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(s390_insn);
  31
  32 static int insn_page_in_use;
  33 static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);
  34
  35 static void *alloc_s390_insn_page(void)
  36 {
  37         if (xchg(&insn_page_in_use, 1) == 1)
  38                 return NULL;
  39         set_memory_x((unsigned long) &insn_page, 1);
  40         return &insn_page;
  41 }
  42
  43 static void free_s390_insn_page(void *page)
  44 {
  45         set_memory_nx((unsigned long) page, 1);
  46         xchg(&insn_page_in_use, 0);
  47 }
  48
  49 struct kprobe_insn_cache kprobe_s390_insn_slots = {
  50         .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
  51         .alloc = alloc_s390_insn_page,
  52         .free = free_s390_insn_page,
  53         .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
  54         .insn_size = MAX_INSN_SIZE,
  55 };
  56
  57 static void copy_instruction(struct kprobe *p)
  58 {
  59         unsigned long ip = (unsigned long) p->addr;
  60         s64 disp, new_disp;
  61         u64 addr, new_addr;
  62
  63         if (ftrace_location(ip) == ip) {
  64                 /*
  65                  * If kprobes patches the instruction that is morphed by
  66                  * ftrace make sure that kprobes always sees the branch
  67                  * "jg .+24" that skips the mcount block or the "brcl 0,0"
  68                  * in case of hotpatch.
  69                  */
  70                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
  71                 p->ainsn.is_ftrace_insn = 1;
  72         } else
  73                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
  74         p->opcode = p->ainsn.insn[0];
  75         if (!probe_is_insn_relative_long(p->ainsn.insn))
  76                 return;
  77         /*
  78          * For pc-relative instructions in RIL-b or RIL-c format patch the
  79          * RI2 displacement field. We have already made sure that the insn
  80          * slot for the patched instruction is within the same 2GB area
  81          * as the original instruction (either kernel image or module area).
  82          * Therefore the new displacement will always fit.
  83          */
  84         disp = *(s32 *)&p->ainsn.insn[1];
  85         addr = (u64)(unsigned long)p->addr;
  86         new_addr = (u64)(unsigned long)p->ainsn.insn;
  87         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
  88         *(s32 *)&p->ainsn.insn[1] = new_disp;
  89 }
  90 NOKPROBE_SYMBOL(copy_instruction);
  91
  92 static inline int is_kernel_addr(void *addr)
  93 {
  94         return addr < (void *)_end;
  95 }
  96
  97 static int s390_get_insn_slot(struct kprobe *p)
  98 {
  99         /*
 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.
 103          */
 104         p->ainsn.insn = NULL;
 105         if (is_kernel_addr(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;
 110 }
 111 NOKPROBE_SYMBOL(s390_get_insn_slot);
 112
 113 static void s390_free_insn_slot(struct kprobe *p)
 114 {
 115         if (!p->ainsn.insn)
 116                 return;
 117         if (is_kernel_addr(p->addr))
 118                 free_s390_insn_slot(p->ainsn.insn, 0);
 119         else
 120                 free_insn_slot(p->ainsn.insn, 0);
 121         p->ainsn.insn = NULL;
 122 }
 123 NOKPROBE_SYMBOL(s390_free_insn_slot);
 124
 125 int arch_prepare_kprobe(struct kprobe *p)
 126 {
 127         if ((unsigned long) p->addr & 0x01)
 128                 return -EINVAL;
 129         /* Make sure the probe isn't going on a difficult instruction */
 130         if (probe_is_prohibited_opcode(p->addr))
 131                 return -EINVAL;
 132         if (s390_get_insn_slot(p))
 133                 return -ENOMEM;
 134         copy_instruction(p);
 135         return 0;
 136 }
 137 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 138
 139 int arch_check_ftrace_location(struct kprobe *p)
 140 {
 141         return 0;
 142 }
 143
 144 struct swap_insn_args {
 145         struct kprobe *p;
 146         unsigned int arm_kprobe : 1;
 147 };
 148
 149 static int swap_instruction(void *data)
 150 {
 151         struct swap_insn_args *args = data;
 152         struct ftrace_insn new_insn, *insn;
 153         struct kprobe *p = args->p;
 154         size_t len;
 155
 156         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
 157         len = sizeof(new_insn.opc);
 158         if (!p->ainsn.is_ftrace_insn)
 159                 goto skip_ftrace;
 160         len = sizeof(new_insn);
 161         insn = (struct ftrace_insn *) p->addr;
 162         if (args->arm_kprobe) {
 163                 if (is_ftrace_nop(insn))
 164                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
 165                 else
 166                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
 167         } else {
 168                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
 169                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
 170                         ftrace_generate_nop_insn(&new_insn);
 171         }
 172 skip_ftrace:
 173         s390_kernel_write(p->addr, &new_insn, len);
 174         return 0;
 175 }
 176 NOKPROBE_SYMBOL(swap_instruction);
 177
 178 void arch_arm_kprobe(struct kprobe *p)
 179 {
 180         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 181
 182         stop_machine_cpuslocked(swap_instruction, &args, NULL);
 183 }
 184 NOKPROBE_SYMBOL(arch_arm_kprobe);
 185
 186 void arch_disarm_kprobe(struct kprobe *p)
 187 {
 188         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 189
 190         stop_machine_cpuslocked(swap_instruction, &args, NULL);
 191 }
 192 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 193
 194 void arch_remove_kprobe(struct kprobe *p)
 195 {
 196         s390_free_insn_slot(p);
 197 }
 198 NOKPROBE_SYMBOL(arch_remove_kprobe);
 199
 200 static void enable_singlestep(struct kprobe_ctlblk *kcb,
 201                               struct pt_regs *regs,
 202                               unsigned long ip)
 203 {
 204         struct per_regs per_kprobe;
 205
 206         /* Set up the PER control registers %cr9-%cr11 */
 207         per_kprobe.control = PER_EVENT_IFETCH;
 208         per_kprobe.start = ip;
 209         per_kprobe.end = ip;
 210
 211         /* Save control regs and psw mask */
 212         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 213         kcb->kprobe_saved_imask = regs->psw.mask &
 214                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 215
 216         /* Set PER control regs, turns on single step for the given address */
 217         __ctl_load(per_kprobe, 9, 11);
 218         regs->psw.mask |= PSW_MASK_PER;
 219         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 220         regs->psw.addr = ip;
 221 }
 222 NOKPROBE_SYMBOL(enable_singlestep);
 223
 224 static void disable_singlestep(struct kprobe_ctlblk *kcb,
 225                                struct pt_regs *regs,
 226                                unsigned long ip)
 227 {
 228         /* Restore control regs and psw mask, set new psw address */
 229         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 230         regs->psw.mask &= ~PSW_MASK_PER;
 231         regs->psw.mask |= kcb->kprobe_saved_imask;
 232         regs->psw.addr = ip;
 233 }
 234 NOKPROBE_SYMBOL(disable_singlestep);
 235
 236 /*
 237  * Activate a kprobe by storing its pointer to current_kprobe. The
 238  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 239  * two kprobes can be active, see KPROBE_REENTER.
 240  */
 241 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 242 {
 243         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
 244         kcb->prev_kprobe.status = kcb->kprobe_status;
 245         __this_cpu_write(current_kprobe, p);
 246 }
 247 NOKPROBE_SYMBOL(push_kprobe);
 248
 249 /*
 250  * Deactivate a kprobe by backing up to the previous state. If the
 251  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 252  * for any other state prev_kprobe.kp will be NULL.
 253  */
 254 static void pop_kprobe(struct kprobe_ctlblk *kcb)
 255 {
 256         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 257         kcb->kprobe_status = kcb->prev_kprobe.status;
 258 }
 259 NOKPROBE_SYMBOL(pop_kprobe);
 260
 261 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 262 {
 263         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 264
 265         /* Replace the return addr with trampoline addr */
 266         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 267 }
 268 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 269
 270 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
 271 {
 272         switch (kcb->kprobe_status) {
 273         case KPROBE_HIT_SSDONE:
 274         case KPROBE_HIT_ACTIVE:
 275                 kprobes_inc_nmissed_count(p);
 276                 break;
 277         case KPROBE_HIT_SS:
 278         case KPROBE_REENTER:
 279         default:
 280                 /*
 281                  * A kprobe on the code path to single step an instruction
 282                  * is a BUG. The code path resides in the .kprobes.text
 283                  * section and is executed with interrupts disabled.
 284                  */
 285                 pr_err("Invalid kprobe detected.\n");
 286                 dump_kprobe(p);
 287                 BUG();
 288         }
 289 }
 290 NOKPROBE_SYMBOL(kprobe_reenter_check);
 291
 292 static int kprobe_handler(struct pt_regs *regs)
 293 {
 294         struct kprobe_ctlblk *kcb;
 295         struct kprobe *p;
 296
 297         /*
 298          * We want to disable preemption for the entire duration of kprobe
 299          * processing. That includes the calls to the pre/post handlers
 300          * and single stepping the kprobe instruction.
 301          */
 302         preempt_disable();
 303         kcb = get_kprobe_ctlblk();
 304         p = get_kprobe((void *)(regs->psw.addr - 2));
 305
 306         if (p) {
 307                 if (kprobe_running()) {
 308                         /*
 309                          * We have hit a kprobe while another is still
 310                          * active. This can happen in the pre and post
 311                          * handler. Single step the instruction of the
 312                          * new probe but do not call any handler function
 313                          * of this secondary kprobe.
 314                          * push_kprobe and pop_kprobe saves and restores
 315                          * the currently active kprobe.
 316                          */
 317                         kprobe_reenter_check(kcb, p);
 318                         push_kprobe(kcb, p);
 319                         kcb->kprobe_status = KPROBE_REENTER;
 320                 } else {
 321                         /*
 322                          * If we have no pre-handler or it returned 0, we
 323                          * continue with single stepping. If we have a
 324                          * pre-handler and it returned non-zero, it prepped
 325                          * for changing execution path, so get out doing
 326                          * nothing more here.
 327                          */
 328                         push_kprobe(kcb, p);
 329                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 330                         if (p->pre_handler && p->pre_handler(p, regs)) {
 331                                 pop_kprobe(kcb);
 332                                 preempt_enable_no_resched();
 333                                 return 1;
 334                         }
 335                         kcb->kprobe_status = KPROBE_HIT_SS;
 336                 }
 337                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 338                 return 1;
 339         } /* else:
 340            * No kprobe at this address and no active kprobe. The trap has
 341            * not been caused by a kprobe breakpoint. The race of breakpoint
 342            * vs. kprobe remove does not exist because on s390 as we use
 343            * stop_machine to arm/disarm the breakpoints.
 344            */
 345         preempt_enable_no_resched();
 346         return 0;
 347 }
 348 NOKPROBE_SYMBOL(kprobe_handler);
 349
 350 /*
 351  * Function return probe trampoline:
 352  *      - init_kprobes() establishes a probepoint here
 353  *      - When the probed function returns, this probe
 354  *              causes the handlers to fire
 355  */
 356 static void __used kretprobe_trampoline_holder(void)
 357 {
 358         asm volatile(".global kretprobe_trampoline\n"
 359                      "kretprobe_trampoline: bcr 0,0\n");
 360 }
 361
 362 /*
 363  * Called when the probe at kretprobe trampoline is hit
 364  */
 365 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 366 {
 367         struct kretprobe_instance *ri;
 368         struct hlist_head *head, empty_rp;
 369         struct hlist_node *tmp;
 370         unsigned long flags, orig_ret_address;
 371         unsigned long trampoline_address;
 372         kprobe_opcode_t *correct_ret_addr;
 373
 374         INIT_HLIST_HEAD(&empty_rp);
 375         kretprobe_hash_lock(current, &head, &flags);
 376
 377         /*
 378          * It is possible to have multiple instances associated with a given
 379          * task either because an multiple functions in the call path
 380          * have a return probe installed on them, and/or more than one return
 381          * return probe was registered for a target function.
 382          *
 383          * We can handle this because:
 384          *     - instances are always inserted at the head of the list
 385          *     - when multiple return probes are registered for the same
 386          *       function, the first instance's ret_addr will point to the
 387          *       real return address, and all the rest will point to
 388          *       kretprobe_trampoline
 389          */
 390         ri = NULL;
 391         orig_ret_address = 0;
 392         correct_ret_addr = NULL;
 393         trampoline_address = (unsigned long) &kretprobe_trampoline;
 394         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 395                 if (ri->task != current)
 396                         /* another task is sharing our hash bucket */
 397                         continue;
 398
 399                 orig_ret_address = (unsigned long) ri->ret_addr;
 400
 401                 if (orig_ret_address != trampoline_address)
 402                         /*
 403                          * This is the real return address. Any other
 404                          * instances associated with this task are for
 405                          * other calls deeper on the call stack
 406                          */
 407                         break;
 408         }
 409
 410         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 411
 412         correct_ret_addr = ri->ret_addr;
 413         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 414                 if (ri->task != current)
 415                         /* another task is sharing our hash bucket */
 416                         continue;
 417
 418                 orig_ret_address = (unsigned long) ri->ret_addr;
 419
 420                 if (ri->rp && ri->rp->handler) {
 421                         ri->ret_addr = correct_ret_addr;
 422                         ri->rp->handler(ri, regs);
 423                 }
 424
 425                 recycle_rp_inst(ri, &empty_rp);
 426
 427                 if (orig_ret_address != trampoline_address)
 428                         /*
 429                          * This is the real return address. Any other
 430                          * instances associated with this task are for
 431                          * other calls deeper on the call stack
 432                          */
 433                         break;
 434         }
 435
 436         regs->psw.addr = orig_ret_address;
 437
 438         kretprobe_hash_unlock(current, &flags);
 439
 440         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 441                 hlist_del(&ri->hlist);
 442                 kfree(ri);
 443         }
 444         /*
 445          * By returning a non-zero value, we are telling
 446          * kprobe_handler() that we don't want the post_handler
 447          * to run (and have re-enabled preemption)
 448          */
 449         return 1;
 450 }
 451 NOKPROBE_SYMBOL(trampoline_probe_handler);
 452
 453 /*
 454  * Called after single-stepping.  p->addr is the address of the
 455  * instruction whose first byte has been replaced by the "breakpoint"
 456  * instruction.  To avoid the SMP problems that can occur when we
 457  * temporarily put back the original opcode to single-step, we
 458  * single-stepped a copy of the instruction.  The address of this
 459  * copy is p->ainsn.insn.
 460  */
 461 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 462 {
 463         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 464         unsigned long ip = regs->psw.addr;
 465         int fixup = probe_get_fixup_type(p->ainsn.insn);
 466
 467         /* Check if the kprobes location is an enabled ftrace caller */
 468         if (p->ainsn.is_ftrace_insn) {
 469                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
 470                 struct ftrace_insn call_insn;
 471
 472                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
 473                 /*
 474                  * A kprobe on an enabled ftrace call site actually single
 475                  * stepped an unconditional branch (ftrace nop equivalent).
 476                  * Now we need to fixup things and pretend that a brasl r0,...
 477                  * was executed instead.
 478                  */
 479                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
 480                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
 481                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
 482                 }
 483         }
 484
 485         if (fixup & FIXUP_PSW_NORMAL)
 486                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 487
 488         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 489                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 490                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 491                         ip = (unsigned long) p->addr + ilen;
 492         }
 493
 494         if (fixup & FIXUP_RETURN_REGISTER) {
 495                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 496                 regs->gprs[reg] += (unsigned long) p->addr -
 497                                    (unsigned long) p->ainsn.insn;
 498         }
 499
 500         disable_singlestep(kcb, regs, ip);
 501 }
 502 NOKPROBE_SYMBOL(resume_execution);
 503
 504 static int post_kprobe_handler(struct pt_regs *regs)
 505 {
 506         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 507         struct kprobe *p = kprobe_running();
 508
 509         if (!p)
 510                 return 0;
 511
 512         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 513                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 514                 p->post_handler(p, regs, 0);
 515         }
 516
 517         resume_execution(p, regs);
 518         pop_kprobe(kcb);
 519         preempt_enable_no_resched();
 520
 521         /*
 522          * if somebody else is singlestepping across a probe point, psw mask
 523          * will have PER set, in which case, continue the remaining processing
 524          * of do_single_step, as if this is not a probe hit.
 525          */
 526         if (regs->psw.mask & PSW_MASK_PER)
 527                 return 0;
 528
 529         return 1;
 530 }
 531 NOKPROBE_SYMBOL(post_kprobe_handler);
 532
 533 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 534 {
 535         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 536         struct kprobe *p = kprobe_running();
 537         const struct exception_table_entry *entry;
 538
 539         switch(kcb->kprobe_status) {
 540         case KPROBE_HIT_SS:
 541         case KPROBE_REENTER:
 542                 /*
 543                  * We are here because the instruction being single
 544                  * stepped caused a page fault. We reset the current
 545                  * kprobe and the nip points back to the probe address
 546                  * and allow the page fault handler to continue as a
 547                  * normal page fault.
 548                  */
 549                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 550                 pop_kprobe(kcb);
 551                 preempt_enable_no_resched();
 552                 break;
 553         case KPROBE_HIT_ACTIVE:
 554         case KPROBE_HIT_SSDONE:
 555                 /*
 556                  * We increment the nmissed count for accounting,
 557                  * we can also use npre/npostfault count for accounting
 558                  * these specific fault cases.
 559                  */
 560                 kprobes_inc_nmissed_count(p);
 561
 562                 /*
 563                  * We come here because instructions in the pre/post
 564                  * handler caused the page_fault, this could happen
 565                  * if handler tries to access user space by
 566                  * copy_from_user(), get_user() etc. Let the
 567                  * user-specified handler try to fix it first.
 568                  */
 569                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 570                         return 1;
 571
 572                 /*
 573                  * In case the user-specified fault handler returned
 574                  * zero, try to fix up.
 575                  */
 576                 entry = s390_search_extables(regs->psw.addr);
 577                 if (entry) {
 578                         regs->psw.addr = extable_fixup(entry);
 579                         return 1;
 580                 }
 581
 582                 /*
 583                  * fixup_exception() could not handle it,
 584                  * Let do_page_fault() fix it.
 585                  */
 586                 break;
 587         default:
 588                 break;
 589         }
 590         return 0;
 591 }
 592 NOKPROBE_SYMBOL(kprobe_trap_handler);
 593
 594 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 595 {
 596         int ret;
 597
 598         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 599                 local_irq_disable();
 600         ret = kprobe_trap_handler(regs, trapnr);
 601         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 602                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 603         return ret;
 604 }
 605 NOKPROBE_SYMBOL(kprobe_fault_handler);
 606
 607 /*
 608  * Wrapper routine to for handling exceptions.
 609  */
 610 int kprobe_exceptions_notify(struct notifier_block *self,
 611                              unsigned long val, void *data)
 612 {
 613         struct die_args *args = (struct die_args *) data;
 614         struct pt_regs *regs = args->regs;
 615         int ret = NOTIFY_DONE;
 616
 617         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 618                 local_irq_disable();
 619
 620         switch (val) {
 621         case DIE_BPT:
 622                 if (kprobe_handler(regs))
 623                         ret = NOTIFY_STOP;
 624                 break;
 625         case DIE_SSTEP:
 626                 if (post_kprobe_handler(regs))
 627                         ret = NOTIFY_STOP;
 628                 break;
 629         case DIE_TRAP:
 630                 if (!preemptible() && kprobe_running() &&
 631                     kprobe_trap_handler(regs, args->trapnr))
 632                         ret = NOTIFY_STOP;
 633                 break;
 634         default:
 635                 break;
 636         }
 637
 638         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 639                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 640
 641         return ret;
 642 }
 643 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 644
 645 static struct kprobe trampoline = {
 646         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 647         .pre_handler = trampoline_probe_handler
 648 };
 649
 650 int __init arch_init_kprobes(void)
 651 {
 652         return register_kprobe(&trampoline);
 653 }
 654
 655 int arch_trampoline_kprobe(struct kprobe *p)
 656 {
 657         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 658 }
 659 NOKPROBE_SYMBOL(arch_trampoline_kprobe);