1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * SuperH KGDB support
4 *
5 * Copyright (C) 2008 - 2012 Paul Mundt
6 *
7 * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
8 */
9 #include <linux/kgdb.h>
10 #include <linux/kdebug.h>
11 #include <linux/irq.h>
12 #include <linux/io.h>
13 #include <linux/sched.h>
14 #include <linux/sched/task_stack.h>
15
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 */
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
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 */
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
167 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
168 { "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
169 { "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
170 { "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
171 { "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
172 { "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
173 { "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
174 { "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
175 { "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
176 { "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
177 { "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
178 { "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
179 { "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
180 { "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
181 { "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
182 { "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
183 { "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
184 { "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) },
185 { "pr", GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) },
186 { "sr", GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) },
187 { "gbr", GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) },
188 { "mach", GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) },
189 { "macl", GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) },
190 { "vbr", GDB_SIZEOF_REG, -1 },
191 };
192
193 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
194 {
195 if (regno < 0 || regno >= DBG_MAX_REG_NUM)
196 return -EINVAL;
197
198 if (dbg_reg_def[regno].offset != -1)
199 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
200 dbg_reg_def[regno].size);
201
202 return 0;
203 }
204
205 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
206 {
207 if (regno >= DBG_MAX_REG_NUM || regno < 0)
208 return NULL;
209
210 if (dbg_reg_def[regno].size != -1)
211 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
212 dbg_reg_def[regno].size);
213
214 switch (regno) {
215 case GDB_VBR:
216 __asm__ __volatile__ ("stc vbr, %0" : "=r" (mem));
217 break;
218 }
219
220 return dbg_reg_def[regno].name;
221 }
222
223 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
224 {
225 struct pt_regs *thread_regs = task_pt_regs(p);
226 int reg;
227
228 /* Initialize to zero */
229 for (reg = 0; reg < DBG_MAX_REG_NUM; reg++)
230 gdb_regs[reg] = 0;
231
232 /*
233 * Copy out GP regs 8 to 14.
234 *
235 * switch_to() relies on SR.RB toggling, so regs 0->7 are banked
236 * and need privileged instructions to get to. The r15 value we
237 * fetch from the thread info directly.
238 */
239 for (reg = GDB_R8; reg < GDB_R15; reg++)
240 gdb_regs[reg] = thread_regs->regs[reg];
241
242 gdb_regs[GDB_R15] = p->thread.sp;
243 gdb_regs[GDB_PC] = p->thread.pc;
244
245 /*
246 * Additional registers we have context for
247 */
248 gdb_regs[GDB_PR] = thread_regs->pr;
249 gdb_regs[GDB_GBR] = thread_regs->gbr;
250 }
251
252 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
253 char *remcomInBuffer, char *remcomOutBuffer,
254 struct pt_regs *linux_regs)
255 {
256 unsigned long addr;
257 char *ptr;
258
259 /* Undo any stepping we may have done */
260 undo_single_step(linux_regs);
261
262 switch (remcomInBuffer[0]) {
263 case 'c':
264 case 's':
265 /* try to read optional parameter, pc unchanged if no parm */
266 ptr = &remcomInBuffer[1];
267 if (kgdb_hex2long(&ptr, &addr))
268 linux_regs->pc = addr;
269 fallthrough;
270 case 'D':
271 case 'k':
272 atomic_set(&kgdb_cpu_doing_single_step, -1);
273
274 if (remcomInBuffer[0] == 's') {
275 do_single_step(linux_regs);
276 kgdb_single_step = 1;
277
278 atomic_set(&kgdb_cpu_doing_single_step,
279 raw_smp_processor_id());
280 }
281
282 return 0;
283 }
284
285 /* this means that we do not want to exit from the handler: */
286 return -1;
287 }
288
289 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
290 {
291 if (exception == 60)
292 return instruction_pointer(regs) - 2;
293 return instruction_pointer(regs);
294 }
295
296 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
297 {
298 regs->pc = ip;
299 }
300
301 /*
302 * The primary entry points for the kgdb debug trap table entries.
303 */
304 BUILD_TRAP_HANDLER(singlestep)
305 {
306 unsigned long flags;
307 TRAP_HANDLER_DECL;
308
309 local_irq_save(flags);
310 regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
311 kgdb_handle_exception(0, SIGTRAP, 0, regs);
312 local_irq_restore(flags);
313 }
314
315 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
316 {
317 int ret;
318
319 switch (cmd) {
320 case DIE_BREAKPOINT:
321 /*
322 * This means a user thread is single stepping
323 * a system call which should be ignored
324 */
325 if (test_thread_flag(TIF_SINGLESTEP))
326 return NOTIFY_DONE;
327
328 ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
329 args->err, args->regs);
330 if (ret)
331 return NOTIFY_DONE;
332
333 break;
334 }
335
336 return NOTIFY_STOP;
337 }
338
339 static int
340 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
341 {
342 unsigned long flags;
343 int ret;
344
345 local_irq_save(flags);
346 ret = __kgdb_notify(ptr, cmd);
347 local_irq_restore(flags);
348
349 return ret;
350 }
351
352 static struct notifier_block kgdb_notifier = {
353 .notifier_call = kgdb_notify,
354
355 /*
356 * Lowest-prio notifier priority, we want to be notified last:
357 */
358 .priority = -INT_MAX,
359 };
360
361 int kgdb_arch_init(void)
362 {
363 return register_die_notifier(&kgdb_notifier);
364 }
365
366 void kgdb_arch_exit(void)
367 {
368 unregister_die_notifier(&kgdb_notifier);
369 }
370
371 const struct kgdb_arch arch_kgdb_ops = {
372 /* Breakpoint instruction: trapa #0x3c */
373 #ifdef CONFIG_CPU_LITTLE_ENDIAN
374 .gdb_bpt_instr = { 0x3c, 0xc3 },
375 #else
376 .gdb_bpt_instr = { 0xc3, 0x3c },
377 #endif
378 };
379
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