 531
 532         /*
 533          * Get the passive CPU lock which will hold all the non-primary
 534          * CPU in a spin state while the debugger is active
 535          */
 536         if (!kgdb_single_step) {
 537                 for (i = 0; i < NR_CPUS; i++)
 538                         atomic_inc(&passive_cpu_wait[i]);
 539         }
 540
 541 #ifdef CONFIG_SMP
 542         /* Signal the other CPUs to enter kgdb_wait() */
 543         if ((!kgdb_single_step) && kgdb_do_roundup)
 544                 kgdb_roundup_cpus(flags);
 545 #endif
 546
 547         /*
 548          * Wait for the other CPUs to be notified and be waiting for us:
 549          */
 550         for_each_online_cpu(i) {
 551                 while (!atomic_read(&cpu_in_kgdb[i]))
 552                         cpu_relax();
 553         }
 554
 555         /*
 556          * At this point the primary processor is completely
 557          * in the debugger and all secondary CPUs are quiescent
 558          */
 559         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
 560         kgdb_deactivate_sw_breakpoints();
 561         kgdb_single_step = 0;
 562         kgdb_contthread = current;
 563         exception_level = 0;
 564         trace_on = tracing_is_on();
 565         if (trace_on)
 566                 tracing_off();
 567
 568         /* Talk to debugger with gdbserial protocol */
 569         error = gdb_serial_stub(ks);
 570
 571         /* Call the I/O driver's post_exception routine */
 572         if (dbg_io_ops->post_exception)
 573                 dbg_io_ops->post_exception();
 574
 575         atomic_dec(&cpu_in_kgdb[ks->cpu]);
 576
 577         if (!kgdb_single_step) {
 578                 for (i = NR_CPUS-1; i >= 0; i--)
 579                         atomic_dec(&passive_cpu_wait[i]);
 580                 /*
 581                  * Wait till all the CPUs have quit
 582                  * from the debugger.
 583                  */
 584                 for_each_online_cpu(i) {
 585                         while (atomic_read(&cpu_in_kgdb[i]))
 586                                 cpu_relax();
 587                 }
 588         }
 589
 590 kgdb_restore:
 591         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 592                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
 593                 if (kgdb_info[sstep_cpu].task)
 594                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
 595                 else
 596                         kgdb_sstep_pid = 0;
 597         }
 598         if (trace_on)
 599                 tracing_on();
 600         /* Free kgdb_active */
 601         atomic_set(&kgdb_active, -1);
 602         touch_softlockup_watchdog_sync();
 603         clocksource_touch_watchdog();
 604         local_irq_restore(flags);
 605
 606         return error;
 607 }
 608
 609 /*
 610  * kgdb_handle_exception() - main entry point from a kernel exception
 611  *
 612  * Locking hierarchy:
 613  *      interface locks, if any (begin_session)
 614  *      kgdb lock (kgdb_active)
 615  */
 616 int
 617 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
 618 {
 619         struct kgdb_state kgdb_var;
 620         struct kgdb_state *ks = &kgdb_var;
 621         int ret;
 622
 623         ks->cpu                 = raw_smp_processor_id();
 624         ks->ex_vector           = evector;
 625         ks->signo               = signo;
 626         ks->ex_vector           = evector;
 627         ks->err_code            = ecode;
 628         ks->kgdb_usethreadid    = 0;
 629         ks->linux_regs          = regs;
 630
 631         if (kgdb_reenter_check(ks))
 632                 return 0; /* Ouch, double exception ! */
 633         kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
 634         ret = kgdb_cpu_enter(ks, regs);
 635         kgdb_info[ks->cpu].exception_state &= ~DCPU_WANT_MASTER;
 636         return ret;
 637 }
 638
 639 int kgdb_nmicallback(int cpu, void *regs)
 640 {
 641 #ifdef CONFIG_SMP
 642         struct kgdb_state kgdb_var;
 643         struct kgdb_state *ks = &kgdb_var;
 644
 645         memset(ks, 0, sizeof(struct kgdb_state));
 646         ks->cpu                 = cpu;
 647         ks->linux_regs          = regs;
 648
 649         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
 650             atomic_read(&kgdb_active) != -1 &&
 651             atomic_read(&kgdb_active) != cpu) {
 652                 kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
 653                 kgdb_cpu_enter(ks, regs);
 654                 kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
 655                 return 0;
 656         }
 657 #endif
 658         return 1;
 659 }
 660
 661 static void kgdb_console_write(struct console *co, const char *s,
 662    unsigned count)
 663 {
 664         unsigned long flags;
 665
 666         /* If we're debugging, or KGDB has not connected, don't try
 667          * and print. */
 668         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
 669                 return;
 670
 671         local_irq_save(flags);
 672         gdbstub_msg_write(s, count);
 673         local_irq_restore(flags);
 674 }
 675
 676 static struct console kgdbcons = {
 677         .name           = "kgdb",
 678         .write          = kgdb_console_write,
 679         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 680         .index          = -1,
 681 };
 682
 683 #ifdef CONFIG_MAGIC_SYSRQ
 684 static void sysrq_handle_dbg(int key, struct tty_struct *tty)
 685 {
 686         if (!dbg_io_ops) {
 687                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
 688                 return;
 689         }
 690         if (!kgdb_connected)
 691                 printk(KERN_CRIT "Entering KGDB\n");
 692
 693         kgdb_breakpoint();
 694 }
 695
 696 static struct sysrq_key_op sysrq_dbg_op = {
 697         .handler        = sysrq_handle_dbg,
 698         .help_msg       = "debug(G)",
 699         .action_msg     = "DEBUG",
 700 };
 701 #endif
 702
 703 static void kgdb_register_callbacks(void)
 704 {
 705         if (!kgdb_io_module_registered) {
 706                 kgdb_io_module_registered = 1;
 707                 kgdb_arch_init();
 708 #ifdef CONFIG_MAGIC_SYSRQ
 709                 register_sysrq_key('g', &sysrq_dbg_op);
 710 #endif
 711                 if (kgdb_use_con && !kgdb_con_registered) {
 712                         register_console(&kgdbcons);
 713                         kgdb_con_registered = 1;
 714                 }
 715         }
 716 }
 717
 718 static void kgdb_unregister_callbacks(void)
 719 {
 720         /*
 721          * When this routine is called KGDB should unregister from the
 722          * panic handler and clean up, making sure it is not handling any
 723          * break exceptions at the time.
 724          */
 725         if (kgdb_io_module_registered) {
 726                 kgdb_io_module_registered = 0;
 727                 kgdb_arch_exit();
 728 #ifdef CONFIG_MAGIC_SYSRQ
 729                 unregister_sysrq_key('g', &sysrq_dbg_op);
 730 #endif
 731                 if (kgdb_con_registered) {
 732                         unregister_console(&kgdbcons);
 733                         kgdb_con_registered = 0;
 734                 }
 735         }
 736 }
 737
 738 static void kgdb_initial_breakpoint(void)
 739 {
 740         kgdb_break_asap = 0;
 741
 742         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
 743         kgdb_breakpoint();
 744 }
 745
 746 /**
 747  *      kgdb_register_io_module - register KGDB IO module
 748  *      @new_dbg_io_ops: the io ops vector
 749  *
 750  *      Register it with the KGDB core.
 751  */
 752 int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 753 {
 754         int err;
 755
 756         spin_lock(&kgdb_registration_lock);
 757
 758         if (dbg_io_ops) {
 759                 spin_unlock(&kgdb_registration_lock);
 760
 761                 printk(KERN_ERR "kgdb: Another I/O driver is already "
 762                                 "registered with KGDB.\n");
 763                 return -EBUSY;
 764         }
 765
 766         if (new_dbg_io_ops->init) {
 767                 err = new_dbg_io_ops->init();
 768                 if (err) {
 769                         spin_unlock(&kgdb_registration_lock);
 770                         return err;
 771                 }
 772         }
 773
 774         dbg_io_ops = new_dbg_io_ops;
 775
 776         spin_unlock(&kgdb_registration_lock);
 777
 778         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
 779                new_dbg_io_ops->name);
 780
 781         /* Arm KGDB now. */
 782         kgdb_register_callbacks();
 783
 784         if (kgdb_break_asap)
 785                 kgdb_initial_breakpoint();
 786
 787         return 0;
 788 }
 789 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 790
 791 /**
 792  *      kkgdb_unregister_io_module - unregister KGDB IO module
 793  *      @old_dbg_io_ops: the io ops vector
 794  *
 795  *      Unregister it with the KGDB core.
 796  */
 797 void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops)
 798 {
 799         BUG_ON(kgdb_connected);
 800
 801         /*
 802          * KGDB is no longer able to communicate out, so
 803          * unregister our callbacks and reset state.
 804          */
 805         kgdb_unregister_callbacks();
 806
 807         spin_lock(&kgdb_registration_lock);
 808
 809         WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops);
 810         dbg_io_ops = NULL;
 811
 812         spin_unlock(&kgdb_registration_lock);
 813
 814         printk(KERN_INFO
 815                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
 816                 old_dbg_io_ops->name);
 817 }
 818 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
 819
 820 /**
 821  * kgdb_breakpoint - generate breakpoint exception
 822  *
 823  * This function will generate a breakpoint exception.  It is used at the
 824  * beginning of a program to sync up with a debugger and can be used
 825  * otherwise as a quick means to stop program execution and "break" into
 826  * the debugger.
 827  */
 828 void kgdb_breakpoint(void)
 829 {
 830         atomic_inc(&kgdb_setting_breakpoint);
 831         wmb(); /* Sync point before breakpoint */
 832         arch_kgdb_breakpoint();
 833         wmb(); /* Sync point after breakpoint */
 834         atomic_dec(&kgdb_setting_breakpoint);
 835 }
 836 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
 837
 838 static int __init opt_kgdb_wait(char *str)
 839 {
 840         kgdb_break_asap = 1;
 841
 842         if (kgdb_io_module_registered)
 843                 kgdb_initial_breakpoint();
 844
 845         return 0;
 846 }
 847
 848 early_param("kgdbwait", opt_kgdb_wait);