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