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         p->ainsn.insn[0] = *p->addr;
  47         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  48         p->opcode = *p->addr;
  49         return 0;
  50 }
  51
  52 void __kprobes arch_arm_kprobe(struct kprobe *p)
  53 {
  54         *p->addr = BREAKPOINT_INSTRUCTION;
  55         flushi(p->addr);
  56 }
  57
  58 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  59 {
  60         *p->addr = p->opcode;
  61         flushi(p->addr);
  62 }
  63
  64 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
  65 {
  66         kcb->prev_kprobe.kp = kprobe_running();
  67         kcb->prev_kprobe.status = kcb->kprobe_status;
  68         kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc;
  69         kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil;
  70 }
  71
  72 static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  73 {
  74         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
  75         kcb->kprobe_status = kcb->prev_kprobe.status;
  76         kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc;
  77         kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil;
  78 }
  79
  80 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
  81                                 struct kprobe_ctlblk *kcb)
  82 {
  83         __get_cpu_var(current_kprobe) = p;
  84         kcb->kprobe_orig_tnpc = regs->tnpc;
  85         kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  86 }
  87
  88 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs,
  89                         struct kprobe_ctlblk *kcb)
  90 {
  91         regs->tstate |= TSTATE_PIL;
  92
  93         /*single step inline, if it a breakpoint instruction*/
  94         if (p->opcode == BREAKPOINT_INSTRUCTION) {
  95                 regs->tpc = (unsigned long) p->addr;
  96                 regs->tnpc = kcb->kprobe_orig_tnpc;
  97         } else {
  98                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
  99                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 100         }
 101 }
 102
 103 static int __kprobes kprobe_handler(struct pt_regs *regs)
 104 {
 105         struct kprobe *p;
 106         void *addr = (void *) regs->tpc;
 107         int ret = 0;
 108         struct kprobe_ctlblk *kcb;
 109
 110         /*
 111          * We don't want to be preempted for the entire
 112          * duration of kprobe processing
 113          */
 114         preempt_disable();
 115         kcb = get_kprobe_ctlblk();
 116
 117         if (kprobe_running()) {
 118                 p = get_kprobe(addr);
 119                 if (p) {
 120                         if (kcb->kprobe_status == KPROBE_HIT_SS) {
 121                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 122                                         kcb->kprobe_orig_tstate_pil);
 123                                 goto no_kprobe;
 124                         }
 125                         /* We have reentered the kprobe_handler(), since
 126                          * another probe was hit while within the handler.
 127                          * We here save the original kprobes variables and
 128                          * just single step on the instruction of the new probe
 129                          * without calling any user handlers.
 130                          */
 131                         save_previous_kprobe(kcb);
 132                         set_current_kprobe(p, regs, kcb);
 133                         kprobes_inc_nmissed_count(p);
 134                         kcb->kprobe_status = KPROBE_REENTER;
 135                         prepare_singlestep(p, regs, kcb);
 136                         return 1;
 137                 } else {
 138                         if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 139                         /* The breakpoint instruction was removed by
 140                          * another cpu right after we hit, no further
 141                          * handling of this interrupt is appropriate
 142                          */
 143                                 ret = 1;
 144                                 goto no_kprobe;
 145                         }
 146                         p = __get_cpu_var(current_kprobe);
 147                         if (p->break_handler && p->break_handler(p, regs))
 148                                 goto ss_probe;
 149                 }
 150                 goto no_kprobe;
 151         }
 152
 153         p = get_kprobe(addr);
 154         if (!p) {
 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         set_current_kprobe(p, regs, kcb);
 170         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 171         if (p->pre_handler && p->pre_handler(p, regs))
 172                 return 1;
 173
 174 ss_probe:
 175         prepare_singlestep(p, regs, kcb);
 176         kcb->kprobe_status = KPROBE_HIT_SS;
 177         return 1;
 178
 179 no_kprobe:
 180         preempt_enable_no_resched();
 181         return ret;
 182 }
 183
 184 /* If INSN is a relative control transfer instruction,
 185  * return the corrected branch destination value.
 186  *
 187  * The original INSN location was REAL_PC, it actually
 188  * executed at PC and produced destination address NPC.
 189  */
 190 static unsigned long __kprobes relbranch_fixup(u32 insn, unsigned long real_pc,
 191                                                unsigned long pc,
 192                                                unsigned long npc)
 193 {
 194         /* Branch not taken, no mods necessary.  */
 195         if (npc == pc + 0x4UL)
 196                 return real_pc + 0x4UL;
 197
 198         /* The three cases are call, branch w/prediction,
 199          * and traditional branch.
 200          */
 201         if ((insn & 0xc0000000) == 0x40000000 ||
 202             (insn & 0xc1c00000) == 0x00400000 ||
 203             (insn & 0xc1c00000) == 0x00800000) {
 204                 /* The instruction did all the work for us
 205                  * already, just apply the offset to the correct
 206                  * instruction location.
 207                  */
 208                 return (real_pc + (npc - pc));
 209         }
 210
 211         return real_pc + 0x4UL;
 212 }
 213
 214 /* If INSN is an instruction which writes it's PC location
 215  * into a destination register, fix that up.
 216  */
 217 static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn,
 218                                   unsigned long real_pc)
 219 {
 220         unsigned long *slot = NULL;
 221
 222         /* Simplest cast is call, which always uses %o7 */
 223         if ((insn & 0xc0000000) == 0x40000000) {
 224                 slot = &regs->u_regs[UREG_I7];
 225         }
 226
 227         /* Jmpl encodes the register inside of the opcode */
 228         if ((insn & 0xc1f80000) == 0x81c00000) {
 229                 unsigned long rd = ((insn >> 25) & 0x1f);
 230
 231                 if (rd <= 15) {
 232                         slot = &regs->u_regs[rd];
 233                 } else {
 234                         /* Hard case, it goes onto the stack. */
 235                         flushw_all();
 236
 237                         rd -= 16;
 238                         slot = (unsigned long *)
 239                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 240                         slot += rd;
 241                 }
 242         }
 243         if (slot != NULL)
 244                 *slot = real_pc;
 245 }
 246
 247 /*
 248  * Called after single-stepping.  p->addr is the address of the
 249  * instruction whose first byte has been replaced by the breakpoint
 250  * instruction.  To avoid the SMP problems that can occur when we
 251  * temporarily put back the original opcode to single-step, we
 252  * single-stepped a copy of the instruction.  The address of this
 253  * copy is p->ainsn.insn.
 254  *
 255  * This function prepares to return from the post-single-step
 256  * breakpoint trap.
 257  */
 258 static void __kprobes resume_execution(struct kprobe *p,
 259                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 260 {
 261         u32 insn = p->ainsn.insn[0];
 262
 263         regs->tpc = kcb->kprobe_orig_tnpc;
 264         regs->tnpc = relbranch_fixup(insn,
 265                                      (unsigned long) p->addr,
 266                                      (unsigned long) &p->ainsn.insn[0],
 267                                      regs->tnpc);
 268         retpc_fixup(regs, insn, (unsigned long) p->addr);
 269
 270         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 271                         kcb->kprobe_orig_tstate_pil);
 272 }
 273
 274 static inline int post_kprobe_handler(struct pt_regs *regs)
 275 {
 276         struct kprobe *cur = kprobe_running();
 277         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 278
 279         if (!cur)
 280                 return 0;
 281
 282         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 283                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 284                 cur->post_handler(cur, regs, 0);
 285         }
 286
 287         resume_execution(cur, regs, kcb);
 288
 289         /*Restore back the original saved kprobes variables and continue. */
 290         if (kcb->kprobe_status == KPROBE_REENTER) {
 291                 restore_previous_kprobe(kcb);
 292                 goto out;
 293         }
 294         reset_current_kprobe();
 295 out:
 296         preempt_enable_no_resched();
 297
 298         return 1;
 299 }
 300
 301 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 302 {
 303         struct kprobe *cur = kprobe_running();
 304         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 305
 306         if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 307                 return 1;
 308
 309         if (kcb->kprobe_status & KPROBE_HIT_SS) {
 310                 resume_execution(cur, regs, kcb);
 311
 312                 reset_current_kprobe();
 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         int ret = NOTIFY_DONE;
 326
 327         switch (val) {
 328         case DIE_DEBUG:
 329                 if (kprobe_handler(args->regs))
 330                         ret = NOTIFY_STOP;
 331                 break;
 332         case DIE_DEBUG_2:
 333                 if (post_kprobe_handler(args->regs))
 334                         ret = NOTIFY_STOP;
 335                 break;
 336         case DIE_GPF:
 337         case DIE_PAGE_FAULT:
 338                 /* kprobe_running() needs smp_processor_id() */
 339                 preempt_disable();
 340                 if (kprobe_running() &&
 341                     kprobe_fault_handler(args->regs, args->trapnr))
 342                         ret = NOTIFY_STOP;
 343                 preempt_enable();
 344                 break;
 345         default:
 346                 break;
 347         }
 348         return ret;
 349 }
 350
 351 asmlinkage void __kprobes kprobe_trap(unsigned long trap_level,
 352                                       struct pt_regs *regs)
 353 {
 354         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 355
 356         if (user_mode(regs)) {
 357                 local_irq_enable();
 358                 bad_trap(regs, trap_level);
 359                 return;
 360         }
 361
 362         /* trap_level == 0x170 --> ta 0x70
 363          * trap_level == 0x171 --> ta 0x71
 364          */
 365         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 366                        (trap_level == 0x170) ? "debug" : "debug_2",
 367                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 368                 bad_trap(regs, trap_level);
 369 }
 370
 371 /* Jprobes support.  */
 372 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 373 {
 374         struct jprobe *jp = container_of(p, struct jprobe, kp);
 375         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 376
 377         kcb->jprobe_saved_regs_location = regs;
 378         memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs));
 379
 380         /* Save a whole stack frame, this gets arguments
 381          * pushed onto the stack after using up all the
 382          * arg registers.
 383          */
 384         memcpy(&(kcb->jprobe_saved_stack),
 385                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 386                sizeof(kcb->jprobe_saved_stack));
 387
 388         regs->tpc  = (unsigned long) jp->entry;
 389         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 390         regs->tstate |= TSTATE_PIL;
 391
 392         return 1;
 393 }
 394
 395 void __kprobes jprobe_return(void)
 396 {
 397         __asm__ __volatile__(
 398                 ".globl jprobe_return_trap_instruction\n"
 399 "jprobe_return_trap_instruction:\n\t"
 400                 "ta 0x70");
 401 }
 402
 403 extern void jprobe_return_trap_instruction(void);
 404
 405 extern void __show_regs(struct pt_regs * regs);
 406
 407 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 408 {
 409         u32 *addr = (u32 *) regs->tpc;
 410         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 411
 412         if (addr == (u32 *) jprobe_return_trap_instruction) {
 413                 if (kcb->jprobe_saved_regs_location != regs) {
 414                         printk("JPROBE: Current regs (%p) does not match "
 415                                "saved regs (%p).\n",
 416                                regs, kcb->jprobe_saved_regs_location);
 417                         printk("JPROBE: Saved registers\n");
 418                         __show_regs(kcb->jprobe_saved_regs_location);
 419                         printk("JPROBE: Current registers\n");
 420                         __show_regs(regs);
 421                         BUG();
 422                 }
 423                 /* Restore old register state.  Do pt_regs
 424                  * first so that UREG_FP is the original one for
 425                  * the stack frame restore.
 426                  */
 427                 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs));
 428
 429                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 430                        &(kcb->jprobe_saved_stack),
 431                        sizeof(kcb->jprobe_saved_stack));
 432
 433                 preempt_enable_no_resched();
 434                 return 1;
 435         }
 436         return 0;
 437 }
 438
 439 /* architecture specific initialization */
 440 int arch_init_kprobes(void)
 441 {
 442         return 0;
 443 }