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         struct kprobe *p = up2kp(up);
  95         struct task_struct *task = up->task;
  96         u8 *tramp = up->atramp.tramp;
  97         enum { call_relative_opcode = 0xe8 };
  98
  99         if (!read_proc_vm_atomic(task, (unsigned long)p->addr,
 100                                  tramp, MAX_INSN_SIZE))
 101                 panic("failed to read memory %p!\n", p->addr);
 102         /* TODO: this is a workaround */
 103         if (tramp[0] == call_relative_opcode) {
 104                 printk(KERN_INFO "cannot install probe: 1st instruction is call\n");
 105                 return -1;
 106         }
 107
 108         tramp[UPROBES_TRAMP_RET_BREAK_IDX] = BREAKPOINT_INSTRUCTION;
 109
 110         /* TODO: remove dual info */
 111         p->opcode = tramp[0];
 112
 113         p->ainsn.boostable = swap_can_boost(tramp) ? 0 : -1;
 114
 115         p->ainsn.insn = swap_slot_alloc(up->sm);
 116         if (p->ainsn.insn == NULL) {
 117                 printk(KERN_INFO "trampoline out of memory\n");
 118                 return -ENOMEM;
 119         }
 120
 121         if (!write_proc_vm_atomic(task, (unsigned long)p->ainsn.insn,
 122                                   tramp, sizeof(up->atramp.tramp))) {
 123                 swap_slot_free(up->sm, p->ainsn.insn);
 124                 printk("failed to write memory %p!\n", tramp);
 125                 return -EINVAL;
 126         }
 127
 128         return 0;
 129 }
 130
 131 /**
 132  * @brief Jump pre-handler.
 133  *
 134  * @param p Pointer to the uprobe's kprobe.
 135  * @param regs Pointer to CPU register data.
 136  * @return 0.
 137  */
 138 int setjmp_upre_handler(struct kprobe *p, struct pt_regs *regs)
 139 {
 140         struct uprobe *up = container_of(p, struct uprobe, kp);
 141         struct ujprobe *jp = container_of(up, struct ujprobe, up);
 142         kprobe_pre_entry_handler_t pre_entry =
 143                 (kprobe_pre_entry_handler_t)jp->pre_entry;
 144         entry_point_t entry = (entry_point_t)jp->entry;
 145         unsigned long args[6];
 146
 147         /* FIXME some user space apps crash if we clean interrupt bit */
 148         /* regs->EREG(flags) &= ~IF_MASK; */
 149 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 18)
 150         trace_hardirqs_off();
 151 #endif
 152
 153         /* read first 6 args from stack */
 154         if (!read_proc_vm_atomic(current, regs->EREG(sp) + 4,
 155                                  args, sizeof(args)))
 156                 panic("failed to read user space func arguments %lx!\n",
 157                       regs->EREG(sp) + 4);
 158
 159         if (pre_entry)
 160                 p->ss_addr[smp_processor_id()] = (kprobe_opcode_t *)
 161                                                  pre_entry(jp->priv_arg, regs);
 162
 163         if (entry)
 164                 entry(args[0], args[1], args[2], args[3], args[4], args[5]);
 165         else
 166                 arch_ujprobe_return();
 167
 168         return 0;
 169 }
 170
 171 /**
 172  * @brief Prepares uretprobe for x86.
 173  *
 174  * @param ri Pointer to the uretprobe instance.
 175  * @param regs Pointer to CPU register data.
 176  * @return Void.
 177  */
 178 void arch_prepare_uretprobe(struct uretprobe_instance *ri, struct pt_regs *regs)
 179 {
 180         /* Replace the return addr with trampoline addr */
 181         unsigned long ra = trampoline_addr(&ri->rp->up);
 182         ri->sp = (kprobe_opcode_t *)regs->sp;
 183
 184         if (!read_proc_vm_atomic(current, regs->EREG(sp), &(ri->ret_addr),
 185                                  sizeof(ri->ret_addr)))
 186                 panic("failed to read user space func ra %lx!\n",
 187                       regs->EREG(sp));
 188
 189         if (!write_proc_vm_atomic(current, regs->EREG(sp), &ra, sizeof(ra)))
 190                 panic("failed to write user space func ra %lx!\n",
 191                       regs->EREG(sp));
 192
 193         add_uprobe_table(&ri->rp->up.kp);
 194 }
 195
 196 /**
 197  * @brief Disarms uretprobe on x86 arch.
 198  *
 199  * @param ri Pointer to the uretprobe instance.
 200  * @param task Pointer to the task for which the probe.
 201  * @return 0 on success,\n
 202  * negative error code on error.
 203  */
 204 int arch_disarm_urp_inst(struct uretprobe_instance *ri,
 205                          struct task_struct *task)
 206 {
 207         int len;
 208         unsigned long ret_addr;
 209         unsigned long sp = (unsigned long)ri->sp;
 210         unsigned long tramp_addr = trampoline_addr(&ri->rp->up);
 211         len = read_proc_vm_atomic(task, sp, &ret_addr, sizeof(ret_addr));
 212         if (len != sizeof(ret_addr)) {
 213                 printk(KERN_INFO "---> %s (%d/%d): failed to read stack from %08lx\n",
 214                        task->comm, task->tgid, task->pid, sp);
 215                 return -EFAULT;
 216         }
 217
 218         if (tramp_addr == ret_addr) {
 219                 len = write_proc_vm_atomic(task, sp, &ri->ret_addr,
 220                                            sizeof(ri->ret_addr));
 221                 if (len != sizeof(ri->ret_addr)) {
 222                         printk(KERN_INFO "---> %s (%d/%d): failed to write "
 223                                "orig_ret_addr to %08lx",
 224                                task->comm, task->tgid, task->pid, sp);
 225                         return -EFAULT;
 226                 }
 227         } else {
 228                 printk(KERN_INFO "---> %s (%d/%d): trampoline NOT found at sp = %08lx\n",
 229                        task->comm, task->tgid, task->pid, sp);
 230                 return -ENOENT;
 231         }
 232
 233         return 0;
 234 }
 235
 236 /**
 237  * @brief Gets trampoline address.
 238  *
 239  * @param p Pointer to the uprobe's kprobe.
 240  * @param regs Pointer to CPU register data.
 241  * @return Trampoline address.
 242  */
 243 unsigned long arch_get_trampoline_addr(struct kprobe *p, struct pt_regs *regs)
 244 {
 245         return trampoline_addr(kp2up(p));
 246 }
 247
 248 /**
 249  * @brief Restores return address.
 250  *
 251  * @param orig_ret_addr Original return address.
 252  * @param regs Pointer to CPU register data.
 253  * @return Void.
 254  */
 255 void arch_set_orig_ret_addr(unsigned long orig_ret_addr, struct pt_regs *regs)
 256 {
 257         regs->EREG(ip) = orig_ret_addr;
 258 }
 259
 260 /**
 261  * @brief Removes uprobe.
 262  *
 263  * @param up Pointer to the target uprobe.
 264  * @return Void.
 265  */
 266 void arch_remove_uprobe(struct uprobe *up)
 267 {
 268         struct kprobe *p = up2kp(up);
 269
 270         swap_slot_free(up->sm, p->ainsn.insn);
 271 }
 272
 273 static void set_user_jmp_op(void *from, void *to)
 274 {
 275         struct __arch_jmp_op {
 276                 char op;
 277                 long raddr;
 278         } __packed jop;
 279
 280         jop.raddr = (long)(to) - ((long)(from) + 5);
 281         jop.op = RELATIVEJUMP_INSTRUCTION;
 282
 283         if (!write_proc_vm_atomic(current, (unsigned long)from, &jop,
 284                                   sizeof(jop)))
 285                 panic("failed to write jump opcode to user space %p!\n", from);
 286 }
 287
 288 static void resume_execution(struct kprobe *p,
 289                              struct pt_regs *regs,
 290                              unsigned long flags)
 291 {
 292         unsigned long *tos, tos_dword = 0;
 293         unsigned long copy_eip = (unsigned long)p->ainsn.insn;
 294         unsigned long orig_eip = (unsigned long)p->addr;
 295         kprobe_opcode_t insns[2];
 296
 297         regs->EREG(flags) &= ~TF_MASK;
 298
 299         tos = (unsigned long *)&tos_dword;
 300         if (!read_proc_vm_atomic(current, regs->EREG(sp), &tos_dword,
 301                                  sizeof(tos_dword)))
 302                 panic("failed to read dword from top of the user space stack "
 303                       "%lx!\n", regs->EREG(sp));
 304
 305         if (!read_proc_vm_atomic(current, (unsigned long)p->ainsn.insn, insns,
 306                                  2 * sizeof(kprobe_opcode_t)))
 307                 panic("failed to read first 2 opcodes of instruction copy "
 308                       "from user space %p!\n", p->ainsn.insn);
 309
 310         switch (insns[0]) {
 311         case 0x9c: /* pushfl */
 312                 *tos &= ~(TF_MASK | IF_MASK);
 313                 *tos |= flags & (TF_MASK | IF_MASK);
 314                 break;
 315         case 0xc2: /* iret/ret/lret */
 316         case 0xc3:
 317         case 0xca:
 318         case 0xcb:
 319         case 0xcf:
 320         case 0xea: /* jmp absolute -- eip is correct */
 321                 /* eip is already adjusted, no more changes required */
 322                 p->ainsn.boostable = 1;
 323                 goto no_change;
 324         case 0xe8: /* call relative - Fix return addr */
 325                 *tos = orig_eip + (*tos - copy_eip);
 326                 break;
 327         case 0x9a: /* call absolute -- same as call absolute, indirect */
 328                 *tos = orig_eip + (*tos - copy_eip);
 329
 330                 if (!write_proc_vm_atomic(current,
 331                                           regs->EREG(sp),
 332                                           &tos_dword,
 333                                           sizeof(tos_dword)))
 334                         panic("failed to write dword to top of the"
 335                               " user space stack %lx!\n",
 336                               regs->EREG(sp));
 337
 338                 goto no_change;
 339         case 0xff:
 340                 if ((insns[1] & 0x30) == 0x10) {
 341                         /*
 342                          * call absolute, indirect
 343                          * Fix return addr; eip is correct.
 344                          * But this is not boostable
 345                          */
 346                         *tos = orig_eip + (*tos - copy_eip);
 347
 348                         if (!write_proc_vm_atomic(current, regs->EREG(sp),
 349                                                   &tos_dword,
 350                                                   sizeof(tos_dword)))
 351                                 panic("failed to write dword to top of the "
 352                                       "user space stack %lx!\n",
 353                                       regs->EREG(sp));
 354
 355                         goto no_change;
 356                 } else if (((insns[1] & 0x31) == 0x20) || /* jmp near, absolute
 357                                                            * indirect */
 358                            ((insns[1] & 0x31) == 0x21)) {
 359                         /* jmp far, absolute indirect */
 360                         /* eip is correct. And this is boostable */
 361                         p->ainsn.boostable = 1;
 362                         goto no_change;
 363                 }
 364         case 0xf3:
 365                 if (insns[1] == 0xc3)
 366                         /* repz ret special handling: no more changes */
 367                         goto no_change;
 368                 break;
 369         default:
 370                 break;
 371         }
 372
 373         if (!write_proc_vm_atomic(current, regs->EREG(sp), &tos_dword,
 374                                   sizeof(tos_dword)))
 375                 panic("failed to write dword to top of the user space stack "
 376                       "%lx!\n", regs->EREG(sp));
 377
 378         if (p->ainsn.boostable == 0) {
 379                 if ((regs->EREG(ip) > copy_eip) && (regs->EREG(ip) - copy_eip) +
 380                     5 < MAX_INSN_SIZE) {
 381                         /*
 382                          * These instructions can be executed directly if it
 383                          * jumps back to correct address.
 384                          */
 385                         set_user_jmp_op((void *) regs->EREG(ip),
 386                                         (void *)orig_eip +
 387                                         (regs->EREG(ip) - copy_eip));
 388                         p->ainsn.boostable = 1;
 389                 } else {
 390                         p->ainsn.boostable = -1;
 391                 }
 392         }
 393
 394         regs->EREG(ip) = orig_eip + (regs->EREG(ip) - copy_eip);
 395
 396 no_change:
 397         return;
 398 }
 399
 400 static int uprobe_handler(struct pt_regs *regs)
 401 {
 402         struct kprobe *p;
 403         kprobe_opcode_t *addr;
 404         struct task_struct *task = current;
 405         pid_t tgid = task->tgid;
 406
 407         save_current_flags(regs);
 408
 409         addr = (kprobe_opcode_t *)(regs->EREG(ip) - sizeof(kprobe_opcode_t));
 410         p = get_ukprobe(addr, tgid);
 411
 412         if (p == NULL) {
 413                 void *tramp_addr = (void *)addr - UPROBES_TRAMP_RET_BREAK_IDX;
 414
 415                 p = get_ukprobe_by_insn_slot(tramp_addr, tgid, regs);
 416                 if (p == NULL) {
 417                         printk(KERN_INFO "no_uprobe\n");
 418                         return 0;
 419                 }
 420
 421                 trampoline_uprobe_handler(p, regs);
 422                 return 1;
 423         } else {
 424                 if (!p->pre_handler || !p->pre_handler(p, regs)) {
 425
 426                         if (p->ainsn.boostable == 1 && !p->post_handler) {
 427                                 if (p->ss_addr[smp_processor_id()]) {
 428                                         regs->EREG(ip) = (unsigned long)p->ss_addr[smp_processor_id()];
 429                                         p->ss_addr[smp_processor_id()] = NULL;
 430                                 } else {
 431                                         regs->EREG(ip) = (unsigned long)p->ainsn.insn;
 432                                 }
 433                                 return 1;
 434                         }
 435
 436                         prepare_singlestep(p, regs);
 437                 }
 438         }
 439
 440         set_current_probe(p);
 441
 442         return 1;
 443 }
 444
 445 static int post_uprobe_handler(struct pt_regs *regs)
 446 {
 447         struct kprobe *p = get_current_probe();
 448         unsigned long flags = __get_cpu_var(ucb).flags;
 449
 450         if (p == NULL)
 451                 return 0;
 452
 453         resume_execution(p, regs, flags);
 454         restore_current_flags(regs);
 455
 456         reset_current_probe();
 457
 458         return 1;
 459 }
 460
 461 static int uprobe_exceptions_notify(struct notifier_block *self,
 462                                     unsigned long val, void *data)
 463 {
 464         struct die_args *args = (struct die_args *)data;
 465         int ret = NOTIFY_DONE;
 466
 467         if (args->regs == NULL || !user_mode_vm(args->regs))
 468                 return ret;
 469
 470         switch (val) {
 471 #ifdef CONFIG_KPROBES
 472         case DIE_INT3:
 473 #else
 474         case DIE_TRAP:
 475 #endif
 476                 if (uprobe_handler(args->regs))
 477                         ret = NOTIFY_STOP;
 478                 break;
 479         case DIE_DEBUG:
 480                 if (post_uprobe_handler(args->regs))
 481                         ret = NOTIFY_STOP;
 482                 break;
 483         default:
 484                 break;
 485         }
 486
 487         return ret;
 488 }
 489
 490 static struct notifier_block uprobe_exceptions_nb = {
 491         .notifier_call = uprobe_exceptions_notify,
 492         .priority = INT_MAX
 493 };
 494
 495 /**
 496  * @brief Registers notify.
 497  *
 498  * @return register_die_notifier result.
 499  */
 500 int swap_arch_init_uprobes(void)
 501 {
 502         return register_die_notifier(&uprobe_exceptions_nb);
 503 }
 504
 505 /**
 506  * @brief Unregisters notify.
 507  *
 508  * @return Void.
 509  */
 510 void swap_arch_exit_uprobes(void)
 511 {
 512         unregister_die_notifier(&uprobe_exceptions_nb);
 513 }
 514