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
);