arch/powerpc/lib/code-patching.c

   1 /*
   2  *  Copyright 2008 Michael Ellerman, IBM Corporation.
   3  *
   4  *  This program is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU General Public License
   6  *  as published by the Free Software Foundation; either version
   7  *  2 of the License, or (at your option) any later version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/kprobes.h>
  12 #include <linux/vmalloc.h>
  13 #include <linux/init.h>
  14 #include <linux/mm.h>
  15 #include <linux/cpuhotplug.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/kprobes.h>
  19
  20 #include <asm/pgtable.h>
  21 #include <asm/tlbflush.h>
  22 #include <asm/page.h>
  23 #include <asm/code-patching.h>
  24 #include <asm/setup.h>
  25
  26 static int __patch_instruction(unsigned int *addr, unsigned int instr)
  27 {
  28         int err;
  29
  30         __put_user_size(instr, addr, 4, err);
  31         if (err)
  32                 return err;
  33
  34         asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" :: "r" (addr));
  35
  36         return 0;
  37 }
  38
  39 #ifdef CONFIG_STRICT_KERNEL_RWX
  40 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
  41
  42 static int text_area_cpu_up(unsigned int cpu)
  43 {
  44         struct vm_struct *area;
  45
  46         area = get_vm_area(PAGE_SIZE, VM_ALLOC);
  47         if (!area) {
  48                 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
  49                         cpu);
  50                 return -1;
  51         }
  52         this_cpu_write(text_poke_area, area);
  53
  54         return 0;
  55 }
  56
  57 static int text_area_cpu_down(unsigned int cpu)
  58 {
  59         free_vm_area(this_cpu_read(text_poke_area));
  60         return 0;
  61 }
  62
  63 /*
  64  * Run as a late init call. This allows all the boot time patching to be done
  65  * simply by patching the code, and then we're called here prior to
  66  * mark_rodata_ro(), which happens after all init calls are run. Although
  67  * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
  68  * it as being preferable to a kernel that will crash later when someone tries
  69  * to use patch_instruction().
  70  */
  71 static int __init setup_text_poke_area(void)
  72 {
  73         BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
  74                 "powerpc/text_poke:online", text_area_cpu_up,
  75                 text_area_cpu_down));
  76
  77         return 0;
  78 }
  79 late_initcall(setup_text_poke_area);
  80
  81 /*
  82  * This can be called for kernel text or a module.
  83  */
  84 static int map_patch_area(void *addr, unsigned long text_poke_addr)
  85 {
  86         unsigned long pfn;
  87         int err;
  88
  89         if (is_vmalloc_addr(addr))
  90                 pfn = vmalloc_to_pfn(addr);
  91         else
  92                 pfn = __pa_symbol(addr) >> PAGE_SHIFT;
  93
  94         err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT),
  95                                 pgprot_val(PAGE_KERNEL));
  96
  97         pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
  98         if (err)
  99                 return -1;
 100
 101         return 0;
 102 }
 103
 104 static inline int unmap_patch_area(unsigned long addr)
 105 {
 106         pte_t *ptep;
 107         pmd_t *pmdp;
 108         pud_t *pudp;
 109         pgd_t *pgdp;
 110
 111         pgdp = pgd_offset_k(addr);
 112         if (unlikely(!pgdp))
 113                 return -EINVAL;
 114
 115         pudp = pud_offset(pgdp, addr);
 116         if (unlikely(!pudp))
 117                 return -EINVAL;
 118
 119         pmdp = pmd_offset(pudp, addr);
 120         if (unlikely(!pmdp))
 121                 return -EINVAL;
 122
 123         ptep = pte_offset_kernel(pmdp, addr);
 124         if (unlikely(!ptep))
 125                 return -EINVAL;
 126
 127         pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);
 128
 129         /*
 130          * In hash, pte_clear flushes the tlb, in radix, we have to
 131          */
 132         pte_clear(&init_mm, addr, ptep);
 133         flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 134
 135         return 0;
 136 }
 137
 138 int patch_instruction(unsigned int *addr, unsigned int instr)
 139 {
 140         int err;
 141         unsigned int *dest = NULL;
 142         unsigned long flags;
 143         unsigned long text_poke_addr;
 144         unsigned long kaddr = (unsigned long)addr;
 145
 146         /*
 147          * During early early boot patch_instruction is called
 148          * when text_poke_area is not ready, but we still need
 149          * to allow patching. We just do the plain old patching
 150          */
 151         if (!this_cpu_read(*PTRRELOC(&text_poke_area)))
 152                 return __patch_instruction(addr, instr);
 153
 154         local_irq_save(flags);
 155
 156         text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
 157         if (map_patch_area(addr, text_poke_addr)) {
 158                 err = -1;
 159                 goto out;
 160         }
 161
 162         dest = (unsigned int *)(text_poke_addr) +
 163                         ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
 164
 165         /*
 166          * We use __put_user_size so that we can handle faults while
 167          * writing to dest and return err to handle faults gracefully
 168          */
 169         __put_user_size(instr, dest, 4, err);
 170         if (!err)
 171                 asm ("dcbst 0, %0; sync; icbi 0,%0; icbi 0,%1; sync; isync"
 172                         ::"r" (dest), "r"(addr));
 173
 174         err = unmap_patch_area(text_poke_addr);
 175         if (err)
 176                 pr_warn("failed to unmap %lx\n", text_poke_addr);
 177
 178 out:
 179         local_irq_restore(flags);
 180
 181         return err;
 182 }
 183 #else /* !CONFIG_STRICT_KERNEL_RWX */
 184
 185 int patch_instruction(unsigned int *addr, unsigned int instr)
 186 {
 187         return __patch_instruction(addr, instr);
 188 }
 189
 190 #endif /* CONFIG_STRICT_KERNEL_RWX */
 191 NOKPROBE_SYMBOL(patch_instruction);
 192
 193 int patch_branch(unsigned int *addr, unsigned long target, int flags)
 194 {
 195         return patch_instruction(addr, create_branch(addr, target, flags));
 196 }
 197
 198 bool is_offset_in_branch_range(long offset)
 199 {
 200         /*
 201          * Powerpc branch instruction is :
 202          *
 203          *  0         6                 30   31
 204          *  +---------+----------------+---+---+
 205          *  | opcode  |     LI         |AA |LK |
 206          *  +---------+----------------+---+---+
 207          *  Where AA = 0 and LK = 0
 208          *
 209          * LI is a signed 24 bits integer. The real branch offset is computed
 210          * by: imm32 = SignExtend(LI:'0b00', 32);
 211          *
 212          * So the maximum forward branch should be:
 213          *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
 214          * The maximum backward branch should be:
 215          *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
 216          */
 217         return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
 218 }
 219
 220 /*
 221  * Helper to check if a given instruction is a conditional branch
 222  * Derived from the conditional checks in analyse_instr()
 223  */
 224 bool is_conditional_branch(unsigned int instr)
 225 {
 226         unsigned int opcode = instr >> 26;
 227
 228         if (opcode == 16)       /* bc, bca, bcl, bcla */
 229                 return true;
 230         if (opcode == 19) {
 231                 switch ((instr >> 1) & 0x3ff) {
 232                 case 16:        /* bclr, bclrl */
 233                 case 528:       /* bcctr, bcctrl */
 234                 case 560:       /* bctar, bctarl */
 235                         return true;
 236                 }
 237         }
 238         return false;
 239 }
 240 NOKPROBE_SYMBOL(is_conditional_branch);
 241
 242 unsigned int create_branch(const unsigned int *addr,
 243                            unsigned long target, int flags)
 244 {
 245         unsigned int instruction;
 246         long offset;
 247
 248         offset = target;
 249         if (! (flags & BRANCH_ABSOLUTE))
 250                 offset = offset - (unsigned long)addr;
 251
 252         /* Check we can represent the target in the instruction format */
 253         if (!is_offset_in_branch_range(offset))
 254                 return 0;
 255
 256         /* Mask out the flags and target, so they don't step on each other. */
 257         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
 258
 259         return instruction;
 260 }
 261
 262 unsigned int create_cond_branch(const unsigned int *addr,
 263                                 unsigned long target, int flags)
 264 {
 265         unsigned int instruction;
 266         long offset;
 267
 268         offset = target;
 269         if (! (flags & BRANCH_ABSOLUTE))
 270                 offset = offset - (unsigned long)addr;
 271
 272         /* Check we can represent the target in the instruction format */
 273         if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
 274                 return 0;
 275
 276         /* Mask out the flags and target, so they don't step on each other. */
 277         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
 278
 279         return instruction;
 280 }
 281
 282 static unsigned int branch_opcode(unsigned int instr)
 283 {
 284         return (instr >> 26) & 0x3F;
 285 }
 286
 287 static int instr_is_branch_iform(unsigned int instr)
 288 {
 289         return branch_opcode(instr) == 18;
 290 }
 291
 292 static int instr_is_branch_bform(unsigned int instr)
 293 {
 294         return branch_opcode(instr) == 16;
 295 }
 296
 297 int instr_is_relative_branch(unsigned int instr)
 298 {
 299         if (instr & BRANCH_ABSOLUTE)
 300                 return 0;
 301
 302         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 303 }
 304
 305 static unsigned long branch_iform_target(const unsigned int *instr)
 306 {
 307         signed long imm;
 308
 309         imm = *instr & 0x3FFFFFC;
 310
 311         /* If the top bit of the immediate value is set this is negative */
 312         if (imm & 0x2000000)
 313                 imm -= 0x4000000;
 314
 315         if ((*instr & BRANCH_ABSOLUTE) == 0)
 316                 imm += (unsigned long)instr;
 317
 318         return (unsigned long)imm;
 319 }
 320
 321 static unsigned long branch_bform_target(const unsigned int *instr)
 322 {
 323         signed long imm;
 324
 325         imm = *instr & 0xFFFC;
 326
 327         /* If the top bit of the immediate value is set this is negative */
 328         if (imm & 0x8000)
 329                 imm -= 0x10000;
 330
 331         if ((*instr & BRANCH_ABSOLUTE) == 0)
 332                 imm += (unsigned long)instr;
 333
 334         return (unsigned long)imm;
 335 }
 336
 337 unsigned long branch_target(const unsigned int *instr)
 338 {
 339         if (instr_is_branch_iform(*instr))
 340                 return branch_iform_target(instr);
 341         else if (instr_is_branch_bform(*instr))
 342                 return branch_bform_target(instr);
 343
 344         return 0;
 345 }
 346
 347 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 348 {
 349         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 350                 return branch_target(instr) == addr;
 351
 352         return 0;
 353 }
 354
 355 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 356 {
 357         unsigned long target;
 358
 359         target = branch_target(src);
 360
 361         if (instr_is_branch_iform(*src))
 362                 return create_branch(dest, target, *src);
 363         else if (instr_is_branch_bform(*src))
 364                 return create_cond_branch(dest, target, *src);
 365
 366         return 0;
 367 }
 368
 369 #ifdef CONFIG_PPC_BOOK3E_64
 370 void __patch_exception(int exc, unsigned long addr)
 371 {
 372         extern unsigned int interrupt_base_book3e;
 373         unsigned int *ibase = &interrupt_base_book3e;
 374
 375         /* Our exceptions vectors start with a NOP and -then- a branch
 376          * to deal with single stepping from userspace which stops on
 377          * the second instruction. Thus we need to patch the second
 378          * instruction of the exception, not the first one
 379          */
 380
 381         patch_branch(ibase + (exc / 4) + 1, addr, 0);
 382 }
 383 #endif
 384
 385 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 386
 387 static void __init test_trampoline(void)
 388 {
 389         asm ("nop;\n");
 390 }
 391
 392 #define check(x)        \
 393         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 394
 395 static void __init test_branch_iform(void)
 396 {
 397         unsigned int instr;
 398         unsigned long addr;
 399
 400         addr = (unsigned long)&instr;
 401
 402         /* The simplest case, branch to self, no flags */
 403         check(instr_is_branch_iform(0x48000000));
 404         /* All bits of target set, and flags */
 405         check(instr_is_branch_iform(0x4bffffff));
 406         /* High bit of opcode set, which is wrong */
 407         check(!instr_is_branch_iform(0xcbffffff));
 408         /* Middle bits of opcode set, which is wrong */
 409         check(!instr_is_branch_iform(0x7bffffff));
 410
 411         /* Simplest case, branch to self with link */
 412         check(instr_is_branch_iform(0x48000001));
 413         /* All bits of targets set */
 414         check(instr_is_branch_iform(0x4bfffffd));
 415         /* Some bits of targets set */
 416         check(instr_is_branch_iform(0x4bff00fd));
 417         /* Must be a valid branch to start with */
 418         check(!instr_is_branch_iform(0x7bfffffd));
 419
 420         /* Absolute branch to 0x100 */
 421         instr = 0x48000103;
 422         check(instr_is_branch_to_addr(&instr, 0x100));
 423         /* Absolute branch to 0x420fc */
 424         instr = 0x480420ff;
 425         check(instr_is_branch_to_addr(&instr, 0x420fc));
 426         /* Maximum positive relative branch, + 20MB - 4B */
 427         instr = 0x49fffffc;
 428         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 429         /* Smallest negative relative branch, - 4B */
 430         instr = 0x4bfffffc;
 431         check(instr_is_branch_to_addr(&instr, addr - 4));
 432         /* Largest negative relative branch, - 32 MB */
 433         instr = 0x4a000000;
 434         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 435
 436         /* Branch to self, with link */
 437         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 438         check(instr_is_branch_to_addr(&instr, addr));
 439
 440         /* Branch to self - 0x100, with link */
 441         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 442         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 443
 444         /* Branch to self + 0x100, no link */
 445         instr = create_branch(&instr, addr + 0x100, 0);
 446         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 447
 448         /* Maximum relative negative offset, - 32 MB */
 449         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 450         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 451
 452         /* Out of range relative negative offset, - 32 MB + 4*/
 453         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 454         check(instr == 0);
 455
 456         /* Out of range relative positive offset, + 32 MB */
 457         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 458         check(instr == 0);
 459
 460         /* Unaligned target */
 461         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 462         check(instr == 0);
 463
 464         /* Check flags are masked correctly */
 465         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 466         check(instr_is_branch_to_addr(&instr, addr));
 467         check(instr == 0x48000000);
 468 }
 469
 470 static void __init test_create_function_call(void)
 471 {
 472         unsigned int *iptr;
 473         unsigned long dest;
 474
 475         /* Check we can create a function call */
 476         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 477         dest = ppc_function_entry(test_create_function_call);
 478         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 479         check(instr_is_branch_to_addr(iptr, dest));
 480 }
 481
 482 static void __init test_branch_bform(void)
 483 {
 484         unsigned long addr;
 485         unsigned int *iptr, instr, flags;
 486
 487         iptr = &instr;
 488         addr = (unsigned long)iptr;
 489
 490         /* The simplest case, branch to self, no flags */
 491         check(instr_is_branch_bform(0x40000000));
 492         /* All bits of target set, and flags */
 493         check(instr_is_branch_bform(0x43ffffff));
 494         /* High bit of opcode set, which is wrong */
 495         check(!instr_is_branch_bform(0xc3ffffff));
 496         /* Middle bits of opcode set, which is wrong */
 497         check(!instr_is_branch_bform(0x7bffffff));
 498
 499         /* Absolute conditional branch to 0x100 */
 500         instr = 0x43ff0103;
 501         check(instr_is_branch_to_addr(&instr, 0x100));
 502         /* Absolute conditional branch to 0x20fc */
 503         instr = 0x43ff20ff;
 504         check(instr_is_branch_to_addr(&instr, 0x20fc));
 505         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 506         instr = 0x43ff7ffc;
 507         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 508         /* Smallest negative relative conditional branch, - 4B */
 509         instr = 0x43fffffc;
 510         check(instr_is_branch_to_addr(&instr, addr - 4));
 511         /* Largest negative relative conditional branch, - 32 KB */
 512         instr = 0x43ff8000;
 513         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 514
 515         /* All condition code bits set & link */
 516         flags = 0x3ff000 | BRANCH_SET_LINK;
 517
 518         /* Branch to self */
 519         instr = create_cond_branch(iptr, addr, flags);
 520         check(instr_is_branch_to_addr(&instr, addr));
 521
 522         /* Branch to self - 0x100 */
 523         instr = create_cond_branch(iptr, addr - 0x100, flags);
 524         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 525
 526         /* Branch to self + 0x100 */
 527         instr = create_cond_branch(iptr, addr + 0x100, flags);
 528         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 529
 530         /* Maximum relative negative offset, - 32 KB */
 531         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 532         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 533
 534         /* Out of range relative negative offset, - 32 KB + 4*/
 535         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 536         check(instr == 0);
 537
 538         /* Out of range relative positive offset, + 32 KB */
 539         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 540         check(instr == 0);
 541
 542         /* Unaligned target */
 543         instr = create_cond_branch(iptr, addr + 3, flags);
 544         check(instr == 0);
 545
 546         /* Check flags are masked correctly */
 547         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 548         check(instr_is_branch_to_addr(&instr, addr));
 549         check(instr == 0x43FF0000);
 550 }
 551
 552 static void __init test_translate_branch(void)
 553 {
 554         unsigned long addr;
 555         unsigned int *p, *q;
 556         void *buf;
 557
 558         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 559         check(buf);
 560         if (!buf)
 561                 return;
 562
 563         /* Simple case, branch to self moved a little */
 564         p = buf;
 565         addr = (unsigned long)p;
 566         patch_branch(p, addr, 0);
 567         check(instr_is_branch_to_addr(p, addr));
 568         q = p + 1;
 569         patch_instruction(q, translate_branch(q, p));
 570         check(instr_is_branch_to_addr(q, addr));
 571
 572         /* Maximum negative case, move b . to addr + 32 MB */
 573         p = buf;
 574         addr = (unsigned long)p;
 575         patch_branch(p, addr, 0);
 576         q = buf + 0x2000000;
 577         patch_instruction(q, translate_branch(q, p));
 578         check(instr_is_branch_to_addr(p, addr));
 579         check(instr_is_branch_to_addr(q, addr));
 580         check(*q == 0x4a000000);
 581
 582         /* Maximum positive case, move x to x - 32 MB + 4 */
 583         p = buf + 0x2000000;
 584         addr = (unsigned long)p;
 585         patch_branch(p, addr, 0);
 586         q = buf + 4;
 587         patch_instruction(q, translate_branch(q, p));
 588         check(instr_is_branch_to_addr(p, addr));
 589         check(instr_is_branch_to_addr(q, addr));
 590         check(*q == 0x49fffffc);
 591
 592         /* Jump to x + 16 MB moved to x + 20 MB */
 593         p = buf;
 594         addr = 0x1000000 + (unsigned long)buf;
 595         patch_branch(p, addr, BRANCH_SET_LINK);
 596         q = buf + 0x1400000;
 597         patch_instruction(q, translate_branch(q, p));
 598         check(instr_is_branch_to_addr(p, addr));
 599         check(instr_is_branch_to_addr(q, addr));
 600
 601         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 602         p = buf + 0x1000000;
 603         addr = 0x2000000 + (unsigned long)buf;
 604         patch_branch(p, addr, 0);
 605         q = buf + 4;
 606         patch_instruction(q, translate_branch(q, p));
 607         check(instr_is_branch_to_addr(p, addr));
 608         check(instr_is_branch_to_addr(q, addr));
 609
 610
 611         /* Conditional branch tests */
 612
 613         /* Simple case, branch to self moved a little */
 614         p = buf;
 615         addr = (unsigned long)p;
 616         patch_instruction(p, create_cond_branch(p, addr, 0));
 617         check(instr_is_branch_to_addr(p, addr));
 618         q = p + 1;
 619         patch_instruction(q, translate_branch(q, p));
 620         check(instr_is_branch_to_addr(q, addr));
 621
 622         /* Maximum negative case, move b . to addr + 32 KB */
 623         p = buf;
 624         addr = (unsigned long)p;
 625         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 626         q = buf + 0x8000;
 627         patch_instruction(q, translate_branch(q, p));
 628         check(instr_is_branch_to_addr(p, addr));
 629         check(instr_is_branch_to_addr(q, addr));
 630         check(*q == 0x43ff8000);
 631
 632         /* Maximum positive case, move x to x - 32 KB + 4 */
 633         p = buf + 0x8000;
 634         addr = (unsigned long)p;
 635         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 636         q = buf + 4;
 637         patch_instruction(q, translate_branch(q, p));
 638         check(instr_is_branch_to_addr(p, addr));
 639         check(instr_is_branch_to_addr(q, addr));
 640         check(*q == 0x43ff7ffc);
 641
 642         /* Jump to x + 12 KB moved to x + 20 KB */
 643         p = buf;
 644         addr = 0x3000 + (unsigned long)buf;
 645         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 646         q = buf + 0x5000;
 647         patch_instruction(q, translate_branch(q, p));
 648         check(instr_is_branch_to_addr(p, addr));
 649         check(instr_is_branch_to_addr(q, addr));
 650
 651         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 652         p = buf + 0x2000;
 653         addr = 0x4000 + (unsigned long)buf;
 654         patch_instruction(p, create_cond_branch(p, addr, 0));
 655         q = buf + 4;
 656         patch_instruction(q, translate_branch(q, p));
 657         check(instr_is_branch_to_addr(p, addr));
 658         check(instr_is_branch_to_addr(q, addr));
 659
 660         /* Free the buffer we were using */
 661         vfree(buf);
 662 }
 663
 664 static int __init test_code_patching(void)
 665 {
 666         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 667
 668         test_branch_iform();
 669         test_branch_bform();
 670         test_create_function_call();
 671         test_translate_branch();
 672
 673         return 0;
 674 }
 675 late_initcall(test_code_patching);
 676
 677 #endif /* CONFIG_CODE_PATCHING_SELFTEST */