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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright IBM Corp. 2002, 2006
6 *
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
8 */
9
10#include <linux/kprobes.h>
11#include <linux/ptrace.h>
12#include <linux/preempt.h>
13#include <linux/stop_machine.h>
14#include <linux/kdebug.h>
15#include <linux/uaccess.h>
16#include <linux/extable.h>
17#include <linux/module.h>
18#include <linux/slab.h>
19#include <linux/hardirq.h>
20#include <linux/ftrace.h>
21#include <asm/set_memory.h>
22#include <asm/sections.h>
23#include <asm/dis.h>
24
25DEFINE_PER_CPU(struct kprobe *, current_kprobe);
26DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
27
28struct kretprobe_blackpoint kretprobe_blacklist[] = { };
29
30DEFINE_INSN_CACHE_OPS(dmainsn);
31
32static void *alloc_dmainsn_page(void)
33{
34 void *page;
35
36 page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA);
37 if (page)
38 set_memory_x((unsigned long) page, 1);
39 return page;
40}
41
42static void free_dmainsn_page(void *page)
43{
44 set_memory_nx((unsigned long) page, 1);
45 free_page((unsigned long)page);
46}
47
48struct kprobe_insn_cache kprobe_dmainsn_slots = {
49 .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
50 .alloc = alloc_dmainsn_page,
51 .free = free_dmainsn_page,
52 .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
53 .insn_size = MAX_INSN_SIZE,
54};
55
56static void copy_instruction(struct kprobe *p)
57{
58 unsigned long ip = (unsigned long) p->addr;
59 s64 disp, new_disp;
60 u64 addr, new_addr;
61
62 if (ftrace_location(ip) == ip) {
63 /*
64 * If kprobes patches the instruction that is morphed by
65 * ftrace make sure that kprobes always sees the branch
66 * "jg .+24" that skips the mcount block or the "brcl 0,0"
67 * in case of hotpatch.
68 */
69 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
70 p->ainsn.is_ftrace_insn = 1;
71 } else
72 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
73 p->opcode = p->ainsn.insn[0];
74 if (!probe_is_insn_relative_long(p->ainsn.insn))
75 return;
76 /*
77 * For pc-relative instructions in RIL-b or RIL-c format patch the
78 * RI2 displacement field. We have already made sure that the insn
79 * slot for the patched instruction is within the same 2GB area
80 * as the original instruction (either kernel image or module area).
81 * Therefore the new displacement will always fit.
82 */
83 disp = *(s32 *)&p->ainsn.insn[1];
84 addr = (u64)(unsigned long)p->addr;
85 new_addr = (u64)(unsigned long)p->ainsn.insn;
86 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
87 *(s32 *)&p->ainsn.insn[1] = new_disp;
88}
89NOKPROBE_SYMBOL(copy_instruction);
90
91static inline int is_kernel_addr(void *addr)
92{
93 return addr < (void *)_end;
94}
95
96static int s390_get_insn_slot(struct kprobe *p)
97{
98 /*
99 * Get an insn slot that is within the same 2GB area like the original
100 * instruction. That way instructions with a 32bit signed displacement
101 * field can be patched and executed within the insn slot.
102 */
103 p->ainsn.insn = NULL;
104 if (is_kernel_addr(p->addr))
105 p->ainsn.insn = get_dmainsn_slot();
106 else if (is_module_addr(p->addr))
107 p->ainsn.insn = get_insn_slot();
108 return p->ainsn.insn ? 0 : -ENOMEM;
109}
110NOKPROBE_SYMBOL(s390_get_insn_slot);
111
112static void s390_free_insn_slot(struct kprobe *p)
113{
114 if (!p->ainsn.insn)
115 return;
116 if (is_kernel_addr(p->addr))
117 free_dmainsn_slot(p->ainsn.insn, 0);
118 else
119 free_insn_slot(p->ainsn.insn, 0);
120 p->ainsn.insn = NULL;
121}
122NOKPROBE_SYMBOL(s390_free_insn_slot);
123
124int arch_prepare_kprobe(struct kprobe *p)
125{
126 if ((unsigned long) p->addr & 0x01)
127 return -EINVAL;
128 /* Make sure the probe isn't going on a difficult instruction */
129 if (probe_is_prohibited_opcode(p->addr))
130 return -EINVAL;
131 if (s390_get_insn_slot(p))
132 return -ENOMEM;
133 copy_instruction(p);
134 return 0;
135}
136NOKPROBE_SYMBOL(arch_prepare_kprobe);
137
138int arch_check_ftrace_location(struct kprobe *p)
139{
140 return 0;
141}
142
143struct swap_insn_args {
144 struct kprobe *p;
145 unsigned int arm_kprobe : 1;
146};
147
148static int swap_instruction(void *data)
149{
150 struct swap_insn_args *args = data;
151 struct ftrace_insn new_insn, *insn;
152 struct kprobe *p = args->p;
153 size_t len;
154
155 new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
156 len = sizeof(new_insn.opc);
157 if (!p->ainsn.is_ftrace_insn)
158 goto skip_ftrace;
159 len = sizeof(new_insn);
160 insn = (struct ftrace_insn *) p->addr;
161 if (args->arm_kprobe) {
162 if (is_ftrace_nop(insn))
163 new_insn.disp = KPROBE_ON_FTRACE_NOP;
164 else
165 new_insn.disp = KPROBE_ON_FTRACE_CALL;
166 } else {
167 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
168 if (insn->disp == KPROBE_ON_FTRACE_NOP)
169 ftrace_generate_nop_insn(&new_insn);
170 }
171skip_ftrace:
172 s390_kernel_write(p->addr, &new_insn, len);
173 return 0;
174}
175NOKPROBE_SYMBOL(swap_instruction);
176
177void arch_arm_kprobe(struct kprobe *p)
178{
179 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
180
181 stop_machine_cpuslocked(swap_instruction, &args, NULL);
182}
183NOKPROBE_SYMBOL(arch_arm_kprobe);
184
185void arch_disarm_kprobe(struct kprobe *p)
186{
187 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
188
189 stop_machine_cpuslocked(swap_instruction, &args, NULL);
190}
191NOKPROBE_SYMBOL(arch_disarm_kprobe);
192
193void arch_remove_kprobe(struct kprobe *p)
194{
195 s390_free_insn_slot(p);
196}
197NOKPROBE_SYMBOL(arch_remove_kprobe);
198
199static void enable_singlestep(struct kprobe_ctlblk *kcb,
200 struct pt_regs *regs,
201 unsigned long ip)
202{
203 struct per_regs per_kprobe;
204
205 /* Set up the PER control registers %cr9-%cr11 */
206 per_kprobe.control = PER_EVENT_IFETCH;
207 per_kprobe.start = ip;
208 per_kprobe.end = ip;
209
210 /* Save control regs and psw mask */
211 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
212 kcb->kprobe_saved_imask = regs->psw.mask &
213 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
214
215 /* Set PER control regs, turns on single step for the given address */
216 __ctl_load(per_kprobe, 9, 11);
217 regs->psw.mask |= PSW_MASK_PER;
218 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
219 regs->psw.addr = ip;
220}
221NOKPROBE_SYMBOL(enable_singlestep);
222
223static void disable_singlestep(struct kprobe_ctlblk *kcb,
224 struct pt_regs *regs,
225 unsigned long ip)
226{
227 /* Restore control regs and psw mask, set new psw address */
228 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
229 regs->psw.mask &= ~PSW_MASK_PER;
230 regs->psw.mask |= kcb->kprobe_saved_imask;
231 regs->psw.addr = ip;
232}
233NOKPROBE_SYMBOL(disable_singlestep);
234
235/*
236 * Activate a kprobe by storing its pointer to current_kprobe. The
237 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
238 * two kprobes can be active, see KPROBE_REENTER.
239 */
240static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
241{
242 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
243 kcb->prev_kprobe.status = kcb->kprobe_status;
244 __this_cpu_write(current_kprobe, p);
245}
246NOKPROBE_SYMBOL(push_kprobe);
247
248/*
249 * Deactivate a kprobe by backing up to the previous state. If the
250 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
251 * for any other state prev_kprobe.kp will be NULL.
252 */
253static void pop_kprobe(struct kprobe_ctlblk *kcb)
254{
255 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
256 kcb->kprobe_status = kcb->prev_kprobe.status;
257}
258NOKPROBE_SYMBOL(pop_kprobe);
259
260void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
261{
262 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
263
264 /* Replace the return addr with trampoline addr */
265 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
266}
267NOKPROBE_SYMBOL(arch_prepare_kretprobe);
268
269static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
270{
271 switch (kcb->kprobe_status) {
272 case KPROBE_HIT_SSDONE:
273 case KPROBE_HIT_ACTIVE:
274 kprobes_inc_nmissed_count(p);
275 break;
276 case KPROBE_HIT_SS:
277 case KPROBE_REENTER:
278 default:
279 /*
280 * A kprobe on the code path to single step an instruction
281 * is a BUG. The code path resides in the .kprobes.text
282 * section and is executed with interrupts disabled.
283 */
284 pr_err("Invalid kprobe detected.\n");
285 dump_kprobe(p);
286 BUG();
287 }
288}
289NOKPROBE_SYMBOL(kprobe_reenter_check);
290
291static int kprobe_handler(struct pt_regs *regs)
292{
293 struct kprobe_ctlblk *kcb;
294 struct kprobe *p;
295
296 /*
297 * We want to disable preemption for the entire duration of kprobe
298 * processing. That includes the calls to the pre/post handlers
299 * and single stepping the kprobe instruction.
300 */
301 preempt_disable();
302 kcb = get_kprobe_ctlblk();
303 p = get_kprobe((void *)(regs->psw.addr - 2));
304
305 if (p) {
306 if (kprobe_running()) {
307 /*
308 * We have hit a kprobe while another is still
309 * active. This can happen in the pre and post
310 * handler. Single step the instruction of the
311 * new probe but do not call any handler function
312 * of this secondary kprobe.
313 * push_kprobe and pop_kprobe saves and restores
314 * the currently active kprobe.
315 */
316 kprobe_reenter_check(kcb, p);
317 push_kprobe(kcb, p);
318 kcb->kprobe_status = KPROBE_REENTER;
319 } else {
320 /*
321 * If we have no pre-handler or it returned 0, we
322 * continue with single stepping. If we have a
323 * pre-handler and it returned non-zero, it prepped
324 * for calling the break_handler below on re-entry
325 * for jprobe processing, so get out doing nothing
326 * more here.
327 */
328 push_kprobe(kcb, p);
329 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
330 if (p->pre_handler && p->pre_handler(p, regs))
331 return 1;
332 kcb->kprobe_status = KPROBE_HIT_SS;
333 }
334 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
335 return 1;
336 } else if (kprobe_running()) {
337 p = __this_cpu_read(current_kprobe);
338 if (p->break_handler && p->break_handler(p, regs)) {
339 /*
340 * Continuation after the jprobe completed and
341 * caused the jprobe_return trap. The jprobe
342 * break_handler "returns" to the original
343 * function that still has the kprobe breakpoint
344 * installed. We continue with single stepping.
345 */
346 kcb->kprobe_status = KPROBE_HIT_SS;
347 enable_singlestep(kcb, regs,
348 (unsigned long) p->ainsn.insn);
349 return 1;
350 } /* else:
351 * No kprobe at this address and the current kprobe
352 * has no break handler (no jprobe!). The kernel just
353 * exploded, let the standard trap handler pick up the
354 * pieces.
355 */
356 } /* else:
357 * No kprobe at this address and no active kprobe. The trap has
358 * not been caused by a kprobe breakpoint. The race of breakpoint
359 * vs. kprobe remove does not exist because on s390 as we use
360 * stop_machine to arm/disarm the breakpoints.
361 */
362 preempt_enable_no_resched();
363 return 0;
364}
365NOKPROBE_SYMBOL(kprobe_handler);
366
367/*
368 * Function return probe trampoline:
369 * - init_kprobes() establishes a probepoint here
370 * - When the probed function returns, this probe
371 * causes the handlers to fire
372 */
373static void __used kretprobe_trampoline_holder(void)
374{
375 asm volatile(".global kretprobe_trampoline\n"
376 "kretprobe_trampoline: bcr 0,0\n");
377}
378
379/*
380 * Called when the probe at kretprobe trampoline is hit
381 */
382static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
383{
384 struct kretprobe_instance *ri;
385 struct hlist_head *head, empty_rp;
386 struct hlist_node *tmp;
387 unsigned long flags, orig_ret_address;
388 unsigned long trampoline_address;
389 kprobe_opcode_t *correct_ret_addr;
390
391 INIT_HLIST_HEAD(&empty_rp);
392 kretprobe_hash_lock(current, &head, &flags);
393
394 /*
395 * It is possible to have multiple instances associated with a given
396 * task either because an multiple functions in the call path
397 * have a return probe installed on them, and/or more than one return
398 * return probe was registered for a target function.
399 *
400 * We can handle this because:
401 * - instances are always inserted at the head of the list
402 * - when multiple return probes are registered for the same
403 * function, the first instance's ret_addr will point to the
404 * real return address, and all the rest will point to
405 * kretprobe_trampoline
406 */
407 ri = NULL;
408 orig_ret_address = 0;
409 correct_ret_addr = NULL;
410 trampoline_address = (unsigned long) &kretprobe_trampoline;
411 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
412 if (ri->task != current)
413 /* another task is sharing our hash bucket */
414 continue;
415
416 orig_ret_address = (unsigned long) ri->ret_addr;
417
418 if (orig_ret_address != trampoline_address)
419 /*
420 * This is the real return address. Any other
421 * instances associated with this task are for
422 * other calls deeper on the call stack
423 */
424 break;
425 }
426
427 kretprobe_assert(ri, orig_ret_address, trampoline_address);
428
429 correct_ret_addr = ri->ret_addr;
430 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
431 if (ri->task != current)
432 /* another task is sharing our hash bucket */
433 continue;
434
435 orig_ret_address = (unsigned long) ri->ret_addr;
436
437 if (ri->rp && ri->rp->handler) {
438 ri->ret_addr = correct_ret_addr;
439 ri->rp->handler(ri, regs);
440 }
441
442 recycle_rp_inst(ri, &empty_rp);
443
444 if (orig_ret_address != trampoline_address)
445 /*
446 * This is the real return address. Any other
447 * instances associated with this task are for
448 * other calls deeper on the call stack
449 */
450 break;
451 }
452
453 regs->psw.addr = orig_ret_address;
454
455 pop_kprobe(get_kprobe_ctlblk());
456 kretprobe_hash_unlock(current, &flags);
457 preempt_enable_no_resched();
458
459 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
460 hlist_del(&ri->hlist);
461 kfree(ri);
462 }
463 /*
464 * By returning a non-zero value, we are telling
465 * kprobe_handler() that we don't want the post_handler
466 * to run (and have re-enabled preemption)
467 */
468 return 1;
469}
470NOKPROBE_SYMBOL(trampoline_probe_handler);
471
472/*
473 * Called after single-stepping. p->addr is the address of the
474 * instruction whose first byte has been replaced by the "breakpoint"
475 * instruction. To avoid the SMP problems that can occur when we
476 * temporarily put back the original opcode to single-step, we
477 * single-stepped a copy of the instruction. The address of this
478 * copy is p->ainsn.insn.
479 */
480static void resume_execution(struct kprobe *p, struct pt_regs *regs)
481{
482 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
483 unsigned long ip = regs->psw.addr;
484 int fixup = probe_get_fixup_type(p->ainsn.insn);
485
486 /* Check if the kprobes location is an enabled ftrace caller */
487 if (p->ainsn.is_ftrace_insn) {
488 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
489 struct ftrace_insn call_insn;
490
491 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
492 /*
493 * A kprobe on an enabled ftrace call site actually single
494 * stepped an unconditional branch (ftrace nop equivalent).
495 * Now we need to fixup things and pretend that a brasl r0,...
496 * was executed instead.
497 */
498 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
499 ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
500 regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
501 }
502 }
503
504 if (fixup & FIXUP_PSW_NORMAL)
505 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
506
507 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
508 int ilen = insn_length(p->ainsn.insn[0] >> 8);
509 if (ip - (unsigned long) p->ainsn.insn == ilen)
510 ip = (unsigned long) p->addr + ilen;
511 }
512
513 if (fixup & FIXUP_RETURN_REGISTER) {
514 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
515 regs->gprs[reg] += (unsigned long) p->addr -
516 (unsigned long) p->ainsn.insn;
517 }
518
519 disable_singlestep(kcb, regs, ip);
520}
521NOKPROBE_SYMBOL(resume_execution);
522
523static int post_kprobe_handler(struct pt_regs *regs)
524{
525 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
526 struct kprobe *p = kprobe_running();
527
528 if (!p)
529 return 0;
530
531 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
532 kcb->kprobe_status = KPROBE_HIT_SSDONE;
533 p->post_handler(p, regs, 0);
534 }
535
536 resume_execution(p, regs);
537 pop_kprobe(kcb);
538 preempt_enable_no_resched();
539
540 /*
541 * if somebody else is singlestepping across a probe point, psw mask
542 * will have PER set, in which case, continue the remaining processing
543 * of do_single_step, as if this is not a probe hit.
544 */
545 if (regs->psw.mask & PSW_MASK_PER)
546 return 0;
547
548 return 1;
549}
550NOKPROBE_SYMBOL(post_kprobe_handler);
551
552static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
553{
554 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
555 struct kprobe *p = kprobe_running();
556 const struct exception_table_entry *entry;
557
558 switch(kcb->kprobe_status) {
559 case KPROBE_HIT_SS:
560 case KPROBE_REENTER:
561 /*
562 * We are here because the instruction being single
563 * stepped caused a page fault. We reset the current
564 * kprobe and the nip points back to the probe address
565 * and allow the page fault handler to continue as a
566 * normal page fault.
567 */
568 disable_singlestep(kcb, regs, (unsigned long) p->addr);
569 pop_kprobe(kcb);
570 preempt_enable_no_resched();
571 break;
572 case KPROBE_HIT_ACTIVE:
573 case KPROBE_HIT_SSDONE:
574 /*
575 * We increment the nmissed count for accounting,
576 * we can also use npre/npostfault count for accounting
577 * these specific fault cases.
578 */
579 kprobes_inc_nmissed_count(p);
580
581 /*
582 * We come here because instructions in the pre/post
583 * handler caused the page_fault, this could happen
584 * if handler tries to access user space by
585 * copy_from_user(), get_user() etc. Let the
586 * user-specified handler try to fix it first.
587 */
588 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
589 return 1;
590
591 /*
592 * In case the user-specified fault handler returned
593 * zero, try to fix up.
594 */
595 entry = search_exception_tables(regs->psw.addr);
596 if (entry) {
597 regs->psw.addr = extable_fixup(entry);
598 return 1;
599 }
600
601 /*
602 * fixup_exception() could not handle it,
603 * Let do_page_fault() fix it.
604 */
605 break;
606 default:
607 break;
608 }
609 return 0;
610}
611NOKPROBE_SYMBOL(kprobe_trap_handler);
612
613int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
614{
615 int ret;
616
617 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
618 local_irq_disable();
619 ret = kprobe_trap_handler(regs, trapnr);
620 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
621 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
622 return ret;
623}
624NOKPROBE_SYMBOL(kprobe_fault_handler);
625
626/*
627 * Wrapper routine to for handling exceptions.
628 */
629int kprobe_exceptions_notify(struct notifier_block *self,
630 unsigned long val, void *data)
631{
632 struct die_args *args = (struct die_args *) data;
633 struct pt_regs *regs = args->regs;
634 int ret = NOTIFY_DONE;
635
636 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
637 local_irq_disable();
638
639 switch (val) {
640 case DIE_BPT:
641 if (kprobe_handler(regs))
642 ret = NOTIFY_STOP;
643 break;
644 case DIE_SSTEP:
645 if (post_kprobe_handler(regs))
646 ret = NOTIFY_STOP;
647 break;
648 case DIE_TRAP:
649 if (!preemptible() && kprobe_running() &&
650 kprobe_trap_handler(regs, args->trapnr))
651 ret = NOTIFY_STOP;
652 break;
653 default:
654 break;
655 }
656
657 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
658 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
659
660 return ret;
661}
662NOKPROBE_SYMBOL(kprobe_exceptions_notify);
663
664int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
665{
666 struct jprobe *jp = container_of(p, struct jprobe, kp);
667 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
668 unsigned long stack;
669
670 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
671
672 /* setup return addr to the jprobe handler routine */
673 regs->psw.addr = (unsigned long) jp->entry;
674 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
675
676 /* r15 is the stack pointer */
677 stack = (unsigned long) regs->gprs[15];
678
679 memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
680
681 /*
682 * jprobes use jprobe_return() which skips the normal return
683 * path of the function, and this messes up the accounting of the
684 * function graph tracer to get messed up.
685 *
686 * Pause function graph tracing while performing the jprobe function.
687 */
688 pause_graph_tracing();
689 return 1;
690}
691NOKPROBE_SYMBOL(setjmp_pre_handler);
692
693void jprobe_return(void)
694{
695 asm volatile(".word 0x0002");
696}
697NOKPROBE_SYMBOL(jprobe_return);
698
699int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
700{
701 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
702 unsigned long stack;
703
704 /* It's OK to start function graph tracing again */
705 unpause_graph_tracing();
706
707 stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
708
709 /* Put the regs back */
710 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
711 /* put the stack back */
712 memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
713 preempt_enable_no_resched();
714 return 1;
715}
716NOKPROBE_SYMBOL(longjmp_break_handler);
717
718static struct kprobe trampoline = {
719 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
720 .pre_handler = trampoline_probe_handler
721};
722
723int __init arch_init_kprobes(void)
724{
725 return register_kprobe(&trampoline);
726}
727
728int arch_trampoline_kprobe(struct kprobe *p)
729{
730 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
731}
732NOKPROBE_SYMBOL(arch_trampoline_kprobe);
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Kernel Probes (KProbes)
4 *
5 * Copyright IBM Corp. 2002, 2006
6 *
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
8 */
9
10#include <linux/moduleloader.h>
11#include <linux/kprobes.h>
12#include <linux/ptrace.h>
13#include <linux/preempt.h>
14#include <linux/stop_machine.h>
15#include <linux/kdebug.h>
16#include <linux/uaccess.h>
17#include <linux/extable.h>
18#include <linux/module.h>
19#include <linux/slab.h>
20#include <linux/hardirq.h>
21#include <linux/ftrace.h>
22#include <asm/set_memory.h>
23#include <asm/sections.h>
24#include <asm/dis.h>
25#include "entry.h"
26
27DEFINE_PER_CPU(struct kprobe *, current_kprobe);
28DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
29
30struct kretprobe_blackpoint kretprobe_blacklist[] = { };
31
32DEFINE_INSN_CACHE_OPS(s390_insn);
33
34static int insn_page_in_use;
35
36void *alloc_insn_page(void)
37{
38 void *page;
39
40 page = module_alloc(PAGE_SIZE);
41 if (!page)
42 return NULL;
43 __set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
44 return page;
45}
46
47static void *alloc_s390_insn_page(void)
48{
49 if (xchg(&insn_page_in_use, 1) == 1)
50 return NULL;
51 return &kprobes_insn_page;
52}
53
54static void free_s390_insn_page(void *page)
55{
56 xchg(&insn_page_in_use, 0);
57}
58
59struct kprobe_insn_cache kprobe_s390_insn_slots = {
60 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
61 .alloc = alloc_s390_insn_page,
62 .free = free_s390_insn_page,
63 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
64 .insn_size = MAX_INSN_SIZE,
65};
66
67static void copy_instruction(struct kprobe *p)
68{
69 kprobe_opcode_t insn[MAX_INSN_SIZE];
70 s64 disp, new_disp;
71 u64 addr, new_addr;
72 unsigned int len;
73
74 len = insn_length(*p->addr >> 8);
75 memcpy(&insn, p->addr, len);
76 p->opcode = insn[0];
77 if (probe_is_insn_relative_long(&insn[0])) {
78 /*
79 * For pc-relative instructions in RIL-b or RIL-c format patch
80 * the RI2 displacement field. We have already made sure that
81 * the insn slot for the patched instruction is within the same
82 * 2GB area as the original instruction (either kernel image or
83 * module area). Therefore the new displacement will always fit.
84 */
85 disp = *(s32 *)&insn[1];
86 addr = (u64)(unsigned long)p->addr;
87 new_addr = (u64)(unsigned long)p->ainsn.insn;
88 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
89 *(s32 *)&insn[1] = new_disp;
90 }
91 s390_kernel_write(p->ainsn.insn, &insn, len);
92}
93NOKPROBE_SYMBOL(copy_instruction);
94
95static int s390_get_insn_slot(struct kprobe *p)
96{
97 /*
98 * Get an insn slot that is within the same 2GB area like the original
99 * instruction. That way instructions with a 32bit signed displacement
100 * field can be patched and executed within the insn slot.
101 */
102 p->ainsn.insn = NULL;
103 if (is_kernel((unsigned long)p->addr))
104 p->ainsn.insn = get_s390_insn_slot();
105 else if (is_module_addr(p->addr))
106 p->ainsn.insn = get_insn_slot();
107 return p->ainsn.insn ? 0 : -ENOMEM;
108}
109NOKPROBE_SYMBOL(s390_get_insn_slot);
110
111static void s390_free_insn_slot(struct kprobe *p)
112{
113 if (!p->ainsn.insn)
114 return;
115 if (is_kernel((unsigned long)p->addr))
116 free_s390_insn_slot(p->ainsn.insn, 0);
117 else
118 free_insn_slot(p->ainsn.insn, 0);
119 p->ainsn.insn = NULL;
120}
121NOKPROBE_SYMBOL(s390_free_insn_slot);
122
123int arch_prepare_kprobe(struct kprobe *p)
124{
125 if ((unsigned long) p->addr & 0x01)
126 return -EINVAL;
127 /* Make sure the probe isn't going on a difficult instruction */
128 if (probe_is_prohibited_opcode(p->addr))
129 return -EINVAL;
130 if (s390_get_insn_slot(p))
131 return -ENOMEM;
132 copy_instruction(p);
133 return 0;
134}
135NOKPROBE_SYMBOL(arch_prepare_kprobe);
136
137struct swap_insn_args {
138 struct kprobe *p;
139 unsigned int arm_kprobe : 1;
140};
141
142static int swap_instruction(void *data)
143{
144 struct swap_insn_args *args = data;
145 struct kprobe *p = args->p;
146 u16 opc;
147
148 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
149 s390_kernel_write(p->addr, &opc, sizeof(opc));
150 return 0;
151}
152NOKPROBE_SYMBOL(swap_instruction);
153
154void arch_arm_kprobe(struct kprobe *p)
155{
156 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
157
158 stop_machine_cpuslocked(swap_instruction, &args, NULL);
159}
160NOKPROBE_SYMBOL(arch_arm_kprobe);
161
162void arch_disarm_kprobe(struct kprobe *p)
163{
164 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
165
166 stop_machine_cpuslocked(swap_instruction, &args, NULL);
167}
168NOKPROBE_SYMBOL(arch_disarm_kprobe);
169
170void arch_remove_kprobe(struct kprobe *p)
171{
172 s390_free_insn_slot(p);
173}
174NOKPROBE_SYMBOL(arch_remove_kprobe);
175
176static void enable_singlestep(struct kprobe_ctlblk *kcb,
177 struct pt_regs *regs,
178 unsigned long ip)
179{
180 struct per_regs per_kprobe;
181
182 /* Set up the PER control registers %cr9-%cr11 */
183 per_kprobe.control = PER_EVENT_IFETCH;
184 per_kprobe.start = ip;
185 per_kprobe.end = ip;
186
187 /* Save control regs and psw mask */
188 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
189 kcb->kprobe_saved_imask = regs->psw.mask &
190 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
191
192 /* Set PER control regs, turns on single step for the given address */
193 __ctl_load(per_kprobe, 9, 11);
194 regs->psw.mask |= PSW_MASK_PER;
195 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
196 regs->psw.addr = ip;
197}
198NOKPROBE_SYMBOL(enable_singlestep);
199
200static void disable_singlestep(struct kprobe_ctlblk *kcb,
201 struct pt_regs *regs,
202 unsigned long ip)
203{
204 /* Restore control regs and psw mask, set new psw address */
205 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
206 regs->psw.mask &= ~PSW_MASK_PER;
207 regs->psw.mask |= kcb->kprobe_saved_imask;
208 regs->psw.addr = ip;
209}
210NOKPROBE_SYMBOL(disable_singlestep);
211
212/*
213 * Activate a kprobe by storing its pointer to current_kprobe. The
214 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
215 * two kprobes can be active, see KPROBE_REENTER.
216 */
217static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
218{
219 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
220 kcb->prev_kprobe.status = kcb->kprobe_status;
221 __this_cpu_write(current_kprobe, p);
222}
223NOKPROBE_SYMBOL(push_kprobe);
224
225/*
226 * Deactivate a kprobe by backing up to the previous state. If the
227 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
228 * for any other state prev_kprobe.kp will be NULL.
229 */
230static void pop_kprobe(struct kprobe_ctlblk *kcb)
231{
232 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
233 kcb->kprobe_status = kcb->prev_kprobe.status;
234}
235NOKPROBE_SYMBOL(pop_kprobe);
236
237void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
238{
239 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
240 ri->fp = NULL;
241
242 /* Replace the return addr with trampoline addr */
243 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
244}
245NOKPROBE_SYMBOL(arch_prepare_kretprobe);
246
247static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
248{
249 switch (kcb->kprobe_status) {
250 case KPROBE_HIT_SSDONE:
251 case KPROBE_HIT_ACTIVE:
252 kprobes_inc_nmissed_count(p);
253 break;
254 case KPROBE_HIT_SS:
255 case KPROBE_REENTER:
256 default:
257 /*
258 * A kprobe on the code path to single step an instruction
259 * is a BUG. The code path resides in the .kprobes.text
260 * section and is executed with interrupts disabled.
261 */
262 pr_err("Invalid kprobe detected.\n");
263 dump_kprobe(p);
264 BUG();
265 }
266}
267NOKPROBE_SYMBOL(kprobe_reenter_check);
268
269static int kprobe_handler(struct pt_regs *regs)
270{
271 struct kprobe_ctlblk *kcb;
272 struct kprobe *p;
273
274 /*
275 * We want to disable preemption for the entire duration of kprobe
276 * processing. That includes the calls to the pre/post handlers
277 * and single stepping the kprobe instruction.
278 */
279 preempt_disable();
280 kcb = get_kprobe_ctlblk();
281 p = get_kprobe((void *)(regs->psw.addr - 2));
282
283 if (p) {
284 if (kprobe_running()) {
285 /*
286 * We have hit a kprobe while another is still
287 * active. This can happen in the pre and post
288 * handler. Single step the instruction of the
289 * new probe but do not call any handler function
290 * of this secondary kprobe.
291 * push_kprobe and pop_kprobe saves and restores
292 * the currently active kprobe.
293 */
294 kprobe_reenter_check(kcb, p);
295 push_kprobe(kcb, p);
296 kcb->kprobe_status = KPROBE_REENTER;
297 } else {
298 /*
299 * If we have no pre-handler or it returned 0, we
300 * continue with single stepping. If we have a
301 * pre-handler and it returned non-zero, it prepped
302 * for changing execution path, so get out doing
303 * nothing more here.
304 */
305 push_kprobe(kcb, p);
306 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
307 if (p->pre_handler && p->pre_handler(p, regs)) {
308 pop_kprobe(kcb);
309 preempt_enable_no_resched();
310 return 1;
311 }
312 kcb->kprobe_status = KPROBE_HIT_SS;
313 }
314 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
315 return 1;
316 } /* else:
317 * No kprobe at this address and no active kprobe. The trap has
318 * not been caused by a kprobe breakpoint. The race of breakpoint
319 * vs. kprobe remove does not exist because on s390 as we use
320 * stop_machine to arm/disarm the breakpoints.
321 */
322 preempt_enable_no_resched();
323 return 0;
324}
325NOKPROBE_SYMBOL(kprobe_handler);
326
327/*
328 * Function return probe trampoline:
329 * - init_kprobes() establishes a probepoint here
330 * - When the probed function returns, this probe
331 * causes the handlers to fire
332 */
333static void __used kretprobe_trampoline_holder(void)
334{
335 asm volatile(".global kretprobe_trampoline\n"
336 "kretprobe_trampoline: bcr 0,0\n");
337}
338
339/*
340 * Called when the probe at kretprobe trampoline is hit
341 */
342static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
343{
344 regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
345 /*
346 * By returning a non-zero value, we are telling
347 * kprobe_handler() that we don't want the post_handler
348 * to run (and have re-enabled preemption)
349 */
350 return 1;
351}
352NOKPROBE_SYMBOL(trampoline_probe_handler);
353
354/*
355 * Called after single-stepping. p->addr is the address of the
356 * instruction whose first byte has been replaced by the "breakpoint"
357 * instruction. To avoid the SMP problems that can occur when we
358 * temporarily put back the original opcode to single-step, we
359 * single-stepped a copy of the instruction. The address of this
360 * copy is p->ainsn.insn.
361 */
362static void resume_execution(struct kprobe *p, struct pt_regs *regs)
363{
364 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
365 unsigned long ip = regs->psw.addr;
366 int fixup = probe_get_fixup_type(p->ainsn.insn);
367
368 if (fixup & FIXUP_PSW_NORMAL)
369 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
370
371 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
372 int ilen = insn_length(p->ainsn.insn[0] >> 8);
373 if (ip - (unsigned long) p->ainsn.insn == ilen)
374 ip = (unsigned long) p->addr + ilen;
375 }
376
377 if (fixup & FIXUP_RETURN_REGISTER) {
378 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
379 regs->gprs[reg] += (unsigned long) p->addr -
380 (unsigned long) p->ainsn.insn;
381 }
382
383 disable_singlestep(kcb, regs, ip);
384}
385NOKPROBE_SYMBOL(resume_execution);
386
387static int post_kprobe_handler(struct pt_regs *regs)
388{
389 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
390 struct kprobe *p = kprobe_running();
391
392 if (!p)
393 return 0;
394
395 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
396 kcb->kprobe_status = KPROBE_HIT_SSDONE;
397 p->post_handler(p, regs, 0);
398 }
399
400 resume_execution(p, regs);
401 pop_kprobe(kcb);
402 preempt_enable_no_resched();
403
404 /*
405 * if somebody else is singlestepping across a probe point, psw mask
406 * will have PER set, in which case, continue the remaining processing
407 * of do_single_step, as if this is not a probe hit.
408 */
409 if (regs->psw.mask & PSW_MASK_PER)
410 return 0;
411
412 return 1;
413}
414NOKPROBE_SYMBOL(post_kprobe_handler);
415
416static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
417{
418 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
419 struct kprobe *p = kprobe_running();
420 const struct exception_table_entry *entry;
421
422 switch(kcb->kprobe_status) {
423 case KPROBE_HIT_SS:
424 case KPROBE_REENTER:
425 /*
426 * We are here because the instruction being single
427 * stepped caused a page fault. We reset the current
428 * kprobe and the nip points back to the probe address
429 * and allow the page fault handler to continue as a
430 * normal page fault.
431 */
432 disable_singlestep(kcb, regs, (unsigned long) p->addr);
433 pop_kprobe(kcb);
434 preempt_enable_no_resched();
435 break;
436 case KPROBE_HIT_ACTIVE:
437 case KPROBE_HIT_SSDONE:
438 /*
439 * In case the user-specified fault handler returned
440 * zero, try to fix up.
441 */
442 entry = s390_search_extables(regs->psw.addr);
443 if (entry && ex_handle(entry, regs))
444 return 1;
445
446 /*
447 * fixup_exception() could not handle it,
448 * Let do_page_fault() fix it.
449 */
450 break;
451 default:
452 break;
453 }
454 return 0;
455}
456NOKPROBE_SYMBOL(kprobe_trap_handler);
457
458int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
459{
460 int ret;
461
462 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
463 local_irq_disable();
464 ret = kprobe_trap_handler(regs, trapnr);
465 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
466 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
467 return ret;
468}
469NOKPROBE_SYMBOL(kprobe_fault_handler);
470
471/*
472 * Wrapper routine to for handling exceptions.
473 */
474int kprobe_exceptions_notify(struct notifier_block *self,
475 unsigned long val, void *data)
476{
477 struct die_args *args = (struct die_args *) data;
478 struct pt_regs *regs = args->regs;
479 int ret = NOTIFY_DONE;
480
481 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
482 local_irq_disable();
483
484 switch (val) {
485 case DIE_BPT:
486 if (kprobe_handler(regs))
487 ret = NOTIFY_STOP;
488 break;
489 case DIE_SSTEP:
490 if (post_kprobe_handler(regs))
491 ret = NOTIFY_STOP;
492 break;
493 case DIE_TRAP:
494 if (!preemptible() && kprobe_running() &&
495 kprobe_trap_handler(regs, args->trapnr))
496 ret = NOTIFY_STOP;
497 break;
498 default:
499 break;
500 }
501
502 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
503 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
504
505 return ret;
506}
507NOKPROBE_SYMBOL(kprobe_exceptions_notify);
508
509static struct kprobe trampoline = {
510 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
511 .pre_handler = trampoline_probe_handler
512};
513
514int __init arch_init_kprobes(void)
515{
516 return register_kprobe(&trampoline);
517}
518
519int arch_trampoline_kprobe(struct kprobe *p)
520{
521 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
522}
523NOKPROBE_SYMBOL(arch_trampoline_kprobe);