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 static void *alloc_s390_insn_page(void)
49 if (xchg(&insn_page_in_use, 1) == 1)
51 return &kprobes_insn_page;
54 static void free_s390_insn_page(void *page)
56 xchg(&insn_page_in_use, 0);
59 struct kprobe_insn_cache kprobe_s390_insn_slots = {
60 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
61 .alloc = alloc_s390_insn_page,
62 .free = free_s390_insn_page,
63 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
64 .insn_size = MAX_INSN_SIZE,
67 static void copy_instruction(struct kprobe *p)
69 kprobe_opcode_t insn[MAX_INSN_SIZE];
74 len = insn_length(*p->addr >> 8);
75 memcpy(&insn, p->addr, len);
77 if (probe_is_insn_relative_long(&insn[0])) {
79 * For pc-relative instructions in RIL-b or RIL-c format patch
80 * the RI2 displacement field. We have already made sure that
81 * the insn slot for the patched instruction is within the same
82 * 2GB area as the original instruction (either kernel image or
83 * module area). Therefore the new displacement will always fit.
85 disp = *(s32 *)&insn[1];
86 addr = (u64)(unsigned long)p->addr;
87 new_addr = (u64)(unsigned long)p->ainsn.insn;
88 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
89 *(s32 *)&insn[1] = new_disp;
91 s390_kernel_write(p->ainsn.insn, &insn, len);
93 NOKPROBE_SYMBOL(copy_instruction);
95 static int s390_get_insn_slot(struct kprobe *p)
98 * Get an insn slot that is within the same 2GB area like the original
99 * instruction. That way instructions with a 32bit signed displacement
100 * field can be patched and executed within the insn slot.
102 p->ainsn.insn = NULL;
103 if (is_kernel((unsigned long)p->addr))
104 p->ainsn.insn = get_s390_insn_slot();
105 else if (is_module_addr(p->addr))
106 p->ainsn.insn = get_insn_slot();
107 return p->ainsn.insn ? 0 : -ENOMEM;
109 NOKPROBE_SYMBOL(s390_get_insn_slot);
111 static void s390_free_insn_slot(struct kprobe *p)
115 if (is_kernel((unsigned long)p->addr))
116 free_s390_insn_slot(p->ainsn.insn, 0);
118 free_insn_slot(p->ainsn.insn, 0);
119 p->ainsn.insn = NULL;
121 NOKPROBE_SYMBOL(s390_free_insn_slot);
123 int arch_prepare_kprobe(struct kprobe *p)
125 if ((unsigned long) p->addr & 0x01)
127 /* Make sure the probe isn't going on a difficult instruction */
128 if (probe_is_prohibited_opcode(p->addr))
130 if (s390_get_insn_slot(p))
135 NOKPROBE_SYMBOL(arch_prepare_kprobe);
137 struct swap_insn_args {
139 unsigned int arm_kprobe : 1;
142 static int swap_instruction(void *data)
144 struct swap_insn_args *args = data;
145 struct kprobe *p = args->p;
148 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
149 s390_kernel_write(p->addr, &opc, sizeof(opc));
152 NOKPROBE_SYMBOL(swap_instruction);
154 void arch_arm_kprobe(struct kprobe *p)
156 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
158 stop_machine_cpuslocked(swap_instruction, &args, NULL);
160 NOKPROBE_SYMBOL(arch_arm_kprobe);
162 void arch_disarm_kprobe(struct kprobe *p)
164 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
166 stop_machine_cpuslocked(swap_instruction, &args, NULL);
168 NOKPROBE_SYMBOL(arch_disarm_kprobe);
170 void arch_remove_kprobe(struct kprobe *p)
172 s390_free_insn_slot(p);
174 NOKPROBE_SYMBOL(arch_remove_kprobe);
176 static void enable_singlestep(struct kprobe_ctlblk *kcb,
177 struct pt_regs *regs,
180 struct per_regs per_kprobe;
182 /* Set up the PER control registers %cr9-%cr11 */
183 per_kprobe.control = PER_EVENT_IFETCH;
184 per_kprobe.start = ip;
187 /* Save control regs and psw mask */
188 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
189 kcb->kprobe_saved_imask = regs->psw.mask &
190 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
192 /* Set PER control regs, turns on single step for the given address */
193 __ctl_load(per_kprobe, 9, 11);
194 regs->psw.mask |= PSW_MASK_PER;
195 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
198 NOKPROBE_SYMBOL(enable_singlestep);
200 static void disable_singlestep(struct kprobe_ctlblk *kcb,
201 struct pt_regs *regs,
204 /* Restore control regs and psw mask, set new psw address */
205 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
206 regs->psw.mask &= ~PSW_MASK_PER;
207 regs->psw.mask |= kcb->kprobe_saved_imask;
210 NOKPROBE_SYMBOL(disable_singlestep);
213 * Activate a kprobe by storing its pointer to current_kprobe. The
214 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
215 * two kprobes can be active, see KPROBE_REENTER.
217 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
219 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
220 kcb->prev_kprobe.status = kcb->kprobe_status;
221 __this_cpu_write(current_kprobe, p);
223 NOKPROBE_SYMBOL(push_kprobe);
226 * Deactivate a kprobe by backing up to the previous state. If the
227 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
228 * for any other state prev_kprobe.kp will be NULL.
230 static void pop_kprobe(struct kprobe_ctlblk *kcb)
232 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
233 kcb->kprobe_status = kcb->prev_kprobe.status;
235 NOKPROBE_SYMBOL(pop_kprobe);
237 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
239 ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
242 /* Replace the return addr with trampoline addr */
243 regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
245 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
247 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
249 switch (kcb->kprobe_status) {
250 case KPROBE_HIT_SSDONE:
251 case KPROBE_HIT_ACTIVE:
252 kprobes_inc_nmissed_count(p);
258 * A kprobe on the code path to single step an instruction
259 * is a BUG. The code path resides in the .kprobes.text
260 * section and is executed with interrupts disabled.
262 pr_err("Invalid kprobe detected.\n");
267 NOKPROBE_SYMBOL(kprobe_reenter_check);
269 static int kprobe_handler(struct pt_regs *regs)
271 struct kprobe_ctlblk *kcb;
275 * We want to disable preemption for the entire duration of kprobe
276 * processing. That includes the calls to the pre/post handlers
277 * and single stepping the kprobe instruction.
280 kcb = get_kprobe_ctlblk();
281 p = get_kprobe((void *)(regs->psw.addr - 2));
284 if (kprobe_running()) {
286 * We have hit a kprobe while another is still
287 * active. This can happen in the pre and post
288 * handler. Single step the instruction of the
289 * new probe but do not call any handler function
290 * of this secondary kprobe.
291 * push_kprobe and pop_kprobe saves and restores
292 * the currently active kprobe.
294 kprobe_reenter_check(kcb, p);
296 kcb->kprobe_status = KPROBE_REENTER;
299 * If we have no pre-handler or it returned 0, we
300 * continue with single stepping. If we have a
301 * pre-handler and it returned non-zero, it prepped
302 * for changing execution path, so get out doing
306 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
307 if (p->pre_handler && p->pre_handler(p, regs)) {
309 preempt_enable_no_resched();
312 kcb->kprobe_status = KPROBE_HIT_SS;
314 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
317 * No kprobe at this address and no active kprobe. The trap has
318 * not been caused by a kprobe breakpoint. The race of breakpoint
319 * vs. kprobe remove does not exist because on s390 as we use
320 * stop_machine to arm/disarm the breakpoints.
322 preempt_enable_no_resched();
325 NOKPROBE_SYMBOL(kprobe_handler);
328 * Function return probe trampoline:
329 * - init_kprobes() establishes a probepoint here
330 * - When the probed function returns, this probe
331 * causes the handlers to fire
333 static void __used kretprobe_trampoline_holder(void)
335 asm volatile(".global kretprobe_trampoline\n"
336 "kretprobe_trampoline: bcr 0,0\n");
340 * Called when the probe at kretprobe trampoline is hit
342 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
344 regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
346 * By returning a non-zero value, we are telling
347 * kprobe_handler() that we don't want the post_handler
348 * to run (and have re-enabled preemption)
352 NOKPROBE_SYMBOL(trampoline_probe_handler);
355 * Called after single-stepping. p->addr is the address of the
356 * instruction whose first byte has been replaced by the "breakpoint"
357 * instruction. To avoid the SMP problems that can occur when we
358 * temporarily put back the original opcode to single-step, we
359 * single-stepped a copy of the instruction. The address of this
360 * copy is p->ainsn.insn.
362 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
364 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
365 unsigned long ip = regs->psw.addr;
366 int fixup = probe_get_fixup_type(p->ainsn.insn);
368 if (fixup & FIXUP_PSW_NORMAL)
369 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
371 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
372 int ilen = insn_length(p->ainsn.insn[0] >> 8);
373 if (ip - (unsigned long) p->ainsn.insn == ilen)
374 ip = (unsigned long) p->addr + ilen;
377 if (fixup & FIXUP_RETURN_REGISTER) {
378 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
379 regs->gprs[reg] += (unsigned long) p->addr -
380 (unsigned long) p->ainsn.insn;
383 disable_singlestep(kcb, regs, ip);
385 NOKPROBE_SYMBOL(resume_execution);
387 static int post_kprobe_handler(struct pt_regs *regs)
389 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
390 struct kprobe *p = kprobe_running();
395 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
396 kcb->kprobe_status = KPROBE_HIT_SSDONE;
397 p->post_handler(p, regs, 0);
400 resume_execution(p, regs);
402 preempt_enable_no_resched();
405 * if somebody else is singlestepping across a probe point, psw mask
406 * will have PER set, in which case, continue the remaining processing
407 * of do_single_step, as if this is not a probe hit.
409 if (regs->psw.mask & PSW_MASK_PER)
414 NOKPROBE_SYMBOL(post_kprobe_handler);
416 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
418 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
419 struct kprobe *p = kprobe_running();
420 const struct exception_table_entry *entry;
422 switch(kcb->kprobe_status) {
426 * We are here because the instruction being single
427 * stepped caused a page fault. We reset the current
428 * kprobe and the nip points back to the probe address
429 * and allow the page fault handler to continue as a
432 disable_singlestep(kcb, regs, (unsigned long) p->addr);
434 preempt_enable_no_resched();
436 case KPROBE_HIT_ACTIVE:
437 case KPROBE_HIT_SSDONE:
439 * In case the user-specified fault handler returned
440 * zero, try to fix up.
442 entry = s390_search_extables(regs->psw.addr);
443 if (entry && ex_handle(entry, regs))
447 * fixup_exception() could not handle it,
448 * Let do_page_fault() fix it.
456 NOKPROBE_SYMBOL(kprobe_trap_handler);
458 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
462 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
464 ret = kprobe_trap_handler(regs, trapnr);
465 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
466 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
469 NOKPROBE_SYMBOL(kprobe_fault_handler);
472 * Wrapper routine to for handling exceptions.
474 int kprobe_exceptions_notify(struct notifier_block *self,
475 unsigned long val, void *data)
477 struct die_args *args = (struct die_args *) data;
478 struct pt_regs *regs = args->regs;
479 int ret = NOTIFY_DONE;
481 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
486 if (kprobe_handler(regs))
490 if (post_kprobe_handler(regs))
494 if (!preemptible() && kprobe_running() &&
495 kprobe_trap_handler(regs, args->trapnr))
502 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
503 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
507 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
509 static struct kprobe trampoline = {
510 .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
511 .pre_handler = trampoline_probe_handler
514 int __init arch_init_kprobes(void)
516 return register_kprobe(&trampoline);
519 int arch_trampoline_kprobe(struct kprobe *p)
521 return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
523 NOKPROBE_SYMBOL(arch_trampoline_kprobe);