kgdb.c revision cf6f196d112a6f6757b1ca3cce0b576f7abee479
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 46#include <asm/debugreg.h> 47#include <asm/apicdef.h> 48#include <asm/system.h> 49 50#include <asm/apic.h> 51 52/* 53 * Put the error code here just in case the user cares: 54 */ 55static int gdb_x86errcode; 56 57/* 58 * Likewise, the vector number here (since GDB only gets the signal 59 * number through the usual means, and that's not very specific): 60 */ 61static int gdb_x86vector = -1; 62 63/** 64 * pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs 65 * @gdb_regs: A pointer to hold the registers in the order GDB wants. 66 * @regs: The &struct pt_regs of the current process. 67 * 68 * Convert the pt_regs in @regs into the format for registers that 69 * GDB expects, stored in @gdb_regs. 70 */ 71void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs) 72{ 73#ifndef CONFIG_X86_32 74 u32 *gdb_regs32 = (u32 *)gdb_regs; 75#endif 76 gdb_regs[GDB_AX] = regs->ax; 77 gdb_regs[GDB_BX] = regs->bx; 78 gdb_regs[GDB_CX] = regs->cx; 79 gdb_regs[GDB_DX] = regs->dx; 80 gdb_regs[GDB_SI] = regs->si; 81 gdb_regs[GDB_DI] = regs->di; 82 gdb_regs[GDB_BP] = regs->bp; 83 gdb_regs[GDB_PC] = regs->ip; 84#ifdef CONFIG_X86_32 85 gdb_regs[GDB_PS] = regs->flags; 86 gdb_regs[GDB_DS] = regs->ds; 87 gdb_regs[GDB_ES] = regs->es; 88 gdb_regs[GDB_CS] = regs->cs; 89 gdb_regs[GDB_FS] = 0xFFFF; 90 gdb_regs[GDB_GS] = 0xFFFF; 91 if (user_mode_vm(regs)) { 92 gdb_regs[GDB_SS] = regs->ss; 93 gdb_regs[GDB_SP] = regs->sp; 94 } else { 95 gdb_regs[GDB_SS] = __KERNEL_DS; 96 gdb_regs[GDB_SP] = kernel_stack_pointer(regs); 97 } 98#else 99 gdb_regs[GDB_R8] = regs->r8; 100 gdb_regs[GDB_R9] = regs->r9; 101 gdb_regs[GDB_R10] = regs->r10; 102 gdb_regs[GDB_R11] = regs->r11; 103 gdb_regs[GDB_R12] = regs->r12; 104 gdb_regs[GDB_R13] = regs->r13; 105 gdb_regs[GDB_R14] = regs->r14; 106 gdb_regs[GDB_R15] = regs->r15; 107 gdb_regs32[GDB_PS] = regs->flags; 108 gdb_regs32[GDB_CS] = regs->cs; 109 gdb_regs32[GDB_SS] = regs->ss; 110 gdb_regs[GDB_SP] = kernel_stack_pointer(regs); 111#endif 112} 113 114/** 115 * sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs 116 * @gdb_regs: A pointer to hold the registers in the order GDB wants. 117 * @p: The &struct task_struct of the desired process. 118 * 119 * Convert the register values of the sleeping process in @p to 120 * the format that GDB expects. 121 * This function is called when kgdb does not have access to the 122 * &struct pt_regs and therefore it should fill the gdb registers 123 * @gdb_regs with what has been saved in &struct thread_struct 124 * thread field during switch_to. 125 */ 126void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p) 127{ 128#ifndef CONFIG_X86_32 129 u32 *gdb_regs32 = (u32 *)gdb_regs; 130#endif 131 gdb_regs[GDB_AX] = 0; 132 gdb_regs[GDB_BX] = 0; 133 gdb_regs[GDB_CX] = 0; 134 gdb_regs[GDB_DX] = 0; 135 gdb_regs[GDB_SI] = 0; 136 gdb_regs[GDB_DI] = 0; 137 gdb_regs[GDB_BP] = *(unsigned long *)p->thread.sp; 138#ifdef CONFIG_X86_32 139 gdb_regs[GDB_DS] = __KERNEL_DS; 140 gdb_regs[GDB_ES] = __KERNEL_DS; 141 gdb_regs[GDB_PS] = 0; 142 gdb_regs[GDB_CS] = __KERNEL_CS; 143 gdb_regs[GDB_PC] = p->thread.ip; 144 gdb_regs[GDB_SS] = __KERNEL_DS; 145 gdb_regs[GDB_FS] = 0xFFFF; 146 gdb_regs[GDB_GS] = 0xFFFF; 147#else 148 gdb_regs32[GDB_PS] = *(unsigned long *)(p->thread.sp + 8); 149 gdb_regs32[GDB_CS] = __KERNEL_CS; 150 gdb_regs32[GDB_SS] = __KERNEL_DS; 151 gdb_regs[GDB_PC] = 0; 152 gdb_regs[GDB_R8] = 0; 153 gdb_regs[GDB_R9] = 0; 154 gdb_regs[GDB_R10] = 0; 155 gdb_regs[GDB_R11] = 0; 156 gdb_regs[GDB_R12] = 0; 157 gdb_regs[GDB_R13] = 0; 158 gdb_regs[GDB_R14] = 0; 159 gdb_regs[GDB_R15] = 0; 160#endif 161 gdb_regs[GDB_SP] = p->thread.sp; 162} 163 164/** 165 * gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs. 166 * @gdb_regs: A pointer to hold the registers we've received from GDB. 167 * @regs: A pointer to a &struct pt_regs to hold these values in. 168 * 169 * Convert the GDB regs in @gdb_regs into the pt_regs, and store them 170 * in @regs. 171 */ 172void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs) 173{ 174#ifndef CONFIG_X86_32 175 u32 *gdb_regs32 = (u32 *)gdb_regs; 176#endif 177 regs->ax = gdb_regs[GDB_AX]; 178 regs->bx = gdb_regs[GDB_BX]; 179 regs->cx = gdb_regs[GDB_CX]; 180 regs->dx = gdb_regs[GDB_DX]; 181 regs->si = gdb_regs[GDB_SI]; 182 regs->di = gdb_regs[GDB_DI]; 183 regs->bp = gdb_regs[GDB_BP]; 184 regs->ip = gdb_regs[GDB_PC]; 185#ifdef CONFIG_X86_32 186 regs->flags = gdb_regs[GDB_PS]; 187 regs->ds = gdb_regs[GDB_DS]; 188 regs->es = gdb_regs[GDB_ES]; 189 regs->cs = gdb_regs[GDB_CS]; 190#else 191 regs->r8 = gdb_regs[GDB_R8]; 192 regs->r9 = gdb_regs[GDB_R9]; 193 regs->r10 = gdb_regs[GDB_R10]; 194 regs->r11 = gdb_regs[GDB_R11]; 195 regs->r12 = gdb_regs[GDB_R12]; 196 regs->r13 = gdb_regs[GDB_R13]; 197 regs->r14 = gdb_regs[GDB_R14]; 198 regs->r15 = gdb_regs[GDB_R15]; 199 regs->flags = gdb_regs32[GDB_PS]; 200 regs->cs = gdb_regs32[GDB_CS]; 201 regs->ss = gdb_regs32[GDB_SS]; 202#endif 203} 204 205static struct hw_breakpoint { 206 unsigned enabled; 207 unsigned type; 208 unsigned len; 209 unsigned long addr; 210} breakinfo[4]; 211 212static void kgdb_correct_hw_break(void) 213{ 214 unsigned long dr7; 215 int correctit = 0; 216 int breakbit; 217 int breakno; 218 219 get_debugreg(dr7, 7); 220 for (breakno = 0; breakno < 4; breakno++) { 221 breakbit = 2 << (breakno << 1); 222 if (!(dr7 & breakbit) && breakinfo[breakno].enabled) { 223 correctit = 1; 224 dr7 |= breakbit; 225 dr7 &= ~(0xf0000 << (breakno << 2)); 226 dr7 |= ((breakinfo[breakno].len << 2) | 227 breakinfo[breakno].type) << 228 ((breakno << 2) + 16); 229 set_debugreg(breakinfo[breakno].addr, breakno); 230 231 } else { 232 if ((dr7 & breakbit) && !breakinfo[breakno].enabled) { 233 correctit = 1; 234 dr7 &= ~breakbit; 235 dr7 &= ~(0xf0000 << (breakno << 2)); 236 } 237 } 238 } 239 if (correctit) 240 set_debugreg(dr7, 7); 241} 242 243static int 244kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) 245{ 246 int i; 247 248 for (i = 0; i < 4; i++) 249 if (breakinfo[i].addr == addr && breakinfo[i].enabled) 250 break; 251 if (i == 4) 252 return -1; 253 254 breakinfo[i].enabled = 0; 255 256 return 0; 257} 258 259static void kgdb_remove_all_hw_break(void) 260{ 261 int i; 262 263 for (i = 0; i < 4; i++) 264 memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint)); 265} 266 267static int 268kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype) 269{ 270 unsigned type; 271 int i; 272 273 for (i = 0; i < 4; i++) 274 if (!breakinfo[i].enabled) 275 break; 276 if (i == 4) 277 return -1; 278 279 switch (bptype) { 280 case BP_HARDWARE_BREAKPOINT: 281 type = 0; 282 len = 1; 283 break; 284 case BP_WRITE_WATCHPOINT: 285 type = 1; 286 break; 287 case BP_ACCESS_WATCHPOINT: 288 type = 3; 289 break; 290 default: 291 return -1; 292 } 293 294 if (len == 1 || len == 2 || len == 4) 295 breakinfo[i].len = len - 1; 296 else 297 return -1; 298 299 breakinfo[i].enabled = 1; 300 breakinfo[i].addr = addr; 301 breakinfo[i].type = type; 302 303 return 0; 304} 305 306/** 307 * kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb. 308 * @regs: Current &struct pt_regs. 309 * 310 * This function will be called if the particular architecture must 311 * disable hardware debugging while it is processing gdb packets or 312 * handling exception. 313 */ 314void kgdb_disable_hw_debug(struct pt_regs *regs) 315{ 316 /* Disable hardware debugging while we are in kgdb: */ 317 set_debugreg(0UL, 7); 318} 319 320/** 321 * kgdb_post_primary_code - Save error vector/code numbers. 322 * @regs: Original pt_regs. 323 * @e_vector: Original error vector. 324 * @err_code: Original error code. 325 * 326 * This is needed on architectures which support SMP and KGDB. 327 * This function is called after all the slave cpus have been put 328 * to a know spin state and the primary CPU has control over KGDB. 329 */ 330void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code) 331{ 332 /* primary processor is completely in the debugger */ 333 gdb_x86vector = e_vector; 334 gdb_x86errcode = err_code; 335} 336 337#ifdef CONFIG_SMP 338/** 339 * kgdb_roundup_cpus - Get other CPUs into a holding pattern 340 * @flags: Current IRQ state 341 * 342 * On SMP systems, we need to get the attention of the other CPUs 343 * and get them be in a known state. This should do what is needed 344 * to get the other CPUs to call kgdb_wait(). Note that on some arches, 345 * the NMI approach is not used for rounding up all the CPUs. For example, 346 * in case of MIPS, smp_call_function() is used to roundup CPUs. In 347 * this case, we have to make sure that interrupts are enabled before 348 * calling smp_call_function(). The argument to this function is 349 * the flags that will be used when restoring the interrupts. There is 350 * local_irq_save() call before kgdb_roundup_cpus(). 351 * 352 * On non-SMP systems, this is not called. 353 */ 354void kgdb_roundup_cpus(unsigned long flags) 355{ 356 apic->send_IPI_allbutself(APIC_DM_NMI); 357} 358#endif 359 360/** 361 * kgdb_arch_handle_exception - Handle architecture specific GDB packets. 362 * @vector: The error vector of the exception that happened. 363 * @signo: The signal number of the exception that happened. 364 * @err_code: The error code of the exception that happened. 365 * @remcom_in_buffer: The buffer of the packet we have read. 366 * @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into. 367 * @regs: The &struct pt_regs of the current process. 368 * 369 * This function MUST handle the 'c' and 's' command packets, 370 * as well packets to set / remove a hardware breakpoint, if used. 371 * If there are additional packets which the hardware needs to handle, 372 * they are handled here. The code should return -1 if it wants to 373 * process more packets, and a %0 or %1 if it wants to exit from the 374 * kgdb callback. 375 */ 376int kgdb_arch_handle_exception(int e_vector, int signo, int err_code, 377 char *remcomInBuffer, char *remcomOutBuffer, 378 struct pt_regs *linux_regs) 379{ 380 unsigned long addr; 381 unsigned long dr6; 382 char *ptr; 383 int newPC; 384 385 switch (remcomInBuffer[0]) { 386 case 'c': 387 case 's': 388 /* try to read optional parameter, pc unchanged if no parm */ 389 ptr = &remcomInBuffer[1]; 390 if (kgdb_hex2long(&ptr, &addr)) 391 linux_regs->ip = addr; 392 case 'D': 393 case 'k': 394 newPC = linux_regs->ip; 395 396 /* clear the trace bit */ 397 linux_regs->flags &= ~X86_EFLAGS_TF; 398 atomic_set(&kgdb_cpu_doing_single_step, -1); 399 400 /* set the trace bit if we're stepping */ 401 if (remcomInBuffer[0] == 's') { 402 linux_regs->flags |= X86_EFLAGS_TF; 403 kgdb_single_step = 1; 404 atomic_set(&kgdb_cpu_doing_single_step, 405 raw_smp_processor_id()); 406 } 407 408 get_debugreg(dr6, 6); 409 if (!(dr6 & 0x4000)) { 410 int breakno; 411 412 for (breakno = 0; breakno < 4; breakno++) { 413 if (dr6 & (1 << breakno) && 414 breakinfo[breakno].type == 0) { 415 /* Set restore flag: */ 416 linux_regs->flags |= X86_EFLAGS_RF; 417 break; 418 } 419 } 420 } 421 set_debugreg(0UL, 6); 422 kgdb_correct_hw_break(); 423 424 return 0; 425 } 426 427 /* this means that we do not want to exit from the handler: */ 428 return -1; 429} 430 431static inline int 432single_step_cont(struct pt_regs *regs, struct die_args *args) 433{ 434 /* 435 * Single step exception from kernel space to user space so 436 * eat the exception and continue the process: 437 */ 438 printk(KERN_ERR "KGDB: trap/step from kernel to user space, " 439 "resuming...\n"); 440 kgdb_arch_handle_exception(args->trapnr, args->signr, 441 args->err, "c", "", regs); 442 /* 443 * Reset the BS bit in dr6 (pointed by args->err) to 444 * denote completion of processing 445 */ 446 (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; 447 448 return NOTIFY_STOP; 449} 450 451static int was_in_debug_nmi[NR_CPUS]; 452 453static int __kgdb_notify(struct die_args *args, unsigned long cmd) 454{ 455 struct pt_regs *regs = args->regs; 456 457 switch (cmd) { 458 case DIE_NMI: 459 if (atomic_read(&kgdb_active) != -1) { 460 /* KGDB CPU roundup */ 461 kgdb_nmicallback(raw_smp_processor_id(), regs); 462 was_in_debug_nmi[raw_smp_processor_id()] = 1; 463 touch_nmi_watchdog(); 464 return NOTIFY_STOP; 465 } 466 return NOTIFY_DONE; 467 468 case DIE_NMI_IPI: 469 /* Just ignore, we will handle the roundup on DIE_NMI. */ 470 return NOTIFY_DONE; 471 472 case DIE_NMIUNKNOWN: 473 if (was_in_debug_nmi[raw_smp_processor_id()]) { 474 was_in_debug_nmi[raw_smp_processor_id()] = 0; 475 return NOTIFY_STOP; 476 } 477 return NOTIFY_DONE; 478 479 case DIE_NMIWATCHDOG: 480 if (atomic_read(&kgdb_active) != -1) { 481 /* KGDB CPU roundup: */ 482 kgdb_nmicallback(raw_smp_processor_id(), regs); 483 return NOTIFY_STOP; 484 } 485 /* Enter debugger: */ 486 break; 487 488 case DIE_DEBUG: 489 if (atomic_read(&kgdb_cpu_doing_single_step) == 490 raw_smp_processor_id()) { 491 if (user_mode(regs)) 492 return single_step_cont(regs, args); 493 break; 494 } else if (test_thread_flag(TIF_SINGLESTEP)) 495 /* This means a user thread is single stepping 496 * a system call which should be ignored 497 */ 498 return NOTIFY_DONE; 499 /* fall through */ 500 default: 501 if (user_mode(regs)) 502 return NOTIFY_DONE; 503 } 504 505 if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs)) 506 return NOTIFY_DONE; 507 508 /* Must touch watchdog before return to normal operation */ 509 touch_nmi_watchdog(); 510 return NOTIFY_STOP; 511} 512 513static int 514kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr) 515{ 516 unsigned long flags; 517 int ret; 518 519 local_irq_save(flags); 520 ret = __kgdb_notify(ptr, cmd); 521 local_irq_restore(flags); 522 523 return ret; 524} 525 526static struct notifier_block kgdb_notifier = { 527 .notifier_call = kgdb_notify, 528 529 /* 530 * Lowest-prio notifier priority, we want to be notified last: 531 */ 532 .priority = -INT_MAX, 533}; 534 535/** 536 * kgdb_arch_init - Perform any architecture specific initalization. 537 * 538 * This function will handle the initalization of any architecture 539 * specific callbacks. 540 */ 541int kgdb_arch_init(void) 542{ 543 return register_die_notifier(&kgdb_notifier); 544} 545 546/** 547 * kgdb_arch_exit - Perform any architecture specific uninitalization. 548 * 549 * This function will handle the uninitalization of any architecture 550 * specific callbacks, for dynamic registration and unregistration. 551 */ 552void kgdb_arch_exit(void) 553{ 554 unregister_die_notifier(&kgdb_notifier); 555} 556 557/** 558 * 559 * kgdb_skipexception - Bail out of KGDB when we've been triggered. 560 * @exception: Exception vector number 561 * @regs: Current &struct pt_regs. 562 * 563 * On some architectures we need to skip a breakpoint exception when 564 * it occurs after a breakpoint has been removed. 565 * 566 * Skip an int3 exception when it occurs after a breakpoint has been 567 * removed. Backtrack eip by 1 since the int3 would have caused it to 568 * increment by 1. 569 */ 570int kgdb_skipexception(int exception, struct pt_regs *regs) 571{ 572 if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) { 573 regs->ip -= 1; 574 return 1; 575 } 576 return 0; 577} 578 579unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs) 580{ 581 if (exception == 3) 582 return instruction_pointer(regs) - 1; 583 return instruction_pointer(regs); 584} 585 586struct kgdb_arch arch_kgdb_ops = { 587 /* Breakpoint instruction: */ 588 .gdb_bpt_instr = { 0xcc }, 589 .flags = KGDB_HW_BREAKPOINT, 590 .set_hw_breakpoint = kgdb_set_hw_break, 591 .remove_hw_breakpoint = kgdb_remove_hw_break, 592 .remove_all_hw_break = kgdb_remove_all_hw_break, 593 .correct_hw_break = kgdb_correct_hw_break, 594}; 595