err.no Git - linux-2.6/blob - 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 /* kprobe_status settings */
  69 #define KPROBE_HIT_ACTIVE       0x00000001
  70 #define KPROBE_HIT_SS           0x00000002
  71
  72 static struct kprobe *current_kprobe;
  73 static unsigned long current_kprobe_orig_tnpc;
  74 static unsigned long current_kprobe_orig_tstate_pil;
  75 static unsigned int kprobe_status;
  76
  77 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
  78 {
  79         current_kprobe_orig_tnpc = regs->tnpc;
  80         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  81         regs->tstate |= TSTATE_PIL;
  82
  83         /*single step inline, if it a breakpoint instruction*/
  84         if (p->opcode == BREAKPOINT_INSTRUCTION) {
  85                 regs->tpc = (unsigned long) p->addr;
  86                 regs->tnpc = current_kprobe_orig_tnpc;
  87         } else {
  88                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
  89                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
  90         }
  91 }
  92
  93 static int kprobe_handler(struct pt_regs *regs)
  94 {
  95         struct kprobe *p;
  96         void *addr = (void *) regs->tpc;
  97         int ret = 0;
  98
  99         preempt_disable();
 100
 101         if (kprobe_running()) {
 102                 /* We *are* holding lock here, so this is safe.
 103                  * Disarm the probe we just hit, and ignore it.
 104                  */
 105                 p = get_kprobe(addr);
 106                 if (p) {
 107                         if (kprobe_status == KPROBE_HIT_SS) {
 108                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 109                                         current_kprobe_orig_tstate_pil);
 110                                 unlock_kprobes();
 111                                 goto no_kprobe;
 112                         }
 113                         arch_disarm_kprobe(p);
 114                         regs->tpc = (unsigned long) p->addr;
 115                         regs->tnpc = current_kprobe_orig_tnpc;
 116                         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 117                                         current_kprobe_orig_tstate_pil);
 118                         ret = 1;
 119                 } else {
 120                         p = current_kprobe;
 121                         if (p->break_handler && p->break_handler(p, regs))
 122                                 goto ss_probe;
 123                 }
 124                 /* If it's not ours, can't be delete race, (we hold lock). */
 125                 goto no_kprobe;
 126         }
 127
 128         lock_kprobes();
 129         p = get_kprobe(addr);
 130         if (!p) {
 131                 unlock_kprobes();
 132                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 133                         /*
 134                          * The breakpoint instruction was removed right
 135                          * after we hit it.  Another cpu has removed
 136                          * either a probepoint or a debugger breakpoint
 137                          * at this address.  In either case, no further
 138                          * handling of this interrupt is appropriate.
 139                          */
 140                         ret = 1;
 141                 }
 142                 /* Not one of ours: let kernel handle it */
 143                 goto no_kprobe;
 144         }
 145
 146         kprobe_status = KPROBE_HIT_ACTIVE;
 147         current_kprobe = p;
 148         if (p->pre_handler && p->pre_handler(p, regs))
 149                 return 1;
 150
 151 ss_probe:
 152         prepare_singlestep(p, regs);
 153         kprobe_status = KPROBE_HIT_SS;
 154         return 1;
 155
 156 no_kprobe:
 157         preempt_enable_no_resched();
 158         return ret;
 159 }
 160
 161 /* If INSN is a relative control transfer instruction,
 162  * return the corrected branch destination value.
 163  *
 164  * The original INSN location was REAL_PC, it actually
 165  * executed at PC and produced destination address NPC.
 166  */
 167 static unsigned long relbranch_fixup(u32 insn, unsigned long real_pc,
 168                                      unsigned long pc, unsigned long npc)
 169 {
 170         /* Branch not taken, no mods necessary.  */
 171         if (npc == pc + 0x4UL)
 172                 return real_pc + 0x4UL;
 173
 174         /* The three cases are call, branch w/prediction,
 175          * and traditional branch.
 176          */
 177         if ((insn & 0xc0000000) == 0x40000000 ||
 178             (insn & 0xc1c00000) == 0x00400000 ||
 179             (insn & 0xc1c00000) == 0x00800000) {
 180                 /* The instruction did all the work for us
 181                  * already, just apply the offset to the correct
 182                  * instruction location.
 183                  */
 184                 return (real_pc + (npc - pc));
 185         }
 186
 187         return real_pc + 0x4UL;
 188 }
 189
 190 /* If INSN is an instruction which writes it's PC location
 191  * into a destination register, fix that up.
 192  */
 193 static void retpc_fixup(struct pt_regs *regs, u32 insn, unsigned long real_pc)
 194 {
 195         unsigned long *slot = NULL;
 196
 197         /* Simplest cast is call, which always uses %o7 */
 198         if ((insn & 0xc0000000) == 0x40000000) {
 199                 slot = &regs->u_regs[UREG_I7];
 200         }
 201
 202         /* Jmpl encodes the register inside of the opcode */
 203         if ((insn & 0xc1f80000) == 0x81c00000) {
 204                 unsigned long rd = ((insn >> 25) & 0x1f);
 205
 206                 if (rd <= 15) {
 207                         slot = &regs->u_regs[rd];
 208                 } else {
 209                         /* Hard case, it goes onto the stack. */
 210                         flushw_all();
 211
 212                         rd -= 16;
 213                         slot = (unsigned long *)
 214                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 215                         slot += rd;
 216                 }
 217         }
 218         if (slot != NULL)
 219                 *slot = real_pc;
 220 }
 221
 222 /*
 223  * Called after single-stepping.  p->addr is the address of the
 224  * instruction whose first byte has been replaced by the breakpoint
 225  * instruction.  To avoid the SMP problems that can occur when we
 226  * temporarily put back the original opcode to single-step, we
 227  * single-stepped a copy of the instruction.  The address of this
 228  * copy is p->ainsn.insn.
 229  *
 230  * This function prepares to return from the post-single-step
 231  * breakpoint trap.
 232  */
 233 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 234 {
 235         u32 insn = p->ainsn.insn[0];
 236
 237         regs->tpc = current_kprobe_orig_tnpc;
 238         regs->tnpc = relbranch_fixup(insn,
 239                                      (unsigned long) p->addr,
 240                                      (unsigned long) &p->ainsn.insn[0],
 241                                      regs->tnpc);
 242         retpc_fixup(regs, insn, (unsigned long) p->addr);
 243
 244         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 245                         current_kprobe_orig_tstate_pil);
 246 }
 247
 248 static inline int post_kprobe_handler(struct pt_regs *regs)
 249 {
 250         if (!kprobe_running())
 251                 return 0;
 252
 253         if (current_kprobe->post_handler)
 254                 current_kprobe->post_handler(current_kprobe, regs, 0);
 255
 256         resume_execution(current_kprobe, regs);
 257
 258         unlock_kprobes();
 259         preempt_enable_no_resched();
 260
 261         return 1;
 262 }
 263
 264 /* Interrupts disabled, kprobe_lock held. */
 265 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 266 {
 267         if (current_kprobe->fault_handler
 268             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
 269                 return 1;
 270
 271         if (kprobe_status & KPROBE_HIT_SS) {
 272                 resume_execution(current_kprobe, regs);
 273
 274                 unlock_kprobes();
 275                 preempt_enable_no_resched();
 276         }
 277         return 0;
 278 }
 279
 280 /*
 281  * Wrapper routine to for handling exceptions.
 282  */
 283 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
 284                              void *data)
 285 {
 286         struct die_args *args = (struct die_args *)data;
 287         switch (val) {
 288         case DIE_DEBUG:
 289                 if (kprobe_handler(args->regs))
 290                         return NOTIFY_STOP;
 291                 break;
 292         case DIE_DEBUG_2:
 293                 if (post_kprobe_handler(args->regs))
 294                         return NOTIFY_STOP;
 295                 break;
 296         case DIE_GPF:
 297                 if (kprobe_running() &&
 298                     kprobe_fault_handler(args->regs, args->trapnr))
 299                         return NOTIFY_STOP;
 300                 break;
 301         case DIE_PAGE_FAULT:
 302                 if (kprobe_running() &&
 303                     kprobe_fault_handler(args->regs, args->trapnr))
 304                         return NOTIFY_STOP;
 305                 break;
 306         default:
 307                 break;
 308         }
 309         return NOTIFY_DONE;
 310 }
 311
 312 asmlinkage void kprobe_trap(unsigned long trap_level, struct pt_regs *regs)
 313 {
 314         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 315
 316         if (user_mode(regs)) {
 317                 local_irq_enable();
 318                 bad_trap(regs, trap_level);
 319                 return;
 320         }
 321
 322         /* trap_level == 0x170 --> ta 0x70
 323          * trap_level == 0x171 --> ta 0x71
 324          */
 325         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 326                        (trap_level == 0x170) ? "debug" : "debug_2",
 327                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 328                 bad_trap(regs, trap_level);
 329 }
 330
 331 /* Jprobes support.  */
 332 static struct pt_regs jprobe_saved_regs;
 333 static struct pt_regs *jprobe_saved_regs_location;
 334 static struct sparc_stackf jprobe_saved_stack;
 335
 336 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 337 {
 338         struct jprobe *jp = container_of(p, struct jprobe, kp);
 339
 340         jprobe_saved_regs_location = regs;
 341         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
 342
 343         /* Save a whole stack frame, this gets arguments
 344          * pushed onto the stack after using up all the
 345          * arg registers.
 346          */
 347         memcpy(&jprobe_saved_stack,
 348                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 349                sizeof(jprobe_saved_stack));
 350
 351         regs->tpc  = (unsigned long) jp->entry;
 352         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 353         regs->tstate |= TSTATE_PIL;
 354
 355         return 1;
 356 }
 357
 358 void jprobe_return(void)
 359 {
 360         preempt_enable_no_resched();
 361         __asm__ __volatile__(
 362                 ".globl jprobe_return_trap_instruction\n"
 363 "jprobe_return_trap_instruction:\n\t"
 364                 "ta 0x70");
 365 }
 366
 367 extern void jprobe_return_trap_instruction(void);
 368
 369 extern void __show_regs(struct pt_regs * regs);
 370
 371 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 372 {
 373         u32 *addr = (u32 *) regs->tpc;
 374
 375         if (addr == (u32 *) jprobe_return_trap_instruction) {
 376                 if (jprobe_saved_regs_location != regs) {
 377                         printk("JPROBE: Current regs (%p) does not match "
 378                                "saved regs (%p).\n",
 379                                regs, jprobe_saved_regs_location);
 380                         printk("JPROBE: Saved registers\n");
 381                         __show_regs(jprobe_saved_regs_location);
 382                         printk("JPROBE: Current registers\n");
 383                         __show_regs(regs);
 384                         BUG();
 385                 }
 386                 /* Restore old register state.  Do pt_regs
 387                  * first so that UREG_FP is the original one for
 388                  * the stack frame restore.
 389                  */
 390                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
 391
 392                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 393                        &jprobe_saved_stack,
 394                        sizeof(jprobe_saved_stack));
 395
 396                 return 1;
 397         }
 398         return 0;
 399 }