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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 <asm/kdebug.h>
  10 #include <asm/signal.h>
  11 #include <asm/cacheflush.h>
  12
  13 /* We do not have hardware single-stepping on sparc64.
  14  * So we implement software single-stepping with breakpoint
  15  * traps.  The top-level scheme is similar to that used
  16  * in the x86 kprobes implementation.
  17  *
  18  * In the kprobe->ainsn.insn[] array we store the original
  19  * instruction at index zero and a break instruction at
  20  * index one.
  21  *
  22  * When we hit a kprobe we:
  23  * - Run the pre-handler
  24  * - Remember "regs->tnpc" and interrupt level stored in
  25  *   "regs->tstate" so we can restore them later
  26  * - Disable PIL interrupts
  27  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  28  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  29  * - Mark that we are actively in a kprobe
  30  *
  31  * At this point we wait for the second breakpoint at
  32  * kprobe->ainsn.insn[1] to hit.  When it does we:
  33  * - Run the post-handler
  34  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  35  *   restore the PIL interrupt level in "regs->tstate" as well
  36  * - Make any adjustments necessary to regs->tnpc in order
  37  *   to handle relative branches correctly.  See below.
  38  * - Mark that we are no longer actively in a kprobe.
  39  */
  40
  41 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  42 {
  43         return 0;
  44 }
  45
  46 void __kprobes arch_copy_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 }
  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 void __kprobes arch_remove_kprobe(struct kprobe *p)
  66 {
  67 }
  68
  69 static struct kprobe *current_kprobe;
  70 static unsigned long current_kprobe_orig_tnpc;
  71 static unsigned long current_kprobe_orig_tstate_pil;
  72 static unsigned int kprobe_status;
  73 static struct kprobe *kprobe_prev;
  74 static unsigned long kprobe_orig_tnpc_prev;
  75 static unsigned long kprobe_orig_tstate_pil_prev;
  76 static unsigned int kprobe_status_prev;
  77
  78 static inline void save_previous_kprobe(void)
  79 {
  80         kprobe_status_prev = kprobe_status;
  81         kprobe_orig_tnpc_prev = current_kprobe_orig_tnpc;
  82         kprobe_orig_tstate_pil_prev = current_kprobe_orig_tstate_pil;
  83         kprobe_prev = current_kprobe;
  84 }
  85
  86 static inline void restore_previous_kprobe(void)
  87 {
  88         kprobe_status = kprobe_status_prev;
  89         current_kprobe_orig_tnpc = kprobe_orig_tnpc_prev;
  90         current_kprobe_orig_tstate_pil = kprobe_orig_tstate_pil_prev;
  91         current_kprobe = kprobe_prev;
  92 }
  93
  94 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
  95 {
  96         current_kprobe_orig_tnpc = regs->tnpc;
  97         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  98         current_kprobe = p;
  99 }
 100
 101 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 102 {
 103         regs->tstate |= TSTATE_PIL;
 104
 105         /*single step inline, if it a breakpoint instruction*/
 106         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 107                 regs->tpc = (unsigned long) p->addr;
 108                 regs->tnpc = current_kprobe_orig_tnpc;
 109         } else {
 110                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 111                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 112         }
 113 }
 114
 115 static int __kprobes kprobe_handler(struct pt_regs *regs)
 116 {
 117         struct kprobe *p;
 118         void *addr = (void *) regs->tpc;
 119         int ret = 0;
 120
 121         preempt_disable();
 122
 123         if (kprobe_running()) {
 124                 /* We *are* holding lock here, so this is safe.
 125                  * Disarm the probe we just hit, and ignore it.
 126                  */
 127                 p = get_kprobe(addr);
 128                 if (p) {
 129                         if (kprobe_status == KPROBE_HIT_SS) {
 130                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 131                                         current_kprobe_orig_tstate_pil);
 132                                 unlock_kprobes();
 133                                 goto no_kprobe;
 134                         }
 135                         /* We have reentered the kprobe_handler(), since
 136                          * another probe was hit while within the handler.
 137                          * We here save the original kprobes variables and
 138                          * just single step on the instruction of the new probe
 139                          * without calling any user handlers.
 140                          */
 141                         save_previous_kprobe();
 142                         set_current_kprobe(p, regs);
 143                         p->nmissed++;
 144                         kprobe_status = KPROBE_REENTER;
 145                         prepare_singlestep(p, regs);
 146                         return 1;
 147                 } else {
 148                         p = current_kprobe;
 149                         if (p->break_handler && p->break_handler(p, regs))
 150                                 goto ss_probe;
 151                 }
 152                 /* If it's not ours, can't be delete race, (we hold lock). */
 153                 goto no_kprobe;
 154         }
 155
 156         lock_kprobes();
 157         p = get_kprobe(addr);
 158         if (!p) {
 159                 unlock_kprobes();
 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);
 175         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);
 181         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  * The original INSN location was REAL_PC, it actually
 193  * executed at PC and produced destination address NPC.
 194  */
 195 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 196                                                unsigned long pc,
 197                                                unsigned long npc)
 198 {
 199         /* Branch not taken, no mods necessary.  */
 200         if (npc == pc + 0x4UL)
 201                 return real_pc + 0x4UL;
 202
 203         /* The three cases are call, branch w/prediction,
 204          * and traditional branch.
 205          */
 206         if ((insn & 0xc0000000) == 0x40000000 ||
 207             (insn & 0xc1c00000) == 0x00400000 ||
 208             (insn & 0xc1c00000) == 0x00800000) {
 209                 /* The instruction did all the work for us
 210                  * already, just apply the offset to the correct
 211                  * instruction location.
 212                  */
 213                 return (real_pc + (npc - pc));
 214         }
 215
 216         return real_pc + 0x4UL;
 217 }
 218
 219 /* If INSN is an instruction which writes it's PC location
 220  * into a destination register, fix that up.
 221  */
 222 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 223                                   unsigned long real_pc)
 224 {
 225         unsigned long *slot = NULL;
 226
 227         /* Simplest cast is call, which always uses %o7 */
 228         if ((insn & 0xc0000000) == 0x40000000) {
 229                 slot = &regs->u_regs[UREG_I7];
 230         }
 231
 232         /* Jmpl encodes the register inside of the opcode */
 233         if ((insn & 0xc1f80000) == 0x81c00000) {
 234                 unsigned long rd = ((insn >> 25) & 0x1f);
 235
 236                 if (rd <= 15) {
 237                         slot = &regs->u_regs[rd];
 238                 } else {
 239                         /* Hard case, it goes onto the stack. */
 240                         flushw_all();
 241
 242                         rd -= 16;
 243                         slot = (unsigned long *)
 244                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 245                         slot += rd;
 246                 }
 247         }
 248         if (slot != NULL)
 249                 *slot = real_pc;
 250 }
 251
 252 /*
 253  * Called after single-stepping.  p->addr is the address of the
 254  * instruction whose first byte has been replaced by the breakpoint
 255  * instruction.  To avoid the SMP problems that can occur when we
 256  * temporarily put back the original opcode to single-step, we
 257  * single-stepped a copy of the instruction.  The address of this
 258  * copy is p->ainsn.insn.
 259  *
 260  * This function prepares to return from the post-single-step
 261  * breakpoint trap.
 262  */
 263 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 264 {
 265         u32 insn = p->ainsn.insn[0];
 266
 267         regs->tpc = current_kprobe_orig_tnpc;
 268         regs->tnpc = relbranch_fixup(insn,
 269                                      (unsigned long) p->addr,
 270                                      (unsigned long) &p->ainsn.insn[0],
 271                                      regs->tnpc);
 272         retpc_fixup(regs, insn, (unsigned long) p->addr);
 273
 274         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 275                         current_kprobe_orig_tstate_pil);
 276 }
 277
 278 static inline int post_kprobe_handler(struct pt_regs *regs)
 279 {
 280         if (!kprobe_running())
 281                 return 0;
 282
 283         if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
 284                 kprobe_status = KPROBE_HIT_SSDONE;
 285                 current_kprobe->post_handler(current_kprobe, regs, 0);
 286         }
 287
 288         resume_execution(current_kprobe, regs);
 289
 290         /*Restore back the original saved kprobes variables and continue. */
 291         if (kprobe_status == KPROBE_REENTER) {
 292                 restore_previous_kprobe();
 293                 goto out;
 294         }
 295         unlock_kprobes();
 296 out:
 297         preempt_enable_no_resched();
 298
 299         return 1;
 300 }
 301
 302 /* Interrupts disabled, kprobe_lock held. */
 303 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 304 {
 305         if (current_kprobe->fault_handler
 306             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
 307                 return 1;
 308
 309         if (kprobe_status & KPROBE_HIT_SS) {
 310                 resume_execution(current_kprobe, regs);
 311
 312                 unlock_kprobes();
 313                 preempt_enable_no_resched();
 314         }
 315         return 0;
 316 }
 317
 318 /*
 319  * Wrapper routine to for handling exceptions.
 320  */
 321 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 322                                        unsigned long val, void *data)
 323 {
 324         struct die_args *args = (struct die_args *)data;
 325         switch (val) {
 326         case DIE_DEBUG:
 327                 if (kprobe_handler(args->regs))
 328                         return NOTIFY_STOP;
 329                 break;
 330         case DIE_DEBUG_2:
 331                 if (post_kprobe_handler(args->regs))
 332                         return NOTIFY_STOP;
 333                 break;
 334         case DIE_GPF:
 335                 if (kprobe_running() &&
 336                     kprobe_fault_handler(args->regs, args->trapnr))
 337                         return NOTIFY_STOP;
 338                 break;
 339         case DIE_PAGE_FAULT:
 340                 if (kprobe_running() &&
 341                     kprobe_fault_handler(args->regs, args->trapnr))
 342                         return NOTIFY_STOP;
 343                 break;
 344         default:
 345                 break;
 346         }
 347         return NOTIFY_DONE;
 348 }
 349
 350 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 351                                       struct pt_regs *regs)
 352 {
 353         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 354
 355         if (user_mode(regs)) {
 356                 local_irq_enable();
 357                 bad_trap(regs, trap_level);
 358                 return;
 359         }
 360
 361         /* trap_level == 0x170 --> ta 0x70
 362          * trap_level == 0x171 --> ta 0x71
 363          */
 364         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 365                        (trap_level == 0x170) ? "debug" : "debug_2",
 366                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 367                 bad_trap(regs, trap_level);
 368 }
 369
 370 /* Jprobes support.  */
 371 static struct pt_regs jprobe_saved_regs;
 372 static struct pt_regs *jprobe_saved_regs_location;
 373 static struct sparc_stackf jprobe_saved_stack;
 374
 375 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 376 {
 377         struct jprobe *jp = container_of(p, struct jprobe, kp);
 378
 379         jprobe_saved_regs_location = regs;
 380         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
 381
 382         /* Save a whole stack frame, this gets arguments
 383          * pushed onto the stack after using up all the
 384          * arg registers.
 385          */
 386         memcpy(&jprobe_saved_stack,
 387                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 388                sizeof(jprobe_saved_stack));
 389
 390         regs->tpc  = (unsigned long) jp->entry;
 391         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 392         regs->tstate |= TSTATE_PIL;
 393
 394         return 1;
 395 }
 396
 397 void __kprobes jprobe_return(void)
 398 {
 399         preempt_enable_no_resched();
 400         __asm__ __volatile__(
 401                 ".globl jprobe_return_trap_instruction\n"
 402 "jprobe_return_trap_instruction:\n\t"
 403                 "ta 0x70");
 404 }
 405
 406 extern void jprobe_return_trap_instruction(void);
 407
 408 extern void __show_regs(struct pt_regs * regs);
 409
 410 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 411 {
 412         u32 *addr = (u32 *) regs->tpc;
 413
 414         if (addr == (u32 *) jprobe_return_trap_instruction) {
 415                 if (jprobe_saved_regs_location != regs) {
 416                         printk("JPROBE: Current regs (%p) does not match "
 417                                "saved regs (%p).\n",
 418                                regs, jprobe_saved_regs_location);
 419                         printk("JPROBE: Saved registers\n");
 420                         __show_regs(jprobe_saved_regs_location);
 421                         printk("JPROBE: Current registers\n");
 422                         __show_regs(regs);
 423                         BUG();
 424                 }
 425                 /* Restore old register state.  Do pt_regs
 426                  * first so that UREG_FP is the original one for
 427                  * the stack frame restore.
 428                  */
 429                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
 430
 431                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 432                        &jprobe_saved_stack,
 433                        sizeof(jprobe_saved_stack));
 434
 435                 return 1;
 436         }
 437         return 0;
 438 }
 439
 440 /* architecture specific initialization */
 441 int arch_init_kprobes(void)
 442 {
 443         return 0;
 444 }