xref: /openbmc/linux/arch/arm/kernel/kgdb.c (revision f14a0244)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * arch/arm/kernel/kgdb.c
4  *
5  * ARM KGDB support
6  *
7  * Copyright (c) 2002-2004 MontaVista Software, Inc
8  * Copyright (c) 2008 Wind River Systems, Inc.
9  *
10  * Authors:  George Davis <davis_g@mvista.com>
11  *           Deepak Saxena <dsaxena@plexity.net>
12  */
13 #include <linux/irq.h>
14 #include <linux/kdebug.h>
15 #include <linux/kgdb.h>
16 #include <linux/uaccess.h>
17 
18 #include <asm/patch.h>
19 #include <asm/traps.h>
20 
21 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] =
22 {
23 	{ "r0", 4, offsetof(struct pt_regs, ARM_r0)},
24 	{ "r1", 4, offsetof(struct pt_regs, ARM_r1)},
25 	{ "r2", 4, offsetof(struct pt_regs, ARM_r2)},
26 	{ "r3", 4, offsetof(struct pt_regs, ARM_r3)},
27 	{ "r4", 4, offsetof(struct pt_regs, ARM_r4)},
28 	{ "r5", 4, offsetof(struct pt_regs, ARM_r5)},
29 	{ "r6", 4, offsetof(struct pt_regs, ARM_r6)},
30 	{ "r7", 4, offsetof(struct pt_regs, ARM_r7)},
31 	{ "r8", 4, offsetof(struct pt_regs, ARM_r8)},
32 	{ "r9", 4, offsetof(struct pt_regs, ARM_r9)},
33 	{ "r10", 4, offsetof(struct pt_regs, ARM_r10)},
34 	{ "fp", 4, offsetof(struct pt_regs, ARM_fp)},
35 	{ "ip", 4, offsetof(struct pt_regs, ARM_ip)},
36 	{ "sp", 4, offsetof(struct pt_regs, ARM_sp)},
37 	{ "lr", 4, offsetof(struct pt_regs, ARM_lr)},
38 	{ "pc", 4, offsetof(struct pt_regs, ARM_pc)},
39 	{ "f0", 12, -1 },
40 	{ "f1", 12, -1 },
41 	{ "f2", 12, -1 },
42 	{ "f3", 12, -1 },
43 	{ "f4", 12, -1 },
44 	{ "f5", 12, -1 },
45 	{ "f6", 12, -1 },
46 	{ "f7", 12, -1 },
47 	{ "fps", 4, -1 },
48 	{ "cpsr", 4, offsetof(struct pt_regs, ARM_cpsr)},
49 };
50 
dbg_get_reg(int regno,void * mem,struct pt_regs * regs)51 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
52 {
53 	if (regno >= DBG_MAX_REG_NUM || regno < 0)
54 		return NULL;
55 
56 	if (dbg_reg_def[regno].offset != -1)
57 		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
58 		       dbg_reg_def[regno].size);
59 	else
60 		memset(mem, 0, dbg_reg_def[regno].size);
61 	return dbg_reg_def[regno].name;
62 }
63 
dbg_set_reg(int regno,void * mem,struct pt_regs * regs)64 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
65 {
66 	if (regno >= DBG_MAX_REG_NUM || regno < 0)
67 		return -EINVAL;
68 
69 	if (dbg_reg_def[regno].offset != -1)
70 		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
71 		       dbg_reg_def[regno].size);
72 	return 0;
73 }
74 
75 void
sleeping_thread_to_gdb_regs(unsigned long * gdb_regs,struct task_struct * task)76 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
77 {
78 	struct thread_info *ti;
79 	int regno;
80 
81 	/* Just making sure... */
82 	if (task == NULL)
83 		return;
84 
85 	/* Initialize to zero */
86 	for (regno = 0; regno < GDB_MAX_REGS; regno++)
87 		gdb_regs[regno] = 0;
88 
89 	/* Otherwise, we have only some registers from switch_to() */
90 	ti			= task_thread_info(task);
91 	gdb_regs[_R4]		= ti->cpu_context.r4;
92 	gdb_regs[_R5]		= ti->cpu_context.r5;
93 	gdb_regs[_R6]		= ti->cpu_context.r6;
94 	gdb_regs[_R7]		= ti->cpu_context.r7;
95 	gdb_regs[_R8]		= ti->cpu_context.r8;
96 	gdb_regs[_R9]		= ti->cpu_context.r9;
97 	gdb_regs[_R10]		= ti->cpu_context.sl;
98 	gdb_regs[_FP]		= ti->cpu_context.fp;
99 	gdb_regs[_SPT]		= ti->cpu_context.sp;
100 	gdb_regs[_PC]		= ti->cpu_context.pc;
101 }
102 
kgdb_arch_set_pc(struct pt_regs * regs,unsigned long pc)103 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
104 {
105 	regs->ARM_pc = pc;
106 }
107 
108 static int compiled_break;
109 
kgdb_arch_handle_exception(int exception_vector,int signo,int err_code,char * remcom_in_buffer,char * remcom_out_buffer,struct pt_regs * linux_regs)110 int kgdb_arch_handle_exception(int exception_vector, int signo,
111 			       int err_code, char *remcom_in_buffer,
112 			       char *remcom_out_buffer,
113 			       struct pt_regs *linux_regs)
114 {
115 	unsigned long addr;
116 	char *ptr;
117 
118 	switch (remcom_in_buffer[0]) {
119 	case 'D':
120 	case 'k':
121 	case 'c':
122 		/*
123 		 * Try to read optional parameter, pc unchanged if no parm.
124 		 * If this was a compiled breakpoint, we need to move
125 		 * to the next instruction or we will just breakpoint
126 		 * over and over again.
127 		 */
128 		ptr = &remcom_in_buffer[1];
129 		if (kgdb_hex2long(&ptr, &addr))
130 			linux_regs->ARM_pc = addr;
131 		else if (compiled_break == 1)
132 			linux_regs->ARM_pc += 4;
133 
134 		compiled_break = 0;
135 
136 		return 0;
137 	}
138 
139 	return -1;
140 }
141 
kgdb_brk_fn(struct pt_regs * regs,unsigned int instr)142 static int kgdb_brk_fn(struct pt_regs *regs, unsigned int instr)
143 {
144 	kgdb_handle_exception(1, SIGTRAP, 0, regs);
145 
146 	return 0;
147 }
148 
kgdb_compiled_brk_fn(struct pt_regs * regs,unsigned int instr)149 static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
150 {
151 	compiled_break = 1;
152 	kgdb_handle_exception(1, SIGTRAP, 0, regs);
153 
154 	return 0;
155 }
156 
157 static struct undef_hook kgdb_brkpt_arm_hook = {
158 	.instr_mask		= 0xffffffff,
159 	.instr_val		= KGDB_BREAKINST,
160 	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
161 	.cpsr_val		= SVC_MODE,
162 	.fn			= kgdb_brk_fn
163 };
164 
165 static struct undef_hook kgdb_brkpt_thumb_hook = {
166 	.instr_mask		= 0xffff,
167 	.instr_val		= KGDB_BREAKINST & 0xffff,
168 	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
169 	.cpsr_val		= PSR_T_BIT | SVC_MODE,
170 	.fn			= kgdb_brk_fn
171 };
172 
173 static struct undef_hook kgdb_compiled_brkpt_arm_hook = {
174 	.instr_mask		= 0xffffffff,
175 	.instr_val		= KGDB_COMPILED_BREAK,
176 	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
177 	.cpsr_val		= SVC_MODE,
178 	.fn			= kgdb_compiled_brk_fn
179 };
180 
181 static struct undef_hook kgdb_compiled_brkpt_thumb_hook = {
182 	.instr_mask		= 0xffff,
183 	.instr_val		= KGDB_COMPILED_BREAK & 0xffff,
184 	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
185 	.cpsr_val		= PSR_T_BIT | SVC_MODE,
186 	.fn			= kgdb_compiled_brk_fn
187 };
188 
__kgdb_notify(struct die_args * args,unsigned long cmd)189 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
190 {
191 	struct pt_regs *regs = args->regs;
192 
193 	if (kgdb_handle_exception(1, args->signr, cmd, regs))
194 		return NOTIFY_DONE;
195 	return NOTIFY_STOP;
196 }
197 static int
kgdb_notify(struct notifier_block * self,unsigned long cmd,void * ptr)198 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
199 {
200 	unsigned long flags;
201 	int ret;
202 
203 	local_irq_save(flags);
204 	ret = __kgdb_notify(ptr, cmd);
205 	local_irq_restore(flags);
206 
207 	return ret;
208 }
209 
210 static struct notifier_block kgdb_notifier = {
211 	.notifier_call	= kgdb_notify,
212 	.priority	= -INT_MAX,
213 };
214 
215 
216 /**
217  *	kgdb_arch_init - Perform any architecture specific initalization.
218  *
219  *	This function will handle the initalization of any architecture
220  *	specific callbacks.
221  */
kgdb_arch_init(void)222 int kgdb_arch_init(void)
223 {
224 	int ret = register_die_notifier(&kgdb_notifier);
225 
226 	if (ret != 0)
227 		return ret;
228 
229 	register_undef_hook(&kgdb_brkpt_arm_hook);
230 	register_undef_hook(&kgdb_brkpt_thumb_hook);
231 	register_undef_hook(&kgdb_compiled_brkpt_arm_hook);
232 	register_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
233 
234 	return 0;
235 }
236 
237 /**
238  *	kgdb_arch_exit - Perform any architecture specific uninitalization.
239  *
240  *	This function will handle the uninitalization of any architecture
241  *	specific callbacks, for dynamic registration and unregistration.
242  */
kgdb_arch_exit(void)243 void kgdb_arch_exit(void)
244 {
245 	unregister_undef_hook(&kgdb_brkpt_arm_hook);
246 	unregister_undef_hook(&kgdb_brkpt_thumb_hook);
247 	unregister_undef_hook(&kgdb_compiled_brkpt_arm_hook);
248 	unregister_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
249 	unregister_die_notifier(&kgdb_notifier);
250 }
251 
kgdb_arch_set_breakpoint(struct kgdb_bkpt * bpt)252 int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
253 {
254 	int err;
255 
256 	/* patch_text() only supports int-sized breakpoints */
257 	BUILD_BUG_ON(sizeof(int) != BREAK_INSTR_SIZE);
258 
259 	err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr,
260 				BREAK_INSTR_SIZE);
261 	if (err)
262 		return err;
263 
264 	/* Machine is already stopped, so we can use __patch_text() directly */
265 	__patch_text((void *)bpt->bpt_addr,
266 		     *(unsigned int *)arch_kgdb_ops.gdb_bpt_instr);
267 
268 	return err;
269 }
270 
kgdb_arch_remove_breakpoint(struct kgdb_bkpt * bpt)271 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
272 {
273 	/* Machine is already stopped, so we can use __patch_text() directly */
274 	__patch_text((void *)bpt->bpt_addr, *(unsigned int *)bpt->saved_instr);
275 
276 	return 0;
277 }
278 
279 /*
280  * Register our undef instruction hooks with ARM undef core.
281  * We register a hook specifically looking for the KGB break inst
282  * and we handle the normal undef case within the do_undefinstr
283  * handler.
284  */
285 const struct kgdb_arch arch_kgdb_ops = {
286 #ifndef __ARMEB__
287 	.gdb_bpt_instr		= {0xfe, 0xde, 0xff, 0xe7}
288 #else /* ! __ARMEB__ */
289 	.gdb_bpt_instr		= {0xe7, 0xff, 0xde, 0xfe}
290 #endif
291 };
292