xref: /openbmc/linux/arch/mips/kernel/kgdb.c (revision e6ce4a48)
1 /*
2  *  Originally written by Glenn Engel, Lake Stevens Instrument Division
3  *
4  *  Contributed by HP Systems
5  *
6  *  Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
7  *  Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
8  *
9  *  Copyright (C) 1995 Andreas Busse
10  *
11  *  Copyright (C) 2003 MontaVista Software Inc.
12  *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
13  *
14  *  Copyright (C) 2004-2005 MontaVista Software Inc.
15  *  Author: Manish Lachwani, mlachwani@mvista.com or manish@koffee-break.com
16  *
17  *  Copyright (C) 2007-2008 Wind River Systems, Inc.
18  *  Author/Maintainer: Jason Wessel, jason.wessel@windriver.com
19  *
20  *  This file is licensed under the terms of the GNU General Public License
21  *  version 2. This program is licensed "as is" without any warranty of any
22  *  kind, whether express or implied.
23  */
24 
25 #include <linux/ptrace.h>		/* for linux pt_regs struct */
26 #include <linux/kgdb.h>
27 #include <linux/kdebug.h>
28 #include <linux/sched.h>
29 #include <linux/smp.h>
30 #include <asm/inst.h>
31 #include <asm/fpu.h>
32 #include <asm/cacheflush.h>
33 #include <asm/processor.h>
34 #include <asm/sigcontext.h>
35 #include <asm/irq_regs.h>
36 
37 static struct hard_trap_info {
38 	unsigned char tt;	/* Trap type code for MIPS R3xxx and R4xxx */
39 	unsigned char signo;	/* Signal that we map this trap into */
40 } hard_trap_info[] = {
41 	{ 6, SIGBUS },		/* instruction bus error */
42 	{ 7, SIGBUS },		/* data bus error */
43 	{ 9, SIGTRAP },		/* break */
44 /*	{ 11, SIGILL }, */	/* CPU unusable */
45 	{ 12, SIGFPE },		/* overflow */
46 	{ 13, SIGTRAP },	/* trap */
47 	{ 14, SIGSEGV },	/* virtual instruction cache coherency */
48 	{ 15, SIGFPE },		/* floating point exception */
49 	{ 23, SIGSEGV },	/* watch */
50 	{ 31, SIGSEGV },	/* virtual data cache coherency */
51 	{ 0, 0}			/* Must be last */
52 };
53 
54 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
55 {
56 	{ "zero", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
57 	{ "at", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
58 	{ "v0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
59 	{ "v1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
60 	{ "a0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
61 	{ "a1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
62 	{ "a2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
63 	{ "a3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
64 	{ "t0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
65 	{ "t1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
66 	{ "t2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
67 	{ "t3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
68 	{ "t4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
69 	{ "t5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
70 	{ "t6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
71 	{ "t7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
72 	{ "s0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[16]) },
73 	{ "s1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[17]) },
74 	{ "s2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[18]) },
75 	{ "s3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[19]) },
76 	{ "s4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[20]) },
77 	{ "s5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[21]) },
78 	{ "s6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[22]) },
79 	{ "s7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[23]) },
80 	{ "t8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[24]) },
81 	{ "t9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[25]) },
82 	{ "k0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[26]) },
83 	{ "k1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[27]) },
84 	{ "gp", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[28]) },
85 	{ "sp", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[29]) },
86 	{ "s8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[30]) },
87 	{ "ra", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[31]) },
88 	{ "sr", GDB_SIZEOF_REG, offsetof(struct pt_regs, cp0_status) },
89 	{ "lo", GDB_SIZEOF_REG, offsetof(struct pt_regs, lo) },
90 	{ "hi", GDB_SIZEOF_REG, offsetof(struct pt_regs, hi) },
91 	{ "bad", GDB_SIZEOF_REG, offsetof(struct pt_regs, cp0_badvaddr) },
92 	{ "cause", GDB_SIZEOF_REG, offsetof(struct pt_regs, cp0_cause) },
93 	{ "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, cp0_epc) },
94 	{ "f0", GDB_SIZEOF_REG, 0 },
95 	{ "f1", GDB_SIZEOF_REG, 1 },
96 	{ "f2", GDB_SIZEOF_REG, 2 },
97 	{ "f3", GDB_SIZEOF_REG, 3 },
98 	{ "f4", GDB_SIZEOF_REG, 4 },
99 	{ "f5", GDB_SIZEOF_REG, 5 },
100 	{ "f6", GDB_SIZEOF_REG, 6 },
101 	{ "f7", GDB_SIZEOF_REG, 7 },
102 	{ "f8", GDB_SIZEOF_REG, 8 },
103 	{ "f9", GDB_SIZEOF_REG, 9 },
104 	{ "f10", GDB_SIZEOF_REG, 10 },
105 	{ "f11", GDB_SIZEOF_REG, 11 },
106 	{ "f12", GDB_SIZEOF_REG, 12 },
107 	{ "f13", GDB_SIZEOF_REG, 13 },
108 	{ "f14", GDB_SIZEOF_REG, 14 },
109 	{ "f15", GDB_SIZEOF_REG, 15 },
110 	{ "f16", GDB_SIZEOF_REG, 16 },
111 	{ "f17", GDB_SIZEOF_REG, 17 },
112 	{ "f18", GDB_SIZEOF_REG, 18 },
113 	{ "f19", GDB_SIZEOF_REG, 19 },
114 	{ "f20", GDB_SIZEOF_REG, 20 },
115 	{ "f21", GDB_SIZEOF_REG, 21 },
116 	{ "f22", GDB_SIZEOF_REG, 22 },
117 	{ "f23", GDB_SIZEOF_REG, 23 },
118 	{ "f24", GDB_SIZEOF_REG, 24 },
119 	{ "f25", GDB_SIZEOF_REG, 25 },
120 	{ "f26", GDB_SIZEOF_REG, 26 },
121 	{ "f27", GDB_SIZEOF_REG, 27 },
122 	{ "f28", GDB_SIZEOF_REG, 28 },
123 	{ "f29", GDB_SIZEOF_REG, 29 },
124 	{ "f30", GDB_SIZEOF_REG, 30 },
125 	{ "f31", GDB_SIZEOF_REG, 31 },
126 	{ "fsr", GDB_SIZEOF_REG, 0 },
127 	{ "fir", GDB_SIZEOF_REG, 0 },
128 };
129 
dbg_set_reg(int regno,void * mem,struct pt_regs * regs)130 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
131 {
132 	int fp_reg;
133 
134 	if (regno < 0 || regno >= DBG_MAX_REG_NUM)
135 		return -EINVAL;
136 
137 	if (dbg_reg_def[regno].offset != -1 && regno < 38) {
138 		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
139 		       dbg_reg_def[regno].size);
140 	} else if (current && dbg_reg_def[regno].offset != -1 && regno < 72) {
141 		/* FP registers 38 -> 69 */
142 		if (!(regs->cp0_status & ST0_CU1))
143 			return 0;
144 		if (regno == 70) {
145 			/* Process the fcr31/fsr (register 70) */
146 			memcpy((void *)&current->thread.fpu.fcr31, mem,
147 			       dbg_reg_def[regno].size);
148 			goto out_save;
149 		} else if (regno == 71) {
150 			/* Ignore the fir (register 71) */
151 			goto out_save;
152 		}
153 		fp_reg = dbg_reg_def[regno].offset;
154 		memcpy((void *)&current->thread.fpu.fpr[fp_reg], mem,
155 		       dbg_reg_def[regno].size);
156 out_save:
157 		restore_fp(current);
158 	}
159 
160 	return 0;
161 }
162 
dbg_get_reg(int regno,void * mem,struct pt_regs * regs)163 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
164 {
165 	int fp_reg;
166 
167 	if (regno >= DBG_MAX_REG_NUM || regno < 0)
168 		return NULL;
169 
170 	if (dbg_reg_def[regno].offset != -1 && regno < 38) {
171 		/* First 38 registers */
172 		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
173 		       dbg_reg_def[regno].size);
174 	} else if (current && dbg_reg_def[regno].offset != -1 && regno < 72) {
175 		/* FP registers 38 -> 69 */
176 		if (!(regs->cp0_status & ST0_CU1))
177 			goto out;
178 		save_fp(current);
179 		if (regno == 70) {
180 			/* Process the fcr31/fsr (register 70) */
181 			memcpy(mem, (void *)&current->thread.fpu.fcr31,
182 			       dbg_reg_def[regno].size);
183 			goto out;
184 		} else if (regno == 71) {
185 			/* Ignore the fir (register 71) */
186 			memset(mem, 0, dbg_reg_def[regno].size);
187 			goto out;
188 		}
189 		fp_reg = dbg_reg_def[regno].offset;
190 		memcpy(mem, (void *)&current->thread.fpu.fpr[fp_reg],
191 		       dbg_reg_def[regno].size);
192 	}
193 
194 out:
195 	return dbg_reg_def[regno].name;
196 
197 }
198 
arch_kgdb_breakpoint(void)199 void arch_kgdb_breakpoint(void)
200 {
201 	__asm__ __volatile__(
202 		".globl breakinst\n\t"
203 		".set\tnoreorder\n\t"
204 		"nop\n"
205 		"breakinst:\tbreak\n\t"
206 		"nop\n\t"
207 		".set\treorder");
208 }
209 
compute_signal(int tt)210 static int compute_signal(int tt)
211 {
212 	struct hard_trap_info *ht;
213 
214 	for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
215 		if (ht->tt == tt)
216 			return ht->signo;
217 
218 	return SIGHUP;		/* default for things we don't know about */
219 }
220 
221 /*
222  * Similar to regs_to_gdb_regs() except that process is sleeping and so
223  * we may not be able to get all the info.
224  */
sleeping_thread_to_gdb_regs(unsigned long * gdb_regs,struct task_struct * p)225 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
226 {
227 	int reg;
228 #if (KGDB_GDB_REG_SIZE == 32)
229 	u32 *ptr = (u32 *)gdb_regs;
230 #else
231 	u64 *ptr = (u64 *)gdb_regs;
232 #endif
233 
234 	for (reg = 0; reg < 16; reg++)
235 		*(ptr++) = 0;
236 
237 	/* S0 - S7 */
238 	*(ptr++) = p->thread.reg16;
239 	*(ptr++) = p->thread.reg17;
240 	*(ptr++) = p->thread.reg18;
241 	*(ptr++) = p->thread.reg19;
242 	*(ptr++) = p->thread.reg20;
243 	*(ptr++) = p->thread.reg21;
244 	*(ptr++) = p->thread.reg22;
245 	*(ptr++) = p->thread.reg23;
246 
247 	for (reg = 24; reg < 28; reg++)
248 		*(ptr++) = 0;
249 
250 	/* GP, SP, FP, RA */
251 	*(ptr++) = (long)p;
252 	*(ptr++) = p->thread.reg29;
253 	*(ptr++) = p->thread.reg30;
254 	*(ptr++) = p->thread.reg31;
255 
256 	*(ptr++) = p->thread.cp0_status;
257 
258 	/* lo, hi */
259 	*(ptr++) = 0;
260 	*(ptr++) = 0;
261 
262 	/*
263 	 * BadVAddr, Cause
264 	 * Ideally these would come from the last exception frame up the stack
265 	 * but that requires unwinding, otherwise we can't know much for sure.
266 	 */
267 	*(ptr++) = 0;
268 	*(ptr++) = 0;
269 
270 	/*
271 	 * PC
272 	 * use return address (RA), i.e. the moment after return from resume()
273 	 */
274 	*(ptr++) = p->thread.reg31;
275 }
276 
kgdb_arch_set_pc(struct pt_regs * regs,unsigned long pc)277 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
278 {
279 	regs->cp0_epc = pc;
280 }
281 
282 /*
283  * Calls linux_debug_hook before the kernel dies. If KGDB is enabled,
284  * then try to fall into the debugger
285  */
kgdb_mips_notify(struct notifier_block * self,unsigned long cmd,void * ptr)286 static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
287 			    void *ptr)
288 {
289 	struct die_args *args = (struct die_args *)ptr;
290 	struct pt_regs *regs = args->regs;
291 	int trap = (regs->cp0_cause & 0x7c) >> 2;
292 
293 #ifdef CONFIG_KPROBES
294 	/*
295 	 * Return immediately if the kprobes fault notifier has set
296 	 * DIE_PAGE_FAULT.
297 	 */
298 	if (cmd == DIE_PAGE_FAULT)
299 		return NOTIFY_DONE;
300 #endif /* CONFIG_KPROBES */
301 
302 	/* Userspace events, ignore. */
303 	if (user_mode(regs))
304 		return NOTIFY_DONE;
305 
306 	if (atomic_read(&kgdb_active) != -1)
307 		kgdb_nmicallback(smp_processor_id(), regs);
308 
309 	if (kgdb_handle_exception(trap, compute_signal(trap), cmd, regs))
310 		return NOTIFY_DONE;
311 
312 	if (atomic_read(&kgdb_setting_breakpoint))
313 		if ((trap == 9) && (regs->cp0_epc == (unsigned long)breakinst))
314 			regs->cp0_epc += 4;
315 
316 	/* In SMP mode, __flush_cache_all does IPI */
317 	local_irq_enable();
318 	__flush_cache_all();
319 
320 	return NOTIFY_STOP;
321 }
322 
323 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
kgdb_ll_trap(int cmd,const char * str,struct pt_regs * regs,long err,int trap,int sig)324 int kgdb_ll_trap(int cmd, const char *str,
325 		 struct pt_regs *regs, long err, int trap, int sig)
326 {
327 	struct die_args args = {
328 		.regs	= regs,
329 		.str	= str,
330 		.err	= err,
331 		.trapnr = trap,
332 		.signr	= sig,
333 
334 	};
335 
336 	if (!kgdb_io_module_registered)
337 		return NOTIFY_DONE;
338 
339 	return kgdb_mips_notify(NULL, cmd, &args);
340 }
341 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
342 
343 static struct notifier_block kgdb_notifier = {
344 	.notifier_call = kgdb_mips_notify,
345 };
346 
347 /*
348  * Handle the 'c' command
349  */
kgdb_arch_handle_exception(int vector,int signo,int err_code,char * remcom_in_buffer,char * remcom_out_buffer,struct pt_regs * regs)350 int kgdb_arch_handle_exception(int vector, int signo, int err_code,
351 			       char *remcom_in_buffer, char *remcom_out_buffer,
352 			       struct pt_regs *regs)
353 {
354 	char *ptr;
355 	unsigned long address;
356 
357 	switch (remcom_in_buffer[0]) {
358 	case 'c':
359 		/* handle the optional parameter */
360 		ptr = &remcom_in_buffer[1];
361 		if (kgdb_hex2long(&ptr, &address))
362 			regs->cp0_epc = address;
363 
364 		return 0;
365 	}
366 
367 	return -1;
368 }
369 
370 const struct kgdb_arch arch_kgdb_ops = {
371 #ifdef CONFIG_CPU_BIG_ENDIAN
372 	.gdb_bpt_instr = { spec_op << 2, 0x00, 0x00, break_op },
373 #else
374 	.gdb_bpt_instr = { break_op, 0x00, 0x00, spec_op << 2 },
375 #endif
376 };
377 
kgdb_arch_init(void)378 int kgdb_arch_init(void)
379 {
380 	register_die_notifier(&kgdb_notifier);
381 
382 	return 0;
383 }
384 
385 /*
386  *	kgdb_arch_exit - Perform any architecture specific uninitalization.
387  *
388  *	This function will handle the uninitalization of any architecture
389  *	specific callbacks, for dynamic registration and unregistration.
390  */
kgdb_arch_exit(void)391 void kgdb_arch_exit(void)
392 {
393 	unregister_die_notifier(&kgdb_notifier);
394 }
395