arch/x86/kernel/kgdb.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify it
   3  * under the terms of the GNU General Public License as published by the
   4  * Free Software Foundation; either version 2, or (at your option) any
   5  * later version.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  10  * General Public License for more details.
  11  *
  12  */
  13
  14 /*
  15  * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
  16  * Copyright (C) 2000-2001 VERITAS Software Corporation.
  17  * Copyright (C) 2002 Andi Kleen, SuSE Labs
  18  * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
  19  * Copyright (C) 2007 MontaVista Software, Inc.
  20  * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
  21  */
  22 /****************************************************************************
  23  *  Contributor:     Lake Stevens Instrument Division$
  24  *  Written by:      Glenn Engel $
  25  *  Updated by:      Amit Kale<akale@veritas.com>
  26  *  Updated by:      Tom Rini <trini@kernel.crashing.org>
  27  *  Updated by:      Jason Wessel <jason.wessel@windriver.com>
  28  *  Modified for 386 by Jim Kingdon, Cygnus Support.
  29  *  Origianl kgdb, compatibility with 2.1.xx kernel by
  30  *  David Grothe <dave@gcom.com>
  31  *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
  32  *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
  33  */
  34 #include <linux/spinlock.h>
  35 #include <linux/kdebug.h>
  36 #include <linux/string.h>
  37 #include <linux/kernel.h>
  38 #include <linux/ptrace.h>
  39 #include <linux/sched.h>
  40 #include <linux/delay.h>
  41 #include <linux/kgdb.h>
  42 #include <linux/init.h>
  43 #include <linux/smp.h>
  44 #include <linux/nmi.h>
  45 #include <linux/hw_breakpoint.h>
  46
  47 #include <asm/debugreg.h>
  48 #include <asm/apicdef.h>
  49 #include <asm/system.h>
  50 #include <asm/apic.h>
  51
  52 /**
  53  *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
  54  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
  55  *      @regs: The &struct pt_regs of the current process.
  56  *
  57  *      Convert the pt_regs in @regs into the format for registers that
  58  *      GDB expects, stored in @gdb_regs.
  59  */
  60 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
  61 {
  62 #ifndef CONFIG_X86_32
  63         u32 *gdb_regs32 = (u32 *)gdb_regs;
  64 #endif
  65         gdb_regs[GDB_AX]        = regs->ax;
  66         gdb_regs[GDB_BX]        = regs->bx;
  67         gdb_regs[GDB_CX]        = regs->cx;
  68         gdb_regs[GDB_DX]        = regs->dx;
  69         gdb_regs[GDB_SI]        = regs->si;
  70         gdb_regs[GDB_DI]        = regs->di;
  71         gdb_regs[GDB_BP]        = regs->bp;
  72         gdb_regs[GDB_PC]        = regs->ip;
  73 #ifdef CONFIG_X86_32
  74         gdb_regs[GDB_PS]        = regs->flags;
  75         gdb_regs[GDB_DS]        = regs->ds;
  76         gdb_regs[GDB_ES]        = regs->es;
  77         gdb_regs[GDB_CS]        = regs->cs;
  78         gdb_regs[GDB_FS]        = 0xFFFF;
  79         gdb_regs[GDB_GS]        = 0xFFFF;
  80         if (user_mode_vm(regs)) {
  81                 gdb_regs[GDB_SS] = regs->ss;
  82                 gdb_regs[GDB_SP] = regs->sp;
  83         } else {
  84                 gdb_regs[GDB_SS] = __KERNEL_DS;
  85                 gdb_regs[GDB_SP] = kernel_stack_pointer(regs);
  86         }
  87 #else
  88         gdb_regs[GDB_R8]        = regs->r8;
  89         gdb_regs[GDB_R9]        = regs->r9;
  90         gdb_regs[GDB_R10]       = regs->r10;
  91         gdb_regs[GDB_R11]       = regs->r11;
  92         gdb_regs[GDB_R12]       = regs->r12;
  93         gdb_regs[GDB_R13]       = regs->r13;
  94         gdb_regs[GDB_R14]       = regs->r14;
  95         gdb_regs[GDB_R15]       = regs->r15;
  96         gdb_regs32[GDB_PS]      = regs->flags;
  97         gdb_regs32[GDB_CS]      = regs->cs;
  98         gdb_regs32[GDB_SS]      = regs->ss;
  99         gdb_regs[GDB_SP]        = kernel_stack_pointer(regs);
 100 #endif
 101 }
 102
 103 /**
 104  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 105  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 106  *      @p: The &struct task_struct of the desired process.
 107  *
 108  *      Convert the register values of the sleeping process in @p to
 109  *      the format that GDB expects.
 110  *      This function is called when kgdb does not have access to the
 111  *      &struct pt_regs and therefore it should fill the gdb registers
 112  *      @gdb_regs with what has been saved in &struct thread_struct
 113  *      thread field during switch_to.
 114  */
 115 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 116 {
 117 #ifndef CONFIG_X86_32
 118         u32 *gdb_regs32 = (u32 *)gdb_regs;
 119 #endif
 120         gdb_regs[GDB_AX]        = 0;
 121         gdb_regs[GDB_BX]        = 0;
 122         gdb_regs[GDB_CX]        = 0;
 123         gdb_regs[GDB_DX]        = 0;
 124         gdb_regs[GDB_SI]        = 0;
 125         gdb_regs[GDB_DI]        = 0;
 126         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
 127 #ifdef CONFIG_X86_32
 128         gdb_regs[GDB_DS]        = __KERNEL_DS;
 129         gdb_regs[GDB_ES]        = __KERNEL_DS;
 130         gdb_regs[GDB_PS]        = 0;
 131         gdb_regs[GDB_CS]        = __KERNEL_CS;
 132         gdb_regs[GDB_PC]        = p->thread.ip;
 133         gdb_regs[GDB_SS]        = __KERNEL_DS;
 134         gdb_regs[GDB_FS]        = 0xFFFF;
 135         gdb_regs[GDB_GS]        = 0xFFFF;
 136 #else
 137         gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
 138         gdb_regs32[GDB_CS]      = __KERNEL_CS;
 139         gdb_regs32[GDB_SS]      = __KERNEL_DS;
 140         gdb_regs[GDB_PC]        = 0;
 141         gdb_regs[GDB_R8]        = 0;
 142         gdb_regs[GDB_R9]        = 0;
 143         gdb_regs[GDB_R10]       = 0;
 144         gdb_regs[GDB_R11]       = 0;
 145         gdb_regs[GDB_R12]       = 0;
 146         gdb_regs[GDB_R13]       = 0;
 147         gdb_regs[GDB_R14]       = 0;
 148         gdb_regs[GDB_R15]       = 0;
 149 #endif
 150         gdb_regs[GDB_SP]        = p->thread.sp;
 151 }
 152
 153 /**
 154  *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
 155  *      @gdb_regs: A pointer to hold the registers we've received from GDB.
 156  *      @regs: A pointer to a &struct pt_regs to hold these values in.
 157  *
 158  *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
 159  *      in @regs.
 160  */
 161 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 162 {
 163 #ifndef CONFIG_X86_32
 164         u32 *gdb_regs32 = (u32 *)gdb_regs;
 165 #endif
 166         regs->ax                = gdb_regs[GDB_AX];
 167         regs->bx                = gdb_regs[GDB_BX];
 168         regs->cx                = gdb_regs[GDB_CX];
 169         regs->dx                = gdb_regs[GDB_DX];
 170         regs->si                = gdb_regs[GDB_SI];
 171         regs->di                = gdb_regs[GDB_DI];
 172         regs->bp                = gdb_regs[GDB_BP];
 173         regs->ip                = gdb_regs[GDB_PC];
 174 #ifdef CONFIG_X86_32
 175         regs->flags             = gdb_regs[GDB_PS];
 176         regs->ds                = gdb_regs[GDB_DS];
 177         regs->es                = gdb_regs[GDB_ES];
 178         regs->cs                = gdb_regs[GDB_CS];
 179 #else
 180         regs->r8                = gdb_regs[GDB_R8];
 181         regs->r9                = gdb_regs[GDB_R9];
 182         regs->r10               = gdb_regs[GDB_R10];
 183         regs->r11               = gdb_regs[GDB_R11];
 184         regs->r12               = gdb_regs[GDB_R12];
 185         regs->r13               = gdb_regs[GDB_R13];
 186         regs->r14               = gdb_regs[GDB_R14];
 187         regs->r15               = gdb_regs[GDB_R15];
 188         regs->flags             = gdb_regs32[GDB_PS];
 189         regs->cs                = gdb_regs32[GDB_CS];
 190         regs->ss                = gdb_regs32[GDB_SS];
 191 #endif
 192 }
 193
 194 static struct hw_breakpoint {
 195         unsigned                enabled;
 196         unsigned long           addr;
 197         int                     len;
 198         int                     type;
 199         struct perf_event       **pev;
 200 } breakinfo[4];
 201
 202 static void kgdb_correct_hw_break(void)
 203 {
 204         int breakno;
 205
 206         for (breakno = 0; breakno < 4; breakno++) {
 207                 struct perf_event *bp;
 208                 struct arch_hw_breakpoint *info;
 209                 int val;
 210                 int cpu = raw_smp_processor_id();
 211                 if (!breakinfo[breakno].enabled)
 212                         continue;
 213                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
 214                 info = counter_arch_bp(bp);
 215                 if (bp->attr.disabled != 1)
 216                         continue;
 217                 bp->attr.bp_addr = breakinfo[breakno].addr;
 218                 bp->attr.bp_len = breakinfo[breakno].len;
 219                 bp->attr.bp_type = breakinfo[breakno].type;
 220                 info->address = breakinfo[breakno].addr;
 221                 info->len = breakinfo[breakno].len;
 222                 info->type = breakinfo[breakno].type;
 223                 val = arch_install_hw_breakpoint(bp);
 224                 if (!val)
 225                         bp->attr.disabled = 0;
 226         }
 227         hw_breakpoint_restore();
 228 }
 229
 230 static int hw_break_reserve_slot(int breakno)
 231 {
 232         int cpu;
 233         int cnt = 0;
 234         struct perf_event **pevent;
 235
 236         for_each_online_cpu(cpu) {
 237                 cnt++;
 238                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 239                 if (dbg_reserve_bp_slot(*pevent))
 240                         goto fail;
 241         }
 242
 243         return 0;
 244
 245 fail:
 246         for_each_online_cpu(cpu) {
 247                 cnt--;
 248                 if (!cnt)
 249                         break;
 250                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 251                 dbg_release_bp_slot(*pevent);
 252         }
 253         return -1;
 254 }
 255
 256 static int hw_break_release_slot(int breakno)
 257 {
 258         struct perf_event **pevent;
 259         int cpu;
 260
 261         for_each_online_cpu(cpu) {
 262                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 263                 if (dbg_release_bp_slot(*pevent))
 264                         /*
 265                          * The debugger is responisble for handing the retry on
 266                          * remove failure.
 267                          */
 268                         return -1;
 269         }
 270         return 0;
 271 }
 272
 273 static int
 274 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 275 {
 276         int i;
 277
 278         for (i = 0; i < 4; i++)
 279                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
 280                         break;
 281         if (i == 4)
 282                 return -1;
 283
 284         if (hw_break_release_slot(i)) {
 285                 printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
 286                 return -1;
 287         }
 288         breakinfo[i].enabled = 0;
 289
 290         return 0;
 291 }
 292
 293 static void kgdb_remove_all_hw_break(void)
 294 {
 295         int i;
 296         int cpu = raw_smp_processor_id();
 297         struct perf_event *bp;
 298
 299         for (i = 0; i < 4; i++) {
 300                 if (!breakinfo[i].enabled)
 301                         continue;
 302                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 303                 if (bp->attr.disabled == 1)
 304                         continue;
 305                 arch_uninstall_hw_breakpoint(bp);
 306                 bp->attr.disabled = 1;
 307         }
 308 }
 309
 310 static int
 311 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 312 {
 313         int i;
 314
 315         for (i = 0; i < 4; i++)
 316                 if (!breakinfo[i].enabled)
 317                         break;
 318         if (i == 4)
 319                 return -1;
 320
 321         switch (bptype) {
 322         case BP_HARDWARE_BREAKPOINT:
 323                 len = 1;
 324                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
 325                 break;
 326         case BP_WRITE_WATCHPOINT:
 327                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
 328                 break;
 329         case BP_ACCESS_WATCHPOINT:
 330                 breakinfo[i].type = X86_BREAKPOINT_RW;
 331                 break;
 332         default:
 333                 return -1;
 334         }
 335         switch (len) {
 336         case 1:
 337                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
 338                 break;
 339         case 2:
 340                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
 341                 break;
 342         case 4:
 343                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
 344                 break;
 345 #ifdef CONFIG_X86_64
 346         case 8:
 347                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
 348                 break;
 349 #endif
 350         default:
 351                 return -1;
 352         }
 353         breakinfo[i].addr = addr;
 354         if (hw_break_reserve_slot(i)) {
 355                 breakinfo[i].addr = 0;
 356                 return -1;
 357         }
 358         breakinfo[i].enabled = 1;
 359
 360         return 0;
 361 }
 362
 363 /**
 364  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 365  *      @regs: Current &struct pt_regs.
 366  *
 367  *      This function will be called if the particular architecture must
 368  *      disable hardware debugging while it is processing gdb packets or
 369  *      handling exception.
 370  */
 371 void kgdb_disable_hw_debug(struct pt_regs *regs)
 372 {
 373         int i;
 374         int cpu = raw_smp_processor_id();
 375         struct perf_event *bp;
 376
 377         /* Disable hardware debugging while we are in kgdb: */
 378         set_debugreg(0UL, 7);
 379         for (i = 0; i < 4; i++) {
 380                 if (!breakinfo[i].enabled)
 381                         continue;
 382                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 383                 if (bp->attr.disabled == 1)
 384                         continue;
 385                 arch_uninstall_hw_breakpoint(bp);
 386                 bp->attr.disabled = 1;
 387         }
 388 }
 389
 390 #ifdef CONFIG_SMP
 391 /**
 392  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 393  *      @flags: Current IRQ state
 394  *
 395  *      On SMP systems, we need to get the attention of the other CPUs
 396  *      and get them be in a known state.  This should do what is needed
 397  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 398  *      the NMI approach is not used for rounding up all the CPUs. For example,
 399  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 400  *      this case, we have to make sure that interrupts are enabled before
 401  *      calling smp_call_function(). The argument to this function is
 402  *      the flags that will be used when restoring the interrupts. There is
 403  *      local_irq_save() call before kgdb_roundup_cpus().
 404  *
 405  *      On non-SMP systems, this is not called.
 406  */
 407 void kgdb_roundup_cpus(unsigned long flags)
 408 {
 409         apic->send_IPI_allbutself(APIC_DM_NMI);
 410 }
 411 #endif
 412
 413 /**
 414  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 415  *      @vector: The error vector of the exception that happened.
 416  *      @signo: The signal number of the exception that happened.
 417  *      @err_code: The error code of the exception that happened.
 418  *      @remcom_in_buffer: The buffer of the packet we have read.
 419  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 420  *      @regs: The &struct pt_regs of the current process.
 421  *
 422  *      This function MUST handle the 'c' and 's' command packets,
 423  *      as well packets to set / remove a hardware breakpoint, if used.
 424  *      If there are additional packets which the hardware needs to handle,
 425  *      they are handled here.  The code should return -1 if it wants to
 426  *      process more packets, and a %0 or %1 if it wants to exit from the
 427  *      kgdb callback.
 428  */
 429 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 430                                char *remcomInBuffer, char *remcomOutBuffer,
 431                                struct pt_regs *linux_regs)
 432 {
 433         unsigned long addr;
 434         char *ptr;
 435         int newPC;
 436
 437         switch (remcomInBuffer[0]) {
 438         case 'c':
 439         case 's':
 440                 /* try to read optional parameter, pc unchanged if no parm */
 441                 ptr = &remcomInBuffer[1];
 442                 if (kgdb_hex2long(&ptr, &addr))
 443                         linux_regs->ip = addr;
 444         case 'D':
 445         case 'k':
 446                 newPC = linux_regs->ip;
 447
 448                 /* clear the trace bit */
 449                 linux_regs->flags &= ~X86_EFLAGS_TF;
 450                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 451
 452                 /* set the trace bit if we're stepping */
 453                 if (remcomInBuffer[0] == 's') {
 454                         linux_regs->flags |= X86_EFLAGS_TF;
 455                         atomic_set(&kgdb_cpu_doing_single_step,
 456                                    raw_smp_processor_id());
 457                 }
 458
 459                 kgdb_correct_hw_break();
 460
 461                 return 0;
 462         }
 463
 464         /* this means that we do not want to exit from the handler: */
 465         return -1;
 466 }
 467
 468 static inline int
 469 single_step_cont(struct pt_regs *regs, struct die_args *args)
 470 {
 471         /*
 472          * Single step exception from kernel space to user space so
 473          * eat the exception and continue the process:
 474          */
 475         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
 476                         "resuming...\n");
 477         kgdb_arch_handle_exception(args->trapnr, args->signr,
 478                                    args->err, "c", "", regs);
 479         /*
 480          * Reset the BS bit in dr6 (pointed by args->err) to
 481          * denote completion of processing
 482          */
 483         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 484
 485         return NOTIFY_STOP;
 486 }
 487
 488 static int was_in_debug_nmi[NR_CPUS];
 489
 490 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 491 {
 492         struct pt_regs *regs = args->regs;
 493
 494         switch (cmd) {
 495         case DIE_NMI:
 496                 if (atomic_read(&kgdb_active) != -1) {
 497                         /* KGDB CPU roundup */
 498                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 499                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
 500                         touch_nmi_watchdog();
 501                         return NOTIFY_STOP;
 502                 }
 503                 return NOTIFY_DONE;
 504
 505         case DIE_NMI_IPI:
 506                 /* Just ignore, we will handle the roundup on DIE_NMI. */
 507                 return NOTIFY_DONE;
 508
 509         case DIE_NMIUNKNOWN:
 510                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
 511                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
 512                         return NOTIFY_STOP;
 513                 }
 514                 return NOTIFY_DONE;
 515
 516         case DIE_NMIWATCHDOG:
 517                 if (atomic_read(&kgdb_active) != -1) {
 518                         /* KGDB CPU roundup: */
 519                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 520                         return NOTIFY_STOP;
 521                 }
 522                 /* Enter debugger: */
 523                 break;
 524
 525         case DIE_DEBUG:
 526                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 527                         if (user_mode(regs))
 528                                 return single_step_cont(regs, args);
 529                         break;
 530                 } else if (test_thread_flag(TIF_SINGLESTEP))
 531                         /* This means a user thread is single stepping
 532                          * a system call which should be ignored
 533                          */
 534                         return NOTIFY_DONE;
 535                 /* fall through */
 536         default:
 537                 if (user_mode(regs))
 538                         return NOTIFY_DONE;
 539         }
 540
 541         if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
 542                 return NOTIFY_DONE;
 543
 544         /* Must touch watchdog before return to normal operation */
 545         touch_nmi_watchdog();
 546         return NOTIFY_STOP;
 547 }
 548
 549 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 550 int kgdb_ll_trap(int cmd, const char *str,
 551                  struct pt_regs *regs, long err, int trap, int sig)
 552 {
 553         struct die_args args = {
 554                 .regs   = regs,
 555                 .str    = str,
 556                 .err    = err,
 557                 .trapnr = trap,
 558                 .signr  = sig,
 559
 560         };
 561
 562         if (!kgdb_io_module_registered)
 563                 return NOTIFY_DONE;
 564
 565         return __kgdb_notify(&args, cmd);
 566 }
 567 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 568
 569 static int
 570 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 571 {
 572         unsigned long flags;
 573         int ret;
 574
 575         local_irq_save(flags);
 576         ret = __kgdb_notify(ptr, cmd);
 577         local_irq_restore(flags);
 578
 579         return ret;
 580 }
 581
 582 static struct notifier_block kgdb_notifier = {
 583         .notifier_call  = kgdb_notify,
 584
 585         /*
 586          * Lowest-prio notifier priority, we want to be notified last:
 587          */
 588         .priority       = -INT_MAX,
 589 };
 590
 591 /**
 592  *      kgdb_arch_init - Perform any architecture specific initalization.
 593  *
 594  *      This function will handle the initalization of any architecture
 595  *      specific callbacks.
 596  */
 597 int kgdb_arch_init(void)
 598 {
 599         int i, cpu;
 600         int ret;
 601         struct perf_event_attr attr;
 602         struct perf_event **pevent;
 603
 604         ret = register_die_notifier(&kgdb_notifier);
 605         if (ret != 0)
 606                 return ret;
 607         /*
 608          * Pre-allocate the hw breakpoint structions in the non-atomic
 609          * portion of kgdb because this operation requires mutexs to
 610          * complete.
 611          */
 612         hw_breakpoint_init(&attr);
 613         attr.bp_addr = (unsigned long)kgdb_arch_init;
 614         attr.bp_len = HW_BREAKPOINT_LEN_1;
 615         attr.bp_type = HW_BREAKPOINT_W;
 616         attr.disabled = 1;
 617         for (i = 0; i < 4; i++) {
 618                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
 619                 if (IS_ERR(breakinfo[i].pev)) {
 620                         printk(KERN_ERR "kgdb: Could not allocate hw breakpoints\n");
 621                         breakinfo[i].pev = NULL;
 622                         kgdb_arch_exit();
 623                         return -1;
 624                 }
 625                 for_each_online_cpu(cpu) {
 626                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
 627                         pevent[0]->hw.sample_period = 1;
 628                         if (pevent[0]->destroy != NULL) {
 629                                 pevent[0]->destroy = NULL;
 630                                 release_bp_slot(*pevent);
 631                         }
 632                 }
 633         }
 634         return ret;
 635 }
 636
 637 /**
 638  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
 639  *
 640  *      This function will handle the uninitalization of any architecture
 641  *      specific callbacks, for dynamic registration and unregistration.
 642  */
 643 void kgdb_arch_exit(void)
 644 {
 645         int i;
 646         for (i = 0; i < 4; i++) {
 647                 if (breakinfo[i].pev) {
 648                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
 649                         breakinfo[i].pev = NULL;
 650                 }
 651         }
 652         unregister_die_notifier(&kgdb_notifier);
 653 }
 654
 655 /**
 656  *
 657  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 658  *      @exception: Exception vector number
 659  *      @regs: Current &struct pt_regs.
 660  *
 661  *      On some architectures we need to skip a breakpoint exception when
 662  *      it occurs after a breakpoint has been removed.
 663  *
 664  * Skip an int3 exception when it occurs after a breakpoint has been
 665  * removed. Backtrack eip by 1 since the int3 would have caused it to
 666  * increment by 1.
 667  */
 668 int kgdb_skipexception(int exception, struct pt_regs *regs)
 669 {
 670         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
 671                 regs->ip -= 1;
 672                 return 1;
 673         }
 674         return 0;
 675 }
 676
 677 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 678 {
 679         if (exception == 3)
 680                 return instruction_pointer(regs) - 1;
 681         return instruction_pointer(regs);
 682 }
 683
 684 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 685 {
 686         regs->ip = ip;
 687 }
 688
 689 struct kgdb_arch arch_kgdb_ops = {
 690         /* Breakpoint instruction: */
 691         .gdb_bpt_instr          = { 0xcc },
 692         .flags                  = KGDB_HW_BREAKPOINT,
 693         .set_hw_breakpoint      = kgdb_set_hw_break,
 694         .remove_hw_breakpoint   = kgdb_remove_hw_break,
 695         .remove_all_hw_break    = kgdb_remove_all_hw_break,
 696         .correct_hw_break       = kgdb_correct_hw_break,
 697 };