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Linux/arch/x86/kernel/kgdb.c

Version: ~ [ linux-5.12-rc7 ] ~ [ linux-5.11.13 ] ~ [ linux-5.10.29 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.111 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.186 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.230 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.266 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.266 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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/smp.h>
 43 #include <linux/nmi.h>
 44 #include <linux/hw_breakpoint.h>
 45 #include <linux/uaccess.h>
 46 #include <linux/memory.h>
 47 
 48 #include <asm/debugreg.h>
 49 #include <asm/apicdef.h>
 50 #include <asm/apic.h>
 51 #include <asm/nmi.h>
 52 
 53 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
 54 {
 55 #ifdef CONFIG_X86_32
 56         { "ax", 4, offsetof(struct pt_regs, ax) },
 57         { "cx", 4, offsetof(struct pt_regs, cx) },
 58         { "dx", 4, offsetof(struct pt_regs, dx) },
 59         { "bx", 4, offsetof(struct pt_regs, bx) },
 60         { "sp", 4, offsetof(struct pt_regs, sp) },
 61         { "bp", 4, offsetof(struct pt_regs, bp) },
 62         { "si", 4, offsetof(struct pt_regs, si) },
 63         { "di", 4, offsetof(struct pt_regs, di) },
 64         { "ip", 4, offsetof(struct pt_regs, ip) },
 65         { "flags", 4, offsetof(struct pt_regs, flags) },
 66         { "cs", 4, offsetof(struct pt_regs, cs) },
 67         { "ss", 4, offsetof(struct pt_regs, ss) },
 68         { "ds", 4, offsetof(struct pt_regs, ds) },
 69         { "es", 4, offsetof(struct pt_regs, es) },
 70 #else
 71         { "ax", 8, offsetof(struct pt_regs, ax) },
 72         { "bx", 8, offsetof(struct pt_regs, bx) },
 73         { "cx", 8, offsetof(struct pt_regs, cx) },
 74         { "dx", 8, offsetof(struct pt_regs, dx) },
 75         { "si", 8, offsetof(struct pt_regs, dx) },
 76         { "di", 8, offsetof(struct pt_regs, di) },
 77         { "bp", 8, offsetof(struct pt_regs, bp) },
 78         { "sp", 8, offsetof(struct pt_regs, sp) },
 79         { "r8", 8, offsetof(struct pt_regs, r8) },
 80         { "r9", 8, offsetof(struct pt_regs, r9) },
 81         { "r10", 8, offsetof(struct pt_regs, r10) },
 82         { "r11", 8, offsetof(struct pt_regs, r11) },
 83         { "r12", 8, offsetof(struct pt_regs, r12) },
 84         { "r13", 8, offsetof(struct pt_regs, r13) },
 85         { "r14", 8, offsetof(struct pt_regs, r14) },
 86         { "r15", 8, offsetof(struct pt_regs, r15) },
 87         { "ip", 8, offsetof(struct pt_regs, ip) },
 88         { "flags", 4, offsetof(struct pt_regs, flags) },
 89         { "cs", 4, offsetof(struct pt_regs, cs) },
 90         { "ss", 4, offsetof(struct pt_regs, ss) },
 91         { "ds", 4, -1 },
 92         { "es", 4, -1 },
 93 #endif
 94         { "fs", 4, -1 },
 95         { "gs", 4, -1 },
 96 };
 97 
 98 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 99 {
100         if (
101 #ifdef CONFIG_X86_32
102             regno == GDB_SS || regno == GDB_FS || regno == GDB_GS ||
103 #endif
104             regno == GDB_SP || regno == GDB_ORIG_AX)
105                 return 0;
106 
107         if (dbg_reg_def[regno].offset != -1)
108                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
109                        dbg_reg_def[regno].size);
110         return 0;
111 }
112 
113 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
114 {
115         if (regno == GDB_ORIG_AX) {
116                 memcpy(mem, &regs->orig_ax, sizeof(regs->orig_ax));
117                 return "orig_ax";
118         }
119         if (regno >= DBG_MAX_REG_NUM || regno < 0)
120                 return NULL;
121 
122         if (dbg_reg_def[regno].offset != -1)
123                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
124                        dbg_reg_def[regno].size);
125 
126 #ifdef CONFIG_X86_32
127         switch (regno) {
128         case GDB_SS:
129                 if (!user_mode_vm(regs))
130                         *(unsigned long *)mem = __KERNEL_DS;
131                 break;
132         case GDB_SP:
133                 if (!user_mode_vm(regs))
134                         *(unsigned long *)mem = kernel_stack_pointer(regs);
135                 break;
136         case GDB_GS:
137         case GDB_FS:
138                 *(unsigned long *)mem = 0xFFFF;
139                 break;
140         }
141 #endif
142         return dbg_reg_def[regno].name;
143 }
144 
145 /**
146  *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
147  *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
148  *      @p: The &struct task_struct of the desired process.
149  *
150  *      Convert the register values of the sleeping process in @p to
151  *      the format that GDB expects.
152  *      This function is called when kgdb does not have access to the
153  *      &struct pt_regs and therefore it should fill the gdb registers
154  *      @gdb_regs with what has been saved in &struct thread_struct
155  *      thread field during switch_to.
156  */
157 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
158 {
159 #ifndef CONFIG_X86_32
160         u32 *gdb_regs32 = (u32 *)gdb_regs;
161 #endif
162         gdb_regs[GDB_AX]        = 0;
163         gdb_regs[GDB_BX]        = 0;
164         gdb_regs[GDB_CX]        = 0;
165         gdb_regs[GDB_DX]        = 0;
166         gdb_regs[GDB_SI]        = 0;
167         gdb_regs[GDB_DI]        = 0;
168         gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
169 #ifdef CONFIG_X86_32
170         gdb_regs[GDB_DS]        = __KERNEL_DS;
171         gdb_regs[GDB_ES]        = __KERNEL_DS;
172         gdb_regs[GDB_PS]        = 0;
173         gdb_regs[GDB_CS]        = __KERNEL_CS;
174         gdb_regs[GDB_PC]        = p->thread.ip;
175         gdb_regs[GDB_SS]        = __KERNEL_DS;
176         gdb_regs[GDB_FS]        = 0xFFFF;
177         gdb_regs[GDB_GS]        = 0xFFFF;
178 #else
179         gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
180         gdb_regs32[GDB_CS]      = __KERNEL_CS;
181         gdb_regs32[GDB_SS]      = __KERNEL_DS;
182         gdb_regs[GDB_PC]        = 0;
183         gdb_regs[GDB_R8]        = 0;
184         gdb_regs[GDB_R9]        = 0;
185         gdb_regs[GDB_R10]       = 0;
186         gdb_regs[GDB_R11]       = 0;
187         gdb_regs[GDB_R12]       = 0;
188         gdb_regs[GDB_R13]       = 0;
189         gdb_regs[GDB_R14]       = 0;
190         gdb_regs[GDB_R15]       = 0;
191 #endif
192         gdb_regs[GDB_SP]        = p->thread.sp;
193 }
194 
195 static struct hw_breakpoint {
196         unsigned                enabled;
197         unsigned long           addr;
198         int                     len;
199         int                     type;
200         struct perf_event       * __percpu *pev;
201 } breakinfo[HBP_NUM];
202 
203 static unsigned long early_dr7;
204 
205 static void kgdb_correct_hw_break(void)
206 {
207         int breakno;
208 
209         for (breakno = 0; breakno < HBP_NUM; breakno++) {
210                 struct perf_event *bp;
211                 struct arch_hw_breakpoint *info;
212                 int val;
213                 int cpu = raw_smp_processor_id();
214                 if (!breakinfo[breakno].enabled)
215                         continue;
216                 if (dbg_is_early) {
217                         set_debugreg(breakinfo[breakno].addr, breakno);
218                         early_dr7 |= encode_dr7(breakno,
219                                                 breakinfo[breakno].len,
220                                                 breakinfo[breakno].type);
221                         set_debugreg(early_dr7, 7);
222                         continue;
223                 }
224                 bp = *per_cpu_ptr(breakinfo[breakno].pev, cpu);
225                 info = counter_arch_bp(bp);
226                 if (bp->attr.disabled != 1)
227                         continue;
228                 bp->attr.bp_addr = breakinfo[breakno].addr;
229                 bp->attr.bp_len = breakinfo[breakno].len;
230                 bp->attr.bp_type = breakinfo[breakno].type;
231                 info->address = breakinfo[breakno].addr;
232                 info->len = breakinfo[breakno].len;
233                 info->type = breakinfo[breakno].type;
234                 val = arch_install_hw_breakpoint(bp);
235                 if (!val)
236                         bp->attr.disabled = 0;
237         }
238         if (!dbg_is_early)
239                 hw_breakpoint_restore();
240 }
241 
242 static int hw_break_reserve_slot(int breakno)
243 {
244         int cpu;
245         int cnt = 0;
246         struct perf_event **pevent;
247 
248         if (dbg_is_early)
249                 return 0;
250 
251         for_each_online_cpu(cpu) {
252                 cnt++;
253                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
254                 if (dbg_reserve_bp_slot(*pevent))
255                         goto fail;
256         }
257 
258         return 0;
259 
260 fail:
261         for_each_online_cpu(cpu) {
262                 cnt--;
263                 if (!cnt)
264                         break;
265                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
266                 dbg_release_bp_slot(*pevent);
267         }
268         return -1;
269 }
270 
271 static int hw_break_release_slot(int breakno)
272 {
273         struct perf_event **pevent;
274         int cpu;
275 
276         if (dbg_is_early)
277                 return 0;
278 
279         for_each_online_cpu(cpu) {
280                 pevent = per_cpu_ptr(breakinfo[breakno].pev, cpu);
281                 if (dbg_release_bp_slot(*pevent))
282                         /*
283                          * The debugger is responsible for handing the retry on
284                          * remove failure.
285                          */
286                         return -1;
287         }
288         return 0;
289 }
290 
291 static int
292 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
293 {
294         int i;
295 
296         for (i = 0; i < HBP_NUM; i++)
297                 if (breakinfo[i].addr == addr && breakinfo[i].enabled)
298                         break;
299         if (i == HBP_NUM)
300                 return -1;
301 
302         if (hw_break_release_slot(i)) {
303                 printk(KERN_ERR "Cannot remove hw breakpoint at %lx\n", addr);
304                 return -1;
305         }
306         breakinfo[i].enabled = 0;
307 
308         return 0;
309 }
310 
311 static void kgdb_remove_all_hw_break(void)
312 {
313         int i;
314         int cpu = raw_smp_processor_id();
315         struct perf_event *bp;
316 
317         for (i = 0; i < HBP_NUM; i++) {
318                 if (!breakinfo[i].enabled)
319                         continue;
320                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
321                 if (!bp->attr.disabled) {
322                         arch_uninstall_hw_breakpoint(bp);
323                         bp->attr.disabled = 1;
324                         continue;
325                 }
326                 if (dbg_is_early)
327                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
328                                                  breakinfo[i].type);
329                 else if (hw_break_release_slot(i))
330                         printk(KERN_ERR "KGDB: hw bpt remove failed %lx\n",
331                                breakinfo[i].addr);
332                 breakinfo[i].enabled = 0;
333         }
334 }
335 
336 static int
337 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
338 {
339         int i;
340 
341         for (i = 0; i < HBP_NUM; i++)
342                 if (!breakinfo[i].enabled)
343                         break;
344         if (i == HBP_NUM)
345                 return -1;
346 
347         switch (bptype) {
348         case BP_HARDWARE_BREAKPOINT:
349                 len = 1;
350                 breakinfo[i].type = X86_BREAKPOINT_EXECUTE;
351                 break;
352         case BP_WRITE_WATCHPOINT:
353                 breakinfo[i].type = X86_BREAKPOINT_WRITE;
354                 break;
355         case BP_ACCESS_WATCHPOINT:
356                 breakinfo[i].type = X86_BREAKPOINT_RW;
357                 break;
358         default:
359                 return -1;
360         }
361         switch (len) {
362         case 1:
363                 breakinfo[i].len = X86_BREAKPOINT_LEN_1;
364                 break;
365         case 2:
366                 breakinfo[i].len = X86_BREAKPOINT_LEN_2;
367                 break;
368         case 4:
369                 breakinfo[i].len = X86_BREAKPOINT_LEN_4;
370                 break;
371 #ifdef CONFIG_X86_64
372         case 8:
373                 breakinfo[i].len = X86_BREAKPOINT_LEN_8;
374                 break;
375 #endif
376         default:
377                 return -1;
378         }
379         breakinfo[i].addr = addr;
380         if (hw_break_reserve_slot(i)) {
381                 breakinfo[i].addr = 0;
382                 return -1;
383         }
384         breakinfo[i].enabled = 1;
385 
386         return 0;
387 }
388 
389 /**
390  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
391  *      @regs: Current &struct pt_regs.
392  *
393  *      This function will be called if the particular architecture must
394  *      disable hardware debugging while it is processing gdb packets or
395  *      handling exception.
396  */
397 static void kgdb_disable_hw_debug(struct pt_regs *regs)
398 {
399         int i;
400         int cpu = raw_smp_processor_id();
401         struct perf_event *bp;
402 
403         /* Disable hardware debugging while we are in kgdb: */
404         set_debugreg(0UL, 7);
405         for (i = 0; i < HBP_NUM; i++) {
406                 if (!breakinfo[i].enabled)
407                         continue;
408                 if (dbg_is_early) {
409                         early_dr7 &= ~encode_dr7(i, breakinfo[i].len,
410                                                  breakinfo[i].type);
411                         continue;
412                 }
413                 bp = *per_cpu_ptr(breakinfo[i].pev, cpu);
414                 if (bp->attr.disabled == 1)
415                         continue;
416                 arch_uninstall_hw_breakpoint(bp);
417                 bp->attr.disabled = 1;
418         }
419 }
420 
421 #ifdef CONFIG_SMP
422 /**
423  *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
424  *      @flags: Current IRQ state
425  *
426  *      On SMP systems, we need to get the attention of the other CPUs
427  *      and get them be in a known state.  This should do what is needed
428  *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
429  *      the NMI approach is not used for rounding up all the CPUs. For example,
430  *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
431  *      this case, we have to make sure that interrupts are enabled before
432  *      calling smp_call_function(). The argument to this function is
433  *      the flags that will be used when restoring the interrupts. There is
434  *      local_irq_save() call before kgdb_roundup_cpus().
435  *
436  *      On non-SMP systems, this is not called.
437  */
438 void kgdb_roundup_cpus(unsigned long flags)
439 {
440         apic->send_IPI_allbutself(APIC_DM_NMI);
441 }
442 #endif
443 
444 /**
445  *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
446  *      @e_vector: The error vector of the exception that happened.
447  *      @signo: The signal number of the exception that happened.
448  *      @err_code: The error code of the exception that happened.
449  *      @remcomInBuffer: The buffer of the packet we have read.
450  *      @remcomOutBuffer: The buffer of %BUFMAX bytes to write a packet into.
451  *      @linux_regs: The &struct pt_regs of the current process.
452  *
453  *      This function MUST handle the 'c' and 's' command packets,
454  *      as well packets to set / remove a hardware breakpoint, if used.
455  *      If there are additional packets which the hardware needs to handle,
456  *      they are handled here.  The code should return -1 if it wants to
457  *      process more packets, and a %0 or %1 if it wants to exit from the
458  *      kgdb callback.
459  */
460 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
461                                char *remcomInBuffer, char *remcomOutBuffer,
462                                struct pt_regs *linux_regs)
463 {
464         unsigned long addr;
465         char *ptr;
466 
467         switch (remcomInBuffer[0]) {
468         case 'c':
469         case 's':
470                 /* try to read optional parameter, pc unchanged if no parm */
471                 ptr = &remcomInBuffer[1];
472                 if (kgdb_hex2long(&ptr, &addr))
473                         linux_regs->ip = addr;
474         case 'D':
475         case 'k':
476                 /* clear the trace bit */
477                 linux_regs->flags &= ~X86_EFLAGS_TF;
478                 atomic_set(&kgdb_cpu_doing_single_step, -1);
479 
480                 /* set the trace bit if we're stepping */
481                 if (remcomInBuffer[0] == 's') {
482                         linux_regs->flags |= X86_EFLAGS_TF;
483                         atomic_set(&kgdb_cpu_doing_single_step,
484                                    raw_smp_processor_id());
485                 }
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_nmi_handler(unsigned int cmd, struct pt_regs *regs)
517 {
518         switch (cmd) {
519         case NMI_LOCAL:
520                 if (atomic_read(&kgdb_active) != -1) {
521                         /* KGDB CPU roundup */
522                         kgdb_nmicallback(raw_smp_processor_id(), regs);
523                         was_in_debug_nmi[raw_smp_processor_id()] = 1;
524                         touch_nmi_watchdog();
525                         return NMI_HANDLED;
526                 }
527                 break;
528 
529         case NMI_UNKNOWN:
530                 if (was_in_debug_nmi[raw_smp_processor_id()]) {
531                         was_in_debug_nmi[raw_smp_processor_id()] = 0;
532                         return NMI_HANDLED;
533                 }
534                 break;
535         default:
536                 /* do nothing */
537                 break;
538         }
539         return NMI_DONE;
540 }
541 
542 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
543 {
544         struct pt_regs *regs = args->regs;
545 
546         switch (cmd) {
547         case DIE_DEBUG:
548                 if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
549                         if (user_mode(regs))
550                                 return single_step_cont(regs, args);
551                         break;
552                 } else if (test_thread_flag(TIF_SINGLESTEP))
553                         /* This means a user thread is single stepping
554                          * a system call which should be ignored
555                          */
556                         return NOTIFY_DONE;
557                 /* fall through */
558         default:
559                 if (user_mode(regs))
560                         return NOTIFY_DONE;
561         }
562 
563         if (kgdb_handle_exception(args->trapnr, args->signr, cmd, regs))
564                 return NOTIFY_DONE;
565 
566         /* Must touch watchdog before return to normal operation */
567         touch_nmi_watchdog();
568         return NOTIFY_STOP;
569 }
570 
571 int kgdb_ll_trap(int cmd, const char *str,
572                  struct pt_regs *regs, long err, int trap, int sig)
573 {
574         struct die_args args = {
575                 .regs   = regs,
576                 .str    = str,
577                 .err    = err,
578                 .trapnr = trap,
579                 .signr  = sig,
580 
581         };
582 
583         if (!kgdb_io_module_registered)
584                 return NOTIFY_DONE;
585 
586         return __kgdb_notify(&args, cmd);
587 }
588 
589 static int
590 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
591 {
592         unsigned long flags;
593         int ret;
594 
595         local_irq_save(flags);
596         ret = __kgdb_notify(ptr, cmd);
597         local_irq_restore(flags);
598 
599         return ret;
600 }
601 
602 static struct notifier_block kgdb_notifier = {
603         .notifier_call  = kgdb_notify,
604 };
605 
606 /**
607  *      kgdb_arch_init - Perform any architecture specific initalization.
608  *
609  *      This function will handle the initalization of any architecture
610  *      specific callbacks.
611  */
612 int kgdb_arch_init(void)
613 {
614         int retval;
615 
616         retval = register_die_notifier(&kgdb_notifier);
617         if (retval)
618                 goto out;
619 
620         retval = register_nmi_handler(NMI_LOCAL, kgdb_nmi_handler,
621                                         0, "kgdb");
622         if (retval)
623                 goto out1;
624 
625         retval = register_nmi_handler(NMI_UNKNOWN, kgdb_nmi_handler,
626                                         0, "kgdb");
627 
628         if (retval)
629                 goto out2;
630 
631         return retval;
632 
633 out2:
634         unregister_nmi_handler(NMI_LOCAL, "kgdb");
635 out1:
636         unregister_die_notifier(&kgdb_notifier);
637 out:
638         return retval;
639 }
640 
641 static void kgdb_hw_overflow_handler(struct perf_event *event,
642                 struct perf_sample_data *data, struct pt_regs *regs)
643 {
644         struct task_struct *tsk = current;
645         int i;
646 
647         for (i = 0; i < 4; i++)
648                 if (breakinfo[i].enabled)
649                         tsk->thread.debugreg6 |= (DR_TRAP0 << i);
650 }
651 
652 void kgdb_arch_late(void)
653 {
654         int i, cpu;
655         struct perf_event_attr attr;
656         struct perf_event **pevent;
657 
658         /*
659          * Pre-allocate the hw breakpoint structions in the non-atomic
660          * portion of kgdb because this operation requires mutexs to
661          * complete.
662          */
663         hw_breakpoint_init(&attr);
664         attr.bp_addr = (unsigned long)kgdb_arch_init;
665         attr.bp_len = HW_BREAKPOINT_LEN_1;
666         attr.bp_type = HW_BREAKPOINT_W;
667         attr.disabled = 1;
668         for (i = 0; i < HBP_NUM; i++) {
669                 if (breakinfo[i].pev)
670                         continue;
671                 breakinfo[i].pev = register_wide_hw_breakpoint(&attr, NULL, NULL);
672                 if (IS_ERR((void * __force)breakinfo[i].pev)) {
673                         printk(KERN_ERR "kgdb: Could not allocate hw"
674                                "breakpoints\nDisabling the kernel debugger\n");
675                         breakinfo[i].pev = NULL;
676                         kgdb_arch_exit();
677                         return;
678                 }
679                 for_each_online_cpu(cpu) {
680                         pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
681                         pevent[0]->hw.sample_period = 1;
682                         pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
683                         if (pevent[0]->destroy != NULL) {
684                                 pevent[0]->destroy = NULL;
685                                 release_bp_slot(*pevent);
686                         }
687                 }
688         }
689 }
690 
691 /**
692  *      kgdb_arch_exit - Perform any architecture specific uninitalization.
693  *
694  *      This function will handle the uninitalization of any architecture
695  *      specific callbacks, for dynamic registration and unregistration.
696  */
697 void kgdb_arch_exit(void)
698 {
699         int i;
700         for (i = 0; i < 4; i++) {
701                 if (breakinfo[i].pev) {
702                         unregister_wide_hw_breakpoint(breakinfo[i].pev);
703                         breakinfo[i].pev = NULL;
704                 }
705         }
706         unregister_nmi_handler(NMI_UNKNOWN, "kgdb");
707         unregister_nmi_handler(NMI_LOCAL, "kgdb");
708         unregister_die_notifier(&kgdb_notifier);
709 }
710 
711 /**
712  *
713  *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
714  *      @exception: Exception vector number
715  *      @regs: Current &struct pt_regs.
716  *
717  *      On some architectures we need to skip a breakpoint exception when
718  *      it occurs after a breakpoint has been removed.
719  *
720  * Skip an int3 exception when it occurs after a breakpoint has been
721  * removed. Backtrack eip by 1 since the int3 would have caused it to
722  * increment by 1.
723  */
724 int kgdb_skipexception(int exception, struct pt_regs *regs)
725 {
726         if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
727                 regs->ip -= 1;
728                 return 1;
729         }
730         return 0;
731 }
732 
733 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
734 {
735         if (exception == 3)
736                 return instruction_pointer(regs) - 1;
737         return instruction_pointer(regs);
738 }
739 
740 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
741 {
742         regs->ip = ip;
743 }
744 
745 int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
746 {
747         int err;
748 #ifdef CONFIG_DEBUG_RODATA
749         char opc[BREAK_INSTR_SIZE];
750 #endif /* CONFIG_DEBUG_RODATA */
751 
752         bpt->type = BP_BREAKPOINT;
753         err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
754                                 BREAK_INSTR_SIZE);
755         if (err)
756                 return err;
757         err = probe_kernel_write((char *)bpt->bpt_addr,
758                                  arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
759 #ifdef CONFIG_DEBUG_RODATA
760         if (!err)
761                 return err;
762         /*
763          * It is safe to call text_poke() because normal kernel execution
764          * is stopped on all cores, so long as the text_mutex is not locked.
765          */
766         if (mutex_is_locked(&text_mutex))
767                 return -EBUSY;
768         text_poke((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
769                   BREAK_INSTR_SIZE);
770         err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
771         if (err)
772                 return err;
773         if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))
774                 return -EINVAL;
775         bpt->type = BP_POKE_BREAKPOINT;
776 #endif /* CONFIG_DEBUG_RODATA */
777         return err;
778 }
779 
780 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
781 {
782 #ifdef CONFIG_DEBUG_RODATA
783         int err;
784         char opc[BREAK_INSTR_SIZE];
785 
786         if (bpt->type != BP_POKE_BREAKPOINT)
787                 goto knl_write;
788         /*
789          * It is safe to call text_poke() because normal kernel execution
790          * is stopped on all cores, so long as the text_mutex is not locked.
791          */
792         if (mutex_is_locked(&text_mutex))
793                 goto knl_write;
794         text_poke((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE);
795         err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
796         if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
797                 goto knl_write;
798         return err;
799 knl_write:
800 #endif /* CONFIG_DEBUG_RODATA */
801         return probe_kernel_write((char *)bpt->bpt_addr,
802                                   (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
803 }
804 
805 struct kgdb_arch arch_kgdb_ops = {
806         /* Breakpoint instruction: */
807         .gdb_bpt_instr          = { 0xcc },
808         .flags                  = KGDB_HW_BREAKPOINT,
809         .set_hw_breakpoint      = kgdb_set_hw_break,
810         .remove_hw_breakpoint   = kgdb_remove_hw_break,
811         .disable_hw_break       = kgdb_disable_hw_debug,
812         .remove_all_hw_break    = kgdb_remove_all_hw_break,
813         .correct_hw_break       = kgdb_correct_hw_break,
814 };
815 

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