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 #define pr_fmt(fmt) "kprobes: " fmt
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>
29 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
30 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
32 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
34 DEFINE_INSN_CACHE_OPS(s390_insn);
36 static int insn_page_in_use;
38 void *alloc_insn_page(void)
42 page = module_alloc(PAGE_SIZE);
45 __set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
49 static void *alloc_s390_insn_page(void)
51 if (xchg(&insn_page_in_use, 1) == 1)
53 return &kprobes_insn_page;
56 static void free_s390_insn_page(void *page)
58 xchg(&insn_page_in_use, 0);
61 struct kprobe_insn_cache kprobe_s390_insn_slots = {
62 .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
63 .alloc = alloc_s390_insn_page,
64 .free = free_s390_insn_page,
65 .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
66 .insn_size = MAX_INSN_SIZE,
69 static void copy_instruction(struct kprobe *p)
71 kprobe_opcode_t insn[MAX_INSN_SIZE];
76 len = insn_length(*p->addr >> 8);
77 memcpy(&insn, p->addr, len);
79 if (probe_is_insn_relative_long(&insn[0])) {
81 * For pc-relative instructions in RIL-b or RIL-c format patch
82 * the RI2 displacement field. We have already made sure that
83 * the insn slot for the patched instruction is within the same
84 * 2GB area as the original instruction (either kernel image or
85 * module area). Therefore the new displacement will always fit.
87 disp = *(s32 *)&insn[1];
88 addr = (u64)(unsigned long)p->addr;
89 new_addr = (u64)(unsigned long)p->ainsn.insn;
90 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
91 *(s32 *)&insn[1] = new_disp;
93 s390_kernel_write(p->ainsn.insn, &insn, len);
95 NOKPROBE_SYMBOL(copy_instruction);
97 static int s390_get_insn_slot(struct kprobe *p)
100 * Get an insn slot that is within the same 2GB area like the original
101 * instruction. That way instructions with a 32bit signed displacement
102 * field can be patched and executed within the insn slot.
104 p->ainsn.insn = NULL;
105 if (is_kernel((unsigned long)p->addr))
106 p->ainsn.insn = get_s390_insn_slot();
107 else if (is_module_addr(p->addr))
108 p->ainsn.insn = get_insn_slot();
109 return p->ainsn.insn ? 0 : -ENOMEM;
111 NOKPROBE_SYMBOL(s390_get_insn_slot);
113 static void s390_free_insn_slot(struct kprobe *p)
117 if (is_kernel((unsigned long)p->addr))
118 free_s390_insn_slot(p->ainsn.insn, 0);
120 free_insn_slot(p->ainsn.insn, 0);
121 p->ainsn.insn = NULL;
123 NOKPROBE_SYMBOL(s390_free_insn_slot);
125 /* Check if paddr is at an instruction boundary */
126 static bool can_probe(unsigned long paddr)
128 unsigned long addr, offset = 0;
129 kprobe_opcode_t insn;
135 if (!kallsyms_lookup_size_offset(paddr, NULL, &offset))
138 /* Decode instructions */
139 addr = paddr - offset;
140 while (addr < paddr) {
141 if (copy_from_kernel_nofault(&insn, (void *)addr, sizeof(insn)))
144 if (insn >> 8 == 0) {
145 if (insn != BREAKPOINT_INSTRUCTION) {
147 * Note that QEMU inserts opcode 0x0000 to implement
148 * software breakpoints for guests. Since the size of
149 * the original instruction is unknown, stop following
150 * instructions and prevent setting a kprobe.
155 * Check if the instruction has been modified by another
156 * kprobe, in which case the original instruction is
159 kp = get_kprobe((void *)addr);
166 addr += insn_length(insn >> 8);
168 return addr == paddr;
171 int arch_prepare_kprobe(struct kprobe *p)
173 if (!can_probe((unsigned long)p->addr))
175 /* Make sure the probe isn't going on a difficult instruction */
176 if (probe_is_prohibited_opcode(p->addr))
178 if (s390_get_insn_slot(p))
183 NOKPROBE_SYMBOL(arch_prepare_kprobe);
185 struct swap_insn_args {
187 unsigned int arm_kprobe : 1;
190 static int swap_instruction(void *data)
192 struct swap_insn_args *args = data;
193 struct kprobe *p = args->p;
196 opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
197 s390_kernel_write(p->addr, &opc, sizeof(opc));
200 NOKPROBE_SYMBOL(swap_instruction);
202 void arch_arm_kprobe(struct kprobe *p)
204 struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
206 stop_machine_cpuslocked(swap_instruction, &args, NULL);
208 NOKPROBE_SYMBOL(arch_arm_kprobe);
210 void arch_disarm_kprobe(struct kprobe *p)
212 struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
214 stop_machine_cpuslocked(swap_instruction, &args, NULL);
216 NOKPROBE_SYMBOL(arch_disarm_kprobe);
218 void arch_remove_kprobe(struct kprobe *p)
220 s390_free_insn_slot(p);
222 NOKPROBE_SYMBOL(arch_remove_kprobe);
224 static void enable_singlestep(struct kprobe_ctlblk *kcb,
225 struct pt_regs *regs,
228 struct per_regs per_kprobe;
230 /* Set up the PER control registers %cr9-%cr11 */
231 per_kprobe.control = PER_EVENT_IFETCH;
232 per_kprobe.start = ip;
235 /* Save control regs and psw mask */
236 __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
237 kcb->kprobe_saved_imask = regs->psw.mask &
238 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
240 /* Set PER control regs, turns on single step for the given address */
241 __ctl_load(per_kprobe, 9, 11);
242 regs->psw.mask |= PSW_MASK_PER;
243 regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
246 NOKPROBE_SYMBOL(enable_singlestep);
248 static void disable_singlestep(struct kprobe_ctlblk *kcb,
249 struct pt_regs *regs,
252 /* Restore control regs and psw mask, set new psw address */
253 __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
254 regs->psw.mask &= ~PSW_MASK_PER;
255 regs->psw.mask |= kcb->kprobe_saved_imask;
258 NOKPROBE_SYMBOL(disable_singlestep);
261 * Activate a kprobe by storing its pointer to current_kprobe. The
262 * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
263 * two kprobes can be active, see KPROBE_REENTER.
265 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
267 kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
268 kcb->prev_kprobe.status = kcb->kprobe_status;
269 __this_cpu_write(current_kprobe, p);
271 NOKPROBE_SYMBOL(push_kprobe);
274 * Deactivate a kprobe by backing up to the previous state. If the
275 * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
276 * for any other state prev_kprobe.kp will be NULL.
278 static void pop_kprobe(struct kprobe_ctlblk *kcb)
280 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
281 kcb->kprobe_status = kcb->prev_kprobe.status;
282 kcb->prev_kprobe.kp = NULL;
284 NOKPROBE_SYMBOL(pop_kprobe);
286 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
288 ri->ret_addr = (kprobe_opcode_t *)regs->gprs[14];
289 ri->fp = (void *)regs->gprs[15];
291 /* Replace the return addr with trampoline addr */
292 regs->gprs[14] = (unsigned long)&__kretprobe_trampoline;
294 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
296 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
298 switch (kcb->kprobe_status) {
299 case KPROBE_HIT_SSDONE:
300 case KPROBE_HIT_ACTIVE:
301 kprobes_inc_nmissed_count(p);
307 * A kprobe on the code path to single step an instruction
308 * is a BUG. The code path resides in the .kprobes.text
309 * section and is executed with interrupts disabled.
311 pr_err("Failed to recover from reentered kprobes.\n");
316 NOKPROBE_SYMBOL(kprobe_reenter_check);
318 static int kprobe_handler(struct pt_regs *regs)
320 struct kprobe_ctlblk *kcb;
324 * We want to disable preemption for the entire duration of kprobe
325 * processing. That includes the calls to the pre/post handlers
326 * and single stepping the kprobe instruction.
329 kcb = get_kprobe_ctlblk();
330 p = get_kprobe((void *)(regs->psw.addr - 2));
333 if (kprobe_running()) {
335 * We have hit a kprobe while another is still
336 * active. This can happen in the pre and post
337 * handler. Single step the instruction of the
338 * new probe but do not call any handler function
339 * of this secondary kprobe.
340 * push_kprobe and pop_kprobe saves and restores
341 * the currently active kprobe.
343 kprobe_reenter_check(kcb, p);
345 kcb->kprobe_status = KPROBE_REENTER;
348 * If we have no pre-handler or it returned 0, we
349 * continue with single stepping. If we have a
350 * pre-handler and it returned non-zero, it prepped
351 * for changing execution path, so get out doing
355 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
356 if (p->pre_handler && p->pre_handler(p, regs)) {
358 preempt_enable_no_resched();
361 kcb->kprobe_status = KPROBE_HIT_SS;
363 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
366 * No kprobe at this address and no active kprobe. The trap has
367 * not been caused by a kprobe breakpoint. The race of breakpoint
368 * vs. kprobe remove does not exist because on s390 as we use
369 * stop_machine to arm/disarm the breakpoints.
371 preempt_enable_no_resched();
374 NOKPROBE_SYMBOL(kprobe_handler);
376 void arch_kretprobe_fixup_return(struct pt_regs *regs,
377 kprobe_opcode_t *correct_ret_addr)
379 /* Replace fake return address with real one. */
380 regs->gprs[14] = (unsigned long)correct_ret_addr;
382 NOKPROBE_SYMBOL(arch_kretprobe_fixup_return);
385 * Called from __kretprobe_trampoline
387 void trampoline_probe_handler(struct pt_regs *regs)
389 kretprobe_trampoline_handler(regs, (void *)regs->gprs[15]);
391 NOKPROBE_SYMBOL(trampoline_probe_handler);
393 /* assembler function that handles the kretprobes must not be probed itself */
394 NOKPROBE_SYMBOL(__kretprobe_trampoline);
397 * Called after single-stepping. p->addr is the address of the
398 * instruction whose first byte has been replaced by the "breakpoint"
399 * instruction. To avoid the SMP problems that can occur when we
400 * temporarily put back the original opcode to single-step, we
401 * single-stepped a copy of the instruction. The address of this
402 * copy is p->ainsn.insn.
404 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
406 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
407 unsigned long ip = regs->psw.addr;
408 int fixup = probe_get_fixup_type(p->ainsn.insn);
410 if (fixup & FIXUP_PSW_NORMAL)
411 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
413 if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
414 int ilen = insn_length(p->ainsn.insn[0] >> 8);
415 if (ip - (unsigned long) p->ainsn.insn == ilen)
416 ip = (unsigned long) p->addr + ilen;
419 if (fixup & FIXUP_RETURN_REGISTER) {
420 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
421 regs->gprs[reg] += (unsigned long) p->addr -
422 (unsigned long) p->ainsn.insn;
425 disable_singlestep(kcb, regs, ip);
427 NOKPROBE_SYMBOL(resume_execution);
429 static int post_kprobe_handler(struct pt_regs *regs)
431 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
432 struct kprobe *p = kprobe_running();
437 resume_execution(p, regs);
438 if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
439 kcb->kprobe_status = KPROBE_HIT_SSDONE;
440 p->post_handler(p, regs, 0);
443 preempt_enable_no_resched();
446 * if somebody else is singlestepping across a probe point, psw mask
447 * will have PER set, in which case, continue the remaining processing
448 * of do_single_step, as if this is not a probe hit.
450 if (regs->psw.mask & PSW_MASK_PER)
455 NOKPROBE_SYMBOL(post_kprobe_handler);
457 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
459 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
460 struct kprobe *p = kprobe_running();
462 switch(kcb->kprobe_status) {
466 * We are here because the instruction being single
467 * stepped caused a page fault. We reset the current
468 * kprobe and the nip points back to the probe address
469 * and allow the page fault handler to continue as a
472 disable_singlestep(kcb, regs, (unsigned long) p->addr);
474 preempt_enable_no_resched();
476 case KPROBE_HIT_ACTIVE:
477 case KPROBE_HIT_SSDONE:
479 * In case the user-specified fault handler returned
480 * zero, try to fix up.
482 if (fixup_exception(regs))
485 * fixup_exception() could not handle it,
486 * Let do_page_fault() fix it.
494 NOKPROBE_SYMBOL(kprobe_trap_handler);
496 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
500 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
502 ret = kprobe_trap_handler(regs, trapnr);
503 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
504 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
507 NOKPROBE_SYMBOL(kprobe_fault_handler);
510 * Wrapper routine to for handling exceptions.
512 int kprobe_exceptions_notify(struct notifier_block *self,
513 unsigned long val, void *data)
515 struct die_args *args = (struct die_args *) data;
516 struct pt_regs *regs = args->regs;
517 int ret = NOTIFY_DONE;
519 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
524 if (kprobe_handler(regs))
528 if (post_kprobe_handler(regs))
532 if (!preemptible() && kprobe_running() &&
533 kprobe_trap_handler(regs, args->trapnr))
540 if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
541 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
545 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
547 int __init arch_init_kprobes(void)
552 int arch_trampoline_kprobe(struct kprobe *p)
556 NOKPROBE_SYMBOL(arch_trampoline_kprobe);