xref: /openbmc/linux/arch/x86/kernel/kgdb.c (revision 9ac8d3fb)
1 /*
2  * This program is free software; you can redistribute it and/or modify it
3  * under the terms of the GNU General Public License as published by the
4  * Free Software Foundation; either version 2, or (at your option) any
5  * later version.
6  *
7  * This program is distributed in the hope that it will be useful, but
8  * WITHOUT ANY WARRANTY; without even the implied warranty of
9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
10  * General Public License for more details.
11  *
12  */
13 
14 /*
15  * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
16  * Copyright (C) 2000-2001 VERITAS Software Corporation.
17  * Copyright (C) 2002 Andi Kleen, SuSE Labs
18  * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
19  * Copyright (C) 2007 MontaVista Software, Inc.
20  * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
21  */
22 /****************************************************************************
23  *  Contributor:     Lake Stevens Instrument Division$
24  *  Written by:      Glenn Engel $
25  *  Updated by:	     Amit Kale<akale@veritas.com>
26  *  Updated by:	     Tom Rini <trini@kernel.crashing.org>
27  *  Updated by:	     Jason Wessel <jason.wessel@windriver.com>
28  *  Modified for 386 by Jim Kingdon, Cygnus Support.
29  *  Origianl kgdb, compatibility with 2.1.xx kernel by
30  *  David Grothe <dave@gcom.com>
31  *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
32  *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
33  */
34 #include <linux/spinlock.h>
35 #include <linux/kdebug.h>
36 #include <linux/string.h>
37 #include <linux/kernel.h>
38 #include <linux/ptrace.h>
39 #include <linux/sched.h>
40 #include <linux/delay.h>
41 #include <linux/kgdb.h>
42 #include <linux/init.h>
43 #include <linux/smp.h>
44 #include <linux/nmi.h>
45 
46 #include <asm/apicdef.h>
47 #include <asm/system.h>
48 
49 #include <mach_ipi.h>
50 
51 /*
52  * Put the error code here just in case the user cares:
53  */
54 static int gdb_x86errcode;
55 
56 /*
57  * Likewise, the vector number here (since GDB only gets the signal
58  * number through the usual means, and that's not very specific):
59  */
60 static int gdb_x86vector = -1;
61 
62 /**
63  *	pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
64  *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
65  *	@regs: The &struct pt_regs of the current process.
66  *
67  *	Convert the pt_regs in @regs into the format for registers that
68  *	GDB expects, stored in @gdb_regs.
69  */
70 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
71 {
72 #ifndef CONFIG_X86_32
73 	u32 *gdb_regs32 = (u32 *)gdb_regs;
74 #endif
75 	gdb_regs[GDB_AX]	= regs->ax;
76 	gdb_regs[GDB_BX]	= regs->bx;
77 	gdb_regs[GDB_CX]	= regs->cx;
78 	gdb_regs[GDB_DX]	= regs->dx;
79 	gdb_regs[GDB_SI]	= regs->si;
80 	gdb_regs[GDB_DI]	= regs->di;
81 	gdb_regs[GDB_BP]	= regs->bp;
82 	gdb_regs[GDB_PC]	= regs->ip;
83 #ifdef CONFIG_X86_32
84 	gdb_regs[GDB_PS]	= regs->flags;
85 	gdb_regs[GDB_DS]	= regs->ds;
86 	gdb_regs[GDB_ES]	= regs->es;
87 	gdb_regs[GDB_CS]	= regs->cs;
88 	gdb_regs[GDB_SS]	= __KERNEL_DS;
89 	gdb_regs[GDB_FS]	= 0xFFFF;
90 	gdb_regs[GDB_GS]	= 0xFFFF;
91 #else
92 	gdb_regs[GDB_R8]	= regs->r8;
93 	gdb_regs[GDB_R9]	= regs->r9;
94 	gdb_regs[GDB_R10]	= regs->r10;
95 	gdb_regs[GDB_R11]	= regs->r11;
96 	gdb_regs[GDB_R12]	= regs->r12;
97 	gdb_regs[GDB_R13]	= regs->r13;
98 	gdb_regs[GDB_R14]	= regs->r14;
99 	gdb_regs[GDB_R15]	= regs->r15;
100 	gdb_regs32[GDB_PS]	= regs->flags;
101 	gdb_regs32[GDB_CS]	= regs->cs;
102 	gdb_regs32[GDB_SS]	= regs->ss;
103 #endif
104 	gdb_regs[GDB_SP]	= regs->sp;
105 }
106 
107 /**
108  *	sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
109  *	@gdb_regs: A pointer to hold the registers in the order GDB wants.
110  *	@p: The &struct task_struct of the desired process.
111  *
112  *	Convert the register values of the sleeping process in @p to
113  *	the format that GDB expects.
114  *	This function is called when kgdb does not have access to the
115  *	&struct pt_regs and therefore it should fill the gdb registers
116  *	@gdb_regs with what has	been saved in &struct thread_struct
117  *	thread field during switch_to.
118  */
119 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
120 {
121 #ifndef CONFIG_X86_32
122 	u32 *gdb_regs32 = (u32 *)gdb_regs;
123 #endif
124 	gdb_regs[GDB_AX]	= 0;
125 	gdb_regs[GDB_BX]	= 0;
126 	gdb_regs[GDB_CX]	= 0;
127 	gdb_regs[GDB_DX]	= 0;
128 	gdb_regs[GDB_SI]	= 0;
129 	gdb_regs[GDB_DI]	= 0;
130 	gdb_regs[GDB_BP]	= *(unsigned long *)p->thread.sp;
131 #ifdef CONFIG_X86_32
132 	gdb_regs[GDB_DS]	= __KERNEL_DS;
133 	gdb_regs[GDB_ES]	= __KERNEL_DS;
134 	gdb_regs[GDB_PS]	= 0;
135 	gdb_regs[GDB_CS]	= __KERNEL_CS;
136 	gdb_regs[GDB_PC]	= p->thread.ip;
137 	gdb_regs[GDB_SS]	= __KERNEL_DS;
138 	gdb_regs[GDB_FS]	= 0xFFFF;
139 	gdb_regs[GDB_GS]	= 0xFFFF;
140 #else
141 	gdb_regs32[GDB_PS]	= *(unsigned long *)(p->thread.sp + 8);
142 	gdb_regs32[GDB_CS]	= __KERNEL_CS;
143 	gdb_regs32[GDB_SS]	= __KERNEL_DS;
144 	gdb_regs[GDB_PC]	= p->thread.ip;
145 	gdb_regs[GDB_R8]	= 0;
146 	gdb_regs[GDB_R9]	= 0;
147 	gdb_regs[GDB_R10]	= 0;
148 	gdb_regs[GDB_R11]	= 0;
149 	gdb_regs[GDB_R12]	= 0;
150 	gdb_regs[GDB_R13]	= 0;
151 	gdb_regs[GDB_R14]	= 0;
152 	gdb_regs[GDB_R15]	= 0;
153 #endif
154 	gdb_regs[GDB_SP]	= p->thread.sp;
155 }
156 
157 /**
158  *	gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
159  *	@gdb_regs: A pointer to hold the registers we've received from GDB.
160  *	@regs: A pointer to a &struct pt_regs to hold these values in.
161  *
162  *	Convert the GDB regs in @gdb_regs into the pt_regs, and store them
163  *	in @regs.
164  */
165 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
166 {
167 #ifndef CONFIG_X86_32
168 	u32 *gdb_regs32 = (u32 *)gdb_regs;
169 #endif
170 	regs->ax		= gdb_regs[GDB_AX];
171 	regs->bx		= gdb_regs[GDB_BX];
172 	regs->cx		= gdb_regs[GDB_CX];
173 	regs->dx		= gdb_regs[GDB_DX];
174 	regs->si		= gdb_regs[GDB_SI];
175 	regs->di		= gdb_regs[GDB_DI];
176 	regs->bp		= gdb_regs[GDB_BP];
177 	regs->ip		= gdb_regs[GDB_PC];
178 #ifdef CONFIG_X86_32
179 	regs->flags		= gdb_regs[GDB_PS];
180 	regs->ds		= gdb_regs[GDB_DS];
181 	regs->es		= gdb_regs[GDB_ES];
182 	regs->cs		= gdb_regs[GDB_CS];
183 #else
184 	regs->r8		= gdb_regs[GDB_R8];
185 	regs->r9		= gdb_regs[GDB_R9];
186 	regs->r10		= gdb_regs[GDB_R10];
187 	regs->r11		= gdb_regs[GDB_R11];
188 	regs->r12		= gdb_regs[GDB_R12];
189 	regs->r13		= gdb_regs[GDB_R13];
190 	regs->r14		= gdb_regs[GDB_R14];
191 	regs->r15		= gdb_regs[GDB_R15];
192 	regs->flags		= gdb_regs32[GDB_PS];
193 	regs->cs		= gdb_regs32[GDB_CS];
194 	regs->ss		= gdb_regs32[GDB_SS];
195 #endif
196 }
197 
198 static struct hw_breakpoint {
199 	unsigned		enabled;
200 	unsigned		type;
201 	unsigned		len;
202 	unsigned long		addr;
203 } breakinfo[4];
204 
205 static void kgdb_correct_hw_break(void)
206 {
207 	unsigned long dr7;
208 	int correctit = 0;
209 	int breakbit;
210 	int breakno;
211 
212 	get_debugreg(dr7, 7);
213 	for (breakno = 0; breakno < 4; breakno++) {
214 		breakbit = 2 << (breakno << 1);
215 		if (!(dr7 & breakbit) && breakinfo[breakno].enabled) {
216 			correctit = 1;
217 			dr7 |= breakbit;
218 			dr7 &= ~(0xf0000 << (breakno << 2));
219 			dr7 |= ((breakinfo[breakno].len << 2) |
220 				 breakinfo[breakno].type) <<
221 			       ((breakno << 2) + 16);
222 			if (breakno >= 0 && breakno <= 3)
223 				set_debugreg(breakinfo[breakno].addr, breakno);
224 
225 		} else {
226 			if ((dr7 & breakbit) && !breakinfo[breakno].enabled) {
227 				correctit = 1;
228 				dr7 &= ~breakbit;
229 				dr7 &= ~(0xf0000 << (breakno << 2));
230 			}
231 		}
232 	}
233 	if (correctit)
234 		set_debugreg(dr7, 7);
235 }
236 
237 static int
238 kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
239 {
240 	int i;
241 
242 	for (i = 0; i < 4; i++)
243 		if (breakinfo[i].addr == addr && breakinfo[i].enabled)
244 			break;
245 	if (i == 4)
246 		return -1;
247 
248 	breakinfo[i].enabled = 0;
249 
250 	return 0;
251 }
252 
253 static void kgdb_remove_all_hw_break(void)
254 {
255 	int i;
256 
257 	for (i = 0; i < 4; i++)
258 		memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint));
259 }
260 
261 static int
262 kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
263 {
264 	unsigned type;
265 	int i;
266 
267 	for (i = 0; i < 4; i++)
268 		if (!breakinfo[i].enabled)
269 			break;
270 	if (i == 4)
271 		return -1;
272 
273 	switch (bptype) {
274 	case BP_HARDWARE_BREAKPOINT:
275 		type = 0;
276 		len  = 1;
277 		break;
278 	case BP_WRITE_WATCHPOINT:
279 		type = 1;
280 		break;
281 	case BP_ACCESS_WATCHPOINT:
282 		type = 3;
283 		break;
284 	default:
285 		return -1;
286 	}
287 
288 	if (len == 1 || len == 2 || len == 4)
289 		breakinfo[i].len  = len - 1;
290 	else
291 		return -1;
292 
293 	breakinfo[i].enabled = 1;
294 	breakinfo[i].addr = addr;
295 	breakinfo[i].type = type;
296 
297 	return 0;
298 }
299 
300 /**
301  *	kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
302  *	@regs: Current &struct pt_regs.
303  *
304  *	This function will be called if the particular architecture must
305  *	disable hardware debugging while it is processing gdb packets or
306  *	handling exception.
307  */
308 void kgdb_disable_hw_debug(struct pt_regs *regs)
309 {
310 	/* Disable hardware debugging while we are in kgdb: */
311 	set_debugreg(0UL, 7);
312 }
313 
314 /**
315  *	kgdb_post_primary_code - Save error vector/code numbers.
316  *	@regs: Original pt_regs.
317  *	@e_vector: Original error vector.
318  *	@err_code: Original error code.
319  *
320  *	This is needed on architectures which support SMP and KGDB.
321  *	This function is called after all the slave cpus have been put
322  *	to a know spin state and the primary CPU has control over KGDB.
323  */
324 void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
325 {
326 	/* primary processor is completely in the debugger */
327 	gdb_x86vector = e_vector;
328 	gdb_x86errcode = err_code;
329 }
330 
331 #ifdef CONFIG_SMP
332 /**
333  *	kgdb_roundup_cpus - Get other CPUs into a holding pattern
334  *	@flags: Current IRQ state
335  *
336  *	On SMP systems, we need to get the attention of the other CPUs
337  *	and get them be in a known state.  This should do what is needed
338  *	to get the other CPUs to call kgdb_wait(). Note that on some arches,
339  *	the NMI approach is not used for rounding up all the CPUs. For example,
340  *	in case of MIPS, smp_call_function() is used to roundup CPUs. In
341  *	this case, we have to make sure that interrupts are enabled before
342  *	calling smp_call_function(). The argument to this function is
343  *	the flags that will be used when restoring the interrupts. There is
344  *	local_irq_save() call before kgdb_roundup_cpus().
345  *
346  *	On non-SMP systems, this is not called.
347  */
348 void kgdb_roundup_cpus(unsigned long flags)
349 {
350 	send_IPI_allbutself(APIC_DM_NMI);
351 }
352 #endif
353 
354 /**
355  *	kgdb_arch_handle_exception - Handle architecture specific GDB packets.
356  *	@vector: The error vector of the exception that happened.
357  *	@signo: The signal number of the exception that happened.
358  *	@err_code: The error code of the exception that happened.
359  *	@remcom_in_buffer: The buffer of the packet we have read.
360  *	@remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
361  *	@regs: The &struct pt_regs of the current process.
362  *
363  *	This function MUST handle the 'c' and 's' command packets,
364  *	as well packets to set / remove a hardware breakpoint, if used.
365  *	If there are additional packets which the hardware needs to handle,
366  *	they are handled here.  The code should return -1 if it wants to
367  *	process more packets, and a %0 or %1 if it wants to exit from the
368  *	kgdb callback.
369  */
370 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
371 			       char *remcomInBuffer, char *remcomOutBuffer,
372 			       struct pt_regs *linux_regs)
373 {
374 	unsigned long addr;
375 	unsigned long dr6;
376 	char *ptr;
377 	int newPC;
378 
379 	switch (remcomInBuffer[0]) {
380 	case 'c':
381 	case 's':
382 		/* try to read optional parameter, pc unchanged if no parm */
383 		ptr = &remcomInBuffer[1];
384 		if (kgdb_hex2long(&ptr, &addr))
385 			linux_regs->ip = addr;
386 	case 'D':
387 	case 'k':
388 		newPC = linux_regs->ip;
389 
390 		/* clear the trace bit */
391 		linux_regs->flags &= ~X86_EFLAGS_TF;
392 		atomic_set(&kgdb_cpu_doing_single_step, -1);
393 
394 		/* set the trace bit if we're stepping */
395 		if (remcomInBuffer[0] == 's') {
396 			linux_regs->flags |= X86_EFLAGS_TF;
397 			kgdb_single_step = 1;
398 			atomic_set(&kgdb_cpu_doing_single_step,
399 				   raw_smp_processor_id());
400 		}
401 
402 		get_debugreg(dr6, 6);
403 		if (!(dr6 & 0x4000)) {
404 			int breakno;
405 
406 			for (breakno = 0; breakno < 4; breakno++) {
407 				if (dr6 & (1 << breakno) &&
408 				    breakinfo[breakno].type == 0) {
409 					/* Set restore flag: */
410 					linux_regs->flags |= X86_EFLAGS_RF;
411 					break;
412 				}
413 			}
414 		}
415 		set_debugreg(0UL, 6);
416 		kgdb_correct_hw_break();
417 
418 		return 0;
419 	}
420 
421 	/* this means that we do not want to exit from the handler: */
422 	return -1;
423 }
424 
425 static inline int
426 single_step_cont(struct pt_regs *regs, struct die_args *args)
427 {
428 	/*
429 	 * Single step exception from kernel space to user space so
430 	 * eat the exception and continue the process:
431 	 */
432 	printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
433 			"resuming...\n");
434 	kgdb_arch_handle_exception(args->trapnr, args->signr,
435 				   args->err, "c", "", regs);
436 
437 	return NOTIFY_STOP;
438 }
439 
440 static int was_in_debug_nmi[NR_CPUS];
441 
442 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
443 {
444 	struct pt_regs *regs = args->regs;
445 
446 	switch (cmd) {
447 	case DIE_NMI:
448 		if (atomic_read(&kgdb_active) != -1) {
449 			/* KGDB CPU roundup */
450 			kgdb_nmicallback(raw_smp_processor_id(), regs);
451 			was_in_debug_nmi[raw_smp_processor_id()] = 1;
452 			touch_nmi_watchdog();
453 			return NOTIFY_STOP;
454 		}
455 		return NOTIFY_DONE;
456 
457 	case DIE_NMI_IPI:
458 		/* Just ignore, we will handle the roundup on DIE_NMI. */
459 		return NOTIFY_DONE;
460 
461 	case DIE_NMIUNKNOWN:
462 		if (was_in_debug_nmi[raw_smp_processor_id()]) {
463 			was_in_debug_nmi[raw_smp_processor_id()] = 0;
464 			return NOTIFY_STOP;
465 		}
466 		return NOTIFY_DONE;
467 
468 	case DIE_NMIWATCHDOG:
469 		if (atomic_read(&kgdb_active) != -1) {
470 			/* KGDB CPU roundup: */
471 			kgdb_nmicallback(raw_smp_processor_id(), regs);
472 			return NOTIFY_STOP;
473 		}
474 		/* Enter debugger: */
475 		break;
476 
477 	case DIE_DEBUG:
478 		if (atomic_read(&kgdb_cpu_doing_single_step) ==
479 		    raw_smp_processor_id()) {
480 			if (user_mode(regs))
481 				return single_step_cont(regs, args);
482 			break;
483 		} else if (test_thread_flag(TIF_SINGLESTEP))
484 			/* This means a user thread is single stepping
485 			 * a system call which should be ignored
486 			 */
487 			return NOTIFY_DONE;
488 		/* fall through */
489 	default:
490 		if (user_mode(regs))
491 			return NOTIFY_DONE;
492 	}
493 
494 	if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
495 		return NOTIFY_DONE;
496 
497 	/* Must touch watchdog before return to normal operation */
498 	touch_nmi_watchdog();
499 	return NOTIFY_STOP;
500 }
501 
502 static int
503 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
504 {
505 	unsigned long flags;
506 	int ret;
507 
508 	local_irq_save(flags);
509 	ret = __kgdb_notify(ptr, cmd);
510 	local_irq_restore(flags);
511 
512 	return ret;
513 }
514 
515 static struct notifier_block kgdb_notifier = {
516 	.notifier_call	= kgdb_notify,
517 
518 	/*
519 	 * Lowest-prio notifier priority, we want to be notified last:
520 	 */
521 	.priority	= -INT_MAX,
522 };
523 
524 /**
525  *	kgdb_arch_init - Perform any architecture specific initalization.
526  *
527  *	This function will handle the initalization of any architecture
528  *	specific callbacks.
529  */
530 int kgdb_arch_init(void)
531 {
532 	return register_die_notifier(&kgdb_notifier);
533 }
534 
535 /**
536  *	kgdb_arch_exit - Perform any architecture specific uninitalization.
537  *
538  *	This function will handle the uninitalization of any architecture
539  *	specific callbacks, for dynamic registration and unregistration.
540  */
541 void kgdb_arch_exit(void)
542 {
543 	unregister_die_notifier(&kgdb_notifier);
544 }
545 
546 /**
547  *
548  *	kgdb_skipexception - Bail out of KGDB when we've been triggered.
549  *	@exception: Exception vector number
550  *	@regs: Current &struct pt_regs.
551  *
552  *	On some architectures we need to skip a breakpoint exception when
553  *	it occurs after a breakpoint has been removed.
554  *
555  * Skip an int3 exception when it occurs after a breakpoint has been
556  * removed. Backtrack eip by 1 since the int3 would have caused it to
557  * increment by 1.
558  */
559 int kgdb_skipexception(int exception, struct pt_regs *regs)
560 {
561 	if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
562 		regs->ip -= 1;
563 		return 1;
564 	}
565 	return 0;
566 }
567 
568 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
569 {
570 	if (exception == 3)
571 		return instruction_pointer(regs) - 1;
572 	return instruction_pointer(regs);
573 }
574 
575 struct kgdb_arch arch_kgdb_ops = {
576 	/* Breakpoint instruction: */
577 	.gdb_bpt_instr		= { 0xcc },
578 	.flags			= KGDB_HW_BREAKPOINT,
579 	.set_hw_breakpoint	= kgdb_set_hw_break,
580 	.remove_hw_breakpoint	= kgdb_remove_hw_break,
581 	.remove_all_hw_break	= kgdb_remove_all_hw_break,
582 	.correct_hw_break	= kgdb_correct_hw_break,
583 };
584