Loading...
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/*
2 * Kernel Probes (KProbes)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright IBM Corp. 2002, 2006
19 *
20 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
21 */
22
23#include <linux/kprobes.h>
24#include <linux/ptrace.h>
25#include <linux/preempt.h>
26#include <linux/stop_machine.h>
27#include <linux/kdebug.h>
28#include <linux/uaccess.h>
29#include <linux/module.h>
30#include <linux/slab.h>
31#include <linux/hardirq.h>
32#include <linux/ftrace.h>
33#include <asm/cacheflush.h>
34#include <asm/sections.h>
35#include <asm/dis.h>
36
37DEFINE_PER_CPU(struct kprobe *, current_kprobe);
38DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
39
40struct kretprobe_blackpoint kretprobe_blacklist[] = { };
41
42DEFINE_INSN_CACHE_OPS(dmainsn);
43
44static void *alloc_dmainsn_page(void)
45{
46 return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
47}
48
49static void free_dmainsn_page(void *page)
50{
51 free_page((unsigned long)page);
52}
53
54struct kprobe_insn_cache kprobe_dmainsn_slots = {
55 .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
56 .alloc = alloc_dmainsn_page,
57 .free = free_dmainsn_page,
58 .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
59 .insn_size = MAX_INSN_SIZE,
60};
61
62static void copy_instruction(struct kprobe *p)
63{
64 unsigned long ip = (unsigned long) p->addr;
65 s64 disp, new_disp;
66 u64 addr, new_addr;
67
68 if (ftrace_location(ip) == ip) {
69 /*
70 * If kprobes patches the instruction that is morphed by
71 * ftrace make sure that kprobes always sees the branch
72 * "jg .+24" that skips the mcount block or the "brcl 0,0"
73 * in case of hotpatch.
74 */
75 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
76 p->ainsn.is_ftrace_insn = 1;
77 } else
78 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
79 p->opcode = p->ainsn.insn[0];
80 if (!probe_is_insn_relative_long(p->ainsn.insn))
81 return;
82 /*
83 * For pc-relative instructions in RIL-b or RIL-c format patch the
84 * RI2 displacement field. We have already made sure that the insn
85 * slot for the patched instruction is within the same 2GB area
86 * as the original instruction (either kernel image or module area).
87 * Therefore the new displacement will always fit.
88 */
89 disp = *(s32 *)&p->ainsn.insn[1];
90 addr = (u64)(unsigned long)p->addr;
91 new_addr = (u64)(unsigned long)p->ainsn.insn;
92 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
93 *(s32 *)&p->ainsn.insn[1] = new_disp;
94}
95NOKPROBE_SYMBOL(copy_instruction);
96
97static inline int is_kernel_addr(void *addr)
98{
99 return addr < (void *)_end;
100}
101
102static int s390_get_insn_slot(struct kprobe *p)
103{
104 /*
105 * Get an insn slot that is within the same 2GB area like the original
106 * instruction. That way instructions with a 32bit signed displacement
107 * field can be patched and executed within the insn slot.
108 */
109 p->ainsn.insn = NULL;
110 if (is_kernel_addr(p->addr))
111 p->ainsn.insn = get_dmainsn_slot();
112 else if (is_module_addr(p->addr))
113 p->ainsn.insn = get_insn_slot();
114 return p->ainsn.insn ? 0 : -ENOMEM;
115}
116NOKPROBE_SYMBOL(s390_get_insn_slot);
117
118static void s390_free_insn_slot(struct kprobe *p)
119{
120 if (!p->ainsn.insn)
121 return;
122 if (is_kernel_addr(p->addr))
123 free_dmainsn_slot(p->ainsn.insn, 0);
124 else
125 free_insn_slot(p->ainsn.insn, 0);
126 p->ainsn.insn = NULL;
127}
128NOKPROBE_SYMBOL(s390_free_insn_slot);
129
130int arch_prepare_kprobe(struct kprobe *p)
131{
132 if ((unsigned long) p->addr & 0x01)
133 return -EINVAL;
134 /* Make sure the probe isn't going on a difficult instruction */
135 if (probe_is_prohibited_opcode(p->addr))
136 return -EINVAL;
137 if (s390_get_insn_slot(p))
138 return -ENOMEM;
139 copy_instruction(p);
140 return 0;
141}
142NOKPROBE_SYMBOL(arch_prepare_kprobe);
143
144int arch_check_ftrace_location(struct kprobe *p)
145{
146 return 0;
147}
148
149struct swap_insn_args {
150 struct kprobe *p;
151 unsigned int arm_kprobe : 1;
152};
153
154static int swap_instruction(void *data)
155{
156 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
157 unsigned long status = kcb->kprobe_status;
158 struct swap_insn_args *args = data;
159 struct ftrace_insn new_insn, *insn;
160 struct kprobe *p = args->p;
161 size_t len;
162
163 new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
164 len = sizeof(new_insn.opc);
165 if (!p->ainsn.is_ftrace_insn)
166 goto skip_ftrace;
167 len = sizeof(new_insn);
168 insn = (struct ftrace_insn *) p->addr;
169 if (args->arm_kprobe) {
170 if (is_ftrace_nop(insn))
171 new_insn.disp = KPROBE_ON_FTRACE_NOP;
172 else
173 new_insn.disp = KPROBE_ON_FTRACE_CALL;
174 } else {
175 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
176 if (insn->disp == KPROBE_ON_FTRACE_NOP)
177 ftrace_generate_nop_insn(&new_insn);
178 }
179skip_ftrace:
180 kcb->kprobe_status = KPROBE_SWAP_INST;
181 s390_kernel_write(p->addr, &new_insn, len);
182 kcb->kprobe_status = status;
183 return 0;
184}
185NOKPROBE_SYMBOL(swap_instruction);
186
187void arch_arm_kprobe(struct kprobe *p)
188{
189 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
190
191 stop_machine(swap_instruction, &args, NULL);
192}
193NOKPROBE_SYMBOL(arch_arm_kprobe);
194
195void arch_disarm_kprobe(struct kprobe *p)
196{
197 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
198
199 stop_machine(swap_instruction, &args, NULL);
200}
201NOKPROBE_SYMBOL(arch_disarm_kprobe);
202
203void arch_remove_kprobe(struct kprobe *p)
204{
205 s390_free_insn_slot(p);
206}
207NOKPROBE_SYMBOL(arch_remove_kprobe);
208
209static void enable_singlestep(struct kprobe_ctlblk *kcb,
210 struct pt_regs *regs,
211 unsigned long ip)
212{
213 struct per_regs per_kprobe;
214
215 /* Set up the PER control registers %cr9-%cr11 */
216 per_kprobe.control = PER_EVENT_IFETCH;
217 per_kprobe.start = ip;
218 per_kprobe.end = ip;
219
220 /* Save control regs and psw mask */
221 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
222 kcb->kprobe_saved_imask = regs->psw.mask &
223 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
224
225 /* Set PER control regs, turns on single step for the given address */
226 __ctl_load(per_kprobe, 9, 11);
227 regs->psw.mask |= PSW_MASK_PER;
228 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
229 regs->psw.addr = ip;
230}
231NOKPROBE_SYMBOL(enable_singlestep);
232
233static void disable_singlestep(struct kprobe_ctlblk *kcb,
234 struct pt_regs *regs,
235 unsigned long ip)
236{
237 /* Restore control regs and psw mask, set new psw address */
238 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
239 regs->psw.mask &= ~PSW_MASK_PER;
240 regs->psw.mask |= kcb->kprobe_saved_imask;
241 regs->psw.addr = ip;
242}
243NOKPROBE_SYMBOL(disable_singlestep);
244
245/*
246 * Activate a kprobe by storing its pointer to current_kprobe. The
247 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
248 * two kprobes can be active, see KPROBE_REENTER.
249 */
250static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
251{
252 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
253 kcb->prev_kprobe.status = kcb->kprobe_status;
254 __this_cpu_write(current_kprobe, p);
255}
256NOKPROBE_SYMBOL(push_kprobe);
257
258/*
259 * Deactivate a kprobe by backing up to the previous state. If the
260 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
261 * for any other state prev_kprobe.kp will be NULL.
262 */
263static void pop_kprobe(struct kprobe_ctlblk *kcb)
264{
265 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
266 kcb->kprobe_status = kcb->prev_kprobe.status;
267}
268NOKPROBE_SYMBOL(pop_kprobe);
269
270void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
271{
272 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
273
274 /* Replace the return addr with trampoline addr */
275 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
276}
277NOKPROBE_SYMBOL(arch_prepare_kretprobe);
278
279static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
280{
281 switch (kcb->kprobe_status) {
282 case KPROBE_HIT_SSDONE:
283 case KPROBE_HIT_ACTIVE:
284 kprobes_inc_nmissed_count(p);
285 break;
286 case KPROBE_HIT_SS:
287 case KPROBE_REENTER:
288 default:
289 /*
290 * A kprobe on the code path to single step an instruction
291 * is a BUG. The code path resides in the .kprobes.text
292 * section and is executed with interrupts disabled.
293 */
294 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
295 dump_kprobe(p);
296 BUG();
297 }
298}
299NOKPROBE_SYMBOL(kprobe_reenter_check);
300
301static int kprobe_handler(struct pt_regs *regs)
302{
303 struct kprobe_ctlblk *kcb;
304 struct kprobe *p;
305
306 /*
307 * We want to disable preemption for the entire duration of kprobe
308 * processing. That includes the calls to the pre/post handlers
309 * and single stepping the kprobe instruction.
310 */
311 preempt_disable();
312 kcb = get_kprobe_ctlblk();
313 p = get_kprobe((void *)(regs->psw.addr - 2));
314
315 if (p) {
316 if (kprobe_running()) {
317 /*
318 * We have hit a kprobe while another is still
319 * active. This can happen in the pre and post
320 * handler. Single step the instruction of the
321 * new probe but do not call any handler function
322 * of this secondary kprobe.
323 * push_kprobe and pop_kprobe saves and restores
324 * the currently active kprobe.
325 */
326 kprobe_reenter_check(kcb, p);
327 push_kprobe(kcb, p);
328 kcb->kprobe_status = KPROBE_REENTER;
329 } else {
330 /*
331 * If we have no pre-handler or it returned 0, we
332 * continue with single stepping. If we have a
333 * pre-handler and it returned non-zero, it prepped
334 * for calling the break_handler below on re-entry
335 * for jprobe processing, so get out doing nothing
336 * more here.
337 */
338 push_kprobe(kcb, p);
339 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
340 if (p->pre_handler && p->pre_handler(p, regs))
341 return 1;
342 kcb->kprobe_status = KPROBE_HIT_SS;
343 }
344 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
345 return 1;
346 } else if (kprobe_running()) {
347 p = __this_cpu_read(current_kprobe);
348 if (p->break_handler && p->break_handler(p, regs)) {
349 /*
350 * Continuation after the jprobe completed and
351 * caused the jprobe_return trap. The jprobe
352 * break_handler "returns" to the original
353 * function that still has the kprobe breakpoint
354 * installed. We continue with single stepping.
355 */
356 kcb->kprobe_status = KPROBE_HIT_SS;
357 enable_singlestep(kcb, regs,
358 (unsigned long) p->ainsn.insn);
359 return 1;
360 } /* else:
361 * No kprobe at this address and the current kprobe
362 * has no break handler (no jprobe!). The kernel just
363 * exploded, let the standard trap handler pick up the
364 * pieces.
365 */
366 } /* else:
367 * No kprobe at this address and no active kprobe. The trap has
368 * not been caused by a kprobe breakpoint. The race of breakpoint
369 * vs. kprobe remove does not exist because on s390 as we use
370 * stop_machine to arm/disarm the breakpoints.
371 */
372 preempt_enable_no_resched();
373 return 0;
374}
375NOKPROBE_SYMBOL(kprobe_handler);
376
377/*
378 * Function return probe trampoline:
379 * - init_kprobes() establishes a probepoint here
380 * - When the probed function returns, this probe
381 * causes the handlers to fire
382 */
383static void __used kretprobe_trampoline_holder(void)
384{
385 asm volatile(".global kretprobe_trampoline\n"
386 "kretprobe_trampoline: bcr 0,0\n");
387}
388
389/*
390 * Called when the probe at kretprobe trampoline is hit
391 */
392static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
393{
394 struct kretprobe_instance *ri;
395 struct hlist_head *head, empty_rp;
396 struct hlist_node *tmp;
397 unsigned long flags, orig_ret_address;
398 unsigned long trampoline_address;
399 kprobe_opcode_t *correct_ret_addr;
400
401 INIT_HLIST_HEAD(&empty_rp);
402 kretprobe_hash_lock(current, &head, &flags);
403
404 /*
405 * It is possible to have multiple instances associated with a given
406 * task either because an multiple functions in the call path
407 * have a return probe installed on them, and/or more than one return
408 * return probe was registered for a target function.
409 *
410 * We can handle this because:
411 * - instances are always inserted at the head of the list
412 * - when multiple return probes are registered for the same
413 * function, the first instance's ret_addr will point to the
414 * real return address, and all the rest will point to
415 * kretprobe_trampoline
416 */
417 ri = NULL;
418 orig_ret_address = 0;
419 correct_ret_addr = NULL;
420 trampoline_address = (unsigned long) &kretprobe_trampoline;
421 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
422 if (ri->task != current)
423 /* another task is sharing our hash bucket */
424 continue;
425
426 orig_ret_address = (unsigned long) ri->ret_addr;
427
428 if (orig_ret_address != trampoline_address)
429 /*
430 * This is the real return address. Any other
431 * instances associated with this task are for
432 * other calls deeper on the call stack
433 */
434 break;
435 }
436
437 kretprobe_assert(ri, orig_ret_address, trampoline_address);
438
439 correct_ret_addr = ri->ret_addr;
440 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
441 if (ri->task != current)
442 /* another task is sharing our hash bucket */
443 continue;
444
445 orig_ret_address = (unsigned long) ri->ret_addr;
446
447 if (ri->rp && ri->rp->handler) {
448 ri->ret_addr = correct_ret_addr;
449 ri->rp->handler(ri, regs);
450 }
451
452 recycle_rp_inst(ri, &empty_rp);
453
454 if (orig_ret_address != trampoline_address)
455 /*
456 * This is the real return address. Any other
457 * instances associated with this task are for
458 * other calls deeper on the call stack
459 */
460 break;
461 }
462
463 regs->psw.addr = orig_ret_address;
464
465 pop_kprobe(get_kprobe_ctlblk());
466 kretprobe_hash_unlock(current, &flags);
467 preempt_enable_no_resched();
468
469 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
470 hlist_del(&ri->hlist);
471 kfree(ri);
472 }
473 /*
474 * By returning a non-zero value, we are telling
475 * kprobe_handler() that we don't want the post_handler
476 * to run (and have re-enabled preemption)
477 */
478 return 1;
479}
480NOKPROBE_SYMBOL(trampoline_probe_handler);
481
482/*
483 * Called after single-stepping. p->addr is the address of the
484 * instruction whose first byte has been replaced by the "breakpoint"
485 * instruction. To avoid the SMP problems that can occur when we
486 * temporarily put back the original opcode to single-step, we
487 * single-stepped a copy of the instruction. The address of this
488 * copy is p->ainsn.insn.
489 */
490static void resume_execution(struct kprobe *p, struct pt_regs *regs)
491{
492 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
493 unsigned long ip = regs->psw.addr;
494 int fixup = probe_get_fixup_type(p->ainsn.insn);
495
496 /* Check if the kprobes location is an enabled ftrace caller */
497 if (p->ainsn.is_ftrace_insn) {
498 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
499 struct ftrace_insn call_insn;
500
501 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
502 /*
503 * A kprobe on an enabled ftrace call site actually single
504 * stepped an unconditional branch (ftrace nop equivalent).
505 * Now we need to fixup things and pretend that a brasl r0,...
506 * was executed instead.
507 */
508 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
509 ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
510 regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
511 }
512 }
513
514 if (fixup & FIXUP_PSW_NORMAL)
515 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
516
517 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
518 int ilen = insn_length(p->ainsn.insn[0] >> 8);
519 if (ip - (unsigned long) p->ainsn.insn == ilen)
520 ip = (unsigned long) p->addr + ilen;
521 }
522
523 if (fixup & FIXUP_RETURN_REGISTER) {
524 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
525 regs->gprs[reg] += (unsigned long) p->addr -
526 (unsigned long) p->ainsn.insn;
527 }
528
529 disable_singlestep(kcb, regs, ip);
530}
531NOKPROBE_SYMBOL(resume_execution);
532
533static int post_kprobe_handler(struct pt_regs *regs)
534{
535 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
536 struct kprobe *p = kprobe_running();
537
538 if (!p)
539 return 0;
540
541 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
542 kcb->kprobe_status = KPROBE_HIT_SSDONE;
543 p->post_handler(p, regs, 0);
544 }
545
546 resume_execution(p, regs);
547 pop_kprobe(kcb);
548 preempt_enable_no_resched();
549
550 /*
551 * if somebody else is singlestepping across a probe point, psw mask
552 * will have PER set, in which case, continue the remaining processing
553 * of do_single_step, as if this is not a probe hit.
554 */
555 if (regs->psw.mask & PSW_MASK_PER)
556 return 0;
557
558 return 1;
559}
560NOKPROBE_SYMBOL(post_kprobe_handler);
561
562static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
563{
564 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
565 struct kprobe *p = kprobe_running();
566 const struct exception_table_entry *entry;
567
568 switch(kcb->kprobe_status) {
569 case KPROBE_SWAP_INST:
570 /* We are here because the instruction replacement failed */
571 return 0;
572 case KPROBE_HIT_SS:
573 case KPROBE_REENTER:
574 /*
575 * We are here because the instruction being single
576 * stepped caused a page fault. We reset the current
577 * kprobe and the nip points back to the probe address
578 * and allow the page fault handler to continue as a
579 * normal page fault.
580 */
581 disable_singlestep(kcb, regs, (unsigned long) p->addr);
582 pop_kprobe(kcb);
583 preempt_enable_no_resched();
584 break;
585 case KPROBE_HIT_ACTIVE:
586 case KPROBE_HIT_SSDONE:
587 /*
588 * We increment the nmissed count for accounting,
589 * we can also use npre/npostfault count for accounting
590 * these specific fault cases.
591 */
592 kprobes_inc_nmissed_count(p);
593
594 /*
595 * We come here because instructions in the pre/post
596 * handler caused the page_fault, this could happen
597 * if handler tries to access user space by
598 * copy_from_user(), get_user() etc. Let the
599 * user-specified handler try to fix it first.
600 */
601 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
602 return 1;
603
604 /*
605 * In case the user-specified fault handler returned
606 * zero, try to fix up.
607 */
608 entry = search_exception_tables(regs->psw.addr);
609 if (entry) {
610 regs->psw.addr = extable_fixup(entry);
611 return 1;
612 }
613
614 /*
615 * fixup_exception() could not handle it,
616 * Let do_page_fault() fix it.
617 */
618 break;
619 default:
620 break;
621 }
622 return 0;
623}
624NOKPROBE_SYMBOL(kprobe_trap_handler);
625
626int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
627{
628 int ret;
629
630 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
631 local_irq_disable();
632 ret = kprobe_trap_handler(regs, trapnr);
633 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
634 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
635 return ret;
636}
637NOKPROBE_SYMBOL(kprobe_fault_handler);
638
639/*
640 * Wrapper routine to for handling exceptions.
641 */
642int kprobe_exceptions_notify(struct notifier_block *self,
643 unsigned long val, void *data)
644{
645 struct die_args *args = (struct die_args *) data;
646 struct pt_regs *regs = args->regs;
647 int ret = NOTIFY_DONE;
648
649 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
650 local_irq_disable();
651
652 switch (val) {
653 case DIE_BPT:
654 if (kprobe_handler(regs))
655 ret = NOTIFY_STOP;
656 break;
657 case DIE_SSTEP:
658 if (post_kprobe_handler(regs))
659 ret = NOTIFY_STOP;
660 break;
661 case DIE_TRAP:
662 if (!preemptible() && kprobe_running() &&
663 kprobe_trap_handler(regs, args->trapnr))
664 ret = NOTIFY_STOP;
665 break;
666 default:
667 break;
668 }
669
670 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
671 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
672
673 return ret;
674}
675NOKPROBE_SYMBOL(kprobe_exceptions_notify);
676
677int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
678{
679 struct jprobe *jp = container_of(p, struct jprobe, kp);
680 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
681 unsigned long stack;
682
683 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
684
685 /* setup return addr to the jprobe handler routine */
686 regs->psw.addr = (unsigned long) jp->entry;
687 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
688
689 /* r15 is the stack pointer */
690 stack = (unsigned long) regs->gprs[15];
691
692 memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
693 return 1;
694}
695NOKPROBE_SYMBOL(setjmp_pre_handler);
696
697void jprobe_return(void)
698{
699 asm volatile(".word 0x0002");
700}
701NOKPROBE_SYMBOL(jprobe_return);
702
703int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
704{
705 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
706 unsigned long stack;
707
708 stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
709
710 /* Put the regs back */
711 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
712 /* put the stack back */
713 memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
714 preempt_enable_no_resched();
715 return 1;
716}
717NOKPROBE_SYMBOL(longjmp_break_handler);
718
719static struct kprobe trampoline = {
720 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
721 .pre_handler = trampoline_probe_handler
722};
723
724int __init arch_init_kprobes(void)
725{
726 return register_kprobe(&trampoline);
727}
728
729int arch_trampoline_kprobe(struct kprobe *p)
730{
731 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
732}
733NOKPROBE_SYMBOL(arch_trampoline_kprobe);