kgdb: fix kgdb_validate_break_address to perform a mem write
[linux-2.6.git] / kernel / kgdb.c
1 /*
2  * KGDB stub.
3  *
4  * Maintainer: Jason Wessel <jason.wessel@windriver.com>
5  *
6  * Copyright (C) 2000-2001 VERITAS Software Corporation.
7  * Copyright (C) 2002-2004 Timesys Corporation
8  * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com>
9  * Copyright (C) 2004 Pavel Machek <pavel@suse.cz>
10  * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org>
11  * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd.
12  * Copyright (C) 2005-2008 Wind River Systems, Inc.
13  * Copyright (C) 2007 MontaVista Software, Inc.
14  * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
15  *
16  * Contributors at various stages not listed above:
17  *  Jason Wessel ( jason.wessel@windriver.com )
18  *  George Anzinger <george@mvista.com>
19  *  Anurekh Saxena (anurekh.saxena@timesys.com)
20  *  Lake Stevens Instrument Division (Glenn Engel)
21  *  Jim Kingdon, Cygnus Support.
22  *
23  * Original KGDB stub: David Grothe <dave@gcom.com>,
24  * Tigran Aivazian <tigran@sco.com>
25  *
26  * This file is licensed under the terms of the GNU General Public License
27  * version 2. This program is licensed "as is" without any warranty of any
28  * kind, whether express or implied.
29  */
30 #include <linux/pid_namespace.h>
31 #include <linux/clocksource.h>
32 #include <linux/interrupt.h>
33 #include <linux/spinlock.h>
34 #include <linux/console.h>
35 #include <linux/threads.h>
36 #include <linux/uaccess.h>
37 #include <linux/kernel.h>
38 #include <linux/module.h>
39 #include <linux/ptrace.h>
40 #include <linux/reboot.h>
41 #include <linux/string.h>
42 #include <linux/delay.h>
43 #include <linux/sched.h>
44 #include <linux/sysrq.h>
45 #include <linux/init.h>
46 #include <linux/kgdb.h>
47 #include <linux/pid.h>
48 #include <linux/smp.h>
49 #include <linux/mm.h>
50
51 #include <asm/cacheflush.h>
52 #include <asm/byteorder.h>
53 #include <asm/atomic.h>
54 #include <asm/system.h>
55 #include <asm/unaligned.h>
56
57 static int kgdb_break_asap;
58
59 struct kgdb_state {
60         int                     ex_vector;
61         int                     signo;
62         int                     err_code;
63         int                     cpu;
64         int                     pass_exception;
65         unsigned long           threadid;
66         long                    kgdb_usethreadid;
67         struct pt_regs          *linux_regs;
68 };
69
70 static struct debuggerinfo_struct {
71         void                    *debuggerinfo;
72         struct task_struct      *task;
73 } kgdb_info[NR_CPUS];
74
75 /**
76  * kgdb_connected - Is a host GDB connected to us?
77  */
78 int                             kgdb_connected;
79 EXPORT_SYMBOL_GPL(kgdb_connected);
80
81 /* All the KGDB handlers are installed */
82 static int                      kgdb_io_module_registered;
83
84 /* Guard for recursive entry */
85 static int                      exception_level;
86
87 static struct kgdb_io           *kgdb_io_ops;
88 static DEFINE_SPINLOCK(kgdb_registration_lock);
89
90 /* kgdb console driver is loaded */
91 static int kgdb_con_registered;
92 /* determine if kgdb console output should be used */
93 static int kgdb_use_con;
94
95 static int __init opt_kgdb_con(char *str)
96 {
97         kgdb_use_con = 1;
98         return 0;
99 }
100
101 early_param("kgdbcon", opt_kgdb_con);
102
103 module_param(kgdb_use_con, int, 0644);
104
105 /*
106  * Holds information about breakpoints in a kernel. These breakpoints are
107  * added and removed by gdb.
108  */
109 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
110         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
111 };
112
113 /*
114  * The CPU# of the active CPU, or -1 if none:
115  */
116 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
117
118 /*
119  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
120  * bootup code (which might not have percpu set up yet):
121  */
122 static atomic_t                 passive_cpu_wait[NR_CPUS];
123 static atomic_t                 cpu_in_kgdb[NR_CPUS];
124 atomic_t                        kgdb_setting_breakpoint;
125
126 struct task_struct              *kgdb_usethread;
127 struct task_struct              *kgdb_contthread;
128
129 int                             kgdb_single_step;
130
131 /* Our I/O buffers. */
132 static char                     remcom_in_buffer[BUFMAX];
133 static char                     remcom_out_buffer[BUFMAX];
134
135 /* Storage for the registers, in GDB format. */
136 static unsigned long            gdb_regs[(NUMREGBYTES +
137                                         sizeof(unsigned long) - 1) /
138                                         sizeof(unsigned long)];
139
140 /* to keep track of the CPU which is doing the single stepping*/
141 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
142
143 /*
144  * If you are debugging a problem where roundup (the collection of
145  * all other CPUs) is a problem [this should be extremely rare],
146  * then use the nokgdbroundup option to avoid roundup. In that case
147  * the other CPUs might interfere with your debugging context, so
148  * use this with care:
149  */
150 static int kgdb_do_roundup = 1;
151
152 static int __init opt_nokgdbroundup(char *str)
153 {
154         kgdb_do_roundup = 0;
155
156         return 0;
157 }
158
159 early_param("nokgdbroundup", opt_nokgdbroundup);
160
161 /*
162  * Finally, some KGDB code :-)
163  */
164
165 /*
166  * Weak aliases for breakpoint management,
167  * can be overriden by architectures when needed:
168  */
169 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
170 {
171         int err;
172
173         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
174         if (err)
175                 return err;
176
177         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
178                                   BREAK_INSTR_SIZE);
179 }
180
181 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
182 {
183         return probe_kernel_write((char *)addr,
184                                   (char *)bundle, BREAK_INSTR_SIZE);
185 }
186
187 int __weak kgdb_validate_break_address(unsigned long addr)
188 {
189         char tmp_variable[BREAK_INSTR_SIZE];
190         int err;
191         /* Validate setting the breakpoint and then removing it.  In the
192          * remove fails, the kernel needs to emit a bad message because we
193          * are deep trouble not being able to put things back the way we
194          * found them.
195          */
196         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
197         if (err)
198                 return err;
199         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
200         if (err)
201                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
202                    "memory destroyed at: %lx", addr);
203         return err;
204 }
205
206 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
207 {
208         return instruction_pointer(regs);
209 }
210
211 int __weak kgdb_arch_init(void)
212 {
213         return 0;
214 }
215
216 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
217 {
218         return 0;
219 }
220
221 void __weak
222 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
223 {
224         return;
225 }
226
227 /**
228  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
229  *      @regs: Current &struct pt_regs.
230  *
231  *      This function will be called if the particular architecture must
232  *      disable hardware debugging while it is processing gdb packets or
233  *      handling exception.
234  */
235 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
236 {
237 }
238
239 /*
240  * GDB remote protocol parser:
241  */
242
243 static int hex(char ch)
244 {
245         if ((ch >= 'a') && (ch <= 'f'))
246                 return ch - 'a' + 10;
247         if ((ch >= '0') && (ch <= '9'))
248                 return ch - '0';
249         if ((ch >= 'A') && (ch <= 'F'))
250                 return ch - 'A' + 10;
251         return -1;
252 }
253
254 /* scan for the sequence $<data>#<checksum> */
255 static void get_packet(char *buffer)
256 {
257         unsigned char checksum;
258         unsigned char xmitcsum;
259         int count;
260         char ch;
261
262         do {
263                 /*
264                  * Spin and wait around for the start character, ignore all
265                  * other characters:
266                  */
267                 while ((ch = (kgdb_io_ops->read_char())) != '$')
268                         /* nothing */;
269
270                 kgdb_connected = 1;
271                 checksum = 0;
272                 xmitcsum = -1;
273
274                 count = 0;
275
276                 /*
277                  * now, read until a # or end of buffer is found:
278                  */
279                 while (count < (BUFMAX - 1)) {
280                         ch = kgdb_io_ops->read_char();
281                         if (ch == '#')
282                                 break;
283                         checksum = checksum + ch;
284                         buffer[count] = ch;
285                         count = count + 1;
286                 }
287                 buffer[count] = 0;
288
289                 if (ch == '#') {
290                         xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
291                         xmitcsum += hex(kgdb_io_ops->read_char());
292
293                         if (checksum != xmitcsum)
294                                 /* failed checksum */
295                                 kgdb_io_ops->write_char('-');
296                         else
297                                 /* successful transfer */
298                                 kgdb_io_ops->write_char('+');
299                         if (kgdb_io_ops->flush)
300                                 kgdb_io_ops->flush();
301                 }
302         } while (checksum != xmitcsum);
303 }
304
305 /*
306  * Send the packet in buffer.
307  * Check for gdb connection if asked for.
308  */
309 static void put_packet(char *buffer)
310 {
311         unsigned char checksum;
312         int count;
313         char ch;
314
315         /*
316          * $<packet info>#<checksum>.
317          */
318         while (1) {
319                 kgdb_io_ops->write_char('$');
320                 checksum = 0;
321                 count = 0;
322
323                 while ((ch = buffer[count])) {
324                         kgdb_io_ops->write_char(ch);
325                         checksum += ch;
326                         count++;
327                 }
328
329                 kgdb_io_ops->write_char('#');
330                 kgdb_io_ops->write_char(hex_asc_hi(checksum));
331                 kgdb_io_ops->write_char(hex_asc_lo(checksum));
332                 if (kgdb_io_ops->flush)
333                         kgdb_io_ops->flush();
334
335                 /* Now see what we get in reply. */
336                 ch = kgdb_io_ops->read_char();
337
338                 if (ch == 3)
339                         ch = kgdb_io_ops->read_char();
340
341                 /* If we get an ACK, we are done. */
342                 if (ch == '+')
343                         return;
344
345                 /*
346                  * If we get the start of another packet, this means
347                  * that GDB is attempting to reconnect.  We will NAK
348                  * the packet being sent, and stop trying to send this
349                  * packet.
350                  */
351                 if (ch == '$') {
352                         kgdb_io_ops->write_char('-');
353                         if (kgdb_io_ops->flush)
354                                 kgdb_io_ops->flush();
355                         return;
356                 }
357         }
358 }
359
360 /*
361  * Convert the memory pointed to by mem into hex, placing result in buf.
362  * Return a pointer to the last char put in buf (null). May return an error.
363  */
364 int kgdb_mem2hex(char *mem, char *buf, int count)
365 {
366         char *tmp;
367         int err;
368
369         /*
370          * We use the upper half of buf as an intermediate buffer for the
371          * raw memory copy.  Hex conversion will work against this one.
372          */
373         tmp = buf + count;
374
375         err = probe_kernel_read(tmp, mem, count);
376         if (!err) {
377                 while (count > 0) {
378                         buf = pack_hex_byte(buf, *tmp);
379                         tmp++;
380                         count--;
381                 }
382
383                 *buf = 0;
384         }
385
386         return err;
387 }
388
389 /*
390  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
391  * 0x7d escaped with 0x7d.  Return a pointer to the character after
392  * the last byte written.
393  */
394 static int kgdb_ebin2mem(char *buf, char *mem, int count)
395 {
396         int err = 0;
397         char c;
398
399         while (count-- > 0) {
400                 c = *buf++;
401                 if (c == 0x7d)
402                         c = *buf++ ^ 0x20;
403
404                 err = probe_kernel_write(mem, &c, 1);
405                 if (err)
406                         break;
407
408                 mem++;
409         }
410
411         return err;
412 }
413
414 /*
415  * Convert the hex array pointed to by buf into binary to be placed in mem.
416  * Return a pointer to the character AFTER the last byte written.
417  * May return an error.
418  */
419 int kgdb_hex2mem(char *buf, char *mem, int count)
420 {
421         char *tmp_raw;
422         char *tmp_hex;
423
424         /*
425          * We use the upper half of buf as an intermediate buffer for the
426          * raw memory that is converted from hex.
427          */
428         tmp_raw = buf + count * 2;
429
430         tmp_hex = tmp_raw - 1;
431         while (tmp_hex >= buf) {
432                 tmp_raw--;
433                 *tmp_raw = hex(*tmp_hex--);
434                 *tmp_raw |= hex(*tmp_hex--) << 4;
435         }
436
437         return probe_kernel_write(mem, tmp_raw, count);
438 }
439
440 /*
441  * While we find nice hex chars, build a long_val.
442  * Return number of chars processed.
443  */
444 int kgdb_hex2long(char **ptr, unsigned long *long_val)
445 {
446         int hex_val;
447         int num = 0;
448
449         *long_val = 0;
450
451         while (**ptr) {
452                 hex_val = hex(**ptr);
453                 if (hex_val < 0)
454                         break;
455
456                 *long_val = (*long_val << 4) | hex_val;
457                 num++;
458                 (*ptr)++;
459         }
460
461         return num;
462 }
463
464 /* Write memory due to an 'M' or 'X' packet. */
465 static int write_mem_msg(int binary)
466 {
467         char *ptr = &remcom_in_buffer[1];
468         unsigned long addr;
469         unsigned long length;
470         int err;
471
472         if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
473             kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
474                 if (binary)
475                         err = kgdb_ebin2mem(ptr, (char *)addr, length);
476                 else
477                         err = kgdb_hex2mem(ptr, (char *)addr, length);
478                 if (err)
479                         return err;
480                 if (CACHE_FLUSH_IS_SAFE)
481                         flush_icache_range(addr, addr + length + 1);
482                 return 0;
483         }
484
485         return -EINVAL;
486 }
487
488 static void error_packet(char *pkt, int error)
489 {
490         error = -error;
491         pkt[0] = 'E';
492         pkt[1] = hex_asc[(error / 10)];
493         pkt[2] = hex_asc[(error % 10)];
494         pkt[3] = '\0';
495 }
496
497 /*
498  * Thread ID accessors. We represent a flat TID space to GDB, where
499  * the per CPU idle threads (which under Linux all have PID 0) are
500  * remapped to negative TIDs.
501  */
502
503 #define BUF_THREAD_ID_SIZE      16
504
505 static char *pack_threadid(char *pkt, unsigned char *id)
506 {
507         char *limit;
508
509         limit = pkt + BUF_THREAD_ID_SIZE;
510         while (pkt < limit)
511                 pkt = pack_hex_byte(pkt, *id++);
512
513         return pkt;
514 }
515
516 static void int_to_threadref(unsigned char *id, int value)
517 {
518         unsigned char *scan;
519         int i = 4;
520
521         scan = (unsigned char *)id;
522         while (i--)
523                 *scan++ = 0;
524         put_unaligned_be32(value, scan);
525 }
526
527 static struct task_struct *getthread(struct pt_regs *regs, int tid)
528 {
529         /*
530          * Non-positive TIDs are remapped idle tasks:
531          */
532         if (tid <= 0)
533                 return idle_task(-tid);
534
535         /*
536          * find_task_by_pid_ns() does not take the tasklist lock anymore
537          * but is nicely RCU locked - hence is a pretty resilient
538          * thing to use:
539          */
540         return find_task_by_pid_ns(tid, &init_pid_ns);
541 }
542
543 /*
544  * CPU debug state control:
545  */
546
547 #ifdef CONFIG_SMP
548 static void kgdb_wait(struct pt_regs *regs)
549 {
550         unsigned long flags;
551         int cpu;
552
553         local_irq_save(flags);
554         cpu = raw_smp_processor_id();
555         kgdb_info[cpu].debuggerinfo = regs;
556         kgdb_info[cpu].task = current;
557         /*
558          * Make sure the above info reaches the primary CPU before
559          * our cpu_in_kgdb[] flag setting does:
560          */
561         smp_wmb();
562         atomic_set(&cpu_in_kgdb[cpu], 1);
563
564         /* Wait till primary CPU is done with debugging */
565         while (atomic_read(&passive_cpu_wait[cpu]))
566                 cpu_relax();
567
568         kgdb_info[cpu].debuggerinfo = NULL;
569         kgdb_info[cpu].task = NULL;
570
571         /* fix up hardware debug registers on local cpu */
572         if (arch_kgdb_ops.correct_hw_break)
573                 arch_kgdb_ops.correct_hw_break();
574
575         /* Signal the primary CPU that we are done: */
576         atomic_set(&cpu_in_kgdb[cpu], 0);
577         clocksource_touch_watchdog();
578         local_irq_restore(flags);
579 }
580 #endif
581
582 /*
583  * Some architectures need cache flushes when we set/clear a
584  * breakpoint:
585  */
586 static void kgdb_flush_swbreak_addr(unsigned long addr)
587 {
588         if (!CACHE_FLUSH_IS_SAFE)
589                 return;
590
591         if (current->mm && current->mm->mmap_cache) {
592                 flush_cache_range(current->mm->mmap_cache,
593                                   addr, addr + BREAK_INSTR_SIZE);
594         }
595         /* Force flush instruction cache if it was outside the mm */
596         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
597 }
598
599 /*
600  * SW breakpoint management:
601  */
602 static int kgdb_activate_sw_breakpoints(void)
603 {
604         unsigned long addr;
605         int error = 0;
606         int i;
607
608         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
609                 if (kgdb_break[i].state != BP_SET)
610                         continue;
611
612                 addr = kgdb_break[i].bpt_addr;
613                 error = kgdb_arch_set_breakpoint(addr,
614                                 kgdb_break[i].saved_instr);
615                 if (error)
616                         return error;
617
618                 kgdb_flush_swbreak_addr(addr);
619                 kgdb_break[i].state = BP_ACTIVE;
620         }
621         return 0;
622 }
623
624 static int kgdb_set_sw_break(unsigned long addr)
625 {
626         int err = kgdb_validate_break_address(addr);
627         int breakno = -1;
628         int i;
629
630         if (err)
631                 return err;
632
633         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
634                 if ((kgdb_break[i].state == BP_SET) &&
635                                         (kgdb_break[i].bpt_addr == addr))
636                         return -EEXIST;
637         }
638         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
639                 if (kgdb_break[i].state == BP_REMOVED &&
640                                         kgdb_break[i].bpt_addr == addr) {
641                         breakno = i;
642                         break;
643                 }
644         }
645
646         if (breakno == -1) {
647                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
648                         if (kgdb_break[i].state == BP_UNDEFINED) {
649                                 breakno = i;
650                                 break;
651                         }
652                 }
653         }
654
655         if (breakno == -1)
656                 return -E2BIG;
657
658         kgdb_break[breakno].state = BP_SET;
659         kgdb_break[breakno].type = BP_BREAKPOINT;
660         kgdb_break[breakno].bpt_addr = addr;
661
662         return 0;
663 }
664
665 static int kgdb_deactivate_sw_breakpoints(void)
666 {
667         unsigned long addr;
668         int error = 0;
669         int i;
670
671         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
672                 if (kgdb_break[i].state != BP_ACTIVE)
673                         continue;
674                 addr = kgdb_break[i].bpt_addr;
675                 error = kgdb_arch_remove_breakpoint(addr,
676                                         kgdb_break[i].saved_instr);
677                 if (error)
678                         return error;
679
680                 kgdb_flush_swbreak_addr(addr);
681                 kgdb_break[i].state = BP_SET;
682         }
683         return 0;
684 }
685
686 static int kgdb_remove_sw_break(unsigned long addr)
687 {
688         int i;
689
690         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
691                 if ((kgdb_break[i].state == BP_SET) &&
692                                 (kgdb_break[i].bpt_addr == addr)) {
693                         kgdb_break[i].state = BP_REMOVED;
694                         return 0;
695                 }
696         }
697         return -ENOENT;
698 }
699
700 int kgdb_isremovedbreak(unsigned long addr)
701 {
702         int i;
703
704         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
705                 if ((kgdb_break[i].state == BP_REMOVED) &&
706                                         (kgdb_break[i].bpt_addr == addr))
707                         return 1;
708         }
709         return 0;
710 }
711
712 static int remove_all_break(void)
713 {
714         unsigned long addr;
715         int error;
716         int i;
717
718         /* Clear memory breakpoints. */
719         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
720                 if (kgdb_break[i].state != BP_ACTIVE)
721                         goto setundefined;
722                 addr = kgdb_break[i].bpt_addr;
723                 error = kgdb_arch_remove_breakpoint(addr,
724                                 kgdb_break[i].saved_instr);
725                 if (error)
726                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
727                            addr);
728 setundefined:
729                 kgdb_break[i].state = BP_UNDEFINED;
730         }
731
732         /* Clear hardware breakpoints. */
733         if (arch_kgdb_ops.remove_all_hw_break)
734                 arch_kgdb_ops.remove_all_hw_break();
735
736         return 0;
737 }
738
739 /*
740  * Remap normal tasks to their real PID, idle tasks to -1 ... -NR_CPUs:
741  */
742 static inline int shadow_pid(int realpid)
743 {
744         if (realpid)
745                 return realpid;
746
747         return -1-raw_smp_processor_id();
748 }
749
750 static char gdbmsgbuf[BUFMAX + 1];
751
752 static void kgdb_msg_write(const char *s, int len)
753 {
754         char *bufptr;
755         int wcount;
756         int i;
757
758         /* 'O'utput */
759         gdbmsgbuf[0] = 'O';
760
761         /* Fill and send buffers... */
762         while (len > 0) {
763                 bufptr = gdbmsgbuf + 1;
764
765                 /* Calculate how many this time */
766                 if ((len << 1) > (BUFMAX - 2))
767                         wcount = (BUFMAX - 2) >> 1;
768                 else
769                         wcount = len;
770
771                 /* Pack in hex chars */
772                 for (i = 0; i < wcount; i++)
773                         bufptr = pack_hex_byte(bufptr, s[i]);
774                 *bufptr = '\0';
775
776                 /* Move up */
777                 s += wcount;
778                 len -= wcount;
779
780                 /* Write packet */
781                 put_packet(gdbmsgbuf);
782         }
783 }
784
785 /*
786  * Return true if there is a valid kgdb I/O module.  Also if no
787  * debugger is attached a message can be printed to the console about
788  * waiting for the debugger to attach.
789  *
790  * The print_wait argument is only to be true when called from inside
791  * the core kgdb_handle_exception, because it will wait for the
792  * debugger to attach.
793  */
794 static int kgdb_io_ready(int print_wait)
795 {
796         if (!kgdb_io_ops)
797                 return 0;
798         if (kgdb_connected)
799                 return 1;
800         if (atomic_read(&kgdb_setting_breakpoint))
801                 return 1;
802         if (print_wait)
803                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
804         return 1;
805 }
806
807 /*
808  * All the functions that start with gdb_cmd are the various
809  * operations to implement the handlers for the gdbserial protocol
810  * where KGDB is communicating with an external debugger
811  */
812
813 /* Handle the '?' status packets */
814 static void gdb_cmd_status(struct kgdb_state *ks)
815 {
816         /*
817          * We know that this packet is only sent
818          * during initial connect.  So to be safe,
819          * we clear out our breakpoints now in case
820          * GDB is reconnecting.
821          */
822         remove_all_break();
823
824         remcom_out_buffer[0] = 'S';
825         pack_hex_byte(&remcom_out_buffer[1], ks->signo);
826 }
827
828 /* Handle the 'g' get registers request */
829 static void gdb_cmd_getregs(struct kgdb_state *ks)
830 {
831         struct task_struct *thread;
832         void *local_debuggerinfo;
833         int i;
834
835         thread = kgdb_usethread;
836         if (!thread) {
837                 thread = kgdb_info[ks->cpu].task;
838                 local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
839         } else {
840                 local_debuggerinfo = NULL;
841                 for (i = 0; i < NR_CPUS; i++) {
842                         /*
843                          * Try to find the task on some other
844                          * or possibly this node if we do not
845                          * find the matching task then we try
846                          * to approximate the results.
847                          */
848                         if (thread == kgdb_info[i].task)
849                                 local_debuggerinfo = kgdb_info[i].debuggerinfo;
850                 }
851         }
852
853         /*
854          * All threads that don't have debuggerinfo should be
855          * in __schedule() sleeping, since all other CPUs
856          * are in kgdb_wait, and thus have debuggerinfo.
857          */
858         if (local_debuggerinfo) {
859                 pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
860         } else {
861                 /*
862                  * Pull stuff saved during switch_to; nothing
863                  * else is accessible (or even particularly
864                  * relevant).
865                  *
866                  * This should be enough for a stack trace.
867                  */
868                 sleeping_thread_to_gdb_regs(gdb_regs, thread);
869         }
870         kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
871 }
872
873 /* Handle the 'G' set registers request */
874 static void gdb_cmd_setregs(struct kgdb_state *ks)
875 {
876         kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
877
878         if (kgdb_usethread && kgdb_usethread != current) {
879                 error_packet(remcom_out_buffer, -EINVAL);
880         } else {
881                 gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
882                 strcpy(remcom_out_buffer, "OK");
883         }
884 }
885
886 /* Handle the 'm' memory read bytes */
887 static void gdb_cmd_memread(struct kgdb_state *ks)
888 {
889         char *ptr = &remcom_in_buffer[1];
890         unsigned long length;
891         unsigned long addr;
892         int err;
893
894         if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
895                                         kgdb_hex2long(&ptr, &length) > 0) {
896                 err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
897                 if (err)
898                         error_packet(remcom_out_buffer, err);
899         } else {
900                 error_packet(remcom_out_buffer, -EINVAL);
901         }
902 }
903
904 /* Handle the 'M' memory write bytes */
905 static void gdb_cmd_memwrite(struct kgdb_state *ks)
906 {
907         int err = write_mem_msg(0);
908
909         if (err)
910                 error_packet(remcom_out_buffer, err);
911         else
912                 strcpy(remcom_out_buffer, "OK");
913 }
914
915 /* Handle the 'X' memory binary write bytes */
916 static void gdb_cmd_binwrite(struct kgdb_state *ks)
917 {
918         int err = write_mem_msg(1);
919
920         if (err)
921                 error_packet(remcom_out_buffer, err);
922         else
923                 strcpy(remcom_out_buffer, "OK");
924 }
925
926 /* Handle the 'D' or 'k', detach or kill packets */
927 static void gdb_cmd_detachkill(struct kgdb_state *ks)
928 {
929         int error;
930
931         /* The detach case */
932         if (remcom_in_buffer[0] == 'D') {
933                 error = remove_all_break();
934                 if (error < 0) {
935                         error_packet(remcom_out_buffer, error);
936                 } else {
937                         strcpy(remcom_out_buffer, "OK");
938                         kgdb_connected = 0;
939                 }
940                 put_packet(remcom_out_buffer);
941         } else {
942                 /*
943                  * Assume the kill case, with no exit code checking,
944                  * trying to force detach the debugger:
945                  */
946                 remove_all_break();
947                 kgdb_connected = 0;
948         }
949 }
950
951 /* Handle the 'R' reboot packets */
952 static int gdb_cmd_reboot(struct kgdb_state *ks)
953 {
954         /* For now, only honor R0 */
955         if (strcmp(remcom_in_buffer, "R0") == 0) {
956                 printk(KERN_CRIT "Executing emergency reboot\n");
957                 strcpy(remcom_out_buffer, "OK");
958                 put_packet(remcom_out_buffer);
959
960                 /*
961                  * Execution should not return from
962                  * machine_emergency_restart()
963                  */
964                 machine_emergency_restart();
965                 kgdb_connected = 0;
966
967                 return 1;
968         }
969         return 0;
970 }
971
972 /* Handle the 'q' query packets */
973 static void gdb_cmd_query(struct kgdb_state *ks)
974 {
975         struct task_struct *thread;
976         unsigned char thref[8];
977         char *ptr;
978         int i;
979
980         switch (remcom_in_buffer[1]) {
981         case 's':
982         case 'f':
983                 if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
984                         error_packet(remcom_out_buffer, -EINVAL);
985                         break;
986                 }
987
988                 if (remcom_in_buffer[1] == 'f')
989                         ks->threadid = 1;
990
991                 remcom_out_buffer[0] = 'm';
992                 ptr = remcom_out_buffer + 1;
993
994                 for (i = 0; i < 17; ks->threadid++) {
995                         thread = getthread(ks->linux_regs, ks->threadid);
996                         if (thread) {
997                                 int_to_threadref(thref, ks->threadid);
998                                 pack_threadid(ptr, thref);
999                                 ptr += BUF_THREAD_ID_SIZE;
1000                                 *(ptr++) = ',';
1001                                 i++;
1002                         }
1003                 }
1004                 *(--ptr) = '\0';
1005                 break;
1006
1007         case 'C':
1008                 /* Current thread id */
1009                 strcpy(remcom_out_buffer, "QC");
1010                 ks->threadid = shadow_pid(current->pid);
1011                 int_to_threadref(thref, ks->threadid);
1012                 pack_threadid(remcom_out_buffer + 2, thref);
1013                 break;
1014         case 'T':
1015                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
1016                         error_packet(remcom_out_buffer, -EINVAL);
1017                         break;
1018                 }
1019                 ks->threadid = 0;
1020                 ptr = remcom_in_buffer + 17;
1021                 kgdb_hex2long(&ptr, &ks->threadid);
1022                 if (!getthread(ks->linux_regs, ks->threadid)) {
1023                         error_packet(remcom_out_buffer, -EINVAL);
1024                         break;
1025                 }
1026                 if (ks->threadid > 0) {
1027                         kgdb_mem2hex(getthread(ks->linux_regs,
1028                                         ks->threadid)->comm,
1029                                         remcom_out_buffer, 16);
1030                 } else {
1031                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
1032
1033                         sprintf(tmpstr, "Shadow task %d for pid 0",
1034                                         (int)(-ks->threadid-1));
1035                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
1036                 }
1037                 break;
1038         }
1039 }
1040
1041 /* Handle the 'H' task query packets */
1042 static void gdb_cmd_task(struct kgdb_state *ks)
1043 {
1044         struct task_struct *thread;
1045         char *ptr;
1046
1047         switch (remcom_in_buffer[1]) {
1048         case 'g':
1049                 ptr = &remcom_in_buffer[2];
1050                 kgdb_hex2long(&ptr, &ks->threadid);
1051                 thread = getthread(ks->linux_regs, ks->threadid);
1052                 if (!thread && ks->threadid > 0) {
1053                         error_packet(remcom_out_buffer, -EINVAL);
1054                         break;
1055                 }
1056                 kgdb_usethread = thread;
1057                 ks->kgdb_usethreadid = ks->threadid;
1058                 strcpy(remcom_out_buffer, "OK");
1059                 break;
1060         case 'c':
1061                 ptr = &remcom_in_buffer[2];
1062                 kgdb_hex2long(&ptr, &ks->threadid);
1063                 if (!ks->threadid) {
1064                         kgdb_contthread = NULL;
1065                 } else {
1066                         thread = getthread(ks->linux_regs, ks->threadid);
1067                         if (!thread && ks->threadid > 0) {
1068                                 error_packet(remcom_out_buffer, -EINVAL);
1069                                 break;
1070                         }
1071                         kgdb_contthread = thread;
1072                 }
1073                 strcpy(remcom_out_buffer, "OK");
1074                 break;
1075         }
1076 }
1077
1078 /* Handle the 'T' thread query packets */
1079 static void gdb_cmd_thread(struct kgdb_state *ks)
1080 {
1081         char *ptr = &remcom_in_buffer[1];
1082         struct task_struct *thread;
1083
1084         kgdb_hex2long(&ptr, &ks->threadid);
1085         thread = getthread(ks->linux_regs, ks->threadid);
1086         if (thread)
1087                 strcpy(remcom_out_buffer, "OK");
1088         else
1089                 error_packet(remcom_out_buffer, -EINVAL);
1090 }
1091
1092 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
1093 static void gdb_cmd_break(struct kgdb_state *ks)
1094 {
1095         /*
1096          * Since GDB-5.3, it's been drafted that '0' is a software
1097          * breakpoint, '1' is a hardware breakpoint, so let's do that.
1098          */
1099         char *bpt_type = &remcom_in_buffer[1];
1100         char *ptr = &remcom_in_buffer[2];
1101         unsigned long addr;
1102         unsigned long length;
1103         int error = 0;
1104
1105         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
1106                 /* Unsupported */
1107                 if (*bpt_type > '4')
1108                         return;
1109         } else {
1110                 if (*bpt_type != '0' && *bpt_type != '1')
1111                         /* Unsupported. */
1112                         return;
1113         }
1114
1115         /*
1116          * Test if this is a hardware breakpoint, and
1117          * if we support it:
1118          */
1119         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
1120                 /* Unsupported. */
1121                 return;
1122
1123         if (*(ptr++) != ',') {
1124                 error_packet(remcom_out_buffer, -EINVAL);
1125                 return;
1126         }
1127         if (!kgdb_hex2long(&ptr, &addr)) {
1128                 error_packet(remcom_out_buffer, -EINVAL);
1129                 return;
1130         }
1131         if (*(ptr++) != ',' ||
1132                 !kgdb_hex2long(&ptr, &length)) {
1133                 error_packet(remcom_out_buffer, -EINVAL);
1134                 return;
1135         }
1136
1137         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
1138                 error = kgdb_set_sw_break(addr);
1139         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
1140                 error = kgdb_remove_sw_break(addr);
1141         else if (remcom_in_buffer[0] == 'Z')
1142                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
1143                         (int)length, *bpt_type - '0');
1144         else if (remcom_in_buffer[0] == 'z')
1145                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
1146                         (int) length, *bpt_type - '0');
1147
1148         if (error == 0)
1149                 strcpy(remcom_out_buffer, "OK");
1150         else
1151                 error_packet(remcom_out_buffer, error);
1152 }
1153
1154 /* Handle the 'C' signal / exception passing packets */
1155 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
1156 {
1157         /* C09 == pass exception
1158          * C15 == detach kgdb, pass exception
1159          */
1160         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
1161
1162                 ks->pass_exception = 1;
1163                 remcom_in_buffer[0] = 'c';
1164
1165         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
1166
1167                 ks->pass_exception = 1;
1168                 remcom_in_buffer[0] = 'D';
1169                 remove_all_break();
1170                 kgdb_connected = 0;
1171                 return 1;
1172
1173         } else {
1174                 error_packet(remcom_out_buffer, -EINVAL);
1175                 return 0;
1176         }
1177
1178         /* Indicate fall through */
1179         return -1;
1180 }
1181
1182 /*
1183  * This function performs all gdbserial command procesing
1184  */
1185 static int gdb_serial_stub(struct kgdb_state *ks)
1186 {
1187         int error = 0;
1188         int tmp;
1189
1190         /* Clear the out buffer. */
1191         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1192
1193         if (kgdb_connected) {
1194                 unsigned char thref[8];
1195                 char *ptr;
1196
1197                 /* Reply to host that an exception has occurred */
1198                 ptr = remcom_out_buffer;
1199                 *ptr++ = 'T';
1200                 ptr = pack_hex_byte(ptr, ks->signo);
1201                 ptr += strlen(strcpy(ptr, "thread:"));
1202                 int_to_threadref(thref, shadow_pid(current->pid));
1203                 ptr = pack_threadid(ptr, thref);
1204                 *ptr++ = ';';
1205                 put_packet(remcom_out_buffer);
1206         }
1207
1208         kgdb_usethread = kgdb_info[ks->cpu].task;
1209         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
1210         ks->pass_exception = 0;
1211
1212         while (1) {
1213                 error = 0;
1214
1215                 /* Clear the out buffer. */
1216                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1217
1218                 get_packet(remcom_in_buffer);
1219
1220                 switch (remcom_in_buffer[0]) {
1221                 case '?': /* gdbserial status */
1222                         gdb_cmd_status(ks);
1223                         break;
1224                 case 'g': /* return the value of the CPU registers */
1225                         gdb_cmd_getregs(ks);
1226                         break;
1227                 case 'G': /* set the value of the CPU registers - return OK */
1228                         gdb_cmd_setregs(ks);
1229                         break;
1230                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1231                         gdb_cmd_memread(ks);
1232                         break;
1233                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1234                         gdb_cmd_memwrite(ks);
1235                         break;
1236                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1237                         gdb_cmd_binwrite(ks);
1238                         break;
1239                         /* kill or detach. KGDB should treat this like a
1240                          * continue.
1241                          */
1242                 case 'D': /* Debugger detach */
1243                 case 'k': /* Debugger detach via kill */
1244                         gdb_cmd_detachkill(ks);
1245                         goto default_handle;
1246                 case 'R': /* Reboot */
1247                         if (gdb_cmd_reboot(ks))
1248                                 goto default_handle;
1249                         break;
1250                 case 'q': /* query command */
1251                         gdb_cmd_query(ks);
1252                         break;
1253                 case 'H': /* task related */
1254                         gdb_cmd_task(ks);
1255                         break;
1256                 case 'T': /* Query thread status */
1257                         gdb_cmd_thread(ks);
1258                         break;
1259                 case 'z': /* Break point remove */
1260                 case 'Z': /* Break point set */
1261                         gdb_cmd_break(ks);
1262                         break;
1263                 case 'C': /* Exception passing */
1264                         tmp = gdb_cmd_exception_pass(ks);
1265                         if (tmp > 0)
1266                                 goto default_handle;
1267                         if (tmp == 0)
1268                                 break;
1269                         /* Fall through on tmp < 0 */
1270                 case 'c': /* Continue packet */
1271                 case 's': /* Single step packet */
1272                         if (kgdb_contthread && kgdb_contthread != current) {
1273                                 /* Can't switch threads in kgdb */
1274                                 error_packet(remcom_out_buffer, -EINVAL);
1275                                 break;
1276                         }
1277                         kgdb_activate_sw_breakpoints();
1278                         /* Fall through to default processing */
1279                 default:
1280 default_handle:
1281                         error = kgdb_arch_handle_exception(ks->ex_vector,
1282                                                 ks->signo,
1283                                                 ks->err_code,
1284                                                 remcom_in_buffer,
1285                                                 remcom_out_buffer,
1286                                                 ks->linux_regs);
1287                         /*
1288                          * Leave cmd processing on error, detach,
1289                          * kill, continue, or single step.
1290                          */
1291                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1292                             remcom_in_buffer[0] == 'k') {
1293                                 error = 0;
1294                                 goto kgdb_exit;
1295                         }
1296
1297                 }
1298
1299                 /* reply to the request */
1300                 put_packet(remcom_out_buffer);
1301         }
1302
1303 kgdb_exit:
1304         if (ks->pass_exception)
1305                 error = 1;
1306         return error;
1307 }
1308
1309 static int kgdb_reenter_check(struct kgdb_state *ks)
1310 {
1311         unsigned long addr;
1312
1313         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
1314                 return 0;
1315
1316         /* Panic on recursive debugger calls: */
1317         exception_level++;
1318         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
1319         kgdb_deactivate_sw_breakpoints();
1320
1321         /*
1322          * If the break point removed ok at the place exception
1323          * occurred, try to recover and print a warning to the end
1324          * user because the user planted a breakpoint in a place that
1325          * KGDB needs in order to function.
1326          */
1327         if (kgdb_remove_sw_break(addr) == 0) {
1328                 exception_level = 0;
1329                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1330                 kgdb_activate_sw_breakpoints();
1331                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
1332                         addr);
1333                 WARN_ON_ONCE(1);
1334
1335                 return 1;
1336         }
1337         remove_all_break();
1338         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1339
1340         if (exception_level > 1) {
1341                 dump_stack();
1342                 panic("Recursive entry to debugger");
1343         }
1344
1345         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
1346         dump_stack();
1347         panic("Recursive entry to debugger");
1348
1349         return 1;
1350 }
1351
1352 /*
1353  * kgdb_handle_exception() - main entry point from a kernel exception
1354  *
1355  * Locking hierarchy:
1356  *      interface locks, if any (begin_session)
1357  *      kgdb lock (kgdb_active)
1358  */
1359 int
1360 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
1361 {
1362         struct kgdb_state kgdb_var;
1363         struct kgdb_state *ks = &kgdb_var;
1364         unsigned long flags;
1365         int error = 0;
1366         int i, cpu;
1367
1368         ks->cpu                 = raw_smp_processor_id();
1369         ks->ex_vector           = evector;
1370         ks->signo               = signo;
1371         ks->ex_vector           = evector;
1372         ks->err_code            = ecode;
1373         ks->kgdb_usethreadid    = 0;
1374         ks->linux_regs          = regs;
1375
1376         if (kgdb_reenter_check(ks))
1377                 return 0; /* Ouch, double exception ! */
1378
1379 acquirelock:
1380         /*
1381          * Interrupts will be restored by the 'trap return' code, except when
1382          * single stepping.
1383          */
1384         local_irq_save(flags);
1385
1386         cpu = raw_smp_processor_id();
1387
1388         /*
1389          * Acquire the kgdb_active lock:
1390          */
1391         while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
1392                 cpu_relax();
1393
1394         /*
1395          * Do not start the debugger connection on this CPU if the last
1396          * instance of the exception handler wanted to come into the
1397          * debugger on a different CPU via a single step
1398          */
1399         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
1400             atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
1401
1402                 atomic_set(&kgdb_active, -1);
1403                 clocksource_touch_watchdog();
1404                 local_irq_restore(flags);
1405
1406                 goto acquirelock;
1407         }
1408
1409         if (!kgdb_io_ready(1)) {
1410                 error = 1;
1411                 goto kgdb_restore; /* No I/O connection, so resume the system */
1412         }
1413
1414         /*
1415          * Don't enter if we have hit a removed breakpoint.
1416          */
1417         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
1418                 goto kgdb_restore;
1419
1420         /* Call the I/O driver's pre_exception routine */
1421         if (kgdb_io_ops->pre_exception)
1422                 kgdb_io_ops->pre_exception();
1423
1424         kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
1425         kgdb_info[ks->cpu].task = current;
1426
1427         kgdb_disable_hw_debug(ks->linux_regs);
1428
1429         /*
1430          * Get the passive CPU lock which will hold all the non-primary
1431          * CPU in a spin state while the debugger is active
1432          */
1433         if (!kgdb_single_step || !kgdb_contthread) {
1434                 for (i = 0; i < NR_CPUS; i++)
1435                         atomic_set(&passive_cpu_wait[i], 1);
1436         }
1437
1438         /*
1439          * spin_lock code is good enough as a barrier so we don't
1440          * need one here:
1441          */
1442         atomic_set(&cpu_in_kgdb[ks->cpu], 1);
1443
1444 #ifdef CONFIG_SMP
1445         /* Signal the other CPUs to enter kgdb_wait() */
1446         if ((!kgdb_single_step || !kgdb_contthread) && kgdb_do_roundup)
1447                 kgdb_roundup_cpus(flags);
1448 #endif
1449
1450         /*
1451          * Wait for the other CPUs to be notified and be waiting for us:
1452          */
1453         for_each_online_cpu(i) {
1454                 while (!atomic_read(&cpu_in_kgdb[i]))
1455                         cpu_relax();
1456         }
1457
1458         /*
1459          * At this point the primary processor is completely
1460          * in the debugger and all secondary CPUs are quiescent
1461          */
1462         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
1463         kgdb_deactivate_sw_breakpoints();
1464         kgdb_single_step = 0;
1465         kgdb_contthread = NULL;
1466         exception_level = 0;
1467
1468         /* Talk to debugger with gdbserial protocol */
1469         error = gdb_serial_stub(ks);
1470
1471         /* Call the I/O driver's post_exception routine */
1472         if (kgdb_io_ops->post_exception)
1473                 kgdb_io_ops->post_exception();
1474
1475         kgdb_info[ks->cpu].debuggerinfo = NULL;
1476         kgdb_info[ks->cpu].task = NULL;
1477         atomic_set(&cpu_in_kgdb[ks->cpu], 0);
1478
1479         if (!kgdb_single_step || !kgdb_contthread) {
1480                 for (i = NR_CPUS-1; i >= 0; i--)
1481                         atomic_set(&passive_cpu_wait[i], 0);
1482                 /*
1483                  * Wait till all the CPUs have quit
1484                  * from the debugger.
1485                  */
1486                 for_each_online_cpu(i) {
1487                         while (atomic_read(&cpu_in_kgdb[i]))
1488                                 cpu_relax();
1489                 }
1490         }
1491
1492 kgdb_restore:
1493         /* Free kgdb_active */
1494         atomic_set(&kgdb_active, -1);
1495         clocksource_touch_watchdog();
1496         local_irq_restore(flags);
1497
1498         return error;
1499 }
1500
1501 int kgdb_nmicallback(int cpu, void *regs)
1502 {
1503 #ifdef CONFIG_SMP
1504         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
1505                         atomic_read(&kgdb_active) != cpu &&
1506                         atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
1507                 kgdb_wait((struct pt_regs *)regs);
1508                 return 0;
1509         }
1510 #endif
1511         return 1;
1512 }
1513
1514 static void kgdb_console_write(struct console *co, const char *s,
1515    unsigned count)
1516 {
1517         unsigned long flags;
1518
1519         /* If we're debugging, or KGDB has not connected, don't try
1520          * and print. */
1521         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
1522                 return;
1523
1524         local_irq_save(flags);
1525         kgdb_msg_write(s, count);
1526         local_irq_restore(flags);
1527 }
1528
1529 static struct console kgdbcons = {
1530         .name           = "kgdb",
1531         .write          = kgdb_console_write,
1532         .flags          = CON_PRINTBUFFER | CON_ENABLED,
1533         .index          = -1,
1534 };
1535
1536 #ifdef CONFIG_MAGIC_SYSRQ
1537 static void sysrq_handle_gdb(int key, struct tty_struct *tty)
1538 {
1539         if (!kgdb_io_ops) {
1540                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
1541                 return;
1542         }
1543         if (!kgdb_connected)
1544                 printk(KERN_CRIT "Entering KGDB\n");
1545
1546         kgdb_breakpoint();
1547 }
1548
1549 static struct sysrq_key_op sysrq_gdb_op = {
1550         .handler        = sysrq_handle_gdb,
1551         .help_msg       = "Gdb",
1552         .action_msg     = "GDB",
1553 };
1554 #endif
1555
1556 static void kgdb_register_callbacks(void)
1557 {
1558         if (!kgdb_io_module_registered) {
1559                 kgdb_io_module_registered = 1;
1560                 kgdb_arch_init();
1561 #ifdef CONFIG_MAGIC_SYSRQ
1562                 register_sysrq_key('g', &sysrq_gdb_op);
1563 #endif
1564                 if (kgdb_use_con && !kgdb_con_registered) {
1565                         register_console(&kgdbcons);
1566                         kgdb_con_registered = 1;
1567                 }
1568         }
1569 }
1570
1571 static void kgdb_unregister_callbacks(void)
1572 {
1573         /*
1574          * When this routine is called KGDB should unregister from the
1575          * panic handler and clean up, making sure it is not handling any
1576          * break exceptions at the time.
1577          */
1578         if (kgdb_io_module_registered) {
1579                 kgdb_io_module_registered = 0;
1580                 kgdb_arch_exit();
1581 #ifdef CONFIG_MAGIC_SYSRQ
1582                 unregister_sysrq_key('g', &sysrq_gdb_op);
1583 #endif
1584                 if (kgdb_con_registered) {
1585                         unregister_console(&kgdbcons);
1586                         kgdb_con_registered = 0;
1587                 }
1588         }
1589 }
1590
1591 static void kgdb_initial_breakpoint(void)
1592 {
1593         kgdb_break_asap = 0;
1594
1595         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
1596         kgdb_breakpoint();
1597 }
1598
1599 /**
1600  *      kgdb_register_io_module - register KGDB IO module
1601  *      @new_kgdb_io_ops: the io ops vector
1602  *
1603  *      Register it with the KGDB core.
1604  */
1605 int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
1606 {
1607         int err;
1608
1609         spin_lock(&kgdb_registration_lock);
1610
1611         if (kgdb_io_ops) {
1612                 spin_unlock(&kgdb_registration_lock);
1613
1614                 printk(KERN_ERR "kgdb: Another I/O driver is already "
1615                                 "registered with KGDB.\n");
1616                 return -EBUSY;
1617         }
1618
1619         if (new_kgdb_io_ops->init) {
1620                 err = new_kgdb_io_ops->init();
1621                 if (err) {
1622                         spin_unlock(&kgdb_registration_lock);
1623                         return err;
1624                 }
1625         }
1626
1627         kgdb_io_ops = new_kgdb_io_ops;
1628
1629         spin_unlock(&kgdb_registration_lock);
1630
1631         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
1632                new_kgdb_io_ops->name);
1633
1634         /* Arm KGDB now. */
1635         kgdb_register_callbacks();
1636
1637         if (kgdb_break_asap)
1638                 kgdb_initial_breakpoint();
1639
1640         return 0;
1641 }
1642 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1643
1644 /**
1645  *      kkgdb_unregister_io_module - unregister KGDB IO module
1646  *      @old_kgdb_io_ops: the io ops vector
1647  *
1648  *      Unregister it with the KGDB core.
1649  */
1650 void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
1651 {
1652         BUG_ON(kgdb_connected);
1653
1654         /*
1655          * KGDB is no longer able to communicate out, so
1656          * unregister our callbacks and reset state.
1657          */
1658         kgdb_unregister_callbacks();
1659
1660         spin_lock(&kgdb_registration_lock);
1661
1662         WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
1663         kgdb_io_ops = NULL;
1664
1665         spin_unlock(&kgdb_registration_lock);
1666
1667         printk(KERN_INFO
1668                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
1669                 old_kgdb_io_ops->name);
1670 }
1671 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1672
1673 /**
1674  * kgdb_breakpoint - generate breakpoint exception
1675  *
1676  * This function will generate a breakpoint exception.  It is used at the
1677  * beginning of a program to sync up with a debugger and can be used
1678  * otherwise as a quick means to stop program execution and "break" into
1679  * the debugger.
1680  */
1681 void kgdb_breakpoint(void)
1682 {
1683         atomic_set(&kgdb_setting_breakpoint, 1);
1684         wmb(); /* Sync point before breakpoint */
1685         arch_kgdb_breakpoint();
1686         wmb(); /* Sync point after breakpoint */
1687         atomic_set(&kgdb_setting_breakpoint, 0);
1688 }
1689 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1690
1691 static int __init opt_kgdb_wait(char *str)
1692 {
1693         kgdb_break_asap = 1;
1694
1695         if (kgdb_io_module_registered)
1696                 kgdb_initial_breakpoint();
1697
1698         return 0;
1699 }
1700
1701 early_param("kgdbwait", opt_kgdb_wait);