arch/s390/kernel/kprobes.c

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