1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * AArch64 KGDB support
4 *
5 * Based on arch/arm/kernel/kgdb.c
6 *
7 * Copyright (C) 2013 Cavium Inc.
8 * Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
9 */
10
11 #include <linux/bug.h>
12 #include <linux/irq.h>
13 #include <linux/kdebug.h>
14 #include <linux/kgdb.h>
15 #include <linux/kprobes.h>
16 #include <linux/sched/task_stack.h>
17
18 #include <asm/debug-monitors.h>
19 #include <asm/insn.h>
20 #include <asm/text-patching.h>
21 #include <asm/traps.h>
22
23 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
24 { "x0", 8, offsetof(struct pt_regs, regs[0])},
25 { "x1", 8, offsetof(struct pt_regs, regs[1])},
26 { "x2", 8, offsetof(struct pt_regs, regs[2])},
27 { "x3", 8, offsetof(struct pt_regs, regs[3])},
28 { "x4", 8, offsetof(struct pt_regs, regs[4])},
29 { "x5", 8, offsetof(struct pt_regs, regs[5])},
30 { "x6", 8, offsetof(struct pt_regs, regs[6])},
31 { "x7", 8, offsetof(struct pt_regs, regs[7])},
32 { "x8", 8, offsetof(struct pt_regs, regs[8])},
33 { "x9", 8, offsetof(struct pt_regs, regs[9])},
34 { "x10", 8, offsetof(struct pt_regs, regs[10])},
35 { "x11", 8, offsetof(struct pt_regs, regs[11])},
36 { "x12", 8, offsetof(struct pt_regs, regs[12])},
37 { "x13", 8, offsetof(struct pt_regs, regs[13])},
38 { "x14", 8, offsetof(struct pt_regs, regs[14])},
39 { "x15", 8, offsetof(struct pt_regs, regs[15])},
40 { "x16", 8, offsetof(struct pt_regs, regs[16])},
41 { "x17", 8, offsetof(struct pt_regs, regs[17])},
42 { "x18", 8, offsetof(struct pt_regs, regs[18])},
43 { "x19", 8, offsetof(struct pt_regs, regs[19])},
44 { "x20", 8, offsetof(struct pt_regs, regs[20])},
45 { "x21", 8, offsetof(struct pt_regs, regs[21])},
46 { "x22", 8, offsetof(struct pt_regs, regs[22])},
47 { "x23", 8, offsetof(struct pt_regs, regs[23])},
48 { "x24", 8, offsetof(struct pt_regs, regs[24])},
49 { "x25", 8, offsetof(struct pt_regs, regs[25])},
50 { "x26", 8, offsetof(struct pt_regs, regs[26])},
51 { "x27", 8, offsetof(struct pt_regs, regs[27])},
52 { "x28", 8, offsetof(struct pt_regs, regs[28])},
53 { "x29", 8, offsetof(struct pt_regs, regs[29])},
54 { "x30", 8, offsetof(struct pt_regs, regs[30])},
55 { "sp", 8, offsetof(struct pt_regs, sp)},
56 { "pc", 8, offsetof(struct pt_regs, pc)},
57 /*
58 * struct pt_regs thinks PSTATE is 64-bits wide but gdb remote
59 * protocol disagrees. Therefore we must extract only the lower
60 * 32-bits. Look for the big comment in asm/kgdb.h for more
61 * detail.
62 */
63 { "pstate", 4, offsetof(struct pt_regs, pstate)},
64 { "v0", 16, -1 },
65 { "v1", 16, -1 },
66 { "v2", 16, -1 },
67 { "v3", 16, -1 },
68 { "v4", 16, -1 },
69 { "v5", 16, -1 },
70 { "v6", 16, -1 },
71 { "v7", 16, -1 },
72 { "v8", 16, -1 },
73 { "v9", 16, -1 },
74 { "v10", 16, -1 },
75 { "v11", 16, -1 },
76 { "v12", 16, -1 },
77 { "v13", 16, -1 },
78 { "v14", 16, -1 },
79 { "v15", 16, -1 },
80 { "v16", 16, -1 },
81 { "v17", 16, -1 },
82 { "v18", 16, -1 },
83 { "v19", 16, -1 },
84 { "v20", 16, -1 },
85 { "v21", 16, -1 },
86 { "v22", 16, -1 },
87 { "v23", 16, -1 },
88 { "v24", 16, -1 },
89 { "v25", 16, -1 },
90 { "v26", 16, -1 },
91 { "v27", 16, -1 },
92 { "v28", 16, -1 },
93 { "v29", 16, -1 },
94 { "v30", 16, -1 },
95 { "v31", 16, -1 },
96 { "fpsr", 4, -1 },
97 { "fpcr", 4, -1 },
98 };
99
dbg_get_reg(int regno,void * mem,struct pt_regs * regs)100 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
101 {
102 if (regno >= DBG_MAX_REG_NUM || regno < 0)
103 return NULL;
104
105 if (dbg_reg_def[regno].offset != -1)
106 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
107 dbg_reg_def[regno].size);
108 else
109 memset(mem, 0, dbg_reg_def[regno].size);
110 return dbg_reg_def[regno].name;
111 }
112
dbg_set_reg(int regno,void * mem,struct pt_regs * regs)113 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
114 {
115 if (regno >= DBG_MAX_REG_NUM || regno < 0)
116 return -EINVAL;
117
118 if (dbg_reg_def[regno].offset != -1)
119 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
120 dbg_reg_def[regno].size);
121 return 0;
122 }
123
124 void
sleeping_thread_to_gdb_regs(unsigned long * gdb_regs,struct task_struct * task)125 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
126 {
127 struct cpu_context *cpu_context = &task->thread.cpu_context;
128
129 /* Initialize to zero */
130 memset((char *)gdb_regs, 0, NUMREGBYTES);
131
132 gdb_regs[19] = cpu_context->x19;
133 gdb_regs[20] = cpu_context->x20;
134 gdb_regs[21] = cpu_context->x21;
135 gdb_regs[22] = cpu_context->x22;
136 gdb_regs[23] = cpu_context->x23;
137 gdb_regs[24] = cpu_context->x24;
138 gdb_regs[25] = cpu_context->x25;
139 gdb_regs[26] = cpu_context->x26;
140 gdb_regs[27] = cpu_context->x27;
141 gdb_regs[28] = cpu_context->x28;
142 gdb_regs[29] = cpu_context->fp;
143
144 gdb_regs[31] = cpu_context->sp;
145 gdb_regs[32] = cpu_context->pc;
146 }
147
kgdb_arch_set_pc(struct pt_regs * regs,unsigned long pc)148 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
149 {
150 regs->pc = pc;
151 }
152
153 static int compiled_break;
154
kgdb_arch_update_addr(struct pt_regs * regs,char * remcom_in_buffer)155 static void kgdb_arch_update_addr(struct pt_regs *regs,
156 char *remcom_in_buffer)
157 {
158 unsigned long addr;
159 char *ptr;
160
161 ptr = &remcom_in_buffer[1];
162 if (kgdb_hex2long(&ptr, &addr))
163 kgdb_arch_set_pc(regs, addr);
164 else if (compiled_break == 1)
165 kgdb_arch_set_pc(regs, regs->pc + 4);
166
167 compiled_break = 0;
168 }
169
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)170 int kgdb_arch_handle_exception(int exception_vector, int signo,
171 int err_code, char *remcom_in_buffer,
172 char *remcom_out_buffer,
173 struct pt_regs *linux_regs)
174 {
175 int err;
176
177 switch (remcom_in_buffer[0]) {
178 case 'D':
179 case 'k':
180 /*
181 * Packet D (Detach), k (kill). No special handling
182 * is required here. Handle same as c packet.
183 */
184 case 'c':
185 /*
186 * Packet c (Continue) to continue executing.
187 * Set pc to required address.
188 * Try to read optional parameter and set pc.
189 * If this was a compiled breakpoint, we need to move
190 * to the next instruction else we will just breakpoint
191 * over and over again.
192 */
193 kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
194 atomic_set(&kgdb_cpu_doing_single_step, -1);
195 kgdb_single_step = 0;
196
197 /*
198 * Received continue command, disable single step
199 */
200 if (kernel_active_single_step())
201 kernel_disable_single_step();
202
203 err = 0;
204 break;
205 case 's':
206 /*
207 * Update step address value with address passed
208 * with step packet.
209 * On debug exception return PC is copied to ELR
210 * So just update PC.
211 * If no step address is passed, resume from the address
212 * pointed by PC. Do not update PC
213 */
214 kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
215 atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
216 kgdb_single_step = 1;
217
218 /*
219 * Enable single step handling
220 */
221 if (!kernel_active_single_step())
222 kernel_enable_single_step(linux_regs);
223 else
224 kernel_rewind_single_step(linux_regs);
225 err = 0;
226 break;
227 default:
228 err = -1;
229 }
230 return err;
231 }
232
kgdb_brk_handler(struct pt_regs * regs,unsigned long esr)233 int kgdb_brk_handler(struct pt_regs *regs, unsigned long esr)
234 {
235 kgdb_handle_exception(1, SIGTRAP, 0, regs);
236 return DBG_HOOK_HANDLED;
237 }
NOKPROBE_SYMBOL(kgdb_brk_handler)238 NOKPROBE_SYMBOL(kgdb_brk_handler)
239
240 int kgdb_compiled_brk_handler(struct pt_regs *regs, unsigned long esr)
241 {
242 compiled_break = 1;
243 kgdb_handle_exception(1, SIGTRAP, 0, regs);
244
245 return DBG_HOOK_HANDLED;
246 }
247 NOKPROBE_SYMBOL(kgdb_compiled_brk_handler);
248
kgdb_single_step_handler(struct pt_regs * regs,unsigned long esr)249 int kgdb_single_step_handler(struct pt_regs *regs, unsigned long esr)
250 {
251 if (!kgdb_single_step)
252 return DBG_HOOK_ERROR;
253
254 kgdb_handle_exception(0, SIGTRAP, 0, regs);
255 return DBG_HOOK_HANDLED;
256 }
257 NOKPROBE_SYMBOL(kgdb_single_step_handler);
258
__kgdb_notify(struct die_args * args,unsigned long cmd)259 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
260 {
261 struct pt_regs *regs = args->regs;
262
263 if (kgdb_handle_exception(1, args->signr, cmd, regs))
264 return NOTIFY_DONE;
265 return NOTIFY_STOP;
266 }
267
268 static int
kgdb_notify(struct notifier_block * self,unsigned long cmd,void * ptr)269 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
270 {
271 unsigned long flags;
272 int ret;
273
274 local_irq_save(flags);
275 ret = __kgdb_notify(ptr, cmd);
276 local_irq_restore(flags);
277
278 return ret;
279 }
280
281 static struct notifier_block kgdb_notifier = {
282 .notifier_call = kgdb_notify,
283 /*
284 * Want to be lowest priority
285 */
286 .priority = -INT_MAX,
287 };
288
289 /*
290 * kgdb_arch_init - Perform any architecture specific initialization.
291 * This function will handle the initialization of any architecture
292 * specific callbacks.
293 */
kgdb_arch_init(void)294 int kgdb_arch_init(void)
295 {
296 return register_die_notifier(&kgdb_notifier);
297 }
298
299 /*
300 * kgdb_arch_exit - Perform any architecture specific uninitalization.
301 * This function will handle the uninitalization of any architecture
302 * specific callbacks, for dynamic registration and unregistration.
303 */
kgdb_arch_exit(void)304 void kgdb_arch_exit(void)
305 {
306 unregister_die_notifier(&kgdb_notifier);
307 }
308
309 const struct kgdb_arch arch_kgdb_ops;
310
kgdb_arch_set_breakpoint(struct kgdb_bkpt * bpt)311 int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
312 {
313 int err;
314
315 BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
316
317 err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
318 if (err)
319 return err;
320
321 return aarch64_insn_write((void *)bpt->bpt_addr,
322 (u32)AARCH64_BREAK_KGDB_DYN_DBG);
323 }
324
kgdb_arch_remove_breakpoint(struct kgdb_bkpt * bpt)325 int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
326 {
327 return aarch64_insn_write((void *)bpt->bpt_addr,
328 *(u32 *)bpt->saved_instr);
329 }
330