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