arch/x86/kernel/kprobes_64.c

   1 /*
   2  *  Kernel Probes (KProbes)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2002, 2004
  19  *
  20  * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
  21  *              Probes initial implementation ( includes contributions from
  22  *              Rusty Russell).
  23  * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
  24  *              interface to access function arguments.
  25  * 2004-Oct     Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
  26  *              <prasanna@in.ibm.com> adapted for x86_64
  27  * 2005-Mar     Roland McGrath <roland@redhat.com>
  28  *              Fixed to handle %rip-relative addressing mode correctly.
  29  * 2005-May     Rusty Lynch <rusty.lynch@intel.com>
  30  *              Added function return probes functionality
  31  */
  32
  33 #include <linux/kprobes.h>
  34 #include <linux/ptrace.h>
  35 #include <linux/string.h>
  36 #include <linux/slab.h>
  37 #include <linux/preempt.h>
  38 #include <linux/module.h>
  39 #include <linux/kdebug.h>
  40
  41 #include <asm/pgtable.h>
  42 #include <asm/uaccess.h>
  43 #include <asm/alternative.h>
  44
  45 void jprobe_return_end(void);
  46 static void __kprobes arch_copy_kprobe(struct kprobe *p);
  47
  48 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  49 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  50
  51 struct kretprobe_blackpoint kretprobe_blacklist[] = {
  52         {"__switch_to", }, /* This function switches only current task, but
  53                               doesn't switch kernel stack.*/
  54         {NULL, NULL}    /* Terminator */
  55 };
  56 const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
  57
  58 /*
  59  * returns non-zero if opcode modifies the interrupt flag.
  60  */
  61 static __always_inline int is_IF_modifier(kprobe_opcode_t *insn)
  62 {
  63         switch (*insn) {
  64         case 0xfa:              /* cli */
  65         case 0xfb:              /* sti */
  66         case 0xcf:              /* iret/iretd */
  67         case 0x9d:              /* popf/popfd */
  68                 return 1;
  69         }
  70
  71         if (*insn  >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
  72                 return 1;
  73         return 0;
  74 }
  75
  76 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  77 {
  78         /* insn: must be on special executable page on x86_64. */
  79         p->ainsn.insn = get_insn_slot();
  80         if (!p->ainsn.insn) {
  81                 return -ENOMEM;
  82         }
  83         arch_copy_kprobe(p);
  84         return 0;
  85 }
  86
  87 /*
  88  * Determine if the instruction uses the %rip-relative addressing mode.
  89  * If it does, return the address of the 32-bit displacement word.
  90  * If not, return null.
  91  */
  92 static s32 __kprobes *is_riprel(u8 *insn)
  93 {
  94 #define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)                \
  95         (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
  96           (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
  97           (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
  98           (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
  99          << (row % 64))
 100         static const u64 onebyte_has_modrm[256 / 64] = {
 101                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
 102                 /*      -------------------------------         */
 103                 W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
 104                 W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
 105                 W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
 106                 W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
 107                 W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
 108                 W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
 109                 W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
 110                 W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
 111                 W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
 112                 W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
 113                 W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
 114                 W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
 115                 W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
 116                 W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
 117                 W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
 118                 W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1)  /* f0 */
 119                 /*      -------------------------------         */
 120                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
 121         };
 122         static const u64 twobyte_has_modrm[256 / 64] = {
 123                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
 124                 /*      -------------------------------         */
 125                 W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
 126                 W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
 127                 W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
 128                 W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
 129                 W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
 130                 W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
 131                 W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
 132                 W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
 133                 W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
 134                 W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
 135                 W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
 136                 W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
 137                 W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
 138                 W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
 139                 W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
 140                 W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0)  /* ff */
 141                 /*      -------------------------------         */
 142                 /*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
 143         };
 144 #undef  W
 145         int need_modrm;
 146
 147         /* Skip legacy instruction prefixes.  */
 148         while (1) {
 149                 switch (*insn) {
 150                 case 0x66:
 151                 case 0x67:
 152                 case 0x2e:
 153                 case 0x3e:
 154                 case 0x26:
 155                 case 0x64:
 156                 case 0x65:
 157                 case 0x36:
 158                 case 0xf0:
 159                 case 0xf3:
 160                 case 0xf2:
 161                         ++insn;
 162                         continue;
 163                 }
 164                 break;
 165         }
 166
 167         /* Skip REX instruction prefix.  */
 168         if ((*insn & 0xf0) == 0x40)
 169                 ++insn;
 170
 171         if (*insn == 0x0f) {    /* Two-byte opcode.  */
 172                 ++insn;
 173                 need_modrm = test_bit(*insn, twobyte_has_modrm);
 174         } else {                /* One-byte opcode.  */
 175                 need_modrm = test_bit(*insn, onebyte_has_modrm);
 176         }
 177
 178         if (need_modrm) {
 179                 u8 modrm = *++insn;
 180                 if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
 181                         /* Displacement follows ModRM byte.  */
 182                         return (s32 *) ++insn;
 183                 }
 184         }
 185
 186         /* No %rip-relative addressing mode here.  */
 187         return NULL;
 188 }
 189
 190 static void __kprobes arch_copy_kprobe(struct kprobe *p)
 191 {
 192         s32 *ripdisp;
 193         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
 194         ripdisp = is_riprel(p->ainsn.insn);
 195         if (ripdisp) {
 196                 /*
 197                  * The copied instruction uses the %rip-relative
 198                  * addressing mode.  Adjust the displacement for the
 199                  * difference between the original location of this
 200                  * instruction and the location of the copy that will
 201                  * actually be run.  The tricky bit here is making sure
 202                  * that the sign extension happens correctly in this
 203                  * calculation, since we need a signed 32-bit result to
 204                  * be sign-extended to 64 bits when it's added to the
 205                  * %rip value and yield the same 64-bit result that the
 206                  * sign-extension of the original signed 32-bit
 207                  * displacement would have given.
 208                  */
 209                 s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
 210                 BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
 211                 *ripdisp = disp;
 212         }
 213         p->opcode = *p->addr;
 214 }
 215
 216 void __kprobes arch_arm_kprobe(struct kprobe *p)
 217 {
 218         text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
 219 }
 220
 221 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 222 {
 223         text_poke(p->addr, &p->opcode, 1);
 224 }
 225
 226 void __kprobes arch_remove_kprobe(struct kprobe *p)
 227 {
 228         mutex_lock(&kprobe_mutex);
 229         free_insn_slot(p->ainsn.insn, 0);
 230         mutex_unlock(&kprobe_mutex);
 231 }
 232
 233 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 234 {
 235         kcb->prev_kprobe.kp = kprobe_running();
 236         kcb->prev_kprobe.status = kcb->kprobe_status;
 237         kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
 238         kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
 239 }
 240
 241 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 242 {
 243         __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 244         kcb->kprobe_status = kcb->prev_kprobe.status;
 245         kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
 246         kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
 247 }
 248
 249 static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 250                                 struct kprobe_ctlblk *kcb)
 251 {
 252         __get_cpu_var(current_kprobe) = p;
 253         kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
 254                 = (regs->eflags & (TF_MASK | IF_MASK));
 255         if (is_IF_modifier(p->ainsn.insn))
 256                 kcb->kprobe_saved_rflags &= ~IF_MASK;
 257 }
 258
 259 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 260 {
 261         regs->eflags |= TF_MASK;
 262         regs->eflags &= ~IF_MASK;
 263         /*single step inline if the instruction is an int3*/
 264         if (p->opcode == BREAKPOINT_INSTRUCTION)
 265                 regs->rip = (unsigned long)p->addr;
 266         else
 267                 regs->rip = (unsigned long)p->ainsn.insn;
 268 }
 269
 270 /* Called with kretprobe_lock held */
 271 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 272                                       struct pt_regs *regs)
 273 {
 274         unsigned long *sara = (unsigned long *)regs->rsp;
 275
 276         ri->ret_addr = (kprobe_opcode_t *) *sara;
 277         /* Replace the return addr with trampoline addr */
 278         *sara = (unsigned long) &kretprobe_trampoline;
 279 }
 280
 281 int __kprobes kprobe_handler(struct pt_regs *regs)
 282 {
 283         struct kprobe *p;
 284         int ret = 0;
 285         kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
 286         struct kprobe_ctlblk *kcb;
 287
 288         /*
 289          * We don't want to be preempted for the entire
 290          * duration of kprobe processing
 291          */
 292         preempt_disable();
 293         kcb = get_kprobe_ctlblk();
 294
 295         /* Check we're not actually recursing */
 296         if (kprobe_running()) {
 297                 p = get_kprobe(addr);
 298                 if (p) {
 299                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
 300                                 *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
 301                                 regs->eflags &= ~TF_MASK;
 302                                 regs->eflags |= kcb->kprobe_saved_rflags;
 303                                 goto no_kprobe;
 304                         } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
 305                                 /* TODO: Provide re-entrancy from
 306                                  * post_kprobes_handler() and avoid exception
 307                                  * stack corruption while single-stepping on
 308                                  * the instruction of the new probe.
 309                                  */
 310                                 arch_disarm_kprobe(p);
 311                                 regs->rip = (unsigned long)p->addr;
 312                                 reset_current_kprobe();
 313                                 ret = 1;
 314                         } else {
 315                                 /* We have reentered the kprobe_handler(), since
 316                                  * another probe was hit while within the
 317                                  * handler. We here save the original kprobe
 318                                  * variables and just single step on instruction
 319                                  * of the new probe without calling any user
 320                                  * handlers.
 321                                  */
 322                                 save_previous_kprobe(kcb);
 323                                 set_current_kprobe(p, regs, kcb);
 324                                 kprobes_inc_nmissed_count(p);
 325                                 prepare_singlestep(p, regs);
 326                                 kcb->kprobe_status = KPROBE_REENTER;
 327                                 return 1;
 328                         }
 329                 } else {
 330                         if (*addr != BREAKPOINT_INSTRUCTION) {
 331                         /* The breakpoint instruction was removed by
 332                          * another cpu right after we hit, no further
 333                          * handling of this interrupt is appropriate
 334                          */
 335                                 regs->rip = (unsigned long)addr;
 336                                 ret = 1;
 337                                 goto no_kprobe;
 338                         }
 339                         p = __get_cpu_var(current_kprobe);
 340                         if (p->break_handler && p->break_handler(p, regs)) {
 341                                 goto ss_probe;
 342                         }
 343                 }
 344                 goto no_kprobe;
 345         }
 346
 347         p = get_kprobe(addr);
 348         if (!p) {
 349                 if (*addr != BREAKPOINT_INSTRUCTION) {
 350                         /*
 351                          * The breakpoint instruction was removed right
 352                          * after we hit it.  Another cpu has removed
 353                          * either a probepoint or a debugger breakpoint
 354                          * at this address.  In either case, no further
 355                          * handling of this interrupt is appropriate.
 356                          * Back up over the (now missing) int3 and run
 357                          * the original instruction.
 358                          */
 359                         regs->rip = (unsigned long)addr;
 360                         ret = 1;
 361                 }
 362                 /* Not one of ours: let kernel handle it */
 363                 goto no_kprobe;
 364         }
 365
 366         set_current_kprobe(p, regs, kcb);
 367         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 368
 369         if (p->pre_handler && p->pre_handler(p, regs))
 370                 /* handler has already set things up, so skip ss setup */
 371                 return 1;
 372
 373 ss_probe:
 374         prepare_singlestep(p, regs);
 375         kcb->kprobe_status = KPROBE_HIT_SS;
 376         return 1;
 377
 378 no_kprobe:
 379         preempt_enable_no_resched();
 380         return ret;
 381 }
 382
 383 /*
 384  * For function-return probes, init_kprobes() establishes a probepoint
 385  * here. When a retprobed function returns, this probe is hit and
 386  * trampoline_probe_handler() runs, calling the kretprobe's handler.
 387  */
 388  void kretprobe_trampoline_holder(void)
 389  {
 390         asm volatile (  ".global kretprobe_trampoline\n"
 391                         "kretprobe_trampoline: \n"
 392                         "nop\n");
 393  }
 394
 395 /*
 396  * Called when we hit the probe point at kretprobe_trampoline
 397  */
 398 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 399 {
 400         struct kretprobe_instance *ri = NULL;
 401         struct hlist_head *head, empty_rp;
 402         struct hlist_node *node, *tmp;
 403         unsigned long flags, orig_ret_address = 0;
 404         unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 405
 406         INIT_HLIST_HEAD(&empty_rp);
 407         spin_lock_irqsave(&kretprobe_lock, flags);
 408         head = kretprobe_inst_table_head(current);
 409
 410         /*
 411          * It is possible to have multiple instances associated with a given
 412          * task either because an multiple functions in the call path
 413          * have a return probe installed on them, and/or more then one return
 414          * return probe was registered for a target function.
 415          *
 416          * We can handle this because:
 417          *     - instances are always inserted at the head of the list
 418          *     - when multiple return probes are registered for the same
 419          *       function, the first instance's ret_addr will point to the
 420          *       real return address, and all the rest will point to
 421          *       kretprobe_trampoline
 422          */
 423         hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 424                 if (ri->task != current)
 425                         /* another task is sharing our hash bucket */
 426                         continue;
 427
 428                 if (ri->rp && ri->rp->handler)
 429                         ri->rp->handler(ri, regs);
 430
 431                 orig_ret_address = (unsigned long)ri->ret_addr;
 432                 recycle_rp_inst(ri, &empty_rp);
 433
 434                 if (orig_ret_address != trampoline_address)
 435                         /*
 436                          * This is the real return address. Any other
 437                          * instances associated with this task are for
 438                          * other calls deeper on the call stack
 439                          */
 440                         break;
 441         }
 442
 443         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 444         regs->rip = orig_ret_address;
 445
 446         reset_current_kprobe();
 447         spin_unlock_irqrestore(&kretprobe_lock, flags);
 448         preempt_enable_no_resched();
 449
 450         hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
 451                 hlist_del(&ri->hlist);
 452                 kfree(ri);
 453         }
 454         /*
 455          * By returning a non-zero value, we are telling
 456          * kprobe_handler() that we don't want the post_handler
 457          * to run (and have re-enabled preemption)
 458          */
 459         return 1;
 460 }
 461
 462 /*
 463  * Called after single-stepping.  p->addr is the address of the
 464  * instruction whose first byte has been replaced by the "int 3"
 465  * instruction.  To avoid the SMP problems that can occur when we
 466  * temporarily put back the original opcode to single-step, we
 467  * single-stepped a copy of the instruction.  The address of this
 468  * copy is p->ainsn.insn.
 469  *
 470  * This function prepares to return from the post-single-step
 471  * interrupt.  We have to fix up the stack as follows:
 472  *
 473  * 0) Except in the case of absolute or indirect jump or call instructions,
 474  * the new rip is relative to the copied instruction.  We need to make
 475  * it relative to the original instruction.
 476  *
 477  * 1) If the single-stepped instruction was pushfl, then the TF and IF
 478  * flags are set in the just-pushed eflags, and may need to be cleared.
 479  *
 480  * 2) If the single-stepped instruction was a call, the return address
 481  * that is atop the stack is the address following the copied instruction.
 482  * We need to make it the address following the original instruction.
 483  */
 484 static void __kprobes resume_execution(struct kprobe *p,
 485                 struct pt_regs *regs, struct kprobe_ctlblk *kcb)
 486 {
 487         unsigned long *tos = (unsigned long *)regs->rsp;
 488         unsigned long next_rip = 0;
 489         unsigned long copy_rip = (unsigned long)p->ainsn.insn;
 490         unsigned long orig_rip = (unsigned long)p->addr;
 491         kprobe_opcode_t *insn = p->ainsn.insn;
 492
 493         /*skip the REX prefix*/
 494         if (*insn >= 0x40 && *insn <= 0x4f)
 495                 insn++;
 496
 497         switch (*insn) {
 498         case 0x9c:              /* pushfl */
 499                 *tos &= ~(TF_MASK | IF_MASK);
 500                 *tos |= kcb->kprobe_old_rflags;
 501                 break;
 502         case 0xc3:              /* ret/lret */
 503         case 0xcb:
 504         case 0xc2:
 505         case 0xca:
 506                 regs->eflags &= ~TF_MASK;
 507                 /* rip is already adjusted, no more changes required*/
 508                 return;
 509         case 0xe8:              /* call relative - Fix return addr */
 510                 *tos = orig_rip + (*tos - copy_rip);
 511                 break;
 512         case 0xff:
 513                 if ((insn[1] & 0x30) == 0x10) {
 514                         /* call absolute, indirect */
 515                         /* Fix return addr; rip is correct. */
 516                         next_rip = regs->rip;
 517                         *tos = orig_rip + (*tos - copy_rip);
 518                 } else if (((insn[1] & 0x31) == 0x20) ||        /* jmp near, absolute indirect */
 519                            ((insn[1] & 0x31) == 0x21)) {        /* jmp far, absolute indirect */
 520                         /* rip is correct. */
 521                         next_rip = regs->rip;
 522                 }
 523                 break;
 524         case 0xea:              /* jmp absolute -- rip is correct */
 525                 next_rip = regs->rip;
 526                 break;
 527         default:
 528                 break;
 529         }
 530
 531         regs->eflags &= ~TF_MASK;
 532         if (next_rip) {
 533                 regs->rip = next_rip;
 534         } else {
 535                 regs->rip = orig_rip + (regs->rip - copy_rip);
 536         }
 537 }
 538
 539 int __kprobes post_kprobe_handler(struct pt_regs *regs)
 540 {
 541         struct kprobe *cur = kprobe_running();
 542         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 543
 544         if (!cur)
 545                 return 0;
 546
 547         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
 548                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 549                 cur->post_handler(cur, regs, 0);
 550         }
 551
 552         resume_execution(cur, regs, kcb);
 553         regs->eflags |= kcb->kprobe_saved_rflags;
 554         trace_hardirqs_fixup_flags(regs->eflags);
 555
 556         /* Restore the original saved kprobes variables and continue. */
 557         if (kcb->kprobe_status == KPROBE_REENTER) {
 558                 restore_previous_kprobe(kcb);
 559                 goto out;
 560         }
 561         reset_current_kprobe();
 562 out:
 563         preempt_enable_no_resched();
 564
 565         /*
 566          * if somebody else is singlestepping across a probe point, eflags
 567          * will have TF set, in which case, continue the remaining processing
 568          * of do_debug, as if this is not a probe hit.
 569          */
 570         if (regs->eflags & TF_MASK)
 571                 return 0;
 572
 573         return 1;
 574 }
 575
 576 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 577 {
 578         struct kprobe *cur = kprobe_running();
 579         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 580         const struct exception_table_entry *fixup;
 581
 582         switch(kcb->kprobe_status) {
 583         case KPROBE_HIT_SS:
 584         case KPROBE_REENTER:
 585                 /*
 586                  * We are here because the instruction being single
 587                  * stepped caused a page fault. We reset the current
 588                  * kprobe and the rip points back to the probe address
 589                  * and allow the page fault handler to continue as a
 590                  * normal page fault.
 591                  */
 592                 regs->rip = (unsigned long)cur->addr;
 593                 regs->eflags |= kcb->kprobe_old_rflags;
 594                 if (kcb->kprobe_status == KPROBE_REENTER)
 595                         restore_previous_kprobe(kcb);
 596                 else
 597                         reset_current_kprobe();
 598                 preempt_enable_no_resched();
 599                 break;
 600         case KPROBE_HIT_ACTIVE:
 601         case KPROBE_HIT_SSDONE:
 602                 /*
 603                  * We increment the nmissed count for accounting,
 604                  * we can also use npre/npostfault count for accouting
 605                  * these specific fault cases.
 606                  */
 607                 kprobes_inc_nmissed_count(cur);
 608
 609                 /*
 610                  * We come here because instructions in the pre/post
 611                  * handler caused the page_fault, this could happen
 612                  * if handler tries to access user space by
 613                  * copy_from_user(), get_user() etc. Let the
 614                  * user-specified handler try to fix it first.
 615                  */
 616                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 617                         return 1;
 618
 619                 /*
 620                  * In case the user-specified fault handler returned
 621                  * zero, try to fix up.
 622                  */
 623                 fixup = search_exception_tables(regs->rip);
 624                 if (fixup) {
 625                         regs->rip = fixup->fixup;
 626                         return 1;
 627                 }
 628
 629                 /*
 630                  * fixup() could not handle it,
 631                  * Let do_page_fault() fix it.
 632                  */
 633                 break;
 634         default:
 635                 break;
 636         }
 637         return 0;
 638 }
 639
 640 /*
 641  * Wrapper routine for handling exceptions.
 642  */
 643 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 644                                        unsigned long val, void *data)
 645 {
 646         struct die_args *args = (struct die_args *)data;
 647         int ret = NOTIFY_DONE;
 648
 649         if (args->regs && user_mode(args->regs))
 650                 return ret;
 651
 652         switch (val) {
 653         case DIE_INT3:
 654                 if (kprobe_handler(args->regs))
 655                         ret = NOTIFY_STOP;
 656                 break;
 657         case DIE_DEBUG:
 658                 if (post_kprobe_handler(args->regs))
 659                         ret = NOTIFY_STOP;
 660                 break;
 661         case DIE_GPF:
 662                 /* kprobe_running() needs smp_processor_id() */
 663                 preempt_disable();
 664                 if (kprobe_running() &&
 665                     kprobe_fault_handler(args->regs, args->trapnr))
 666                         ret = NOTIFY_STOP;
 667                 preempt_enable();
 668                 break;
 669         default:
 670                 break;
 671         }
 672         return ret;
 673 }
 674
 675 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 676 {
 677         struct jprobe *jp = container_of(p, struct jprobe, kp);
 678         unsigned long addr;
 679         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 680
 681         kcb->jprobe_saved_regs = *regs;
 682         kcb->jprobe_saved_rsp = (long *) regs->rsp;
 683         addr = (unsigned long)(kcb->jprobe_saved_rsp);
 684         /*
 685          * As Linus pointed out, gcc assumes that the callee
 686          * owns the argument space and could overwrite it, e.g.
 687          * tailcall optimization. So, to be absolutely safe
 688          * we also save and restore enough stack bytes to cover
 689          * the argument area.
 690          */
 691         memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
 692                         MIN_STACK_SIZE(addr));
 693         regs->eflags &= ~IF_MASK;
 694         trace_hardirqs_off();
 695         regs->rip = (unsigned long)(jp->entry);
 696         return 1;
 697 }
 698
 699 void __kprobes jprobe_return(void)
 700 {
 701         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 702
 703         asm volatile ("       xchg   %%rbx,%%rsp     \n"
 704                       "       int3                      \n"
 705                       "       .globl jprobe_return_end  \n"
 706                       "       jprobe_return_end:        \n"
 707                       "       nop                       \n"::"b"
 708                       (kcb->jprobe_saved_rsp):"memory");
 709 }
 710
 711 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 712 {
 713         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 714         u8 *addr = (u8 *) (regs->rip - 1);
 715         unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
 716         struct jprobe *jp = container_of(p, struct jprobe, kp);
 717
 718         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
 719                 if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
 720                         struct pt_regs *saved_regs =
 721                             container_of(kcb->jprobe_saved_rsp,
 722                                             struct pt_regs, rsp);
 723                         printk("current rsp %p does not match saved rsp %p\n",
 724                                (long *)regs->rsp, kcb->jprobe_saved_rsp);
 725                         printk("Saved registers for jprobe %p\n", jp);
 726                         show_registers(saved_regs);
 727                         printk("Current registers\n");
 728                         show_registers(regs);
 729                         BUG();
 730                 }
 731                 *regs = kcb->jprobe_saved_regs;
 732                 memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
 733                        MIN_STACK_SIZE(stack_addr));
 734                 preempt_enable_no_resched();
 735                 return 1;
 736         }
 737         return 0;
 738 }
 739
 740 static struct kprobe trampoline_p = {
 741         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 742         .pre_handler = trampoline_probe_handler
 743 };
 744
 745 int __init arch_init_kprobes(void)
 746 {
 747         return register_kprobe(&trampoline_p);
 748 }
 749
 750 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 751 {
 752         if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
 753                 return 1;
 754
 755         return 0;
 756 }