1 // SPDX-License-Identifier: GPL-2.0+
3 * Kernel Probes (KProbes)
5 * Copyright IBM Corp. 2002, 2006
7 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
10 #include <linux/moduleloader.h>
11 #include <linux/kprobes.h>
12 #include <linux/ptrace.h>
13 #include <linux/preempt.h>
14 #include <linux/stop_machine.h>
15 #include <linux/kdebug.h>
16 #include <linux/uaccess.h>
17 #include <linux/extable.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
20 #include <linux/hardirq.h>
21 #include <linux/ftrace.h>
22 #include <asm/set_memory.h>
23 #include <asm/sections.h>
27 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
28 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
30 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
32 DEFINE_INSN_CACHE_OPS(s390_insn);
34 static int insn_page_in_use;
36 void *alloc_insn_page(void)
40 page = module_alloc(PAGE_SIZE);
43 __set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
47 void free_insn_page(void *page)
52 static void *alloc_s390_insn_page(void)
54 if (xchg(&insn_page_in_use, 1) == 1)
56 return &kprobes_insn_page;
59 static void free_s390_insn_page(void *page)
61 xchg(&insn_page_in_use, 0);
64 struct kprobe_insn_cache kprobe_s390_insn_slots = {
65 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
66 .alloc = alloc_s390_insn_page,
67 .free = free_s390_insn_page,
68 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
69 .insn_size = MAX_INSN_SIZE,
72 static void copy_instruction(struct kprobe *p)
74 kprobe_opcode_t insn[MAX_INSN_SIZE];
79 len = insn_length(*p->addr >> 8);
80 memcpy(&insn, p->addr, len);
82 if (probe_is_insn_relative_long(&insn[0])) {
84 * For pc-relative instructions in RIL-b or RIL-c format patch
85 * the RI2 displacement field. We have already made sure that
86 * the insn slot for the patched instruction is within the same
87 * 2GB area as the original instruction (either kernel image or
88 * module area). Therefore the new displacement will always fit.
90 disp = *(s32 *)&insn[1];
91 addr = (u64)(unsigned long)p->addr;
92 new_addr = (u64)(unsigned long)p->ainsn.insn;
93 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
94 *(s32 *)&insn[1] = new_disp;
96 s390_kernel_write(p->ainsn.insn, &insn, len);
98 NOKPROBE_SYMBOL(copy_instruction);
100 static inline int is_kernel_addr(void *addr)
102 return addr < (void *)_end;
105 static int s390_get_insn_slot(struct kprobe *p)
108 * Get an insn slot that is within the same 2GB area like the original
109 * instruction. That way instructions with a 32bit signed displacement
110 * field can be patched and executed within the insn slot.
112 p->ainsn.insn = NULL;
113 if (is_kernel_addr(p->addr))
114 p->ainsn.insn = get_s390_insn_slot();
115 else if (is_module_addr(p->addr))
116 p->ainsn.insn = get_insn_slot();
117 return p->ainsn.insn ? 0 : -ENOMEM;
119 NOKPROBE_SYMBOL(s390_get_insn_slot);
121 static void s390_free_insn_slot(struct kprobe *p)
125 if (is_kernel_addr(p->addr))
126 free_s390_insn_slot(p->ainsn.insn, 0);
128 free_insn_slot(p->ainsn.insn, 0);
129 p->ainsn.insn = NULL;
131 NOKPROBE_SYMBOL(s390_free_insn_slot);
133 int arch_prepare_kprobe(struct kprobe *p)
135 if ((unsigned long) p->addr & 0x01)
137 /* Make sure the probe isn't going on a difficult instruction */
138 if (probe_is_prohibited_opcode(p->addr))
140 if (s390_get_insn_slot(p))
145 NOKPROBE_SYMBOL(arch_prepare_kprobe);
147 struct swap_insn_args {
149 unsigned int arm_kprobe : 1;
152 static int swap_instruction(void *data)
154 struct swap_insn_args *args = data;
155 struct kprobe *p = args->p;
158 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
159 s390_kernel_write(p->addr, &opc, sizeof(opc));
162 NOKPROBE_SYMBOL(swap_instruction);
164 void arch_arm_kprobe(struct kprobe *p)
166 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
168 stop_machine_cpuslocked(swap_instruction, &args, NULL);
170 NOKPROBE_SYMBOL(arch_arm_kprobe);
172 void arch_disarm_kprobe(struct kprobe *p)
174 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
176 stop_machine_cpuslocked(swap_instruction, &args, NULL);
178 NOKPROBE_SYMBOL(arch_disarm_kprobe);
180 void arch_remove_kprobe(struct kprobe *p)
182 s390_free_insn_slot(p);
184 NOKPROBE_SYMBOL(arch_remove_kprobe);
186 static void enable_singlestep(struct kprobe_ctlblk *kcb,
187 struct pt_regs *regs,
190 struct per_regs per_kprobe;
192 /* Set up the PER control registers %cr9-%cr11 */
193 per_kprobe.control = PER_EVENT_IFETCH;
194 per_kprobe.start = ip;
197 /* Save control regs and psw mask */
198 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
199 kcb->kprobe_saved_imask = regs->psw.mask &
200 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
202 /* Set PER control regs, turns on single step for the given address */
203 __ctl_load(per_kprobe, 9, 11);
204 regs->psw.mask |= PSW_MASK_PER;
205 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
208 NOKPROBE_SYMBOL(enable_singlestep);
210 static void disable_singlestep(struct kprobe_ctlblk *kcb,
211 struct pt_regs *regs,
214 /* Restore control regs and psw mask, set new psw address */
215 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
216 regs->psw.mask &= ~PSW_MASK_PER;
217 regs->psw.mask |= kcb->kprobe_saved_imask;
220 NOKPROBE_SYMBOL(disable_singlestep);
223 * Activate a kprobe by storing its pointer to current_kprobe. The
224 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
225 * two kprobes can be active, see KPROBE_REENTER.
227 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
229 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
230 kcb->prev_kprobe.status = kcb->kprobe_status;
231 __this_cpu_write(current_kprobe, p);
233 NOKPROBE_SYMBOL(push_kprobe);
236 * Deactivate a kprobe by backing up to the previous state. If the
237 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
238 * for any other state prev_kprobe.kp will be NULL.
240 static void pop_kprobe(struct kprobe_ctlblk *kcb)
242 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
243 kcb->kprobe_status = kcb->prev_kprobe.status;
245 NOKPROBE_SYMBOL(pop_kprobe);
247 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
249 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
252 /* Replace the return addr with trampoline addr */
253 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
255 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
257 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
259 switch (kcb->kprobe_status) {
260 case KPROBE_HIT_SSDONE:
261 case KPROBE_HIT_ACTIVE:
262 kprobes_inc_nmissed_count(p);
268 * A kprobe on the code path to single step an instruction
269 * is a BUG. The code path resides in the .kprobes.text
270 * section and is executed with interrupts disabled.
272 pr_err("Invalid kprobe detected.\n");
277 NOKPROBE_SYMBOL(kprobe_reenter_check);
279 static int kprobe_handler(struct pt_regs *regs)
281 struct kprobe_ctlblk *kcb;
285 * We want to disable preemption for the entire duration of kprobe
286 * processing. That includes the calls to the pre/post handlers
287 * and single stepping the kprobe instruction.
290 kcb = get_kprobe_ctlblk();
291 p = get_kprobe((void *)(regs->psw.addr - 2));
294 if (kprobe_running()) {
296 * We have hit a kprobe while another is still
297 * active. This can happen in the pre and post
298 * handler. Single step the instruction of the
299 * new probe but do not call any handler function
300 * of this secondary kprobe.
301 * push_kprobe and pop_kprobe saves and restores
302 * the currently active kprobe.
304 kprobe_reenter_check(kcb, p);
306 kcb->kprobe_status = KPROBE_REENTER;
309 * If we have no pre-handler or it returned 0, we
310 * continue with single stepping. If we have a
311 * pre-handler and it returned non-zero, it prepped
312 * for changing execution path, so get out doing
316 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
317 if (p->pre_handler && p->pre_handler(p, regs)) {
319 preempt_enable_no_resched();
322 kcb->kprobe_status = KPROBE_HIT_SS;
324 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
327 * No kprobe at this address and no active kprobe. The trap has
328 * not been caused by a kprobe breakpoint. The race of breakpoint
329 * vs. kprobe remove does not exist because on s390 as we use
330 * stop_machine to arm/disarm the breakpoints.
332 preempt_enable_no_resched();
335 NOKPROBE_SYMBOL(kprobe_handler);
338 * Function return probe trampoline:
339 * - init_kprobes() establishes a probepoint here
340 * - When the probed function returns, this probe
341 * causes the handlers to fire
343 static void __used kretprobe_trampoline_holder(void)
345 asm volatile(".global kretprobe_trampoline\n"
346 "kretprobe_trampoline: bcr 0,0\n");
350 * Called when the probe at kretprobe trampoline is hit
352 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
354 regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
356 * By returning a non-zero value, we are telling
357 * kprobe_handler() that we don't want the post_handler
358 * to run (and have re-enabled preemption)
362 NOKPROBE_SYMBOL(trampoline_probe_handler);
365 * Called after single-stepping. p->addr is the address of the
366 * instruction whose first byte has been replaced by the "breakpoint"
367 * instruction. To avoid the SMP problems that can occur when we
368 * temporarily put back the original opcode to single-step, we
369 * single-stepped a copy of the instruction. The address of this
370 * copy is p->ainsn.insn.
372 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
374 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
375 unsigned long ip = regs->psw.addr;
376 int fixup = probe_get_fixup_type(p->ainsn.insn);
378 if (fixup & FIXUP_PSW_NORMAL)
379 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
381 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
382 int ilen = insn_length(p->ainsn.insn[0] >> 8);
383 if (ip - (unsigned long) p->ainsn.insn == ilen)
384 ip = (unsigned long) p->addr + ilen;
387 if (fixup & FIXUP_RETURN_REGISTER) {
388 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
389 regs->gprs[reg] += (unsigned long) p->addr -
390 (unsigned long) p->ainsn.insn;
393 disable_singlestep(kcb, regs, ip);
395 NOKPROBE_SYMBOL(resume_execution);
397 static int post_kprobe_handler(struct pt_regs *regs)
399 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
400 struct kprobe *p = kprobe_running();
405 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
406 kcb->kprobe_status = KPROBE_HIT_SSDONE;
407 p->post_handler(p, regs, 0);
410 resume_execution(p, regs);
412 preempt_enable_no_resched();
415 * if somebody else is singlestepping across a probe point, psw mask
416 * will have PER set, in which case, continue the remaining processing
417 * of do_single_step, as if this is not a probe hit.
419 if (regs->psw.mask & PSW_MASK_PER)
424 NOKPROBE_SYMBOL(post_kprobe_handler);
426 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
428 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
429 struct kprobe *p = kprobe_running();
430 const struct exception_table_entry *entry;
432 switch(kcb->kprobe_status) {
436 * We are here because the instruction being single
437 * stepped caused a page fault. We reset the current
438 * kprobe and the nip points back to the probe address
439 * and allow the page fault handler to continue as a
442 disable_singlestep(kcb, regs, (unsigned long) p->addr);
444 preempt_enable_no_resched();
446 case KPROBE_HIT_ACTIVE:
447 case KPROBE_HIT_SSDONE:
449 * We increment the nmissed count for accounting,
450 * we can also use npre/npostfault count for accounting
451 * these specific fault cases.
453 kprobes_inc_nmissed_count(p);
456 * We come here because instructions in the pre/post
457 * handler caused the page_fault, this could happen
458 * if handler tries to access user space by
459 * copy_from_user(), get_user() etc. Let the
460 * user-specified handler try to fix it first.
462 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
466 * In case the user-specified fault handler returned
467 * zero, try to fix up.
469 entry = s390_search_extables(regs->psw.addr);
470 if (entry && ex_handle(entry, regs))
474 * fixup_exception() could not handle it,
475 * Let do_page_fault() fix it.
483 NOKPROBE_SYMBOL(kprobe_trap_handler);
485 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
489 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
491 ret = kprobe_trap_handler(regs, trapnr);
492 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
493 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
496 NOKPROBE_SYMBOL(kprobe_fault_handler);
499 * Wrapper routine to for handling exceptions.
501 int kprobe_exceptions_notify(struct notifier_block *self,
502 unsigned long val, void *data)
504 struct die_args *args = (struct die_args *) data;
505 struct pt_regs *regs = args->regs;
506 int ret = NOTIFY_DONE;
508 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
513 if (kprobe_handler(regs))
517 if (post_kprobe_handler(regs))
521 if (!preemptible() && kprobe_running() &&
522 kprobe_trap_handler(regs, args->trapnr))
529 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
530 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
534 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
536 static struct kprobe trampoline = {
537 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
538 .pre_handler = trampoline_probe_handler
541 int __init arch_init_kprobes(void)
543 return register_kprobe(&trampoline);
546 int arch_trampoline_kprobe(struct kprobe *p)
548 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
550 NOKPROBE_SYMBOL(arch_trampoline_kprobe);