kgdb: fix several kgdb regressions
[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
56 static int kgdb_break_asap;
57
58 struct kgdb_state {
59         int                     ex_vector;
60         int                     signo;
61         int                     err_code;
62         int                     cpu;
63         int                     pass_exception;
64         long                    threadid;
65         long                    kgdb_usethreadid;
66         struct pt_regs          *linux_regs;
67 };
68
69 static struct debuggerinfo_struct {
70         void                    *debuggerinfo;
71         struct task_struct      *task;
72 } kgdb_info[NR_CPUS];
73
74 /**
75  * kgdb_connected - Is a host GDB connected to us?
76  */
77 int                             kgdb_connected;
78 EXPORT_SYMBOL_GPL(kgdb_connected);
79
80 /* All the KGDB handlers are installed */
81 static int                      kgdb_io_module_registered;
82
83 /* Guard for recursive entry */
84 static int                      exception_level;
85
86 static struct kgdb_io           *kgdb_io_ops;
87 static DEFINE_SPINLOCK(kgdb_registration_lock);
88
89 /* kgdb console driver is loaded */
90 static int kgdb_con_registered;
91 /* determine if kgdb console output should be used */
92 static int kgdb_use_con;
93
94 static int __init opt_kgdb_con(char *str)
95 {
96         kgdb_use_con = 1;
97         return 0;
98 }
99
100 early_param("kgdbcon", opt_kgdb_con);
101
102 module_param(kgdb_use_con, int, 0644);
103
104 /*
105  * Holds information about breakpoints in a kernel. These breakpoints are
106  * added and removed by gdb.
107  */
108 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
109         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
110 };
111
112 /*
113  * The CPU# of the active CPU, or -1 if none:
114  */
115 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
116
117 /*
118  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
119  * bootup code (which might not have percpu set up yet):
120  */
121 static atomic_t                 passive_cpu_wait[NR_CPUS];
122 static atomic_t                 cpu_in_kgdb[NR_CPUS];
123 atomic_t                        kgdb_setting_breakpoint;
124
125 struct task_struct              *kgdb_usethread;
126 struct task_struct              *kgdb_contthread;
127
128 int                             kgdb_single_step;
129
130 /* Our I/O buffers. */
131 static char                     remcom_in_buffer[BUFMAX];
132 static char                     remcom_out_buffer[BUFMAX];
133
134 /* Storage for the registers, in GDB format. */
135 static unsigned long            gdb_regs[(NUMREGBYTES +
136                                         sizeof(unsigned long) - 1) /
137                                         sizeof(unsigned long)];
138
139 /* to keep track of the CPU which is doing the single stepping*/
140 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
141
142 /*
143  * If you are debugging a problem where roundup (the collection of
144  * all other CPUs) is a problem [this should be extremely rare],
145  * then use the nokgdbroundup option to avoid roundup. In that case
146  * the other CPUs might interfere with your debugging context, so
147  * use this with care:
148  */
149 int                             kgdb_do_roundup = 1;
150
151 static int __init opt_nokgdbroundup(char *str)
152 {
153         kgdb_do_roundup = 0;
154
155         return 0;
156 }
157
158 early_param("nokgdbroundup", opt_nokgdbroundup);
159
160 /*
161  * Finally, some KGDB code :-)
162  */
163
164 /*
165  * Weak aliases for breakpoint management,
166  * can be overriden by architectures when needed:
167  */
168 int __weak kgdb_validate_break_address(unsigned long addr)
169 {
170         char tmp_variable[BREAK_INSTR_SIZE];
171
172         return probe_kernel_read(tmp_variable, (char *)addr, BREAK_INSTR_SIZE);
173 }
174
175 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
176 {
177         int err;
178
179         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
180         if (err)
181                 return err;
182
183         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
184                                   BREAK_INSTR_SIZE);
185 }
186
187 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
188 {
189         return probe_kernel_write((char *)addr,
190                                   (char *)bundle, BREAK_INSTR_SIZE);
191 }
192
193 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
194 {
195         return instruction_pointer(regs);
196 }
197
198 int __weak kgdb_arch_init(void)
199 {
200         return 0;
201 }
202
203 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
204 {
205         return 0;
206 }
207
208 void __weak
209 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
210 {
211         return;
212 }
213
214 /**
215  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
216  *      @regs: Current &struct pt_regs.
217  *
218  *      This function will be called if the particular architecture must
219  *      disable hardware debugging while it is processing gdb packets or
220  *      handling exception.
221  */
222 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
223 {
224 }
225
226 /*
227  * GDB remote protocol parser:
228  */
229
230 static const char       hexchars[] = "0123456789abcdef";
231
232 static int hex(char ch)
233 {
234         if ((ch >= 'a') && (ch <= 'f'))
235                 return ch - 'a' + 10;
236         if ((ch >= '0') && (ch <= '9'))
237                 return ch - '0';
238         if ((ch >= 'A') && (ch <= 'F'))
239                 return ch - 'A' + 10;
240         return -1;
241 }
242
243 /* scan for the sequence $<data>#<checksum> */
244 static void get_packet(char *buffer)
245 {
246         unsigned char checksum;
247         unsigned char xmitcsum;
248         int count;
249         char ch;
250
251         do {
252                 /*
253                  * Spin and wait around for the start character, ignore all
254                  * other characters:
255                  */
256                 while ((ch = (kgdb_io_ops->read_char())) != '$')
257                         /* nothing */;
258
259                 kgdb_connected = 1;
260                 checksum = 0;
261                 xmitcsum = -1;
262
263                 count = 0;
264
265                 /*
266                  * now, read until a # or end of buffer is found:
267                  */
268                 while (count < (BUFMAX - 1)) {
269                         ch = kgdb_io_ops->read_char();
270                         if (ch == '#')
271                                 break;
272                         checksum = checksum + ch;
273                         buffer[count] = ch;
274                         count = count + 1;
275                 }
276                 buffer[count] = 0;
277
278                 if (ch == '#') {
279                         xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
280                         xmitcsum += hex(kgdb_io_ops->read_char());
281
282                         if (checksum != xmitcsum)
283                                 /* failed checksum */
284                                 kgdb_io_ops->write_char('-');
285                         else
286                                 /* successful transfer */
287                                 kgdb_io_ops->write_char('+');
288                         if (kgdb_io_ops->flush)
289                                 kgdb_io_ops->flush();
290                 }
291         } while (checksum != xmitcsum);
292 }
293
294 /*
295  * Send the packet in buffer.
296  * Check for gdb connection if asked for.
297  */
298 static void put_packet(char *buffer)
299 {
300         unsigned char checksum;
301         int count;
302         char ch;
303
304         /*
305          * $<packet info>#<checksum>.
306          */
307         while (1) {
308                 kgdb_io_ops->write_char('$');
309                 checksum = 0;
310                 count = 0;
311
312                 while ((ch = buffer[count])) {
313                         kgdb_io_ops->write_char(ch);
314                         checksum += ch;
315                         count++;
316                 }
317
318                 kgdb_io_ops->write_char('#');
319                 kgdb_io_ops->write_char(hexchars[checksum >> 4]);
320                 kgdb_io_ops->write_char(hexchars[checksum & 0xf]);
321                 if (kgdb_io_ops->flush)
322                         kgdb_io_ops->flush();
323
324                 /* Now see what we get in reply. */
325                 ch = kgdb_io_ops->read_char();
326
327                 if (ch == 3)
328                         ch = kgdb_io_ops->read_char();
329
330                 /* If we get an ACK, we are done. */
331                 if (ch == '+')
332                         return;
333
334                 /*
335                  * If we get the start of another packet, this means
336                  * that GDB is attempting to reconnect.  We will NAK
337                  * the packet being sent, and stop trying to send this
338                  * packet.
339                  */
340                 if (ch == '$') {
341                         kgdb_io_ops->write_char('-');
342                         if (kgdb_io_ops->flush)
343                                 kgdb_io_ops->flush();
344                         return;
345                 }
346         }
347 }
348
349 static char *pack_hex_byte(char *pkt, u8 byte)
350 {
351         *pkt++ = hexchars[byte >> 4];
352         *pkt++ = hexchars[byte & 0xf];
353
354         return pkt;
355 }
356
357 /*
358  * Convert the memory pointed to by mem into hex, placing result in buf.
359  * Return a pointer to the last char put in buf (null). May return an error.
360  */
361 int kgdb_mem2hex(char *mem, char *buf, int count)
362 {
363         char *tmp;
364         int err;
365
366         /*
367          * We use the upper half of buf as an intermediate buffer for the
368          * raw memory copy.  Hex conversion will work against this one.
369          */
370         tmp = buf + count;
371
372         err = probe_kernel_read(tmp, mem, count);
373         if (!err) {
374                 while (count > 0) {
375                         buf = pack_hex_byte(buf, *tmp);
376                         tmp++;
377                         count--;
378                 }
379
380                 *buf = 0;
381         }
382
383         return err;
384 }
385
386 /*
387  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
388  * 0x7d escaped with 0x7d.  Return a pointer to the character after
389  * the last byte written.
390  */
391 static int kgdb_ebin2mem(char *buf, char *mem, int count)
392 {
393         int err = 0;
394         char c;
395
396         while (count-- > 0) {
397                 c = *buf++;
398                 if (c == 0x7d)
399                         c = *buf++ ^ 0x20;
400
401                 err = probe_kernel_write(mem, &c, 1);
402                 if (err)
403                         break;
404
405                 mem++;
406         }
407
408         return err;
409 }
410
411 /*
412  * Convert the hex array pointed to by buf into binary to be placed in mem.
413  * Return a pointer to the character AFTER the last byte written.
414  * May return an error.
415  */
416 int kgdb_hex2mem(char *buf, char *mem, int count)
417 {
418         char *tmp_raw;
419         char *tmp_hex;
420
421         /*
422          * We use the upper half of buf as an intermediate buffer for the
423          * raw memory that is converted from hex.
424          */
425         tmp_raw = buf + count * 2;
426
427         tmp_hex = tmp_raw - 1;
428         while (tmp_hex >= buf) {
429                 tmp_raw--;
430                 *tmp_raw = hex(*tmp_hex--);
431                 *tmp_raw |= hex(*tmp_hex--) << 4;
432         }
433
434         return probe_kernel_write(mem, tmp_raw, count);
435 }
436
437 /*
438  * While we find nice hex chars, build a long_val.
439  * Return number of chars processed.
440  */
441 int kgdb_hex2long(char **ptr, long *long_val)
442 {
443         int hex_val;
444         int num = 0;
445
446         *long_val = 0;
447
448         while (**ptr) {
449                 hex_val = hex(**ptr);
450                 if (hex_val < 0)
451                         break;
452
453                 *long_val = (*long_val << 4) | hex_val;
454                 num++;
455                 (*ptr)++;
456         }
457
458         return num;
459 }
460
461 /* Write memory due to an 'M' or 'X' packet. */
462 static int write_mem_msg(int binary)
463 {
464         char *ptr = &remcom_in_buffer[1];
465         unsigned long addr;
466         unsigned long length;
467         int err;
468
469         if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
470             kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
471                 if (binary)
472                         err = kgdb_ebin2mem(ptr, (char *)addr, length);
473                 else
474                         err = kgdb_hex2mem(ptr, (char *)addr, length);
475                 if (err)
476                         return err;
477                 if (CACHE_FLUSH_IS_SAFE)
478                         flush_icache_range(addr, addr + length + 1);
479                 return 0;
480         }
481
482         return -EINVAL;
483 }
484
485 static void error_packet(char *pkt, int error)
486 {
487         error = -error;
488         pkt[0] = 'E';
489         pkt[1] = hexchars[(error / 10)];
490         pkt[2] = hexchars[(error % 10)];
491         pkt[3] = '\0';
492 }
493
494 /*
495  * Thread ID accessors. We represent a flat TID space to GDB, where
496  * the per CPU idle threads (which under Linux all have PID 0) are
497  * remapped to negative TIDs.
498  */
499
500 #define BUF_THREAD_ID_SIZE      16
501
502 static char *pack_threadid(char *pkt, unsigned char *id)
503 {
504         char *limit;
505
506         limit = pkt + BUF_THREAD_ID_SIZE;
507         while (pkt < limit)
508                 pkt = pack_hex_byte(pkt, *id++);
509
510         return pkt;
511 }
512
513 static void int_to_threadref(unsigned char *id, int value)
514 {
515         unsigned char *scan;
516         int i = 4;
517
518         scan = (unsigned char *)id;
519         while (i--)
520                 *scan++ = 0;
521         *scan++ = (value >> 24) & 0xff;
522         *scan++ = (value >> 16) & 0xff;
523         *scan++ = (value >> 8) & 0xff;
524         *scan++ = (value & 0xff);
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         /*
565          * The primary CPU must be active to enter here, but this is
566          * guard in case the primary CPU had not been selected if
567          * this was an entry via nmi.
568          */
569         while (atomic_read(&kgdb_active) == -1)
570                 cpu_relax();
571
572         /* Wait till primary CPU goes completely into the debugger. */
573         while (!atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)]))
574                 cpu_relax();
575
576         /* Wait till primary CPU is done with debugging */
577         while (atomic_read(&passive_cpu_wait[cpu]))
578                 cpu_relax();
579
580         kgdb_info[cpu].debuggerinfo = NULL;
581         kgdb_info[cpu].task = NULL;
582
583         /* fix up hardware debug registers on local cpu */
584         if (arch_kgdb_ops.correct_hw_break)
585                 arch_kgdb_ops.correct_hw_break();
586
587         /* Signal the primary CPU that we are done: */
588         atomic_set(&cpu_in_kgdb[cpu], 0);
589         clocksource_touch_watchdog();
590         local_irq_restore(flags);
591 }
592 #endif
593
594 /*
595  * Some architectures need cache flushes when we set/clear a
596  * breakpoint:
597  */
598 static void kgdb_flush_swbreak_addr(unsigned long addr)
599 {
600         if (!CACHE_FLUSH_IS_SAFE)
601                 return;
602
603         if (current->mm && current->mm->mmap_cache) {
604                 flush_cache_range(current->mm->mmap_cache,
605                                   addr, addr + BREAK_INSTR_SIZE);
606         } else {
607                 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
608         }
609 }
610
611 /*
612  * SW breakpoint management:
613  */
614 static int kgdb_activate_sw_breakpoints(void)
615 {
616         unsigned long addr;
617         int error = 0;
618         int i;
619
620         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
621                 if (kgdb_break[i].state != BP_SET)
622                         continue;
623
624                 addr = kgdb_break[i].bpt_addr;
625                 error = kgdb_arch_set_breakpoint(addr,
626                                 kgdb_break[i].saved_instr);
627                 if (error)
628                         return error;
629
630                 kgdb_flush_swbreak_addr(addr);
631                 kgdb_break[i].state = BP_ACTIVE;
632         }
633         return 0;
634 }
635
636 static int kgdb_set_sw_break(unsigned long addr)
637 {
638         int err = kgdb_validate_break_address(addr);
639         int breakno = -1;
640         int i;
641
642         if (err)
643                 return err;
644
645         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
646                 if ((kgdb_break[i].state == BP_SET) &&
647                                         (kgdb_break[i].bpt_addr == addr))
648                         return -EEXIST;
649         }
650         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
651                 if (kgdb_break[i].state == BP_REMOVED &&
652                                         kgdb_break[i].bpt_addr == addr) {
653                         breakno = i;
654                         break;
655                 }
656         }
657
658         if (breakno == -1) {
659                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
660                         if (kgdb_break[i].state == BP_UNDEFINED) {
661                                 breakno = i;
662                                 break;
663                         }
664                 }
665         }
666
667         if (breakno == -1)
668                 return -E2BIG;
669
670         kgdb_break[breakno].state = BP_SET;
671         kgdb_break[breakno].type = BP_BREAKPOINT;
672         kgdb_break[breakno].bpt_addr = addr;
673
674         return 0;
675 }
676
677 static int kgdb_deactivate_sw_breakpoints(void)
678 {
679         unsigned long addr;
680         int error = 0;
681         int i;
682
683         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
684                 if (kgdb_break[i].state != BP_ACTIVE)
685                         continue;
686                 addr = kgdb_break[i].bpt_addr;
687                 error = kgdb_arch_remove_breakpoint(addr,
688                                         kgdb_break[i].saved_instr);
689                 if (error)
690                         return error;
691
692                 kgdb_flush_swbreak_addr(addr);
693                 kgdb_break[i].state = BP_SET;
694         }
695         return 0;
696 }
697
698 static int kgdb_remove_sw_break(unsigned long addr)
699 {
700         int i;
701
702         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
703                 if ((kgdb_break[i].state == BP_SET) &&
704                                 (kgdb_break[i].bpt_addr == addr)) {
705                         kgdb_break[i].state = BP_REMOVED;
706                         return 0;
707                 }
708         }
709         return -ENOENT;
710 }
711
712 int kgdb_isremovedbreak(unsigned long addr)
713 {
714         int i;
715
716         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
717                 if ((kgdb_break[i].state == BP_REMOVED) &&
718                                         (kgdb_break[i].bpt_addr == addr))
719                         return 1;
720         }
721         return 0;
722 }
723
724 int remove_all_break(void)
725 {
726         unsigned long addr;
727         int error;
728         int i;
729
730         /* Clear memory breakpoints. */
731         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
732                 if (kgdb_break[i].state != BP_ACTIVE)
733                         goto setundefined;
734                 addr = kgdb_break[i].bpt_addr;
735                 error = kgdb_arch_remove_breakpoint(addr,
736                                 kgdb_break[i].saved_instr);
737                 if (error)
738                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
739                            addr);
740 setundefined:
741                 kgdb_break[i].state = BP_UNDEFINED;
742         }
743
744         /* Clear hardware breakpoints. */
745         if (arch_kgdb_ops.remove_all_hw_break)
746                 arch_kgdb_ops.remove_all_hw_break();
747
748         return 0;
749 }
750
751 /*
752  * Remap normal tasks to their real PID, idle tasks to -1 ... -NR_CPUs:
753  */
754 static inline int shadow_pid(int realpid)
755 {
756         if (realpid)
757                 return realpid;
758
759         return -1-raw_smp_processor_id();
760 }
761
762 static char gdbmsgbuf[BUFMAX + 1];
763
764 static void kgdb_msg_write(const char *s, int len)
765 {
766         char *bufptr;
767         int wcount;
768         int i;
769
770         /* 'O'utput */
771         gdbmsgbuf[0] = 'O';
772
773         /* Fill and send buffers... */
774         while (len > 0) {
775                 bufptr = gdbmsgbuf + 1;
776
777                 /* Calculate how many this time */
778                 if ((len << 1) > (BUFMAX - 2))
779                         wcount = (BUFMAX - 2) >> 1;
780                 else
781                         wcount = len;
782
783                 /* Pack in hex chars */
784                 for (i = 0; i < wcount; i++)
785                         bufptr = pack_hex_byte(bufptr, s[i]);
786                 *bufptr = '\0';
787
788                 /* Move up */
789                 s += wcount;
790                 len -= wcount;
791
792                 /* Write packet */
793                 put_packet(gdbmsgbuf);
794         }
795 }
796
797 /*
798  * Return true if there is a valid kgdb I/O module.  Also if no
799  * debugger is attached a message can be printed to the console about
800  * waiting for the debugger to attach.
801  *
802  * The print_wait argument is only to be true when called from inside
803  * the core kgdb_handle_exception, because it will wait for the
804  * debugger to attach.
805  */
806 static int kgdb_io_ready(int print_wait)
807 {
808         if (!kgdb_io_ops)
809                 return 0;
810         if (kgdb_connected)
811                 return 1;
812         if (atomic_read(&kgdb_setting_breakpoint))
813                 return 1;
814         if (print_wait)
815                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
816         return 1;
817 }
818
819 /*
820  * All the functions that start with gdb_cmd are the various
821  * operations to implement the handlers for the gdbserial protocol
822  * where KGDB is communicating with an external debugger
823  */
824
825 /* Handle the '?' status packets */
826 static void gdb_cmd_status(struct kgdb_state *ks)
827 {
828         /*
829          * We know that this packet is only sent
830          * during initial connect.  So to be safe,
831          * we clear out our breakpoints now in case
832          * GDB is reconnecting.
833          */
834         remove_all_break();
835
836         remcom_out_buffer[0] = 'S';
837         pack_hex_byte(&remcom_out_buffer[1], ks->signo);
838 }
839
840 /* Handle the 'g' get registers request */
841 static void gdb_cmd_getregs(struct kgdb_state *ks)
842 {
843         struct task_struct *thread;
844         void *local_debuggerinfo;
845         int i;
846
847         thread = kgdb_usethread;
848         if (!thread) {
849                 thread = kgdb_info[ks->cpu].task;
850                 local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
851         } else {
852                 local_debuggerinfo = NULL;
853                 for (i = 0; i < NR_CPUS; i++) {
854                         /*
855                          * Try to find the task on some other
856                          * or possibly this node if we do not
857                          * find the matching task then we try
858                          * to approximate the results.
859                          */
860                         if (thread == kgdb_info[i].task)
861                                 local_debuggerinfo = kgdb_info[i].debuggerinfo;
862                 }
863         }
864
865         /*
866          * All threads that don't have debuggerinfo should be
867          * in __schedule() sleeping, since all other CPUs
868          * are in kgdb_wait, and thus have debuggerinfo.
869          */
870         if (local_debuggerinfo) {
871                 pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
872         } else {
873                 /*
874                  * Pull stuff saved during switch_to; nothing
875                  * else is accessible (or even particularly
876                  * relevant).
877                  *
878                  * This should be enough for a stack trace.
879                  */
880                 sleeping_thread_to_gdb_regs(gdb_regs, thread);
881         }
882         kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
883 }
884
885 /* Handle the 'G' set registers request */
886 static void gdb_cmd_setregs(struct kgdb_state *ks)
887 {
888         kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
889
890         if (kgdb_usethread && kgdb_usethread != current) {
891                 error_packet(remcom_out_buffer, -EINVAL);
892         } else {
893                 gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
894                 strcpy(remcom_out_buffer, "OK");
895         }
896 }
897
898 /* Handle the 'm' memory read bytes */
899 static void gdb_cmd_memread(struct kgdb_state *ks)
900 {
901         char *ptr = &remcom_in_buffer[1];
902         unsigned long length;
903         unsigned long addr;
904         int err;
905
906         if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
907                                         kgdb_hex2long(&ptr, &length) > 0) {
908                 err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
909                 if (err)
910                         error_packet(remcom_out_buffer, err);
911         } else {
912                 error_packet(remcom_out_buffer, -EINVAL);
913         }
914 }
915
916 /* Handle the 'M' memory write bytes */
917 static void gdb_cmd_memwrite(struct kgdb_state *ks)
918 {
919         int err = write_mem_msg(0);
920
921         if (err)
922                 error_packet(remcom_out_buffer, err);
923         else
924                 strcpy(remcom_out_buffer, "OK");
925 }
926
927 /* Handle the 'X' memory binary write bytes */
928 static void gdb_cmd_binwrite(struct kgdb_state *ks)
929 {
930         int err = write_mem_msg(1);
931
932         if (err)
933                 error_packet(remcom_out_buffer, err);
934         else
935                 strcpy(remcom_out_buffer, "OK");
936 }
937
938 /* Handle the 'D' or 'k', detach or kill packets */
939 static void gdb_cmd_detachkill(struct kgdb_state *ks)
940 {
941         int error;
942
943         /* The detach case */
944         if (remcom_in_buffer[0] == 'D') {
945                 error = remove_all_break();
946                 if (error < 0) {
947                         error_packet(remcom_out_buffer, error);
948                 } else {
949                         strcpy(remcom_out_buffer, "OK");
950                         kgdb_connected = 0;
951                 }
952                 put_packet(remcom_out_buffer);
953         } else {
954                 /*
955                  * Assume the kill case, with no exit code checking,
956                  * trying to force detach the debugger:
957                  */
958                 remove_all_break();
959                 kgdb_connected = 0;
960         }
961 }
962
963 /* Handle the 'R' reboot packets */
964 static int gdb_cmd_reboot(struct kgdb_state *ks)
965 {
966         /* For now, only honor R0 */
967         if (strcmp(remcom_in_buffer, "R0") == 0) {
968                 printk(KERN_CRIT "Executing emergency reboot\n");
969                 strcpy(remcom_out_buffer, "OK");
970                 put_packet(remcom_out_buffer);
971
972                 /*
973                  * Execution should not return from
974                  * machine_emergency_restart()
975                  */
976                 machine_emergency_restart();
977                 kgdb_connected = 0;
978
979                 return 1;
980         }
981         return 0;
982 }
983
984 /* Handle the 'q' query packets */
985 static void gdb_cmd_query(struct kgdb_state *ks)
986 {
987         struct task_struct *thread;
988         unsigned char thref[8];
989         char *ptr;
990         int i;
991
992         switch (remcom_in_buffer[1]) {
993         case 's':
994         case 'f':
995                 if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
996                         error_packet(remcom_out_buffer, -EINVAL);
997                         break;
998                 }
999
1000                 if (remcom_in_buffer[1] == 'f')
1001                         ks->threadid = 1;
1002
1003                 remcom_out_buffer[0] = 'm';
1004                 ptr = remcom_out_buffer + 1;
1005
1006                 for (i = 0; i < 17; ks->threadid++) {
1007                         thread = getthread(ks->linux_regs, ks->threadid);
1008                         if (thread) {
1009                                 int_to_threadref(thref, ks->threadid);
1010                                 pack_threadid(ptr, thref);
1011                                 ptr += BUF_THREAD_ID_SIZE;
1012                                 *(ptr++) = ',';
1013                                 i++;
1014                         }
1015                 }
1016                 *(--ptr) = '\0';
1017                 break;
1018
1019         case 'C':
1020                 /* Current thread id */
1021                 strcpy(remcom_out_buffer, "QC");
1022                 ks->threadid = shadow_pid(current->pid);
1023                 int_to_threadref(thref, ks->threadid);
1024                 pack_threadid(remcom_out_buffer + 2, thref);
1025                 break;
1026         case 'T':
1027                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
1028                         error_packet(remcom_out_buffer, -EINVAL);
1029                         break;
1030                 }
1031                 ks->threadid = 0;
1032                 ptr = remcom_in_buffer + 17;
1033                 kgdb_hex2long(&ptr, &ks->threadid);
1034                 if (!getthread(ks->linux_regs, ks->threadid)) {
1035                         error_packet(remcom_out_buffer, -EINVAL);
1036                         break;
1037                 }
1038                 if (ks->threadid > 0) {
1039                         kgdb_mem2hex(getthread(ks->linux_regs,
1040                                         ks->threadid)->comm,
1041                                         remcom_out_buffer, 16);
1042                 } else {
1043                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
1044
1045                         sprintf(tmpstr, "Shadow task %d for pid 0",
1046                                         (int)(-ks->threadid-1));
1047                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
1048                 }
1049                 break;
1050         }
1051 }
1052
1053 /* Handle the 'H' task query packets */
1054 static void gdb_cmd_task(struct kgdb_state *ks)
1055 {
1056         struct task_struct *thread;
1057         char *ptr;
1058
1059         switch (remcom_in_buffer[1]) {
1060         case 'g':
1061                 ptr = &remcom_in_buffer[2];
1062                 kgdb_hex2long(&ptr, &ks->threadid);
1063                 thread = getthread(ks->linux_regs, ks->threadid);
1064                 if (!thread && ks->threadid > 0) {
1065                         error_packet(remcom_out_buffer, -EINVAL);
1066                         break;
1067                 }
1068                 kgdb_usethread = thread;
1069                 ks->kgdb_usethreadid = ks->threadid;
1070                 strcpy(remcom_out_buffer, "OK");
1071                 break;
1072         case 'c':
1073                 ptr = &remcom_in_buffer[2];
1074                 kgdb_hex2long(&ptr, &ks->threadid);
1075                 if (!ks->threadid) {
1076                         kgdb_contthread = NULL;
1077                 } else {
1078                         thread = getthread(ks->linux_regs, ks->threadid);
1079                         if (!thread && ks->threadid > 0) {
1080                                 error_packet(remcom_out_buffer, -EINVAL);
1081                                 break;
1082                         }
1083                         kgdb_contthread = thread;
1084                 }
1085                 strcpy(remcom_out_buffer, "OK");
1086                 break;
1087         }
1088 }
1089
1090 /* Handle the 'T' thread query packets */
1091 static void gdb_cmd_thread(struct kgdb_state *ks)
1092 {
1093         char *ptr = &remcom_in_buffer[1];
1094         struct task_struct *thread;
1095
1096         kgdb_hex2long(&ptr, &ks->threadid);
1097         thread = getthread(ks->linux_regs, ks->threadid);
1098         if (thread)
1099                 strcpy(remcom_out_buffer, "OK");
1100         else
1101                 error_packet(remcom_out_buffer, -EINVAL);
1102 }
1103
1104 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
1105 static void gdb_cmd_break(struct kgdb_state *ks)
1106 {
1107         /*
1108          * Since GDB-5.3, it's been drafted that '0' is a software
1109          * breakpoint, '1' is a hardware breakpoint, so let's do that.
1110          */
1111         char *bpt_type = &remcom_in_buffer[1];
1112         char *ptr = &remcom_in_buffer[2];
1113         unsigned long addr;
1114         unsigned long length;
1115         int error = 0;
1116
1117         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
1118                 /* Unsupported */
1119                 if (*bpt_type > '4')
1120                         return;
1121         } else {
1122                 if (*bpt_type != '0' && *bpt_type != '1')
1123                         /* Unsupported. */
1124                         return;
1125         }
1126
1127         /*
1128          * Test if this is a hardware breakpoint, and
1129          * if we support it:
1130          */
1131         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
1132                 /* Unsupported. */
1133                 return;
1134
1135         if (*(ptr++) != ',') {
1136                 error_packet(remcom_out_buffer, -EINVAL);
1137                 return;
1138         }
1139         if (!kgdb_hex2long(&ptr, &addr)) {
1140                 error_packet(remcom_out_buffer, -EINVAL);
1141                 return;
1142         }
1143         if (*(ptr++) != ',' ||
1144                 !kgdb_hex2long(&ptr, &length)) {
1145                 error_packet(remcom_out_buffer, -EINVAL);
1146                 return;
1147         }
1148
1149         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
1150                 error = kgdb_set_sw_break(addr);
1151         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
1152                 error = kgdb_remove_sw_break(addr);
1153         else if (remcom_in_buffer[0] == 'Z')
1154                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
1155                         (int)length, *bpt_type - '0');
1156         else if (remcom_in_buffer[0] == 'z')
1157                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
1158                         (int) length, *bpt_type - '0');
1159
1160         if (error == 0)
1161                 strcpy(remcom_out_buffer, "OK");
1162         else
1163                 error_packet(remcom_out_buffer, error);
1164 }
1165
1166 /* Handle the 'C' signal / exception passing packets */
1167 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
1168 {
1169         /* C09 == pass exception
1170          * C15 == detach kgdb, pass exception
1171          */
1172         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
1173
1174                 ks->pass_exception = 1;
1175                 remcom_in_buffer[0] = 'c';
1176
1177         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
1178
1179                 ks->pass_exception = 1;
1180                 remcom_in_buffer[0] = 'D';
1181                 remove_all_break();
1182                 kgdb_connected = 0;
1183                 return 1;
1184
1185         } else {
1186                 error_packet(remcom_out_buffer, -EINVAL);
1187                 return 0;
1188         }
1189
1190         /* Indicate fall through */
1191         return -1;
1192 }
1193
1194 /*
1195  * This function performs all gdbserial command procesing
1196  */
1197 static int gdb_serial_stub(struct kgdb_state *ks)
1198 {
1199         int error = 0;
1200         int tmp;
1201
1202         /* Clear the out buffer. */
1203         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1204
1205         if (kgdb_connected) {
1206                 unsigned char thref[8];
1207                 char *ptr;
1208
1209                 /* Reply to host that an exception has occurred */
1210                 ptr = remcom_out_buffer;
1211                 *ptr++ = 'T';
1212                 ptr = pack_hex_byte(ptr, ks->signo);
1213                 ptr += strlen(strcpy(ptr, "thread:"));
1214                 int_to_threadref(thref, shadow_pid(current->pid));
1215                 ptr = pack_threadid(ptr, thref);
1216                 *ptr++ = ';';
1217                 put_packet(remcom_out_buffer);
1218         }
1219
1220         kgdb_usethread = kgdb_info[ks->cpu].task;
1221         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
1222         ks->pass_exception = 0;
1223
1224         while (1) {
1225                 error = 0;
1226
1227                 /* Clear the out buffer. */
1228                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1229
1230                 get_packet(remcom_in_buffer);
1231
1232                 switch (remcom_in_buffer[0]) {
1233                 case '?': /* gdbserial status */
1234                         gdb_cmd_status(ks);
1235                         break;
1236                 case 'g': /* return the value of the CPU registers */
1237                         gdb_cmd_getregs(ks);
1238                         break;
1239                 case 'G': /* set the value of the CPU registers - return OK */
1240                         gdb_cmd_setregs(ks);
1241                         break;
1242                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1243                         gdb_cmd_memread(ks);
1244                         break;
1245                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1246                         gdb_cmd_memwrite(ks);
1247                         break;
1248                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1249                         gdb_cmd_binwrite(ks);
1250                         break;
1251                         /* kill or detach. KGDB should treat this like a
1252                          * continue.
1253                          */
1254                 case 'D': /* Debugger detach */
1255                 case 'k': /* Debugger detach via kill */
1256                         gdb_cmd_detachkill(ks);
1257                         goto default_handle;
1258                 case 'R': /* Reboot */
1259                         if (gdb_cmd_reboot(ks))
1260                                 goto default_handle;
1261                         break;
1262                 case 'q': /* query command */
1263                         gdb_cmd_query(ks);
1264                         break;
1265                 case 'H': /* task related */
1266                         gdb_cmd_task(ks);
1267                         break;
1268                 case 'T': /* Query thread status */
1269                         gdb_cmd_thread(ks);
1270                         break;
1271                 case 'z': /* Break point remove */
1272                 case 'Z': /* Break point set */
1273                         gdb_cmd_break(ks);
1274                         break;
1275                 case 'C': /* Exception passing */
1276                         tmp = gdb_cmd_exception_pass(ks);
1277                         if (tmp > 0)
1278                                 goto default_handle;
1279                         if (tmp == 0)
1280                                 break;
1281                         /* Fall through on tmp < 0 */
1282                 case 'c': /* Continue packet */
1283                 case 's': /* Single step packet */
1284                         if (kgdb_contthread && kgdb_contthread != current) {
1285                                 /* Can't switch threads in kgdb */
1286                                 error_packet(remcom_out_buffer, -EINVAL);
1287                                 break;
1288                         }
1289                         kgdb_activate_sw_breakpoints();
1290                         /* Fall through to default processing */
1291                 default:
1292 default_handle:
1293                         error = kgdb_arch_handle_exception(ks->ex_vector,
1294                                                 ks->signo,
1295                                                 ks->err_code,
1296                                                 remcom_in_buffer,
1297                                                 remcom_out_buffer,
1298                                                 ks->linux_regs);
1299                         /*
1300                          * Leave cmd processing on error, detach,
1301                          * kill, continue, or single step.
1302                          */
1303                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1304                             remcom_in_buffer[0] == 'k') {
1305                                 error = 0;
1306                                 goto kgdb_exit;
1307                         }
1308
1309                 }
1310
1311                 /* reply to the request */
1312                 put_packet(remcom_out_buffer);
1313         }
1314
1315 kgdb_exit:
1316         if (ks->pass_exception)
1317                 error = 1;
1318         return error;
1319 }
1320
1321 static int kgdb_reenter_check(struct kgdb_state *ks)
1322 {
1323         unsigned long addr;
1324
1325         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
1326                 return 0;
1327
1328         /* Panic on recursive debugger calls: */
1329         exception_level++;
1330         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
1331         kgdb_deactivate_sw_breakpoints();
1332
1333         /*
1334          * If the break point removed ok at the place exception
1335          * occurred, try to recover and print a warning to the end
1336          * user because the user planted a breakpoint in a place that
1337          * KGDB needs in order to function.
1338          */
1339         if (kgdb_remove_sw_break(addr) == 0) {
1340                 exception_level = 0;
1341                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1342                 kgdb_activate_sw_breakpoints();
1343                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
1344                         addr);
1345                 WARN_ON_ONCE(1);
1346
1347                 return 1;
1348         }
1349         remove_all_break();
1350         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1351
1352         if (exception_level > 1) {
1353                 dump_stack();
1354                 panic("Recursive entry to debugger");
1355         }
1356
1357         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
1358         dump_stack();
1359         panic("Recursive entry to debugger");
1360
1361         return 1;
1362 }
1363
1364 /*
1365  * kgdb_handle_exception() - main entry point from a kernel exception
1366  *
1367  * Locking hierarchy:
1368  *      interface locks, if any (begin_session)
1369  *      kgdb lock (kgdb_active)
1370  */
1371 int
1372 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
1373 {
1374         struct kgdb_state kgdb_var;
1375         struct kgdb_state *ks = &kgdb_var;
1376         unsigned long flags;
1377         int error = 0;
1378         int i, cpu;
1379
1380         ks->cpu                 = raw_smp_processor_id();
1381         ks->ex_vector           = evector;
1382         ks->signo               = signo;
1383         ks->ex_vector           = evector;
1384         ks->err_code            = ecode;
1385         ks->kgdb_usethreadid    = 0;
1386         ks->linux_regs          = regs;
1387
1388         if (kgdb_reenter_check(ks))
1389                 return 0; /* Ouch, double exception ! */
1390
1391 acquirelock:
1392         /*
1393          * Interrupts will be restored by the 'trap return' code, except when
1394          * single stepping.
1395          */
1396         local_irq_save(flags);
1397
1398         cpu = raw_smp_processor_id();
1399
1400         /*
1401          * Acquire the kgdb_active lock:
1402          */
1403         while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
1404                 cpu_relax();
1405
1406         /*
1407          * Do not start the debugger connection on this CPU if the last
1408          * instance of the exception handler wanted to come into the
1409          * debugger on a different CPU via a single step
1410          */
1411         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
1412             atomic_read(&kgdb_cpu_doing_single_step) != cpu) {
1413
1414                 atomic_set(&kgdb_active, -1);
1415                 clocksource_touch_watchdog();
1416                 local_irq_restore(flags);
1417
1418                 goto acquirelock;
1419         }
1420
1421         if (!kgdb_io_ready(1)) {
1422                 error = 1;
1423                 goto kgdb_restore; /* No I/O connection, so resume the system */
1424         }
1425
1426         /*
1427          * Don't enter if we have hit a removed breakpoint.
1428          */
1429         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
1430                 goto kgdb_restore;
1431
1432         /* Call the I/O driver's pre_exception routine */
1433         if (kgdb_io_ops->pre_exception)
1434                 kgdb_io_ops->pre_exception();
1435
1436         kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
1437         kgdb_info[ks->cpu].task = current;
1438
1439         kgdb_disable_hw_debug(ks->linux_regs);
1440
1441         /*
1442          * Get the passive CPU lock which will hold all the non-primary
1443          * CPU in a spin state while the debugger is active
1444          */
1445         if (!kgdb_single_step || !kgdb_contthread) {
1446                 for (i = 0; i < NR_CPUS; i++)
1447                         atomic_set(&passive_cpu_wait[i], 1);
1448         }
1449
1450 #ifdef CONFIG_SMP
1451         /* Signal the other CPUs to enter kgdb_wait() */
1452         if ((!kgdb_single_step || !kgdb_contthread) && kgdb_do_roundup)
1453                 kgdb_roundup_cpus(flags);
1454 #endif
1455
1456         /*
1457          * spin_lock code is good enough as a barrier so we don't
1458          * need one here:
1459          */
1460         atomic_set(&cpu_in_kgdb[ks->cpu], 1);
1461
1462         /*
1463          * Wait for the other CPUs to be notified and be waiting for us:
1464          */
1465         for_each_online_cpu(i) {
1466                 while (!atomic_read(&cpu_in_kgdb[i]))
1467                         cpu_relax();
1468         }
1469
1470         /*
1471          * At this point the primary processor is completely
1472          * in the debugger and all secondary CPUs are quiescent
1473          */
1474         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
1475         kgdb_deactivate_sw_breakpoints();
1476         kgdb_single_step = 0;
1477         kgdb_contthread = NULL;
1478         exception_level = 0;
1479
1480         /* Talk to debugger with gdbserial protocol */
1481         error = gdb_serial_stub(ks);
1482
1483         /* Call the I/O driver's post_exception routine */
1484         if (kgdb_io_ops->post_exception)
1485                 kgdb_io_ops->post_exception();
1486
1487         kgdb_info[ks->cpu].debuggerinfo = NULL;
1488         kgdb_info[ks->cpu].task = NULL;
1489         atomic_set(&cpu_in_kgdb[ks->cpu], 0);
1490
1491         if (!kgdb_single_step || !kgdb_contthread) {
1492                 for (i = NR_CPUS-1; i >= 0; i--)
1493                         atomic_set(&passive_cpu_wait[i], 0);
1494                 /*
1495                  * Wait till all the CPUs have quit
1496                  * from the debugger.
1497                  */
1498                 for_each_online_cpu(i) {
1499                         while (atomic_read(&cpu_in_kgdb[i]))
1500                                 cpu_relax();
1501                 }
1502         }
1503
1504 kgdb_restore:
1505         /* Free kgdb_active */
1506         atomic_set(&kgdb_active, -1);
1507         clocksource_touch_watchdog();
1508         local_irq_restore(flags);
1509
1510         return error;
1511 }
1512
1513 int kgdb_nmicallback(int cpu, void *regs)
1514 {
1515 #ifdef CONFIG_SMP
1516         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
1517                         atomic_read(&kgdb_active) != cpu) {
1518                 kgdb_wait((struct pt_regs *)regs);
1519                 return 0;
1520         }
1521 #endif
1522         return 1;
1523 }
1524
1525 void kgdb_console_write(struct console *co, const char *s, unsigned count)
1526 {
1527         unsigned long flags;
1528
1529         /* If we're debugging, or KGDB has not connected, don't try
1530          * and print. */
1531         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
1532                 return;
1533
1534         local_irq_save(flags);
1535         kgdb_msg_write(s, count);
1536         local_irq_restore(flags);
1537 }
1538
1539 static struct console kgdbcons = {
1540         .name           = "kgdb",
1541         .write          = kgdb_console_write,
1542         .flags          = CON_PRINTBUFFER | CON_ENABLED,
1543         .index          = -1,
1544 };
1545
1546 #ifdef CONFIG_MAGIC_SYSRQ
1547 static void sysrq_handle_gdb(int key, struct tty_struct *tty)
1548 {
1549         if (!kgdb_io_ops) {
1550                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
1551                 return;
1552         }
1553         if (!kgdb_connected)
1554                 printk(KERN_CRIT "Entering KGDB\n");
1555
1556         kgdb_breakpoint();
1557 }
1558
1559 static struct sysrq_key_op sysrq_gdb_op = {
1560         .handler        = sysrq_handle_gdb,
1561         .help_msg       = "Gdb",
1562         .action_msg     = "GDB",
1563 };
1564 #endif
1565
1566 static void kgdb_register_callbacks(void)
1567 {
1568         if (!kgdb_io_module_registered) {
1569                 kgdb_io_module_registered = 1;
1570                 kgdb_arch_init();
1571 #ifdef CONFIG_MAGIC_SYSRQ
1572                 register_sysrq_key('g', &sysrq_gdb_op);
1573 #endif
1574                 if (kgdb_use_con && !kgdb_con_registered) {
1575                         register_console(&kgdbcons);
1576                         kgdb_con_registered = 1;
1577                 }
1578         }
1579 }
1580
1581 static void kgdb_unregister_callbacks(void)
1582 {
1583         /*
1584          * When this routine is called KGDB should unregister from the
1585          * panic handler and clean up, making sure it is not handling any
1586          * break exceptions at the time.
1587          */
1588         if (kgdb_io_module_registered) {
1589                 kgdb_io_module_registered = 0;
1590                 kgdb_arch_exit();
1591 #ifdef CONFIG_MAGIC_SYSRQ
1592                 unregister_sysrq_key('g', &sysrq_gdb_op);
1593 #endif
1594                 if (kgdb_con_registered) {
1595                         unregister_console(&kgdbcons);
1596                         kgdb_con_registered = 0;
1597                 }
1598         }
1599 }
1600
1601 static void kgdb_initial_breakpoint(void)
1602 {
1603         kgdb_break_asap = 0;
1604
1605         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
1606         kgdb_breakpoint();
1607 }
1608
1609 /**
1610  *      kgdb_register_io_module - register KGDB IO module
1611  *      @new_kgdb_io_ops: the io ops vector
1612  *
1613  *      Register it with the KGDB core.
1614  */
1615 int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
1616 {
1617         int err;
1618
1619         spin_lock(&kgdb_registration_lock);
1620
1621         if (kgdb_io_ops) {
1622                 spin_unlock(&kgdb_registration_lock);
1623
1624                 printk(KERN_ERR "kgdb: Another I/O driver is already "
1625                                 "registered with KGDB.\n");
1626                 return -EBUSY;
1627         }
1628
1629         if (new_kgdb_io_ops->init) {
1630                 err = new_kgdb_io_ops->init();
1631                 if (err) {
1632                         spin_unlock(&kgdb_registration_lock);
1633                         return err;
1634                 }
1635         }
1636
1637         kgdb_io_ops = new_kgdb_io_ops;
1638
1639         spin_unlock(&kgdb_registration_lock);
1640
1641         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
1642                new_kgdb_io_ops->name);
1643
1644         /* Arm KGDB now. */
1645         kgdb_register_callbacks();
1646
1647         if (kgdb_break_asap)
1648                 kgdb_initial_breakpoint();
1649
1650         return 0;
1651 }
1652 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1653
1654 /**
1655  *      kkgdb_unregister_io_module - unregister KGDB IO module
1656  *      @old_kgdb_io_ops: the io ops vector
1657  *
1658  *      Unregister it with the KGDB core.
1659  */
1660 void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
1661 {
1662         BUG_ON(kgdb_connected);
1663
1664         /*
1665          * KGDB is no longer able to communicate out, so
1666          * unregister our callbacks and reset state.
1667          */
1668         kgdb_unregister_callbacks();
1669
1670         spin_lock(&kgdb_registration_lock);
1671
1672         WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
1673         kgdb_io_ops = NULL;
1674
1675         spin_unlock(&kgdb_registration_lock);
1676
1677         printk(KERN_INFO
1678                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
1679                 old_kgdb_io_ops->name);
1680 }
1681 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1682
1683 /**
1684  * kgdb_breakpoint - generate breakpoint exception
1685  *
1686  * This function will generate a breakpoint exception.  It is used at the
1687  * beginning of a program to sync up with a debugger and can be used
1688  * otherwise as a quick means to stop program execution and "break" into
1689  * the debugger.
1690  */
1691 void kgdb_breakpoint(void)
1692 {
1693         atomic_set(&kgdb_setting_breakpoint, 1);
1694         wmb(); /* Sync point before breakpoint */
1695         arch_kgdb_breakpoint();
1696         wmb(); /* Sync point after breakpoint */
1697         atomic_set(&kgdb_setting_breakpoint, 0);
1698 }
1699 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1700
1701 static int __init opt_kgdb_wait(char *str)
1702 {
1703         kgdb_break_asap = 1;
1704
1705         if (kgdb_io_module_registered)
1706                 kgdb_initial_breakpoint();
1707
1708         return 0;
1709 }
1710
1711 early_param("kgdbwait", opt_kgdb_wait);