arch/s390/kernel/kprobes.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright IBM Corp. 2002, 2006
  19  *
  20  * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
  21  */
  22
  23 #include <linux/kprobes.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/preempt.h>
  26 #include <linux/stop_machine.h>
  27 #include <linux/kdebug.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/extable.h>
  30 #include <linux/module.h>
  31 #include <linux/slab.h>
  32 #include <linux/hardirq.h>
  33 #include <linux/ftrace.h>
  34 #include <asm/cacheflush.h>
  35 #include <asm/sections.h>
  36 #include <asm/uaccess.h>
  37 #include <asm/dis.h>
  38
  39 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  40 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  41
  42 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
  43
  44 DEFINE_INSN_CACHE_OPS(dmainsn);
  45
  46 static void *alloc_dmainsn_page(void)
  47 {
  48         return (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
  49 }
  50
  51 static void free_dmainsn_page(void *page)
  52 {
  53         free_page((unsigned long)page);
  54 }
  55
  56 struct kprobe_insn_cache kprobe_dmainsn_slots = {
  57         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
  58         .alloc = alloc_dmainsn_page,
  59         .free = free_dmainsn_page,
  60         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
  61         .insn_size = MAX_INSN_SIZE,
  62 };
  63
  64 static void copy_instruction(struct kprobe *p)
  65 {
  66         unsigned long ip = (unsigned long) p->addr;
  67         s64 disp, new_disp;
  68         u64 addr, new_addr;
  69
  70         if (ftrace_location(ip) == ip) {
  71                 /*
  72                  * If kprobes patches the instruction that is morphed by
  73                  * ftrace make sure that kprobes always sees the branch
  74                  * "jg .+24" that skips the mcount block or the "brcl 0,0"
  75                  * in case of hotpatch.
  76                  */
  77                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
  78                 p->ainsn.is_ftrace_insn = 1;
  79         } else
  80                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
  81         p->opcode = p->ainsn.insn[0];
  82         if (!probe_is_insn_relative_long(p->ainsn.insn))
  83                 return;
  84         /*
  85          * For pc-relative instructions in RIL-b or RIL-c format patch the
  86          * RI2 displacement field. We have already made sure that the insn
  87          * slot for the patched instruction is within the same 2GB area
  88          * as the original instruction (either kernel image or module area).
  89          * Therefore the new displacement will always fit.
  90          */
  91         disp = *(s32 *)&p->ainsn.insn[1];
  92         addr = (u64)(unsigned long)p->addr;
  93         new_addr = (u64)(unsigned long)p->ainsn.insn;
  94         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
  95         *(s32 *)&p->ainsn.insn[1] = new_disp;
  96 }
  97 NOKPROBE_SYMBOL(copy_instruction);
  98
  99 static inline int is_kernel_addr(void *addr)
 100 {
 101         return addr < (void *)_end;
 102 }
 103
 104 static int s390_get_insn_slot(struct kprobe *p)
 105 {
 106         /*
 107          * Get an insn slot that is within the same 2GB area like the original
 108          * instruction. That way instructions with a 32bit signed displacement
 109          * field can be patched and executed within the insn slot.
 110          */
 111         p->ainsn.insn = NULL;
 112         if (is_kernel_addr(p->addr))
 113                 p->ainsn.insn = get_dmainsn_slot();
 114         else if (is_module_addr(p->addr))
 115                 p->ainsn.insn = get_insn_slot();
 116         return p->ainsn.insn ? 0 : -ENOMEM;
 117 }
 118 NOKPROBE_SYMBOL(s390_get_insn_slot);
 119
 120 static void s390_free_insn_slot(struct kprobe *p)
 121 {
 122         if (!p->ainsn.insn)
 123                 return;
 124         if (is_kernel_addr(p->addr))
 125                 free_dmainsn_slot(p->ainsn.insn, 0);
 126         else
 127                 free_insn_slot(p->ainsn.insn, 0);
 128         p->ainsn.insn = NULL;
 129 }
 130 NOKPROBE_SYMBOL(s390_free_insn_slot);
 131
 132 int arch_prepare_kprobe(struct kprobe *p)
 133 {
 134         if ((unsigned long) p->addr & 0x01)
 135                 return -EINVAL;
 136         /* Make sure the probe isn't going on a difficult instruction */
 137         if (probe_is_prohibited_opcode(p->addr))
 138                 return -EINVAL;
 139         if (s390_get_insn_slot(p))
 140                 return -ENOMEM;
 141         copy_instruction(p);
 142         return 0;
 143 }
 144 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 145
 146 int arch_check_ftrace_location(struct kprobe *p)
 147 {
 148         return 0;
 149 }
 150
 151 struct swap_insn_args {
 152         struct kprobe *p;
 153         unsigned int arm_kprobe : 1;
 154 };
 155
 156 static int swap_instruction(void *data)
 157 {
 158         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 159         unsigned long status = kcb->kprobe_status;
 160         struct swap_insn_args *args = data;
 161         struct ftrace_insn new_insn, *insn;
 162         struct kprobe *p = args->p;
 163         size_t len;
 164
 165         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
 166         len = sizeof(new_insn.opc);
 167         if (!p->ainsn.is_ftrace_insn)
 168                 goto skip_ftrace;
 169         len = sizeof(new_insn);
 170         insn = (struct ftrace_insn *) p->addr;
 171         if (args->arm_kprobe) {
 172                 if (is_ftrace_nop(insn))
 173                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
 174                 else
 175                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
 176         } else {
 177                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
 178                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
 179                         ftrace_generate_nop_insn(&new_insn);
 180         }
 181 skip_ftrace:
 182         kcb->kprobe_status = KPROBE_SWAP_INST;
 183         s390_kernel_write(p->addr, &new_insn, len);
 184         kcb->kprobe_status = status;
 185         return 0;
 186 }
 187 NOKPROBE_SYMBOL(swap_instruction);
 188
 189 void arch_arm_kprobe(struct kprobe *p)
 190 {
 191         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 192
 193         stop_machine(swap_instruction, &args, NULL);
 194 }
 195 NOKPROBE_SYMBOL(arch_arm_kprobe);
 196
 197 void arch_disarm_kprobe(struct kprobe *p)
 198 {
 199         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 200
 201         stop_machine(swap_instruction, &args, NULL);
 202 }
 203 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 204
 205 void arch_remove_kprobe(struct kprobe *p)
 206 {
 207         s390_free_insn_slot(p);
 208 }
 209 NOKPROBE_SYMBOL(arch_remove_kprobe);
 210
 211 static void enable_singlestep(struct kprobe_ctlblk *kcb,
 212                               struct pt_regs *regs,
 213                               unsigned long ip)
 214 {
 215         struct per_regs per_kprobe;
 216
 217         /* Set up the PER control registers %cr9-%cr11 */
 218         per_kprobe.control = PER_EVENT_IFETCH;
 219         per_kprobe.start = ip;
 220         per_kprobe.end = ip;
 221
 222         /* Save control regs and psw mask */
 223         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 224         kcb->kprobe_saved_imask = regs->psw.mask &
 225                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 226
 227         /* Set PER control regs, turns on single step for the given address */
 228         __ctl_load(per_kprobe, 9, 11);
 229         regs->psw.mask |= PSW_MASK_PER;
 230         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 231         regs->psw.addr = ip;
 232 }
 233 NOKPROBE_SYMBOL(enable_singlestep);
 234
 235 static void disable_singlestep(struct kprobe_ctlblk *kcb,
 236                                struct pt_regs *regs,
 237                                unsigned long ip)
 238 {
 239         /* Restore control regs and psw mask, set new psw address */
 240         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 241         regs->psw.mask &= ~PSW_MASK_PER;
 242         regs->psw.mask |= kcb->kprobe_saved_imask;
 243         regs->psw.addr = ip;
 244 }
 245 NOKPROBE_SYMBOL(disable_singlestep);
 246
 247 /*
 248  * Activate a kprobe by storing its pointer to current_kprobe. The
 249  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 250  * two kprobes can be active, see KPROBE_REENTER.
 251  */
 252 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 253 {
 254         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
 255         kcb->prev_kprobe.status = kcb->kprobe_status;
 256         __this_cpu_write(current_kprobe, p);
 257 }
 258 NOKPROBE_SYMBOL(push_kprobe);
 259
 260 /*
 261  * Deactivate a kprobe by backing up to the previous state. If the
 262  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 263  * for any other state prev_kprobe.kp will be NULL.
 264  */
 265 static void pop_kprobe(struct kprobe_ctlblk *kcb)
 266 {
 267         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 268         kcb->kprobe_status = kcb->prev_kprobe.status;
 269 }
 270 NOKPROBE_SYMBOL(pop_kprobe);
 271
 272 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 273 {
 274         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 275
 276         /* Replace the return addr with trampoline addr */
 277         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 278 }
 279 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 280
 281 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
 282 {
 283         switch (kcb->kprobe_status) {
 284         case KPROBE_HIT_SSDONE:
 285         case KPROBE_HIT_ACTIVE:
 286                 kprobes_inc_nmissed_count(p);
 287                 break;
 288         case KPROBE_HIT_SS:
 289         case KPROBE_REENTER:
 290         default:
 291                 /*
 292                  * A kprobe on the code path to single step an instruction
 293                  * is a BUG. The code path resides in the .kprobes.text
 294                  * section and is executed with interrupts disabled.
 295                  */
 296                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 297                 dump_kprobe(p);
 298                 BUG();
 299         }
 300 }
 301 NOKPROBE_SYMBOL(kprobe_reenter_check);
 302
 303 static int kprobe_handler(struct pt_regs *regs)
 304 {
 305         struct kprobe_ctlblk *kcb;
 306         struct kprobe *p;
 307
 308         /*
 309          * We want to disable preemption for the entire duration of kprobe
 310          * processing. That includes the calls to the pre/post handlers
 311          * and single stepping the kprobe instruction.
 312          */
 313         preempt_disable();
 314         kcb = get_kprobe_ctlblk();
 315         p = get_kprobe((void *)(regs->psw.addr - 2));
 316
 317         if (p) {
 318                 if (kprobe_running()) {
 319                         /*
 320                          * We have hit a kprobe while another is still
 321                          * active. This can happen in the pre and post
 322                          * handler. Single step the instruction of the
 323                          * new probe but do not call any handler function
 324                          * of this secondary kprobe.
 325                          * push_kprobe and pop_kprobe saves and restores
 326                          * the currently active kprobe.
 327                          */
 328                         kprobe_reenter_check(kcb, p);
 329                         push_kprobe(kcb, p);
 330                         kcb->kprobe_status = KPROBE_REENTER;
 331                 } else {
 332                         /*
 333                          * If we have no pre-handler or it returned 0, we
 334                          * continue with single stepping. If we have a
 335                          * pre-handler and it returned non-zero, it prepped
 336                          * for calling the break_handler below on re-entry
 337                          * for jprobe processing, so get out doing nothing
 338                          * more here.
 339                          */
 340                         push_kprobe(kcb, p);
 341                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 342                         if (p->pre_handler && p->pre_handler(p, regs))
 343                                 return 1;
 344                         kcb->kprobe_status = KPROBE_HIT_SS;
 345                 }
 346                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 347                 return 1;
 348         } else if (kprobe_running()) {
 349                 p = __this_cpu_read(current_kprobe);
 350                 if (p->break_handler && p->break_handler(p, regs)) {
 351                         /*
 352                          * Continuation after the jprobe completed and
 353                          * caused the jprobe_return trap. The jprobe
 354                          * break_handler "returns" to the original
 355                          * function that still has the kprobe breakpoint
 356                          * installed. We continue with single stepping.
 357                          */
 358                         kcb->kprobe_status = KPROBE_HIT_SS;
 359                         enable_singlestep(kcb, regs,
 360                                           (unsigned long) p->ainsn.insn);
 361                         return 1;
 362                 } /* else:
 363                    * No kprobe at this address and the current kprobe
 364                    * has no break handler (no jprobe!). The kernel just
 365                    * exploded, let the standard trap handler pick up the
 366                    * pieces.
 367                    */
 368         } /* else:
 369            * No kprobe at this address and no active kprobe. The trap has
 370            * not been caused by a kprobe breakpoint. The race of breakpoint
 371            * vs. kprobe remove does not exist because on s390 as we use
 372            * stop_machine to arm/disarm the breakpoints.
 373            */
 374         preempt_enable_no_resched();
 375         return 0;
 376 }
 377 NOKPROBE_SYMBOL(kprobe_handler);
 378
 379 /*
 380  * Function return probe trampoline:
 381  *      - init_kprobes() establishes a probepoint here
 382  *      - When the probed function returns, this probe
 383  *              causes the handlers to fire
 384  */
 385 static void __used kretprobe_trampoline_holder(void)
 386 {
 387         asm volatile(".global kretprobe_trampoline\n"
 388                      "kretprobe_trampoline: bcr 0,0\n");
 389 }
 390
 391 /*
 392  * Called when the probe at kretprobe trampoline is hit
 393  */
 394 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 395 {
 396         struct kretprobe_instance *ri;
 397         struct hlist_head *head, empty_rp;
 398         struct hlist_node *tmp;
 399         unsigned long flags, orig_ret_address;
 400         unsigned long trampoline_address;
 401         kprobe_opcode_t *correct_ret_addr;
 402
 403         INIT_HLIST_HEAD(&empty_rp);
 404         kretprobe_hash_lock(current, &head, &flags);
 405
 406         /*
 407          * It is possible to have multiple instances associated with a given
 408          * task either because an multiple functions in the call path
 409          * have a return probe installed on them, and/or more than one return
 410          * return probe was registered for a target function.
 411          *
 412          * We can handle this because:
 413          *     - instances are always inserted at the head of the list
 414          *     - when multiple return probes are registered for the same
 415          *       function, the first instance's ret_addr will point to the
 416          *       real return address, and all the rest will point to
 417          *       kretprobe_trampoline
 418          */
 419         ri = NULL;
 420         orig_ret_address = 0;
 421         correct_ret_addr = NULL;
 422         trampoline_address = (unsigned long) &kretprobe_trampoline;
 423         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 424                 if (ri->task != current)
 425                         /* another task is sharing our hash bucket */
 426                         continue;
 427
 428                 orig_ret_address = (unsigned long) ri->ret_addr;
 429
 430                 if (orig_ret_address != trampoline_address)
 431                         /*
 432                          * This is the real return address. Any other
 433                          * instances associated with this task are for
 434                          * other calls deeper on the call stack
 435                          */
 436                         break;
 437         }
 438
 439         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 440
 441         correct_ret_addr = ri->ret_addr;
 442         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 443                 if (ri->task != current)
 444                         /* another task is sharing our hash bucket */
 445                         continue;
 446
 447                 orig_ret_address = (unsigned long) ri->ret_addr;
 448
 449                 if (ri->rp && ri->rp->handler) {
 450                         ri->ret_addr = correct_ret_addr;
 451                         ri->rp->handler(ri, regs);
 452                 }
 453
 454                 recycle_rp_inst(ri, &empty_rp);
 455
 456                 if (orig_ret_address != trampoline_address)
 457                         /*
 458                          * This is the real return address. Any other
 459                          * instances associated with this task are for
 460                          * other calls deeper on the call stack
 461                          */
 462                         break;
 463         }
 464
 465         regs->psw.addr = orig_ret_address;
 466
 467         pop_kprobe(get_kprobe_ctlblk());
 468         kretprobe_hash_unlock(current, &flags);
 469         preempt_enable_no_resched();
 470
 471         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 472                 hlist_del(&ri->hlist);
 473                 kfree(ri);
 474         }
 475         /*
 476          * By returning a non-zero value, we are telling
 477          * kprobe_handler() that we don't want the post_handler
 478          * to run (and have re-enabled preemption)
 479          */
 480         return 1;
 481 }
 482 NOKPROBE_SYMBOL(trampoline_probe_handler);
 483
 484 /*
 485  * Called after single-stepping.  p->addr is the address of the
 486  * instruction whose first byte has been replaced by the "breakpoint"
 487  * instruction.  To avoid the SMP problems that can occur when we
 488  * temporarily put back the original opcode to single-step, we
 489  * single-stepped a copy of the instruction.  The address of this
 490  * copy is p->ainsn.insn.
 491  */
 492 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 493 {
 494         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 495         unsigned long ip = regs->psw.addr;
 496         int fixup = probe_get_fixup_type(p->ainsn.insn);
 497
 498         /* Check if the kprobes location is an enabled ftrace caller */
 499         if (p->ainsn.is_ftrace_insn) {
 500                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
 501                 struct ftrace_insn call_insn;
 502
 503                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
 504                 /*
 505                  * A kprobe on an enabled ftrace call site actually single
 506                  * stepped an unconditional branch (ftrace nop equivalent).
 507                  * Now we need to fixup things and pretend that a brasl r0,...
 508                  * was executed instead.
 509                  */
 510                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
 511                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
 512                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
 513                 }
 514         }
 515
 516         if (fixup & FIXUP_PSW_NORMAL)
 517                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 518
 519         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 520                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 521                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 522                         ip = (unsigned long) p->addr + ilen;
 523         }
 524
 525         if (fixup & FIXUP_RETURN_REGISTER) {
 526                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 527                 regs->gprs[reg] += (unsigned long) p->addr -
 528                                    (unsigned long) p->ainsn.insn;
 529         }
 530
 531         disable_singlestep(kcb, regs, ip);
 532 }
 533 NOKPROBE_SYMBOL(resume_execution);
 534
 535 static int post_kprobe_handler(struct pt_regs *regs)
 536 {
 537         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 538         struct kprobe *p = kprobe_running();
 539
 540         if (!p)
 541                 return 0;
 542
 543         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 544                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 545                 p->post_handler(p, regs, 0);
 546         }
 547
 548         resume_execution(p, regs);
 549         pop_kprobe(kcb);
 550         preempt_enable_no_resched();
 551
 552         /*
 553          * if somebody else is singlestepping across a probe point, psw mask
 554          * will have PER set, in which case, continue the remaining processing
 555          * of do_single_step, as if this is not a probe hit.
 556          */
 557         if (regs->psw.mask & PSW_MASK_PER)
 558                 return 0;
 559
 560         return 1;
 561 }
 562 NOKPROBE_SYMBOL(post_kprobe_handler);
 563
 564 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 565 {
 566         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 567         struct kprobe *p = kprobe_running();
 568         const struct exception_table_entry *entry;
 569
 570         switch(kcb->kprobe_status) {
 571         case KPROBE_SWAP_INST:
 572                 /* We are here because the instruction replacement failed */
 573                 return 0;
 574         case KPROBE_HIT_SS:
 575         case KPROBE_REENTER:
 576                 /*
 577                  * We are here because the instruction being single
 578                  * stepped caused a page fault. We reset the current
 579                  * kprobe and the nip points back to the probe address
 580                  * and allow the page fault handler to continue as a
 581                  * normal page fault.
 582                  */
 583                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 584                 pop_kprobe(kcb);
 585                 preempt_enable_no_resched();
 586                 break;
 587         case KPROBE_HIT_ACTIVE:
 588         case KPROBE_HIT_SSDONE:
 589                 /*
 590                  * We increment the nmissed count for accounting,
 591                  * we can also use npre/npostfault count for accounting
 592                  * these specific fault cases.
 593                  */
 594                 kprobes_inc_nmissed_count(p);
 595
 596                 /*
 597                  * We come here because instructions in the pre/post
 598                  * handler caused the page_fault, this could happen
 599                  * if handler tries to access user space by
 600                  * copy_from_user(), get_user() etc. Let the
 601                  * user-specified handler try to fix it first.
 602                  */
 603                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 604                         return 1;
 605
 606                 /*
 607                  * In case the user-specified fault handler returned
 608                  * zero, try to fix up.
 609                  */
 610                 entry = search_exception_tables(regs->psw.addr);
 611                 if (entry) {
 612                         regs->psw.addr = extable_fixup(entry);
 613                         return 1;
 614                 }
 615
 616                 /*
 617                  * fixup_exception() could not handle it,
 618                  * Let do_page_fault() fix it.
 619                  */
 620                 break;
 621         default:
 622                 break;
 623         }
 624         return 0;
 625 }
 626 NOKPROBE_SYMBOL(kprobe_trap_handler);
 627
 628 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 629 {
 630         int ret;
 631
 632         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 633                 local_irq_disable();
 634         ret = kprobe_trap_handler(regs, trapnr);
 635         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 636                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 637         return ret;
 638 }
 639 NOKPROBE_SYMBOL(kprobe_fault_handler);
 640
 641 /*
 642  * Wrapper routine to for handling exceptions.
 643  */
 644 int kprobe_exceptions_notify(struct notifier_block *self,
 645                              unsigned long val, void *data)
 646 {
 647         struct die_args *args = (struct die_args *) data;
 648         struct pt_regs *regs = args->regs;
 649         int ret = NOTIFY_DONE;
 650
 651         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 652                 local_irq_disable();
 653
 654         switch (val) {
 655         case DIE_BPT:
 656                 if (kprobe_handler(regs))
 657                         ret = NOTIFY_STOP;
 658                 break;
 659         case DIE_SSTEP:
 660                 if (post_kprobe_handler(regs))
 661                         ret = NOTIFY_STOP;
 662                 break;
 663         case DIE_TRAP:
 664                 if (!preemptible() && kprobe_running() &&
 665                     kprobe_trap_handler(regs, args->trapnr))
 666                         ret = NOTIFY_STOP;
 667                 break;
 668         default:
 669                 break;
 670         }
 671
 672         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 673                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 674
 675         return ret;
 676 }
 677 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 678
 679 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 680 {
 681         struct jprobe *jp = container_of(p, struct jprobe, kp);
 682         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 683         unsigned long stack;
 684
 685         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 686
 687         /* setup return addr to the jprobe handler routine */
 688         regs->psw.addr = (unsigned long) jp->entry;
 689         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 690
 691         /* r15 is the stack pointer */
 692         stack = (unsigned long) regs->gprs[15];
 693
 694         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 695
 696         /*
 697          * jprobes use jprobe_return() which skips the normal return
 698          * path of the function, and this messes up the accounting of the
 699          * function graph tracer to get messed up.
 700          *
 701          * Pause function graph tracing while performing the jprobe function.
 702          */
 703         pause_graph_tracing();
 704         return 1;
 705 }
 706 NOKPROBE_SYMBOL(setjmp_pre_handler);
 707
 708 void jprobe_return(void)
 709 {
 710         asm volatile(".word 0x0002");
 711 }
 712 NOKPROBE_SYMBOL(jprobe_return);
 713
 714 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 715 {
 716         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 717         unsigned long stack;
 718
 719         /* It's OK to start function graph tracing again */
 720         unpause_graph_tracing();
 721
 722         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 723
 724         /* Put the regs back */
 725         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 726         /* put the stack back */
 727         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 728         preempt_enable_no_resched();
 729         return 1;
 730 }
 731 NOKPROBE_SYMBOL(longjmp_break_handler);
 732
 733 static struct kprobe trampoline = {
 734         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 735         .pre_handler = trampoline_probe_handler
 736 };
 737
 738 int __init arch_init_kprobes(void)
 739 {
 740         return register_kprobe(&trampoline);
 741 }
 742
 743 int arch_trampoline_kprobe(struct kprobe *p)
 744 {
 745         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 746 }
 747 NOKPROBE_SYMBOL(arch_trampoline_kprobe);