arch/tile/kernel/kprobes.c

   1 /*
   2  * arch/tile/kernel/kprobes.c
   3  * Kprobes on TILE-Gx
   4  *
   5  * Some portions copied from the MIPS version.
   6  *
   7  * Copyright (C) IBM Corporation, 2002, 2004
   8  * Copyright 2006 Sony Corp.
   9  * Copyright 2010 Cavium Networks
  10  *
  11  * Copyright 2012 Tilera Corporation. All Rights Reserved.
  12  *
  13  *   This program is free software; you can redistribute it and/or
  14  *   modify it under the terms of the GNU General Public License
  15  *   as published by the Free Software Foundation, version 2.
  16  *
  17  *   This program is distributed in the hope that it will be useful, but
  18  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  19  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  20  *   NON INFRINGEMENT.  See the GNU General Public License for
  21  *   more details.
  22  */
  23
  24 #include <linux/kprobes.h>
  25 #include <linux/kdebug.h>
  26 #include <linux/module.h>
  27 #include <linux/slab.h>
  28 #include <linux/uaccess.h>
  29 #include <asm/cacheflush.h>
  30
  31 #include <arch/opcode.h>
  32
  33 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  34 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  35
  36 tile_bundle_bits breakpoint_insn = TILEGX_BPT_BUNDLE;
  37 tile_bundle_bits breakpoint2_insn = TILEGX_BPT_BUNDLE | DIE_SSTEPBP;
  38
  39 /*
  40  * Check whether instruction is branch or jump, or if executing it
  41  * has different results depending on where it is executed (e.g. lnk).
  42  */
  43 static int __kprobes insn_has_control(kprobe_opcode_t insn)
  44 {
  45         if (get_Mode(insn) != 0) {   /* Y-format bundle */
  46                 if (get_Opcode_Y1(insn) != RRR_1_OPCODE_Y1 ||
  47                     get_RRROpcodeExtension_Y1(insn) != UNARY_RRR_1_OPCODE_Y1)
  48                         return 0;
  49
  50                 switch (get_UnaryOpcodeExtension_Y1(insn)) {
  51                 case JALRP_UNARY_OPCODE_Y1:
  52                 case JALR_UNARY_OPCODE_Y1:
  53                 case JRP_UNARY_OPCODE_Y1:
  54                 case JR_UNARY_OPCODE_Y1:
  55                 case LNK_UNARY_OPCODE_Y1:
  56                         return 1;
  57                 default:
  58                         return 0;
  59                 }
  60         }
  61
  62         switch (get_Opcode_X1(insn)) {
  63         case BRANCH_OPCODE_X1:  /* branch instructions */
  64         case JUMP_OPCODE_X1:    /* jump instructions: j and jal */
  65                 return 1;
  66
  67         case RRR_0_OPCODE_X1:   /* other jump instructions */
  68                 if (get_RRROpcodeExtension_X1(insn) != UNARY_RRR_0_OPCODE_X1)
  69                         return 0;
  70                 switch (get_UnaryOpcodeExtension_X1(insn)) {
  71                 case JALRP_UNARY_OPCODE_X1:
  72                 case JALR_UNARY_OPCODE_X1:
  73                 case JRP_UNARY_OPCODE_X1:
  74                 case JR_UNARY_OPCODE_X1:
  75                 case LNK_UNARY_OPCODE_X1:
  76                         return 1;
  77                 default:
  78                         return 0;
  79                 }
  80         default:
  81                 return 0;
  82         }
  83 }
  84
  85 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  86 {
  87         unsigned long addr = (unsigned long)p->addr;
  88
  89         if (addr & (sizeof(kprobe_opcode_t) - 1))
  90                 return -EINVAL;
  91
  92         if (insn_has_control(*p->addr)) {
  93                 pr_notice("Kprobes for control instructions are not supported\n");
  94                 return -EINVAL;
  95         }
  96
  97         /* insn: must be on special executable page on tile. */
  98         p->ainsn.insn = get_insn_slot();
  99         if (!p->ainsn.insn)
 100                 return -ENOMEM;
 101
 102         /*
 103          * In the kprobe->ainsn.insn[] array we store the original
 104          * instruction at index zero and a break trap instruction at
 105          * index one.
 106          */
 107         memcpy(&p->ainsn.insn[0], p->addr, sizeof(kprobe_opcode_t));
 108         p->ainsn.insn[1] = breakpoint2_insn;
 109         p->opcode = *p->addr;
 110
 111         return 0;
 112 }
 113
 114 void __kprobes arch_arm_kprobe(struct kprobe *p)
 115 {
 116         unsigned long addr_wr;
 117
 118         /* Operate on writable kernel text mapping. */
 119         addr_wr = (unsigned long)p->addr - MEM_SV_START + PAGE_OFFSET;
 120
 121         if (probe_kernel_write((void *)addr_wr, &breakpoint_insn,
 122                 sizeof(breakpoint_insn)))
 123                 pr_err("%s: failed to enable kprobe\n", __func__);
 124
 125         smp_wmb();
 126         flush_insn_slot(p);
 127 }
 128
 129 void __kprobes arch_disarm_kprobe(struct kprobe *kp)
 130 {
 131         unsigned long addr_wr;
 132
 133         /* Operate on writable kernel text mapping. */
 134         addr_wr = (unsigned long)kp->addr - MEM_SV_START + PAGE_OFFSET;
 135
 136         if (probe_kernel_write((void *)addr_wr, &kp->opcode,
 137                 sizeof(kp->opcode)))
 138                 pr_err("%s: failed to enable kprobe\n", __func__);
 139
 140         smp_wmb();
 141         flush_insn_slot(kp);
 142 }
 143
 144 void __kprobes arch_remove_kprobe(struct kprobe *p)
 145 {
 146         if (p->ainsn.insn) {
 147                 free_insn_slot(p->ainsn.insn, 0);
 148                 p->ainsn.insn = NULL;
 149         }
 150 }
 151
 152 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 153 {
 154         kcb->prev_kprobe.kp = kprobe_running();
 155         kcb->prev_kprobe.status = kcb->kprobe_status;
 156         kcb->prev_kprobe.saved_pc = kcb->kprobe_saved_pc;
 157 }
 158
 159 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 160 {
 161         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 162         kcb->kprobe_status = kcb->prev_kprobe.status;
 163         kcb->kprobe_saved_pc = kcb->prev_kprobe.saved_pc;
 164 }
 165
 166 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 167                         struct kprobe_ctlblk *kcb)
 168 {
 169         __this_cpu_write(current_kprobe, p);
 170         kcb->kprobe_saved_pc = regs->pc;
 171 }
 172
 173 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 174 {
 175         /* Single step inline if the instruction is a break. */
 176         if (p->opcode == breakpoint_insn ||
 177             p->opcode == breakpoint2_insn)
 178                 regs->pc = (unsigned long)p->addr;
 179         else
 180                 regs->pc = (unsigned long)&p->ainsn.insn[0];
 181 }
 182
 183 static int __kprobes kprobe_handler(struct pt_regs *regs)
 184 {
 185         struct kprobe *p;
 186         int ret = 0;
 187         kprobe_opcode_t *addr;
 188         struct kprobe_ctlblk *kcb;
 189
 190         addr = (kprobe_opcode_t *)regs->pc;
 191
 192         /*
 193          * We don't want to be preempted for the entire
 194          * duration of kprobe processing.
 195          */
 196         preempt_disable();
 197         kcb = get_kprobe_ctlblk();
 198
 199         /* Check we're not actually recursing. */
 200         if (kprobe_running()) {
 201                 p = get_kprobe(addr);
 202                 if (p) {
 203                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 204                             p->ainsn.insn[0] == breakpoint_insn) {
 205                                 goto no_kprobe;
 206                         }
 207                         /*
 208                          * We have reentered the kprobe_handler(), since
 209                          * another probe was hit while within the handler.
 210                          * We here save the original kprobes variables and
 211                          * just single step on the instruction of the new probe
 212                          * without calling any user handlers.
 213                          */
 214                         save_previous_kprobe(kcb);
 215                         set_current_kprobe(p, regs, kcb);
 216                         kprobes_inc_nmissed_count(p);
 217                         prepare_singlestep(p, regs);
 218                         kcb->kprobe_status = KPROBE_REENTER;
 219                         return 1;
 220                 } else {
 221                         if (*addr != breakpoint_insn) {
 222                                 /*
 223                                  * The breakpoint instruction was removed by
 224                                  * another cpu right after we hit, no further
 225                                  * handling of this interrupt is appropriate.
 226                                  */
 227                                 ret = 1;
 228                                 goto no_kprobe;
 229                         }
 230                         p = __this_cpu_read(current_kprobe);
 231                         if (p->break_handler && p->break_handler(p, regs))
 232                                 goto ss_probe;
 233                 }
 234                 goto no_kprobe;
 235         }
 236
 237         p = get_kprobe(addr);
 238         if (!p) {
 239                 if (*addr != breakpoint_insn) {
 240                         /*
 241                          * The breakpoint instruction was removed right
 242                          * after we hit it.  Another cpu has removed
 243                          * either a probepoint or a debugger breakpoint
 244                          * at this address.  In either case, no further
 245                          * handling of this interrupt is appropriate.
 246                          */
 247                         ret = 1;
 248                 }
 249                 /* Not one of ours: let kernel handle it. */
 250                 goto no_kprobe;
 251         }
 252
 253         set_current_kprobe(p, regs, kcb);
 254         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 255
 256         if (p->pre_handler && p->pre_handler(p, regs)) {
 257                 /* Handler has already set things up, so skip ss setup. */
 258                 return 1;
 259         }
 260
 261 ss_probe:
 262         prepare_singlestep(p, regs);
 263         kcb->kprobe_status = KPROBE_HIT_SS;
 264         return 1;
 265
 266 no_kprobe:
 267         preempt_enable_no_resched();
 268         return ret;
 269 }
 270
 271 /*
 272  * Called after single-stepping.  p->addr is the address of the
 273  * instruction that has been replaced by the breakpoint. To avoid the
 274  * SMP problems that can occur when we temporarily put back the
 275  * original opcode to single-step, we single-stepped a copy of the
 276  * instruction.  The address of this copy is p->ainsn.insn.
 277  *
 278  * This function prepares to return from the post-single-step
 279  * breakpoint trap.
 280  */
 281 static void __kprobes resume_execution(struct kprobe *p,
 282                                        struct pt_regs *regs,
 283                                        struct kprobe_ctlblk *kcb)
 284 {
 285         unsigned long orig_pc = kcb->kprobe_saved_pc;
 286         regs->pc = orig_pc + 8;
 287 }
 288
 289 static inline int post_kprobe_handler(struct pt_regs *regs)
 290 {
 291         struct kprobe *cur = kprobe_running();
 292         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 293
 294         if (!cur)
 295                 return 0;
 296
 297         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 298                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 299                 cur->post_handler(cur, regs, 0);
 300         }
 301
 302         resume_execution(cur, regs, kcb);
 303
 304         /* Restore back the original saved kprobes variables and continue. */
 305         if (kcb->kprobe_status == KPROBE_REENTER) {
 306                 restore_previous_kprobe(kcb);
 307                 goto out;
 308         }
 309         reset_current_kprobe();
 310 out:
 311         preempt_enable_no_resched();
 312
 313         return 1;
 314 }
 315
 316 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 317 {
 318         struct kprobe *cur = kprobe_running();
 319         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 320
 321         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 322                 return 1;
 323
 324         if (kcb->kprobe_status & KPROBE_HIT_SS) {
 325                 /*
 326                  * We are here because the instruction being single
 327                  * stepped caused a page fault. We reset the current
 328                  * kprobe and the ip points back to the probe address
 329                  * and allow the page fault handler to continue as a
 330                  * normal page fault.
 331                  */
 332                 resume_execution(cur, regs, kcb);
 333                 reset_current_kprobe();
 334                 preempt_enable_no_resched();
 335         }
 336         return 0;
 337 }
 338
 339 /*
 340  * Wrapper routine for handling exceptions.
 341  */
 342 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 343                                        unsigned long val, void *data)
 344 {
 345         struct die_args *args = (struct die_args *)data;
 346         int ret = NOTIFY_DONE;
 347
 348         switch (val) {
 349         case DIE_BREAK:
 350                 if (kprobe_handler(args->regs))
 351                         ret = NOTIFY_STOP;
 352                 break;
 353         case DIE_SSTEPBP:
 354                 if (post_kprobe_handler(args->regs))
 355                         ret = NOTIFY_STOP;
 356                 break;
 357         case DIE_PAGE_FAULT:
 358                 /* kprobe_running() needs smp_processor_id(). */
 359                 preempt_disable();
 360
 361                 if (kprobe_running()
 362                     && kprobe_fault_handler(args->regs, args->trapnr))
 363                         ret = NOTIFY_STOP;
 364                 preempt_enable();
 365                 break;
 366         default:
 367                 break;
 368         }
 369         return ret;
 370 }
 371
 372 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 373 {
 374         struct jprobe *jp = container_of(p, struct jprobe, kp);
 375         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 376
 377         kcb->jprobe_saved_regs = *regs;
 378         kcb->jprobe_saved_sp = regs->sp;
 379
 380         memcpy(kcb->jprobes_stack, (void *)kcb->jprobe_saved_sp,
 381                MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
 382
 383         regs->pc = (unsigned long)(jp->entry);
 384
 385         return 1;
 386 }
 387
 388 /* Defined in the inline asm below. */
 389 void jprobe_return_end(void);
 390
 391 void __kprobes jprobe_return(void)
 392 {
 393         asm volatile(
 394                 "bpt\n\t"
 395                 ".globl jprobe_return_end\n"
 396                 "jprobe_return_end:\n");
 397 }
 398
 399 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 400 {
 401         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 402
 403         if (regs->pc >= (unsigned long)jprobe_return &&
 404             regs->pc <= (unsigned long)jprobe_return_end) {
 405                 *regs = kcb->jprobe_saved_regs;
 406                 memcpy((void *)kcb->jprobe_saved_sp, kcb->jprobes_stack,
 407                        MIN_JPROBES_STACK_SIZE(kcb->jprobe_saved_sp));
 408                 preempt_enable_no_resched();
 409
 410                 return 1;
 411         }
 412         return 0;
 413 }
 414
 415 /*
 416  * Function return probe trampoline:
 417  * - init_kprobes() establishes a probepoint here
 418  * - When the probed function returns, this probe causes the
 419  *   handlers to fire
 420  */
 421 static void __used kretprobe_trampoline_holder(void)
 422 {
 423         asm volatile(
 424                 "nop\n\t"
 425                 ".global kretprobe_trampoline\n"
 426                 "kretprobe_trampoline:\n\t"
 427                 "nop\n\t"
 428                 : : : "memory");
 429 }
 430
 431 void kretprobe_trampoline(void);
 432
 433 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 434                                       struct pt_regs *regs)
 435 {
 436         ri->ret_addr = (kprobe_opcode_t *) regs->lr;
 437
 438         /* Replace the return addr with trampoline addr */
 439         regs->lr = (unsigned long)kretprobe_trampoline;
 440 }
 441
 442 /*
 443  * Called when the probe at kretprobe trampoline is hit.
 444  */
 445 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 446                                                 struct pt_regs *regs)
 447 {
 448         struct kretprobe_instance *ri = NULL;
 449         struct hlist_head *head, empty_rp;
 450         struct hlist_node *tmp;
 451         unsigned long flags, orig_ret_address = 0;
 452         unsigned long trampoline_address = (unsigned long)kretprobe_trampoline;
 453
 454         INIT_HLIST_HEAD(&empty_rp);
 455         kretprobe_hash_lock(current, &head, &flags);
 456
 457         /*
 458          * It is possible to have multiple instances associated with a given
 459          * task either because multiple functions in the call path have
 460          * a return probe installed on them, and/or more than one return
 461          * return probe was registered for a target function.
 462          *
 463          * We can handle this because:
 464          *     - instances are always inserted at the head of the list
 465          *     - when multiple return probes are registered for the same
 466          *       function, the first instance's ret_addr will point to the
 467          *       real return address, and all the rest will point to
 468          *       kretprobe_trampoline
 469          */
 470         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 471                 if (ri->task != current)
 472                         /* another task is sharing our hash bucket */
 473                         continue;
 474
 475                 if (ri->rp && ri->rp->handler)
 476                         ri->rp->handler(ri, regs);
 477
 478                 orig_ret_address = (unsigned long)ri->ret_addr;
 479                 recycle_rp_inst(ri, &empty_rp);
 480
 481                 if (orig_ret_address != trampoline_address) {
 482                         /*
 483                          * This is the real return address. Any other
 484                          * instances associated with this task are for
 485                          * other calls deeper on the call stack
 486                          */
 487                         break;
 488                 }
 489         }
 490
 491         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 492         instruction_pointer(regs) = orig_ret_address;
 493
 494         reset_current_kprobe();
 495         kretprobe_hash_unlock(current, &flags);
 496         preempt_enable_no_resched();
 497
 498         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 499                 hlist_del(&ri->hlist);
 500                 kfree(ri);
 501         }
 502         /*
 503          * By returning a non-zero value, we are telling
 504          * kprobe_handler() that we don't want the post_handler
 505          * to run (and have re-enabled preemption)
 506          */
 507         return 1;
 508 }
 509
 510 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 511 {
 512         if (p->addr == (kprobe_opcode_t *)kretprobe_trampoline)
 513                 return 1;
 514
 515         return 0;
 516 }
 517
 518 static struct kprobe trampoline_p = {
 519         .addr = (kprobe_opcode_t *)kretprobe_trampoline,
 520         .pre_handler = trampoline_probe_handler
 521 };
 522
 523 int __init arch_init_kprobes(void)
 524 {
 525         register_kprobe(&trampoline_p);
 526         return 0;
 527 }