1 // SPDX-License-Identifier: GPL-2.0
2 /* arch/sparc64/kernel/kprobes.c
3 *
4 * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
5 */
6
7 #include <linux/kernel.h>
8 #include <linux/kprobes.h>
9 #include <linux/extable.h>
10 #include <linux/kdebug.h>
11 #include <linux/slab.h>
12 #include <linux/context_tracking.h>
13 #include <asm/signal.h>
14 #include <asm/cacheflush.h>
15 #include <linux/uaccess.h>
16
17 /* We do not have hardware single-stepping on sparc64.
18 * So we implement software single-stepping with breakpoint
19 * traps. The top-level scheme is similar to that used
20 * in the x86 kprobes implementation.
21 *
22 * In the kprobe->ainsn.insn[] array we store the original
23 * instruction at index zero and a break instruction at
24 * index one.
25 *
26 * When we hit a kprobe we:
27 * - Run the pre-handler
28 * - Remember "regs->tnpc" and interrupt level stored in
29 * "regs->tstate" so we can restore them later
30 * - Disable PIL interrupts
31 * - Set regs->tpc to point to kprobe->ainsn.insn[0]
32 * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
33 * - Mark that we are actively in a kprobe
34 *
35 * At this point we wait for the second breakpoint at
36 * kprobe->ainsn.insn[1] to hit. When it does we:
37 * - Run the post-handler
38 * - Set regs->tpc to "remembered" regs->tnpc stored above,
39 * restore the PIL interrupt level in "regs->tstate" as well
40 * - Make any adjustments necessary to regs->tnpc in order
41 * to handle relative branches correctly. See below.
42 * - Mark that we are no longer actively in a kprobe.
43 */
44
45 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
46 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
47
48 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
49
50 int __kprobes arch_prepare_kprobe(struct kprobe *p)
51 {
52 if ((unsigned long) p->addr & 0x3UL)
53 return -EILSEQ;
54
55 p->ainsn.insn[0] = *p->addr;
56 flushi(&p->ainsn.insn[0]);
57
58 p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
59 flushi(&p->ainsn.insn[1]);
60
61 p->opcode = *p->addr;
62 return 0;
63 }
64
65 void __kprobes arch_arm_kprobe(struct kprobe *p)
66 {
67 *p->addr = BREAKPOINT_INSTRUCTION;
68 flushi(p->addr);
69 }
70
71 void __kprobes arch_disarm_kprobe(struct kprobe *p)
72 {
73 *p->addr = p->opcode;
74 flushi(p->addr);
75 }
76
77 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
78 {
79 kcb->prev_kprobe.kp = kprobe_running();
80 kcb->prev_kprobe.status = kcb->kprobe_status;
81 kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
82 kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
83 }
84
85 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
86 {
87 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
88 kcb->kprobe_status = kcb->prev_kprobe.status;
89 kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
90 kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
91 }
92
93 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
94 struct kprobe_ctlblk *kcb)
95 {
96 __this_cpu_write(current_kprobe, p);
97 kcb->kprobe_orig_tnpc = regs->tnpc;
98 kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
99 }
100
101 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
102 struct kprobe_ctlblk *kcb)
103 {
104 regs->tstate |= TSTATE_PIL;
105
106 /*single step inline, if it a breakpoint instruction*/
107 if (p->opcode == BREAKPOINT_INSTRUCTION) {
108 regs->tpc = (unsigned long) p->addr;
109 regs->tnpc = kcb->kprobe_orig_tnpc;
110 } else {
111 regs->tpc = (unsigned long) &p->ainsn.insn[0];
112 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
113 }
114 }
115
116 static int __kprobes kprobe_handler(struct pt_regs *regs)
117 {
118 struct kprobe *p;
119 void *addr = (void *) regs->tpc;
120 int ret = 0;
121 struct kprobe_ctlblk *kcb;
122
123 /*
124 * We don't want to be preempted for the entire
125 * duration of kprobe processing
126 */
127 preempt_disable();
128 kcb = get_kprobe_ctlblk();
129
130 if (kprobe_running()) {
131 p = get_kprobe(addr);
132 if (p) {
133 if (kcb->kprobe_status == KPROBE_HIT_SS) {
134 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
135 kcb->kprobe_orig_tstate_pil);
136 goto no_kprobe;
137 }
138 /* We have reentered the kprobe_handler(), since
139 * another probe was hit while within the handler.
140 * We here save the original kprobes variables and
141 * just single step on the instruction of the new probe
142 * without calling any user handlers.
143 */
144 save_previous_kprobe(kcb);
145 set_current_kprobe(p, regs, kcb);
146 kprobes_inc_nmissed_count(p);
147 kcb->kprobe_status = KPROBE_REENTER;
148 prepare_singlestep(p, regs, kcb);
149 return 1;
150 } else if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
151 /* The breakpoint instruction was removed by
152 * another cpu right after we hit, no further
153 * handling of this interrupt is appropriate
154 */
155 ret = 1;
156 }
157 goto no_kprobe;
158 }
159
160 p = get_kprobe(addr);
161 if (!p) {
162 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
163 /*
164 * The breakpoint instruction was removed right
165 * after we hit it. Another cpu has removed
166 * either a probepoint or a debugger breakpoint
167 * at this address. In either case, no further
168 * handling of this interrupt is appropriate.
169 */
170 ret = 1;
171 }
172 /* Not one of ours: let kernel handle it */
173 goto no_kprobe;
174 }
175
176 set_current_kprobe(p, regs, kcb);
177 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
178 if (p->pre_handler && p->pre_handler(p, regs)) {
179 reset_current_kprobe();
180 preempt_enable_no_resched();
181 return 1;
182 }
183
184 prepare_singlestep(p, regs, kcb);
185 kcb->kprobe_status = KPROBE_HIT_SS;
186 return 1;
187
188 no_kprobe:
189 preempt_enable_no_resched();
190 return ret;
191 }
192
193 /* If INSN is a relative control transfer instruction,
194 * return the corrected branch destination value.
195 *
196 * regs->tpc and regs->tnpc still hold the values of the
197 * program counters at the time of trap due to the execution
198 * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
199 *
200 */
201 static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
202 struct pt_regs *regs)
203 {
204 unsigned long real_pc = (unsigned long) p->addr;
205
206 /* Branch not taken, no mods necessary. */
207 if (regs->tnpc == regs->tpc + 0x4UL)
208 return real_pc + 0x8UL;
209
210 /* The three cases are call, branch w/prediction,
211 * and traditional branch.
212 */
213 if ((insn & 0xc0000000) == 0x40000000 ||
214 (insn & 0xc1c00000) == 0x00400000 ||
215 (insn & 0xc1c00000) == 0x00800000) {
216 unsigned long ainsn_addr;
217
218 ainsn_addr = (unsigned long) &p->ainsn.insn[0];
219
220 /* The instruction did all the work for us
221 * already, just apply the offset to the correct
222 * instruction location.
223 */
224 return (real_pc + (regs->tnpc - ainsn_addr));
225 }
226
227 /* It is jmpl or some other absolute PC modification instruction,
228 * leave NPC as-is.
229 */
230 return regs->tnpc;
231 }
232
233 /* If INSN is an instruction which writes its PC location
234 * into a destination register, fix that up.
235 */
236 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
237 unsigned long real_pc)
238 {
239 unsigned long *slot = NULL;
240
241 /* Simplest case is 'call', which always uses %o7 */
242 if ((insn & 0xc0000000) == 0x40000000) {
243 slot = ®s->u_regs[UREG_I7];
244 }
245
246 /* 'jmpl' encodes the register inside of the opcode */
247 if ((insn & 0xc1f80000) == 0x81c00000) {
248 unsigned long rd = ((insn >> 25) & 0x1f);
249
250 if (rd <= 15) {
251 slot = ®s->u_regs[rd];
252 } else {
253 /* Hard case, it goes onto the stack. */
254 flushw_all();
255
256 rd -= 16;
257 slot = (unsigned long *)
258 (regs->u_regs[UREG_FP] + STACK_BIAS);
259 slot += rd;
260 }
261 }
262 if (slot != NULL)
263 *slot = real_pc;
264 }
265
266 /*
267 * Called after single-stepping. p->addr is the address of the
268 * instruction which has been replaced by the breakpoint
269 * instruction. To avoid the SMP problems that can occur when we
270 * temporarily put back the original opcode to single-step, we
271 * single-stepped a copy of the instruction. The address of this
272 * copy is &p->ainsn.insn[0].
273 *
274 * This function prepares to return from the post-single-step
275 * breakpoint trap.
276 */
277 static void __kprobes resume_execution(struct kprobe *p,
278 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
279 {
280 u32 insn = p->ainsn.insn[0];
281
282 regs->tnpc = relbranch_fixup(insn, p, regs);
283
284 /* This assignment must occur after relbranch_fixup() */
285 regs->tpc = kcb->kprobe_orig_tnpc;
286
287 retpc_fixup(regs, insn, (unsigned long) p->addr);
288
289 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
290 kcb->kprobe_orig_tstate_pil);
291 }
292
293 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
294 {
295 struct kprobe *cur = kprobe_running();
296 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
297
298 if (!cur)
299 return 0;
300
301 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
302 kcb->kprobe_status = KPROBE_HIT_SSDONE;
303 cur->post_handler(cur, regs, 0);
304 }
305
306 resume_execution(cur, regs, kcb);
307
308 /*Restore back the original saved kprobes variables and continue. */
309 if (kcb->kprobe_status == KPROBE_REENTER) {
310 restore_previous_kprobe(kcb);
311 goto out;
312 }
313 reset_current_kprobe();
314 out:
315 preempt_enable_no_resched();
316
317 return 1;
318 }
319
320 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
321 {
322 struct kprobe *cur = kprobe_running();
323 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
324 const struct exception_table_entry *entry;
325
326 switch(kcb->kprobe_status) {
327 case KPROBE_HIT_SS:
328 case KPROBE_REENTER:
329 /*
330 * We are here because the instruction being single
331 * stepped caused a page fault. We reset the current
332 * kprobe and the tpc points back to the probe address
333 * and allow the page fault handler to continue as a
334 * normal page fault.
335 */
336 regs->tpc = (unsigned long)cur->addr;
337 regs->tnpc = kcb->kprobe_orig_tnpc;
338 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
339 kcb->kprobe_orig_tstate_pil);
340 if (kcb->kprobe_status == KPROBE_REENTER)
341 restore_previous_kprobe(kcb);
342 else
343 reset_current_kprobe();
344 preempt_enable_no_resched();
345 break;
346 case KPROBE_HIT_ACTIVE:
347 case KPROBE_HIT_SSDONE:
348 /*
349 * In case the user-specified fault handler returned
350 * zero, try to fix up.
351 */
352
353 entry = search_exception_tables(regs->tpc);
354 if (entry) {
355 regs->tpc = entry->fixup;
356 regs->tnpc = regs->tpc + 4;
357 return 1;
358 }
359
360 /*
361 * fixup_exception() could not handle it,
362 * Let do_page_fault() fix it.
363 */
364 break;
365 default:
366 break;
367 }
368
369 return 0;
370 }
371
372 /*
373 * Wrapper routine to for handling exceptions.
374 */
375 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
376 unsigned long val, void *data)
377 {
378 struct die_args *args = (struct die_args *)data;
379 int ret = NOTIFY_DONE;
380
381 if (args->regs && user_mode(args->regs))
382 return ret;
383
384 switch (val) {
385 case DIE_DEBUG:
386 if (kprobe_handler(args->regs))
387 ret = NOTIFY_STOP;
388 break;
389 case DIE_DEBUG_2:
390 if (post_kprobe_handler(args->regs))
391 ret = NOTIFY_STOP;
392 break;
393 default:
394 break;
395 }
396 return ret;
397 }
398
399 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
400 struct pt_regs *regs)
401 {
402 enum ctx_state prev_state = exception_enter();
403
404 BUG_ON(trap_level != 0x170 && trap_level != 0x171);
405
406 if (user_mode(regs)) {
407 local_irq_enable();
408 bad_trap(regs, trap_level);
409 goto out;
410 }
411
412 /* trap_level == 0x170 --> ta 0x70
413 * trap_level == 0x171 --> ta 0x71
414 */
415 if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
416 (trap_level == 0x170) ? "debug" : "debug_2",
417 regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
418 bad_trap(regs, trap_level);
419 out:
420 exception_exit(prev_state);
421 }
422
423 /* The value stored in the return address register is actually 2
424 * instructions before where the callee will return to.
425 * Sequences usually look something like this
426 *
427 * call some_function <--- return register points here
428 * nop <--- call delay slot
429 * whatever <--- where callee returns to
430 *
431 * To keep trampoline_probe_handler logic simpler, we normalize the
432 * value kept in ri->ret_addr so we don't need to keep adjusting it
433 * back and forth.
434 */
435 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
436 struct pt_regs *regs)
437 {
438 ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8);
439 ri->fp = NULL;
440
441 /* Replace the return addr with trampoline addr */
442 regs->u_regs[UREG_RETPC] =
443 ((unsigned long)__kretprobe_trampoline) - 8;
444 }
445
446 /*
447 * Called when the probe at kretprobe trampoline is hit
448 */
449 static int __kprobes trampoline_probe_handler(struct kprobe *p,
450 struct pt_regs *regs)
451 {
452 unsigned long orig_ret_address = 0;
453
454 orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
455 regs->tpc = orig_ret_address;
456 regs->tnpc = orig_ret_address + 4;
457
458 /*
459 * By returning a non-zero value, we are telling
460 * kprobe_handler() that we don't want the post_handler
461 * to run (and have re-enabled preemption)
462 */
463 return 1;
464 }
465
466 static void __used kretprobe_trampoline_holder(void)
467 {
468 asm volatile(".global __kretprobe_trampoline\n"
469 "__kretprobe_trampoline:\n"
470 "\tnop\n"
471 "\tnop\n");
472 }
473 static struct kprobe trampoline_p = {
474 .addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
475 .pre_handler = trampoline_probe_handler
476 };
477
478 int __init arch_init_kprobes(void)
479 {
480 return register_kprobe(&trampoline_p);
481 }
482
483 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
484 {
485 if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
486 return 1;
487
488 return 0;
489 }
490
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