1 // SPDX-License-Identifier: GPL-2.0+
3 * Kernel Probes (KProbes)
5 * Copyright IBM Corp. 2002, 2006
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
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>
25 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
26 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
28 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
30 DEFINE_INSN_CACHE_OPS(s390_insn);
32 static int insn_page_in_use;
33 static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);
35 static void *alloc_s390_insn_page(void)
37 if (xchg(&insn_page_in_use, 1) == 1)
39 set_memory_x((unsigned long) &insn_page, 1);
43 static void free_s390_insn_page(void *page)
45 set_memory_nx((unsigned long) page, 1);
46 xchg(&insn_page_in_use, 0);
49 struct kprobe_insn_cache kprobe_s390_insn_slots = {
50 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
51 .alloc = alloc_s390_insn_page,
52 .free = free_s390_insn_page,
53 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
54 .insn_size = MAX_INSN_SIZE,
57 static void copy_instruction(struct kprobe *p)
62 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
63 p->opcode = p->ainsn.insn[0];
64 if (!probe_is_insn_relative_long(p->ainsn.insn))
67 * For pc-relative instructions in RIL-b or RIL-c format patch the
68 * RI2 displacement field. We have already made sure that the insn
69 * slot for the patched instruction is within the same 2GB area
70 * as the original instruction (either kernel image or module area).
71 * Therefore the new displacement will always fit.
73 disp = *(s32 *)&p->ainsn.insn[1];
74 addr = (u64)(unsigned long)p->addr;
75 new_addr = (u64)(unsigned long)p->ainsn.insn;
76 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
77 *(s32 *)&p->ainsn.insn[1] = new_disp;
79 NOKPROBE_SYMBOL(copy_instruction);
81 static inline int is_kernel_addr(void *addr)
83 return addr < (void *)_end;
86 static int s390_get_insn_slot(struct kprobe *p)
89 * Get an insn slot that is within the same 2GB area like the original
90 * instruction. That way instructions with a 32bit signed displacement
91 * field can be patched and executed within the insn slot.
94 if (is_kernel_addr(p->addr))
95 p->ainsn.insn = get_s390_insn_slot();
96 else if (is_module_addr(p->addr))
97 p->ainsn.insn = get_insn_slot();
98 return p->ainsn.insn ? 0 : -ENOMEM;
100 NOKPROBE_SYMBOL(s390_get_insn_slot);
102 static void s390_free_insn_slot(struct kprobe *p)
106 if (is_kernel_addr(p->addr))
107 free_s390_insn_slot(p->ainsn.insn, 0);
109 free_insn_slot(p->ainsn.insn, 0);
110 p->ainsn.insn = NULL;
112 NOKPROBE_SYMBOL(s390_free_insn_slot);
114 int arch_prepare_kprobe(struct kprobe *p)
116 if ((unsigned long) p->addr & 0x01)
118 /* Make sure the probe isn't going on a difficult instruction */
119 if (probe_is_prohibited_opcode(p->addr))
121 if (s390_get_insn_slot(p))
126 NOKPROBE_SYMBOL(arch_prepare_kprobe);
128 struct swap_insn_args {
130 unsigned int arm_kprobe : 1;
133 static int swap_instruction(void *data)
135 struct swap_insn_args *args = data;
136 struct kprobe *p = args->p;
139 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
140 s390_kernel_write(p->addr, &opc, sizeof(opc));
143 NOKPROBE_SYMBOL(swap_instruction);
145 void arch_arm_kprobe(struct kprobe *p)
147 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
149 stop_machine_cpuslocked(swap_instruction, &args, NULL);
151 NOKPROBE_SYMBOL(arch_arm_kprobe);
153 void arch_disarm_kprobe(struct kprobe *p)
155 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
157 stop_machine_cpuslocked(swap_instruction, &args, NULL);
159 NOKPROBE_SYMBOL(arch_disarm_kprobe);
161 void arch_remove_kprobe(struct kprobe *p)
163 s390_free_insn_slot(p);
165 NOKPROBE_SYMBOL(arch_remove_kprobe);
167 static void enable_singlestep(struct kprobe_ctlblk *kcb,
168 struct pt_regs *regs,
171 struct per_regs per_kprobe;
173 /* Set up the PER control registers %cr9-%cr11 */
174 per_kprobe.control = PER_EVENT_IFETCH;
175 per_kprobe.start = ip;
178 /* Save control regs and psw mask */
179 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
180 kcb->kprobe_saved_imask = regs->psw.mask &
181 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
183 /* Set PER control regs, turns on single step for the given address */
184 __ctl_load(per_kprobe, 9, 11);
185 regs->psw.mask |= PSW_MASK_PER;
186 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
189 NOKPROBE_SYMBOL(enable_singlestep);
191 static void disable_singlestep(struct kprobe_ctlblk *kcb,
192 struct pt_regs *regs,
195 /* Restore control regs and psw mask, set new psw address */
196 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
197 regs->psw.mask &= ~PSW_MASK_PER;
198 regs->psw.mask |= kcb->kprobe_saved_imask;
201 NOKPROBE_SYMBOL(disable_singlestep);
204 * Activate a kprobe by storing its pointer to current_kprobe. The
205 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
206 * two kprobes can be active, see KPROBE_REENTER.
208 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
210 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
211 kcb->prev_kprobe.status = kcb->kprobe_status;
212 __this_cpu_write(current_kprobe, p);
214 NOKPROBE_SYMBOL(push_kprobe);
217 * Deactivate a kprobe by backing up to the previous state. If the
218 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
219 * for any other state prev_kprobe.kp will be NULL.
221 static void pop_kprobe(struct kprobe_ctlblk *kcb)
223 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
224 kcb->kprobe_status = kcb->prev_kprobe.status;
226 NOKPROBE_SYMBOL(pop_kprobe);
228 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
230 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
232 /* Replace the return addr with trampoline addr */
233 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
235 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
237 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
239 switch (kcb->kprobe_status) {
240 case KPROBE_HIT_SSDONE:
241 case KPROBE_HIT_ACTIVE:
242 kprobes_inc_nmissed_count(p);
248 * A kprobe on the code path to single step an instruction
249 * is a BUG. The code path resides in the .kprobes.text
250 * section and is executed with interrupts disabled.
252 pr_err("Invalid kprobe detected.\n");
257 NOKPROBE_SYMBOL(kprobe_reenter_check);
259 static int kprobe_handler(struct pt_regs *regs)
261 struct kprobe_ctlblk *kcb;
265 * We want to disable preemption for the entire duration of kprobe
266 * processing. That includes the calls to the pre/post handlers
267 * and single stepping the kprobe instruction.
270 kcb = get_kprobe_ctlblk();
271 p = get_kprobe((void *)(regs->psw.addr - 2));
274 if (kprobe_running()) {
276 * We have hit a kprobe while another is still
277 * active. This can happen in the pre and post
278 * handler. Single step the instruction of the
279 * new probe but do not call any handler function
280 * of this secondary kprobe.
281 * push_kprobe and pop_kprobe saves and restores
282 * the currently active kprobe.
284 kprobe_reenter_check(kcb, p);
286 kcb->kprobe_status = KPROBE_REENTER;
289 * If we have no pre-handler or it returned 0, we
290 * continue with single stepping. If we have a
291 * pre-handler and it returned non-zero, it prepped
292 * for changing execution path, so get out doing
296 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
297 if (p->pre_handler && p->pre_handler(p, regs)) {
299 preempt_enable_no_resched();
302 kcb->kprobe_status = KPROBE_HIT_SS;
304 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
307 * No kprobe at this address and no active kprobe. The trap has
308 * not been caused by a kprobe breakpoint. The race of breakpoint
309 * vs. kprobe remove does not exist because on s390 as we use
310 * stop_machine to arm/disarm the breakpoints.
312 preempt_enable_no_resched();
315 NOKPROBE_SYMBOL(kprobe_handler);
318 * Function return probe trampoline:
319 * - init_kprobes() establishes a probepoint here
320 * - When the probed function returns, this probe
321 * causes the handlers to fire
323 static void __used kretprobe_trampoline_holder(void)
325 asm volatile(".global kretprobe_trampoline\n"
326 "kretprobe_trampoline: bcr 0,0\n");
330 * Called when the probe at kretprobe trampoline is hit
332 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
334 struct kretprobe_instance *ri;
335 struct hlist_head *head, empty_rp;
336 struct hlist_node *tmp;
337 unsigned long flags, orig_ret_address;
338 unsigned long trampoline_address;
339 kprobe_opcode_t *correct_ret_addr;
341 INIT_HLIST_HEAD(&empty_rp);
342 kretprobe_hash_lock(current, &head, &flags);
345 * It is possible to have multiple instances associated with a given
346 * task either because an multiple functions in the call path
347 * have a return probe installed on them, and/or more than one return
348 * return probe was registered for a target function.
350 * We can handle this because:
351 * - instances are always inserted at the head of the list
352 * - when multiple return probes are registered for the same
353 * function, the first instance's ret_addr will point to the
354 * real return address, and all the rest will point to
355 * kretprobe_trampoline
358 orig_ret_address = 0;
359 correct_ret_addr = NULL;
360 trampoline_address = (unsigned long) &kretprobe_trampoline;
361 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
362 if (ri->task != current)
363 /* another task is sharing our hash bucket */
366 orig_ret_address = (unsigned long) ri->ret_addr;
368 if (orig_ret_address != trampoline_address)
370 * This is the real return address. Any other
371 * instances associated with this task are for
372 * other calls deeper on the call stack
377 kretprobe_assert(ri, orig_ret_address, trampoline_address);
379 correct_ret_addr = ri->ret_addr;
380 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
381 if (ri->task != current)
382 /* another task is sharing our hash bucket */
385 orig_ret_address = (unsigned long) ri->ret_addr;
387 if (ri->rp && ri->rp->handler) {
388 ri->ret_addr = correct_ret_addr;
389 ri->rp->handler(ri, regs);
392 recycle_rp_inst(ri, &empty_rp);
394 if (orig_ret_address != trampoline_address)
396 * This is the real return address. Any other
397 * instances associated with this task are for
398 * other calls deeper on the call stack
403 regs->psw.addr = orig_ret_address;
405 kretprobe_hash_unlock(current, &flags);
407 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
408 hlist_del(&ri->hlist);
412 * By returning a non-zero value, we are telling
413 * kprobe_handler() that we don't want the post_handler
414 * to run (and have re-enabled preemption)
418 NOKPROBE_SYMBOL(trampoline_probe_handler);
421 * Called after single-stepping. p->addr is the address of the
422 * instruction whose first byte has been replaced by the "breakpoint"
423 * instruction. To avoid the SMP problems that can occur when we
424 * temporarily put back the original opcode to single-step, we
425 * single-stepped a copy of the instruction. The address of this
426 * copy is p->ainsn.insn.
428 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
430 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
431 unsigned long ip = regs->psw.addr;
432 int fixup = probe_get_fixup_type(p->ainsn.insn);
434 if (fixup & FIXUP_PSW_NORMAL)
435 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
437 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
438 int ilen = insn_length(p->ainsn.insn[0] >> 8);
439 if (ip - (unsigned long) p->ainsn.insn == ilen)
440 ip = (unsigned long) p->addr + ilen;
443 if (fixup & FIXUP_RETURN_REGISTER) {
444 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
445 regs->gprs[reg] += (unsigned long) p->addr -
446 (unsigned long) p->ainsn.insn;
449 disable_singlestep(kcb, regs, ip);
451 NOKPROBE_SYMBOL(resume_execution);
453 static int post_kprobe_handler(struct pt_regs *regs)
455 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
456 struct kprobe *p = kprobe_running();
461 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
462 kcb->kprobe_status = KPROBE_HIT_SSDONE;
463 p->post_handler(p, regs, 0);
466 resume_execution(p, regs);
468 preempt_enable_no_resched();
471 * if somebody else is singlestepping across a probe point, psw mask
472 * will have PER set, in which case, continue the remaining processing
473 * of do_single_step, as if this is not a probe hit.
475 if (regs->psw.mask & PSW_MASK_PER)
480 NOKPROBE_SYMBOL(post_kprobe_handler);
482 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
484 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
485 struct kprobe *p = kprobe_running();
486 const struct exception_table_entry *entry;
488 switch(kcb->kprobe_status) {
492 * We are here because the instruction being single
493 * stepped caused a page fault. We reset the current
494 * kprobe and the nip points back to the probe address
495 * and allow the page fault handler to continue as a
498 disable_singlestep(kcb, regs, (unsigned long) p->addr);
500 preempt_enable_no_resched();
502 case KPROBE_HIT_ACTIVE:
503 case KPROBE_HIT_SSDONE:
505 * We increment the nmissed count for accounting,
506 * we can also use npre/npostfault count for accounting
507 * these specific fault cases.
509 kprobes_inc_nmissed_count(p);
512 * We come here because instructions in the pre/post
513 * handler caused the page_fault, this could happen
514 * if handler tries to access user space by
515 * copy_from_user(), get_user() etc. Let the
516 * user-specified handler try to fix it first.
518 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
522 * In case the user-specified fault handler returned
523 * zero, try to fix up.
525 entry = s390_search_extables(regs->psw.addr);
527 regs->psw.addr = extable_fixup(entry);
532 * fixup_exception() could not handle it,
533 * Let do_page_fault() fix it.
541 NOKPROBE_SYMBOL(kprobe_trap_handler);
543 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
547 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
549 ret = kprobe_trap_handler(regs, trapnr);
550 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
551 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
554 NOKPROBE_SYMBOL(kprobe_fault_handler);
557 * Wrapper routine to for handling exceptions.
559 int kprobe_exceptions_notify(struct notifier_block *self,
560 unsigned long val, void *data)
562 struct die_args *args = (struct die_args *) data;
563 struct pt_regs *regs = args->regs;
564 int ret = NOTIFY_DONE;
566 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
571 if (kprobe_handler(regs))
575 if (post_kprobe_handler(regs))
579 if (!preemptible() && kprobe_running() &&
580 kprobe_trap_handler(regs, args->trapnr))
587 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
588 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
592 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
594 static struct kprobe trampoline = {
595 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
596 .pre_handler = trampoline_probe_handler
599 int __init arch_init_kprobes(void)
601 return register_kprobe(&trampoline);
604 int arch_trampoline_kprobe(struct kprobe *p)
606 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
608 NOKPROBE_SYMBOL(arch_trampoline_kprobe);