arch/sparc64/kernel/kprobes.c

   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 <linux/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         flushi(&p->ainsn.insn[0]);
  49
  50         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  51         flushi(&p->ainsn.insn[1]);
  52
  53         p->opcode = *p->addr;
  54         return 0;
  55 }
  56
  57 void __kprobes arch_arm_kprobe(struct kprobe *p)
  58 {
  59         *p->addr = BREAKPOINT_INSTRUCTION;
  60         flushi(p->addr);
  61 }
  62
  63 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  64 {
  65         *p->addr = p->opcode;
  66         flushi(p->addr);
  67 }
  68
  69 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  70 {
  71         kcb->prev_kprobe.kp = kprobe_running();
  72         kcb->prev_kprobe.status = kcb->kprobe_status;
  73         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  74         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  75 }
  76
  77 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  78 {
  79         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  80         kcb->kprobe_status = kcb->prev_kprobe.status;
  81         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  82         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  83 }
  84
  85 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  86                                 struct kprobe_ctlblk *kcb)
  87 {
  88         __get_cpu_var(current_kprobe) = p;
  89         kcb->kprobe_orig_tnpc = regs->tnpc;
  90         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  91 }
  92
  93 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  94                         struct kprobe_ctlblk *kcb)
  95 {
  96         regs->tstate |= TSTATE_PIL;
  97
  98         /*single step inline, if it a breakpoint instruction*/
  99         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 100                 regs->tpc = (unsigned long) p->addr;
 101                 regs->tnpc = kcb->kprobe_orig_tnpc;
 102         } else {
 103                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 104                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 105         }
 106 }
 107
 108 static int __kprobes kprobe_handler(struct pt_regs *regs)
 109 {
 110         struct kprobe *p;
 111         void *addr = (void *) regs->tpc;
 112         int ret = 0;
 113         struct kprobe_ctlblk *kcb;
 114
 115         /*
 116          * We don't want to be preempted for the entire
 117          * duration of kprobe processing
 118          */
 119         preempt_disable();
 120         kcb = get_kprobe_ctlblk();
 121
 122         if (kprobe_running()) {
 123                 p = get_kprobe(addr);
 124                 if (p) {
 125                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 126                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 127                                         kcb->kprobe_orig_tstate_pil);
 128                                 goto no_kprobe;
 129                         }
 130                         /* We have reentered the kprobe_handler(), since
 131                          * another probe was hit while within the handler.
 132                          * We here save the original kprobes variables and
 133                          * just single step on the instruction of the new probe
 134                          * without calling any user handlers.
 135                          */
 136                         save_previous_kprobe(kcb);
 137                         set_current_kprobe(p, regs, kcb);
 138                         kprobes_inc_nmissed_count(p);
 139                         kcb->kprobe_status = KPROBE_REENTER;
 140                         prepare_singlestep(p, regs, kcb);
 141                         return 1;
 142                 } else {
 143                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 144                         /* The breakpoint instruction was removed by
 145                          * another cpu right after we hit, no further
 146                          * handling of this interrupt is appropriate
 147                          */
 148                                 ret = 1;
 149                                 goto no_kprobe;
 150                         }
 151                         p = __get_cpu_var(current_kprobe);
 152                         if (p->break_handler && p->break_handler(p, regs))
 153                                 goto ss_probe;
 154                 }
 155                 goto no_kprobe;
 156         }
 157
 158         p = get_kprobe(addr);
 159         if (!p) {
 160                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 161                         /*
 162                          * The breakpoint instruction was removed right
 163                          * after we hit it.  Another cpu has removed
 164                          * either a probepoint or a debugger breakpoint
 165                          * at this address.  In either case, no further
 166                          * handling of this interrupt is appropriate.
 167                          */
 168                         ret = 1;
 169                 }
 170                 /* Not one of ours: let kernel handle it */
 171                 goto no_kprobe;
 172         }
 173
 174         set_current_kprobe(p, regs, kcb);
 175         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 176         if (p->pre_handler && p->pre_handler(p, regs))
 177                 return 1;
 178
 179 ss_probe:
 180         prepare_singlestep(p, regs, kcb);
 181         kcb->kprobe_status = KPROBE_HIT_SS;
 182         return 1;
 183
 184 no_kprobe:
 185         preempt_enable_no_resched();
 186         return ret;
 187 }
 188
 189 /* If INSN is a relative control transfer instruction,
 190  * return the corrected branch destination value.
 191  *
 192  * regs->tpc and regs->tnpc still hold the values of the
 193  * program counters at the time of trap due to the execution
 194  * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1]
 195  *
 196  */
 197 static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p,
 198                                                struct pt_regs *regs)
 199 {
 200         unsigned long real_pc = (unsigned long) p->addr;
 201
 202         /* Branch not taken, no mods necessary.  */
 203         if (regs->tnpc == regs->tpc + 0x4UL)
 204                 return real_pc + 0x8UL;
 205
 206         /* The three cases are call, branch w/prediction,
 207          * and traditional branch.
 208          */
 209         if ((insn & 0xc0000000) == 0x40000000 ||
 210             (insn & 0xc1c00000) == 0x00400000 ||
 211             (insn & 0xc1c00000) == 0x00800000) {
 212                 unsigned long ainsn_addr;
 213
 214                 ainsn_addr = (unsigned long) &p->ainsn.insn[0];
 215
 216                 /* The instruction did all the work for us
 217                  * already, just apply the offset to the correct
 218                  * instruction location.
 219                  */
 220                 return (real_pc + (regs->tnpc - ainsn_addr));
 221         }
 222
 223         /* It is jmpl or some other absolute PC modification instruction,
 224          * leave NPC as-is.
 225          */
 226         return regs->tnpc;
 227 }
 228
 229 /* If INSN is an instruction which writes it's PC location
 230  * into a destination register, fix that up.
 231  */
 232 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 233                                   unsigned long real_pc)
 234 {
 235         unsigned long *slot = NULL;
 236
 237         /* Simplest case is 'call', which always uses %o7 */
 238         if ((insn & 0xc0000000) == 0x40000000) {
 239                 slot = &regs->u_regs[UREG_I7];
 240         }
 241
 242         /* 'jmpl' encodes the register inside of the opcode */
 243         if ((insn & 0xc1f80000) == 0x81c00000) {
 244                 unsigned long rd = ((insn >> 25) & 0x1f);
 245
 246                 if (rd <= 15) {
 247                         slot = &regs->u_regs[rd];
 248                 } else {
 249                         /* Hard case, it goes onto the stack. */
 250                         flushw_all();
 251
 252                         rd -= 16;
 253                         slot = (unsigned long *)
 254                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 255                         slot += rd;
 256                 }
 257         }
 258         if (slot != NULL)
 259                 *slot = real_pc;
 260 }
 261
 262 /*
 263  * Called after single-stepping.  p->addr is the address of the
 264  * instruction which has been replaced by the breakpoint
 265  * instruction.  To avoid the SMP problems that can occur when we
 266  * temporarily put back the original opcode to single-step, we
 267  * single-stepped a copy of the instruction.  The address of this
 268  * copy is &p->ainsn.insn[0].
 269  *
 270  * This function prepares to return from the post-single-step
 271  * breakpoint trap.
 272  */
 273 static void __kprobes resume_execution(struct kprobe *p,
 274                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 275 {
 276         u32 insn = p->ainsn.insn[0];
 277
 278         regs->tnpc = relbranch_fixup(insn, p, regs);
 279
 280         /* This assignment must occur after relbranch_fixup() */
 281         regs->tpc = kcb->kprobe_orig_tnpc;
 282
 283         retpc_fixup(regs, insn, (unsigned long) p->addr);
 284
 285         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 286                         kcb->kprobe_orig_tstate_pil);
 287 }
 288
 289 static int __kprobes 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 int __kprobes 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         const struct exception_table_entry *entry;
 321
 322         switch(kcb->kprobe_status) {
 323         case KPROBE_HIT_SS:
 324         case KPROBE_REENTER:
 325                 /*
 326                  * We are here because the instruction being single
 327                  * stepped caused a page fault. We reset the current
 328                  * kprobe and the tpc points back to the probe address
 329                  * and allow the page fault handler to continue as a
 330                  * normal page fault.
 331                  */
 332                 regs->tpc = (unsigned long)cur->addr;
 333                 regs->tnpc = kcb->kprobe_orig_tnpc;
 334                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 335                                 kcb->kprobe_orig_tstate_pil);
 336                 if (kcb->kprobe_status == KPROBE_REENTER)
 337                         restore_previous_kprobe(kcb);
 338                 else
 339                         reset_current_kprobe();
 340                 preempt_enable_no_resched();
 341                 break;
 342         case KPROBE_HIT_ACTIVE:
 343         case KPROBE_HIT_SSDONE:
 344                 /*
 345                  * We increment the nmissed count for accounting,
 346                  * we can also use npre/npostfault count for accouting
 347                  * these specific fault cases.
 348                  */
 349                 kprobes_inc_nmissed_count(cur);
 350
 351                 /*
 352                  * We come here because instructions in the pre/post
 353                  * handler caused the page_fault, this could happen
 354                  * if handler tries to access user space by
 355                  * copy_from_user(), get_user() etc. Let the
 356                  * user-specified handler try to fix it first.
 357                  */
 358                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 359                         return 1;
 360
 361                 /*
 362                  * In case the user-specified fault handler returned
 363                  * zero, try to fix up.
 364                  */
 365
 366                 entry = search_exception_tables(regs->tpc);
 367                 if (entry) {
 368                         regs->tpc = entry->fixup;
 369                         regs->tnpc = regs->tpc + 4;
 370                         return 1;
 371                 }
 372
 373                 /*
 374                  * fixup_exception() could not handle it,
 375                  * Let do_page_fault() fix it.
 376                  */
 377                 break;
 378         default:
 379                 break;
 380         }
 381
 382         return 0;
 383 }
 384
 385 /*
 386  * Wrapper routine to for handling exceptions.
 387  */
 388 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 389                                        unsigned long val, void *data)
 390 {
 391         struct die_args *args = (struct die_args *)data;
 392         int ret = NOTIFY_DONE;
 393
 394         if (args->regs && user_mode(args->regs))
 395                 return ret;
 396
 397         switch (val) {
 398         case DIE_DEBUG:
 399                 if (kprobe_handler(args->regs))
 400                         ret = NOTIFY_STOP;
 401                 break;
 402         case DIE_DEBUG_2:
 403                 if (post_kprobe_handler(args->regs))
 404                         ret = NOTIFY_STOP;
 405                 break;
 406         case DIE_GPF:
 407         case DIE_PAGE_FAULT:
 408                 /* kprobe_running() needs smp_processor_id() */
 409                 preempt_disable();
 410                 if (kprobe_running() &&
 411                     kprobe_fault_handler(args->regs, args->trapnr))
 412                         ret = NOTIFY_STOP;
 413                 preempt_enable();
 414                 break;
 415         default:
 416                 break;
 417         }
 418         return ret;
 419 }
 420
 421 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 422                                       struct pt_regs *regs)
 423 {
 424         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 425
 426         if (user_mode(regs)) {
 427                 local_irq_enable();
 428                 bad_trap(regs, trap_level);
 429                 return;
 430         }
 431
 432         /* trap_level == 0x170 --> ta 0x70
 433          * trap_level == 0x171 --> ta 0x71
 434          */
 435         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 436                        (trap_level == 0x170) ? "debug" : "debug_2",
 437                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 438                 bad_trap(regs, trap_level);
 439 }
 440
 441 /* Jprobes support.  */
 442 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 443 {
 444         struct jprobe *jp = container_of(p, struct jprobe, kp);
 445         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 446
 447         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 448
 449         regs->tpc  = (unsigned long) jp->entry;
 450         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 451         regs->tstate |= TSTATE_PIL;
 452
 453         return 1;
 454 }
 455
 456 void __kprobes jprobe_return(void)
 457 {
 458         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 459         register unsigned long orig_fp asm("g1");
 460
 461         orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP];
 462         __asm__ __volatile__("\n"
 463 "1:     cmp             %%sp, %0\n\t"
 464         "blu,a,pt       %%xcc, 1b\n\t"
 465         " restore\n\t"
 466         ".globl         jprobe_return_trap_instruction\n"
 467 "jprobe_return_trap_instruction:\n\t"
 468         "ta             0x70"
 469         : /* no outputs */
 470         : "r" (orig_fp));
 471 }
 472
 473 extern void jprobe_return_trap_instruction(void);
 474
 475 extern void __show_regs(struct pt_regs * regs);
 476
 477 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 478 {
 479         u32 *addr = (u32 *) regs->tpc;
 480         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 481
 482         if (addr == (u32 *) jprobe_return_trap_instruction) {
 483                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 484                 preempt_enable_no_resched();
 485                 return 1;
 486         }
 487         return 0;
 488 }
 489
 490 /* architecture specific initialization */
 491 int arch_init_kprobes(void)
 492 {
 493         return 0;
 494 }