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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/kprobes.h>
13#include <linux/ptrace.h>
14#include <linux/preempt.h>
15#include <linux/stop_machine.h>
16#include <linux/kdebug.h>
17#include <linux/uaccess.h>
18#include <linux/extable.h>
19#include <linux/module.h>
20#include <linux/slab.h>
21#include <linux/hardirq.h>
22#include <linux/ftrace.h>
23#include <linux/execmem.h>
24#include <asm/text-patching.h>
25#include <asm/set_memory.h>
26#include <asm/sections.h>
27#include <asm/dis.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
35void *alloc_insn_page(void)
36{
37 void *page;
38
39 page = execmem_alloc(EXECMEM_KPROBES, PAGE_SIZE);
40 if (!page)
41 return NULL;
42 set_memory_rox((unsigned long)page, 1);
43 return page;
44}
45
46static void copy_instruction(struct kprobe *p)
47{
48 kprobe_opcode_t insn[MAX_INSN_SIZE];
49 s64 disp, new_disp;
50 u64 addr, new_addr;
51 unsigned int len;
52
53 len = insn_length(*p->addr >> 8);
54 memcpy(&insn, p->addr, len);
55 p->opcode = insn[0];
56 if (probe_is_insn_relative_long(&insn[0])) {
57 /*
58 * For pc-relative instructions in RIL-b or RIL-c format patch
59 * the RI2 displacement field. The insn slot for the to be
60 * patched instruction is within the same 4GB area like the
61 * original instruction. Therefore the new displacement will
62 * always fit.
63 */
64 disp = *(s32 *)&insn[1];
65 addr = (u64)(unsigned long)p->addr;
66 new_addr = (u64)(unsigned long)p->ainsn.insn;
67 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
68 *(s32 *)&insn[1] = new_disp;
69 }
70 s390_kernel_write(p->ainsn.insn, &insn, len);
71}
72NOKPROBE_SYMBOL(copy_instruction);
73
74/* Check if paddr is at an instruction boundary */
75static bool can_probe(unsigned long paddr)
76{
77 unsigned long addr, offset = 0;
78 kprobe_opcode_t insn;
79 struct kprobe *kp;
80
81 if (paddr & 0x01)
82 return false;
83
84 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
85 return false;
86
87 /* Decode instructions */
88 addr = paddr - offset;
89 while (addr < paddr) {
90 if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
91 return false;
92
93 if (insn >> 8 == 0) {
94 if (insn != BREAKPOINT_INSTRUCTION) {
95 /*
96 * Note that QEMU inserts opcode 0x0000 to implement
97 * software breakpoints for guests. Since the size of
98 * the original instruction is unknown, stop following
99 * instructions and prevent setting a kprobe.
100 */
101 return false;
102 }
103 /*
104 * Check if the instruction has been modified by another
105 * kprobe, in which case the original instruction is
106 * decoded.
107 */
108 kp = get_kprobe((void *)addr);
109 if (!kp) {
110 /* not a kprobe */
111 return false;
112 }
113 insn = kp->opcode;
114 }
115 addr += insn_length(insn >> 8);
116 }
117 return addr == paddr;
118}
119
120int arch_prepare_kprobe(struct kprobe *p)
121{
122 if (!can_probe((unsigned long)p->addr))
123 return -EINVAL;
124 /* Make sure the probe isn't going on a difficult instruction */
125 if (probe_is_prohibited_opcode(p->addr))
126 return -EINVAL;
127 p->ainsn.insn = get_insn_slot();
128 if (!p->ainsn.insn)
129 return -ENOMEM;
130 copy_instruction(p);
131 return 0;
132}
133NOKPROBE_SYMBOL(arch_prepare_kprobe);
134
135struct swap_insn_args {
136 struct kprobe *p;
137 unsigned int arm_kprobe : 1;
138};
139
140static int swap_instruction(void *data)
141{
142 struct swap_insn_args *args = data;
143 struct kprobe *p = args->p;
144 u16 opc;
145
146 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
147 s390_kernel_write(p->addr, &opc, sizeof(opc));
148 return 0;
149}
150NOKPROBE_SYMBOL(swap_instruction);
151
152void arch_arm_kprobe(struct kprobe *p)
153{
154 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
155
156 if (MACHINE_HAS_SEQ_INSN) {
157 swap_instruction(&args);
158 text_poke_sync();
159 } else {
160 stop_machine_cpuslocked(swap_instruction, &args, NULL);
161 }
162}
163NOKPROBE_SYMBOL(arch_arm_kprobe);
164
165void arch_disarm_kprobe(struct kprobe *p)
166{
167 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
168
169 if (MACHINE_HAS_SEQ_INSN) {
170 swap_instruction(&args);
171 text_poke_sync();
172 } else {
173 stop_machine_cpuslocked(swap_instruction, &args, NULL);
174 }
175}
176NOKPROBE_SYMBOL(arch_disarm_kprobe);
177
178void arch_remove_kprobe(struct kprobe *p)
179{
180 if (!p->ainsn.insn)
181 return;
182 free_insn_slot(p->ainsn.insn, 0);
183 p->ainsn.insn = NULL;
184}
185NOKPROBE_SYMBOL(arch_remove_kprobe);
186
187static void enable_singlestep(struct kprobe_ctlblk *kcb,
188 struct pt_regs *regs,
189 unsigned long ip)
190{
191 union {
192 struct ctlreg regs[3];
193 struct {
194 struct ctlreg control;
195 struct ctlreg start;
196 struct ctlreg end;
197 };
198 } per_kprobe;
199
200 /* Set up the PER control registers %cr9-%cr11 */
201 per_kprobe.control.val = PER_EVENT_IFETCH;
202 per_kprobe.start.val = ip;
203 per_kprobe.end.val = ip;
204
205 /* Save control regs and psw mask */
206 __local_ctl_store(9, 11, kcb->kprobe_saved_ctl);
207 kcb->kprobe_saved_imask = regs->psw.mask &
208 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
209
210 /* Set PER control regs, turns on single step for the given address */
211 __local_ctl_load(9, 11, per_kprobe.regs);
212 regs->psw.mask |= PSW_MASK_PER;
213 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
214 regs->psw.addr = ip;
215}
216NOKPROBE_SYMBOL(enable_singlestep);
217
218static void disable_singlestep(struct kprobe_ctlblk *kcb,
219 struct pt_regs *regs,
220 unsigned long ip)
221{
222 /* Restore control regs and psw mask, set new psw address */
223 __local_ctl_load(9, 11, kcb->kprobe_saved_ctl);
224 regs->psw.mask &= ~PSW_MASK_PER;
225 regs->psw.mask |= kcb->kprobe_saved_imask;
226 regs->psw.addr = ip;
227}
228NOKPROBE_SYMBOL(disable_singlestep);
229
230/*
231 * Activate a kprobe by storing its pointer to current_kprobe. The
232 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
233 * two kprobes can be active, see KPROBE_REENTER.
234 */
235static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
236{
237 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
238 kcb->prev_kprobe.status = kcb->kprobe_status;
239 __this_cpu_write(current_kprobe, p);
240}
241NOKPROBE_SYMBOL(push_kprobe);
242
243/*
244 * Deactivate a kprobe by backing up to the previous state. If the
245 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
246 * for any other state prev_kprobe.kp will be NULL.
247 */
248static void pop_kprobe(struct kprobe_ctlblk *kcb)
249{
250 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
251 kcb->kprobe_status = kcb->prev_kprobe.status;
252 kcb->prev_kprobe.kp = NULL;
253}
254NOKPROBE_SYMBOL(pop_kprobe);
255
256static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
257{
258 switch (kcb->kprobe_status) {
259 case KPROBE_HIT_SSDONE:
260 case KPROBE_HIT_ACTIVE:
261 kprobes_inc_nmissed_count(p);
262 break;
263 case KPROBE_HIT_SS:
264 case KPROBE_REENTER:
265 default:
266 /*
267 * A kprobe on the code path to single step an instruction
268 * is a BUG. The code path resides in the .kprobes.text
269 * section and is executed with interrupts disabled.
270 */
271 pr_err("Failed to recover from reentered kprobes.\n");
272 dump_kprobe(p);
273 BUG();
274 }
275}
276NOKPROBE_SYMBOL(kprobe_reenter_check);
277
278static int kprobe_handler(struct pt_regs *regs)
279{
280 struct kprobe_ctlblk *kcb;
281 struct kprobe *p;
282
283 /*
284 * We want to disable preemption for the entire duration of kprobe
285 * processing. That includes the calls to the pre/post handlers
286 * and single stepping the kprobe instruction.
287 */
288 preempt_disable();
289 kcb = get_kprobe_ctlblk();
290 p = get_kprobe((void *)(regs->psw.addr - 2));
291
292 if (p) {
293 if (kprobe_running()) {
294 /*
295 * We have hit a kprobe while another is still
296 * active. This can happen in the pre and post
297 * handler. Single step the instruction of the
298 * new probe but do not call any handler function
299 * of this secondary kprobe.
300 * push_kprobe and pop_kprobe saves and restores
301 * the currently active kprobe.
302 */
303 kprobe_reenter_check(kcb, p);
304 push_kprobe(kcb, p);
305 kcb->kprobe_status = KPROBE_REENTER;
306 } else {
307 /*
308 * If we have no pre-handler or it returned 0, we
309 * continue with single stepping. If we have a
310 * pre-handler and it returned non-zero, it prepped
311 * for changing execution path, so get out doing
312 * nothing more here.
313 */
314 push_kprobe(kcb, p);
315 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
316 if (p->pre_handler && p->pre_handler(p, regs)) {
317 pop_kprobe(kcb);
318 preempt_enable_no_resched();
319 return 1;
320 }
321 kcb->kprobe_status = KPROBE_HIT_SS;
322 }
323 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
324 return 1;
325 } /* else:
326 * No kprobe at this address and no active kprobe. The trap has
327 * not been caused by a kprobe breakpoint. The race of breakpoint
328 * vs. kprobe remove does not exist because on s390 as we use
329 * stop_machine to arm/disarm the breakpoints.
330 */
331 preempt_enable_no_resched();
332 return 0;
333}
334NOKPROBE_SYMBOL(kprobe_handler);
335
336/*
337 * Called after single-stepping. p->addr is the address of the
338 * instruction whose first byte has been replaced by the "breakpoint"
339 * instruction. To avoid the SMP problems that can occur when we
340 * temporarily put back the original opcode to single-step, we
341 * single-stepped a copy of the instruction. The address of this
342 * copy is p->ainsn.insn.
343 */
344static void resume_execution(struct kprobe *p, struct pt_regs *regs)
345{
346 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
347 unsigned long ip = regs->psw.addr;
348 int fixup = probe_get_fixup_type(p->ainsn.insn);
349
350 if (fixup & FIXUP_PSW_NORMAL)
351 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
352
353 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
354 int ilen = insn_length(p->ainsn.insn[0] >> 8);
355 if (ip - (unsigned long) p->ainsn.insn == ilen)
356 ip = (unsigned long) p->addr + ilen;
357 }
358
359 if (fixup & FIXUP_RETURN_REGISTER) {
360 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
361 regs->gprs[reg] += (unsigned long) p->addr -
362 (unsigned long) p->ainsn.insn;
363 }
364
365 disable_singlestep(kcb, regs, ip);
366}
367NOKPROBE_SYMBOL(resume_execution);
368
369static int post_kprobe_handler(struct pt_regs *regs)
370{
371 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
372 struct kprobe *p = kprobe_running();
373
374 if (!p)
375 return 0;
376
377 resume_execution(p, regs);
378 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
379 kcb->kprobe_status = KPROBE_HIT_SSDONE;
380 p->post_handler(p, regs, 0);
381 }
382 pop_kprobe(kcb);
383 preempt_enable_no_resched();
384
385 /*
386 * if somebody else is singlestepping across a probe point, psw mask
387 * will have PER set, in which case, continue the remaining processing
388 * of do_single_step, as if this is not a probe hit.
389 */
390 if (regs->psw.mask & PSW_MASK_PER)
391 return 0;
392
393 return 1;
394}
395NOKPROBE_SYMBOL(post_kprobe_handler);
396
397static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
398{
399 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
400 struct kprobe *p = kprobe_running();
401
402 switch(kcb->kprobe_status) {
403 case KPROBE_HIT_SS:
404 case KPROBE_REENTER:
405 /*
406 * We are here because the instruction being single
407 * stepped caused a page fault. We reset the current
408 * kprobe and the nip points back to the probe address
409 * and allow the page fault handler to continue as a
410 * normal page fault.
411 */
412 disable_singlestep(kcb, regs, (unsigned long) p->addr);
413 pop_kprobe(kcb);
414 preempt_enable_no_resched();
415 break;
416 case KPROBE_HIT_ACTIVE:
417 case KPROBE_HIT_SSDONE:
418 /*
419 * In case the user-specified fault handler returned
420 * zero, try to fix up.
421 */
422 if (fixup_exception(regs))
423 return 1;
424 /*
425 * fixup_exception() could not handle it,
426 * Let do_page_fault() fix it.
427 */
428 break;
429 default:
430 break;
431 }
432 return 0;
433}
434NOKPROBE_SYMBOL(kprobe_trap_handler);
435
436int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
437{
438 int ret;
439
440 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
441 local_irq_disable();
442 ret = kprobe_trap_handler(regs, trapnr);
443 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
444 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
445 return ret;
446}
447NOKPROBE_SYMBOL(kprobe_fault_handler);
448
449/*
450 * Wrapper routine to for handling exceptions.
451 */
452int kprobe_exceptions_notify(struct notifier_block *self,
453 unsigned long val, void *data)
454{
455 struct die_args *args = (struct die_args *) data;
456 struct pt_regs *regs = args->regs;
457 int ret = NOTIFY_DONE;
458
459 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
460 local_irq_disable();
461
462 switch (val) {
463 case DIE_BPT:
464 if (kprobe_handler(regs))
465 ret = NOTIFY_STOP;
466 break;
467 case DIE_SSTEP:
468 if (post_kprobe_handler(regs))
469 ret = NOTIFY_STOP;
470 break;
471 case DIE_TRAP:
472 if (!preemptible() && kprobe_running() &&
473 kprobe_trap_handler(regs, args->trapnr))
474 ret = NOTIFY_STOP;
475 break;
476 default:
477 break;
478 }
479
480 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
481 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
482
483 return ret;
484}
485NOKPROBE_SYMBOL(kprobe_exceptions_notify);
486
487int __init arch_init_kprobes(void)
488{
489 return 0;
490}
491
492int __init arch_populate_kprobe_blacklist(void)
493{
494 return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
495 (unsigned long)__irqentry_text_end);
496}
497
498int arch_trampoline_kprobe(struct kprobe *p)
499{
500 return 0;
501}
502NOKPROBE_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/extable.h>
30#include <linux/module.h>
31#include <linux/slab.h>
32#include <linux/hardirq.h>
33#include <linux/ftrace.h>
34#include <asm/cacheflush.h>
35#include <asm/sections.h>
36#include <linux/uaccess.h>
37#include <asm/dis.h>
38
39DEFINE_PER_CPU(struct kprobe *, current_kprobe);
40DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
41
42struct kretprobe_blackpoint kretprobe_blacklist[] = { };
43
44DEFINE_INSN_CACHE_OPS(dmainsn);
45
46static void *alloc_dmainsn_page(void)
47{
48 return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
49}
50
51static void free_dmainsn_page(void *page)
52{
53 free_page((unsigned long)page);
54}
55
56struct kprobe_insn_cache kprobe_dmainsn_slots = {
57 .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
58 .alloc = alloc_dmainsn_page,
59 .free = free_dmainsn_page,
60 .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
61 .insn_size = MAX_INSN_SIZE,
62};
63
64static void copy_instruction(struct kprobe *p)
65{
66 unsigned long ip = (unsigned long) p->addr;
67 s64 disp, new_disp;
68 u64 addr, new_addr;
69
70 if (ftrace_location(ip) == ip) {
71 /*
72 * If kprobes patches the instruction that is morphed by
73 * ftrace make sure that kprobes always sees the branch
74 * "jg .+24" that skips the mcount block or the "brcl 0,0"
75 * in case of hotpatch.
76 */
77 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
78 p->ainsn.is_ftrace_insn = 1;
79 } else
80 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
81 p->opcode = p->ainsn.insn[0];
82 if (!probe_is_insn_relative_long(p->ainsn.insn))
83 return;
84 /*
85 * For pc-relative instructions in RIL-b or RIL-c format patch the
86 * RI2 displacement field. We have already made sure that the insn
87 * slot for the patched instruction is within the same 2GB area
88 * as the original instruction (either kernel image or module area).
89 * Therefore the new displacement will always fit.
90 */
91 disp = *(s32 *)&p->ainsn.insn[1];
92 addr = (u64)(unsigned long)p->addr;
93 new_addr = (u64)(unsigned long)p->ainsn.insn;
94 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
95 *(s32 *)&p->ainsn.insn[1] = new_disp;
96}
97NOKPROBE_SYMBOL(copy_instruction);
98
99static inline int is_kernel_addr(void *addr)
100{
101 return addr < (void *)_end;
102}
103
104static int s390_get_insn_slot(struct kprobe *p)
105{
106 /*
107 * Get an insn slot that is within the same 2GB area like the original
108 * instruction. That way instructions with a 32bit signed displacement
109 * field can be patched and executed within the insn slot.
110 */
111 p->ainsn.insn = NULL;
112 if (is_kernel_addr(p->addr))
113 p->ainsn.insn = get_dmainsn_slot();
114 else if (is_module_addr(p->addr))
115 p->ainsn.insn = get_insn_slot();
116 return p->ainsn.insn ? 0 : -ENOMEM;
117}
118NOKPROBE_SYMBOL(s390_get_insn_slot);
119
120static void s390_free_insn_slot(struct kprobe *p)
121{
122 if (!p->ainsn.insn)
123 return;
124 if (is_kernel_addr(p->addr))
125 free_dmainsn_slot(p->ainsn.insn, 0);
126 else
127 free_insn_slot(p->ainsn.insn, 0);
128 p->ainsn.insn = NULL;
129}
130NOKPROBE_SYMBOL(s390_free_insn_slot);
131
132int arch_prepare_kprobe(struct kprobe *p)
133{
134 if ((unsigned long) p->addr & 0x01)
135 return -EINVAL;
136 /* Make sure the probe isn't going on a difficult instruction */
137 if (probe_is_prohibited_opcode(p->addr))
138 return -EINVAL;
139 if (s390_get_insn_slot(p))
140 return -ENOMEM;
141 copy_instruction(p);
142 return 0;
143}
144NOKPROBE_SYMBOL(arch_prepare_kprobe);
145
146int arch_check_ftrace_location(struct kprobe *p)
147{
148 return 0;
149}
150
151struct swap_insn_args {
152 struct kprobe *p;
153 unsigned int arm_kprobe : 1;
154};
155
156static int swap_instruction(void *data)
157{
158 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
159 unsigned long status = kcb->kprobe_status;
160 struct swap_insn_args *args = data;
161 struct ftrace_insn new_insn, *insn;
162 struct kprobe *p = args->p;
163 size_t len;
164
165 new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
166 len = sizeof(new_insn.opc);
167 if (!p->ainsn.is_ftrace_insn)
168 goto skip_ftrace;
169 len = sizeof(new_insn);
170 insn = (struct ftrace_insn *) p->addr;
171 if (args->arm_kprobe) {
172 if (is_ftrace_nop(insn))
173 new_insn.disp = KPROBE_ON_FTRACE_NOP;
174 else
175 new_insn.disp = KPROBE_ON_FTRACE_CALL;
176 } else {
177 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
178 if (insn->disp == KPROBE_ON_FTRACE_NOP)
179 ftrace_generate_nop_insn(&new_insn);
180 }
181skip_ftrace:
182 kcb->kprobe_status = KPROBE_SWAP_INST;
183 s390_kernel_write(p->addr, &new_insn, len);
184 kcb->kprobe_status = status;
185 return 0;
186}
187NOKPROBE_SYMBOL(swap_instruction);
188
189void arch_arm_kprobe(struct kprobe *p)
190{
191 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
192
193 stop_machine(swap_instruction, &args, NULL);
194}
195NOKPROBE_SYMBOL(arch_arm_kprobe);
196
197void arch_disarm_kprobe(struct kprobe *p)
198{
199 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
200
201 stop_machine(swap_instruction, &args, NULL);
202}
203NOKPROBE_SYMBOL(arch_disarm_kprobe);
204
205void arch_remove_kprobe(struct kprobe *p)
206{
207 s390_free_insn_slot(p);
208}
209NOKPROBE_SYMBOL(arch_remove_kprobe);
210
211static void enable_singlestep(struct kprobe_ctlblk *kcb,
212 struct pt_regs *regs,
213 unsigned long ip)
214{
215 struct per_regs per_kprobe;
216
217 /* Set up the PER control registers %cr9-%cr11 */
218 per_kprobe.control = PER_EVENT_IFETCH;
219 per_kprobe.start = ip;
220 per_kprobe.end = ip;
221
222 /* Save control regs and psw mask */
223 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
224 kcb->kprobe_saved_imask = regs->psw.mask &
225 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
226
227 /* Set PER control regs, turns on single step for the given address */
228 __ctl_load(per_kprobe, 9, 11);
229 regs->psw.mask |= PSW_MASK_PER;
230 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
231 regs->psw.addr = ip;
232}
233NOKPROBE_SYMBOL(enable_singlestep);
234
235static void disable_singlestep(struct kprobe_ctlblk *kcb,
236 struct pt_regs *regs,
237 unsigned long ip)
238{
239 /* Restore control regs and psw mask, set new psw address */
240 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
241 regs->psw.mask &= ~PSW_MASK_PER;
242 regs->psw.mask |= kcb->kprobe_saved_imask;
243 regs->psw.addr = ip;
244}
245NOKPROBE_SYMBOL(disable_singlestep);
246
247/*
248 * Activate a kprobe by storing its pointer to current_kprobe. The
249 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
250 * two kprobes can be active, see KPROBE_REENTER.
251 */
252static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
253{
254 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
255 kcb->prev_kprobe.status = kcb->kprobe_status;
256 __this_cpu_write(current_kprobe, p);
257}
258NOKPROBE_SYMBOL(push_kprobe);
259
260/*
261 * Deactivate a kprobe by backing up to the previous state. If the
262 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
263 * for any other state prev_kprobe.kp will be NULL.
264 */
265static void pop_kprobe(struct kprobe_ctlblk *kcb)
266{
267 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
268 kcb->kprobe_status = kcb->prev_kprobe.status;
269}
270NOKPROBE_SYMBOL(pop_kprobe);
271
272void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
273{
274 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
275
276 /* Replace the return addr with trampoline addr */
277 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
278}
279NOKPROBE_SYMBOL(arch_prepare_kretprobe);
280
281static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
282{
283 switch (kcb->kprobe_status) {
284 case KPROBE_HIT_SSDONE:
285 case KPROBE_HIT_ACTIVE:
286 kprobes_inc_nmissed_count(p);
287 break;
288 case KPROBE_HIT_SS:
289 case KPROBE_REENTER:
290 default:
291 /*
292 * A kprobe on the code path to single step an instruction
293 * is a BUG. The code path resides in the .kprobes.text
294 * section and is executed with interrupts disabled.
295 */
296 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
297 dump_kprobe(p);
298 BUG();
299 }
300}
301NOKPROBE_SYMBOL(kprobe_reenter_check);
302
303static int kprobe_handler(struct pt_regs *regs)
304{
305 struct kprobe_ctlblk *kcb;
306 struct kprobe *p;
307
308 /*
309 * We want to disable preemption for the entire duration of kprobe
310 * processing. That includes the calls to the pre/post handlers
311 * and single stepping the kprobe instruction.
312 */
313 preempt_disable();
314 kcb = get_kprobe_ctlblk();
315 p = get_kprobe((void *)(regs->psw.addr - 2));
316
317 if (p) {
318 if (kprobe_running()) {
319 /*
320 * We have hit a kprobe while another is still
321 * active. This can happen in the pre and post
322 * handler. Single step the instruction of the
323 * new probe but do not call any handler function
324 * of this secondary kprobe.
325 * push_kprobe and pop_kprobe saves and restores
326 * the currently active kprobe.
327 */
328 kprobe_reenter_check(kcb, p);
329 push_kprobe(kcb, p);
330 kcb->kprobe_status = KPROBE_REENTER;
331 } else {
332 /*
333 * If we have no pre-handler or it returned 0, we
334 * continue with single stepping. If we have a
335 * pre-handler and it returned non-zero, it prepped
336 * for calling the break_handler below on re-entry
337 * for jprobe processing, so get out doing nothing
338 * more here.
339 */
340 push_kprobe(kcb, p);
341 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
342 if (p->pre_handler && p->pre_handler(p, regs))
343 return 1;
344 kcb->kprobe_status = KPROBE_HIT_SS;
345 }
346 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
347 return 1;
348 } else if (kprobe_running()) {
349 p = __this_cpu_read(current_kprobe);
350 if (p->break_handler && p->break_handler(p, regs)) {
351 /*
352 * Continuation after the jprobe completed and
353 * caused the jprobe_return trap. The jprobe
354 * break_handler "returns" to the original
355 * function that still has the kprobe breakpoint
356 * installed. We continue with single stepping.
357 */
358 kcb->kprobe_status = KPROBE_HIT_SS;
359 enable_singlestep(kcb, regs,
360 (unsigned long) p->ainsn.insn);
361 return 1;
362 } /* else:
363 * No kprobe at this address and the current kprobe
364 * has no break handler (no jprobe!). The kernel just
365 * exploded, let the standard trap handler pick up the
366 * pieces.
367 */
368 } /* else:
369 * No kprobe at this address and no active kprobe. The trap has
370 * not been caused by a kprobe breakpoint. The race of breakpoint
371 * vs. kprobe remove does not exist because on s390 as we use
372 * stop_machine to arm/disarm the breakpoints.
373 */
374 preempt_enable_no_resched();
375 return 0;
376}
377NOKPROBE_SYMBOL(kprobe_handler);
378
379/*
380 * Function return probe trampoline:
381 * - init_kprobes() establishes a probepoint here
382 * - When the probed function returns, this probe
383 * causes the handlers to fire
384 */
385static void __used kretprobe_trampoline_holder(void)
386{
387 asm volatile(".global kretprobe_trampoline\n"
388 "kretprobe_trampoline: bcr 0,0\n");
389}
390
391/*
392 * Called when the probe at kretprobe trampoline is hit
393 */
394static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
395{
396 struct kretprobe_instance *ri;
397 struct hlist_head *head, empty_rp;
398 struct hlist_node *tmp;
399 unsigned long flags, orig_ret_address;
400 unsigned long trampoline_address;
401 kprobe_opcode_t *correct_ret_addr;
402
403 INIT_HLIST_HEAD(&empty_rp);
404 kretprobe_hash_lock(current, &head, &flags);
405
406 /*
407 * It is possible to have multiple instances associated with a given
408 * task either because an multiple functions in the call path
409 * have a return probe installed on them, and/or more than one return
410 * return probe was registered for a target function.
411 *
412 * We can handle this because:
413 * - instances are always inserted at the head of the list
414 * - when multiple return probes are registered for the same
415 * function, the first instance's ret_addr will point to the
416 * real return address, and all the rest will point to
417 * kretprobe_trampoline
418 */
419 ri = NULL;
420 orig_ret_address = 0;
421 correct_ret_addr = NULL;
422 trampoline_address = (unsigned long) &kretprobe_trampoline;
423 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
424 if (ri->task != current)
425 /* another task is sharing our hash bucket */
426 continue;
427
428 orig_ret_address = (unsigned long) ri->ret_addr;
429
430 if (orig_ret_address != trampoline_address)
431 /*
432 * This is the real return address. Any other
433 * instances associated with this task are for
434 * other calls deeper on the call stack
435 */
436 break;
437 }
438
439 kretprobe_assert(ri, orig_ret_address, trampoline_address);
440
441 correct_ret_addr = ri->ret_addr;
442 hlist_for_each_entry_safe(ri, tmp, head, hlist) {
443 if (ri->task != current)
444 /* another task is sharing our hash bucket */
445 continue;
446
447 orig_ret_address = (unsigned long) ri->ret_addr;
448
449 if (ri->rp && ri->rp->handler) {
450 ri->ret_addr = correct_ret_addr;
451 ri->rp->handler(ri, regs);
452 }
453
454 recycle_rp_inst(ri, &empty_rp);
455
456 if (orig_ret_address != trampoline_address)
457 /*
458 * This is the real return address. Any other
459 * instances associated with this task are for
460 * other calls deeper on the call stack
461 */
462 break;
463 }
464
465 regs->psw.addr = orig_ret_address;
466
467 pop_kprobe(get_kprobe_ctlblk());
468 kretprobe_hash_unlock(current, &flags);
469 preempt_enable_no_resched();
470
471 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
472 hlist_del(&ri->hlist);
473 kfree(ri);
474 }
475 /*
476 * By returning a non-zero value, we are telling
477 * kprobe_handler() that we don't want the post_handler
478 * to run (and have re-enabled preemption)
479 */
480 return 1;
481}
482NOKPROBE_SYMBOL(trampoline_probe_handler);
483
484/*
485 * Called after single-stepping. p->addr is the address of the
486 * instruction whose first byte has been replaced by the "breakpoint"
487 * instruction. To avoid the SMP problems that can occur when we
488 * temporarily put back the original opcode to single-step, we
489 * single-stepped a copy of the instruction. The address of this
490 * copy is p->ainsn.insn.
491 */
492static void resume_execution(struct kprobe *p, struct pt_regs *regs)
493{
494 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
495 unsigned long ip = regs->psw.addr;
496 int fixup = probe_get_fixup_type(p->ainsn.insn);
497
498 /* Check if the kprobes location is an enabled ftrace caller */
499 if (p->ainsn.is_ftrace_insn) {
500 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
501 struct ftrace_insn call_insn;
502
503 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
504 /*
505 * A kprobe on an enabled ftrace call site actually single
506 * stepped an unconditional branch (ftrace nop equivalent).
507 * Now we need to fixup things and pretend that a brasl r0,...
508 * was executed instead.
509 */
510 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
511 ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
512 regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
513 }
514 }
515
516 if (fixup & FIXUP_PSW_NORMAL)
517 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
518
519 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
520 int ilen = insn_length(p->ainsn.insn[0] >> 8);
521 if (ip - (unsigned long) p->ainsn.insn == ilen)
522 ip = (unsigned long) p->addr + ilen;
523 }
524
525 if (fixup & FIXUP_RETURN_REGISTER) {
526 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
527 regs->gprs[reg] += (unsigned long) p->addr -
528 (unsigned long) p->ainsn.insn;
529 }
530
531 disable_singlestep(kcb, regs, ip);
532}
533NOKPROBE_SYMBOL(resume_execution);
534
535static int post_kprobe_handler(struct pt_regs *regs)
536{
537 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
538 struct kprobe *p = kprobe_running();
539
540 if (!p)
541 return 0;
542
543 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
544 kcb->kprobe_status = KPROBE_HIT_SSDONE;
545 p->post_handler(p, regs, 0);
546 }
547
548 resume_execution(p, regs);
549 pop_kprobe(kcb);
550 preempt_enable_no_resched();
551
552 /*
553 * if somebody else is singlestepping across a probe point, psw mask
554 * will have PER set, in which case, continue the remaining processing
555 * of do_single_step, as if this is not a probe hit.
556 */
557 if (regs->psw.mask & PSW_MASK_PER)
558 return 0;
559
560 return 1;
561}
562NOKPROBE_SYMBOL(post_kprobe_handler);
563
564static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
565{
566 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
567 struct kprobe *p = kprobe_running();
568 const struct exception_table_entry *entry;
569
570 switch(kcb->kprobe_status) {
571 case KPROBE_SWAP_INST:
572 /* We are here because the instruction replacement failed */
573 return 0;
574 case KPROBE_HIT_SS:
575 case KPROBE_REENTER:
576 /*
577 * We are here because the instruction being single
578 * stepped caused a page fault. We reset the current
579 * kprobe and the nip points back to the probe address
580 * and allow the page fault handler to continue as a
581 * normal page fault.
582 */
583 disable_singlestep(kcb, regs, (unsigned long) p->addr);
584 pop_kprobe(kcb);
585 preempt_enable_no_resched();
586 break;
587 case KPROBE_HIT_ACTIVE:
588 case KPROBE_HIT_SSDONE:
589 /*
590 * We increment the nmissed count for accounting,
591 * we can also use npre/npostfault count for accounting
592 * these specific fault cases.
593 */
594 kprobes_inc_nmissed_count(p);
595
596 /*
597 * We come here because instructions in the pre/post
598 * handler caused the page_fault, this could happen
599 * if handler tries to access user space by
600 * copy_from_user(), get_user() etc. Let the
601 * user-specified handler try to fix it first.
602 */
603 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
604 return 1;
605
606 /*
607 * In case the user-specified fault handler returned
608 * zero, try to fix up.
609 */
610 entry = search_exception_tables(regs->psw.addr);
611 if (entry) {
612 regs->psw.addr = extable_fixup(entry);
613 return 1;
614 }
615
616 /*
617 * fixup_exception() could not handle it,
618 * Let do_page_fault() fix it.
619 */
620 break;
621 default:
622 break;
623 }
624 return 0;
625}
626NOKPROBE_SYMBOL(kprobe_trap_handler);
627
628int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
629{
630 int ret;
631
632 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
633 local_irq_disable();
634 ret = kprobe_trap_handler(regs, trapnr);
635 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
636 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
637 return ret;
638}
639NOKPROBE_SYMBOL(kprobe_fault_handler);
640
641/*
642 * Wrapper routine to for handling exceptions.
643 */
644int kprobe_exceptions_notify(struct notifier_block *self,
645 unsigned long val, void *data)
646{
647 struct die_args *args = (struct die_args *) data;
648 struct pt_regs *regs = args->regs;
649 int ret = NOTIFY_DONE;
650
651 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
652 local_irq_disable();
653
654 switch (val) {
655 case DIE_BPT:
656 if (kprobe_handler(regs))
657 ret = NOTIFY_STOP;
658 break;
659 case DIE_SSTEP:
660 if (post_kprobe_handler(regs))
661 ret = NOTIFY_STOP;
662 break;
663 case DIE_TRAP:
664 if (!preemptible() && kprobe_running() &&
665 kprobe_trap_handler(regs, args->trapnr))
666 ret = NOTIFY_STOP;
667 break;
668 default:
669 break;
670 }
671
672 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
673 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
674
675 return ret;
676}
677NOKPROBE_SYMBOL(kprobe_exceptions_notify);
678
679int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
680{
681 struct jprobe *jp = container_of(p, struct jprobe, kp);
682 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
683 unsigned long stack;
684
685 memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
686
687 /* setup return addr to the jprobe handler routine */
688 regs->psw.addr = (unsigned long) jp->entry;
689 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
690
691 /* r15 is the stack pointer */
692 stack = (unsigned long) regs->gprs[15];
693
694 memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
695
696 /*
697 * jprobes use jprobe_return() which skips the normal return
698 * path of the function, and this messes up the accounting of the
699 * function graph tracer to get messed up.
700 *
701 * Pause function graph tracing while performing the jprobe function.
702 */
703 pause_graph_tracing();
704 return 1;
705}
706NOKPROBE_SYMBOL(setjmp_pre_handler);
707
708void jprobe_return(void)
709{
710 asm volatile(".word 0x0002");
711}
712NOKPROBE_SYMBOL(jprobe_return);
713
714int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
715{
716 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
717 unsigned long stack;
718
719 /* It's OK to start function graph tracing again */
720 unpause_graph_tracing();
721
722 stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
723
724 /* Put the regs back */
725 memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
726 /* put the stack back */
727 memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
728 preempt_enable_no_resched();
729 return 1;
730}
731NOKPROBE_SYMBOL(longjmp_break_handler);
732
733static struct kprobe trampoline = {
734 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
735 .pre_handler = trampoline_probe_handler
736};
737
738int __init arch_init_kprobes(void)
739{
740 return register_kprobe(&trampoline);
741}
742
743int arch_trampoline_kprobe(struct kprobe *p)
744{
745 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
746}
747NOKPROBE_SYMBOL(arch_trampoline_kprobe);