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
17DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
18DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
19
20static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
21static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
22static 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
40int __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
52void __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
58void __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
65void __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
72int __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 */
86int __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
100void __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
121static 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
127static 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
133static 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 */
144static 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 */
203void __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
213static 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
284no_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 */
294static 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 */
304int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
305{
306	regs->pc = __kretprobe_trampoline_handler(regs, NULL);
307
308	return 1;
309}
310
311static 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
354out:
355	preempt_enable_no_resched();
356
357	return 1;
358}
359
360int __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		 * In case the user-specified fault handler returned
387		 * zero, try to fix up.
388		 */
389		if ((entry = search_exception_tables(regs->pc)) != NULL) {
390			regs->pc = entry->fixup;
391			return 1;
392		}
393
394		/*
395		 * fixup_exception() could not handle it,
396		 * Let do_page_fault() fix it.
397		 */
398		break;
399	default:
400		break;
401	}
402
403	return 0;
404}
405
406/*
407 * Wrapper routine to for handling exceptions.
408 */
409int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
410				       unsigned long val, void *data)
411{
412	struct kprobe *p = NULL;
413	struct die_args *args = (struct die_args *)data;
414	int ret = NOTIFY_DONE;
415	kprobe_opcode_t *addr = NULL;
416	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
417
418	addr = (kprobe_opcode_t *) (args->regs->pc);
419	if (val == DIE_TRAP &&
420	    args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
421		if (!kprobe_running()) {
422			if (kprobe_handler(args->regs)) {
423				ret = NOTIFY_STOP;
424			} else {
425				/* Not a kprobe trap */
426				ret = NOTIFY_DONE;
427			}
428		} else {
429			p = get_kprobe(addr);
430			if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
431			    (kcb->kprobe_status == KPROBE_REENTER)) {
432				if (post_kprobe_handler(args->regs))
433					ret = NOTIFY_STOP;
434			} else {
435				if (kprobe_handler(args->regs))
436					ret = NOTIFY_STOP;
437			}
438		}
439	}
440
441	return ret;
442}
443
444static struct kprobe trampoline_p = {
445	.addr = (kprobe_opcode_t *)&__kretprobe_trampoline,
446	.pre_handler = trampoline_probe_handler
447};
448
449int __init arch_init_kprobes(void)
450{
451	return register_kprobe(&trampoline_p);
452}
453