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 <linux/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         void *page;
  49
  50         page = (void *) __get_free_page(GFP_KERNEL | GFP_DMA);
  51         if (page)
  52                 set_memory_x((unsigned long) page, 1);
  53         return page;
  54 }
  55
  56 static void free_dmainsn_page(void *page)
  57 {
  58         set_memory_nx((unsigned long) page, 1);
  59         free_page((unsigned long)page);
  60 }
  61
  62 struct kprobe_insn_cache kprobe_dmainsn_slots = {
  63         .mutex = __MUTEX_INITIALIZER(kprobe_dmainsn_slots.mutex),
  64         .alloc = alloc_dmainsn_page,
  65         .free = free_dmainsn_page,
  66         .pages = LIST_HEAD_INIT(kprobe_dmainsn_slots.pages),
  67         .insn_size = MAX_INSN_SIZE,
  68 };
  69
  70 static void copy_instruction(struct kprobe *p)
  71 {
  72         unsigned long ip = (unsigned long) p->addr;
  73         s64 disp, new_disp;
  74         u64 addr, new_addr;
  75
  76         if (ftrace_location(ip) == ip) {
  77                 /*
  78                  * If kprobes patches the instruction that is morphed by
  79                  * ftrace make sure that kprobes always sees the branch
  80                  * "jg .+24" that skips the mcount block or the "brcl 0,0"
  81                  * in case of hotpatch.
  82                  */
  83                 ftrace_generate_nop_insn((struct ftrace_insn *)p->ainsn.insn);
  84                 p->ainsn.is_ftrace_insn = 1;
  85         } else
  86                 memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));
  87         p->opcode = p->ainsn.insn[0];
  88         if (!probe_is_insn_relative_long(p->ainsn.insn))
  89                 return;
  90         /*
  91          * For pc-relative instructions in RIL-b or RIL-c format patch the
  92          * RI2 displacement field. We have already made sure that the insn
  93          * slot for the patched instruction is within the same 2GB area
  94          * as the original instruction (either kernel image or module area).
  95          * Therefore the new displacement will always fit.
  96          */
  97         disp = *(s32 *)&p->ainsn.insn[1];
  98         addr = (u64)(unsigned long)p->addr;
  99         new_addr = (u64)(unsigned long)p->ainsn.insn;
 100         new_disp = ((addr + (disp * 2)) - new_addr) / 2;
 101         *(s32 *)&p->ainsn.insn[1] = new_disp;
 102 }
 103 NOKPROBE_SYMBOL(copy_instruction);
 104
 105 static inline int is_kernel_addr(void *addr)
 106 {
 107         return addr < (void *)_end;
 108 }
 109
 110 static int s390_get_insn_slot(struct kprobe *p)
 111 {
 112         /*
 113          * Get an insn slot that is within the same 2GB area like the original
 114          * instruction. That way instructions with a 32bit signed displacement
 115          * field can be patched and executed within the insn slot.
 116          */
 117         p->ainsn.insn = NULL;
 118         if (is_kernel_addr(p->addr))
 119                 p->ainsn.insn = get_dmainsn_slot();
 120         else if (is_module_addr(p->addr))
 121                 p->ainsn.insn = get_insn_slot();
 122         return p->ainsn.insn ? 0 : -ENOMEM;
 123 }
 124 NOKPROBE_SYMBOL(s390_get_insn_slot);
 125
 126 static void s390_free_insn_slot(struct kprobe *p)
 127 {
 128         if (!p->ainsn.insn)
 129                 return;
 130         if (is_kernel_addr(p->addr))
 131                 free_dmainsn_slot(p->ainsn.insn, 0);
 132         else
 133                 free_insn_slot(p->ainsn.insn, 0);
 134         p->ainsn.insn = NULL;
 135 }
 136 NOKPROBE_SYMBOL(s390_free_insn_slot);
 137
 138 int arch_prepare_kprobe(struct kprobe *p)
 139 {
 140         if ((unsigned long) p->addr & 0x01)
 141                 return -EINVAL;
 142         /* Make sure the probe isn't going on a difficult instruction */
 143         if (probe_is_prohibited_opcode(p->addr))
 144                 return -EINVAL;
 145         if (s390_get_insn_slot(p))
 146                 return -ENOMEM;
 147         copy_instruction(p);
 148         return 0;
 149 }
 150 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 151
 152 int arch_check_ftrace_location(struct kprobe *p)
 153 {
 154         return 0;
 155 }
 156
 157 struct swap_insn_args {
 158         struct kprobe *p;
 159         unsigned int arm_kprobe : 1;
 160 };
 161
 162 static int swap_instruction(void *data)
 163 {
 164         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 165         unsigned long status = kcb->kprobe_status;
 166         struct swap_insn_args *args = data;
 167         struct ftrace_insn new_insn, *insn;
 168         struct kprobe *p = args->p;
 169         size_t len;
 170
 171         new_insn.opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
 172         len = sizeof(new_insn.opc);
 173         if (!p->ainsn.is_ftrace_insn)
 174                 goto skip_ftrace;
 175         len = sizeof(new_insn);
 176         insn = (struct ftrace_insn *) p->addr;
 177         if (args->arm_kprobe) {
 178                 if (is_ftrace_nop(insn))
 179                         new_insn.disp = KPROBE_ON_FTRACE_NOP;
 180                 else
 181                         new_insn.disp = KPROBE_ON_FTRACE_CALL;
 182         } else {
 183                 ftrace_generate_call_insn(&new_insn, (unsigned long)p->addr);
 184                 if (insn->disp == KPROBE_ON_FTRACE_NOP)
 185                         ftrace_generate_nop_insn(&new_insn);
 186         }
 187 skip_ftrace:
 188         kcb->kprobe_status = KPROBE_SWAP_INST;
 189         s390_kernel_write(p->addr, &new_insn, len);
 190         kcb->kprobe_status = status;
 191         return 0;
 192 }
 193 NOKPROBE_SYMBOL(swap_instruction);
 194
 195 void arch_arm_kprobe(struct kprobe *p)
 196 {
 197         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 198
 199         stop_machine(swap_instruction, &args, NULL);
 200 }
 201 NOKPROBE_SYMBOL(arch_arm_kprobe);
 202
 203 void arch_disarm_kprobe(struct kprobe *p)
 204 {
 205         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 206
 207         stop_machine(swap_instruction, &args, NULL);
 208 }
 209 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 210
 211 void arch_remove_kprobe(struct kprobe *p)
 212 {
 213         s390_free_insn_slot(p);
 214 }
 215 NOKPROBE_SYMBOL(arch_remove_kprobe);
 216
 217 static void enable_singlestep(struct kprobe_ctlblk *kcb,
 218                               struct pt_regs *regs,
 219                               unsigned long ip)
 220 {
 221         struct per_regs per_kprobe;
 222
 223         /* Set up the PER control registers %cr9-%cr11 */
 224         per_kprobe.control = PER_EVENT_IFETCH;
 225         per_kprobe.start = ip;
 226         per_kprobe.end = ip;
 227
 228         /* Save control regs and psw mask */
 229         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 230         kcb->kprobe_saved_imask = regs->psw.mask &
 231                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 232
 233         /* Set PER control regs, turns on single step for the given address */
 234         __ctl_load(per_kprobe, 9, 11);
 235         regs->psw.mask |= PSW_MASK_PER;
 236         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 237         regs->psw.addr = ip;
 238 }
 239 NOKPROBE_SYMBOL(enable_singlestep);
 240
 241 static void disable_singlestep(struct kprobe_ctlblk *kcb,
 242                                struct pt_regs *regs,
 243                                unsigned long ip)
 244 {
 245         /* Restore control regs and psw mask, set new psw address */
 246         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 247         regs->psw.mask &= ~PSW_MASK_PER;
 248         regs->psw.mask |= kcb->kprobe_saved_imask;
 249         regs->psw.addr = ip;
 250 }
 251 NOKPROBE_SYMBOL(disable_singlestep);
 252
 253 /*
 254  * Activate a kprobe by storing its pointer to current_kprobe. The
 255  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 256  * two kprobes can be active, see KPROBE_REENTER.
 257  */
 258 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 259 {
 260         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
 261         kcb->prev_kprobe.status = kcb->kprobe_status;
 262         __this_cpu_write(current_kprobe, p);
 263 }
 264 NOKPROBE_SYMBOL(push_kprobe);
 265
 266 /*
 267  * Deactivate a kprobe by backing up to the previous state. If the
 268  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 269  * for any other state prev_kprobe.kp will be NULL.
 270  */
 271 static void pop_kprobe(struct kprobe_ctlblk *kcb)
 272 {
 273         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 274         kcb->kprobe_status = kcb->prev_kprobe.status;
 275 }
 276 NOKPROBE_SYMBOL(pop_kprobe);
 277
 278 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 279 {
 280         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 281
 282         /* Replace the return addr with trampoline addr */
 283         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 284 }
 285 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 286
 287 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
 288 {
 289         switch (kcb->kprobe_status) {
 290         case KPROBE_HIT_SSDONE:
 291         case KPROBE_HIT_ACTIVE:
 292                 kprobes_inc_nmissed_count(p);
 293                 break;
 294         case KPROBE_HIT_SS:
 295         case KPROBE_REENTER:
 296         default:
 297                 /*
 298                  * A kprobe on the code path to single step an instruction
 299                  * is a BUG. The code path resides in the .kprobes.text
 300                  * section and is executed with interrupts disabled.
 301                  */
 302                 printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 303                 dump_kprobe(p);
 304                 BUG();
 305         }
 306 }
 307 NOKPROBE_SYMBOL(kprobe_reenter_check);
 308
 309 static int kprobe_handler(struct pt_regs *regs)
 310 {
 311         struct kprobe_ctlblk *kcb;
 312         struct kprobe *p;
 313
 314         /*
 315          * We want to disable preemption for the entire duration of kprobe
 316          * processing. That includes the calls to the pre/post handlers
 317          * and single stepping the kprobe instruction.
 318          */
 319         preempt_disable();
 320         kcb = get_kprobe_ctlblk();
 321         p = get_kprobe((void *)(regs->psw.addr - 2));
 322
 323         if (p) {
 324                 if (kprobe_running()) {
 325                         /*
 326                          * We have hit a kprobe while another is still
 327                          * active. This can happen in the pre and post
 328                          * handler. Single step the instruction of the
 329                          * new probe but do not call any handler function
 330                          * of this secondary kprobe.
 331                          * push_kprobe and pop_kprobe saves and restores
 332                          * the currently active kprobe.
 333                          */
 334                         kprobe_reenter_check(kcb, p);
 335                         push_kprobe(kcb, p);
 336                         kcb->kprobe_status = KPROBE_REENTER;
 337                 } else {
 338                         /*
 339                          * If we have no pre-handler or it returned 0, we
 340                          * continue with single stepping. If we have a
 341                          * pre-handler and it returned non-zero, it prepped
 342                          * for calling the break_handler below on re-entry
 343                          * for jprobe processing, so get out doing nothing
 344                          * more here.
 345                          */
 346                         push_kprobe(kcb, p);
 347                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 348                         if (p->pre_handler && p->pre_handler(p, regs))
 349                                 return 1;
 350                         kcb->kprobe_status = KPROBE_HIT_SS;
 351                 }
 352                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 353                 return 1;
 354         } else if (kprobe_running()) {
 355                 p = __this_cpu_read(current_kprobe);
 356                 if (p->break_handler && p->break_handler(p, regs)) {
 357                         /*
 358                          * Continuation after the jprobe completed and
 359                          * caused the jprobe_return trap. The jprobe
 360                          * break_handler "returns" to the original
 361                          * function that still has the kprobe breakpoint
 362                          * installed. We continue with single stepping.
 363                          */
 364                         kcb->kprobe_status = KPROBE_HIT_SS;
 365                         enable_singlestep(kcb, regs,
 366                                           (unsigned long) p->ainsn.insn);
 367                         return 1;
 368                 } /* else:
 369                    * No kprobe at this address and the current kprobe
 370                    * has no break handler (no jprobe!). The kernel just
 371                    * exploded, let the standard trap handler pick up the
 372                    * pieces.
 373                    */
 374         } /* else:
 375            * No kprobe at this address and no active kprobe. The trap has
 376            * not been caused by a kprobe breakpoint. The race of breakpoint
 377            * vs. kprobe remove does not exist because on s390 as we use
 378            * stop_machine to arm/disarm the breakpoints.
 379            */
 380         preempt_enable_no_resched();
 381         return 0;
 382 }
 383 NOKPROBE_SYMBOL(kprobe_handler);
 384
 385 /*
 386  * Function return probe trampoline:
 387  *      - init_kprobes() establishes a probepoint here
 388  *      - When the probed function returns, this probe
 389  *              causes the handlers to fire
 390  */
 391 static void __used kretprobe_trampoline_holder(void)
 392 {
 393         asm volatile(".global kretprobe_trampoline\n"
 394                      "kretprobe_trampoline: bcr 0,0\n");
 395 }
 396
 397 /*
 398  * Called when the probe at kretprobe trampoline is hit
 399  */
 400 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 401 {
 402         struct kretprobe_instance *ri;
 403         struct hlist_head *head, empty_rp;
 404         struct hlist_node *tmp;
 405         unsigned long flags, orig_ret_address;
 406         unsigned long trampoline_address;
 407         kprobe_opcode_t *correct_ret_addr;
 408
 409         INIT_HLIST_HEAD(&empty_rp);
 410         kretprobe_hash_lock(current, &head, &flags);
 411
 412         /*
 413          * It is possible to have multiple instances associated with a given
 414          * task either because an multiple functions in the call path
 415          * have a return probe installed on them, and/or more than one return
 416          * return probe was registered for a target function.
 417          *
 418          * We can handle this because:
 419          *     - instances are always inserted at the head of the list
 420          *     - when multiple return probes are registered for the same
 421          *       function, the first instance's ret_addr will point to the
 422          *       real return address, and all the rest will point to
 423          *       kretprobe_trampoline
 424          */
 425         ri = NULL;
 426         orig_ret_address = 0;
 427         correct_ret_addr = NULL;
 428         trampoline_address = (unsigned long) &kretprobe_trampoline;
 429         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 430                 if (ri->task != current)
 431                         /* another task is sharing our hash bucket */
 432                         continue;
 433
 434                 orig_ret_address = (unsigned long) ri->ret_addr;
 435
 436                 if (orig_ret_address != trampoline_address)
 437                         /*
 438                          * This is the real return address. Any other
 439                          * instances associated with this task are for
 440                          * other calls deeper on the call stack
 441                          */
 442                         break;
 443         }
 444
 445         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 446
 447         correct_ret_addr = ri->ret_addr;
 448         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 449                 if (ri->task != current)
 450                         /* another task is sharing our hash bucket */
 451                         continue;
 452
 453                 orig_ret_address = (unsigned long) ri->ret_addr;
 454
 455                 if (ri->rp && ri->rp->handler) {
 456                         ri->ret_addr = correct_ret_addr;
 457                         ri->rp->handler(ri, regs);
 458                 }
 459
 460                 recycle_rp_inst(ri, &empty_rp);
 461
 462                 if (orig_ret_address != trampoline_address)
 463                         /*
 464                          * This is the real return address. Any other
 465                          * instances associated with this task are for
 466                          * other calls deeper on the call stack
 467                          */
 468                         break;
 469         }
 470
 471         regs->psw.addr = orig_ret_address;
 472
 473         pop_kprobe(get_kprobe_ctlblk());
 474         kretprobe_hash_unlock(current, &flags);
 475         preempt_enable_no_resched();
 476
 477         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 478                 hlist_del(&ri->hlist);
 479                 kfree(ri);
 480         }
 481         /*
 482          * By returning a non-zero value, we are telling
 483          * kprobe_handler() that we don't want the post_handler
 484          * to run (and have re-enabled preemption)
 485          */
 486         return 1;
 487 }
 488 NOKPROBE_SYMBOL(trampoline_probe_handler);
 489
 490 /*
 491  * Called after single-stepping.  p->addr is the address of the
 492  * instruction whose first byte has been replaced by the "breakpoint"
 493  * instruction.  To avoid the SMP problems that can occur when we
 494  * temporarily put back the original opcode to single-step, we
 495  * single-stepped a copy of the instruction.  The address of this
 496  * copy is p->ainsn.insn.
 497  */
 498 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 499 {
 500         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 501         unsigned long ip = regs->psw.addr;
 502         int fixup = probe_get_fixup_type(p->ainsn.insn);
 503
 504         /* Check if the kprobes location is an enabled ftrace caller */
 505         if (p->ainsn.is_ftrace_insn) {
 506                 struct ftrace_insn *insn = (struct ftrace_insn *) p->addr;
 507                 struct ftrace_insn call_insn;
 508
 509                 ftrace_generate_call_insn(&call_insn, (unsigned long) p->addr);
 510                 /*
 511                  * A kprobe on an enabled ftrace call site actually single
 512                  * stepped an unconditional branch (ftrace nop equivalent).
 513                  * Now we need to fixup things and pretend that a brasl r0,...
 514                  * was executed instead.
 515                  */
 516                 if (insn->disp == KPROBE_ON_FTRACE_CALL) {
 517                         ip += call_insn.disp * 2 - MCOUNT_INSN_SIZE;
 518                         regs->gprs[0] = (unsigned long)p->addr + sizeof(*insn);
 519                 }
 520         }
 521
 522         if (fixup & FIXUP_PSW_NORMAL)
 523                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 524
 525         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 526                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 527                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 528                         ip = (unsigned long) p->addr + ilen;
 529         }
 530
 531         if (fixup & FIXUP_RETURN_REGISTER) {
 532                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 533                 regs->gprs[reg] += (unsigned long) p->addr -
 534                                    (unsigned long) p->ainsn.insn;
 535         }
 536
 537         disable_singlestep(kcb, regs, ip);
 538 }
 539 NOKPROBE_SYMBOL(resume_execution);
 540
 541 static int post_kprobe_handler(struct pt_regs *regs)
 542 {
 543         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 544         struct kprobe *p = kprobe_running();
 545
 546         if (!p)
 547                 return 0;
 548
 549         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 550                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 551                 p->post_handler(p, regs, 0);
 552         }
 553
 554         resume_execution(p, regs);
 555         pop_kprobe(kcb);
 556         preempt_enable_no_resched();
 557
 558         /*
 559          * if somebody else is singlestepping across a probe point, psw mask
 560          * will have PER set, in which case, continue the remaining processing
 561          * of do_single_step, as if this is not a probe hit.
 562          */
 563         if (regs->psw.mask & PSW_MASK_PER)
 564                 return 0;
 565
 566         return 1;
 567 }
 568 NOKPROBE_SYMBOL(post_kprobe_handler);
 569
 570 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 571 {
 572         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 573         struct kprobe *p = kprobe_running();
 574         const struct exception_table_entry *entry;
 575
 576         switch(kcb->kprobe_status) {
 577         case KPROBE_SWAP_INST:
 578                 /* We are here because the instruction replacement failed */
 579                 return 0;
 580         case KPROBE_HIT_SS:
 581         case KPROBE_REENTER:
 582                 /*
 583                  * We are here because the instruction being single
 584                  * stepped caused a page fault. We reset the current
 585                  * kprobe and the nip points back to the probe address
 586                  * and allow the page fault handler to continue as a
 587                  * normal page fault.
 588                  */
 589                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 590                 pop_kprobe(kcb);
 591                 preempt_enable_no_resched();
 592                 break;
 593         case KPROBE_HIT_ACTIVE:
 594         case KPROBE_HIT_SSDONE:
 595                 /*
 596                  * We increment the nmissed count for accounting,
 597                  * we can also use npre/npostfault count for accounting
 598                  * these specific fault cases.
 599                  */
 600                 kprobes_inc_nmissed_count(p);
 601
 602                 /*
 603                  * We come here because instructions in the pre/post
 604                  * handler caused the page_fault, this could happen
 605                  * if handler tries to access user space by
 606                  * copy_from_user(), get_user() etc. Let the
 607                  * user-specified handler try to fix it first.
 608                  */
 609                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 610                         return 1;
 611
 612                 /*
 613                  * In case the user-specified fault handler returned
 614                  * zero, try to fix up.
 615                  */
 616                 entry = search_exception_tables(regs->psw.addr);
 617                 if (entry) {
 618                         regs->psw.addr = extable_fixup(entry);
 619                         return 1;
 620                 }
 621
 622                 /*
 623                  * fixup_exception() could not handle it,
 624                  * Let do_page_fault() fix it.
 625                  */
 626                 break;
 627         default:
 628                 break;
 629         }
 630         return 0;
 631 }
 632 NOKPROBE_SYMBOL(kprobe_trap_handler);
 633
 634 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 635 {
 636         int ret;
 637
 638         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 639                 local_irq_disable();
 640         ret = kprobe_trap_handler(regs, trapnr);
 641         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 642                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 643         return ret;
 644 }
 645 NOKPROBE_SYMBOL(kprobe_fault_handler);
 646
 647 /*
 648  * Wrapper routine to for handling exceptions.
 649  */
 650 int kprobe_exceptions_notify(struct notifier_block *self,
 651                              unsigned long val, void *data)
 652 {
 653         struct die_args *args = (struct die_args *) data;
 654         struct pt_regs *regs = args->regs;
 655         int ret = NOTIFY_DONE;
 656
 657         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 658                 local_irq_disable();
 659
 660         switch (val) {
 661         case DIE_BPT:
 662                 if (kprobe_handler(regs))
 663                         ret = NOTIFY_STOP;
 664                 break;
 665         case DIE_SSTEP:
 666                 if (post_kprobe_handler(regs))
 667                         ret = NOTIFY_STOP;
 668                 break;
 669         case DIE_TRAP:
 670                 if (!preemptible() && kprobe_running() &&
 671                     kprobe_trap_handler(regs, args->trapnr))
 672                         ret = NOTIFY_STOP;
 673                 break;
 674         default:
 675                 break;
 676         }
 677
 678         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 679                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 680
 681         return ret;
 682 }
 683 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 684
 685 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 686 {
 687         struct jprobe *jp = container_of(p, struct jprobe, kp);
 688         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 689         unsigned long stack;
 690
 691         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 692
 693         /* setup return addr to the jprobe handler routine */
 694         regs->psw.addr = (unsigned long) jp->entry;
 695         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 696
 697         /* r15 is the stack pointer */
 698         stack = (unsigned long) regs->gprs[15];
 699
 700         memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 701
 702         /*
 703          * jprobes use jprobe_return() which skips the normal return
 704          * path of the function, and this messes up the accounting of the
 705          * function graph tracer to get messed up.
 706          *
 707          * Pause function graph tracing while performing the jprobe function.
 708          */
 709         pause_graph_tracing();
 710         return 1;
 711 }
 712 NOKPROBE_SYMBOL(setjmp_pre_handler);
 713
 714 void jprobe_return(void)
 715 {
 716         asm volatile(".word 0x0002");
 717 }
 718 NOKPROBE_SYMBOL(jprobe_return);
 719
 720 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 721 {
 722         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 723         unsigned long stack;
 724
 725         /* It's OK to start function graph tracing again */
 726         unpause_graph_tracing();
 727
 728         stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 729
 730         /* Put the regs back */
 731         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 732         /* put the stack back */
 733         memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 734         preempt_enable_no_resched();
 735         return 1;
 736 }
 737 NOKPROBE_SYMBOL(longjmp_break_handler);
 738
 739 static struct kprobe trampoline = {
 740         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 741         .pre_handler = trampoline_probe_handler
 742 };
 743
 744 int __init arch_init_kprobes(void)
 745 {
 746         return register_kprobe(&trampoline);
 747 }
 748
 749 int arch_trampoline_kprobe(struct kprobe *p)
 750 {
 751         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 752 }
 753 NOKPROBE_SYMBOL(arch_trampoline_kprobe);