xref: /openbmc/linux/arch/sh/kernel/kprobes.c (revision d9fd5a71) 
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 
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 
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 
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 
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 
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  */
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 
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 
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 
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 
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  */
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 */
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 
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  */
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  */
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 
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 
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  */
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 
466 int __init arch_init_kprobes(void)
467 {
468 	return register_kprobe(&trampoline_p);
469 }
470