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