arch/x86/kernel/kprobes/opt.c

   1 /*
   2  *  Kernel Probes Jump Optimization (Optprobes)
   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  * Copyright (C) Hitachi Ltd., 2012
  20  */
  21 #include <linux/kprobes.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/string.h>
  24 #include <linux/slab.h>
  25 #include <linux/hardirq.h>
  26 #include <linux/preempt.h>
  27 #include <linux/module.h>
  28 #include <linux/kdebug.h>
  29 #include <linux/kallsyms.h>
  30 #include <linux/ftrace.h>
  31
  32 #include <asm/cacheflush.h>
  33 #include <asm/desc.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/uaccess.h>
  36 #include <asm/alternative.h>
  37 #include <asm/insn.h>
  38 #include <asm/debugreg.h>
  39
  40 #include "common.h"
  41
  42 unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
  43 {
  44         struct optimized_kprobe *op;
  45         struct kprobe *kp;
  46         long offs;
  47         int i;
  48
  49         for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
  50                 kp = get_kprobe((void *)addr - i);
  51                 /* This function only handles jump-optimized kprobe */
  52                 if (kp && kprobe_optimized(kp)) {
  53                         op = container_of(kp, struct optimized_kprobe, kp);
  54                         /* If op->list is not empty, op is under optimizing */
  55                         if (list_empty(&op->list))
  56                                 goto found;
  57                 }
  58         }
  59
  60         return addr;
  61 found:
  62         /*
  63          * If the kprobe can be optimized, original bytes which can be
  64          * overwritten by jump destination address. In this case, original
  65          * bytes must be recovered from op->optinsn.copied_insn buffer.
  66          */
  67         memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  68         if (addr == (unsigned long)kp->addr) {
  69                 buf[0] = kp->opcode;
  70                 memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
  71         } else {
  72                 offs = addr - (unsigned long)kp->addr - 1;
  73                 memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
  74         }
  75
  76         return (unsigned long)buf;
  77 }
  78
  79 /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
  80 static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
  81 {
  82 #ifdef CONFIG_X86_64
  83         *addr++ = 0x48;
  84         *addr++ = 0xbf;
  85 #else
  86         *addr++ = 0xb8;
  87 #endif
  88         *(unsigned long *)addr = val;
  89 }
  90
  91 static void __used __kprobes kprobes_optinsn_template_holder(void)
  92 {
  93         asm volatile (
  94                         ".global optprobe_template_entry\n"
  95                         "optprobe_template_entry:\n"
  96 #ifdef CONFIG_X86_64
  97                         /* We don't bother saving the ss register */
  98                         "       pushq %rsp\n"
  99                         "       pushfq\n"
 100                         SAVE_REGS_STRING
 101                         "       movq %rsp, %rsi\n"
 102                         ".global optprobe_template_val\n"
 103                         "optprobe_template_val:\n"
 104                         ASM_NOP5
 105                         ASM_NOP5
 106                         ".global optprobe_template_call\n"
 107                         "optprobe_template_call:\n"
 108                         ASM_NOP5
 109                         /* Move flags to rsp */
 110                         "       movq 144(%rsp), %rdx\n"
 111                         "       movq %rdx, 152(%rsp)\n"
 112                         RESTORE_REGS_STRING
 113                         /* Skip flags entry */
 114                         "       addq $8, %rsp\n"
 115                         "       popfq\n"
 116 #else /* CONFIG_X86_32 */
 117                         "       pushf\n"
 118                         SAVE_REGS_STRING
 119                         "       movl %esp, %edx\n"
 120                         ".global optprobe_template_val\n"
 121                         "optprobe_template_val:\n"
 122                         ASM_NOP5
 123                         ".global optprobe_template_call\n"
 124                         "optprobe_template_call:\n"
 125                         ASM_NOP5
 126                         RESTORE_REGS_STRING
 127                         "       addl $4, %esp\n"        /* skip cs */
 128                         "       popf\n"
 129 #endif
 130                         ".global optprobe_template_end\n"
 131                         "optprobe_template_end:\n");
 132 }
 133
 134 #define TMPL_MOVE_IDX \
 135         ((long)&optprobe_template_val - (long)&optprobe_template_entry)
 136 #define TMPL_CALL_IDX \
 137         ((long)&optprobe_template_call - (long)&optprobe_template_entry)
 138 #define TMPL_END_IDX \
 139         ((long)&optprobe_template_end - (long)&optprobe_template_entry)
 140
 141 #define INT3_SIZE sizeof(kprobe_opcode_t)
 142
 143 /* Optimized kprobe call back function: called from optinsn */
 144 static void __kprobes optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
 145 {
 146         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 147         unsigned long flags;
 148
 149         /* This is possible if op is under delayed unoptimizing */
 150         if (kprobe_disabled(&op->kp))
 151                 return;
 152
 153         local_irq_save(flags);
 154         if (kprobe_running()) {
 155                 kprobes_inc_nmissed_count(&op->kp);
 156         } else {
 157                 /* Save skipped registers */
 158 #ifdef CONFIG_X86_64
 159                 regs->cs = __KERNEL_CS;
 160 #else
 161                 regs->cs = __KERNEL_CS | get_kernel_rpl();
 162                 regs->gs = 0;
 163 #endif
 164                 regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
 165                 regs->orig_ax = ~0UL;
 166
 167                 __this_cpu_write(current_kprobe, &op->kp);
 168                 kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 169                 opt_pre_handler(&op->kp, regs);
 170                 __this_cpu_write(current_kprobe, NULL);
 171         }
 172         local_irq_restore(flags);
 173 }
 174
 175 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
 176 {
 177         int len = 0, ret;
 178
 179         while (len < RELATIVEJUMP_SIZE) {
 180                 ret = __copy_instruction(dest + len, src + len);
 181                 if (!ret || !can_boost(dest + len))
 182                         return -EINVAL;
 183                 len += ret;
 184         }
 185         /* Check whether the address range is reserved */
 186         if (ftrace_text_reserved(src, src + len - 1) ||
 187             alternatives_text_reserved(src, src + len - 1) ||
 188             jump_label_text_reserved(src, src + len - 1))
 189                 return -EBUSY;
 190
 191         return len;
 192 }
 193
 194 /* Check whether insn is indirect jump */
 195 static int __kprobes insn_is_indirect_jump(struct insn *insn)
 196 {
 197         return ((insn->opcode.bytes[0] == 0xff &&
 198                 (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
 199                 insn->opcode.bytes[0] == 0xea); /* Segment based jump */
 200 }
 201
 202 /* Check whether insn jumps into specified address range */
 203 static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
 204 {
 205         unsigned long target = 0;
 206
 207         switch (insn->opcode.bytes[0]) {
 208         case 0xe0:      /* loopne */
 209         case 0xe1:      /* loope */
 210         case 0xe2:      /* loop */
 211         case 0xe3:      /* jcxz */
 212         case 0xe9:      /* near relative jump */
 213         case 0xeb:      /* short relative jump */
 214                 break;
 215         case 0x0f:
 216                 if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
 217                         break;
 218                 return 0;
 219         default:
 220                 if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
 221                         break;
 222                 return 0;
 223         }
 224         target = (unsigned long)insn->next_byte + insn->immediate.value;
 225
 226         return (start <= target && target <= start + len);
 227 }
 228
 229 /* Decode whole function to ensure any instructions don't jump into target */
 230 static int __kprobes can_optimize(unsigned long paddr)
 231 {
 232         unsigned long addr, size = 0, offset = 0;
 233         struct insn insn;
 234         kprobe_opcode_t buf[MAX_INSN_SIZE];
 235
 236         /* Lookup symbol including addr */
 237         if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
 238                 return 0;
 239
 240         /*
 241          * Do not optimize in the entry code due to the unstable
 242          * stack handling.
 243          */
 244         if ((paddr >= (unsigned long)__entry_text_start) &&
 245             (paddr <  (unsigned long)__entry_text_end))
 246                 return 0;
 247
 248         /* Check there is enough space for a relative jump. */
 249         if (size - offset < RELATIVEJUMP_SIZE)
 250                 return 0;
 251
 252         /* Decode instructions */
 253         addr = paddr - offset;
 254         while (addr < paddr - offset + size) { /* Decode until function end */
 255                 if (search_exception_tables(addr))
 256                         /*
 257                          * Since some fixup code will jumps into this function,
 258                          * we can't optimize kprobe in this function.
 259                          */
 260                         return 0;
 261                 kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, addr));
 262                 insn_get_length(&insn);
 263                 /* Another subsystem puts a breakpoint */
 264                 if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
 265                         return 0;
 266                 /* Recover address */
 267                 insn.kaddr = (void *)addr;
 268                 insn.next_byte = (void *)(addr + insn.length);
 269                 /* Check any instructions don't jump into target */
 270                 if (insn_is_indirect_jump(&insn) ||
 271                     insn_jump_into_range(&insn, paddr + INT3_SIZE,
 272                                          RELATIVE_ADDR_SIZE))
 273                         return 0;
 274                 addr += insn.length;
 275         }
 276
 277         return 1;
 278 }
 279
 280 /* Check optimized_kprobe can actually be optimized. */
 281 int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)
 282 {
 283         int i;
 284         struct kprobe *p;
 285
 286         for (i = 1; i < op->optinsn.size; i++) {
 287                 p = get_kprobe(op->kp.addr + i);
 288                 if (p && !kprobe_disabled(p))
 289                         return -EEXIST;
 290         }
 291
 292         return 0;
 293 }
 294
 295 /* Check the addr is within the optimized instructions. */
 296 int __kprobes
 297 arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr)
 298 {
 299         return ((unsigned long)op->kp.addr <= addr &&
 300                 (unsigned long)op->kp.addr + op->optinsn.size > addr);
 301 }
 302
 303 /* Free optimized instruction slot */
 304 static __kprobes
 305 void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
 306 {
 307         if (op->optinsn.insn) {
 308                 free_optinsn_slot(op->optinsn.insn, dirty);
 309                 op->optinsn.insn = NULL;
 310                 op->optinsn.size = 0;
 311         }
 312 }
 313
 314 void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)
 315 {
 316         __arch_remove_optimized_kprobe(op, 1);
 317 }
 318
 319 /*
 320  * Copy replacing target instructions
 321  * Target instructions MUST be relocatable (checked inside)
 322  * This is called when new aggr(opt)probe is allocated or reused.
 323  */
 324 int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
 325 {
 326         u8 *buf;
 327         int ret;
 328         long rel;
 329
 330         if (!can_optimize((unsigned long)op->kp.addr))
 331                 return -EILSEQ;
 332
 333         op->optinsn.insn = get_optinsn_slot();
 334         if (!op->optinsn.insn)
 335                 return -ENOMEM;
 336
 337         /*
 338          * Verify if the address gap is in 2GB range, because this uses
 339          * a relative jump.
 340          */
 341         rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
 342         if (abs(rel) > 0x7fffffff)
 343                 return -ERANGE;
 344
 345         buf = (u8 *)op->optinsn.insn;
 346
 347         /* Copy instructions into the out-of-line buffer */
 348         ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
 349         if (ret < 0) {
 350                 __arch_remove_optimized_kprobe(op, 0);
 351                 return ret;
 352         }
 353         op->optinsn.size = ret;
 354
 355         /* Copy arch-dep-instance from template */
 356         memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
 357
 358         /* Set probe information */
 359         synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
 360
 361         /* Set probe function call */
 362         synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
 363
 364         /* Set returning jmp instruction at the tail of out-of-line buffer */
 365         synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
 366                            (u8 *)op->kp.addr + op->optinsn.size);
 367
 368         flush_icache_range((unsigned long) buf,
 369                            (unsigned long) buf + TMPL_END_IDX +
 370                            op->optinsn.size + RELATIVEJUMP_SIZE);
 371         return 0;
 372 }
 373
 374 #define MAX_OPTIMIZE_PROBES 256
 375 static struct text_poke_param *jump_poke_params;
 376 static struct jump_poke_buffer {
 377         u8 buf[RELATIVEJUMP_SIZE];
 378 } *jump_poke_bufs;
 379
 380 static void __kprobes setup_optimize_kprobe(struct text_poke_param *tprm,
 381                                             u8 *insn_buf,
 382                                             struct optimized_kprobe *op)
 383 {
 384         s32 rel = (s32)((long)op->optinsn.insn -
 385                         ((long)op->kp.addr + RELATIVEJUMP_SIZE));
 386
 387         /* Backup instructions which will be replaced by jump address */
 388         memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
 389                RELATIVE_ADDR_SIZE);
 390
 391         insn_buf[0] = RELATIVEJUMP_OPCODE;
 392         *(s32 *)(&insn_buf[1]) = rel;
 393
 394         tprm->addr = op->kp.addr;
 395         tprm->opcode = insn_buf;
 396         tprm->len = RELATIVEJUMP_SIZE;
 397 }
 398
 399 /*
 400  * Replace breakpoints (int3) with relative jumps.
 401  * Caller must call with locking kprobe_mutex and text_mutex.
 402  */
 403 void __kprobes arch_optimize_kprobes(struct list_head *oplist)
 404 {
 405         struct optimized_kprobe *op, *tmp;
 406         int c = 0;
 407
 408         list_for_each_entry_safe(op, tmp, oplist, list) {
 409                 WARN_ON(kprobe_disabled(&op->kp));
 410                 /* Setup param */
 411                 setup_optimize_kprobe(&jump_poke_params[c],
 412                                       jump_poke_bufs[c].buf, op);
 413                 list_del_init(&op->list);
 414                 if (++c >= MAX_OPTIMIZE_PROBES)
 415                         break;
 416         }
 417
 418         /*
 419          * text_poke_smp doesn't support NMI/MCE code modifying.
 420          * However, since kprobes itself also doesn't support NMI/MCE
 421          * code probing, it's not a problem.
 422          */
 423         text_poke_smp_batch(jump_poke_params, c);
 424 }
 425
 426 static void __kprobes setup_unoptimize_kprobe(struct text_poke_param *tprm,
 427                                               u8 *insn_buf,
 428                                               struct optimized_kprobe *op)
 429 {
 430         /* Set int3 to first byte for kprobes */
 431         insn_buf[0] = BREAKPOINT_INSTRUCTION;
 432         memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
 433
 434         tprm->addr = op->kp.addr;
 435         tprm->opcode = insn_buf;
 436         tprm->len = RELATIVEJUMP_SIZE;
 437 }
 438
 439 /*
 440  * Recover original instructions and breakpoints from relative jumps.
 441  * Caller must call with locking kprobe_mutex.
 442  */
 443 extern void arch_unoptimize_kprobes(struct list_head *oplist,
 444                                     struct list_head *done_list)
 445 {
 446         struct optimized_kprobe *op, *tmp;
 447         int c = 0;
 448
 449         list_for_each_entry_safe(op, tmp, oplist, list) {
 450                 /* Setup param */
 451                 setup_unoptimize_kprobe(&jump_poke_params[c],
 452                                         jump_poke_bufs[c].buf, op);
 453                 list_move(&op->list, done_list);
 454                 if (++c >= MAX_OPTIMIZE_PROBES)
 455                         break;
 456         }
 457
 458         /*
 459          * text_poke_smp doesn't support NMI/MCE code modifying.
 460          * However, since kprobes itself also doesn't support NMI/MCE
 461          * code probing, it's not a problem.
 462          */
 463         text_poke_smp_batch(jump_poke_params, c);
 464 }
 465
 466 /* Replace a relative jump with a breakpoint (int3).  */
 467 void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)
 468 {
 469         u8 buf[RELATIVEJUMP_SIZE];
 470
 471         /* Set int3 to first byte for kprobes */
 472         buf[0] = BREAKPOINT_INSTRUCTION;
 473         memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
 474         text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE);
 475 }
 476
 477 int  __kprobes
 478 setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
 479 {
 480         struct optimized_kprobe *op;
 481
 482         if (p->flags & KPROBE_FLAG_OPTIMIZED) {
 483                 /* This kprobe is really able to run optimized path. */
 484                 op = container_of(p, struct optimized_kprobe, kp);
 485                 /* Detour through copied instructions */
 486                 regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
 487                 if (!reenter)
 488                         reset_current_kprobe();
 489                 preempt_enable_no_resched();
 490                 return 1;
 491         }
 492         return 0;
 493 }
 494
 495 int __kprobes arch_init_optprobes(void)
 496 {
 497         /* Allocate code buffer and parameter array */
 498         jump_poke_bufs = kmalloc(sizeof(struct jump_poke_buffer) *
 499                                  MAX_OPTIMIZE_PROBES, GFP_KERNEL);
 500         if (!jump_poke_bufs)
 501                 return -ENOMEM;
 502
 503         jump_poke_params = kmalloc(sizeof(struct text_poke_param) *
 504                                    MAX_OPTIMIZE_PROBES, GFP_KERNEL);
 505         if (!jump_poke_params) {
 506                 kfree(jump_poke_bufs);
 507                 jump_poke_bufs = NULL;
 508                 return -ENOMEM;
 509         }
 510
 511         return 0;
 512 }