• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /*
2  * SuperH KGDB support
3  *
4  * Copyright (C) 2008 - 2009  Paul Mundt
5  *
6  * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
7  *
8  * This file is subject to the terms and conditions of the GNU General Public
9  * License.  See the file "COPYING" in the main directory of this archive
10  * for more details.
11  */
12 #include <linux/kgdb.h>
13 #include <linux/kdebug.h>
14 #include <linux/irq.h>
15 #include <linux/io.h>
16 #include <asm/cacheflush.h>
17 #include <asm/traps.h>
18 
19 /* Macros for single step instruction identification */
20 #define OPCODE_BT(op)		(((op) & 0xff00) == 0x8900)
21 #define OPCODE_BF(op)		(((op) & 0xff00) == 0x8b00)
22 #define OPCODE_BTF_DISP(op)	(((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
23 				 (((op) & 0x7f ) << 1))
24 #define OPCODE_BFS(op)		(((op) & 0xff00) == 0x8f00)
25 #define OPCODE_BTS(op)		(((op) & 0xff00) == 0x8d00)
26 #define OPCODE_BRA(op)		(((op) & 0xf000) == 0xa000)
27 #define OPCODE_BRA_DISP(op)	(((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
28 				 (((op) & 0x7ff) << 1))
29 #define OPCODE_BRAF(op)		(((op) & 0xf0ff) == 0x0023)
30 #define OPCODE_BRAF_REG(op)	(((op) & 0x0f00) >> 8)
31 #define OPCODE_BSR(op)		(((op) & 0xf000) == 0xb000)
32 #define OPCODE_BSR_DISP(op)	(((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
33 				 (((op) & 0x7ff) << 1))
34 #define OPCODE_BSRF(op)		(((op) & 0xf0ff) == 0x0003)
35 #define OPCODE_BSRF_REG(op)	(((op) >> 8) & 0xf)
36 #define OPCODE_JMP(op)		(((op) & 0xf0ff) == 0x402b)
37 #define OPCODE_JMP_REG(op)	(((op) >> 8) & 0xf)
38 #define OPCODE_JSR(op)		(((op) & 0xf0ff) == 0x400b)
39 #define OPCODE_JSR_REG(op)	(((op) >> 8) & 0xf)
40 #define OPCODE_RTS(op)		((op) == 0xb)
41 #define OPCODE_RTE(op)		((op) == 0x2b)
42 
43 #define SR_T_BIT_MASK           0x1
44 #define STEP_OPCODE             0xc33d
45 
46 /* Calculate the new address for after a step */
get_step_address(struct pt_regs * linux_regs)47 static short *get_step_address(struct pt_regs *linux_regs)
48 {
49 	insn_size_t op = __raw_readw(linux_regs->pc);
50 	long addr;
51 
52 	/* BT */
53 	if (OPCODE_BT(op)) {
54 		if (linux_regs->sr & SR_T_BIT_MASK)
55 			addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
56 		else
57 			addr = linux_regs->pc + 2;
58 	}
59 
60 	/* BTS */
61 	else if (OPCODE_BTS(op)) {
62 		if (linux_regs->sr & SR_T_BIT_MASK)
63 			addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
64 		else
65 			addr = linux_regs->pc + 4;	/* Not in delay slot */
66 	}
67 
68 	/* BF */
69 	else if (OPCODE_BF(op)) {
70 		if (!(linux_regs->sr & SR_T_BIT_MASK))
71 			addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
72 		else
73 			addr = linux_regs->pc + 2;
74 	}
75 
76 	/* BFS */
77 	else if (OPCODE_BFS(op)) {
78 		if (!(linux_regs->sr & SR_T_BIT_MASK))
79 			addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
80 		else
81 			addr = linux_regs->pc + 4;	/* Not in delay slot */
82 	}
83 
84 	/* BRA */
85 	else if (OPCODE_BRA(op))
86 		addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);
87 
88 	/* BRAF */
89 	else if (OPCODE_BRAF(op))
90 		addr = linux_regs->pc + 4
91 		    + linux_regs->regs[OPCODE_BRAF_REG(op)];
92 
93 	/* BSR */
94 	else if (OPCODE_BSR(op))
95 		addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);
96 
97 	/* BSRF */
98 	else if (OPCODE_BSRF(op))
99 		addr = linux_regs->pc + 4
100 		    + linux_regs->regs[OPCODE_BSRF_REG(op)];
101 
102 	/* JMP */
103 	else if (OPCODE_JMP(op))
104 		addr = linux_regs->regs[OPCODE_JMP_REG(op)];
105 
106 	/* JSR */
107 	else if (OPCODE_JSR(op))
108 		addr = linux_regs->regs[OPCODE_JSR_REG(op)];
109 
110 	/* RTS */
111 	else if (OPCODE_RTS(op))
112 		addr = linux_regs->pr;
113 
114 	/* RTE */
115 	else if (OPCODE_RTE(op))
116 		addr = linux_regs->regs[15];
117 
118 	/* Other */
119 	else
120 		addr = linux_regs->pc + instruction_size(op);
121 
122 	flush_icache_range(addr, addr + instruction_size(op));
123 	return (short *)addr;
124 }
125 
126 /*
127  * Replace the instruction immediately after the current instruction
128  * (i.e. next in the expected flow of control) with a trap instruction,
129  * so that returning will cause only a single instruction to be executed.
130  * Note that this model is slightly broken for instructions with delay
131  * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
132  * instruction in the delay slot will be executed.
133  */
134 
135 static unsigned long stepped_address;
136 static insn_size_t stepped_opcode;
137 
do_single_step(struct pt_regs * linux_regs)138 static void do_single_step(struct pt_regs *linux_regs)
139 {
140 	/* Determine where the target instruction will send us to */
141 	unsigned short *addr = get_step_address(linux_regs);
142 
143 	stepped_address = (int)addr;
144 
145 	/* Replace it */
146 	stepped_opcode = __raw_readw((long)addr);
147 	*addr = STEP_OPCODE;
148 
149 	/* Flush and return */
150 	flush_icache_range((long)addr, (long)addr +
151 			   instruction_size(stepped_opcode));
152 }
153 
154 /* Undo a single step */
undo_single_step(struct pt_regs * linux_regs)155 static void undo_single_step(struct pt_regs *linux_regs)
156 {
157 	/* If we have stepped, put back the old instruction */
158 	/* Use stepped_address in case we stopped elsewhere */
159 	if (stepped_opcode != 0) {
160 		__raw_writew(stepped_opcode, stepped_address);
161 		flush_icache_range(stepped_address, stepped_address + 2);
162 	}
163 
164 	stepped_opcode = 0;
165 }
166 
pt_regs_to_gdb_regs(unsigned long * gdb_regs,struct pt_regs * regs)167 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
168 {
169 	int i;
170 
171 	for (i = 0; i < 16; i++)
172 		gdb_regs[GDB_R0 + i] = regs->regs[i];
173 
174 	gdb_regs[GDB_PC] = regs->pc;
175 	gdb_regs[GDB_PR] = regs->pr;
176 	gdb_regs[GDB_SR] = regs->sr;
177 	gdb_regs[GDB_GBR] = regs->gbr;
178 	gdb_regs[GDB_MACH] = regs->mach;
179 	gdb_regs[GDB_MACL] = regs->macl;
180 
181 	__asm__ __volatile__ ("stc vbr, %0" : "=r" (gdb_regs[GDB_VBR]));
182 }
183 
gdb_regs_to_pt_regs(unsigned long * gdb_regs,struct pt_regs * regs)184 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
185 {
186 	int i;
187 
188 	for (i = 0; i < 16; i++)
189 		regs->regs[GDB_R0 + i] = gdb_regs[GDB_R0 + i];
190 
191 	regs->pc = gdb_regs[GDB_PC];
192 	regs->pr = gdb_regs[GDB_PR];
193 	regs->sr = gdb_regs[GDB_SR];
194 	regs->gbr = gdb_regs[GDB_GBR];
195 	regs->mach = gdb_regs[GDB_MACH];
196 	regs->macl = gdb_regs[GDB_MACL];
197 }
198 
sleeping_thread_to_gdb_regs(unsigned long * gdb_regs,struct task_struct * p)199 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
200 {
201 	gdb_regs[GDB_R15] = p->thread.sp;
202 	gdb_regs[GDB_PC] = p->thread.pc;
203 }
204 
kgdb_arch_handle_exception(int e_vector,int signo,int err_code,char * remcomInBuffer,char * remcomOutBuffer,struct pt_regs * linux_regs)205 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
206 			       char *remcomInBuffer, char *remcomOutBuffer,
207 			       struct pt_regs *linux_regs)
208 {
209 	unsigned long addr;
210 	char *ptr;
211 
212 	/* Undo any stepping we may have done */
213 	undo_single_step(linux_regs);
214 
215 	switch (remcomInBuffer[0]) {
216 	case 'c':
217 	case 's':
218 		/* try to read optional parameter, pc unchanged if no parm */
219 		ptr = &remcomInBuffer[1];
220 		if (kgdb_hex2long(&ptr, &addr))
221 			linux_regs->pc = addr;
222 	case 'D':
223 	case 'k':
224 		atomic_set(&kgdb_cpu_doing_single_step, -1);
225 
226 		if (remcomInBuffer[0] == 's') {
227 			do_single_step(linux_regs);
228 			kgdb_single_step = 1;
229 
230 			atomic_set(&kgdb_cpu_doing_single_step,
231 				   raw_smp_processor_id());
232 		}
233 
234 		return 0;
235 	}
236 
237 	/* this means that we do not want to exit from the handler: */
238 	return -1;
239 }
240 
kgdb_arch_pc(int exception,struct pt_regs * regs)241 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
242 {
243 	if (exception == 60)
244 		return instruction_pointer(regs) - 2;
245 	return instruction_pointer(regs);
246 }
247 
kgdb_arch_set_pc(struct pt_regs * regs,unsigned long ip)248 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
249 {
250 	regs->pc = ip;
251 }
252 
253 /*
254  * The primary entry points for the kgdb debug trap table entries.
255  */
BUILD_TRAP_HANDLER(singlestep)256 BUILD_TRAP_HANDLER(singlestep)
257 {
258 	unsigned long flags;
259 	TRAP_HANDLER_DECL;
260 
261 	local_irq_save(flags);
262 	regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
263 	kgdb_handle_exception(0, SIGTRAP, 0, regs);
264 	local_irq_restore(flags);
265 }
266 
__kgdb_notify(struct die_args * args,unsigned long cmd)267 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
268 {
269 	int ret;
270 
271 	switch (cmd) {
272 	case DIE_BREAKPOINT:
273 		/*
274 		 * This means a user thread is single stepping
275 		 * a system call which should be ignored
276 		 */
277 		if (test_thread_flag(TIF_SINGLESTEP))
278 			return NOTIFY_DONE;
279 
280 		ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
281 					    args->err, args->regs);
282 		if (ret)
283 			return NOTIFY_DONE;
284 
285 		break;
286 	}
287 
288 	return NOTIFY_STOP;
289 }
290 
291 static int
kgdb_notify(struct notifier_block * self,unsigned long cmd,void * ptr)292 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
293 {
294 	unsigned long flags;
295 	int ret;
296 
297 	local_irq_save(flags);
298 	ret = __kgdb_notify(ptr, cmd);
299 	local_irq_restore(flags);
300 
301 	return ret;
302 }
303 
304 static struct notifier_block kgdb_notifier = {
305 	.notifier_call	= kgdb_notify,
306 
307 	/*
308 	 * Lowest-prio notifier priority, we want to be notified last:
309 	 */
310 	.priority	= -INT_MAX,
311 };
312 
kgdb_arch_init(void)313 int kgdb_arch_init(void)
314 {
315 	return register_die_notifier(&kgdb_notifier);
316 }
317 
kgdb_arch_exit(void)318 void kgdb_arch_exit(void)
319 {
320 	unregister_die_notifier(&kgdb_notifier);
321 }
322 
323 struct kgdb_arch arch_kgdb_ops = {
324 	/* Breakpoint instruction: trapa #0x3c */
325 #ifdef CONFIG_CPU_LITTLE_ENDIAN
326 	.gdb_bpt_instr		= { 0x3c, 0xc3 },
327 #else
328 	.gdb_bpt_instr		= { 0xc3, 0x3c },
329 #endif
330 };
331