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   1 /* arch/sparc64/kernel/kprobes.c
   2  *
   3  * Copyright (C) 2004 David S. Miller <davem@davemloft.net>
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/kprobes.h>
   8 #include <linux/module.h>
   9 #include <asm/kdebug.h>
  10 #include <asm/signal.h>
  11 #include <asm/cacheflush.h>
  12 #include <asm/uaccess.h>
  13
  14 /* We do not have hardware single-stepping on sparc64.
  15  * So we implement software single-stepping with breakpoint
  16  * traps.  The top-level scheme is similar to that used
  17  * in the x86 kprobes implementation.
  18  *
  19  * In the kprobe->ainsn.insn[] array we store the original
  20  * instruction at index zero and a break instruction at
  21  * index one.
  22  *
  23  * When we hit a kprobe we:
  24  * - Run the pre-handler
  25  * - Remember "regs->tnpc" and interrupt level stored in
  26  *   "regs->tstate" so we can restore them later
  27  * - Disable PIL interrupts
  28  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  29  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  30  * - Mark that we are actively in a kprobe
  31  *
  32  * At this point we wait for the second breakpoint at
  33  * kprobe->ainsn.insn[1] to hit.  When it does we:
  34  * - Run the post-handler
  35  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  36  *   restore the PIL interrupt level in "regs->tstate" as well
  37  * - Make any adjustments necessary to regs->tnpc in order
  38  *   to handle relative branches correctly.  See below.
  39  * - Mark that we are no longer actively in a kprobe.
  40  */
  41
  42 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  43 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  44
  45 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  46 {
  47         p->ainsn.insn[0] = *p->addr;
  48         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  49         p->opcode = *p->addr;
  50         return 0;
  51 }
  52
  53 void __kprobes arch_arm_kprobe(struct kprobe *p)
  54 {
  55         *p->addr = BREAKPOINT_INSTRUCTION;
  56         flushi(p->addr);
  57 }
  58
  59 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  60 {
  61         *p->addr = p->opcode;
  62         flushi(p->addr);
  63 }
  64
  65 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  66 {
  67         kcb->prev_kprobe.kp = kprobe_running();
  68         kcb->prev_kprobe.status = kcb->kprobe_status;
  69         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  70         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  71 }
  72
  73 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  74 {
  75         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  76         kcb->kprobe_status = kcb->prev_kprobe.status;
  77         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  78         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  79 }
  80
  81 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  82                                 struct kprobe_ctlblk *kcb)
  83 {
  84         __get_cpu_var(current_kprobe) = p;
  85         kcb->kprobe_orig_tnpc = regs->tnpc;
  86         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  87 }
  88
  89 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  90                         struct kprobe_ctlblk *kcb)
  91 {
  92         regs->tstate |= TSTATE_PIL;
  93
  94         /*single step inline, if it a breakpoint instruction*/
  95         if (p->opcode == BREAKPOINT_INSTRUCTION) {
  96                 regs->tpc = (unsigned long) p->addr;
  97                 regs->tnpc = kcb->kprobe_orig_tnpc;
  98         } else {
  99                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 100                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 101         }
 102 }
 103
 104 static int __kprobes kprobe_handler(struct pt_regs *regs)
 105 {
 106         struct kprobe *p;
 107         void *addr = (void *) regs->tpc;
 108         int ret = 0;
 109         struct kprobe_ctlblk *kcb;
 110
 111         /*
 112          * We don't want to be preempted for the entire
 113          * duration of kprobe processing
 114          */
 115         preempt_disable();
 116         kcb = get_kprobe_ctlblk();
 117
 118         if (kprobe_running()) {
 119                 p = get_kprobe(addr);
 120                 if (p) {
 121                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 122                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 123                                         kcb->kprobe_orig_tstate_pil);
 124                                 goto no_kprobe;
 125                         }
 126                         /* We have reentered the kprobe_handler(), since
 127                          * another probe was hit while within the handler.
 128                          * We here save the original kprobes variables and
 129                          * just single step on the instruction of the new probe
 130                          * without calling any user handlers.
 131                          */
 132                         save_previous_kprobe(kcb);
 133                         set_current_kprobe(p, regs, kcb);
 134                         kprobes_inc_nmissed_count(p);
 135                         kcb->kprobe_status = KPROBE_REENTER;
 136                         prepare_singlestep(p, regs, kcb);
 137                         return 1;
 138                 } else {
 139                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 140                         /* The breakpoint instruction was removed by
 141                          * another cpu right after we hit, no further
 142                          * handling of this interrupt is appropriate
 143                          */
 144                                 ret = 1;
 145                                 goto no_kprobe;
 146                         }
 147                         p = __get_cpu_var(current_kprobe);
 148                         if (p->break_handler && p->break_handler(p, regs))
 149                                 goto ss_probe;
 150                 }
 151                 goto no_kprobe;
 152         }
 153
 154         p = get_kprobe(addr);
 155         if (!p) {
 156                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 157                         /*
 158                          * The breakpoint instruction was removed right
 159                          * after we hit it.  Another cpu has removed
 160                          * either a probepoint or a debugger breakpoint
 161                          * at this address.  In either case, no further
 162                          * handling of this interrupt is appropriate.
 163                          */
 164                         ret = 1;
 165                 }
 166                 /* Not one of ours: let kernel handle it */
 167                 goto no_kprobe;
 168         }
 169
 170         set_current_kprobe(p, regs, kcb);
 171         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 172         if (p->pre_handler && p->pre_handler(p, regs))
 173                 return 1;
 174
 175 ss_probe:
 176         prepare_singlestep(p, regs, kcb);
 177         kcb->kprobe_status = KPROBE_HIT_SS;
 178         return 1;
 179
 180 no_kprobe:
 181         preempt_enable_no_resched();
 182         return ret;
 183 }
 184
 185 /* If INSN is a relative control transfer instruction,
 186  * return the corrected branch destination value.
 187  *
 188  * The original INSN location was REAL_PC, it actually
 189  * executed at PC and produced destination address NPC.
 190  */
 191 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 192                                                unsigned long pc,
 193                                                unsigned long npc)
 194 {
 195         /* Branch not taken, no mods necessary.  */
 196         if (npc == pc + 0x4UL)
 197                 return real_pc + 0x4UL;
 198
 199         /* The three cases are call, branch w/prediction,
 200          * and traditional branch.
 201          */
 202         if ((insn & 0xc0000000) == 0x40000000 ||
 203             (insn & 0xc1c00000) == 0x00400000 ||
 204             (insn & 0xc1c00000) == 0x00800000) {
 205                 /* The instruction did all the work for us
 206                  * already, just apply the offset to the correct
 207                  * instruction location.
 208                  */
 209                 return (real_pc + (npc - pc));
 210         }
 211
 212         return real_pc + 0x4UL;
 213 }
 214
 215 /* If INSN is an instruction which writes it's PC location
 216  * into a destination register, fix that up.
 217  */
 218 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 219                                   unsigned long real_pc)
 220 {
 221         unsigned long *slot = NULL;
 222
 223         /* Simplest cast is call, which always uses %o7 */
 224         if ((insn & 0xc0000000) == 0x40000000) {
 225                 slot = &regs->u_regs[UREG_I7];
 226         }
 227
 228         /* Jmpl encodes the register inside of the opcode */
 229         if ((insn & 0xc1f80000) == 0x81c00000) {
 230                 unsigned long rd = ((insn >> 25) & 0x1f);
 231
 232                 if (rd <= 15) {
 233                         slot = &regs->u_regs[rd];
 234                 } else {
 235                         /* Hard case, it goes onto the stack. */
 236                         flushw_all();
 237
 238                         rd -= 16;
 239                         slot = (unsigned long *)
 240                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 241                         slot += rd;
 242                 }
 243         }
 244         if (slot != NULL)
 245                 *slot = real_pc;
 246 }
 247
 248 /*
 249  * Called after single-stepping.  p->addr is the address of the
 250  * instruction whose first byte has been replaced by the breakpoint
 251  * instruction.  To avoid the SMP problems that can occur when we
 252  * temporarily put back the original opcode to single-step, we
 253  * single-stepped a copy of the instruction.  The address of this
 254  * copy is p->ainsn.insn.
 255  *
 256  * This function prepares to return from the post-single-step
 257  * breakpoint trap.
 258  */
 259 static void __kprobes resume_execution(struct kprobe *p,
 260                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 261 {
 262         u32 insn = p->ainsn.insn[0];
 263
 264         regs->tpc = kcb->kprobe_orig_tnpc;
 265         regs->tnpc = relbranch_fixup(insn,
 266                                      (unsigned long) p->addr,
 267                                      (unsigned long) &p->ainsn.insn[0],
 268                                      regs->tnpc);
 269         retpc_fixup(regs, insn, (unsigned long) p->addr);
 270
 271         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 272                         kcb->kprobe_orig_tstate_pil);
 273 }
 274
 275 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 276 {
 277         struct kprobe *cur = kprobe_running();
 278         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 279
 280         if (!cur)
 281                 return 0;
 282
 283         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 284                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 285                 cur->post_handler(cur, regs, 0);
 286         }
 287
 288         resume_execution(cur, regs, kcb);
 289
 290         /*Restore back the original saved kprobes variables and continue. */
 291         if (kcb->kprobe_status == KPROBE_REENTER) {
 292                 restore_previous_kprobe(kcb);
 293                 goto out;
 294         }
 295         reset_current_kprobe();
 296 out:
 297         preempt_enable_no_resched();
 298
 299         return 1;
 300 }
 301
 302 static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 303 {
 304         struct kprobe *cur = kprobe_running();
 305         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 306         const struct exception_table_entry *entry;
 307
 308         switch(kcb->kprobe_status) {
 309         case KPROBE_HIT_SS:
 310         case KPROBE_REENTER:
 311                 /*
 312                  * We are here because the instruction being single
 313                  * stepped caused a page fault. We reset the current
 314                  * kprobe and the tpc points back to the probe address
 315                  * and allow the page fault handler to continue as a
 316                  * normal page fault.
 317                  */
 318                 regs->tpc = (unsigned long)cur->addr;
 319                 regs->tnpc = kcb->kprobe_orig_tnpc;
 320                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 321                                 kcb->kprobe_orig_tstate_pil);
 322                 if (kcb->kprobe_status == KPROBE_REENTER)
 323                         restore_previous_kprobe(kcb);
 324                 else
 325                         reset_current_kprobe();
 326                 preempt_enable_no_resched();
 327                 break;
 328         case KPROBE_HIT_ACTIVE:
 329         case KPROBE_HIT_SSDONE:
 330                 /*
 331                  * We increment the nmissed count for accounting,
 332                  * we can also use npre/npostfault count for accouting
 333                  * these specific fault cases.
 334                  */
 335                 kprobes_inc_nmissed_count(cur);
 336
 337                 /*
 338                  * We come here because instructions in the pre/post
 339                  * handler caused the page_fault, this could happen
 340                  * if handler tries to access user space by
 341                  * copy_from_user(), get_user() etc. Let the
 342                  * user-specified handler try to fix it first.
 343                  */
 344                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 345                         return 1;
 346
 347                 /*
 348                  * In case the user-specified fault handler returned
 349                  * zero, try to fix up.
 350                  */
 351
 352                 entry = search_exception_tables(regs->tpc);
 353                 if (entry) {
 354                         regs->tpc = entry->fixup;
 355                         regs->tnpc = regs->tpc + 4;
 356                         return 1;
 357                 }
 358
 359                 /*
 360                  * fixup_exception() could not handle it,
 361                  * Let do_page_fault() fix it.
 362                  */
 363                 break;
 364         default:
 365                 break;
 366         }
 367
 368         return 0;
 369 }
 370
 371 /*
 372  * Wrapper routine to for handling exceptions.
 373  */
 374 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 375                                        unsigned long val, void *data)
 376 {
 377         struct die_args *args = (struct die_args *)data;
 378         int ret = NOTIFY_DONE;
 379
 380         if (args->regs && user_mode(args->regs))
 381                 return ret;
 382
 383         switch (val) {
 384         case DIE_DEBUG:
 385                 if (kprobe_handler(args->regs))
 386                         ret = NOTIFY_STOP;
 387                 break;
 388         case DIE_DEBUG_2:
 389                 if (post_kprobe_handler(args->regs))
 390                         ret = NOTIFY_STOP;
 391                 break;
 392         case DIE_GPF:
 393         case DIE_PAGE_FAULT:
 394                 /* kprobe_running() needs smp_processor_id() */
 395                 preempt_disable();
 396                 if (kprobe_running() &&
 397                     kprobe_fault_handler(args->regs, args->trapnr))
 398                         ret = NOTIFY_STOP;
 399                 preempt_enable();
 400                 break;
 401         default:
 402                 break;
 403         }
 404         return ret;
 405 }
 406
 407 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 408                                       struct pt_regs *regs)
 409 {
 410         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 411
 412         if (user_mode(regs)) {
 413                 local_irq_enable();
 414                 bad_trap(regs, trap_level);
 415                 return;
 416         }
 417
 418         /* trap_level == 0x170 --> ta 0x70
 419          * trap_level == 0x171 --> ta 0x71
 420          */
 421         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 422                        (trap_level == 0x170) ? "debug" : "debug_2",
 423                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 424                 bad_trap(regs, trap_level);
 425 }
 426
 427 /* Jprobes support.  */
 428 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 429 {
 430         struct jprobe *jp = container_of(p, struct jprobe, kp);
 431         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 432
 433         kcb->jprobe_saved_regs_location = regs;
 434         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 435
 436         /* Save a whole stack frame, this gets arguments
 437          * pushed onto the stack after using up all the
 438          * arg registers.
 439          */
 440         memcpy(&(kcb->jprobe_saved_stack),
 441                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 442                sizeof(kcb->jprobe_saved_stack));
 443
 444         regs->tpc  = (unsigned long) jp->entry;
 445         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 446         regs->tstate |= TSTATE_PIL;
 447
 448         return 1;
 449 }
 450
 451 void __kprobes jprobe_return(void)
 452 {
 453         __asm__ __volatile__(
 454                 ".globl jprobe_return_trap_instruction\n"
 455 "jprobe_return_trap_instruction:\n\t"
 456                 "ta 0x70");
 457 }
 458
 459 extern void jprobe_return_trap_instruction(void);
 460
 461 extern void __show_regs(struct pt_regs * regs);
 462
 463 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 464 {
 465         u32 *addr = (u32 *) regs->tpc;
 466         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 467
 468         if (addr == (u32 *) jprobe_return_trap_instruction) {
 469                 if (kcb->jprobe_saved_regs_location != regs) {
 470                         printk("JPROBE: Current regs (%p) does not match "
 471                                "saved regs (%p).\n",
 472                                regs, kcb->jprobe_saved_regs_location);
 473                         printk("JPROBE: Saved registers\n");
 474                         __show_regs(kcb->jprobe_saved_regs_location);
 475                         printk("JPROBE: Current registers\n");
 476                         __show_regs(regs);
 477                         BUG();
 478                 }
 479                 /* Restore old register state.  Do pt_regs
 480                  * first so that UREG_FP is the original one for
 481                  * the stack frame restore.
 482                  */
 483                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 484
 485                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 486                        &(kcb->jprobe_saved_stack),
 487                        sizeof(kcb->jprobe_saved_stack));
 488
 489                 preempt_enable_no_resched();
 490                 return 1;
 491         }
 492         return 0;
 493 }
 494
 495 /* architecture specific initialization */
 496 int arch_init_kprobes(void)
 497 {
 498         return 0;
 499 }