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
  10 #include <asm/kdebug.h>
  11 #include <asm/signal.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 arch_prepare_kprobe(struct kprobe *p)
  42 {
  43         return 0;
  44 }
  45
  46 void arch_copy_kprobe(struct kprobe *p)
  47 {
  48         p->ainsn.insn[0] = *p->addr;
  49         p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
  50 }
  51
  52 void arch_remove_kprobe(struct kprobe *p)
  53 {
  54 }
  55
  56 /* kprobe_status settings */
  57 #define KPROBE_HIT_ACTIVE       0x00000001
  58 #define KPROBE_HIT_SS           0x00000002
  59
  60 static struct kprobe *current_kprobe;
  61 static unsigned long current_kprobe_orig_tnpc;
  62 static unsigned long current_kprobe_orig_tstate_pil;
  63 static unsigned int kprobe_status;
  64
  65 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
  66 {
  67         current_kprobe_orig_tnpc = regs->tnpc;
  68         current_kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL);
  69         regs->tstate |= TSTATE_PIL;
  70
  71         /*single step inline, if it a breakpoint instruction*/
  72         if (p->opcode == BREAKPOINT_INSTRUCTION) {
  73                 regs->tpc = (unsigned long) p->addr;
  74                 regs->tnpc = current_kprobe_orig_tnpc;
  75         } else {
  76                 regs->tpc = (unsigned long) &p->ainsn.insn[0];
  77                 regs->tnpc = (unsigned long) &p->ainsn.insn[1];
  78         }
  79 }
  80
  81 static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
  82 {
  83         *p->addr = p->opcode;
  84         flushi(p->addr);
  85
  86         regs->tpc = (unsigned long) p->addr;
  87         regs->tnpc = current_kprobe_orig_tnpc;
  88         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
  89                         current_kprobe_orig_tstate_pil);
  90 }
  91
  92 static int kprobe_handler(struct pt_regs *regs)
  93 {
  94         struct kprobe *p;
  95         void *addr = (void *) regs->tpc;
  96         int ret = 0;
  97
  98         preempt_disable();
  99
 100         if (kprobe_running()) {
 101                 /* We *are* holding lock here, so this is safe.
 102                  * Disarm the probe we just hit, and ignore it.
 103                  */
 104                 p = get_kprobe(addr);
 105                 if (p) {
 106                         if (kprobe_status == KPROBE_HIT_SS) {
 107                                 regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 108                                         current_kprobe_orig_tstate_pil);
 109                                 unlock_kprobes();
 110                                 goto no_kprobe;
 111                         }
 112                         disarm_kprobe(p, regs);
 113                         ret = 1;
 114                 } else {
 115                         p = current_kprobe;
 116                         if (p->break_handler && p->break_handler(p, regs))
 117                                 goto ss_probe;
 118                 }
 119                 /* If it's not ours, can't be delete race, (we hold lock). */
 120                 goto no_kprobe;
 121         }
 122
 123         lock_kprobes();
 124         p = get_kprobe(addr);
 125         if (!p) {
 126                 unlock_kprobes();
 127                 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) {
 128                         /*
 129                          * The breakpoint instruction was removed right
 130                          * after we hit it.  Another cpu has removed
 131                          * either a probepoint or a debugger breakpoint
 132                          * at this address.  In either case, no further
 133                          * handling of this interrupt is appropriate.
 134                          */
 135                         ret = 1;
 136                 }
 137                 /* Not one of ours: let kernel handle it */
 138                 goto no_kprobe;
 139         }
 140
 141         kprobe_status = KPROBE_HIT_ACTIVE;
 142         current_kprobe = p;
 143         if (p->pre_handler && p->pre_handler(p, regs))
 144                 return 1;
 145
 146 ss_probe:
 147         prepare_singlestep(p, regs);
 148         kprobe_status = KPROBE_HIT_SS;
 149         return 1;
 150
 151 no_kprobe:
 152         preempt_enable_no_resched();
 153         return ret;
 154 }
 155
 156 /* If INSN is a relative control transfer instruction,
 157  * return the corrected branch destination value.
 158  *
 159  * The original INSN location was REAL_PC, it actually
 160  * executed at PC and produced destination address NPC.
 161  */
 162 static unsigned long relbranch_fixup(u32 insn, unsigned long real_pc,
 163                                      unsigned long pc, unsigned long npc)
 164 {
 165         /* Branch not taken, no mods necessary.  */
 166         if (npc == pc + 0x4UL)
 167                 return real_pc + 0x4UL;
 168
 169         /* The three cases are call, branch w/prediction,
 170          * and traditional branch.
 171          */
 172         if ((insn & 0xc0000000) == 0x40000000 ||
 173             (insn & 0xc1c00000) == 0x00400000 ||
 174             (insn & 0xc1c00000) == 0x00800000) {
 175                 /* The instruction did all the work for us
 176                  * already, just apply the offset to the correct
 177                  * instruction location.
 178                  */
 179                 return (real_pc + (npc - pc));
 180         }
 181
 182         return real_pc + 0x4UL;
 183 }
 184
 185 /* If INSN is an instruction which writes it's PC location
 186  * into a destination register, fix that up.
 187  */
 188 static void retpc_fixup(struct pt_regs *regs, u32 insn, unsigned long real_pc)
 189 {
 190         unsigned long *slot = NULL;
 191
 192         /* Simplest cast is call, which always uses %o7 */
 193         if ((insn & 0xc0000000) == 0x40000000) {
 194                 slot = &regs->u_regs[UREG_I7];
 195         }
 196
 197         /* Jmpl encodes the register inside of the opcode */
 198         if ((insn & 0xc1f80000) == 0x81c00000) {
 199                 unsigned long rd = ((insn >> 25) & 0x1f);
 200
 201                 if (rd <= 15) {
 202                         slot = &regs->u_regs[rd];
 203                 } else {
 204                         /* Hard case, it goes onto the stack. */
 205                         flushw_all();
 206
 207                         rd -= 16;
 208                         slot = (unsigned long *)
 209                                 (regs->u_regs[UREG_FP] + STACK_BIAS);
 210                         slot += rd;
 211                 }
 212         }
 213         if (slot != NULL)
 214                 *slot = real_pc;
 215 }
 216
 217 /*
 218  * Called after single-stepping.  p->addr is the address of the
 219  * instruction whose first byte has been replaced by the breakpoint
 220  * instruction.  To avoid the SMP problems that can occur when we
 221  * temporarily put back the original opcode to single-step, we
 222  * single-stepped a copy of the instruction.  The address of this
 223  * copy is p->ainsn.insn.
 224  *
 225  * This function prepares to return from the post-single-step
 226  * breakpoint trap.
 227  */
 228 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 229 {
 230         u32 insn = p->ainsn.insn[0];
 231
 232         regs->tpc = current_kprobe_orig_tnpc;
 233         regs->tnpc = relbranch_fixup(insn,
 234                                      (unsigned long) p->addr,
 235                                      (unsigned long) &p->ainsn.insn[0],
 236                                      regs->tnpc);
 237         retpc_fixup(regs, insn, (unsigned long) p->addr);
 238
 239         regs->tstate = ((regs->tstate & ~TSTATE_PIL) |
 240                         current_kprobe_orig_tstate_pil);
 241 }
 242
 243 static inline int post_kprobe_handler(struct pt_regs *regs)
 244 {
 245         if (!kprobe_running())
 246                 return 0;
 247
 248         if (current_kprobe->post_handler)
 249                 current_kprobe->post_handler(current_kprobe, regs, 0);
 250
 251         resume_execution(current_kprobe, regs);
 252
 253         unlock_kprobes();
 254         preempt_enable_no_resched();
 255
 256         return 1;
 257 }
 258
 259 /* Interrupts disabled, kprobe_lock held. */
 260 static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 261 {
 262         if (current_kprobe->fault_handler
 263             && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
 264                 return 1;
 265
 266         if (kprobe_status & KPROBE_HIT_SS) {
 267                 resume_execution(current_kprobe, regs);
 268
 269                 unlock_kprobes();
 270                 preempt_enable_no_resched();
 271         }
 272         return 0;
 273 }
 274
 275 /*
 276  * Wrapper routine to for handling exceptions.
 277  */
 278 int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
 279                              void *data)
 280 {
 281         struct die_args *args = (struct die_args *)data;
 282         switch (val) {
 283         case DIE_DEBUG:
 284                 if (kprobe_handler(args->regs))
 285                         return NOTIFY_STOP;
 286                 break;
 287         case DIE_DEBUG_2:
 288                 if (post_kprobe_handler(args->regs))
 289                         return NOTIFY_STOP;
 290                 break;
 291         case DIE_GPF:
 292                 if (kprobe_running() &&
 293                     kprobe_fault_handler(args->regs, args->trapnr))
 294                         return NOTIFY_STOP;
 295                 break;
 296         case DIE_PAGE_FAULT:
 297                 if (kprobe_running() &&
 298                     kprobe_fault_handler(args->regs, args->trapnr))
 299                         return NOTIFY_STOP;
 300                 break;
 301         default:
 302                 break;
 303         }
 304         return NOTIFY_DONE;
 305 }
 306
 307 asmlinkage void kprobe_trap(unsigned long trap_level, struct pt_regs *regs)
 308 {
 309         BUG_ON(trap_level != 0x170 && trap_level != 0x171);
 310
 311         if (user_mode(regs)) {
 312                 local_irq_enable();
 313                 bad_trap(regs, trap_level);
 314                 return;
 315         }
 316
 317         /* trap_level == 0x170 --> ta 0x70
 318          * trap_level == 0x171 --> ta 0x71
 319          */
 320         if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2,
 321                        (trap_level == 0x170) ? "debug" : "debug_2",
 322                        regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 323                 bad_trap(regs, trap_level);
 324 }
 325
 326 /* Jprobes support.  */
 327 static struct pt_regs jprobe_saved_regs;
 328 static struct pt_regs *jprobe_saved_regs_location;
 329 static struct sparc_stackf jprobe_saved_stack;
 330
 331 int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 332 {
 333         struct jprobe *jp = container_of(p, struct jprobe, kp);
 334
 335         jprobe_saved_regs_location = regs;
 336         memcpy(&jprobe_saved_regs, regs, sizeof(*regs));
 337
 338         /* Save a whole stack frame, this gets arguments
 339          * pushed onto the stack after using up all the
 340          * arg registers.
 341          */
 342         memcpy(&jprobe_saved_stack,
 343                (char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 344                sizeof(jprobe_saved_stack));
 345
 346         regs->tpc  = (unsigned long) jp->entry;
 347         regs->tnpc = ((unsigned long) jp->entry) + 0x4UL;
 348         regs->tstate |= TSTATE_PIL;
 349
 350         return 1;
 351 }
 352
 353 void jprobe_return(void)
 354 {
 355         preempt_enable_no_resched();
 356         __asm__ __volatile__(
 357                 ".globl jprobe_return_trap_instruction\n"
 358 "jprobe_return_trap_instruction:\n\t"
 359                 "ta 0x70");
 360 }
 361
 362 extern void jprobe_return_trap_instruction(void);
 363
 364 extern void __show_regs(struct pt_regs * regs);
 365
 366 int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 367 {
 368         u32 *addr = (u32 *) regs->tpc;
 369
 370         if (addr == (u32 *) jprobe_return_trap_instruction) {
 371                 if (jprobe_saved_regs_location != regs) {
 372                         printk("JPROBE: Current regs (%p) does not match "
 373                                "saved regs (%p).\n",
 374                                regs, jprobe_saved_regs_location);
 375                         printk("JPROBE: Saved registers\n");
 376                         __show_regs(jprobe_saved_regs_location);
 377                         printk("JPROBE: Current registers\n");
 378                         __show_regs(regs);
 379                         BUG();
 380                 }
 381                 /* Restore old register state.  Do pt_regs
 382                  * first so that UREG_FP is the original one for
 383                  * the stack frame restore.
 384                  */
 385                 memcpy(regs, &jprobe_saved_regs, sizeof(*regs));
 386
 387                 memcpy((char *) (regs->u_regs[UREG_FP] + STACK_BIAS),
 388                        &jprobe_saved_stack,
 389                        sizeof(jprobe_saved_stack));
 390
 391                 return 1;
 392         }
 393         return 0;
 394 }