1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Kernel probes (kprobes) for SuperH
4 *
5 * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
6 * Copyright (C) 2006 Lineo Solutions, Inc.
7 */
8 #include <linux/kprobes.h>
9 #include <linux/extable.h>
10 #include <linux/ptrace.h>
11 #include <linux/preempt.h>
12 #include <linux/kdebug.h>
13 #include <linux/slab.h>
14 #include <asm/cacheflush.h>
15 #include <linux/uaccess.h>
16
17 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
18 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
19
20 static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
21 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
22 static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);
23
24 #define OPCODE_JMP(x) (((x) & 0xF0FF) == 0x402b)
25 #define OPCODE_JSR(x) (((x) & 0xF0FF) == 0x400b)
26 #define OPCODE_BRA(x) (((x) & 0xF000) == 0xa000)
27 #define OPCODE_BRAF(x) (((x) & 0xF0FF) == 0x0023)
28 #define OPCODE_BSR(x) (((x) & 0xF000) == 0xb000)
29 #define OPCODE_BSRF(x) (((x) & 0xF0FF) == 0x0003)
30
31 #define OPCODE_BF_S(x) (((x) & 0xFF00) == 0x8f00)
32 #define OPCODE_BT_S(x) (((x) & 0xFF00) == 0x8d00)
33
34 #define OPCODE_BF(x) (((x) & 0xFF00) == 0x8b00)
35 #define OPCODE_BT(x) (((x) & 0xFF00) == 0x8900)
36
37 #define OPCODE_RTS(x) (((x) & 0x000F) == 0x000b)
38 #define OPCODE_RTE(x) (((x) & 0xFFFF) == 0x002b)
39
arch_prepare_kprobe(struct kprobe * p)40 int __kprobes arch_prepare_kprobe(struct kprobe *p)
41 {
42 kprobe_opcode_t opcode = *(kprobe_opcode_t *) (p->addr);
43
44 if (OPCODE_RTE(opcode))
45 return -EFAULT; /* Bad breakpoint */
46
47 p->opcode = opcode;
48
49 return 0;
50 }
51
arch_copy_kprobe(struct kprobe * p)52 void __kprobes arch_copy_kprobe(struct kprobe *p)
53 {
54 memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
55 p->opcode = *p->addr;
56 }
57
arch_arm_kprobe(struct kprobe * p)58 void __kprobes arch_arm_kprobe(struct kprobe *p)
59 {
60 *p->addr = BREAKPOINT_INSTRUCTION;
61 flush_icache_range((unsigned long)p->addr,
62 (unsigned long)p->addr + sizeof(kprobe_opcode_t));
63 }
64
arch_disarm_kprobe(struct kprobe * p)65 void __kprobes arch_disarm_kprobe(struct kprobe *p)
66 {
67 *p->addr = p->opcode;
68 flush_icache_range((unsigned long)p->addr,
69 (unsigned long)p->addr + sizeof(kprobe_opcode_t));
70 }
71
arch_trampoline_kprobe(struct kprobe * p)72 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
73 {
74 if (*p->addr == BREAKPOINT_INSTRUCTION)
75 return 1;
76
77 return 0;
78 }
79
80 /**
81 * If an illegal slot instruction exception occurs for an address
82 * containing a kprobe, remove the probe.
83 *
84 * Returns 0 if the exception was handled successfully, 1 otherwise.
85 */
kprobe_handle_illslot(unsigned long pc)86 int __kprobes kprobe_handle_illslot(unsigned long pc)
87 {
88 struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);
89
90 if (p != NULL) {
91 printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
92 (unsigned int)pc + 2);
93 unregister_kprobe(p);
94 return 0;
95 }
96
97 return 1;
98 }
99
arch_remove_kprobe(struct kprobe * p)100 void __kprobes arch_remove_kprobe(struct kprobe *p)
101 {
102 struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);
103
104 if (saved->addr) {
105 arch_disarm_kprobe(p);
106 arch_disarm_kprobe(saved);
107
108 saved->addr = NULL;
109 saved->opcode = 0;
110
111 saved = this_cpu_ptr(&saved_next_opcode2);
112 if (saved->addr) {
113 arch_disarm_kprobe(saved);
114
115 saved->addr = NULL;
116 saved->opcode = 0;
117 }
118 }
119 }
120
save_previous_kprobe(struct kprobe_ctlblk * kcb)121 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
122 {
123 kcb->prev_kprobe.kp = kprobe_running();
124 kcb->prev_kprobe.status = kcb->kprobe_status;
125 }
126
restore_previous_kprobe(struct kprobe_ctlblk * kcb)127 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
128 {
129 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
130 kcb->kprobe_status = kcb->prev_kprobe.status;
131 }
132
set_current_kprobe(struct kprobe * p,struct pt_regs * regs,struct kprobe_ctlblk * kcb)133 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
134 struct kprobe_ctlblk *kcb)
135 {
136 __this_cpu_write(current_kprobe, p);
137 }
138
139 /*
140 * Singlestep is implemented by disabling the current kprobe and setting one
141 * on the next instruction, following branches. Two probes are set if the
142 * branch is conditional.
143 */
prepare_singlestep(struct kprobe * p,struct pt_regs * regs)144 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
145 {
146 __this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);
147
148 if (p != NULL) {
149 struct kprobe *op1, *op2;
150
151 arch_disarm_kprobe(p);
152
153 op1 = this_cpu_ptr(&saved_next_opcode);
154 op2 = this_cpu_ptr(&saved_next_opcode2);
155
156 if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
157 unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
158 op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
159 } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
160 unsigned long disp = (p->opcode & 0x0FFF);
161 op1->addr =
162 (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
163
164 } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
165 unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
166 op1->addr =
167 (kprobe_opcode_t *) (regs->pc + 4 +
168 regs->regs[reg_nr]);
169
170 } else if (OPCODE_RTS(p->opcode)) {
171 op1->addr = (kprobe_opcode_t *) regs->pr;
172
173 } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
174 unsigned long disp = (p->opcode & 0x00FF);
175 /* case 1 */
176 op1->addr = p->addr + 1;
177 /* case 2 */
178 op2->addr =
179 (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
180 op2->opcode = *(op2->addr);
181 arch_arm_kprobe(op2);
182
183 } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
184 unsigned long disp = (p->opcode & 0x00FF);
185 /* case 1 */
186 op1->addr = p->addr + 2;
187 /* case 2 */
188 op2->addr =
189 (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
190 op2->opcode = *(op2->addr);
191 arch_arm_kprobe(op2);
192
193 } else {
194 op1->addr = p->addr + 1;
195 }
196
197 op1->opcode = *(op1->addr);
198 arch_arm_kprobe(op1);
199 }
200 }
201
202 /* Called with kretprobe_lock held */
arch_prepare_kretprobe(struct kretprobe_instance * ri,struct pt_regs * regs)203 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
204 struct pt_regs *regs)
205 {
206 ri->ret_addr = (kprobe_opcode_t *) regs->pr;
207 ri->fp = NULL;
208
209 /* Replace the return addr with trampoline addr */
210 regs->pr = (unsigned long)kretprobe_trampoline;
211 }
212
kprobe_handler(struct pt_regs * regs)213 static int __kprobes kprobe_handler(struct pt_regs *regs)
214 {
215 struct kprobe *p;
216 int ret = 0;
217 kprobe_opcode_t *addr = NULL;
218 struct kprobe_ctlblk *kcb;
219
220 /*
221 * We don't want to be preempted for the entire
222 * duration of kprobe processing
223 */
224 preempt_disable();
225 kcb = get_kprobe_ctlblk();
226
227 addr = (kprobe_opcode_t *) (regs->pc);
228
229 /* Check we're not actually recursing */
230 if (kprobe_running()) {
231 p = get_kprobe(addr);
232 if (p) {
233 if (kcb->kprobe_status == KPROBE_HIT_SS &&
234 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
235 goto no_kprobe;
236 }
237 /* We have reentered the kprobe_handler(), since
238 * another probe was hit while within the handler.
239 * We here save the original kprobes variables and
240 * just single step on the instruction of the new probe
241 * without calling any user handlers.
242 */
243 save_previous_kprobe(kcb);
244 set_current_kprobe(p, regs, kcb);
245 kprobes_inc_nmissed_count(p);
246 prepare_singlestep(p, regs);
247 kcb->kprobe_status = KPROBE_REENTER;
248 return 1;
249 }
250 goto no_kprobe;
251 }
252
253 p = get_kprobe(addr);
254 if (!p) {
255 /* Not one of ours: let kernel handle it */
256 if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
257 /*
258 * The breakpoint instruction was removed right
259 * after we hit it. Another cpu has removed
260 * either a probepoint or a debugger breakpoint
261 * at this address. In either case, no further
262 * handling of this interrupt is appropriate.
263 */
264 ret = 1;
265 }
266
267 goto no_kprobe;
268 }
269
270 set_current_kprobe(p, regs, kcb);
271 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
272
273 if (p->pre_handler && p->pre_handler(p, regs)) {
274 /* handler has already set things up, so skip ss setup */
275 reset_current_kprobe();
276 preempt_enable_no_resched();
277 return 1;
278 }
279
280 prepare_singlestep(p, regs);
281 kcb->kprobe_status = KPROBE_HIT_SS;
282 return 1;
283
284 no_kprobe:
285 preempt_enable_no_resched();
286 return ret;
287 }
288
289 /*
290 * For function-return probes, init_kprobes() establishes a probepoint
291 * here. When a retprobed function returns, this probe is hit and
292 * trampoline_probe_handler() runs, calling the kretprobe's handler.
293 */
kretprobe_trampoline_holder(void)294 static void __used kretprobe_trampoline_holder(void)
295 {
296 asm volatile (".globl kretprobe_trampoline\n"
297 "kretprobe_trampoline:\n\t"
298 "nop\n");
299 }
300
301 /*
302 * Called when we hit the probe point at kretprobe_trampoline
303 */
trampoline_probe_handler(struct kprobe * p,struct pt_regs * regs)304 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
305 {
306 regs->pc = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
307
308 return 1;
309 }
310
post_kprobe_handler(struct pt_regs * regs)311 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
312 {
313 struct kprobe *cur = kprobe_running();
314 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
315 kprobe_opcode_t *addr = NULL;
316 struct kprobe *p = NULL;
317
318 if (!cur)
319 return 0;
320
321 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
322 kcb->kprobe_status = KPROBE_HIT_SSDONE;
323 cur->post_handler(cur, regs, 0);
324 }
325
326 p = this_cpu_ptr(&saved_next_opcode);
327 if (p->addr) {
328 arch_disarm_kprobe(p);
329 p->addr = NULL;
330 p->opcode = 0;
331
332 addr = __this_cpu_read(saved_current_opcode.addr);
333 __this_cpu_write(saved_current_opcode.addr, NULL);
334
335 p = get_kprobe(addr);
336 arch_arm_kprobe(p);
337
338 p = this_cpu_ptr(&saved_next_opcode2);
339 if (p->addr) {
340 arch_disarm_kprobe(p);
341 p->addr = NULL;
342 p->opcode = 0;
343 }
344 }
345
346 /* Restore back the original saved kprobes variables and continue. */
347 if (kcb->kprobe_status == KPROBE_REENTER) {
348 restore_previous_kprobe(kcb);
349 goto out;
350 }
351
352 reset_current_kprobe();
353
354 out:
355 preempt_enable_no_resched();
356
357 return 1;
358 }
359
kprobe_fault_handler(struct pt_regs * regs,int trapnr)360 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
361 {
362 struct kprobe *cur = kprobe_running();
363 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
364 const struct exception_table_entry *entry;
365
366 switch (kcb->kprobe_status) {
367 case KPROBE_HIT_SS:
368 case KPROBE_REENTER:
369 /*
370 * We are here because the instruction being single
371 * stepped caused a page fault. We reset the current
372 * kprobe, point the pc back to the probe address
373 * and allow the page fault handler to continue as a
374 * normal page fault.
375 */
376 regs->pc = (unsigned long)cur->addr;
377 if (kcb->kprobe_status == KPROBE_REENTER)
378 restore_previous_kprobe(kcb);
379 else
380 reset_current_kprobe();
381 preempt_enable_no_resched();
382 break;
383 case KPROBE_HIT_ACTIVE:
384 case KPROBE_HIT_SSDONE:
385 /*
386 * We increment the nmissed count for accounting,
387 * we can also use npre/npostfault count for accounting
388 * these specific fault cases.
389 */
390 kprobes_inc_nmissed_count(cur);
391
392 /*
393 * We come here because instructions in the pre/post
394 * handler caused the page_fault, this could happen
395 * if handler tries to access user space by
396 * copy_from_user(), get_user() etc. Let the
397 * user-specified handler try to fix it first.
398 */
399 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
400 return 1;
401
402 /*
403 * In case the user-specified fault handler returned
404 * zero, try to fix up.
405 */
406 if ((entry = search_exception_tables(regs->pc)) != NULL) {
407 regs->pc = entry->fixup;
408 return 1;
409 }
410
411 /*
412 * fixup_exception() could not handle it,
413 * Let do_page_fault() fix it.
414 */
415 break;
416 default:
417 break;
418 }
419
420 return 0;
421 }
422
423 /*
424 * Wrapper routine to for handling exceptions.
425 */
kprobe_exceptions_notify(struct notifier_block * self,unsigned long val,void * data)426 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
427 unsigned long val, void *data)
428 {
429 struct kprobe *p = NULL;
430 struct die_args *args = (struct die_args *)data;
431 int ret = NOTIFY_DONE;
432 kprobe_opcode_t *addr = NULL;
433 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
434
435 addr = (kprobe_opcode_t *) (args->regs->pc);
436 if (val == DIE_TRAP &&
437 args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
438 if (!kprobe_running()) {
439 if (kprobe_handler(args->regs)) {
440 ret = NOTIFY_STOP;
441 } else {
442 /* Not a kprobe trap */
443 ret = NOTIFY_DONE;
444 }
445 } else {
446 p = get_kprobe(addr);
447 if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
448 (kcb->kprobe_status == KPROBE_REENTER)) {
449 if (post_kprobe_handler(args->regs))
450 ret = NOTIFY_STOP;
451 } else {
452 if (kprobe_handler(args->regs))
453 ret = NOTIFY_STOP;
454 }
455 }
456 }
457
458 return ret;
459 }
460
461 static struct kprobe trampoline_p = {
462 .addr = (kprobe_opcode_t *)&kretprobe_trampoline,
463 .pre_handler = trampoline_probe_handler
464 };
465
arch_init_kprobes(void)466 int __init arch_init_kprobes(void)
467 {
468 return register_kprobe(&trampoline_p);
469 }
470
