uprobe/arch/x86/swap-asm/swap_uprobes.c

   1 /**
   2  * uprobe/arch/asm-x86/swap_uprobes.c
   3  * @author Alexey Gerenkov <a.gerenkov@samsung.com> User-Space Probes initial
   4  * implementation; Support x86/ARM/MIPS for both user and kernel spaces.
   5  * @author Ekaterina Gorelkina <e.gorelkina@samsung.com>: redesign module for
   6  * separating core and arch parts
   7  *
   8  * @section LICENSE
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23  *
  24  * @section COPYRIGHT
  25  *
  26  * Copyright (C) Samsung Electronics, 2006-2010
  27  *
  28  * @section DESCRIPTION
  29  *
  30  * Arch-dependent uprobe interface implementation for x86.
  31  */
  32
  33
  34 #include <linux/kdebug.h>
  35
  36 #include <kprobe/swap_slots.h>
  37 #include <uprobe/swap_uprobes.h>
  38
  39 #include "swap_uprobes.h"
  40
  41
  42 /**
  43  * @struct uprobe_ctlblk
  44  * @brief Uprobe control block
  45  */
  46 struct uprobe_ctlblk {
  47         unsigned long flags;            /**< Flags */
  48         struct kprobe *p;               /**< Pointer to the uprobe's kprobe */
  49 };
  50
  51 static unsigned long trampoline_addr(struct uprobe *up)
  52 {
  53         return (unsigned long)(up->kp.ainsn.insn +
  54                                UPROBES_TRAMP_RET_BREAK_IDX);
  55 }
  56
  57 static DEFINE_PER_CPU(struct uprobe_ctlblk, ucb) = { 0, NULL };
  58
  59 static struct kprobe *get_current_probe(void)
  60 {
  61         return __get_cpu_var(ucb).p;
  62 }
  63
  64 static void set_current_probe(struct kprobe *p)
  65 {
  66         __get_cpu_var(ucb).p = p;
  67 }
  68
  69 static void reset_current_probe(void)
  70 {
  71         set_current_probe(NULL);
  72 }
  73
  74 static void save_current_flags(struct pt_regs *regs)
  75 {
  76         __get_cpu_var(ucb).flags = regs->EREG(flags);
  77 }
  78
  79 static void restore_current_flags(struct pt_regs *regs)
  80 {
  81         regs->EREG(flags) &= ~IF_MASK;
  82         regs->EREG(flags) |= __get_cpu_var(ucb).flags & IF_MASK;
  83 }
  84
  85 /**
  86  * @brief Prepares uprobe for x86.
  87  *
  88  * @param up Pointer to the uprobe.
  89  * @return 0 on success,\n
  90  * -1 on error.
  91  */
  92 int arch_prepare_uprobe(struct uprobe *up)
  93 {
  94         int ret = 0;
  95         struct kprobe *p = up2kp(up);
  96         struct task_struct *task = up->task;
  97         u8 *tramp = up->atramp.tramp;
  98         enum { call_relative_opcode = 0xe8 };
  99
 100         if (!read_proc_vm_atomic(task, (unsigned long)p->addr,
 101                                  tramp, MAX_INSN_SIZE))
 102                 panic("failed to read memory %p!\n", p->addr);
 103         /* TODO: this is a workaround */
 104         if (tramp[0] == call_relative_opcode) {
 105                 printk(KERN_INFO "cannot install probe: 1st instruction is call\n");
 106                 return -1;
 107         }
 108
 109         tramp[UPROBES_TRAMP_RET_BREAK_IDX] = BREAKPOINT_INSTRUCTION;
 110
 111         /* TODO: remove dual info */
 112         p->opcode = tramp[0];
 113
 114         p->ainsn.boostable = swap_can_boost(tramp) ? 0 : -1;
 115
 116         return ret;
 117 }
 118
 119 /**
 120  * @brief Jump pre-handler.
 121  *
 122  * @param p Pointer to the uprobe's kprobe.
 123  * @param regs Pointer to CPU register data.
 124  * @return 0.
 125  */
 126 int setjmp_upre_handler(struct kprobe *p, struct pt_regs *regs)
 127 {
 128         struct uprobe *up = container_of(p, struct uprobe, kp);
 129         struct ujprobe *jp = container_of(up, struct ujprobe, up);
 130         kprobe_pre_entry_handler_t pre_entry =
 131                 (kprobe_pre_entry_handler_t)jp->pre_entry;
 132         entry_point_t entry = (entry_point_t)jp->entry;
 133         unsigned long args[6];
 134
 135         /* FIXME some user space apps crash if we clean interrupt bit */
 136         /* regs->EREG(flags) &= ~IF_MASK; */
 137 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 18)
 138         trace_hardirqs_off();
 139 #endif
 140
 141         /* read first 6 args from stack */
 142         if (!read_proc_vm_atomic(current, regs->EREG(sp) + 4,
 143                                  args, sizeof(args)))
 144                 panic("failed to read user space func arguments %lx!\n",
 145                       regs->EREG(sp) + 4);
 146
 147         if (pre_entry)
 148                 p->ss_addr[smp_processor_id()] = (kprobe_opcode_t *)
 149                                                  pre_entry(jp->priv_arg, regs);
 150
 151         if (entry)
 152                 entry(args[0], args[1], args[2], args[3], args[4], args[5]);
 153         else
 154                 arch_ujprobe_return();
 155
 156         return 0;
 157 }
 158
 159 /**
 160  * @brief Prepares uretprobe for x86.
 161  *
 162  * @param ri Pointer to the uretprobe instance.
 163  * @param regs Pointer to CPU register data.
 164  * @return Void.
 165  */
 166 void arch_prepare_uretprobe(struct uretprobe_instance *ri, struct pt_regs *regs)
 167 {
 168         /* Replace the return addr with trampoline addr */
 169         unsigned long ra = trampoline_addr(&ri->rp->up);
 170         ri->sp = (kprobe_opcode_t *)regs->sp;
 171
 172         if (!read_proc_vm_atomic(current, regs->EREG(sp), &(ri->ret_addr),
 173                                  sizeof(ri->ret_addr)))
 174                 panic("failed to read user space func ra %lx!\n",
 175                       regs->EREG(sp));
 176
 177         if (!write_proc_vm_atomic(current, regs->EREG(sp), &ra, sizeof(ra)))
 178                 panic("failed to write user space func ra %lx!\n",
 179                       regs->EREG(sp));
 180 }
 181
 182 /**
 183  * @brief Disarms uretprobe on x86 arch.
 184  *
 185  * @param ri Pointer to the uretprobe instance.
 186  * @param task Pointer to the task for which the probe.
 187  * @return 0 on success,\n
 188  * negative error code on error.
 189  */
 190 int arch_disarm_urp_inst(struct uretprobe_instance *ri,
 191                          struct task_struct *task)
 192 {
 193         int len;
 194         unsigned long ret_addr;
 195         unsigned long sp = (unsigned long)ri->sp;
 196         unsigned long tramp_addr = trampoline_addr(&ri->rp->up);
 197         len = read_proc_vm_atomic(task, sp, &ret_addr, sizeof(ret_addr));
 198         if (len != sizeof(ret_addr)) {
 199                 printk(KERN_INFO "---> %s (%d/%d): failed to read stack from %08lx\n",
 200                        task->comm, task->tgid, task->pid, sp);
 201                 return -EFAULT;
 202         }
 203
 204         if (tramp_addr == ret_addr) {
 205                 len = write_proc_vm_atomic(task, sp, &ri->ret_addr,
 206                                            sizeof(ri->ret_addr));
 207                 if (len != sizeof(ri->ret_addr)) {
 208                         printk(KERN_INFO "---> %s (%d/%d): failed to write "
 209                                "orig_ret_addr to %08lx",
 210                                task->comm, task->tgid, task->pid, sp);
 211                         return -EFAULT;
 212                 }
 213         } else {
 214                 printk(KERN_INFO "---> %s (%d/%d): trampoline NOT found at sp = %08lx\n",
 215                        task->comm, task->tgid, task->pid, sp);
 216                 return -ENOENT;
 217         }
 218
 219         return 0;
 220 }
 221
 222 /**
 223  * @brief Gets trampoline address.
 224  *
 225  * @param p Pointer to the uprobe's kprobe.
 226  * @param regs Pointer to CPU register data.
 227  * @return Trampoline address.
 228  */
 229 unsigned long arch_get_trampoline_addr(struct kprobe *p, struct pt_regs *regs)
 230 {
 231         return trampoline_addr(kp2up(p));
 232 }
 233
 234 /**
 235  * @brief Restores return address.
 236  *
 237  * @param orig_ret_addr Original return address.
 238  * @param regs Pointer to CPU register data.
 239  * @return Void.
 240  */
 241 void arch_set_orig_ret_addr(unsigned long orig_ret_addr, struct pt_regs *regs)
 242 {
 243         regs->EREG(ip) = orig_ret_addr;
 244 }
 245
 246 /**
 247  * @brief Removes uprobe.
 248  *
 249  * @param up Pointer to the target uprobe.
 250  * @return Void.
 251  */
 252 void arch_remove_uprobe(struct uprobe *up)
 253 {
 254         struct kprobe *p = up2kp(up);
 255
 256         swap_slot_free(up->sm, p->ainsn.insn);
 257 }
 258
 259 static void set_user_jmp_op(void *from, void *to)
 260 {
 261         struct __arch_jmp_op {
 262                 char op;
 263                 long raddr;
 264         } __packed jop;
 265
 266         jop.raddr = (long)(to) - ((long)(from) + 5);
 267         jop.op = RELATIVEJUMP_INSTRUCTION;
 268
 269         if (!write_proc_vm_atomic(current, (unsigned long)from, &jop,
 270                                   sizeof(jop)))
 271                 panic("failed to write jump opcode to user space %p!\n", from);
 272 }
 273
 274 static void resume_execution(struct kprobe *p,
 275                              struct pt_regs *regs,
 276                              unsigned long flags)
 277 {
 278         unsigned long *tos, tos_dword = 0;
 279         unsigned long copy_eip = (unsigned long)p->ainsn.insn;
 280         unsigned long orig_eip = (unsigned long)p->addr;
 281         kprobe_opcode_t insns[2];
 282
 283         regs->EREG(flags) &= ~TF_MASK;
 284
 285         tos = (unsigned long *)&tos_dword;
 286         if (!read_proc_vm_atomic(current, regs->EREG(sp), &tos_dword,
 287                                  sizeof(tos_dword)))
 288                 panic("failed to read dword from top of the user space stack "
 289                       "%lx!\n", regs->EREG(sp));
 290
 291         if (!read_proc_vm_atomic(current, (unsigned long)p->ainsn.insn, insns,
 292                                  2 * sizeof(kprobe_opcode_t)))
 293                 panic("failed to read first 2 opcodes of instruction copy "
 294                       "from user space %p!\n", p->ainsn.insn);
 295
 296         switch (insns[0]) {
 297         case 0x9c: /* pushfl */
 298                 *tos &= ~(TF_MASK | IF_MASK);
 299                 *tos |= flags & (TF_MASK | IF_MASK);
 300                 break;
 301         case 0xc2: /* iret/ret/lret */
 302         case 0xc3:
 303         case 0xca:
 304         case 0xcb:
 305         case 0xcf:
 306         case 0xea: /* jmp absolute -- eip is correct */
 307                 /* eip is already adjusted, no more changes required */
 308                 p->ainsn.boostable = 1;
 309                 goto no_change;
 310         case 0xe8: /* call relative - Fix return addr */
 311                 *tos = orig_eip + (*tos - copy_eip);
 312                 break;
 313         case 0x9a: /* call absolute -- same as call absolute, indirect */
 314                 *tos = orig_eip + (*tos - copy_eip);
 315
 316                 if (!write_proc_vm_atomic(current,
 317                                           regs->EREG(sp),
 318                                           &tos_dword,
 319                                           sizeof(tos_dword)))
 320                         panic("failed to write dword to top of the"
 321                               " user space stack %lx!\n",
 322                               regs->EREG(sp));
 323
 324                 goto no_change;
 325         case 0xff:
 326                 if ((insns[1] & 0x30) == 0x10) {
 327                         /*
 328                          * call absolute, indirect
 329                          * Fix return addr; eip is correct.
 330                          * But this is not boostable
 331                          */
 332                         *tos = orig_eip + (*tos - copy_eip);
 333
 334                         if (!write_proc_vm_atomic(current, regs->EREG(sp),
 335                                                   &tos_dword,
 336                                                   sizeof(tos_dword)))
 337                                 panic("failed to write dword to top of the "
 338                                       "user space stack %lx!\n",
 339                                       regs->EREG(sp));
 340
 341                         goto no_change;
 342                 } else if (((insns[1] & 0x31) == 0x20) || /* jmp near, absolute
 343                                                            * indirect */
 344                            ((insns[1] & 0x31) == 0x21)) {
 345                         /* jmp far, absolute indirect */
 346                         /* eip is correct. And this is boostable */
 347                         p->ainsn.boostable = 1;
 348                         goto no_change;
 349                 }
 350         case 0xf3:
 351                 if (insns[1] == 0xc3)
 352                         /* repz ret special handling: no more changes */
 353                         goto no_change;
 354                 break;
 355         default:
 356                 break;
 357         }
 358
 359         if (!write_proc_vm_atomic(current, regs->EREG(sp), &tos_dword,
 360                                   sizeof(tos_dword)))
 361                 panic("failed to write dword to top of the user space stack "
 362                       "%lx!\n", regs->EREG(sp));
 363
 364         if (p->ainsn.boostable == 0) {
 365                 if ((regs->EREG(ip) > copy_eip) && (regs->EREG(ip) - copy_eip) +
 366                     5 < MAX_INSN_SIZE) {
 367                         /*
 368                          * These instructions can be executed directly if it
 369                          * jumps back to correct address.
 370                          */
 371                         set_user_jmp_op((void *) regs->EREG(ip),
 372                                         (void *)orig_eip +
 373                                         (regs->EREG(ip) - copy_eip));
 374                         p->ainsn.boostable = 1;
 375                 } else {
 376                         p->ainsn.boostable = -1;
 377                 }
 378         }
 379
 380         regs->EREG(ip) = orig_eip + (regs->EREG(ip) - copy_eip);
 381
 382 no_change:
 383         return;
 384 }
 385
 386 static int make_trampoline(struct uprobe *up)
 387 {
 388         struct kprobe *p = up2kp(up);
 389         struct task_struct *task = up->task;
 390         void *tramp;
 391
 392         tramp = swap_slot_alloc(up->sm);
 393         if (tramp == 0) {
 394                 printk(KERN_INFO "trampoline out of memory\n");
 395                 return -ENOMEM;
 396         }
 397
 398         if (!write_proc_vm_atomic(task, (unsigned long)tramp,
 399                                   up->atramp.tramp,
 400                                   sizeof(up->atramp.tramp))) {
 401                 swap_slot_free(up->sm, tramp);
 402                 panic("failed to write memory %p!\n", tramp);
 403                 return -EINVAL;
 404         }
 405
 406         p->ainsn.insn = tramp;
 407
 408         return 0;
 409 }
 410
 411 static int uprobe_handler(struct pt_regs *regs)
 412 {
 413         struct kprobe *p;
 414         kprobe_opcode_t *addr;
 415         struct task_struct *task = current;
 416         pid_t tgid = task->tgid;
 417
 418         save_current_flags(regs);
 419
 420         addr = (kprobe_opcode_t *)(regs->EREG(ip) - sizeof(kprobe_opcode_t));
 421         p = get_ukprobe(addr, tgid);
 422
 423         if (p == NULL) {
 424                 void *tramp_addr = (void *)addr - UPROBES_TRAMP_RET_BREAK_IDX;
 425
 426                 p = get_ukprobe_by_insn_slot(tramp_addr, tgid, regs);
 427                 if (p == NULL) {
 428                         printk(KERN_INFO "no_uprobe\n");
 429                         return 0;
 430                 }
 431
 432                 trampoline_uprobe_handler(p, regs);
 433                 return 1;
 434         } else {
 435                 if (p->ainsn.insn == NULL) {
 436                         struct uprobe *up = kp2up(p);
 437
 438                         make_trampoline(up);
 439
 440                         /* for uretprobe */
 441                         add_uprobe_table(p);
 442                 }
 443
 444                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
 445
 446                         if (p->ainsn.boostable == 1 && !p->post_handler) {
 447                                 if (p->ss_addr[smp_processor_id()]) {
 448                                         regs->EREG(ip) = (unsigned long)p->ss_addr[smp_processor_id()];
 449                                         p->ss_addr[smp_processor_id()] = NULL;
 450                                 } else {
 451                                         regs->EREG(ip) = (unsigned long)p->ainsn.insn;
 452                                 }
 453                                 return 1;
 454                         }
 455
 456                         prepare_singlestep(p, regs);
 457                 }
 458         }
 459
 460         set_current_probe(p);
 461
 462         return 1;
 463 }
 464
 465 static int post_uprobe_handler(struct pt_regs *regs)
 466 {
 467         struct kprobe *p = get_current_probe();
 468         unsigned long flags = __get_cpu_var(ucb).flags;
 469
 470         if (p == NULL)
 471                 return 0;
 472
 473         resume_execution(p, regs, flags);
 474         restore_current_flags(regs);
 475
 476         reset_current_probe();
 477
 478         return 1;
 479 }
 480
 481 static int uprobe_exceptions_notify(struct notifier_block *self,
 482                                     unsigned long val, void *data)
 483 {
 484         struct die_args *args = (struct die_args *)data;
 485         int ret = NOTIFY_DONE;
 486
 487         if (args->regs == NULL || !user_mode_vm(args->regs))
 488                 return ret;
 489
 490         switch (val) {
 491 #ifdef CONFIG_KPROBES
 492         case DIE_INT3:
 493 #else
 494         case DIE_TRAP:
 495 #endif
 496                 if (uprobe_handler(args->regs))
 497                         ret = NOTIFY_STOP;
 498                 break;
 499         case DIE_DEBUG:
 500                 if (post_uprobe_handler(args->regs))
 501                         ret = NOTIFY_STOP;
 502                 break;
 503         default:
 504                 break;
 505         }
 506
 507         return ret;
 508 }
 509
 510 static struct notifier_block uprobe_exceptions_nb = {
 511         .notifier_call = uprobe_exceptions_notify,
 512         .priority = INT_MAX
 513 };
 514
 515 /**
 516  * @brief Registers notify.
 517  *
 518  * @return register_die_notifier result.
 519  */
 520 int swap_arch_init_uprobes(void)
 521 {
 522         return register_die_notifier(&uprobe_exceptions_nb);
 523 }
 524
 525 /**
 526  * @brief Unregisters notify.
 527  *
 528  * @return Void.
 529  */
 530 void swap_arch_exit_uprobes(void)
 531 {
 532         unregister_die_notifier(&uprobe_exceptions_nb);
 533 }
 534