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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#define pr_fmt(fmt) "kprobes: " fmt
11
12#include <linux/moduleloader.h>
13#include <linux/kprobes.h>
14#include <linux/ptrace.h>
15#include <linux/preempt.h>
16#include <linux/stop_machine.h>
17#include <linux/kdebug.h>
18#include <linux/uaccess.h>
19#include <linux/extable.h>
20#include <linux/module.h>
21#include <linux/slab.h>
22#include <linux/hardirq.h>
23#include <linux/ftrace.h>
24#include <asm/set_memory.h>
25#include <asm/sections.h>
26#include <asm/dis.h>
27#include "kprobes.h"
28#include "entry.h"
29
30DEFINE_PER_CPU(struct kprobe *, current_kprobe);
31DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
32
33struct kretprobe_blackpoint kretprobe_blacklist[] = { };
34
35static int insn_page_in_use;
36
37void *alloc_insn_page(void)
38{
39 void *page;
40
41 page = module_alloc(PAGE_SIZE);
42 if (!page)
43 return NULL;
44 set_memory_rox((unsigned long)page, 1);
45 return page;
46}
47
48static void *alloc_s390_insn_page(void)
49{
50 if (xchg(&insn_page_in_use, 1) == 1)
51 return NULL;
52 return &kprobes_insn_page;
53}
54
55static void free_s390_insn_page(void *page)
56{
57 xchg(&insn_page_in_use, 0);
58}
59
60struct kprobe_insn_cache kprobe_s390_insn_slots = {
61 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
62 .alloc = alloc_s390_insn_page,
63 .free = free_s390_insn_page,
64 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
65 .insn_size = MAX_INSN_SIZE,
66};
67
68static void copy_instruction(struct kprobe *p)
69{
70 kprobe_opcode_t insn[MAX_INSN_SIZE];
71 s64 disp, new_disp;
72 u64 addr, new_addr;
73 unsigned int len;
74
75 len = insn_length(*p->addr >> 8);
76 memcpy(&insn, p->addr, len);
77 p->opcode = insn[0];
78 if (probe_is_insn_relative_long(&insn[0])) {
79 /*
80 * For pc-relative instructions in RIL-b or RIL-c format patch
81 * the RI2 displacement field. We have already made sure that
82 * the insn slot for the patched instruction is within the same
83 * 2GB area as the original instruction (either kernel image or
84 * module area). Therefore the new displacement will always fit.
85 */
86 disp = *(s32 *)&insn[1];
87 addr = (u64)(unsigned long)p->addr;
88 new_addr = (u64)(unsigned long)p->ainsn.insn;
89 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
90 *(s32 *)&insn[1] = new_disp;
91 }
92 s390_kernel_write(p->ainsn.insn, &insn, len);
93}
94NOKPROBE_SYMBOL(copy_instruction);
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((unsigned long)p->addr))
105 p->ainsn.insn = get_s390_insn_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((unsigned long)p->addr))
117 free_s390_insn_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
124/* Check if paddr is at an instruction boundary */
125static bool can_probe(unsigned long paddr)
126{
127 unsigned long addr, offset = 0;
128 kprobe_opcode_t insn;
129 struct kprobe *kp;
130
131 if (paddr & 0x01)
132 return false;
133
134 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
135 return false;
136
137 /* Decode instructions */
138 addr = paddr - offset;
139 while (addr < paddr) {
140 if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
141 return false;
142
143 if (insn >> 8 == 0) {
144 if (insn != BREAKPOINT_INSTRUCTION) {
145 /*
146 * Note that QEMU inserts opcode 0x0000 to implement
147 * software breakpoints for guests. Since the size of
148 * the original instruction is unknown, stop following
149 * instructions and prevent setting a kprobe.
150 */
151 return false;
152 }
153 /*
154 * Check if the instruction has been modified by another
155 * kprobe, in which case the original instruction is
156 * decoded.
157 */
158 kp = get_kprobe((void *)addr);
159 if (!kp) {
160 /* not a kprobe */
161 return false;
162 }
163 insn = kp->opcode;
164 }
165 addr += insn_length(insn >> 8);
166 }
167 return addr == paddr;
168}
169
170int arch_prepare_kprobe(struct kprobe *p)
171{
172 if (!can_probe((unsigned long)p->addr))
173 return -EINVAL;
174 /* Make sure the probe isn't going on a difficult instruction */
175 if (probe_is_prohibited_opcode(p->addr))
176 return -EINVAL;
177 if (s390_get_insn_slot(p))
178 return -ENOMEM;
179 copy_instruction(p);
180 return 0;
181}
182NOKPROBE_SYMBOL(arch_prepare_kprobe);
183
184struct swap_insn_args {
185 struct kprobe *p;
186 unsigned int arm_kprobe : 1;
187};
188
189static int swap_instruction(void *data)
190{
191 struct swap_insn_args *args = data;
192 struct kprobe *p = args->p;
193 u16 opc;
194
195 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
196 s390_kernel_write(p->addr, &opc, sizeof(opc));
197 return 0;
198}
199NOKPROBE_SYMBOL(swap_instruction);
200
201void arch_arm_kprobe(struct kprobe *p)
202{
203 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
204
205 stop_machine_cpuslocked(swap_instruction, &args, NULL);
206}
207NOKPROBE_SYMBOL(arch_arm_kprobe);
208
209void arch_disarm_kprobe(struct kprobe *p)
210{
211 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
212
213 stop_machine_cpuslocked(swap_instruction, &args, NULL);
214}
215NOKPROBE_SYMBOL(arch_disarm_kprobe);
216
217void arch_remove_kprobe(struct kprobe *p)
218{
219 s390_free_insn_slot(p);
220}
221NOKPROBE_SYMBOL(arch_remove_kprobe);
222
223static void enable_singlestep(struct kprobe_ctlblk *kcb,
224 struct pt_regs *regs,
225 unsigned long ip)
226{
227 union {
228 struct ctlreg regs[3];
229 struct {
230 struct ctlreg control;
231 struct ctlreg start;
232 struct ctlreg end;
233 };
234 } per_kprobe;
235
236 /* Set up the PER control registers %cr9-%cr11 */
237 per_kprobe.control.val = PER_EVENT_IFETCH;
238 per_kprobe.start.val = ip;
239 per_kprobe.end.val = ip;
240
241 /* Save control regs and psw mask */
242 __local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
243 kcb->kprobe_saved_imask = regs->psw.mask &
244 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
245
246 /* Set PER control regs, turns on single step for the given address */
247 __local_ctl_load(9, 11, per_kprobe.regs);
248 regs->psw.mask |= PSW_MASK_PER;
249 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
250 regs->psw.addr = ip;
251}
252NOKPROBE_SYMBOL(enable_singlestep);
253
254static void disable_singlestep(struct kprobe_ctlblk *kcb,
255 struct pt_regs *regs,
256 unsigned long ip)
257{
258 /* Restore control regs and psw mask, set new psw address */
259 __local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
260 regs->psw.mask &= ~PSW_MASK_PER;
261 regs->psw.mask |= kcb->kprobe_saved_imask;
262 regs->psw.addr = ip;
263}
264NOKPROBE_SYMBOL(disable_singlestep);
265
266/*
267 * Activate a kprobe by storing its pointer to current_kprobe. The
268 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
269 * two kprobes can be active, see KPROBE_REENTER.
270 */
271static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
272{
273 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
274 kcb->prev_kprobe.status = kcb->kprobe_status;
275 __this_cpu_write(current_kprobe, p);
276}
277NOKPROBE_SYMBOL(push_kprobe);
278
279/*
280 * Deactivate a kprobe by backing up to the previous state. If the
281 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
282 * for any other state prev_kprobe.kp will be NULL.
283 */
284static void pop_kprobe(struct kprobe_ctlblk *kcb)
285{
286 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
287 kcb->kprobe_status = kcb->prev_kprobe.status;
288 kcb->prev_kprobe.kp = NULL;
289}
290NOKPROBE_SYMBOL(pop_kprobe);
291
292static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
293{
294 switch (kcb->kprobe_status) {
295 case KPROBE_HIT_SSDONE:
296 case KPROBE_HIT_ACTIVE:
297 kprobes_inc_nmissed_count(p);
298 break;
299 case KPROBE_HIT_SS:
300 case KPROBE_REENTER:
301 default:
302 /*
303 * A kprobe on the code path to single step an instruction
304 * is a BUG. The code path resides in the .kprobes.text
305 * section and is executed with interrupts disabled.
306 */
307 pr_err("Failed to recover from reentered kprobes.\n");
308 dump_kprobe(p);
309 BUG();
310 }
311}
312NOKPROBE_SYMBOL(kprobe_reenter_check);
313
314static int kprobe_handler(struct pt_regs *regs)
315{
316 struct kprobe_ctlblk *kcb;
317 struct kprobe *p;
318
319 /*
320 * We want to disable preemption for the entire duration of kprobe
321 * processing. That includes the calls to the pre/post handlers
322 * and single stepping the kprobe instruction.
323 */
324 preempt_disable();
325 kcb = get_kprobe_ctlblk();
326 p = get_kprobe((void *)(regs->psw.addr - 2));
327
328 if (p) {
329 if (kprobe_running()) {
330 /*
331 * We have hit a kprobe while another is still
332 * active. This can happen in the pre and post
333 * handler. Single step the instruction of the
334 * new probe but do not call any handler function
335 * of this secondary kprobe.
336 * push_kprobe and pop_kprobe saves and restores
337 * the currently active kprobe.
338 */
339 kprobe_reenter_check(kcb, p);
340 push_kprobe(kcb, p);
341 kcb->kprobe_status = KPROBE_REENTER;
342 } else {
343 /*
344 * If we have no pre-handler or it returned 0, we
345 * continue with single stepping. If we have a
346 * pre-handler and it returned non-zero, it prepped
347 * for changing execution path, so get out doing
348 * nothing more here.
349 */
350 push_kprobe(kcb, p);
351 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
352 if (p->pre_handler && p->pre_handler(p, regs)) {
353 pop_kprobe(kcb);
354 preempt_enable_no_resched();
355 return 1;
356 }
357 kcb->kprobe_status = KPROBE_HIT_SS;
358 }
359 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
360 return 1;
361 } /* else:
362 * No kprobe at this address and no active kprobe. The trap has
363 * not been caused by a kprobe breakpoint. The race of breakpoint
364 * vs. kprobe remove does not exist because on s390 as we use
365 * stop_machine to arm/disarm the breakpoints.
366 */
367 preempt_enable_no_resched();
368 return 0;
369}
370NOKPROBE_SYMBOL(kprobe_handler);
371
372/*
373 * Called after single-stepping. p->addr is the address of the
374 * instruction whose first byte has been replaced by the "breakpoint"
375 * instruction. To avoid the SMP problems that can occur when we
376 * temporarily put back the original opcode to single-step, we
377 * single-stepped a copy of the instruction. The address of this
378 * copy is p->ainsn.insn.
379 */
380static void resume_execution(struct kprobe *p, struct pt_regs *regs)
381{
382 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
383 unsigned long ip = regs->psw.addr;
384 int fixup = probe_get_fixup_type(p->ainsn.insn);
385
386 if (fixup & FIXUP_PSW_NORMAL)
387 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
388
389 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
390 int ilen = insn_length(p->ainsn.insn[0] >> 8);
391 if (ip - (unsigned long) p->ainsn.insn == ilen)
392 ip = (unsigned long) p->addr + ilen;
393 }
394
395 if (fixup & FIXUP_RETURN_REGISTER) {
396 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
397 regs->gprs[reg] += (unsigned long) p->addr -
398 (unsigned long) p->ainsn.insn;
399 }
400
401 disable_singlestep(kcb, regs, ip);
402}
403NOKPROBE_SYMBOL(resume_execution);
404
405static int post_kprobe_handler(struct pt_regs *regs)
406{
407 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
408 struct kprobe *p = kprobe_running();
409
410 if (!p)
411 return 0;
412
413 resume_execution(p, regs);
414 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
415 kcb->kprobe_status = KPROBE_HIT_SSDONE;
416 p->post_handler(p, regs, 0);
417 }
418 pop_kprobe(kcb);
419 preempt_enable_no_resched();
420
421 /*
422 * if somebody else is singlestepping across a probe point, psw mask
423 * will have PER set, in which case, continue the remaining processing
424 * of do_single_step, as if this is not a probe hit.
425 */
426 if (regs->psw.mask & PSW_MASK_PER)
427 return 0;
428
429 return 1;
430}
431NOKPROBE_SYMBOL(post_kprobe_handler);
432
433static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
434{
435 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
436 struct kprobe *p = kprobe_running();
437
438 switch(kcb->kprobe_status) {
439 case KPROBE_HIT_SS:
440 case KPROBE_REENTER:
441 /*
442 * We are here because the instruction being single
443 * stepped caused a page fault. We reset the current
444 * kprobe and the nip points back to the probe address
445 * and allow the page fault handler to continue as a
446 * normal page fault.
447 */
448 disable_singlestep(kcb, regs, (unsigned long) p->addr);
449 pop_kprobe(kcb);
450 preempt_enable_no_resched();
451 break;
452 case KPROBE_HIT_ACTIVE:
453 case KPROBE_HIT_SSDONE:
454 /*
455 * In case the user-specified fault handler returned
456 * zero, try to fix up.
457 */
458 if (fixup_exception(regs))
459 return 1;
460 /*
461 * fixup_exception() could not handle it,
462 * Let do_page_fault() fix it.
463 */
464 break;
465 default:
466 break;
467 }
468 return 0;
469}
470NOKPROBE_SYMBOL(kprobe_trap_handler);
471
472int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
473{
474 int ret;
475
476 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
477 local_irq_disable();
478 ret = kprobe_trap_handler(regs, trapnr);
479 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
480 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
481 return ret;
482}
483NOKPROBE_SYMBOL(kprobe_fault_handler);
484
485/*
486 * Wrapper routine to for handling exceptions.
487 */
488int kprobe_exceptions_notify(struct notifier_block *self,
489 unsigned long val, void *data)
490{
491 struct die_args *args = (struct die_args *) data;
492 struct pt_regs *regs = args->regs;
493 int ret = NOTIFY_DONE;
494
495 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
496 local_irq_disable();
497
498 switch (val) {
499 case DIE_BPT:
500 if (kprobe_handler(regs))
501 ret = NOTIFY_STOP;
502 break;
503 case DIE_SSTEP:
504 if (post_kprobe_handler(regs))
505 ret = NOTIFY_STOP;
506 break;
507 case DIE_TRAP:
508 if (!preemptible() && kprobe_running() &&
509 kprobe_trap_handler(regs, args->trapnr))
510 ret = NOTIFY_STOP;
511 break;
512 default:
513 break;
514 }
515
516 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
517 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
518
519 return ret;
520}
521NOKPROBE_SYMBOL(kprobe_exceptions_notify);
522
523int __init arch_init_kprobes(void)
524{
525 return 0;
526}
527
528int arch_trampoline_kprobe(struct kprobe *p)
529{
530 return 0;
531}
532NOKPROBE_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/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(s390_insn);
31
32static int insn_page_in_use;
33static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);
34
35static void *alloc_s390_insn_page(void)
36{
37 if (xchg(&insn_page_in_use, 1) == 1)
38 return NULL;
39 set_memory_x((unsigned long) &insn_page, 1);
40 return &insn_page;
41}
42
43static void free_s390_insn_page(void *page)
44{
45 set_memory_nx((unsigned long) page, 1);
46 xchg(&insn_page_in_use, 0);
47}
48
49struct 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,
55};
56
57static void copy_instruction(struct kprobe *p)
58{
59 unsigned long ip = (unsigned long) p->addr;
60 s64 disp, new_disp;
61 u64 addr, new_addr;
62
63 if (ftrace_location(ip) == ip) {
64 /*
65 * If kprobes patches the instruction that is morphed by
66 * ftrace make sure that kprobes always sees the branch
67 * "jg .+24" that skips the mcount block or the "brcl 0,0"
68 * in case of hotpatch.
69 */
70 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
71 p->ainsn.is_ftrace_insn = 1;
72 } else
73 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
74 p->opcode = p->ainsn.insn[0];
75 if (!probe_is_insn_relative_long(p->ainsn.insn))
76 return;
77 /*
78 * For pc-relative instructions in RIL-b or RIL-c format patch the
79 * RI2 displacement field. We have already made sure that the insn
80 * slot for the patched instruction is within the same 2GB area
81 * as the original instruction (either kernel image or module area).
82 * Therefore the new displacement will always fit.
83 */
84 disp = *(s32 *)&p->ainsn.insn[1];
85 addr = (u64)(unsigned long)p->addr;
86 new_addr = (u64)(unsigned long)p->ainsn.insn;
87 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
88 *(s32 *)&p->ainsn.insn[1] = new_disp;
89}
90NOKPROBE_SYMBOL(copy_instruction);
91
92static inline int is_kernel_addr(void *addr)
93{
94 return addr < (void *)_end;
95}
96
97static int s390_get_insn_slot(struct kprobe *p)
98{
99 /*
100 * Get an insn slot that is within the same 2GB area like the original
101 * instruction. That way instructions with a 32bit signed displacement
102 * field can be patched and executed within the insn slot.
103 */
104 p->ainsn.insn = NULL;
105 if (is_kernel_addr(p->addr))
106 p->ainsn.insn = get_s390_insn_slot();
107 else if (is_module_addr(p->addr))
108 p->ainsn.insn = get_insn_slot();
109 return p->ainsn.insn ? 0 : -ENOMEM;
110}
111NOKPROBE_SYMBOL(s390_get_insn_slot);
112
113static void s390_free_insn_slot(struct kprobe *p)
114{
115 if (!p->ainsn.insn)
116 return;
117 if (is_kernel_addr(p->addr))
118 free_s390_insn_slot(p->ainsn.insn, 0);
119 else
120 free_insn_slot(p->ainsn.insn, 0);
121 p->ainsn.insn = NULL;
122}
123NOKPROBE_SYMBOL(s390_free_insn_slot);
124
125int arch_prepare_kprobe(struct kprobe *p)
126{
127 if ((unsigned long) p->addr & 0x01)
128 return -EINVAL;
129 /* Make sure the probe isn't going on a difficult instruction */
130 if (probe_is_prohibited_opcode(p->addr))
131 return -EINVAL;
132 if (s390_get_insn_slot(p))
133 return -ENOMEM;
134 copy_instruction(p);
135 return 0;
136}
137NOKPROBE_SYMBOL(arch_prepare_kprobe);
138
139int arch_check_ftrace_location(struct kprobe *p)
140{
141 return 0;
142}
143
144struct swap_insn_args {
145 struct kprobe *p;
146 unsigned int arm_kprobe : 1;
147};
148
149static int swap_instruction(void *data)
150{
151 struct swap_insn_args *args = data;
152 struct ftrace_insn new_insn, *insn;
153 struct kprobe *p = args->p;
154 size_t len;
155
156 new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
157 len = sizeof(new_insn.opc);
158 if (!p->ainsn.is_ftrace_insn)
159 goto skip_ftrace;
160 len = sizeof(new_insn);
161 insn = (struct ftrace_insn *) p->addr;
162 if (args->arm_kprobe) {
163 if (is_ftrace_nop(insn))
164 new_insn.disp = KPROBE_ON_FTRACE_NOP;
165 else
166 new_insn.disp = KPROBE_ON_FTRACE_CALL;
167 } else {
168 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
169 if (insn->disp == KPROBE_ON_FTRACE_NOP)
170 ftrace_generate_nop_insn(&new_insn);
171 }
172skip_ftrace:
173 s390_kernel_write(p->addr, &new_insn, len);
174 return 0;
175}
176NOKPROBE_SYMBOL(swap_instruction);
177
178void arch_arm_kprobe(struct kprobe *p)
179{
180 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
181
182 stop_machine_cpuslocked(swap_instruction, &args, NULL);
183}
184NOKPROBE_SYMBOL(arch_arm_kprobe);
185
186void arch_disarm_kprobe(struct kprobe *p)
187{
188 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
189
190 stop_machine_cpuslocked(swap_instruction, &args, NULL);
191}
192NOKPROBE_SYMBOL(arch_disarm_kprobe);
193
194void arch_remove_kprobe(struct kprobe *p)
195{
196 s390_free_insn_slot(p);
197}
198NOKPROBE_SYMBOL(arch_remove_kprobe);
199
200static void enable_singlestep(struct kprobe_ctlblk *kcb,
201 struct pt_regs *regs,
202 unsigned long ip)
203{
204 struct per_regs per_kprobe;
205
206 /* Set up the PER control registers %cr9-%cr11 */
207 per_kprobe.control = PER_EVENT_IFETCH;
208 per_kprobe.start = ip;
209 per_kprobe.end = ip;
210
211 /* Save control regs and psw mask */
212 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
213 kcb->kprobe_saved_imask = regs->psw.mask &
214 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
215
216 /* Set PER control regs, turns on single step for the given address */
217 __ctl_load(per_kprobe, 9, 11);
218 regs->psw.mask |= PSW_MASK_PER;
219 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
220 regs->psw.addr = ip;
221}
222NOKPROBE_SYMBOL(enable_singlestep);
223
224static void disable_singlestep(struct kprobe_ctlblk *kcb,
225 struct pt_regs *regs,
226 unsigned long ip)
227{
228 /* Restore control regs and psw mask, set new psw address */
229 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
230 regs->psw.mask &= ~PSW_MASK_PER;
231 regs->psw.mask |= kcb->kprobe_saved_imask;
232 regs->psw.addr = ip;
233}
234NOKPROBE_SYMBOL(disable_singlestep);
235
236/*
237 * Activate a kprobe by storing its pointer to current_kprobe. The
238 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
239 * two kprobes can be active, see KPROBE_REENTER.
240 */
241static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
242{
243 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
244 kcb->prev_kprobe.status = kcb->kprobe_status;
245 __this_cpu_write(current_kprobe, p);
246}
247NOKPROBE_SYMBOL(push_kprobe);
248
249/*
250 * Deactivate a kprobe by backing up to the previous state. If the
251 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
252 * for any other state prev_kprobe.kp will be NULL.
253 */
254static void pop_kprobe(struct kprobe_ctlblk *kcb)
255{
256 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
257 kcb->kprobe_status = kcb->prev_kprobe.status;
258}
259NOKPROBE_SYMBOL(pop_kprobe);
260
261void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
262{
263 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
264
265 /* Replace the return addr with trampoline addr */
266 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
267}
268NOKPROBE_SYMBOL(arch_prepare_kretprobe);
269
270static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
271{
272 switch (kcb->kprobe_status) {
273 case KPROBE_HIT_SSDONE:
274 case KPROBE_HIT_ACTIVE:
275 kprobes_inc_nmissed_count(p);
276 break;
277 case KPROBE_HIT_SS:
278 case KPROBE_REENTER:
279 default:
280 /*
281 * A kprobe on the code path to single step an instruction
282 * is a BUG. The code path resides in the .kprobes.text
283 * section and is executed with interrupts disabled.
284 */
285 pr_err("Invalid kprobe detected.\n");
286 dump_kprobe(p);
287 BUG();
288 }
289}
290NOKPROBE_SYMBOL(kprobe_reenter_check);
291
292static int kprobe_handler(struct pt_regs *regs)
293{
294 struct kprobe_ctlblk *kcb;
295 struct kprobe *p;
296
297 /*
298 * We want to disable preemption for the entire duration of kprobe
299 * processing. That includes the calls to the pre/post handlers
300 * and single stepping the kprobe instruction.
301 */
302 preempt_disable();
303 kcb = get_kprobe_ctlblk();
304 p = get_kprobe((void *)(regs->psw.addr - 2));
305
306 if (p) {
307 if (kprobe_running()) {
308 /*
309 * We have hit a kprobe while another is still
310 * active. This can happen in the pre and post
311 * handler. Single step the instruction of the
312 * new probe but do not call any handler function
313 * of this secondary kprobe.
314 * push_kprobe and pop_kprobe saves and restores
315 * the currently active kprobe.
316 */
317 kprobe_reenter_check(kcb, p);
318 push_kprobe(kcb, p);
319 kcb->kprobe_status = KPROBE_REENTER;
320 } else {
321 /*
322 * If we have no pre-handler or it returned 0, we
323 * continue with single stepping. If we have a
324 * pre-handler and it returned non-zero, it prepped
325 * for changing execution path, so get out doing
326 * nothing 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 pop_kprobe(kcb);
332 preempt_enable_no_resched();
333 return 1;
334 }
335 kcb->kprobe_status = KPROBE_HIT_SS;
336 }
337 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
338 return 1;
339 } /* else:
340 * No kprobe at this address and no active kprobe. The trap has
341 * not been caused by a kprobe breakpoint. The race of breakpoint
342 * vs. kprobe remove does not exist because on s390 as we use
343 * stop_machine to arm/disarm the breakpoints.
344 */
345 preempt_enable_no_resched();
346 return 0;
347}
348NOKPROBE_SYMBOL(kprobe_handler);
349
350/*
351 * Function return probe trampoline:
352 * - init_kprobes() establishes a probepoint here
353 * - When the probed function returns, this probe
354 * causes the handlers to fire
355 */
356static void __used kretprobe_trampoline_holder(void)
357{
358 asm volatile(".global kretprobe_trampoline\n"
359 "kretprobe_trampoline: bcr 0,0\n");
360}
361
362/*
363 * Called when the probe at kretprobe trampoline is hit
364 */
365static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
366{
367 struct kretprobe_instance *ri;
368 struct hlist_head *head, empty_rp;
369 struct hlist_node *tmp;
370 unsigned long flags, orig_ret_address;
371 unsigned long trampoline_address;
372 kprobe_opcode_t *correct_ret_addr;
373
374 INIT_HLIST_HEAD(&empty_rp);
375 kretprobe_hash_lock(current, &head, &flags);
376
377 /*
378 * It is possible to have multiple instances associated with a given
379 * task either because an multiple functions in the call path
380 * have a return probe installed on them, and/or more than one return
381 * return probe was registered for a target function.
382 *
383 * We can handle this because:
384 * - instances are always inserted at the head of the list
385 * - when multiple return probes are registered for the same
386 * function, the first instance's ret_addr will point to the
387 * real return address, and all the rest will point to
388 * kretprobe_trampoline
389 */
390 ri = NULL;
391 orig_ret_address = 0;
392 correct_ret_addr = NULL;
393 trampoline_address = (unsigned long) &kretprobe_trampoline;
394 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
395 if (ri->task != current)
396 /* another task is sharing our hash bucket */
397 continue;
398
399 orig_ret_address = (unsigned long) ri->ret_addr;
400
401 if (orig_ret_address != trampoline_address)
402 /*
403 * This is the real return address. Any other
404 * instances associated with this task are for
405 * other calls deeper on the call stack
406 */
407 break;
408 }
409
410 kretprobe_assert(ri, orig_ret_address, trampoline_address);
411
412 correct_ret_addr = ri->ret_addr;
413 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
414 if (ri->task != current)
415 /* another task is sharing our hash bucket */
416 continue;
417
418 orig_ret_address = (unsigned long) ri->ret_addr;
419
420 if (ri->rp && ri->rp->handler) {
421 ri->ret_addr = correct_ret_addr;
422 ri->rp->handler(ri, regs);
423 }
424
425 recycle_rp_inst(ri, &empty_rp);
426
427 if (orig_ret_address != trampoline_address)
428 /*
429 * This is the real return address. Any other
430 * instances associated with this task are for
431 * other calls deeper on the call stack
432 */
433 break;
434 }
435
436 regs->psw.addr = orig_ret_address;
437
438 kretprobe_hash_unlock(current, &flags);
439
440 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
441 hlist_del(&ri->hlist);
442 kfree(ri);
443 }
444 /*
445 * By returning a non-zero value, we are telling
446 * kprobe_handler() that we don't want the post_handler
447 * to run (and have re-enabled preemption)
448 */
449 return 1;
450}
451NOKPROBE_SYMBOL(trampoline_probe_handler);
452
453/*
454 * Called after single-stepping. p->addr is the address of the
455 * instruction whose first byte has been replaced by the "breakpoint"
456 * instruction. To avoid the SMP problems that can occur when we
457 * temporarily put back the original opcode to single-step, we
458 * single-stepped a copy of the instruction. The address of this
459 * copy is p->ainsn.insn.
460 */
461static void resume_execution(struct kprobe *p, struct pt_regs *regs)
462{
463 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
464 unsigned long ip = regs->psw.addr;
465 int fixup = probe_get_fixup_type(p->ainsn.insn);
466
467 /* Check if the kprobes location is an enabled ftrace caller */
468 if (p->ainsn.is_ftrace_insn) {
469 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
470 struct ftrace_insn call_insn;
471
472 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
473 /*
474 * A kprobe on an enabled ftrace call site actually single
475 * stepped an unconditional branch (ftrace nop equivalent).
476 * Now we need to fixup things and pretend that a brasl r0,...
477 * was executed instead.
478 */
479 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
480 ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
481 regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
482 }
483 }
484
485 if (fixup & FIXUP_PSW_NORMAL)
486 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
487
488 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
489 int ilen = insn_length(p->ainsn.insn[0] >> 8);
490 if (ip - (unsigned long) p->ainsn.insn == ilen)
491 ip = (unsigned long) p->addr + ilen;
492 }
493
494 if (fixup & FIXUP_RETURN_REGISTER) {
495 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
496 regs->gprs[reg] += (unsigned long) p->addr -
497 (unsigned long) p->ainsn.insn;
498 }
499
500 disable_singlestep(kcb, regs, ip);
501}
502NOKPROBE_SYMBOL(resume_execution);
503
504static int post_kprobe_handler(struct pt_regs *regs)
505{
506 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
507 struct kprobe *p = kprobe_running();
508
509 if (!p)
510 return 0;
511
512 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
513 kcb->kprobe_status = KPROBE_HIT_SSDONE;
514 p->post_handler(p, regs, 0);
515 }
516
517 resume_execution(p, regs);
518 pop_kprobe(kcb);
519 preempt_enable_no_resched();
520
521 /*
522 * if somebody else is singlestepping across a probe point, psw mask
523 * will have PER set, in which case, continue the remaining processing
524 * of do_single_step, as if this is not a probe hit.
525 */
526 if (regs->psw.mask & PSW_MASK_PER)
527 return 0;
528
529 return 1;
530}
531NOKPROBE_SYMBOL(post_kprobe_handler);
532
533static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
534{
535 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
536 struct kprobe *p = kprobe_running();
537 const struct exception_table_entry *entry;
538
539 switch(kcb->kprobe_status) {
540 case KPROBE_HIT_SS:
541 case KPROBE_REENTER:
542 /*
543 * We are here because the instruction being single
544 * stepped caused a page fault. We reset the current
545 * kprobe and the nip points back to the probe address
546 * and allow the page fault handler to continue as a
547 * normal page fault.
548 */
549 disable_singlestep(kcb, regs, (unsigned long) p->addr);
550 pop_kprobe(kcb);
551 preempt_enable_no_resched();
552 break;
553 case KPROBE_HIT_ACTIVE:
554 case KPROBE_HIT_SSDONE:
555 /*
556 * We increment the nmissed count for accounting,
557 * we can also use npre/npostfault count for accounting
558 * these specific fault cases.
559 */
560 kprobes_inc_nmissed_count(p);
561
562 /*
563 * We come here because instructions in the pre/post
564 * handler caused the page_fault, this could happen
565 * if handler tries to access user space by
566 * copy_from_user(), get_user() etc. Let the
567 * user-specified handler try to fix it first.
568 */
569 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
570 return 1;
571
572 /*
573 * In case the user-specified fault handler returned
574 * zero, try to fix up.
575 */
576 entry = s390_search_extables(regs->psw.addr);
577 if (entry) {
578 regs->psw.addr = extable_fixup(entry);
579 return 1;
580 }
581
582 /*
583 * fixup_exception() could not handle it,
584 * Let do_page_fault() fix it.
585 */
586 break;
587 default:
588 break;
589 }
590 return 0;
591}
592NOKPROBE_SYMBOL(kprobe_trap_handler);
593
594int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
595{
596 int ret;
597
598 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
599 local_irq_disable();
600 ret = kprobe_trap_handler(regs, trapnr);
601 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
602 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
603 return ret;
604}
605NOKPROBE_SYMBOL(kprobe_fault_handler);
606
607/*
608 * Wrapper routine to for handling exceptions.
609 */
610int kprobe_exceptions_notify(struct notifier_block *self,
611 unsigned long val, void *data)
612{
613 struct die_args *args = (struct die_args *) data;
614 struct pt_regs *regs = args->regs;
615 int ret = NOTIFY_DONE;
616
617 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
618 local_irq_disable();
619
620 switch (val) {
621 case DIE_BPT:
622 if (kprobe_handler(regs))
623 ret = NOTIFY_STOP;
624 break;
625 case DIE_SSTEP:
626 if (post_kprobe_handler(regs))
627 ret = NOTIFY_STOP;
628 break;
629 case DIE_TRAP:
630 if (!preemptible() && kprobe_running() &&
631 kprobe_trap_handler(regs, args->trapnr))
632 ret = NOTIFY_STOP;
633 break;
634 default:
635 break;
636 }
637
638 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
639 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
640
641 return ret;
642}
643NOKPROBE_SYMBOL(kprobe_exceptions_notify);
644
645static struct kprobe trampoline = {
646 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
647 .pre_handler = trampoline_probe_handler
648};
649
650int __init arch_init_kprobes(void)
651{
652 return register_kprobe(&trampoline);
653}
654
655int arch_trampoline_kprobe(struct kprobe *p)
656{
657 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
658}
659NOKPROBE_SYMBOL(arch_trampoline_kprobe);