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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/config.h>
   7 #include <linux/kernel.h>
   8 #include <linux/kprobes.h>
   9 #include <linux/module.h>
  10 #include <asm/kdebug.h>
  11 #include <asm/signal.h>
  12 #include <asm/cacheflush.h>
  13 #include <asm/uaccess.h>
  14
  15 /* We do not have hardware single-stepping on sparc64.
  16  * So we implement software single-stepping with breakpoint
  17  * traps.  The top-level scheme is similar to that used
  18  * in the x86 kprobes implementation.
  19  *
  20  * In the kprobe->ainsn.insn[] array we store the original
  21  * instruction at index zero and a break instruction at
  22  * index one.
  23  *
  24  * When we hit a kprobe we:
  25  * - Run the pre-handler
  26  * - Remember "regs->tnpc" and interrupt level stored in
  27  *   "regs->tstate" so we can restore them later
  28  * - Disable PIL interrupts
  29  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  30  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  31  * - Mark that we are actively in a kprobe
  32  *
  33  * At this point we wait for the second breakpoint at
  34  * kprobe->ainsn.insn[1] to hit.  When it does we:
  35  * - Run the post-handler
  36  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  37  *   restore the PIL interrupt level in "regs->tstate" as well
  38  * - Make any adjustments necessary to regs->tnpc in order
  39  *   to handle relative branches correctly.  See below.
  40  * - Mark that we are no longer actively in a kprobe.
  41  */
  42
  43 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  44 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  45
  46 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  47 {
  48         p->ainsn.insn[0] = *p->addr;
  49         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  50         p->opcode = *p->addr;
  51         return 0;
  52 }
  53
  54 void __kprobes arch_arm_kprobe(struct kprobe *p)
  55 {
  56         *p->addr = BREAKPOINT_INSTRUCTION;
  57         flushi(p->addr);
  58 }
  59
  60 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  61 {
  62         *p->addr = p->opcode;
  63         flushi(p->addr);
  64 }
  65
  66 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
  67 {
  68         kcb->prev_kprobe.kp = kprobe_running();
  69         kcb->prev_kprobe.status = kcb->kprobe_status;
  70         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  71         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  72 }
  73
  74 static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  75 {
  76         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  77         kcb->kprobe_status = kcb->prev_kprobe.status;
  78         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  79         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  80 }
  81
  82 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  83                                 struct kprobe_ctlblk *kcb)
  84 {
  85         __get_cpu_var(current_kprobe) = p;
  86         kcb->kprobe_orig_tnpc = regs->tnpc;
  87         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  88 }
  89
  90 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  91                         struct kprobe_ctlblk *kcb)
  92 {
  93         regs->tstate |= TSTATE_PIL;
  94
  95         /*single step inline, if it a breakpoint instruction*/
  96         if (p->opcode == BREAKPOINT_INSTRUCTION) {
  97                 regs->tpc = (unsigned long) p->addr;
  98                 regs->tnpc = kcb->kprobe_orig_tnpc;
  99         } else {
 100                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 101                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 102         }
 103 }
 104
 105 static int __kprobes kprobe_handler(struct pt_regs *regs)
 106 {
 107         struct kprobe *p;
 108         void *addr = (void *) regs->tpc;
 109         int ret = 0;
 110         struct kprobe_ctlblk *kcb;
 111
 112         /*
 113          * We don't want to be preempted for the entire
 114          * duration of kprobe processing
 115          */
 116         preempt_disable();
 117         kcb = get_kprobe_ctlblk();
 118
 119         if (kprobe_running()) {
 120                 p = get_kprobe(addr);
 121                 if (p) {
 122                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 123                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 124                                         kcb->kprobe_orig_tstate_pil);
 125                                 goto no_kprobe;
 126                         }
 127                         /* We have reentered the kprobe_handler(), since
 128                          * another probe was hit while within the handler.
 129                          * We here save the original kprobes variables and
 130                          * just single step on the instruction of the new probe
 131                          * without calling any user handlers.
 132                          */
 133                         save_previous_kprobe(kcb);
 134                         set_current_kprobe(p, regs, kcb);
 135                         kprobes_inc_nmissed_count(p);
 136                         kcb->kprobe_status = KPROBE_REENTER;
 137                         prepare_singlestep(p, regs, kcb);
 138                         return 1;
 139                 } else {
 140                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 141                         /* The breakpoint instruction was removed by
 142                          * another cpu right after we hit, no further
 143                          * handling of this interrupt is appropriate
 144                          */
 145                                 ret = 1;
 146                                 goto no_kprobe;
 147                         }
 148                         p = __get_cpu_var(current_kprobe);
 149                         if (p->break_handler && p->break_handler(p, regs))
 150                                 goto ss_probe;
 151                 }
 152                 goto no_kprobe;
 153         }
 154
 155         p = get_kprobe(addr);
 156         if (!p) {
 157                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 158                         /*
 159                          * The breakpoint instruction was removed right
 160                          * after we hit it.  Another cpu has removed
 161                          * either a probepoint or a debugger breakpoint
 162                          * at this address.  In either case, no further
 163                          * handling of this interrupt is appropriate.
 164                          */
 165                         ret = 1;
 166                 }
 167                 /* Not one of ours: let kernel handle it */
 168                 goto no_kprobe;
 169         }
 170
 171         set_current_kprobe(p, regs, kcb);
 172         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 173         if (p->pre_handler && p->pre_handler(p, regs))
 174                 return 1;
 175
 176 ss_probe:
 177         prepare_singlestep(p, regs, kcb);
 178         kcb->kprobe_status = KPROBE_HIT_SS;
 179         return 1;
 180
 181 no_kprobe:
 182         preempt_enable_no_resched();
 183         return ret;
 184 }
 185
 186 /* If INSN is a relative control transfer instruction,
 187  * return the corrected branch destination value.
 188  *
 189  * The original INSN location was REAL_PC, it actually
 190  * executed at PC and produced destination address NPC.
 191  */
 192 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 193                                                unsigned long pc,
 194                                                unsigned long npc)
 195 {
 196         /* Branch not taken, no mods necessary.  */
 197         if (npc == pc + 0x4UL)
 198                 return real_pc + 0x4UL;
 199
 200         /* The three cases are call, branch w/prediction,
 201          * and traditional branch.
 202          */
 203         if ((insn & 0xc0000000) == 0x40000000 ||
 204             (insn & 0xc1c00000) == 0x00400000 ||
 205             (insn & 0xc1c00000) == 0x00800000) {
 206                 /* The instruction did all the work for us
 207                  * already, just apply the offset to the correct
 208                  * instruction location.
 209                  */
 210                 return (real_pc + (npc - pc));
 211         }
 212
 213         return real_pc + 0x4UL;
 214 }
 215
 216 /* If INSN is an instruction which writes it's PC location
 217  * into a destination register, fix that up.
 218  */
 219 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 220                                   unsigned long real_pc)
 221 {
 222         unsigned long *slot = NULL;
 223
 224         /* Simplest cast is call, which always uses %o7 */
 225         if ((insn & 0xc0000000) == 0x40000000) {
 226                 slot = &regs->u_regs[UREG_I7];
 227         }
 228
 229         /* Jmpl encodes the register inside of the opcode */
 230         if ((insn & 0xc1f80000) == 0x81c00000) {
 231                 unsigned long rd = ((insn >> 25) & 0x1f);
 232
 233                 if (rd <= 15) {
 234                         slot = &regs->u_regs[rd];
 235                 } else {
 236                         /* Hard case, it goes onto the stack. */
 237                         flushw_all();
 238
 239                         rd -= 16;
 240                         slot = (unsigned long *)
 241                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 242                         slot += rd;
 243                 }
 244         }
 245         if (slot != NULL)
 246                 *slot = real_pc;
 247 }
 248
 249 /*
 250  * Called after single-stepping.  p->addr is the address of the
 251  * instruction whose first byte has been replaced by the breakpoint
 252  * instruction.  To avoid the SMP problems that can occur when we
 253  * temporarily put back the original opcode to single-step, we
 254  * single-stepped a copy of the instruction.  The address of this
 255  * copy is p->ainsn.insn.
 256  *
 257  * This function prepares to return from the post-single-step
 258  * breakpoint trap.
 259  */
 260 static void __kprobes resume_execution(struct kprobe *p,
 261                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 262 {
 263         u32 insn = p->ainsn.insn[0];
 264
 265         regs->tpc = kcb->kprobe_orig_tnpc;
 266         regs->tnpc = relbranch_fixup(insn,
 267                                      (unsigned long) p->addr,
 268                                      (unsigned long) &p->ainsn.insn[0],
 269                                      regs->tnpc);
 270         retpc_fixup(regs, insn, (unsigned long) p->addr);
 271
 272         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 273                         kcb->kprobe_orig_tstate_pil);
 274 }
 275
 276 static inline int post_kprobe_handler(struct pt_regs *regs)
 277 {
 278         struct kprobe *cur = kprobe_running();
 279         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 280
 281         if (!cur)
 282                 return 0;
 283
 284         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 285                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 286                 cur->post_handler(cur, regs, 0);
 287         }
 288
 289         resume_execution(cur, regs, kcb);
 290
 291         /*Restore back the original saved kprobes variables and continue. */
 292         if (kcb->kprobe_status == KPROBE_REENTER) {
 293                 restore_previous_kprobe(kcb);
 294                 goto out;
 295         }
 296         reset_current_kprobe();
 297 out:
 298         preempt_enable_no_resched();
 299
 300         return 1;
 301 }
 302
 303 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 304 {
 305         struct kprobe *cur = kprobe_running();
 306         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 307         const struct exception_table_entry *entry;
 308
 309         switch(kcb->kprobe_status) {
 310         case KPROBE_HIT_SS:
 311         case KPROBE_REENTER:
 312                 /*
 313                  * We are here because the instruction being single
 314                  * stepped caused a page fault. We reset the current
 315                  * kprobe and the tpc points back to the probe address
 316                  * and allow the page fault handler to continue as a
 317                  * normal page fault.
 318                  */
 319                 regs->tpc = (unsigned long)cur->addr;
 320                 regs->tnpc = kcb->kprobe_orig_tnpc;
 321                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 322                                 kcb->kprobe_orig_tstate_pil);
 323                 if (kcb->kprobe_status == KPROBE_REENTER)
 324                         restore_previous_kprobe(kcb);
 325                 else
 326                         reset_current_kprobe();
 327                 preempt_enable_no_resched();
 328                 break;
 329         case KPROBE_HIT_ACTIVE:
 330         case KPROBE_HIT_SSDONE:
 331                 /*
 332                  * We increment the nmissed count for accounting,
 333                  * we can also use npre/npostfault count for accouting
 334                  * these specific fault cases.
 335                  */
 336                 kprobes_inc_nmissed_count(cur);
 337
 338                 /*
 339                  * We come here because instructions in the pre/post
 340                  * handler caused the page_fault, this could happen
 341                  * if handler tries to access user space by
 342                  * copy_from_user(), get_user() etc. Let the
 343                  * user-specified handler try to fix it first.
 344                  */
 345                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 346                         return 1;
 347
 348                 /*
 349                  * In case the user-specified fault handler returned
 350                  * zero, try to fix up.
 351                  */
 352
 353                 entry = search_exception_tables(regs->tpc);
 354                 if (entry) {
 355                         regs->tpc = entry->fixup;
 356                         regs->tnpc = regs->tpc + 4;
 357                         return 1;
 358                 }
 359
 360                 /*
 361                  * fixup_exception() could not handle it,
 362                  * Let do_page_fault() fix it.
 363                  */
 364                 break;
 365         default:
 366                 break;
 367         }
 368
 369         return 0;
 370 }
 371
 372 /*
 373  * Wrapper routine to for handling exceptions.
 374  */
 375 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 376                                        unsigned long val, void *data)
 377 {
 378         struct die_args *args = (struct die_args *)data;
 379         int ret = NOTIFY_DONE;
 380
 381         if (args->regs && user_mode(args->regs))
 382                 return ret;
 383
 384         switch (val) {
 385         case DIE_DEBUG:
 386                 if (kprobe_handler(args->regs))
 387                         ret = NOTIFY_STOP;
 388                 break;
 389         case DIE_DEBUG_2:
 390                 if (post_kprobe_handler(args->regs))
 391                         ret = NOTIFY_STOP;
 392                 break;
 393         case DIE_GPF:
 394         case DIE_PAGE_FAULT:
 395                 /* kprobe_running() needs smp_processor_id() */
 396                 preempt_disable();
 397                 if (kprobe_running() &&
 398                     kprobe_fault_handler(args->regs, args->trapnr))
 399                         ret = NOTIFY_STOP;
 400                 preempt_enable();
 401                 break;
 402         default:
 403                 break;
 404         }
 405         return ret;
 406 }
 407
 408 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 409                                       struct pt_regs *regs)
 410 {
 411         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 412
 413         if (user_mode(regs)) {
 414                 local_irq_enable();
 415                 bad_trap(regs, trap_level);
 416                 return;
 417         }
 418
 419         /* trap_level == 0x170 --> ta 0x70
 420          * trap_level == 0x171 --> ta 0x71
 421          */
 422         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 423                        (trap_level == 0x170) ? "debug" : "debug_2",
 424                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 425                 bad_trap(regs, trap_level);
 426 }
 427
 428 /* Jprobes support.  */
 429 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 430 {
 431         struct jprobe *jp = container_of(p, struct jprobe, kp);
 432         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 433
 434         kcb->jprobe_saved_regs_location = regs;
 435         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 436
 437         /* Save a whole stack frame, this gets arguments
 438          * pushed onto the stack after using up all the
 439          * arg registers.
 440          */
 441         memcpy(&(kcb->jprobe_saved_stack),
 442                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 443                sizeof(kcb->jprobe_saved_stack));
 444
 445         regs->tpc  = (unsigned long) jp->entry;
 446         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 447         regs->tstate |= TSTATE_PIL;
 448
 449         return 1;
 450 }
 451
 452 void __kprobes jprobe_return(void)
 453 {
 454         __asm__ __volatile__(
 455                 ".globl jprobe_return_trap_instruction\n"
 456 "jprobe_return_trap_instruction:\n\t"
 457                 "ta 0x70");
 458 }
 459
 460 extern void jprobe_return_trap_instruction(void);
 461
 462 extern void __show_regs(struct pt_regs * regs);
 463
 464 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 465 {
 466         u32 *addr = (u32 *) regs->tpc;
 467         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 468
 469         if (addr == (u32 *) jprobe_return_trap_instruction) {
 470                 if (kcb->jprobe_saved_regs_location != regs) {
 471                         printk("JPROBE: Current regs (%p) does not match "
 472                                "saved regs (%p).\n",
 473                                regs, kcb->jprobe_saved_regs_location);
 474                         printk("JPROBE: Saved registers\n");
 475                         __show_regs(kcb->jprobe_saved_regs_location);
 476                         printk("JPROBE: Current registers\n");
 477                         __show_regs(regs);
 478                         BUG();
 479                 }
 480                 /* Restore old register state.  Do pt_regs
 481                  * first so that UREG_FP is the original one for
 482                  * the stack frame restore.
 483                  */
 484                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 485
 486                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 487                        &(kcb->jprobe_saved_stack),
 488                        sizeof(kcb->jprobe_saved_stack));
 489
 490                 preempt_enable_no_resched();
 491                 return 1;
 492         }
 493         return 0;
 494 }
 495
 496 /* architecture specific initialization */
 497 int arch_init_kprobes(void)
 498 {
 499         return 0;
 500 }