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 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         if (kprobe_running()) {
 122                 /* We *are* holding lock here, so this is safe.
 123                  * Disarm the probe we just hit, and ignore it.
 124                  */
 125                 p = get_kprobe(addr);
 126                 if (p) {
 127                         if (kprobe_status == KPROBE_HIT_SS) {
 128                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 129                                         current_kprobe_orig_tstate_pil);
 130                                 unlock_kprobes();
 131                                 goto no_kprobe;
 132                         }
 133                         /* We have reentered the kprobe_handler(), since
 134                          * another probe was hit while within the handler.
 135                          * We here save the original kprobes variables and
 136                          * just single step on the instruction of the new probe
 137                          * without calling any user handlers.
 138                          */
 139                         save_previous_kprobe();
 140                         set_current_kprobe(p, regs);
 141                         p->nmissed++;
 142                         kprobe_status = KPROBE_REENTER;
 143                         prepare_singlestep(p, regs);
 144                         return 1;
 145                 } else {
 146                         p = current_kprobe;
 147                         if (p->break_handler && p->break_handler(p, regs))
 148                                 goto ss_probe;
 149                 }
 150                 /* If it's not ours, can't be delete race, (we hold lock). */
 151                 goto no_kprobe;
 152         }
 153
 154         lock_kprobes();
 155         p = get_kprobe(addr);
 156         if (!p) {
 157                 unlock_kprobes();
 158                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 159                         /*
 160                          * The breakpoint instruction was removed right
 161                          * after we hit it.  Another cpu has removed
 162                          * either a probepoint or a debugger breakpoint
 163                          * at this address.  In either case, no further
 164                          * handling of this interrupt is appropriate.
 165                          */
 166                         ret = 1;
 167                 }
 168                 /* Not one of ours: let kernel handle it */
 169                 goto no_kprobe;
 170         }
 171
 172         /*
 173          * This preempt_disable() matches the preempt_enable_no_resched()
 174          * in post_kprobes_handler()
 175          */
 176         preempt_disable();
 177         set_current_kprobe(p, regs);
 178         kprobe_status = KPROBE_HIT_ACTIVE;
 179         if (p->pre_handler && p->pre_handler(p, regs))
 180                 return 1;
 181
 182 ss_probe:
 183         prepare_singlestep(p, regs);
 184         kprobe_status = KPROBE_HIT_SS;
 185         return 1;
 186
 187 no_kprobe:
 188         return ret;
 189 }
 190
 191 /* If INSN is a relative control transfer instruction,
 192  * return the corrected branch destination value.
 193  *
 194  * The original INSN location was REAL_PC, it actually
 195  * executed at PC and produced destination address NPC.
 196  */
 197 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 198                                                unsigned long pc,
 199                                                unsigned long npc)
 200 {
 201         /* Branch not taken, no mods necessary.  */
 202         if (npc == pc + 0x4UL)
 203                 return real_pc + 0x4UL;
 204
 205         /* The three cases are call, branch w/prediction,
 206          * and traditional branch.
 207          */
 208         if ((insn & 0xc0000000) == 0x40000000 ||
 209             (insn & 0xc1c00000) == 0x00400000 ||
 210             (insn & 0xc1c00000) == 0x00800000) {
 211                 /* The instruction did all the work for us
 212                  * already, just apply the offset to the correct
 213                  * instruction location.
 214                  */
 215                 return (real_pc + (npc - pc));
 216         }
 217
 218         return real_pc + 0x4UL;
 219 }
 220
 221 /* If INSN is an instruction which writes it's PC location
 222  * into a destination register, fix that up.
 223  */
 224 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 225                                   unsigned long real_pc)
 226 {
 227         unsigned long *slot = NULL;
 228
 229         /* Simplest cast is call, which always uses %o7 */
 230         if ((insn & 0xc0000000) == 0x40000000) {
 231                 slot = &regs->u_regs[UREG_I7];
 232         }
 233
 234         /* Jmpl encodes the register inside of the opcode */
 235         if ((insn & 0xc1f80000) == 0x81c00000) {
 236                 unsigned long rd = ((insn >> 25) & 0x1f);
 237
 238                 if (rd <= 15) {
 239                         slot = &regs->u_regs[rd];
 240                 } else {
 241                         /* Hard case, it goes onto the stack. */
 242                         flushw_all();
 243
 244                         rd -= 16;
 245                         slot = (unsigned long *)
 246                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 247                         slot += rd;
 248                 }
 249         }
 250         if (slot != NULL)
 251                 *slot = real_pc;
 252 }
 253
 254 /*
 255  * Called after single-stepping.  p->addr is the address of the
 256  * instruction whose first byte has been replaced by the breakpoint
 257  * instruction.  To avoid the SMP problems that can occur when we
 258  * temporarily put back the original opcode to single-step, we
 259  * single-stepped a copy of the instruction.  The address of this
 260  * copy is p->ainsn.insn.
 261  *
 262  * This function prepares to return from the post-single-step
 263  * breakpoint trap.
 264  */
 265 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 266 {
 267         u32 insn = p->ainsn.insn[0];
 268
 269         regs->tpc = current_kprobe_orig_tnpc;
 270         regs->tnpc = relbranch_fixup(insn,
 271                                      (unsigned long) p->addr,
 272                                      (unsigned long) &p->ainsn.insn[0],
 273                                      regs->tnpc);
 274         retpc_fixup(regs, insn, (unsigned long) p->addr);
 275
 276         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 277                         current_kprobe_orig_tstate_pil);
 278 }
 279
 280 static inline int post_kprobe_handler(struct pt_regs *regs)
 281 {
 282         if (!kprobe_running())
 283                 return 0;
 284
 285         if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
 286                 kprobe_status = KPROBE_HIT_SSDONE;
 287                 current_kprobe->post_handler(current_kprobe, regs, 0);
 288         }
 289
 290         resume_execution(current_kprobe, regs);
 291
 292         /*Restore back the original saved kprobes variables and continue. */
 293         if (kprobe_status == KPROBE_REENTER) {
 294                 restore_previous_kprobe();
 295                 goto out;
 296         }
 297         unlock_kprobes();
 298 out:
 299         preempt_enable_no_resched();
 300
 301         return 1;
 302 }
 303
 304 /* Interrupts disabled, kprobe_lock held. */
 305 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 306 {
 307         if (current_kprobe->fault_handler
 308             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
 309                 return 1;
 310
 311         if (kprobe_status & KPROBE_HIT_SS) {
 312                 resume_execution(current_kprobe, regs);
 313
 314                 unlock_kprobes();
 315                 preempt_enable_no_resched();
 316         }
 317         return 0;
 318 }
 319
 320 /*
 321  * Wrapper routine to for handling exceptions.
 322  */
 323 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 324                                        unsigned long val, void *data)
 325 {
 326         struct die_args *args = (struct die_args *)data;
 327         int ret = NOTIFY_DONE;
 328
 329         preempt_disable();
 330         switch (val) {
 331         case DIE_DEBUG:
 332                 if (kprobe_handler(args->regs))
 333                         ret = NOTIFY_STOP;
 334                 break;
 335         case DIE_DEBUG_2:
 336                 if (post_kprobe_handler(args->regs))
 337                         ret = NOTIFY_STOP;
 338                 break;
 339         case DIE_GPF:
 340         case DIE_PAGE_FAULT:
 341                 if (kprobe_running() &&
 342                     kprobe_fault_handler(args->regs, args->trapnr))
 343                         ret = NOTIFY_STOP;
 344                 break;
 345         default:
 346                 break;
 347         }
 348         preempt_enable();
 349         return ret;
 350 }
 351
 352 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 353                                       struct pt_regs *regs)
 354 {
 355         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 356
 357         if (user_mode(regs)) {
 358                 local_irq_enable();
 359                 bad_trap(regs, trap_level);
 360                 return;
 361         }
 362
 363         /* trap_level == 0x170 --> ta 0x70
 364          * trap_level == 0x171 --> ta 0x71
 365          */
 366         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 367                        (trap_level == 0x170) ? "debug" : "debug_2",
 368                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 369                 bad_trap(regs, trap_level);
 370 }
 371
 372 /* Jprobes support.  */
 373 static struct pt_regs jprobe_saved_regs;
 374 static struct pt_regs *jprobe_saved_regs_location;
 375 static struct sparc_stackf jprobe_saved_stack;
 376
 377 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 378 {
 379         struct jprobe *jp = container_of(p, struct jprobe, kp);
 380
 381         jprobe_saved_regs_location = regs;
 382         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
 383
 384         /* Save a whole stack frame, this gets arguments
 385          * pushed onto the stack after using up all the
 386          * arg registers.
 387          */
 388         memcpy(&jprobe_saved_stack,
 389                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 390                sizeof(jprobe_saved_stack));
 391
 392         regs->tpc  = (unsigned long) jp->entry;
 393         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 394         regs->tstate |= TSTATE_PIL;
 395
 396         return 1;
 397 }
 398
 399 void __kprobes jprobe_return(void)
 400 {
 401         __asm__ __volatile__(
 402                 ".globl jprobe_return_trap_instruction\n"
 403 "jprobe_return_trap_instruction:\n\t"
 404                 "ta 0x70");
 405 }
 406
 407 extern void jprobe_return_trap_instruction(void);
 408
 409 extern void __show_regs(struct pt_regs * regs);
 410
 411 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 412 {
 413         u32 *addr = (u32 *) regs->tpc;
 414
 415         if (addr == (u32 *) jprobe_return_trap_instruction) {
 416                 if (jprobe_saved_regs_location != regs) {
 417                         printk("JPROBE: Current regs (%p) does not match "
 418                                "saved regs (%p).\n",
 419                                regs, jprobe_saved_regs_location);
 420                         printk("JPROBE: Saved registers\n");
 421                         __show_regs(jprobe_saved_regs_location);
 422                         printk("JPROBE: Current registers\n");
 423                         __show_regs(regs);
 424                         BUG();
 425                 }
 426                 /* Restore old register state.  Do pt_regs
 427                  * first so that UREG_FP is the original one for
 428                  * the stack frame restore.
 429                  */
 430                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
 431
 432                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 433                        &jprobe_saved_stack,
 434                        sizeof(jprobe_saved_stack));
 435
 436                 return 1;
 437         }
 438         return 0;
 439 }
 440
 441 /* architecture specific initialization */
 442 int arch_init_kprobes(void)
 443 {
 444         return 0;
 445 }