kgdb.c

  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
 23struct 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#ifdef CONFIG_CPU_BIG_ENDIAN
 65							+ 4
 66#endif
 67	},
 68	{ "v0", 16, -1 },
 69	{ "v1", 16, -1 },
 70	{ "v2", 16, -1 },
 71	{ "v3", 16, -1 },
 72	{ "v4", 16, -1 },
 73	{ "v5", 16, -1 },
 74	{ "v6", 16, -1 },
 75	{ "v7", 16, -1 },
 76	{ "v8", 16, -1 },
 77	{ "v9", 16, -1 },
 78	{ "v10", 16, -1 },
 79	{ "v11", 16, -1 },
 80	{ "v12", 16, -1 },
 81	{ "v13", 16, -1 },
 82	{ "v14", 16, -1 },
 83	{ "v15", 16, -1 },
 84	{ "v16", 16, -1 },
 85	{ "v17", 16, -1 },
 86	{ "v18", 16, -1 },
 87	{ "v19", 16, -1 },
 88	{ "v20", 16, -1 },
 89	{ "v21", 16, -1 },
 90	{ "v22", 16, -1 },
 91	{ "v23", 16, -1 },
 92	{ "v24", 16, -1 },
 93	{ "v25", 16, -1 },
 94	{ "v26", 16, -1 },
 95	{ "v27", 16, -1 },
 96	{ "v28", 16, -1 },
 97	{ "v29", 16, -1 },
 98	{ "v30", 16, -1 },
 99	{ "v31", 16, -1 },
100	{ "fpsr", 4, -1 },
101	{ "fpcr", 4, -1 },
102};
103
104char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
105{
106	if (regno >= DBG_MAX_REG_NUM || regno < 0)
107		return NULL;
108
109	if (dbg_reg_def[regno].offset != -1)
110		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
111		       dbg_reg_def[regno].size);
112	else
113		memset(mem, 0, dbg_reg_def[regno].size);
114	return dbg_reg_def[regno].name;
115}
116
117int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
118{
119	if (regno >= DBG_MAX_REG_NUM || regno < 0)
120		return -EINVAL;
121
122	if (dbg_reg_def[regno].offset != -1)
123		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
124		       dbg_reg_def[regno].size);
125	return 0;
126}
127
128void
129sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
130{
131	struct cpu_context *cpu_context = &task->thread.cpu_context;
132
133	/* Initialize to zero */
134	memset((char *)gdb_regs, 0, NUMREGBYTES);
135
136	gdb_regs[19] = cpu_context->x19;
137	gdb_regs[20] = cpu_context->x20;
138	gdb_regs[21] = cpu_context->x21;
139	gdb_regs[22] = cpu_context->x22;
140	gdb_regs[23] = cpu_context->x23;
141	gdb_regs[24] = cpu_context->x24;
142	gdb_regs[25] = cpu_context->x25;
143	gdb_regs[26] = cpu_context->x26;
144	gdb_regs[27] = cpu_context->x27;
145	gdb_regs[28] = cpu_context->x28;
146	gdb_regs[29] = cpu_context->fp;
147
148	gdb_regs[31] = cpu_context->sp;
149	gdb_regs[32] = cpu_context->pc;
150}
151
152void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
153{
154	regs->pc = pc;
155}
156
157static int compiled_break;
158
159static void kgdb_arch_update_addr(struct pt_regs *regs,
160				char *remcom_in_buffer)
161{
162	unsigned long addr;
163	char *ptr;
164
165	ptr = &remcom_in_buffer[1];
166	if (kgdb_hex2long(&ptr, &addr))
167		kgdb_arch_set_pc(regs, addr);
168	else if (compiled_break == 1)
169		kgdb_arch_set_pc(regs, regs->pc + 4);
170
171	compiled_break = 0;
172}
173
174int kgdb_arch_handle_exception(int exception_vector, int signo,
175			       int err_code, char *remcom_in_buffer,
176			       char *remcom_out_buffer,
177			       struct pt_regs *linux_regs)
178{
179	int err;
180
181	switch (remcom_in_buffer[0]) {
182	case 'D':
183	case 'k':
184		/*
185		 * Packet D (Detach), k (kill). No special handling
186		 * is required here. Handle same as c packet.
187		 */
188	case 'c':
189		/*
190		 * Packet c (Continue) to continue executing.
191		 * Set pc to required address.
192		 * Try to read optional parameter and set pc.
193		 * If this was a compiled breakpoint, we need to move
194		 * to the next instruction else we will just breakpoint
195		 * over and over again.
196		 */
197		kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
198		atomic_set(&kgdb_cpu_doing_single_step, -1);
199		kgdb_single_step =  0;
200
201		/*
202		 * Received continue command, disable single step
203		 */
204		if (kernel_active_single_step())
205			kernel_disable_single_step();
206
207		err = 0;
208		break;
209	case 's':
210		/*
211		 * Update step address value with address passed
212		 * with step packet.
213		 * On debug exception return PC is copied to ELR
214		 * So just update PC.
215		 * If no step address is passed, resume from the address
216		 * pointed by PC. Do not update PC
217		 */
218		kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
219		atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
220		kgdb_single_step =  1;
221
222		/*
223		 * Enable single step handling
224		 */
225		if (!kernel_active_single_step())
226			kernel_enable_single_step(linux_regs);
227		else
228			kernel_rewind_single_step(linux_regs);
229		err = 0;
230		break;
231	default:
232		err = -1;
233	}
234	return err;
235}
236
237int kgdb_brk_handler(struct pt_regs *regs, unsigned long esr)
238{
239	kgdb_handle_exception(1, SIGTRAP, 0, regs);
240	return DBG_HOOK_HANDLED;
241}
242NOKPROBE_SYMBOL(kgdb_brk_handler)
243
244int kgdb_compiled_brk_handler(struct pt_regs *regs, unsigned long esr)
245{
246	compiled_break = 1;
247	kgdb_handle_exception(1, SIGTRAP, 0, regs);
248
249	return DBG_HOOK_HANDLED;
250}
251NOKPROBE_SYMBOL(kgdb_compiled_brk_handler);
252
253int kgdb_single_step_handler(struct pt_regs *regs, unsigned long esr)
254{
255	if (!kgdb_single_step)
256		return DBG_HOOK_ERROR;
257
258	kgdb_handle_exception(0, SIGTRAP, 0, regs);
259	return DBG_HOOK_HANDLED;
260}
261NOKPROBE_SYMBOL(kgdb_single_step_handler);
262
263static int __kgdb_notify(struct die_args *args, unsigned long cmd)
264{
265	struct pt_regs *regs = args->regs;
266
267	if (kgdb_handle_exception(1, args->signr, cmd, regs))
268		return NOTIFY_DONE;
269	return NOTIFY_STOP;
270}
271
272static int
273kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
274{
275	unsigned long flags;
276	int ret;
277
278	local_irq_save(flags);
279	ret = __kgdb_notify(ptr, cmd);
280	local_irq_restore(flags);
281
282	return ret;
283}
284
285static struct notifier_block kgdb_notifier = {
286	.notifier_call	= kgdb_notify,
287	/*
288	 * Want to be lowest priority
289	 */
290	.priority	= -INT_MAX,
291};
292
293/*
294 * kgdb_arch_init - Perform any architecture specific initialization.
295 * This function will handle the initialization of any architecture
296 * specific callbacks.
297 */
298int kgdb_arch_init(void)
299{
300	return register_die_notifier(&kgdb_notifier);
301}
302
303/*
304 * kgdb_arch_exit - Perform any architecture specific uninitalization.
305 * This function will handle the uninitalization of any architecture
306 * specific callbacks, for dynamic registration and unregistration.
307 */
308void kgdb_arch_exit(void)
309{
310	unregister_die_notifier(&kgdb_notifier);
311}
312
313const struct kgdb_arch arch_kgdb_ops;
314
315int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
316{
317	int err;
318
319	BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
320
321	err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
322	if (err)
323		return err;
324
325	return aarch64_insn_write((void *)bpt->bpt_addr,
326			(u32)AARCH64_BREAK_KGDB_DYN_DBG);
327}
328
329int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
330{
331	return aarch64_insn_write((void *)bpt->bpt_addr,
332			*(u32 *)bpt->saved_instr);
333}