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
  12 /* We do not have hardware single-stepping on sparc64.
  13  * So we implement software single-stepping with breakpoint
  14  * traps.  The top-level scheme is similar to that used
  15  * in the x86 kprobes implementation.
  16  *
  17  * In the kprobe->ainsn.insn[] array we store the original
  18  * instruction at index zero and a break instruction at
  19  * index one.
  20  *
  21  * When we hit a kprobe we:
  22  * - Run the pre-handler
  23  * - Remember "regs->tnpc" and interrupt level stored in
  24  *   "regs->tstate" so we can restore them later
  25  * - Disable PIL interrupts
  26  * - Set regs->tpc to point to kprobe->ainsn.insn[0]
  27  * - Set regs->tnpc to point to kprobe->ainsn.insn[1]
  28  * - Mark that we are actively in a kprobe
  29  *
  30  * At this point we wait for the second breakpoint at
  31  * kprobe->ainsn.insn[1] to hit.  When it does we:
  32  * - Run the post-handler
  33  * - Set regs->tpc to "remembered" regs->tnpc stored above,
  34  *   restore the PIL interrupt level in "regs->tstate" as well
  35  * - Make any adjustments necessary to regs->tnpc in order
  36  *   to handle relative branches correctly.  See below.
  37  * - Mark that we are no longer actively in a kprobe.
  38  */
  39
  40 int arch_prepare_kprobe(struct kprobe *p)
  41 {
  42         return 0;
  43 }
  44
  45 void arch_copy_kprobe(struct kprobe *p)
  46 {
  47         p->ainsn.insn[0] = *p->addr;
  48         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  49         p->opcode = *p->addr;
  50 }
  51
  52 void arch_arm_kprobe(struct kprobe *p)
  53 {
  54         *p->addr = BREAKPOINT_INSTRUCTION;
  55         flushi(p->addr);
  56 }
  57
  58 void arch_disarm_kprobe(struct kprobe *p)
  59 {
  60         *p->addr = p->opcode;
  61         flushi(p->addr);
  62 }
  63
  64 void arch_remove_kprobe(struct kprobe *p)
  65 {
  66 }
  67
  68 static struct kprobe *current_kprobe;
  69 static unsigned long current_kprobe_orig_tnpc;
  70 static unsigned long current_kprobe_orig_tstate_pil;
  71 static unsigned int kprobe_status;
  72 static struct kprobe *kprobe_prev;
  73 static unsigned long kprobe_orig_tnpc_prev;
  74 static unsigned long kprobe_orig_tstate_pil_prev;
  75 static unsigned int kprobe_status_prev;
  76
  77 static inline void save_previous_kprobe(void)
  78 {
  79         kprobe_status_prev = kprobe_status;
  80         kprobe_orig_tnpc_prev = current_kprobe_orig_tnpc;
  81         kprobe_orig_tstate_pil_prev = current_kprobe_orig_tstate_pil;
  82         kprobe_prev = current_kprobe;
  83 }
  84
  85 static inline void restore_previous_kprobe(void)
  86 {
  87         kprobe_status = kprobe_status_prev;
  88         current_kprobe_orig_tnpc = kprobe_orig_tnpc_prev;
  89         current_kprobe_orig_tstate_pil = kprobe_orig_tstate_pil_prev;
  90         current_kprobe = kprobe_prev;
  91 }
  92
  93 static inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs)
  94 {
  95         current_kprobe_orig_tnpc = regs->tnpc;
  96         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  97         current_kprobe = p;
  98 }
  99
 100 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 101 {
 102         regs->tstate |= TSTATE_PIL;
 103
 104         /*single step inline, if it a breakpoint instruction*/
 105         if (p->opcode == BREAKPOINT_INSTRUCTION) {
 106                 regs->tpc = (unsigned long) p->addr;
 107                 regs->tnpc = current_kprobe_orig_tnpc;
 108         } else {
 109                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
 110                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
 111         }
 112 }
 113
 114 static int kprobe_handler(struct pt_regs *regs)
 115 {
 116         struct kprobe *p;
 117         void *addr = (void *) regs->tpc;
 118         int ret = 0;
 119
 120         preempt_disable();
 121
 122         if (kprobe_running()) {
 123                 /* We *are* holding lock here, so this is safe.
 124                  * Disarm the probe we just hit, and ignore it.
 125                  */
 126                 p = get_kprobe(addr);
 127                 if (p) {
 128                         if (kprobe_status == KPROBE_HIT_SS) {
 129                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 130                                         current_kprobe_orig_tstate_pil);
 131                                 unlock_kprobes();
 132                                 goto no_kprobe;
 133                         }
 134                         /* We have reentered the kprobe_handler(), since
 135                          * another probe was hit while within the handler.
 136                          * We here save the original kprobes variables and
 137                          * just single step on the instruction of the new probe
 138                          * without calling any user handlers.
 139                          */
 140                         save_previous_kprobe();
 141                         set_current_kprobe(p, regs);
 142                         p->nmissed++;
 143                         kprobe_status = KPROBE_REENTER;
 144                         prepare_singlestep(p, regs);
 145                         return 1;
 146                 } else {
 147                         p = current_kprobe;
 148                         if (p->break_handler && p->break_handler(p, regs))
 149                                 goto ss_probe;
 150                 }
 151                 /* If it's not ours, can't be delete race, (we hold lock). */
 152                 goto no_kprobe;
 153         }
 154
 155         lock_kprobes();
 156         p = get_kprobe(addr);
 157         if (!p) {
 158                 unlock_kprobes();
 159                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 160                         /*
 161                          * The breakpoint instruction was removed right
 162                          * after we hit it.  Another cpu has removed
 163                          * either a probepoint or a debugger breakpoint
 164                          * at this address.  In either case, no further
 165                          * handling of this interrupt is appropriate.
 166                          */
 167                         ret = 1;
 168                 }
 169                 /* Not one of ours: let kernel handle it */
 170                 goto no_kprobe;
 171         }
 172
 173         set_current_kprobe(p, regs);
 174         kprobe_status = KPROBE_HIT_ACTIVE;
 175         if (p->pre_handler && p->pre_handler(p, regs))
 176                 return 1;
 177
 178 ss_probe:
 179         prepare_singlestep(p, regs);
 180         kprobe_status = KPROBE_HIT_SS;
 181         return 1;
 182
 183 no_kprobe:
 184         preempt_enable_no_resched();
 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 relbranch_fixup(u32 insn, unsigned long real_pc,
 195                                      unsigned long pc, unsigned long npc)
 196 {
 197         /* Branch not taken, no mods necessary.  */
 198         if (npc == pc + 0x4UL)
 199                 return real_pc + 0x4UL;
 200
 201         /* The three cases are call, branch w/prediction,
 202          * and traditional branch.
 203          */
 204         if ((insn & 0xc0000000) == 0x40000000 ||
 205             (insn & 0xc1c00000) == 0x00400000 ||
 206             (insn & 0xc1c00000) == 0x00800000) {
 207                 /* The instruction did all the work for us
 208                  * already, just apply the offset to the correct
 209                  * instruction location.
 210                  */
 211                 return (real_pc + (npc - pc));
 212         }
 213
 214         return real_pc + 0x4UL;
 215 }
 216
 217 /* If INSN is an instruction which writes it's PC location
 218  * into a destination register, fix that up.
 219  */
 220 static void retpc_fixup(struct pt_regs *regs, u32 insn, unsigned long real_pc)
 221 {
 222         unsigned long *slot = NULL;
 223
 224         /* Simplest cast is call, which always uses %o7 */
 225         if ((insn & 0xc0000000) == 0x40000000) {
 226                 slot = &regs->u_regs[UREG_I7];
 227         }
 228
 229         /* Jmpl encodes the register inside of the opcode */
 230         if ((insn & 0xc1f80000) == 0x81c00000) {
 231                 unsigned long rd = ((insn >> 25) & 0x1f);
 232
 233                 if (rd <= 15) {
 234                         slot = &regs->u_regs[rd];
 235                 } else {
 236                         /* Hard case, it goes onto the stack. */
 237                         flushw_all();
 238
 239                         rd -= 16;
 240                         slot = (unsigned long *)
 241                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 242                         slot += rd;
 243                 }
 244         }
 245         if (slot != NULL)
 246                 *slot = real_pc;
 247 }
 248
 249 /*
 250  * Called after single-stepping.  p->addr is the address of the
 251  * instruction whose first byte has been replaced by the breakpoint
 252  * instruction.  To avoid the SMP problems that can occur when we
 253  * temporarily put back the original opcode to single-step, we
 254  * single-stepped a copy of the instruction.  The address of this
 255  * copy is p->ainsn.insn.
 256  *
 257  * This function prepares to return from the post-single-step
 258  * breakpoint trap.
 259  */
 260 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 261 {
 262         u32 insn = p->ainsn.insn[0];
 263
 264         regs->tpc = current_kprobe_orig_tnpc;
 265         regs->tnpc = relbranch_fixup(insn,
 266                                      (unsigned long) p->addr,
 267                                      (unsigned long) &p->ainsn.insn[0],
 268                                      regs->tnpc);
 269         retpc_fixup(regs, insn, (unsigned long) p->addr);
 270
 271         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 272                         current_kprobe_orig_tstate_pil);
 273 }
 274
 275 static inline int post_kprobe_handler(struct pt_regs *regs)
 276 {
 277         if (!kprobe_running())
 278                 return 0;
 279
 280         if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
 281                 kprobe_status = KPROBE_HIT_SSDONE;
 282                 current_kprobe->post_handler(current_kprobe, regs, 0);
 283         }
 284
 285         resume_execution(current_kprobe, regs);
 286
 287         /*Restore back the original saved kprobes variables and continue. */
 288         if (kprobe_status == KPROBE_REENTER) {
 289                 restore_previous_kprobe();
 290                 goto out;
 291         }
 292         unlock_kprobes();
 293 out:
 294         preempt_enable_no_resched();
 295
 296         return 1;
 297 }
 298
 299 /* Interrupts disabled, kprobe_lock held. */
 300 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 301 {
 302         if (current_kprobe->fault_handler
 303             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
 304                 return 1;
 305
 306         if (kprobe_status & KPROBE_HIT_SS) {
 307                 resume_execution(current_kprobe, regs);
 308
 309                 unlock_kprobes();
 310                 preempt_enable_no_resched();
 311         }
 312         return 0;
 313 }
 314
 315 /*
 316  * Wrapper routine to for handling exceptions.
 317  */
 318 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
 319                              void *data)
 320 {
 321         struct die_args *args = (struct die_args *)data;
 322         switch (val) {
 323         case DIE_DEBUG:
 324                 if (kprobe_handler(args->regs))
 325                         return NOTIFY_STOP;
 326                 break;
 327         case DIE_DEBUG_2:
 328                 if (post_kprobe_handler(args->regs))
 329                         return NOTIFY_STOP;
 330                 break;
 331         case DIE_GPF:
 332                 if (kprobe_running() &&
 333                     kprobe_fault_handler(args->regs, args->trapnr))
 334                         return NOTIFY_STOP;
 335                 break;
 336         case DIE_PAGE_FAULT:
 337                 if (kprobe_running() &&
 338                     kprobe_fault_handler(args->regs, args->trapnr))
 339                         return NOTIFY_STOP;
 340                 break;
 341         default:
 342                 break;
 343         }
 344         return NOTIFY_DONE;
 345 }
 346
 347 asmlinkage void kprobe_trap(unsigned long trap_level, struct pt_regs *regs)
 348 {
 349         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 350
 351         if (user_mode(regs)) {
 352                 local_irq_enable();
 353                 bad_trap(regs, trap_level);
 354                 return;
 355         }
 356
 357         /* trap_level == 0x170 --> ta 0x70
 358          * trap_level == 0x171 --> ta 0x71
 359          */
 360         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 361                        (trap_level == 0x170) ? "debug" : "debug_2",
 362                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 363                 bad_trap(regs, trap_level);
 364 }
 365
 366 /* Jprobes support.  */
 367 static struct pt_regs jprobe_saved_regs;
 368 static struct pt_regs *jprobe_saved_regs_location;
 369 static struct sparc_stackf jprobe_saved_stack;
 370
 371 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 372 {
 373         struct jprobe *jp = container_of(p, struct jprobe, kp);
 374
 375         jprobe_saved_regs_location = regs;
 376         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
 377
 378         /* Save a whole stack frame, this gets arguments
 379          * pushed onto the stack after using up all the
 380          * arg registers.
 381          */
 382         memcpy(&jprobe_saved_stack,
 383                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 384                sizeof(jprobe_saved_stack));
 385
 386         regs->tpc  = (unsigned long) jp->entry;
 387         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 388         regs->tstate |= TSTATE_PIL;
 389
 390         return 1;
 391 }
 392
 393 void jprobe_return(void)
 394 {
 395         preempt_enable_no_resched();
 396         __asm__ __volatile__(
 397                 ".globl jprobe_return_trap_instruction\n"
 398 "jprobe_return_trap_instruction:\n\t"
 399                 "ta 0x70");
 400 }
 401
 402 extern void jprobe_return_trap_instruction(void);
 403
 404 extern void __show_regs(struct pt_regs * regs);
 405
 406 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 407 {
 408         u32 *addr = (u32 *) regs->tpc;
 409
 410         if (addr == (u32 *) jprobe_return_trap_instruction) {
 411                 if (jprobe_saved_regs_location != regs) {
 412                         printk("JPROBE: Current regs (%p) does not match "
 413                                "saved regs (%p).\n",
 414                                regs, jprobe_saved_regs_location);
 415                         printk("JPROBE: Saved registers\n");
 416                         __show_regs(jprobe_saved_regs_location);
 417                         printk("JPROBE: Current registers\n");
 418                         __show_regs(regs);
 419                         BUG();
 420                 }
 421                 /* Restore old register state.  Do pt_regs
 422                  * first so that UREG_FP is the original one for
 423                  * the stack frame restore.
 424                  */
 425                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
 426
 427                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 428                        &jprobe_saved_stack,
 429                        sizeof(jprobe_saved_stack));
 430
 431                 return 1;
 432         }
 433         return 0;
 434 }
 435
 436 /* architecture specific initialization */
 437 int arch_init_kprobes(void)
 438 {
 439         return 0;
 440 }