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 unsigned long early_dr7;
 203
 204 static void kgdb_correct_hw_break(void)
 205 {
 206         int breakno;
 207
 208         for (breakno = 0; breakno < 4; breakno++) {
 209                 struct perf_event *bp;
 210                 struct arch_hw_breakpoint *info;
 211                 int val;
 212                 int cpu = raw_smp_processor_id();
 213                 if (!breakinfo[breakno].enabled)
 214                         continue;
 215                 if (dbg_is_early) {
 216                         set_debugreg(breakinfo[breakno].addr, breakno);
 217                         early_dr7 |= encode_dr7(breakno,
 218                                                 breakinfo[breakno].len,
 219                                                 breakinfo[breakno].type);
 220                         set_debugreg(early_dr7, 7);
 221                         continue;
 222                 }
 223                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
 224                 info = counter_arch_bp(bp);
 225                 if (bp->attr.disabled != 1)
 226                         continue;
 227                 bp->attr.bp_addr = breakinfo[breakno].addr;
 228                 bp->attr.bp_len = breakinfo[breakno].len;
 229                 bp->attr.bp_type = breakinfo[breakno].type;
 230                 info->address = breakinfo[breakno].addr;
 231                 info->len = breakinfo[breakno].len;
 232                 info->type = breakinfo[breakno].type;
 233                 val = arch_install_hw_breakpoint(bp);
 234                 if (!val)
 235                         bp->attr.disabled = 0;
 236         }
 237         if (!dbg_is_early)
 238                 hw_breakpoint_restore();
 239 }
 240
 241 static int hw_break_reserve_slot(int breakno)
 242 {
 243         int cpu;
 244         int cnt = 0;
 245         struct perf_event **pevent;
 246
 247         if (dbg_is_early)
 248                 return 0;
 249
 250         for_each_online_cpu(cpu) {
 251                 cnt++;
 252                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 253                 if (dbg_reserve_bp_slot(*pevent))
 254                         goto fail;
 255         }
 256
 257         return 0;
 258
 259 fail:
 260         for_each_online_cpu(cpu) {
 261                 cnt--;
 262                 if (!cnt)
 263                         break;
 264                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 265                 dbg_release_bp_slot(*pevent);
 266         }
 267         return -1;
 268 }
 269
 270 static int hw_break_release_slot(int breakno)
 271 {
 272         struct perf_event **pevent;
 273         int cpu;
 274
 275         if (dbg_is_early)
 276                 return 0;
 277
 278         for_each_online_cpu(cpu) {
 279                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
 280                 if (dbg_release_bp_slot(*pevent))
 281                         /*
 282                          * The debugger is responisble for handing the retry on
 283                          * remove failure.
 284                          */
 285                         return -1;
 286         }
 287         return 0;
 288 }
 289
 290 static int
 291 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 292 {
 293         int i;
 294
 295         for (i = 0; i < 4; i++)
 296                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
 297                         break;
 298         if (i == 4)
 299                 return -1;
 300
 301         if (hw_break_release_slot(i)) {
 302                 printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
 303                 return -1;
 304         }
 305         breakinfo[i].enabled = 0;
 306
 307         return 0;
 308 }
 309
 310 static void kgdb_remove_all_hw_break(void)
 311 {
 312         int i;
 313         int cpu = raw_smp_processor_id();
 314         struct perf_event *bp;
 315
 316         for (i = 0; i < 4; i++) {
 317                 if (!breakinfo[i].enabled)
 318                         continue;
 319                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 320                 if (bp->attr.disabled == 1)
 321                         continue;
 322                 if (dbg_is_early)
 323                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
 324                                                  breakinfo[i].type);
 325                 else
 326                         arch_uninstall_hw_breakpoint(bp);
 327                 bp->attr.disabled = 1;
 328         }
 329 }
 330
 331 static int
 332 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
 333 {
 334         int i;
 335
 336         for (i = 0; i < 4; i++)
 337                 if (!breakinfo[i].enabled)
 338                         break;
 339         if (i == 4)
 340                 return -1;
 341
 342         switch (bptype) {
 343         case BP_HARDWARE_BREAKPOINT:
 344                 len = 1;
 345                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
 346                 break;
 347         case BP_WRITE_WATCHPOINT:
 348                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
 349                 break;
 350         case BP_ACCESS_WATCHPOINT:
 351                 breakinfo[i].type = X86_BREAKPOINT_RW;
 352                 break;
 353         default:
 354                 return -1;
 355         }
 356         switch (len) {
 357         case 1:
 358                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
 359                 break;
 360         case 2:
 361                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
 362                 break;
 363         case 4:
 364                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
 365                 break;
 366 #ifdef CONFIG_X86_64
 367         case 8:
 368                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
 369                 break;
 370 #endif
 371         default:
 372                 return -1;
 373         }
 374         breakinfo[i].addr = addr;
 375         if (hw_break_reserve_slot(i)) {
 376                 breakinfo[i].addr = 0;
 377                 return -1;
 378         }
 379         breakinfo[i].enabled = 1;
 380
 381         return 0;
 382 }
 383
 384 /**
 385  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 386  *      @regs: Current &struct pt_regs.
 387  *
 388  *      This function will be called if the particular architecture must
 389  *      disable hardware debugging while it is processing gdb packets or
 390  *      handling exception.
 391  */
 392 void kgdb_disable_hw_debug(struct pt_regs *regs)
 393 {
 394         int i;
 395         int cpu = raw_smp_processor_id();
 396         struct perf_event *bp;
 397
 398         /* Disable hardware debugging while we are in kgdb: */
 399         set_debugreg(0UL, 7);
 400         for (i = 0; i < 4; i++) {
 401                 if (!breakinfo[i].enabled)
 402                         continue;
 403                 if (dbg_is_early) {
 404                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
 405                                                  breakinfo[i].type);
 406                         continue;
 407                 }
 408                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
 409                 if (bp->attr.disabled == 1)
 410                         continue;
 411                 arch_uninstall_hw_breakpoint(bp);
 412                 bp->attr.disabled = 1;
 413         }
 414 }
 415
 416 #ifdef CONFIG_SMP
 417 /**
 418  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 419  *      @flags: Current IRQ state
 420  *
 421  *      On SMP systems, we need to get the attention of the other CPUs
 422  *      and get them be in a known state.  This should do what is needed
 423  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 424  *      the NMI approach is not used for rounding up all the CPUs. For example,
 425  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 426  *      this case, we have to make sure that interrupts are enabled before
 427  *      calling smp_call_function(). The argument to this function is
 428  *      the flags that will be used when restoring the interrupts. There is
 429  *      local_irq_save() call before kgdb_roundup_cpus().
 430  *
 431  *      On non-SMP systems, this is not called.
 432  */
 433 void kgdb_roundup_cpus(unsigned long flags)
 434 {
 435         apic->send_IPI_allbutself(APIC_DM_NMI);
 436 }
 437 #endif
 438
 439 /**
 440  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 441  *      @vector: The error vector of the exception that happened.
 442  *      @signo: The signal number of the exception that happened.
 443  *      @err_code: The error code of the exception that happened.
 444  *      @remcom_in_buffer: The buffer of the packet we have read.
 445  *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 446  *      @regs: The &struct pt_regs of the current process.
 447  *
 448  *      This function MUST handle the 'c' and 's' command packets,
 449  *      as well packets to set / remove a hardware breakpoint, if used.
 450  *      If there are additional packets which the hardware needs to handle,
 451  *      they are handled here.  The code should return -1 if it wants to
 452  *      process more packets, and a %0 or %1 if it wants to exit from the
 453  *      kgdb callback.
 454  */
 455 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 456                                char *remcomInBuffer, char *remcomOutBuffer,
 457                                struct pt_regs *linux_regs)
 458 {
 459         unsigned long addr;
 460         char *ptr;
 461         int newPC;
 462
 463         switch (remcomInBuffer[0]) {
 464         case 'c':
 465         case 's':
 466                 /* try to read optional parameter, pc unchanged if no parm */
 467                 ptr = &remcomInBuffer[1];
 468                 if (kgdb_hex2long(&ptr, &addr))
 469                         linux_regs->ip = addr;
 470         case 'D':
 471         case 'k':
 472                 newPC = linux_regs->ip;
 473
 474                 /* clear the trace bit */
 475                 linux_regs->flags &= ~X86_EFLAGS_TF;
 476                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 477
 478                 /* set the trace bit if we're stepping */
 479                 if (remcomInBuffer[0] == 's') {
 480                         linux_regs->flags |= X86_EFLAGS_TF;
 481                         atomic_set(&kgdb_cpu_doing_single_step,
 482                                    raw_smp_processor_id());
 483                 }
 484
 485                 kgdb_correct_hw_break();
 486
 487                 return 0;
 488         }
 489
 490         /* this means that we do not want to exit from the handler: */
 491         return -1;
 492 }
 493
 494 static inline int
 495 single_step_cont(struct pt_regs *regs, struct die_args *args)
 496 {
 497         /*
 498          * Single step exception from kernel space to user space so
 499          * eat the exception and continue the process:
 500          */
 501         printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
 502                         "resuming...\n");
 503         kgdb_arch_handle_exception(args->trapnr, args->signr,
 504                                    args->err, "c", "", regs);
 505         /*
 506          * Reset the BS bit in dr6 (pointed by args->err) to
 507          * denote completion of processing
 508          */
 509         (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 510
 511         return NOTIFY_STOP;
 512 }
 513
 514 static int was_in_debug_nmi[NR_CPUS];
 515
 516 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 517 {
 518         struct pt_regs *regs = args->regs;
 519
 520         switch (cmd) {
 521         case DIE_NMI:
 522                 if (atomic_read(&kgdb_active) != -1) {
 523                         /* KGDB CPU roundup */
 524                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 525                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
 526                         touch_nmi_watchdog();
 527                         return NOTIFY_STOP;
 528                 }
 529                 return NOTIFY_DONE;
 530
 531         case DIE_NMI_IPI:
 532                 /* Just ignore, we will handle the roundup on DIE_NMI. */
 533                 return NOTIFY_DONE;
 534
 535         case DIE_NMIUNKNOWN:
 536                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
 537                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
 538                         return NOTIFY_STOP;
 539                 }
 540                 return NOTIFY_DONE;
 541
 542         case DIE_NMIWATCHDOG:
 543                 if (atomic_read(&kgdb_active) != -1) {
 544                         /* KGDB CPU roundup: */
 545                         kgdb_nmicallback(raw_smp_processor_id(), regs);
 546                         return NOTIFY_STOP;
 547                 }
 548                 /* Enter debugger: */
 549                 break;
 550
 551         case DIE_DEBUG:
 552                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
 553                         if (user_mode(regs))
 554                                 return single_step_cont(regs, args);
 555                         break;
 556                 } else if (test_thread_flag(TIF_SINGLESTEP))
 557                         /* This means a user thread is single stepping
 558                          * a system call which should be ignored
 559                          */
 560                         return NOTIFY_DONE;
 561                 /* fall through */
 562         default:
 563                 if (user_mode(regs))
 564                         return NOTIFY_DONE;
 565         }
 566
 567         if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
 568                 return NOTIFY_DONE;
 569
 570         /* Must touch watchdog before return to normal operation */
 571         touch_nmi_watchdog();
 572         return NOTIFY_STOP;
 573 }
 574
 575 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 576 int kgdb_ll_trap(int cmd, const char *str,
 577                  struct pt_regs *regs, long err, int trap, int sig)
 578 {
 579         struct die_args args = {
 580                 .regs   = regs,
 581                 .str    = str,
 582                 .err    = err,
 583                 .trapnr = trap,
 584                 .signr  = sig,
 585
 586         };
 587
 588         if (!kgdb_io_module_registered)
 589                 return NOTIFY_DONE;
 590
 591         return __kgdb_notify(&args, cmd);
 592 }
 593 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 594
 595 static int
 596 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 597 {
 598         unsigned long flags;
 599         int ret;
 600
 601         local_irq_save(flags);
 602         ret = __kgdb_notify(ptr, cmd);
 603         local_irq_restore(flags);
 604
 605         return ret;
 606 }
 607
 608 static struct notifier_block kgdb_notifier = {
 609         .notifier_call  = kgdb_notify,
 610
 611         /*
 612          * Lowest-prio notifier priority, we want to be notified last:
 613          */
 614         .priority       = -INT_MAX,
 615 };
 616
 617 /**
 618  *      kgdb_arch_init - Perform any architecture specific initalization.
 619  *
 620  *      This function will handle the initalization of any architecture
 621  *      specific callbacks.
 622  */
 623 int kgdb_arch_init(void)
 624 {
 625         return register_die_notifier(&kgdb_notifier);
 626 }
 627
 628 void kgdb_arch_late(void)
 629 {
 630         int i, cpu;
 631         struct perf_event_attr attr;
 632         struct perf_event **pevent;
 633
 634         /*
 635          * Pre-allocate the hw breakpoint structions in the non-atomic
 636          * portion of kgdb because this operation requires mutexs to
 637          * complete.
 638          */
 639         hw_breakpoint_init(&attr);
 640         attr.bp_addr = (unsigned long)kgdb_arch_init;
 641         attr.bp_len = HW_BREAKPOINT_LEN_1;
 642         attr.bp_type = HW_BREAKPOINT_W;
 643         attr.disabled = 1;
 644         for (i = 0; i < 4; i++) {
 645                 if (breakinfo[i].pev)
 646                         continue;
 647                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL);
 648                 if (IS_ERR(breakinfo[i].pev)) {
 649                         printk(KERN_ERR "kgdb: Could not allocate hw"
 650                                "breakpoints\nDisabling the kernel debugger\n");
 651                         breakinfo[i].pev = NULL;
 652                         kgdb_arch_exit();
 653                         return;
 654                 }
 655                 for_each_online_cpu(cpu) {
 656                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
 657                         pevent[0]->hw.sample_period = 1;
 658                         if (pevent[0]->destroy != NULL) {
 659                                 pevent[0]->destroy = NULL;
 660                                 release_bp_slot(*pevent);
 661                         }
 662                 }
 663         }
 664 }
 665
 666 /**
 667  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
 668  *
 669  *      This function will handle the uninitalization of any architecture
 670  *      specific callbacks, for dynamic registration and unregistration.
 671  */
 672 void kgdb_arch_exit(void)
 673 {
 674         int i;
 675         for (i = 0; i < 4; i++) {
 676                 if (breakinfo[i].pev) {
 677                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
 678                         breakinfo[i].pev = NULL;
 679                 }
 680         }
 681         unregister_die_notifier(&kgdb_notifier);
 682 }
 683
 684 /**
 685  *
 686  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 687  *      @exception: Exception vector number
 688  *      @regs: Current &struct pt_regs.
 689  *
 690  *      On some architectures we need to skip a breakpoint exception when
 691  *      it occurs after a breakpoint has been removed.
 692  *
 693  * Skip an int3 exception when it occurs after a breakpoint has been
 694  * removed. Backtrack eip by 1 since the int3 would have caused it to
 695  * increment by 1.
 696  */
 697 int kgdb_skipexception(int exception, struct pt_regs *regs)
 698 {
 699         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
 700                 regs->ip -= 1;
 701                 return 1;
 702         }
 703         return 0;
 704 }
 705
 706 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 707 {
 708         if (exception == 3)
 709                 return instruction_pointer(regs) - 1;
 710         return instruction_pointer(regs);
 711 }
 712
 713 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 714 {
 715         regs->ip = ip;
 716 }
 717
 718 struct kgdb_arch arch_kgdb_ops = {
 719         /* Breakpoint instruction: */
 720         .gdb_bpt_instr          = { 0xcc },
 721         .flags                  = KGDB_HW_BREAKPOINT,
 722         .set_hw_breakpoint      = kgdb_set_hw_break,
 723         .remove_hw_breakpoint   = kgdb_remove_hw_break,
 724         .remove_all_hw_break    = kgdb_remove_all_hw_break,
 725         .correct_hw_break       = kgdb_correct_hw_break,
 726 };