kgdb: allow for cpu switch when single stepping
[sfrench/cifs-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 #define KGDB_MAX_THREAD_QUERY 17
60 struct kgdb_state {
61         int                     ex_vector;
62         int                     signo;
63         int                     err_code;
64         int                     cpu;
65         int                     pass_exception;
66         unsigned long           thr_query;
67         unsigned long           threadid;
68         long                    kgdb_usethreadid;
69         struct pt_regs          *linux_regs;
70 };
71
72 static struct debuggerinfo_struct {
73         void                    *debuggerinfo;
74         struct task_struct      *task;
75 } kgdb_info[NR_CPUS];
76
77 /**
78  * kgdb_connected - Is a host GDB connected to us?
79  */
80 int                             kgdb_connected;
81 EXPORT_SYMBOL_GPL(kgdb_connected);
82
83 /* All the KGDB handlers are installed */
84 static int                      kgdb_io_module_registered;
85
86 /* Guard for recursive entry */
87 static int                      exception_level;
88
89 static struct kgdb_io           *kgdb_io_ops;
90 static DEFINE_SPINLOCK(kgdb_registration_lock);
91
92 /* kgdb console driver is loaded */
93 static int kgdb_con_registered;
94 /* determine if kgdb console output should be used */
95 static int kgdb_use_con;
96
97 static int __init opt_kgdb_con(char *str)
98 {
99         kgdb_use_con = 1;
100         return 0;
101 }
102
103 early_param("kgdbcon", opt_kgdb_con);
104
105 module_param(kgdb_use_con, int, 0644);
106
107 /*
108  * Holds information about breakpoints in a kernel. These breakpoints are
109  * added and removed by gdb.
110  */
111 static struct kgdb_bkpt         kgdb_break[KGDB_MAX_BREAKPOINTS] = {
112         [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED }
113 };
114
115 /*
116  * The CPU# of the active CPU, or -1 if none:
117  */
118 atomic_t                        kgdb_active = ATOMIC_INIT(-1);
119
120 /*
121  * We use NR_CPUs not PERCPU, in case kgdb is used to debug early
122  * bootup code (which might not have percpu set up yet):
123  */
124 static atomic_t                 passive_cpu_wait[NR_CPUS];
125 static atomic_t                 cpu_in_kgdb[NR_CPUS];
126 atomic_t                        kgdb_setting_breakpoint;
127
128 struct task_struct              *kgdb_usethread;
129 struct task_struct              *kgdb_contthread;
130
131 int                             kgdb_single_step;
132 pid_t                           kgdb_sstep_pid;
133
134 /* Our I/O buffers. */
135 static char                     remcom_in_buffer[BUFMAX];
136 static char                     remcom_out_buffer[BUFMAX];
137
138 /* Storage for the registers, in GDB format. */
139 static unsigned long            gdb_regs[(NUMREGBYTES +
140                                         sizeof(unsigned long) - 1) /
141                                         sizeof(unsigned long)];
142
143 /* to keep track of the CPU which is doing the single stepping*/
144 atomic_t                        kgdb_cpu_doing_single_step = ATOMIC_INIT(-1);
145
146 /*
147  * If you are debugging a problem where roundup (the collection of
148  * all other CPUs) is a problem [this should be extremely rare],
149  * then use the nokgdbroundup option to avoid roundup. In that case
150  * the other CPUs might interfere with your debugging context, so
151  * use this with care:
152  */
153 static int kgdb_do_roundup = 1;
154
155 static int __init opt_nokgdbroundup(char *str)
156 {
157         kgdb_do_roundup = 0;
158
159         return 0;
160 }
161
162 early_param("nokgdbroundup", opt_nokgdbroundup);
163
164 /*
165  * Finally, some KGDB code :-)
166  */
167
168 /*
169  * Weak aliases for breakpoint management,
170  * can be overriden by architectures when needed:
171  */
172 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
173 {
174         int err;
175
176         err = probe_kernel_read(saved_instr, (char *)addr, BREAK_INSTR_SIZE);
177         if (err)
178                 return err;
179
180         return probe_kernel_write((char *)addr, arch_kgdb_ops.gdb_bpt_instr,
181                                   BREAK_INSTR_SIZE);
182 }
183
184 int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
185 {
186         return probe_kernel_write((char *)addr,
187                                   (char *)bundle, BREAK_INSTR_SIZE);
188 }
189
190 int __weak kgdb_validate_break_address(unsigned long addr)
191 {
192         char tmp_variable[BREAK_INSTR_SIZE];
193         int err;
194         /* Validate setting the breakpoint and then removing it.  In the
195          * remove fails, the kernel needs to emit a bad message because we
196          * are deep trouble not being able to put things back the way we
197          * found them.
198          */
199         err = kgdb_arch_set_breakpoint(addr, tmp_variable);
200         if (err)
201                 return err;
202         err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
203         if (err)
204                 printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
205                    "memory destroyed at: %lx", addr);
206         return err;
207 }
208
209 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
210 {
211         return instruction_pointer(regs);
212 }
213
214 int __weak kgdb_arch_init(void)
215 {
216         return 0;
217 }
218
219 int __weak kgdb_skipexception(int exception, struct pt_regs *regs)
220 {
221         return 0;
222 }
223
224 void __weak
225 kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
226 {
227         return;
228 }
229
230 /**
231  *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
232  *      @regs: Current &struct pt_regs.
233  *
234  *      This function will be called if the particular architecture must
235  *      disable hardware debugging while it is processing gdb packets or
236  *      handling exception.
237  */
238 void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
239 {
240 }
241
242 /*
243  * GDB remote protocol parser:
244  */
245
246 static int hex(char ch)
247 {
248         if ((ch >= 'a') && (ch <= 'f'))
249                 return ch - 'a' + 10;
250         if ((ch >= '0') && (ch <= '9'))
251                 return ch - '0';
252         if ((ch >= 'A') && (ch <= 'F'))
253                 return ch - 'A' + 10;
254         return -1;
255 }
256
257 /* scan for the sequence $<data>#<checksum> */
258 static void get_packet(char *buffer)
259 {
260         unsigned char checksum;
261         unsigned char xmitcsum;
262         int count;
263         char ch;
264
265         do {
266                 /*
267                  * Spin and wait around for the start character, ignore all
268                  * other characters:
269                  */
270                 while ((ch = (kgdb_io_ops->read_char())) != '$')
271                         /* nothing */;
272
273                 kgdb_connected = 1;
274                 checksum = 0;
275                 xmitcsum = -1;
276
277                 count = 0;
278
279                 /*
280                  * now, read until a # or end of buffer is found:
281                  */
282                 while (count < (BUFMAX - 1)) {
283                         ch = kgdb_io_ops->read_char();
284                         if (ch == '#')
285                                 break;
286                         checksum = checksum + ch;
287                         buffer[count] = ch;
288                         count = count + 1;
289                 }
290                 buffer[count] = 0;
291
292                 if (ch == '#') {
293                         xmitcsum = hex(kgdb_io_ops->read_char()) << 4;
294                         xmitcsum += hex(kgdb_io_ops->read_char());
295
296                         if (checksum != xmitcsum)
297                                 /* failed checksum */
298                                 kgdb_io_ops->write_char('-');
299                         else
300                                 /* successful transfer */
301                                 kgdb_io_ops->write_char('+');
302                         if (kgdb_io_ops->flush)
303                                 kgdb_io_ops->flush();
304                 }
305         } while (checksum != xmitcsum);
306 }
307
308 /*
309  * Send the packet in buffer.
310  * Check for gdb connection if asked for.
311  */
312 static void put_packet(char *buffer)
313 {
314         unsigned char checksum;
315         int count;
316         char ch;
317
318         /*
319          * $<packet info>#<checksum>.
320          */
321         while (1) {
322                 kgdb_io_ops->write_char('$');
323                 checksum = 0;
324                 count = 0;
325
326                 while ((ch = buffer[count])) {
327                         kgdb_io_ops->write_char(ch);
328                         checksum += ch;
329                         count++;
330                 }
331
332                 kgdb_io_ops->write_char('#');
333                 kgdb_io_ops->write_char(hex_asc_hi(checksum));
334                 kgdb_io_ops->write_char(hex_asc_lo(checksum));
335                 if (kgdb_io_ops->flush)
336                         kgdb_io_ops->flush();
337
338                 /* Now see what we get in reply. */
339                 ch = kgdb_io_ops->read_char();
340
341                 if (ch == 3)
342                         ch = kgdb_io_ops->read_char();
343
344                 /* If we get an ACK, we are done. */
345                 if (ch == '+')
346                         return;
347
348                 /*
349                  * If we get the start of another packet, this means
350                  * that GDB is attempting to reconnect.  We will NAK
351                  * the packet being sent, and stop trying to send this
352                  * packet.
353                  */
354                 if (ch == '$') {
355                         kgdb_io_ops->write_char('-');
356                         if (kgdb_io_ops->flush)
357                                 kgdb_io_ops->flush();
358                         return;
359                 }
360         }
361 }
362
363 /*
364  * Convert the memory pointed to by mem into hex, placing result in buf.
365  * Return a pointer to the last char put in buf (null). May return an error.
366  */
367 int kgdb_mem2hex(char *mem, char *buf, int count)
368 {
369         char *tmp;
370         int err;
371
372         /*
373          * We use the upper half of buf as an intermediate buffer for the
374          * raw memory copy.  Hex conversion will work against this one.
375          */
376         tmp = buf + count;
377
378         err = probe_kernel_read(tmp, mem, count);
379         if (!err) {
380                 while (count > 0) {
381                         buf = pack_hex_byte(buf, *tmp);
382                         tmp++;
383                         count--;
384                 }
385
386                 *buf = 0;
387         }
388
389         return err;
390 }
391
392 /*
393  * Copy the binary array pointed to by buf into mem.  Fix $, #, and
394  * 0x7d escaped with 0x7d.  Return a pointer to the character after
395  * the last byte written.
396  */
397 static int kgdb_ebin2mem(char *buf, char *mem, int count)
398 {
399         int err = 0;
400         char c;
401
402         while (count-- > 0) {
403                 c = *buf++;
404                 if (c == 0x7d)
405                         c = *buf++ ^ 0x20;
406
407                 err = probe_kernel_write(mem, &c, 1);
408                 if (err)
409                         break;
410
411                 mem++;
412         }
413
414         return err;
415 }
416
417 /*
418  * Convert the hex array pointed to by buf into binary to be placed in mem.
419  * Return a pointer to the character AFTER the last byte written.
420  * May return an error.
421  */
422 int kgdb_hex2mem(char *buf, char *mem, int count)
423 {
424         char *tmp_raw;
425         char *tmp_hex;
426
427         /*
428          * We use the upper half of buf as an intermediate buffer for the
429          * raw memory that is converted from hex.
430          */
431         tmp_raw = buf + count * 2;
432
433         tmp_hex = tmp_raw - 1;
434         while (tmp_hex >= buf) {
435                 tmp_raw--;
436                 *tmp_raw = hex(*tmp_hex--);
437                 *tmp_raw |= hex(*tmp_hex--) << 4;
438         }
439
440         return probe_kernel_write(mem, tmp_raw, count);
441 }
442
443 /*
444  * While we find nice hex chars, build a long_val.
445  * Return number of chars processed.
446  */
447 int kgdb_hex2long(char **ptr, unsigned long *long_val)
448 {
449         int hex_val;
450         int num = 0;
451         int negate = 0;
452
453         *long_val = 0;
454
455         if (**ptr == '-') {
456                 negate = 1;
457                 (*ptr)++;
458         }
459         while (**ptr) {
460                 hex_val = hex(**ptr);
461                 if (hex_val < 0)
462                         break;
463
464                 *long_val = (*long_val << 4) | hex_val;
465                 num++;
466                 (*ptr)++;
467         }
468
469         if (negate)
470                 *long_val = -*long_val;
471
472         return num;
473 }
474
475 /* Write memory due to an 'M' or 'X' packet. */
476 static int write_mem_msg(int binary)
477 {
478         char *ptr = &remcom_in_buffer[1];
479         unsigned long addr;
480         unsigned long length;
481         int err;
482
483         if (kgdb_hex2long(&ptr, &addr) > 0 && *(ptr++) == ',' &&
484             kgdb_hex2long(&ptr, &length) > 0 && *(ptr++) == ':') {
485                 if (binary)
486                         err = kgdb_ebin2mem(ptr, (char *)addr, length);
487                 else
488                         err = kgdb_hex2mem(ptr, (char *)addr, length);
489                 if (err)
490                         return err;
491                 if (CACHE_FLUSH_IS_SAFE)
492                         flush_icache_range(addr, addr + length);
493                 return 0;
494         }
495
496         return -EINVAL;
497 }
498
499 static void error_packet(char *pkt, int error)
500 {
501         error = -error;
502         pkt[0] = 'E';
503         pkt[1] = hex_asc[(error / 10)];
504         pkt[2] = hex_asc[(error % 10)];
505         pkt[3] = '\0';
506 }
507
508 /*
509  * Thread ID accessors. We represent a flat TID space to GDB, where
510  * the per CPU idle threads (which under Linux all have PID 0) are
511  * remapped to negative TIDs.
512  */
513
514 #define BUF_THREAD_ID_SIZE      16
515
516 static char *pack_threadid(char *pkt, unsigned char *id)
517 {
518         char *limit;
519
520         limit = pkt + BUF_THREAD_ID_SIZE;
521         while (pkt < limit)
522                 pkt = pack_hex_byte(pkt, *id++);
523
524         return pkt;
525 }
526
527 static void int_to_threadref(unsigned char *id, int value)
528 {
529         unsigned char *scan;
530         int i = 4;
531
532         scan = (unsigned char *)id;
533         while (i--)
534                 *scan++ = 0;
535         put_unaligned_be32(value, scan);
536 }
537
538 static struct task_struct *getthread(struct pt_regs *regs, int tid)
539 {
540         /*
541          * Non-positive TIDs are remapped to the cpu shadow information
542          */
543         if (tid == 0 || tid == -1)
544                 tid = -atomic_read(&kgdb_active) - 2;
545         if (tid < -1 && tid > -NR_CPUS - 2) {
546                 if (kgdb_info[-tid - 2].task)
547                         return kgdb_info[-tid - 2].task;
548                 else
549                         return idle_task(-tid - 2);
550         }
551         if (tid <= 0) {
552                 printk(KERN_ERR "KGDB: Internal thread select error\n");
553                 dump_stack();
554                 return NULL;
555         }
556
557         /*
558          * find_task_by_pid_ns() does not take the tasklist lock anymore
559          * but is nicely RCU locked - hence is a pretty resilient
560          * thing to use:
561          */
562         return find_task_by_pid_ns(tid, &init_pid_ns);
563 }
564
565 /*
566  * CPU debug state control:
567  */
568
569 #ifdef CONFIG_SMP
570 static void kgdb_wait(struct pt_regs *regs)
571 {
572         unsigned long flags;
573         int cpu;
574
575         local_irq_save(flags);
576         cpu = raw_smp_processor_id();
577         kgdb_info[cpu].debuggerinfo = regs;
578         kgdb_info[cpu].task = current;
579         /*
580          * Make sure the above info reaches the primary CPU before
581          * our cpu_in_kgdb[] flag setting does:
582          */
583         smp_wmb();
584         atomic_set(&cpu_in_kgdb[cpu], 1);
585
586         /* Wait till primary CPU is done with debugging */
587         while (atomic_read(&passive_cpu_wait[cpu]))
588                 cpu_relax();
589
590         kgdb_info[cpu].debuggerinfo = NULL;
591         kgdb_info[cpu].task = NULL;
592
593         /* fix up hardware debug registers on local cpu */
594         if (arch_kgdb_ops.correct_hw_break)
595                 arch_kgdb_ops.correct_hw_break();
596
597         /* Signal the primary CPU that we are done: */
598         atomic_set(&cpu_in_kgdb[cpu], 0);
599         touch_softlockup_watchdog();
600         clocksource_touch_watchdog();
601         local_irq_restore(flags);
602 }
603 #endif
604
605 /*
606  * Some architectures need cache flushes when we set/clear a
607  * breakpoint:
608  */
609 static void kgdb_flush_swbreak_addr(unsigned long addr)
610 {
611         if (!CACHE_FLUSH_IS_SAFE)
612                 return;
613
614         if (current->mm && current->mm->mmap_cache) {
615                 flush_cache_range(current->mm->mmap_cache,
616                                   addr, addr + BREAK_INSTR_SIZE);
617         }
618         /* Force flush instruction cache if it was outside the mm */
619         flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
620 }
621
622 /*
623  * SW breakpoint management:
624  */
625 static int kgdb_activate_sw_breakpoints(void)
626 {
627         unsigned long addr;
628         int error = 0;
629         int i;
630
631         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
632                 if (kgdb_break[i].state != BP_SET)
633                         continue;
634
635                 addr = kgdb_break[i].bpt_addr;
636                 error = kgdb_arch_set_breakpoint(addr,
637                                 kgdb_break[i].saved_instr);
638                 if (error)
639                         return error;
640
641                 kgdb_flush_swbreak_addr(addr);
642                 kgdb_break[i].state = BP_ACTIVE;
643         }
644         return 0;
645 }
646
647 static int kgdb_set_sw_break(unsigned long addr)
648 {
649         int err = kgdb_validate_break_address(addr);
650         int breakno = -1;
651         int i;
652
653         if (err)
654                 return err;
655
656         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
657                 if ((kgdb_break[i].state == BP_SET) &&
658                                         (kgdb_break[i].bpt_addr == addr))
659                         return -EEXIST;
660         }
661         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
662                 if (kgdb_break[i].state == BP_REMOVED &&
663                                         kgdb_break[i].bpt_addr == addr) {
664                         breakno = i;
665                         break;
666                 }
667         }
668
669         if (breakno == -1) {
670                 for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
671                         if (kgdb_break[i].state == BP_UNDEFINED) {
672                                 breakno = i;
673                                 break;
674                         }
675                 }
676         }
677
678         if (breakno == -1)
679                 return -E2BIG;
680
681         kgdb_break[breakno].state = BP_SET;
682         kgdb_break[breakno].type = BP_BREAKPOINT;
683         kgdb_break[breakno].bpt_addr = addr;
684
685         return 0;
686 }
687
688 static int kgdb_deactivate_sw_breakpoints(void)
689 {
690         unsigned long addr;
691         int error = 0;
692         int i;
693
694         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
695                 if (kgdb_break[i].state != BP_ACTIVE)
696                         continue;
697                 addr = kgdb_break[i].bpt_addr;
698                 error = kgdb_arch_remove_breakpoint(addr,
699                                         kgdb_break[i].saved_instr);
700                 if (error)
701                         return error;
702
703                 kgdb_flush_swbreak_addr(addr);
704                 kgdb_break[i].state = BP_SET;
705         }
706         return 0;
707 }
708
709 static int kgdb_remove_sw_break(unsigned long addr)
710 {
711         int i;
712
713         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
714                 if ((kgdb_break[i].state == BP_SET) &&
715                                 (kgdb_break[i].bpt_addr == addr)) {
716                         kgdb_break[i].state = BP_REMOVED;
717                         return 0;
718                 }
719         }
720         return -ENOENT;
721 }
722
723 int kgdb_isremovedbreak(unsigned long addr)
724 {
725         int i;
726
727         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
728                 if ((kgdb_break[i].state == BP_REMOVED) &&
729                                         (kgdb_break[i].bpt_addr == addr))
730                         return 1;
731         }
732         return 0;
733 }
734
735 static int remove_all_break(void)
736 {
737         unsigned long addr;
738         int error;
739         int i;
740
741         /* Clear memory breakpoints. */
742         for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
743                 if (kgdb_break[i].state != BP_ACTIVE)
744                         goto setundefined;
745                 addr = kgdb_break[i].bpt_addr;
746                 error = kgdb_arch_remove_breakpoint(addr,
747                                 kgdb_break[i].saved_instr);
748                 if (error)
749                         printk(KERN_ERR "KGDB: breakpoint remove failed: %lx\n",
750                            addr);
751 setundefined:
752                 kgdb_break[i].state = BP_UNDEFINED;
753         }
754
755         /* Clear hardware breakpoints. */
756         if (arch_kgdb_ops.remove_all_hw_break)
757                 arch_kgdb_ops.remove_all_hw_break();
758
759         return 0;
760 }
761
762 /*
763  * Remap normal tasks to their real PID,
764  * CPU shadow threads are mapped to -CPU - 2
765  */
766 static inline int shadow_pid(int realpid)
767 {
768         if (realpid)
769                 return realpid;
770
771         return -raw_smp_processor_id() - 2;
772 }
773
774 static char gdbmsgbuf[BUFMAX + 1];
775
776 static void kgdb_msg_write(const char *s, int len)
777 {
778         char *bufptr;
779         int wcount;
780         int i;
781
782         /* 'O'utput */
783         gdbmsgbuf[0] = 'O';
784
785         /* Fill and send buffers... */
786         while (len > 0) {
787                 bufptr = gdbmsgbuf + 1;
788
789                 /* Calculate how many this time */
790                 if ((len << 1) > (BUFMAX - 2))
791                         wcount = (BUFMAX - 2) >> 1;
792                 else
793                         wcount = len;
794
795                 /* Pack in hex chars */
796                 for (i = 0; i < wcount; i++)
797                         bufptr = pack_hex_byte(bufptr, s[i]);
798                 *bufptr = '\0';
799
800                 /* Move up */
801                 s += wcount;
802                 len -= wcount;
803
804                 /* Write packet */
805                 put_packet(gdbmsgbuf);
806         }
807 }
808
809 /*
810  * Return true if there is a valid kgdb I/O module.  Also if no
811  * debugger is attached a message can be printed to the console about
812  * waiting for the debugger to attach.
813  *
814  * The print_wait argument is only to be true when called from inside
815  * the core kgdb_handle_exception, because it will wait for the
816  * debugger to attach.
817  */
818 static int kgdb_io_ready(int print_wait)
819 {
820         if (!kgdb_io_ops)
821                 return 0;
822         if (kgdb_connected)
823                 return 1;
824         if (atomic_read(&kgdb_setting_breakpoint))
825                 return 1;
826         if (print_wait)
827                 printk(KERN_CRIT "KGDB: Waiting for remote debugger\n");
828         return 1;
829 }
830
831 /*
832  * All the functions that start with gdb_cmd are the various
833  * operations to implement the handlers for the gdbserial protocol
834  * where KGDB is communicating with an external debugger
835  */
836
837 /* Handle the '?' status packets */
838 static void gdb_cmd_status(struct kgdb_state *ks)
839 {
840         /*
841          * We know that this packet is only sent
842          * during initial connect.  So to be safe,
843          * we clear out our breakpoints now in case
844          * GDB is reconnecting.
845          */
846         remove_all_break();
847
848         remcom_out_buffer[0] = 'S';
849         pack_hex_byte(&remcom_out_buffer[1], ks->signo);
850 }
851
852 /* Handle the 'g' get registers request */
853 static void gdb_cmd_getregs(struct kgdb_state *ks)
854 {
855         struct task_struct *thread;
856         void *local_debuggerinfo;
857         int i;
858
859         thread = kgdb_usethread;
860         if (!thread) {
861                 thread = kgdb_info[ks->cpu].task;
862                 local_debuggerinfo = kgdb_info[ks->cpu].debuggerinfo;
863         } else {
864                 local_debuggerinfo = NULL;
865                 for_each_online_cpu(i) {
866                         /*
867                          * Try to find the task on some other
868                          * or possibly this node if we do not
869                          * find the matching task then we try
870                          * to approximate the results.
871                          */
872                         if (thread == kgdb_info[i].task)
873                                 local_debuggerinfo = kgdb_info[i].debuggerinfo;
874                 }
875         }
876
877         /*
878          * All threads that don't have debuggerinfo should be
879          * in schedule() sleeping, since all other CPUs
880          * are in kgdb_wait, and thus have debuggerinfo.
881          */
882         if (local_debuggerinfo) {
883                 pt_regs_to_gdb_regs(gdb_regs, local_debuggerinfo);
884         } else {
885                 /*
886                  * Pull stuff saved during switch_to; nothing
887                  * else is accessible (or even particularly
888                  * relevant).
889                  *
890                  * This should be enough for a stack trace.
891                  */
892                 sleeping_thread_to_gdb_regs(gdb_regs, thread);
893         }
894         kgdb_mem2hex((char *)gdb_regs, remcom_out_buffer, NUMREGBYTES);
895 }
896
897 /* Handle the 'G' set registers request */
898 static void gdb_cmd_setregs(struct kgdb_state *ks)
899 {
900         kgdb_hex2mem(&remcom_in_buffer[1], (char *)gdb_regs, NUMREGBYTES);
901
902         if (kgdb_usethread && kgdb_usethread != current) {
903                 error_packet(remcom_out_buffer, -EINVAL);
904         } else {
905                 gdb_regs_to_pt_regs(gdb_regs, ks->linux_regs);
906                 strcpy(remcom_out_buffer, "OK");
907         }
908 }
909
910 /* Handle the 'm' memory read bytes */
911 static void gdb_cmd_memread(struct kgdb_state *ks)
912 {
913         char *ptr = &remcom_in_buffer[1];
914         unsigned long length;
915         unsigned long addr;
916         int err;
917
918         if (kgdb_hex2long(&ptr, &addr) > 0 && *ptr++ == ',' &&
919                                         kgdb_hex2long(&ptr, &length) > 0) {
920                 err = kgdb_mem2hex((char *)addr, remcom_out_buffer, length);
921                 if (err)
922                         error_packet(remcom_out_buffer, err);
923         } else {
924                 error_packet(remcom_out_buffer, -EINVAL);
925         }
926 }
927
928 /* Handle the 'M' memory write bytes */
929 static void gdb_cmd_memwrite(struct kgdb_state *ks)
930 {
931         int err = write_mem_msg(0);
932
933         if (err)
934                 error_packet(remcom_out_buffer, err);
935         else
936                 strcpy(remcom_out_buffer, "OK");
937 }
938
939 /* Handle the 'X' memory binary write bytes */
940 static void gdb_cmd_binwrite(struct kgdb_state *ks)
941 {
942         int err = write_mem_msg(1);
943
944         if (err)
945                 error_packet(remcom_out_buffer, err);
946         else
947                 strcpy(remcom_out_buffer, "OK");
948 }
949
950 /* Handle the 'D' or 'k', detach or kill packets */
951 static void gdb_cmd_detachkill(struct kgdb_state *ks)
952 {
953         int error;
954
955         /* The detach case */
956         if (remcom_in_buffer[0] == 'D') {
957                 error = remove_all_break();
958                 if (error < 0) {
959                         error_packet(remcom_out_buffer, error);
960                 } else {
961                         strcpy(remcom_out_buffer, "OK");
962                         kgdb_connected = 0;
963                 }
964                 put_packet(remcom_out_buffer);
965         } else {
966                 /*
967                  * Assume the kill case, with no exit code checking,
968                  * trying to force detach the debugger:
969                  */
970                 remove_all_break();
971                 kgdb_connected = 0;
972         }
973 }
974
975 /* Handle the 'R' reboot packets */
976 static int gdb_cmd_reboot(struct kgdb_state *ks)
977 {
978         /* For now, only honor R0 */
979         if (strcmp(remcom_in_buffer, "R0") == 0) {
980                 printk(KERN_CRIT "Executing emergency reboot\n");
981                 strcpy(remcom_out_buffer, "OK");
982                 put_packet(remcom_out_buffer);
983
984                 /*
985                  * Execution should not return from
986                  * machine_emergency_restart()
987                  */
988                 machine_emergency_restart();
989                 kgdb_connected = 0;
990
991                 return 1;
992         }
993         return 0;
994 }
995
996 /* Handle the 'q' query packets */
997 static void gdb_cmd_query(struct kgdb_state *ks)
998 {
999         struct task_struct *g;
1000         struct task_struct *p;
1001         unsigned char thref[8];
1002         char *ptr;
1003         int i;
1004         int cpu;
1005         int finished = 0;
1006
1007         switch (remcom_in_buffer[1]) {
1008         case 's':
1009         case 'f':
1010                 if (memcmp(remcom_in_buffer + 2, "ThreadInfo", 10)) {
1011                         error_packet(remcom_out_buffer, -EINVAL);
1012                         break;
1013                 }
1014
1015                 i = 0;
1016                 remcom_out_buffer[0] = 'm';
1017                 ptr = remcom_out_buffer + 1;
1018                 if (remcom_in_buffer[1] == 'f') {
1019                         /* Each cpu is a shadow thread */
1020                         for_each_online_cpu(cpu) {
1021                                 ks->thr_query = 0;
1022                                 int_to_threadref(thref, -cpu - 2);
1023                                 pack_threadid(ptr, thref);
1024                                 ptr += BUF_THREAD_ID_SIZE;
1025                                 *(ptr++) = ',';
1026                                 i++;
1027                         }
1028                 }
1029
1030                 do_each_thread(g, p) {
1031                         if (i >= ks->thr_query && !finished) {
1032                                 int_to_threadref(thref, p->pid);
1033                                 pack_threadid(ptr, thref);
1034                                 ptr += BUF_THREAD_ID_SIZE;
1035                                 *(ptr++) = ',';
1036                                 ks->thr_query++;
1037                                 if (ks->thr_query % KGDB_MAX_THREAD_QUERY == 0)
1038                                         finished = 1;
1039                         }
1040                         i++;
1041                 } while_each_thread(g, p);
1042
1043                 *(--ptr) = '\0';
1044                 break;
1045
1046         case 'C':
1047                 /* Current thread id */
1048                 strcpy(remcom_out_buffer, "QC");
1049                 ks->threadid = shadow_pid(current->pid);
1050                 int_to_threadref(thref, ks->threadid);
1051                 pack_threadid(remcom_out_buffer + 2, thref);
1052                 break;
1053         case 'T':
1054                 if (memcmp(remcom_in_buffer + 1, "ThreadExtraInfo,", 16)) {
1055                         error_packet(remcom_out_buffer, -EINVAL);
1056                         break;
1057                 }
1058                 ks->threadid = 0;
1059                 ptr = remcom_in_buffer + 17;
1060                 kgdb_hex2long(&ptr, &ks->threadid);
1061                 if (!getthread(ks->linux_regs, ks->threadid)) {
1062                         error_packet(remcom_out_buffer, -EINVAL);
1063                         break;
1064                 }
1065                 if ((int)ks->threadid > 0) {
1066                         kgdb_mem2hex(getthread(ks->linux_regs,
1067                                         ks->threadid)->comm,
1068                                         remcom_out_buffer, 16);
1069                 } else {
1070                         static char tmpstr[23 + BUF_THREAD_ID_SIZE];
1071
1072                         sprintf(tmpstr, "shadowCPU%d",
1073                                         (int)(-ks->threadid - 2));
1074                         kgdb_mem2hex(tmpstr, remcom_out_buffer, strlen(tmpstr));
1075                 }
1076                 break;
1077         }
1078 }
1079
1080 /* Handle the 'H' task query packets */
1081 static void gdb_cmd_task(struct kgdb_state *ks)
1082 {
1083         struct task_struct *thread;
1084         char *ptr;
1085
1086         switch (remcom_in_buffer[1]) {
1087         case 'g':
1088                 ptr = &remcom_in_buffer[2];
1089                 kgdb_hex2long(&ptr, &ks->threadid);
1090                 thread = getthread(ks->linux_regs, ks->threadid);
1091                 if (!thread && ks->threadid > 0) {
1092                         error_packet(remcom_out_buffer, -EINVAL);
1093                         break;
1094                 }
1095                 kgdb_usethread = thread;
1096                 ks->kgdb_usethreadid = ks->threadid;
1097                 strcpy(remcom_out_buffer, "OK");
1098                 break;
1099         case 'c':
1100                 ptr = &remcom_in_buffer[2];
1101                 kgdb_hex2long(&ptr, &ks->threadid);
1102                 if (!ks->threadid) {
1103                         kgdb_contthread = NULL;
1104                 } else {
1105                         thread = getthread(ks->linux_regs, ks->threadid);
1106                         if (!thread && ks->threadid > 0) {
1107                                 error_packet(remcom_out_buffer, -EINVAL);
1108                                 break;
1109                         }
1110                         kgdb_contthread = thread;
1111                 }
1112                 strcpy(remcom_out_buffer, "OK");
1113                 break;
1114         }
1115 }
1116
1117 /* Handle the 'T' thread query packets */
1118 static void gdb_cmd_thread(struct kgdb_state *ks)
1119 {
1120         char *ptr = &remcom_in_buffer[1];
1121         struct task_struct *thread;
1122
1123         kgdb_hex2long(&ptr, &ks->threadid);
1124         thread = getthread(ks->linux_regs, ks->threadid);
1125         if (thread)
1126                 strcpy(remcom_out_buffer, "OK");
1127         else
1128                 error_packet(remcom_out_buffer, -EINVAL);
1129 }
1130
1131 /* Handle the 'z' or 'Z' breakpoint remove or set packets */
1132 static void gdb_cmd_break(struct kgdb_state *ks)
1133 {
1134         /*
1135          * Since GDB-5.3, it's been drafted that '0' is a software
1136          * breakpoint, '1' is a hardware breakpoint, so let's do that.
1137          */
1138         char *bpt_type = &remcom_in_buffer[1];
1139         char *ptr = &remcom_in_buffer[2];
1140         unsigned long addr;
1141         unsigned long length;
1142         int error = 0;
1143
1144         if (arch_kgdb_ops.set_hw_breakpoint && *bpt_type >= '1') {
1145                 /* Unsupported */
1146                 if (*bpt_type > '4')
1147                         return;
1148         } else {
1149                 if (*bpt_type != '0' && *bpt_type != '1')
1150                         /* Unsupported. */
1151                         return;
1152         }
1153
1154         /*
1155          * Test if this is a hardware breakpoint, and
1156          * if we support it:
1157          */
1158         if (*bpt_type == '1' && !(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT))
1159                 /* Unsupported. */
1160                 return;
1161
1162         if (*(ptr++) != ',') {
1163                 error_packet(remcom_out_buffer, -EINVAL);
1164                 return;
1165         }
1166         if (!kgdb_hex2long(&ptr, &addr)) {
1167                 error_packet(remcom_out_buffer, -EINVAL);
1168                 return;
1169         }
1170         if (*(ptr++) != ',' ||
1171                 !kgdb_hex2long(&ptr, &length)) {
1172                 error_packet(remcom_out_buffer, -EINVAL);
1173                 return;
1174         }
1175
1176         if (remcom_in_buffer[0] == 'Z' && *bpt_type == '0')
1177                 error = kgdb_set_sw_break(addr);
1178         else if (remcom_in_buffer[0] == 'z' && *bpt_type == '0')
1179                 error = kgdb_remove_sw_break(addr);
1180         else if (remcom_in_buffer[0] == 'Z')
1181                 error = arch_kgdb_ops.set_hw_breakpoint(addr,
1182                         (int)length, *bpt_type - '0');
1183         else if (remcom_in_buffer[0] == 'z')
1184                 error = arch_kgdb_ops.remove_hw_breakpoint(addr,
1185                         (int) length, *bpt_type - '0');
1186
1187         if (error == 0)
1188                 strcpy(remcom_out_buffer, "OK");
1189         else
1190                 error_packet(remcom_out_buffer, error);
1191 }
1192
1193 /* Handle the 'C' signal / exception passing packets */
1194 static int gdb_cmd_exception_pass(struct kgdb_state *ks)
1195 {
1196         /* C09 == pass exception
1197          * C15 == detach kgdb, pass exception
1198          */
1199         if (remcom_in_buffer[1] == '0' && remcom_in_buffer[2] == '9') {
1200
1201                 ks->pass_exception = 1;
1202                 remcom_in_buffer[0] = 'c';
1203
1204         } else if (remcom_in_buffer[1] == '1' && remcom_in_buffer[2] == '5') {
1205
1206                 ks->pass_exception = 1;
1207                 remcom_in_buffer[0] = 'D';
1208                 remove_all_break();
1209                 kgdb_connected = 0;
1210                 return 1;
1211
1212         } else {
1213                 error_packet(remcom_out_buffer, -EINVAL);
1214                 return 0;
1215         }
1216
1217         /* Indicate fall through */
1218         return -1;
1219 }
1220
1221 /*
1222  * This function performs all gdbserial command procesing
1223  */
1224 static int gdb_serial_stub(struct kgdb_state *ks)
1225 {
1226         int error = 0;
1227         int tmp;
1228
1229         /* Clear the out buffer. */
1230         memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1231
1232         if (kgdb_connected) {
1233                 unsigned char thref[8];
1234                 char *ptr;
1235
1236                 /* Reply to host that an exception has occurred */
1237                 ptr = remcom_out_buffer;
1238                 *ptr++ = 'T';
1239                 ptr = pack_hex_byte(ptr, ks->signo);
1240                 ptr += strlen(strcpy(ptr, "thread:"));
1241                 int_to_threadref(thref, shadow_pid(current->pid));
1242                 ptr = pack_threadid(ptr, thref);
1243                 *ptr++ = ';';
1244                 put_packet(remcom_out_buffer);
1245         }
1246
1247         kgdb_usethread = kgdb_info[ks->cpu].task;
1248         ks->kgdb_usethreadid = shadow_pid(kgdb_info[ks->cpu].task->pid);
1249         ks->pass_exception = 0;
1250
1251         while (1) {
1252                 error = 0;
1253
1254                 /* Clear the out buffer. */
1255                 memset(remcom_out_buffer, 0, sizeof(remcom_out_buffer));
1256
1257                 get_packet(remcom_in_buffer);
1258
1259                 switch (remcom_in_buffer[0]) {
1260                 case '?': /* gdbserial status */
1261                         gdb_cmd_status(ks);
1262                         break;
1263                 case 'g': /* return the value of the CPU registers */
1264                         gdb_cmd_getregs(ks);
1265                         break;
1266                 case 'G': /* set the value of the CPU registers - return OK */
1267                         gdb_cmd_setregs(ks);
1268                         break;
1269                 case 'm': /* mAA..AA,LLLL  Read LLLL bytes at address AA..AA */
1270                         gdb_cmd_memread(ks);
1271                         break;
1272                 case 'M': /* MAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1273                         gdb_cmd_memwrite(ks);
1274                         break;
1275                 case 'X': /* XAA..AA,LLLL: Write LLLL bytes at address AA..AA */
1276                         gdb_cmd_binwrite(ks);
1277                         break;
1278                         /* kill or detach. KGDB should treat this like a
1279                          * continue.
1280                          */
1281                 case 'D': /* Debugger detach */
1282                 case 'k': /* Debugger detach via kill */
1283                         gdb_cmd_detachkill(ks);
1284                         goto default_handle;
1285                 case 'R': /* Reboot */
1286                         if (gdb_cmd_reboot(ks))
1287                                 goto default_handle;
1288                         break;
1289                 case 'q': /* query command */
1290                         gdb_cmd_query(ks);
1291                         break;
1292                 case 'H': /* task related */
1293                         gdb_cmd_task(ks);
1294                         break;
1295                 case 'T': /* Query thread status */
1296                         gdb_cmd_thread(ks);
1297                         break;
1298                 case 'z': /* Break point remove */
1299                 case 'Z': /* Break point set */
1300                         gdb_cmd_break(ks);
1301                         break;
1302                 case 'C': /* Exception passing */
1303                         tmp = gdb_cmd_exception_pass(ks);
1304                         if (tmp > 0)
1305                                 goto default_handle;
1306                         if (tmp == 0)
1307                                 break;
1308                         /* Fall through on tmp < 0 */
1309                 case 'c': /* Continue packet */
1310                 case 's': /* Single step packet */
1311                         if (kgdb_contthread && kgdb_contthread != current) {
1312                                 /* Can't switch threads in kgdb */
1313                                 error_packet(remcom_out_buffer, -EINVAL);
1314                                 break;
1315                         }
1316                         kgdb_activate_sw_breakpoints();
1317                         /* Fall through to default processing */
1318                 default:
1319 default_handle:
1320                         error = kgdb_arch_handle_exception(ks->ex_vector,
1321                                                 ks->signo,
1322                                                 ks->err_code,
1323                                                 remcom_in_buffer,
1324                                                 remcom_out_buffer,
1325                                                 ks->linux_regs);
1326                         /*
1327                          * Leave cmd processing on error, detach,
1328                          * kill, continue, or single step.
1329                          */
1330                         if (error >= 0 || remcom_in_buffer[0] == 'D' ||
1331                             remcom_in_buffer[0] == 'k') {
1332                                 error = 0;
1333                                 goto kgdb_exit;
1334                         }
1335
1336                 }
1337
1338                 /* reply to the request */
1339                 put_packet(remcom_out_buffer);
1340         }
1341
1342 kgdb_exit:
1343         if (ks->pass_exception)
1344                 error = 1;
1345         return error;
1346 }
1347
1348 static int kgdb_reenter_check(struct kgdb_state *ks)
1349 {
1350         unsigned long addr;
1351
1352         if (atomic_read(&kgdb_active) != raw_smp_processor_id())
1353                 return 0;
1354
1355         /* Panic on recursive debugger calls: */
1356         exception_level++;
1357         addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs);
1358         kgdb_deactivate_sw_breakpoints();
1359
1360         /*
1361          * If the break point removed ok at the place exception
1362          * occurred, try to recover and print a warning to the end
1363          * user because the user planted a breakpoint in a place that
1364          * KGDB needs in order to function.
1365          */
1366         if (kgdb_remove_sw_break(addr) == 0) {
1367                 exception_level = 0;
1368                 kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1369                 kgdb_activate_sw_breakpoints();
1370                 printk(KERN_CRIT "KGDB: re-enter error: breakpoint removed %lx\n",
1371                         addr);
1372                 WARN_ON_ONCE(1);
1373
1374                 return 1;
1375         }
1376         remove_all_break();
1377         kgdb_skipexception(ks->ex_vector, ks->linux_regs);
1378
1379         if (exception_level > 1) {
1380                 dump_stack();
1381                 panic("Recursive entry to debugger");
1382         }
1383
1384         printk(KERN_CRIT "KGDB: re-enter exception: ALL breakpoints killed\n");
1385         dump_stack();
1386         panic("Recursive entry to debugger");
1387
1388         return 1;
1389 }
1390
1391 /*
1392  * kgdb_handle_exception() - main entry point from a kernel exception
1393  *
1394  * Locking hierarchy:
1395  *      interface locks, if any (begin_session)
1396  *      kgdb lock (kgdb_active)
1397  */
1398 int
1399 kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
1400 {
1401         struct kgdb_state kgdb_var;
1402         struct kgdb_state *ks = &kgdb_var;
1403         unsigned long flags;
1404         int sstep_tries = 100;
1405         int error = 0;
1406         int i, cpu;
1407
1408         ks->cpu                 = raw_smp_processor_id();
1409         ks->ex_vector           = evector;
1410         ks->signo               = signo;
1411         ks->ex_vector           = evector;
1412         ks->err_code            = ecode;
1413         ks->kgdb_usethreadid    = 0;
1414         ks->linux_regs          = regs;
1415
1416         if (kgdb_reenter_check(ks))
1417                 return 0; /* Ouch, double exception ! */
1418
1419 acquirelock:
1420         /*
1421          * Interrupts will be restored by the 'trap return' code, except when
1422          * single stepping.
1423          */
1424         local_irq_save(flags);
1425
1426         cpu = raw_smp_processor_id();
1427
1428         /*
1429          * Acquire the kgdb_active lock:
1430          */
1431         while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
1432                 cpu_relax();
1433
1434         /*
1435          * For single stepping, try to only enter on the processor
1436          * that was single stepping.  To gaurd against a deadlock, the
1437          * kernel will only try for the value of sstep_tries before
1438          * giving up and continuing on.
1439          */
1440         if (atomic_read(&kgdb_cpu_doing_single_step) != -1 &&
1441             (kgdb_info[cpu].task &&
1442              kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) {
1443                 atomic_set(&kgdb_active, -1);
1444                 touch_softlockup_watchdog();
1445                 clocksource_touch_watchdog();
1446                 local_irq_restore(flags);
1447
1448                 goto acquirelock;
1449         }
1450
1451         if (!kgdb_io_ready(1)) {
1452                 error = 1;
1453                 goto kgdb_restore; /* No I/O connection, so resume the system */
1454         }
1455
1456         /*
1457          * Don't enter if we have hit a removed breakpoint.
1458          */
1459         if (kgdb_skipexception(ks->ex_vector, ks->linux_regs))
1460                 goto kgdb_restore;
1461
1462         /* Call the I/O driver's pre_exception routine */
1463         if (kgdb_io_ops->pre_exception)
1464                 kgdb_io_ops->pre_exception();
1465
1466         kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
1467         kgdb_info[ks->cpu].task = current;
1468
1469         kgdb_disable_hw_debug(ks->linux_regs);
1470
1471         /*
1472          * Get the passive CPU lock which will hold all the non-primary
1473          * CPU in a spin state while the debugger is active
1474          */
1475         if (!kgdb_single_step) {
1476                 for (i = 0; i < NR_CPUS; i++)
1477                         atomic_set(&passive_cpu_wait[i], 1);
1478         }
1479
1480         /*
1481          * spin_lock code is good enough as a barrier so we don't
1482          * need one here:
1483          */
1484         atomic_set(&cpu_in_kgdb[ks->cpu], 1);
1485
1486 #ifdef CONFIG_SMP
1487         /* Signal the other CPUs to enter kgdb_wait() */
1488         if ((!kgdb_single_step) && kgdb_do_roundup)
1489                 kgdb_roundup_cpus(flags);
1490 #endif
1491
1492         /*
1493          * Wait for the other CPUs to be notified and be waiting for us:
1494          */
1495         for_each_online_cpu(i) {
1496                 while (!atomic_read(&cpu_in_kgdb[i]))
1497                         cpu_relax();
1498         }
1499
1500         /*
1501          * At this point the primary processor is completely
1502          * in the debugger and all secondary CPUs are quiescent
1503          */
1504         kgdb_post_primary_code(ks->linux_regs, ks->ex_vector, ks->err_code);
1505         kgdb_deactivate_sw_breakpoints();
1506         kgdb_single_step = 0;
1507         kgdb_contthread = current;
1508         exception_level = 0;
1509
1510         /* Talk to debugger with gdbserial protocol */
1511         error = gdb_serial_stub(ks);
1512
1513         /* Call the I/O driver's post_exception routine */
1514         if (kgdb_io_ops->post_exception)
1515                 kgdb_io_ops->post_exception();
1516
1517         kgdb_info[ks->cpu].debuggerinfo = NULL;
1518         kgdb_info[ks->cpu].task = NULL;
1519         atomic_set(&cpu_in_kgdb[ks->cpu], 0);
1520
1521         if (!kgdb_single_step) {
1522                 for (i = NR_CPUS-1; i >= 0; i--)
1523                         atomic_set(&passive_cpu_wait[i], 0);
1524                 /*
1525                  * Wait till all the CPUs have quit
1526                  * from the debugger.
1527                  */
1528                 for_each_online_cpu(i) {
1529                         while (atomic_read(&cpu_in_kgdb[i]))
1530                                 cpu_relax();
1531                 }
1532         }
1533
1534 kgdb_restore:
1535         if (atomic_read(&kgdb_cpu_doing_single_step) != -1) {
1536                 int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step);
1537                 if (kgdb_info[sstep_cpu].task)
1538                         kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid;
1539                 else
1540                         kgdb_sstep_pid = 0;
1541         }
1542         /* Free kgdb_active */
1543         atomic_set(&kgdb_active, -1);
1544         touch_softlockup_watchdog();
1545         clocksource_touch_watchdog();
1546         local_irq_restore(flags);
1547
1548         return error;
1549 }
1550
1551 int kgdb_nmicallback(int cpu, void *regs)
1552 {
1553 #ifdef CONFIG_SMP
1554         if (!atomic_read(&cpu_in_kgdb[cpu]) &&
1555                         atomic_read(&kgdb_active) != cpu &&
1556                         atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
1557                 kgdb_wait((struct pt_regs *)regs);
1558                 return 0;
1559         }
1560 #endif
1561         return 1;
1562 }
1563
1564 static void kgdb_console_write(struct console *co, const char *s,
1565    unsigned count)
1566 {
1567         unsigned long flags;
1568
1569         /* If we're debugging, or KGDB has not connected, don't try
1570          * and print. */
1571         if (!kgdb_connected || atomic_read(&kgdb_active) != -1)
1572                 return;
1573
1574         local_irq_save(flags);
1575         kgdb_msg_write(s, count);
1576         local_irq_restore(flags);
1577 }
1578
1579 static struct console kgdbcons = {
1580         .name           = "kgdb",
1581         .write          = kgdb_console_write,
1582         .flags          = CON_PRINTBUFFER | CON_ENABLED,
1583         .index          = -1,
1584 };
1585
1586 #ifdef CONFIG_MAGIC_SYSRQ
1587 static void sysrq_handle_gdb(int key, struct tty_struct *tty)
1588 {
1589         if (!kgdb_io_ops) {
1590                 printk(KERN_CRIT "ERROR: No KGDB I/O module available\n");
1591                 return;
1592         }
1593         if (!kgdb_connected)
1594                 printk(KERN_CRIT "Entering KGDB\n");
1595
1596         kgdb_breakpoint();
1597 }
1598
1599 static struct sysrq_key_op sysrq_gdb_op = {
1600         .handler        = sysrq_handle_gdb,
1601         .help_msg       = "debug(G)",
1602         .action_msg     = "DEBUG",
1603 };
1604 #endif
1605
1606 static void kgdb_register_callbacks(void)
1607 {
1608         if (!kgdb_io_module_registered) {
1609                 kgdb_io_module_registered = 1;
1610                 kgdb_arch_init();
1611 #ifdef CONFIG_MAGIC_SYSRQ
1612                 register_sysrq_key('g', &sysrq_gdb_op);
1613 #endif
1614                 if (kgdb_use_con && !kgdb_con_registered) {
1615                         register_console(&kgdbcons);
1616                         kgdb_con_registered = 1;
1617                 }
1618         }
1619 }
1620
1621 static void kgdb_unregister_callbacks(void)
1622 {
1623         /*
1624          * When this routine is called KGDB should unregister from the
1625          * panic handler and clean up, making sure it is not handling any
1626          * break exceptions at the time.
1627          */
1628         if (kgdb_io_module_registered) {
1629                 kgdb_io_module_registered = 0;
1630                 kgdb_arch_exit();
1631 #ifdef CONFIG_MAGIC_SYSRQ
1632                 unregister_sysrq_key('g', &sysrq_gdb_op);
1633 #endif
1634                 if (kgdb_con_registered) {
1635                         unregister_console(&kgdbcons);
1636                         kgdb_con_registered = 0;
1637                 }
1638         }
1639 }
1640
1641 static void kgdb_initial_breakpoint(void)
1642 {
1643         kgdb_break_asap = 0;
1644
1645         printk(KERN_CRIT "kgdb: Waiting for connection from remote gdb...\n");
1646         kgdb_breakpoint();
1647 }
1648
1649 /**
1650  *      kgdb_register_io_module - register KGDB IO module
1651  *      @new_kgdb_io_ops: the io ops vector
1652  *
1653  *      Register it with the KGDB core.
1654  */
1655 int kgdb_register_io_module(struct kgdb_io *new_kgdb_io_ops)
1656 {
1657         int err;
1658
1659         spin_lock(&kgdb_registration_lock);
1660
1661         if (kgdb_io_ops) {
1662                 spin_unlock(&kgdb_registration_lock);
1663
1664                 printk(KERN_ERR "kgdb: Another I/O driver is already "
1665                                 "registered with KGDB.\n");
1666                 return -EBUSY;
1667         }
1668
1669         if (new_kgdb_io_ops->init) {
1670                 err = new_kgdb_io_ops->init();
1671                 if (err) {
1672                         spin_unlock(&kgdb_registration_lock);
1673                         return err;
1674                 }
1675         }
1676
1677         kgdb_io_ops = new_kgdb_io_ops;
1678
1679         spin_unlock(&kgdb_registration_lock);
1680
1681         printk(KERN_INFO "kgdb: Registered I/O driver %s.\n",
1682                new_kgdb_io_ops->name);
1683
1684         /* Arm KGDB now. */
1685         kgdb_register_callbacks();
1686
1687         if (kgdb_break_asap)
1688                 kgdb_initial_breakpoint();
1689
1690         return 0;
1691 }
1692 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
1693
1694 /**
1695  *      kkgdb_unregister_io_module - unregister KGDB IO module
1696  *      @old_kgdb_io_ops: the io ops vector
1697  *
1698  *      Unregister it with the KGDB core.
1699  */
1700 void kgdb_unregister_io_module(struct kgdb_io *old_kgdb_io_ops)
1701 {
1702         BUG_ON(kgdb_connected);
1703
1704         /*
1705          * KGDB is no longer able to communicate out, so
1706          * unregister our callbacks and reset state.
1707          */
1708         kgdb_unregister_callbacks();
1709
1710         spin_lock(&kgdb_registration_lock);
1711
1712         WARN_ON_ONCE(kgdb_io_ops != old_kgdb_io_ops);
1713         kgdb_io_ops = NULL;
1714
1715         spin_unlock(&kgdb_registration_lock);
1716
1717         printk(KERN_INFO
1718                 "kgdb: Unregistered I/O driver %s, debugger disabled.\n",
1719                 old_kgdb_io_ops->name);
1720 }
1721 EXPORT_SYMBOL_GPL(kgdb_unregister_io_module);
1722
1723 /**
1724  * kgdb_breakpoint - generate breakpoint exception
1725  *
1726  * This function will generate a breakpoint exception.  It is used at the
1727  * beginning of a program to sync up with a debugger and can be used
1728  * otherwise as a quick means to stop program execution and "break" into
1729  * the debugger.
1730  */
1731 void kgdb_breakpoint(void)
1732 {
1733         atomic_set(&kgdb_setting_breakpoint, 1);
1734         wmb(); /* Sync point before breakpoint */
1735         arch_kgdb_breakpoint();
1736         wmb(); /* Sync point after breakpoint */
1737         atomic_set(&kgdb_setting_breakpoint, 0);
1738 }
1739 EXPORT_SYMBOL_GPL(kgdb_breakpoint);
1740
1741 static int __init opt_kgdb_wait(char *str)
1742 {
1743         kgdb_break_asap = 1;
1744
1745         if (kgdb_io_module_registered)
1746                 kgdb_initial_breakpoint();
1747
1748         return 0;
1749 }
1750
1751 early_param("kgdbwait", opt_kgdb_wait);