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/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 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  42 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  43
  44 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  45 {
  46         return 0;
  47 }
  48
  49 void __kprobes arch_copy_kprobe(struct kprobe *p)
  50 {
  51         p->ainsn.insn[0] = *p->addr;
  52         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  53         p->opcode = *p->addr;
  54 }
  55
  56 void __kprobes arch_arm_kprobe(struct kprobe *p)
  57 {
  58         *p->addr = BREAKPOINT_INSTRUCTION;
  59         flushi(p->addr);
  60 }
  61
  62 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  63 {
  64         *p->addr = p->opcode;
  65         flushi(p->addr);
  66 }
  67
  68 void __kprobes arch_remove_kprobe(struct kprobe *p)
  69 {
  70 }
  71
  72 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
  73 {
  74         kcb->prev_kprobe.kp = kprobe_running();
  75         kcb->prev_kprobe.status = kcb->kprobe_status;
  76         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  77         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  78 }
  79
  80 static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  81 {
  82         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  83         kcb->kprobe_status = kcb->prev_kprobe.status;
  84         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  85         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  86 }
  87
  88 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  89                                 struct kprobe_ctlblk *kcb)
  90 {
  91         __get_cpu_var(current_kprobe) = p;
  92         kcb->kprobe_orig_tnpc = regs->tnpc;
  93         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  94 }
  95
  96 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  97                         struct kprobe_ctlblk *kcb)
  98 {
  99         regs->tstate |= TSTATE_PIL;
 100
 101         /*single step inline, if it a breakpoint instruction*/
 102         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 103                 regs->tpc = (unsigned long) p->addr;
 104                 regs->tnpc = kcb->kprobe_orig_tnpc;
 105         } else {
 106                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 107                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 108         }
 109 }
 110
 111 static int __kprobes kprobe_handler(struct pt_regs *regs)
 112 {
 113         struct kprobe *p;
 114         void *addr = (void *) regs->tpc;
 115         int ret = 0;
 116         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 117
 118         if (kprobe_running()) {
 119                 /* We *are* holding lock here, so this is safe.
 120                  * Disarm the probe we just hit, and ignore it.
 121                  */
 122                 p = get_kprobe(addr);
 123                 if (p) {
 124                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 125                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 126                                         kcb->kprobe_orig_tstate_pil);
 127                                 unlock_kprobes();
 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                         p->nmissed++;
 139                         kcb->kprobe_status = KPROBE_REENTER;
 140                         prepare_singlestep(p, regs, kcb);
 141                         return 1;
 142                 } else {
 143                         p = __get_cpu_var(current_kprobe);
 144                         if (p->break_handler && p->break_handler(p, regs))
 145                                 goto ss_probe;
 146                 }
 147                 /* If it's not ours, can't be delete race, (we hold lock). */
 148                 goto no_kprobe;
 149         }
 150
 151         lock_kprobes();
 152         p = get_kprobe(addr);
 153         if (!p) {
 154                 unlock_kprobes();
 155                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 156                         /*
 157                          * The breakpoint instruction was removed right
 158                          * after we hit it.  Another cpu has removed
 159                          * either a probepoint or a debugger breakpoint
 160                          * at this address.  In either case, no further
 161                          * handling of this interrupt is appropriate.
 162                          */
 163                         ret = 1;
 164                 }
 165                 /* Not one of ours: let kernel handle it */
 166                 goto no_kprobe;
 167         }
 168
 169         /*
 170          * This preempt_disable() matches the preempt_enable_no_resched()
 171          * in post_kprobes_handler()
 172          */
 173         preempt_disable();
 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         return ret;
 186 }
 187
 188 /* If INSN is a relative control transfer instruction,
 189  * return the corrected branch destination value.
 190  *
 191  * The original INSN location was REAL_PC, it actually
 192  * executed at PC and produced destination address NPC.
 193  */
 194 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 195                                                unsigned long pc,
 196                                                unsigned long npc)
 197 {
 198         /* Branch not taken, no mods necessary.  */
 199         if (npc == pc + 0x4UL)
 200                 return real_pc + 0x4UL;
 201
 202         /* The three cases are call, branch w/prediction,
 203          * and traditional branch.
 204          */
 205         if ((insn & 0xc0000000) == 0x40000000 ||
 206             (insn & 0xc1c00000) == 0x00400000 ||
 207             (insn & 0xc1c00000) == 0x00800000) {
 208                 /* The instruction did all the work for us
 209                  * already, just apply the offset to the correct
 210                  * instruction location.
 211                  */
 212                 return (real_pc + (npc - pc));
 213         }
 214
 215         return real_pc + 0x4UL;
 216 }
 217
 218 /* If INSN is an instruction which writes it's PC location
 219  * into a destination register, fix that up.
 220  */
 221 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 222                                   unsigned long real_pc)
 223 {
 224         unsigned long *slot = NULL;
 225
 226         /* Simplest cast is call, which always uses %o7 */
 227         if ((insn & 0xc0000000) == 0x40000000) {
 228                 slot = &regs->u_regs[UREG_I7];
 229         }
 230
 231         /* Jmpl encodes the register inside of the opcode */
 232         if ((insn & 0xc1f80000) == 0x81c00000) {
 233                 unsigned long rd = ((insn >> 25) & 0x1f);
 234
 235                 if (rd <= 15) {
 236                         slot = &regs->u_regs[rd];
 237                 } else {
 238                         /* Hard case, it goes onto the stack. */
 239                         flushw_all();
 240
 241                         rd -= 16;
 242                         slot = (unsigned long *)
 243                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 244                         slot += rd;
 245                 }
 246         }
 247         if (slot != NULL)
 248                 *slot = real_pc;
 249 }
 250
 251 /*
 252  * Called after single-stepping.  p->addr is the address of the
 253  * instruction whose first byte has been replaced by the breakpoint
 254  * instruction.  To avoid the SMP problems that can occur when we
 255  * temporarily put back the original opcode to single-step, we
 256  * single-stepped a copy of the instruction.  The address of this
 257  * copy is p->ainsn.insn.
 258  *
 259  * This function prepares to return from the post-single-step
 260  * breakpoint trap.
 261  */
 262 static void __kprobes resume_execution(struct kprobe *p,
 263                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 264 {
 265         u32 insn = p->ainsn.insn[0];
 266
 267         regs->tpc = kcb->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                         kcb->kprobe_orig_tstate_pil);
 276 }
 277
 278 static inline int post_kprobe_handler(struct pt_regs *regs)
 279 {
 280         struct kprobe *cur = kprobe_running();
 281         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 282
 283         if (!cur)
 284                 return 0;
 285
 286         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 287                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 288                 cur->post_handler(cur, regs, 0);
 289         }
 290
 291         resume_execution(cur, regs, kcb);
 292
 293         /*Restore back the original saved kprobes variables and continue. */
 294         if (kcb->kprobe_status == KPROBE_REENTER) {
 295                 restore_previous_kprobe(kcb);
 296                 goto out;
 297         }
 298         reset_current_kprobe();
 299         unlock_kprobes();
 300 out:
 301         preempt_enable_no_resched();
 302
 303         return 1;
 304 }
 305
 306 /* Interrupts disabled, kprobe_lock held. */
 307 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 308 {
 309         struct kprobe *cur = kprobe_running();
 310         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 311
 312         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 313                 return 1;
 314
 315         if (kcb->kprobe_status & KPROBE_HIT_SS) {
 316                 resume_execution(cur, regs, kcb);
 317
 318                 reset_current_kprobe();
 319                 unlock_kprobes();
 320                 preempt_enable_no_resched();
 321         }
 322         return 0;
 323 }
 324
 325 /*
 326  * Wrapper routine to for handling exceptions.
 327  */
 328 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 329                                        unsigned long val, void *data)
 330 {
 331         struct die_args *args = (struct die_args *)data;
 332         int ret = NOTIFY_DONE;
 333
 334         preempt_disable();
 335         switch (val) {
 336         case DIE_DEBUG:
 337                 if (kprobe_handler(args->regs))
 338                         ret = NOTIFY_STOP;
 339                 break;
 340         case DIE_DEBUG_2:
 341                 if (post_kprobe_handler(args->regs))
 342                         ret = NOTIFY_STOP;
 343                 break;
 344         case DIE_GPF:
 345         case DIE_PAGE_FAULT:
 346                 if (kprobe_running() &&
 347                     kprobe_fault_handler(args->regs, args->trapnr))
 348                         ret = NOTIFY_STOP;
 349                 break;
 350         default:
 351                 break;
 352         }
 353         preempt_enable();
 354         return ret;
 355 }
 356
 357 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 358                                       struct pt_regs *regs)
 359 {
 360         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 361
 362         if (user_mode(regs)) {
 363                 local_irq_enable();
 364                 bad_trap(regs, trap_level);
 365                 return;
 366         }
 367
 368         /* trap_level == 0x170 --> ta 0x70
 369          * trap_level == 0x171 --> ta 0x71
 370          */
 371         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 372                        (trap_level == 0x170) ? "debug" : "debug_2",
 373                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 374                 bad_trap(regs, trap_level);
 375 }
 376
 377 /* Jprobes support.  */
 378 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 379 {
 380         struct jprobe *jp = container_of(p, struct jprobe, kp);
 381         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 382
 383         kcb->jprobe_saved_regs_location = regs;
 384         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 385
 386         /* Save a whole stack frame, this gets arguments
 387          * pushed onto the stack after using up all the
 388          * arg registers.
 389          */
 390         memcpy(&(kcb->jprobe_saved_stack),
 391                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 392                sizeof(kcb->jprobe_saved_stack));
 393
 394         regs->tpc  = (unsigned long) jp->entry;
 395         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 396         regs->tstate |= TSTATE_PIL;
 397
 398         return 1;
 399 }
 400
 401 void __kprobes jprobe_return(void)
 402 {
 403         __asm__ __volatile__(
 404                 ".globl jprobe_return_trap_instruction\n"
 405 "jprobe_return_trap_instruction:\n\t"
 406                 "ta 0x70");
 407 }
 408
 409 extern void jprobe_return_trap_instruction(void);
 410
 411 extern void __show_regs(struct pt_regs * regs);
 412
 413 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 414 {
 415         u32 *addr = (u32 *) regs->tpc;
 416         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 417
 418         if (addr == (u32 *) jprobe_return_trap_instruction) {
 419                 if (kcb->jprobe_saved_regs_location != regs) {
 420                         printk("JPROBE: Current regs (%p) does not match "
 421                                "saved regs (%p).\n",
 422                                regs, kcb->jprobe_saved_regs_location);
 423                         printk("JPROBE: Saved registers\n");
 424                         __show_regs(kcb->jprobe_saved_regs_location);
 425                         printk("JPROBE: Current registers\n");
 426                         __show_regs(regs);
 427                         BUG();
 428                 }
 429                 /* Restore old register state.  Do pt_regs
 430                  * first so that UREG_FP is the original one for
 431                  * the stack frame restore.
 432                  */
 433                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 434
 435                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 436                        &(kcb->jprobe_saved_stack),
 437                        sizeof(kcb->jprobe_saved_stack));
 438
 439                 return 1;
 440         }
 441         return 0;
 442 }
 443
 444 /* architecture specific initialization */
 445 int arch_init_kprobes(void)
 446 {
 447         return 0;
 448 }