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1/*
2 * arch/tile/kernel/kprobes.c
3 * Kprobes on TILE-Gx
4 *
5 * Some portions copied from the MIPS version.
6 *
7 * Copyright (C) IBM Corporation, 2002, 2004
8 * Copyright 2006 Sony Corp.
9 * Copyright 2010 Cavium Networks
10 *
11 * Copyright 2012 Tilera Corporation. All Rights Reserved.
12 *
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation, version 2.
16 *
17 * This program is distributed in the hope that it will be useful, but
18 * WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
20 * NON INFRINGEMENT. See the GNU General Public License for
21 * more details.
22 */
23
24#include <linux/kprobes.h>
25#include <linux/kdebug.h>
26#include <linux/module.h>
27#include <linux/slab.h>
28#include <linux/uaccess.h>
29#include <asm/cacheflush.h>
30
31#include <arch/opcode.h>
32
33DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
34DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
35
36tile_bundle_bits breakpoint_insn = TILEGX_BPT_BUNDLE;
37tile_bundle_bits breakpoint2_insn = TILEGX_BPT_BUNDLE | DIE_SSTEPBP;
38
39/*
40 * Check whether instruction is branch or jump, or if executing it
41 * has different results depending on where it is executed (e.g. lnk).
42 */
43static int __kprobes insn_has_control(kprobe_opcode_t insn)
44{
45 if (get_Mode(insn) != 0) { /* Y-format bundle */
46 if (get_Opcode_Y1(insn) != RRR_1_OPCODE_Y1 ||
47 get_RRROpcodeExtension_Y1(insn) != UNARY_RRR_1_OPCODE_Y1)
48 return 0;
49
50 switch (get_UnaryOpcodeExtension_Y1(insn)) {
51 case JALRP_UNARY_OPCODE_Y1:
52 case JALR_UNARY_OPCODE_Y1:
53 case JRP_UNARY_OPCODE_Y1:
54 case JR_UNARY_OPCODE_Y1:
55 case LNK_UNARY_OPCODE_Y1:
56 return 1;
57 default:
58 return 0;
59 }
60 }
61
62 switch (get_Opcode_X1(insn)) {
63 case BRANCH_OPCODE_X1: /* branch instructions */
64 case JUMP_OPCODE_X1: /* jump instructions: j and jal */
65 return 1;
66
67 case RRR_0_OPCODE_X1: /* other jump instructions */
68 if (get_RRROpcodeExtension_X1(insn) != UNARY_RRR_0_OPCODE_X1)
69 return 0;
70 switch (get_UnaryOpcodeExtension_X1(insn)) {
71 case JALRP_UNARY_OPCODE_X1:
72 case JALR_UNARY_OPCODE_X1:
73 case JRP_UNARY_OPCODE_X1:
74 case JR_UNARY_OPCODE_X1:
75 case LNK_UNARY_OPCODE_X1:
76 return 1;
77 default:
78 return 0;
79 }
80 default:
81 return 0;
82 }
83}
84
85int __kprobes arch_prepare_kprobe(struct kprobe *p)
86{
87 unsigned long addr = (unsigned long)p->addr;
88
89 if (addr & (sizeof(kprobe_opcode_t) - 1))
90 return -EINVAL;
91
92 if (insn_has_control(*p->addr)) {
93 pr_notice("Kprobes for control instructions are not "
94 "supported\n");
95 return -EINVAL;
96 }
97
98 /* insn: must be on special executable page on tile. */
99 p->ainsn.insn = get_insn_slot();
100 if (!p->ainsn.insn)
101 return -ENOMEM;
102
103 /*
104 * In the kprobe->ainsn.insn[] array we store the original
105 * instruction at index zero and a break trap instruction at
106 * index one.
107 */
108 memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
109 p->ainsn.insn[1] = breakpoint2_insn;
110 p->opcode = *p->addr;
111
112 return 0;
113}
114
115void __kprobes arch_arm_kprobe(struct kprobe *p)
116{
117 unsigned long addr_wr;
118
119 /* Operate on writable kernel text mapping. */
120 addr_wr = (unsigned long)p->addr - MEM_SV_START + PAGE_OFFSET;
121
122 if (probe_kernel_write((void *)addr_wr, &breakpoint_insn,
123 sizeof(breakpoint_insn)))
124 pr_err("%s: failed to enable kprobe\n", __func__);
125
126 smp_wmb();
127 flush_insn_slot(p);
128}
129
130void __kprobes arch_disarm_kprobe(struct kprobe *kp)
131{
132 unsigned long addr_wr;
133
134 /* Operate on writable kernel text mapping. */
135 addr_wr = (unsigned long)kp->addr - MEM_SV_START + PAGE_OFFSET;
136
137 if (probe_kernel_write((void *)addr_wr, &kp->opcode,
138 sizeof(kp->opcode)))
139 pr_err("%s: failed to enable kprobe\n", __func__);
140
141 smp_wmb();
142 flush_insn_slot(kp);
143}
144
145void __kprobes arch_remove_kprobe(struct kprobe *p)
146{
147 if (p->ainsn.insn) {
148 free_insn_slot(p->ainsn.insn, 0);
149 p->ainsn.insn = NULL;
150 }
151}
152
153static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
154{
155 kcb->prev_kprobe.kp = kprobe_running();
156 kcb->prev_kprobe.status = kcb->kprobe_status;
157 kcb->prev_kprobe.saved_pc = kcb->kprobe_saved_pc;
158}
159
160static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
161{
162 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
163 kcb->kprobe_status = kcb->prev_kprobe.status;
164 kcb->kprobe_saved_pc = kcb->prev_kprobe.saved_pc;
165}
166
167static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
168 struct kprobe_ctlblk *kcb)
169{
170 __this_cpu_write(current_kprobe, p);
171 kcb->kprobe_saved_pc = regs->pc;
172}
173
174static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
175{
176 /* Single step inline if the instruction is a break. */
177 if (p->opcode == breakpoint_insn ||
178 p->opcode == breakpoint2_insn)
179 regs->pc = (unsigned long)p->addr;
180 else
181 regs->pc = (unsigned long)&p->ainsn.insn[0];
182}
183
184static int __kprobes kprobe_handler(struct pt_regs *regs)
185{
186 struct kprobe *p;
187 int ret = 0;
188 kprobe_opcode_t *addr;
189 struct kprobe_ctlblk *kcb;
190
191 addr = (kprobe_opcode_t *)regs->pc;
192
193 /*
194 * We don't want to be preempted for the entire
195 * duration of kprobe processing.
196 */
197 preempt_disable();
198 kcb = get_kprobe_ctlblk();
199
200 /* Check we're not actually recursing. */
201 if (kprobe_running()) {
202 p = get_kprobe(addr);
203 if (p) {
204 if (kcb->kprobe_status == KPROBE_HIT_SS &&
205 p->ainsn.insn[0] == breakpoint_insn) {
206 goto no_kprobe;
207 }
208 /*
209 * We have reentered the kprobe_handler(), since
210 * another probe was hit while within the handler.
211 * We here save the original kprobes variables and
212 * just single step on the instruction of the new probe
213 * without calling any user handlers.
214 */
215 save_previous_kprobe(kcb);
216 set_current_kprobe(p, regs, kcb);
217 kprobes_inc_nmissed_count(p);
218 prepare_singlestep(p, regs);
219 kcb->kprobe_status = KPROBE_REENTER;
220 return 1;
221 } else {
222 if (*addr != breakpoint_insn) {
223 /*
224 * The breakpoint instruction was removed by
225 * another cpu right after we hit, no further
226 * handling of this interrupt is appropriate.
227 */
228 ret = 1;
229 goto no_kprobe;
230 }
231 p = __this_cpu_read(current_kprobe);
232 if (p->break_handler && p->break_handler(p, regs))
233 goto ss_probe;
234 }
235 goto no_kprobe;
236 }
237
238 p = get_kprobe(addr);
239 if (!p) {
240 if (*addr != breakpoint_insn) {
241 /*
242 * The breakpoint instruction was removed right
243 * after we hit it. Another cpu has removed
244 * either a probepoint or a debugger breakpoint
245 * at this address. In either case, no further
246 * handling of this interrupt is appropriate.
247 */
248 ret = 1;
249 }
250 /* Not one of ours: let kernel handle it. */
251 goto no_kprobe;
252 }
253
254 set_current_kprobe(p, regs, kcb);
255 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
256
257 if (p->pre_handler && p->pre_handler(p, regs)) {
258 /* Handler has already set things up, so skip ss setup. */
259 return 1;
260 }
261
262ss_probe:
263 prepare_singlestep(p, regs);
264 kcb->kprobe_status = KPROBE_HIT_SS;
265 return 1;
266
267no_kprobe:
268 preempt_enable_no_resched();
269 return ret;
270}
271
272/*
273 * Called after single-stepping. p->addr is the address of the
274 * instruction that has been replaced by the breakpoint. To avoid the
275 * SMP problems that can occur when we temporarily put back the
276 * original opcode to single-step, we single-stepped a copy of the
277 * instruction. The address of this copy is p->ainsn.insn.
278 *
279 * This function prepares to return from the post-single-step
280 * breakpoint trap.
281 */
282static void __kprobes resume_execution(struct kprobe *p,
283 struct pt_regs *regs,
284 struct kprobe_ctlblk *kcb)
285{
286 unsigned long orig_pc = kcb->kprobe_saved_pc;
287 regs->pc = orig_pc + 8;
288}
289
290static inline int post_kprobe_handler(struct pt_regs *regs)
291{
292 struct kprobe *cur = kprobe_running();
293 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
294
295 if (!cur)
296 return 0;
297
298 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
299 kcb->kprobe_status = KPROBE_HIT_SSDONE;
300 cur->post_handler(cur, regs, 0);
301 }
302
303 resume_execution(cur, regs, kcb);
304
305 /* Restore back the original saved kprobes variables and continue. */
306 if (kcb->kprobe_status == KPROBE_REENTER) {
307 restore_previous_kprobe(kcb);
308 goto out;
309 }
310 reset_current_kprobe();
311out:
312 preempt_enable_no_resched();
313
314 return 1;
315}
316
317static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
318{
319 struct kprobe *cur = kprobe_running();
320 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
321
322 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
323 return 1;
324
325 if (kcb->kprobe_status & KPROBE_HIT_SS) {
326 /*
327 * We are here because the instruction being single
328 * stepped caused a page fault. We reset the current
329 * kprobe and the ip points back to the probe address
330 * and allow the page fault handler to continue as a
331 * normal page fault.
332 */
333 resume_execution(cur, regs, kcb);
334 reset_current_kprobe();
335 preempt_enable_no_resched();
336 }
337 return 0;
338}
339
340/*
341 * Wrapper routine for handling exceptions.
342 */
343int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
344 unsigned long val, void *data)
345{
346 struct die_args *args = (struct die_args *)data;
347 int ret = NOTIFY_DONE;
348
349 switch (val) {
350 case DIE_BREAK:
351 if (kprobe_handler(args->regs))
352 ret = NOTIFY_STOP;
353 break;
354 case DIE_SSTEPBP:
355 if (post_kprobe_handler(args->regs))
356 ret = NOTIFY_STOP;
357 break;
358 case DIE_PAGE_FAULT:
359 /* kprobe_running() needs smp_processor_id(). */
360 preempt_disable();
361
362 if (kprobe_running()
363 && kprobe_fault_handler(args->regs, args->trapnr))
364 ret = NOTIFY_STOP;
365 preempt_enable();
366 break;
367 default:
368 break;
369 }
370 return ret;
371}
372
373int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
374{
375 struct jprobe *jp = container_of(p, struct jprobe, kp);
376 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
377
378 kcb->jprobe_saved_regs = *regs;
379 kcb->jprobe_saved_sp = regs->sp;
380
381 memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
382 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
383
384 regs->pc = (unsigned long)(jp->entry);
385
386 return 1;
387}
388
389/* Defined in the inline asm below. */
390void jprobe_return_end(void);
391
392void __kprobes jprobe_return(void)
393{
394 asm volatile(
395 "bpt\n\t"
396 ".globl jprobe_return_end\n"
397 "jprobe_return_end:\n");
398}
399
400int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
401{
402 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
403
404 if (regs->pc >= (unsigned long)jprobe_return &&
405 regs->pc <= (unsigned long)jprobe_return_end) {
406 *regs = kcb->jprobe_saved_regs;
407 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
408 MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
409 preempt_enable_no_resched();
410
411 return 1;
412 }
413 return 0;
414}
415
416/*
417 * Function return probe trampoline:
418 * - init_kprobes() establishes a probepoint here
419 * - When the probed function returns, this probe causes the
420 * handlers to fire
421 */
422static void __used kretprobe_trampoline_holder(void)
423{
424 asm volatile(
425 "nop\n\t"
426 ".global kretprobe_trampoline\n"
427 "kretprobe_trampoline:\n\t"
428 "nop\n\t"
429 : : : "memory");
430}
431
432void kretprobe_trampoline(void);
433
434void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
435 struct pt_regs *regs)
436{
437 ri->ret_addr = (kprobe_opcode_t *) regs->lr;
438
439 /* Replace the return addr with trampoline addr */
440 regs->lr = (unsigned long)kretprobe_trampoline;
441}
442
443/*
444 * Called when the probe at kretprobe trampoline is hit.
445 */
446static int __kprobes trampoline_probe_handler(struct kprobe *p,
447 struct pt_regs *regs)
448{
449 struct kretprobe_instance *ri = NULL;
450 struct hlist_head *head, empty_rp;
451 struct hlist_node *tmp;
452 unsigned long flags, orig_ret_address = 0;
453 unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
454
455 INIT_HLIST_HEAD(&empty_rp);
456 kretprobe_hash_lock(current, &head, &flags);
457
458 /*
459 * It is possible to have multiple instances associated with a given
460 * task either because multiple functions in the call path have
461 * a return probe installed on them, and/or more than one return
462 * return probe was registered for a target function.
463 *
464 * We can handle this because:
465 * - instances are always inserted at the head of the list
466 * - when multiple return probes are registered for the same
467 * function, the first instance's ret_addr will point to the
468 * real return address, and all the rest will point to
469 * kretprobe_trampoline
470 */
471 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
472 if (ri->task != current)
473 /* another task is sharing our hash bucket */
474 continue;
475
476 if (ri->rp && ri->rp->handler)
477 ri->rp->handler(ri, regs);
478
479 orig_ret_address = (unsigned long)ri->ret_addr;
480 recycle_rp_inst(ri, &empty_rp);
481
482 if (orig_ret_address != trampoline_address) {
483 /*
484 * This is the real return address. Any other
485 * instances associated with this task are for
486 * other calls deeper on the call stack
487 */
488 break;
489 }
490 }
491
492 kretprobe_assert(ri, orig_ret_address, trampoline_address);
493 instruction_pointer(regs) = orig_ret_address;
494
495 reset_current_kprobe();
496 kretprobe_hash_unlock(current, &flags);
497 preempt_enable_no_resched();
498
499 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
500 hlist_del(&ri->hlist);
501 kfree(ri);
502 }
503 /*
504 * By returning a non-zero value, we are telling
505 * kprobe_handler() that we don't want the post_handler
506 * to run (and have re-enabled preemption)
507 */
508 return 1;
509}
510
511int __kprobes arch_trampoline_kprobe(struct kprobe *p)
512{
513 if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
514 return 1;
515
516 return 0;
517}
518
519static struct kprobe trampoline_p = {
520 .addr = (kprobe_opcode_t *)kretprobe_trampoline,
521 .pre_handler = trampoline_probe_handler
522};
523
524int __init arch_init_kprobes(void)
525{
526 register_kprobe(&trampoline_p);
527 return 0;
528}