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kgdb.c
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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 <[email protected]>
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<[email protected]>
26  * Updated by: Tom Rini <[email protected]>
27  * Updated by: Jason Wessel <[email protected]>
28  * Modified for 386 by Jim Kingdon, Cygnus Support.
29  * Origianl kgdb, compatibility with 2.1.xx kernel by
30  * David Grothe <[email protected]>
31  * Integrated into 2.2.5 kernel by Tigran Aivazian <[email protected]>
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 #include <linux/uaccess.h>
47 #include <linux/memory.h>
48 
49 #include <asm/debugreg.h>
50 #include <asm/apicdef.h>
51 #include <asm/apic.h>
52 #include <asm/nmi.h>
53 
54 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
55 {
56 #ifdef CONFIG_X86_32
57  { "ax", 4, offsetof(struct pt_regs, ax) },
58  { "cx", 4, offsetof(struct pt_regs, cx) },
59  { "dx", 4, offsetof(struct pt_regs, dx) },
60  { "bx", 4, offsetof(struct pt_regs, bx) },
61  { "sp", 4, offsetof(struct pt_regs, sp) },
62  { "bp", 4, offsetof(struct pt_regs, bp) },
63  { "si", 4, offsetof(struct pt_regs, si) },
64  { "di", 4, offsetof(struct pt_regs, di) },
65  { "ip", 4, offsetof(struct pt_regs, ip) },
66  { "flags", 4, offsetof(struct pt_regs, flags) },
67  { "cs", 4, offsetof(struct pt_regs, cs) },
68  { "ss", 4, offsetof(struct pt_regs, ss) },
69  { "ds", 4, offsetof(struct pt_regs, ds) },
70  { "es", 4, offsetof(struct pt_regs, es) },
71 #else
72  { "ax", 8, offsetof(struct pt_regs, ax) },
73  { "bx", 8, offsetof(struct pt_regs, bx) },
74  { "cx", 8, offsetof(struct pt_regs, cx) },
75  { "dx", 8, offsetof(struct pt_regs, dx) },
76  { "si", 8, offsetof(struct pt_regs, dx) },
77  { "di", 8, offsetof(struct pt_regs, di) },
78  { "bp", 8, offsetof(struct pt_regs, bp) },
79  { "sp", 8, offsetof(struct pt_regs, sp) },
80  { "r8", 8, offsetof(struct pt_regs, r8) },
81  { "r9", 8, offsetof(struct pt_regs, r9) },
82  { "r10", 8, offsetof(struct pt_regs, r10) },
83  { "r11", 8, offsetof(struct pt_regs, r11) },
84  { "r12", 8, offsetof(struct pt_regs, r12) },
85  { "r13", 8, offsetof(struct pt_regs, r13) },
86  { "r14", 8, offsetof(struct pt_regs, r14) },
87  { "r15", 8, offsetof(struct pt_regs, r15) },
88  { "ip", 8, offsetof(struct pt_regs, ip) },
89  { "flags", 4, offsetof(struct pt_regs, flags) },
90  { "cs", 4, offsetof(struct pt_regs, cs) },
91  { "ss", 4, offsetof(struct pt_regs, ss) },
92  { "ds", 4, -1 },
93  { "es", 4, -1 },
94 #endif
95  { "fs", 4, -1 },
96  { "gs", 4, -1 },
97 };
98 
99 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
100 {
101  if (
102 #ifdef CONFIG_X86_32
103  regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
104 #endif
105  regno == GDB_SP || regno == GDB_ORIG_AX)
106  return 0;
107 
108  if (dbg_reg_def[regno].offset != -1)
109  memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
110  dbg_reg_def[regno].size);
111  return 0;
112 }
113 
114 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
115 {
116  if (regno == GDB_ORIG_AX) {
117  memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
118  return "orig_ax";
119  }
120  if (regno >= DBG_MAX_REG_NUM || regno < 0)
121  return NULL;
122 
123  if (dbg_reg_def[regno].offset != -1)
124  memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
125  dbg_reg_def[regno].size);
126 
127 #ifdef CONFIG_X86_32
128  switch (regno) {
129  case GDB_SS:
130  if (!user_mode_vm(regs))
131  *(unsigned long *)mem = __KERNEL_DS;
132  break;
133  case GDB_SP:
134  if (!user_mode_vm(regs))
135  *(unsigned long *)mem = kernel_stack_pointer(regs);
136  break;
137  case GDB_GS:
138  case GDB_FS:
139  *(unsigned long *)mem = 0xFFFF;
140  break;
141  }
142 #endif
143  return dbg_reg_def[regno].name;
144 }
145 
158 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
159 {
160 #ifndef CONFIG_X86_32
161  u32 *gdb_regs32 = (u32 *)gdb_regs;
162 #endif
163  gdb_regs[GDB_AX] = 0;
164  gdb_regs[GDB_BX] = 0;
165  gdb_regs[GDB_CX] = 0;
166  gdb_regs[GDB_DX] = 0;
167  gdb_regs[GDB_SI] = 0;
168  gdb_regs[GDB_DI] = 0;
169  gdb_regs[GDB_BP] = *(unsigned long *)p->thread.sp;
170 #ifdef CONFIG_X86_32
171  gdb_regs[GDB_DS] = __KERNEL_DS;
172  gdb_regs[GDB_ES] = __KERNEL_DS;
173  gdb_regs[GDB_PS] = 0;
174  gdb_regs[GDB_CS] = __KERNEL_CS;
175  gdb_regs[GDB_PC] = p->thread.ip;
176  gdb_regs[GDB_SS] = __KERNEL_DS;
177  gdb_regs[GDB_FS] = 0xFFFF;
178  gdb_regs[GDB_GS] = 0xFFFF;
179 #else
180  gdb_regs32[GDB_PS] = *(unsigned long *)(p->thread.sp + 8);
181  gdb_regs32[GDB_CS] = __KERNEL_CS;
182  gdb_regs32[GDB_SS] = __KERNEL_DS;
183  gdb_regs[GDB_PC] = 0;
184  gdb_regs[GDB_R8] = 0;
185  gdb_regs[GDB_R9] = 0;
186  gdb_regs[GDB_R10] = 0;
187  gdb_regs[GDB_R11] = 0;
188  gdb_regs[GDB_R12] = 0;
189  gdb_regs[GDB_R13] = 0;
190  gdb_regs[GDB_R14] = 0;
191  gdb_regs[GDB_R15] = 0;
192 #endif
193  gdb_regs[GDB_SP] = p->thread.sp;
194 }
195 
196 static struct hw_breakpoint {
197  unsigned enabled;
198  unsigned long addr;
199  int len;
200  int type;
201  struct perf_event * __percpu *pev;
202 } breakinfo[HBP_NUM];
203 
204 static unsigned long early_dr7;
205 
206 static void kgdb_correct_hw_break(void)
207 {
208  int breakno;
209 
210  for (breakno = 0; breakno < HBP_NUM; breakno++) {
211  struct perf_event *bp;
212  struct arch_hw_breakpoint *info;
213  int val;
214  int cpu = raw_smp_processor_id();
215  if (!breakinfo[breakno].enabled)
216  continue;
217  if (dbg_is_early) {
218  set_debugreg(breakinfo[breakno].addr, breakno);
219  early_dr7 |= encode_dr7(breakno,
220  breakinfo[breakno].len,
221  breakinfo[breakno].type);
222  set_debugreg(early_dr7, 7);
223  continue;
224  }
225  bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
226  info = counter_arch_bp(bp);
227  if (bp->attr.disabled != 1)
228  continue;
229  bp->attr.bp_addr = breakinfo[breakno].addr;
230  bp->attr.bp_len = breakinfo[breakno].len;
231  bp->attr.bp_type = breakinfo[breakno].type;
232  info->address = breakinfo[breakno].addr;
233  info->len = breakinfo[breakno].len;
234  info->type = breakinfo[breakno].type;
235  val = arch_install_hw_breakpoint(bp);
236  if (!val)
237  bp->attr.disabled = 0;
238  }
239  if (!dbg_is_early)
240  hw_breakpoint_restore();
241 }
242 
243 static int hw_break_reserve_slot(int breakno)
244 {
245  int cpu;
246  int cnt = 0;
247  struct perf_event **pevent;
248 
249  if (dbg_is_early)
250  return 0;
251 
252  for_each_online_cpu(cpu) {
253  cnt++;
254  pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
255  if (dbg_reserve_bp_slot(*pevent))
256  goto fail;
257  }
258 
259  return 0;
260 
261 fail:
262  for_each_online_cpu(cpu) {
263  cnt--;
264  if (!cnt)
265  break;
266  pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
267  dbg_release_bp_slot(*pevent);
268  }
269  return -1;
270 }
271 
272 static int hw_break_release_slot(int breakno)
273 {
274  struct perf_event **pevent;
275  int cpu;
276 
277  if (dbg_is_early)
278  return 0;
279 
280  for_each_online_cpu(cpu) {
281  pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
282  if (dbg_release_bp_slot(*pevent))
283  /*
284  * The debugger is responsible for handing the retry on
285  * remove failure.
286  */
287  return -1;
288  }
289  return 0;
290 }
291 
292 static int
293 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
294 {
295  int i;
296 
297  for (i = 0; i < HBP_NUM; i++)
298  if (breakinfo[i].addr == addr && breakinfo[i].enabled)
299  break;
300  if (i == HBP_NUM)
301  return -1;
302 
303  if (hw_break_release_slot(i)) {
304  printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
305  return -1;
306  }
307  breakinfo[i].enabled = 0;
308 
309  return 0;
310 }
311 
312 static void kgdb_remove_all_hw_break(void)
313 {
314  int i;
315  int cpu = raw_smp_processor_id();
316  struct perf_event *bp;
317 
318  for (i = 0; i < HBP_NUM; i++) {
319  if (!breakinfo[i].enabled)
320  continue;
321  bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
322  if (!bp->attr.disabled) {
323  arch_uninstall_hw_breakpoint(bp);
324  bp->attr.disabled = 1;
325  continue;
326  }
327  if (dbg_is_early)
328  early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
329  breakinfo[i].type);
330  else if (hw_break_release_slot(i))
331  printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
332  breakinfo[i].addr);
333  breakinfo[i].enabled = 0;
334  }
335 }
336 
337 static int
338 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
339 {
340  int i;
341 
342  for (i = 0; i < HBP_NUM; i++)
343  if (!breakinfo[i].enabled)
344  break;
345  if (i == HBP_NUM)
346  return -1;
347 
348  switch (bptype) {
349  case BP_HARDWARE_BREAKPOINT:
350  len = 1;
351  breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
352  break;
353  case BP_WRITE_WATCHPOINT:
354  breakinfo[i].type = X86_BREAKPOINT_WRITE;
355  break;
356  case BP_ACCESS_WATCHPOINT:
357  breakinfo[i].type = X86_BREAKPOINT_RW;
358  break;
359  default:
360  return -1;
361  }
362  switch (len) {
363  case 1:
364  breakinfo[i].len = X86_BREAKPOINT_LEN_1;
365  break;
366  case 2:
367  breakinfo[i].len = X86_BREAKPOINT_LEN_2;
368  break;
369  case 4:
370  breakinfo[i].len = X86_BREAKPOINT_LEN_4;
371  break;
372 #ifdef CONFIG_X86_64
373  case 8:
374  breakinfo[i].len = X86_BREAKPOINT_LEN_8;
375  break;
376 #endif
377  default:
378  return -1;
379  }
380  breakinfo[i].addr = addr;
381  if (hw_break_reserve_slot(i)) {
382  breakinfo[i].addr = 0;
383  return -1;
384  }
385  breakinfo[i].enabled = 1;
386 
387  return 0;
388 }
389 
398 static void kgdb_disable_hw_debug(struct pt_regs *regs)
399 {
400  int i;
401  int cpu = raw_smp_processor_id();
402  struct perf_event *bp;
403 
404  /* Disable hardware debugging while we are in kgdb: */
405  set_debugreg(0UL, 7);
406  for (i = 0; i < HBP_NUM; i++) {
407  if (!breakinfo[i].enabled)
408  continue;
409  if (dbg_is_early) {
410  early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
411  breakinfo[i].type);
412  continue;
413  }
414  bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
415  if (bp->attr.disabled == 1)
416  continue;
417  arch_uninstall_hw_breakpoint(bp);
418  bp->attr.disabled = 1;
419  }
420 }
421 
422 #ifdef CONFIG_SMP
423 
439 void kgdb_roundup_cpus(unsigned long flags)
440 {
441  apic->send_IPI_allbutself(APIC_DM_NMI);
442 }
443 #endif
444 
461 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
462  char *remcomInBuffer, char *remcomOutBuffer,
463  struct pt_regs *linux_regs)
464 {
465  unsigned long addr;
466  char *ptr;
467 
468  switch (remcomInBuffer[0]) {
469  case 'c':
470  case 's':
471  /* try to read optional parameter, pc unchanged if no parm */
472  ptr = &remcomInBuffer[1];
473  if (kgdb_hex2long(&ptr, &addr))
474  linux_regs->ip = addr;
475  case 'D':
476  case 'k':
477  /* clear the trace bit */
478  linux_regs->flags &= ~X86_EFLAGS_TF;
479  atomic_set(&kgdb_cpu_doing_single_step, -1);
480 
481  /* set the trace bit if we're stepping */
482  if (remcomInBuffer[0] == 's') {
483  linux_regs->flags |= X86_EFLAGS_TF;
484  atomic_set(&kgdb_cpu_doing_single_step,
485  raw_smp_processor_id());
486  }
487 
488  return 0;
489  }
490 
491  /* this means that we do not want to exit from the handler: */
492  return -1;
493 }
494 
495 static inline int
496 single_step_cont(struct pt_regs *regs, struct die_args *args)
497 {
498  /*
499  * Single step exception from kernel space to user space so
500  * eat the exception and continue the process:
501  */
502  printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
503  "resuming...\n");
504  kgdb_arch_handle_exception(args->trapnr, args->signr,
505  args->err, "c", "", regs);
506  /*
507  * Reset the BS bit in dr6 (pointed by args->err) to
508  * denote completion of processing
509  */
510  (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
511 
512  return NOTIFY_STOP;
513 }
514 
515 static int was_in_debug_nmi[NR_CPUS];
516 
517 static int kgdb_nmi_handler(unsigned int cmd, struct pt_regs *regs)
518 {
519  switch (cmd) {
520  case NMI_LOCAL:
521  if (atomic_read(&kgdb_active) != -1) {
522  /* KGDB CPU roundup */
523  kgdb_nmicallback(raw_smp_processor_id(), regs);
524  was_in_debug_nmi[raw_smp_processor_id()] = 1;
525  touch_nmi_watchdog();
526  return NMI_HANDLED;
527  }
528  break;
529 
530  case NMI_UNKNOWN:
531  if (was_in_debug_nmi[raw_smp_processor_id()]) {
532  was_in_debug_nmi[raw_smp_processor_id()] = 0;
533  return NMI_HANDLED;
534  }
535  break;
536  default:
537  /* do nothing */
538  break;
539  }
540  return NMI_DONE;
541 }
542 
543 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
544 {
545  struct pt_regs *regs = args->regs;
546 
547  switch (cmd) {
548  case DIE_DEBUG:
549  if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
550  if (user_mode(regs))
551  return single_step_cont(regs, args);
552  break;
553  } else if (test_thread_flag(TIF_SINGLESTEP))
554  /* This means a user thread is single stepping
555  * a system call which should be ignored
556  */
557  return NOTIFY_DONE;
558  /* fall through */
559  default:
560  if (user_mode(regs))
561  return NOTIFY_DONE;
562  }
563 
564  if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
565  return NOTIFY_DONE;
566 
567  /* Must touch watchdog before return to normal operation */
568  touch_nmi_watchdog();
569  return NOTIFY_STOP;
570 }
571 
572 int kgdb_ll_trap(int cmd, const char *str,
573  struct pt_regs *regs, long err, int trap, int sig)
574 {
575  struct die_args args = {
576  .regs = regs,
577  .str = str,
578  .err = err,
579  .trapnr = trap,
580  .signr = sig,
581 
582  };
583 
584  if (!kgdb_io_module_registered)
585  return NOTIFY_DONE;
586 
587  return __kgdb_notify(&args, cmd);
588 }
589 
590 static int
591 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
592 {
593  unsigned long flags;
594  int ret;
595 
596  local_irq_save(flags);
597  ret = __kgdb_notify(ptr, cmd);
598  local_irq_restore(flags);
599 
600  return ret;
601 }
602 
603 static struct notifier_block kgdb_notifier = {
604  .notifier_call = kgdb_notify,
605 };
606 
613 int kgdb_arch_init(void)
614 {
615  int retval;
616 
617  retval = register_die_notifier(&kgdb_notifier);
618  if (retval)
619  goto out;
620 
621  retval = register_nmi_handler(NMI_LOCAL, kgdb_nmi_handler,
622  0, "kgdb");
623  if (retval)
624  goto out1;
625 
626  retval = register_nmi_handler(NMI_UNKNOWN, kgdb_nmi_handler,
627  0, "kgdb");
628 
629  if (retval)
630  goto out2;
631 
632  return retval;
633 
634 out2:
635  unregister_nmi_handler(NMI_LOCAL, "kgdb");
636 out1:
637  unregister_die_notifier(&kgdb_notifier);
638 out:
639  return retval;
640 }
641 
642 static void kgdb_hw_overflow_handler(struct perf_event *event,
643  struct perf_sample_data *data, struct pt_regs *regs)
644 {
645  struct task_struct *tsk = current;
646  int i;
647 
648  for (i = 0; i < 4; i++)
649  if (breakinfo[i].enabled)
650  tsk->thread.debugreg6 |= (DR_TRAP0 << i);
651 }
652 
653 void kgdb_arch_late(void)
654 {
655  int i, cpu;
656  struct perf_event_attr attr;
657  struct perf_event **pevent;
658 
659  /*
660  * Pre-allocate the hw breakpoint structions in the non-atomic
661  * portion of kgdb because this operation requires mutexs to
662  * complete.
663  */
664  hw_breakpoint_init(&attr);
665  attr.bp_addr = (unsigned long)kgdb_arch_init;
666  attr.bp_len = HW_BREAKPOINT_LEN_1;
667  attr.bp_type = HW_BREAKPOINT_W;
668  attr.disabled = 1;
669  for (i = 0; i < HBP_NUM; i++) {
670  if (breakinfo[i].pev)
671  continue;
672  breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
673  if (IS_ERR((void * __force)breakinfo[i].pev)) {
674  printk(KERN_ERR "kgdb: Could not allocate hw"
675  "breakpoints\nDisabling the kernel debugger\n");
676  breakinfo[i].pev = NULL;
677  kgdb_arch_exit();
678  return;
679  }
680  for_each_online_cpu(cpu) {
681  pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
682  pevent[0]->hw.sample_period = 1;
683  pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
684  if (pevent[0]->destroy != NULL) {
685  pevent[0]->destroy = NULL;
686  release_bp_slot(*pevent);
687  }
688  }
689  }
690 }
691 
698 void kgdb_arch_exit(void)
699 {
700  int i;
701  for (i = 0; i < 4; i++) {
702  if (breakinfo[i].pev) {
703  unregister_wide_hw_breakpoint(breakinfo[i].pev);
704  breakinfo[i].pev = NULL;
705  }
706  }
707  unregister_nmi_handler(NMI_UNKNOWN, "kgdb");
708  unregister_nmi_handler(NMI_LOCAL, "kgdb");
709  unregister_die_notifier(&kgdb_notifier);
710 }
711 
725 int kgdb_skipexception(int exception, struct pt_regs *regs)
726 {
727  if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
728  regs->ip -= 1;
729  return 1;
730  }
731  return 0;
732 }
733 
734 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
735 {
736  if (exception == 3)
737  return instruction_pointer(regs) - 1;
738  return instruction_pointer(regs);
739 }
740 
741 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
742 {
743  regs->ip = ip;
744 }
745 
746 int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
747 {
748  int err;
749 #ifdef CONFIG_DEBUG_RODATA
750  char opc[BREAK_INSTR_SIZE];
751 #endif /* CONFIG_DEBUG_RODATA */
752 
753  bpt->type = BP_BREAKPOINT;
754  err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
755  BREAK_INSTR_SIZE);
756  if (err)
757  return err;
758  err = probe_kernel_write((char *)bpt->bpt_addr,
759  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
760 #ifdef CONFIG_DEBUG_RODATA
761  if (!err)
762  return err;
763  /*
764  * It is safe to call text_poke() because normal kernel execution
765  * is stopped on all cores, so long as the text_mutex is not locked.
766  */
767  if (mutex_is_locked(&text_mutex))
768  return -EBUSY;
769  text_poke((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
770  BREAK_INSTR_SIZE);
771  err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
772  if (err)
773  return err;
774  if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))
775  return -EINVAL;
776  bpt->type = BP_POKE_BREAKPOINT;
777 #endif /* CONFIG_DEBUG_RODATA */
778  return err;
779 }
780 
781 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
782 {
783 #ifdef CONFIG_DEBUG_RODATA
784  int err;
785  char opc[BREAK_INSTR_SIZE];
786 
787  if (bpt->type != BP_POKE_BREAKPOINT)
788  goto knl_write;
789  /*
790  * It is safe to call text_poke() because normal kernel execution
791  * is stopped on all cores, so long as the text_mutex is not locked.
792  */
793  if (mutex_is_locked(&text_mutex))
794  goto knl_write;
795  text_poke((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE);
796  err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
797  if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
798  goto knl_write;
799  return err;
800 knl_write:
801 #endif /* CONFIG_DEBUG_RODATA */
802  return probe_kernel_write((char *)bpt->bpt_addr,
803  (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
804 }
805 
806 struct kgdb_arch arch_kgdb_ops = {
807  /* Breakpoint instruction: */
808  .gdb_bpt_instr = { 0xcc },
809  .flags = KGDB_HW_BREAKPOINT,
810  .set_hw_breakpoint = kgdb_set_hw_break,
811  .remove_hw_breakpoint = kgdb_remove_hw_break,
812  .disable_hw_break = kgdb_disable_hw_debug,
813  .remove_all_hw_break = kgdb_remove_all_hw_break,
814  .correct_hw_break = kgdb_correct_hw_break,
815 };
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