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 #include <asm/sections.h>
  26
  27 static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
  28                                unsigned int *patch_addr)
  29 {
  30         int err;
  31
  32         __put_user_size(instr, patch_addr, 4, err);
  33         if (err)
  34                 return err;
  35
  36         asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
  37                                                             "r" (exec_addr));
  38
  39         return 0;
  40 }
  41
  42 int raw_patch_instruction(unsigned int *addr, unsigned int instr)
  43 {
  44         return __patch_instruction(addr, instr, addr);
  45 }
  46
  47 #ifdef CONFIG_STRICT_KERNEL_RWX
  48 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
  49
  50 static int text_area_cpu_up(unsigned int cpu)
  51 {
  52         struct vm_struct *area;
  53
  54         area = get_vm_area(PAGE_SIZE, VM_ALLOC);
  55         if (!area) {
  56                 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
  57                         cpu);
  58                 return -1;
  59         }
  60         this_cpu_write(text_poke_area, area);
  61
  62         return 0;
  63 }
  64
  65 static int text_area_cpu_down(unsigned int cpu)
  66 {
  67         free_vm_area(this_cpu_read(text_poke_area));
  68         return 0;
  69 }
  70
  71 /*
  72  * Run as a late init call. This allows all the boot time patching to be done
  73  * simply by patching the code, and then we're called here prior to
  74  * mark_rodata_ro(), which happens after all init calls are run. Although
  75  * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
  76  * it as being preferable to a kernel that will crash later when someone tries
  77  * to use patch_instruction().
  78  */
  79 static int __init setup_text_poke_area(void)
  80 {
  81         BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
  82                 "powerpc/text_poke:online", text_area_cpu_up,
  83                 text_area_cpu_down));
  84
  85         return 0;
  86 }
  87 late_initcall(setup_text_poke_area);
  88
  89 /*
  90  * This can be called for kernel text or a module.
  91  */
  92 static int map_patch_area(void *addr, unsigned long text_poke_addr)
  93 {
  94         unsigned long pfn;
  95         int err;
  96
  97         if (is_vmalloc_addr(addr))
  98                 pfn = vmalloc_to_pfn(addr);
  99         else
 100                 pfn = __pa_symbol(addr) >> PAGE_SHIFT;
 101
 102         err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT),
 103                                 pgprot_val(PAGE_KERNEL));
 104
 105         pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
 106         if (err)
 107                 return -1;
 108
 109         return 0;
 110 }
 111
 112 static inline int unmap_patch_area(unsigned long addr)
 113 {
 114         pte_t *ptep;
 115         pmd_t *pmdp;
 116         pud_t *pudp;
 117         pgd_t *pgdp;
 118
 119         pgdp = pgd_offset_k(addr);
 120         if (unlikely(!pgdp))
 121                 return -EINVAL;
 122
 123         pudp = pud_offset(pgdp, addr);
 124         if (unlikely(!pudp))
 125                 return -EINVAL;
 126
 127         pmdp = pmd_offset(pudp, addr);
 128         if (unlikely(!pmdp))
 129                 return -EINVAL;
 130
 131         ptep = pte_offset_kernel(pmdp, addr);
 132         if (unlikely(!ptep))
 133                 return -EINVAL;
 134
 135         pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);
 136
 137         /*
 138          * In hash, pte_clear flushes the tlb, in radix, we have to
 139          */
 140         pte_clear(&init_mm, addr, ptep);
 141         flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 142
 143         return 0;
 144 }
 145
 146 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 147 {
 148         int err;
 149         unsigned int *patch_addr = NULL;
 150         unsigned long flags;
 151         unsigned long text_poke_addr;
 152         unsigned long kaddr = (unsigned long)addr;
 153
 154         /*
 155          * During early early boot patch_instruction is called
 156          * when text_poke_area is not ready, but we still need
 157          * to allow patching. We just do the plain old patching
 158          */
 159         if (!this_cpu_read(text_poke_area))
 160                 return raw_patch_instruction(addr, instr);
 161
 162         local_irq_save(flags);
 163
 164         text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
 165         if (map_patch_area(addr, text_poke_addr)) {
 166                 err = -1;
 167                 goto out;
 168         }
 169
 170         patch_addr = (unsigned int *)(text_poke_addr) +
 171                         ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
 172
 173         __patch_instruction(addr, instr, patch_addr);
 174
 175         err = unmap_patch_area(text_poke_addr);
 176         if (err)
 177                 pr_warn("failed to unmap %lx\n", text_poke_addr);
 178
 179 out:
 180         local_irq_restore(flags);
 181
 182         return err;
 183 }
 184 #else /* !CONFIG_STRICT_KERNEL_RWX */
 185
 186 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 187 {
 188         return raw_patch_instruction(addr, instr);
 189 }
 190
 191 #endif /* CONFIG_STRICT_KERNEL_RWX */
 192
 193 int patch_instruction(unsigned int *addr, unsigned int instr)
 194 {
 195         /* Make sure we aren't patching a freed init section */
 196         if (init_mem_is_free && init_section_contains(addr, 4)) {
 197                 pr_debug("Skipping init section patching addr: 0x%px\n", addr);
 198                 return 0;
 199         }
 200         return do_patch_instruction(addr, instr);
 201 }
 202 NOKPROBE_SYMBOL(patch_instruction);
 203
 204 int patch_branch(unsigned int *addr, unsigned long target, int flags)
 205 {
 206         return patch_instruction(addr, create_branch(addr, target, flags));
 207 }
 208
 209 int patch_branch_site(s32 *site, unsigned long target, int flags)
 210 {
 211         unsigned int *addr;
 212
 213         addr = (unsigned int *)((unsigned long)site + *site);
 214         return patch_instruction(addr, create_branch(addr, target, flags));
 215 }
 216
 217 int patch_instruction_site(s32 *site, unsigned int instr)
 218 {
 219         unsigned int *addr;
 220
 221         addr = (unsigned int *)((unsigned long)site + *site);
 222         return patch_instruction(addr, instr);
 223 }
 224
 225 bool is_offset_in_branch_range(long offset)
 226 {
 227         /*
 228          * Powerpc branch instruction is :
 229          *
 230          *  0         6                 30   31
 231          *  +---------+----------------+---+---+
 232          *  | opcode  |     LI         |AA |LK |
 233          *  +---------+----------------+---+---+
 234          *  Where AA = 0 and LK = 0
 235          *
 236          * LI is a signed 24 bits integer. The real branch offset is computed
 237          * by: imm32 = SignExtend(LI:'0b00', 32);
 238          *
 239          * So the maximum forward branch should be:
 240          *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
 241          * The maximum backward branch should be:
 242          *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
 243          */
 244         return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
 245 }
 246
 247 bool is_offset_in_cond_branch_range(long offset)
 248 {
 249         return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
 250 }
 251
 252 /*
 253  * Helper to check if a given instruction is a conditional branch
 254  * Derived from the conditional checks in analyse_instr()
 255  */
 256 bool is_conditional_branch(unsigned int instr)
 257 {
 258         unsigned int opcode = instr >> 26;
 259
 260         if (opcode == 16)       /* bc, bca, bcl, bcla */
 261                 return true;
 262         if (opcode == 19) {
 263                 switch ((instr >> 1) & 0x3ff) {
 264                 case 16:        /* bclr, bclrl */
 265                 case 528:       /* bcctr, bcctrl */
 266                 case 560:       /* bctar, bctarl */
 267                         return true;
 268                 }
 269         }
 270         return false;
 271 }
 272 NOKPROBE_SYMBOL(is_conditional_branch);
 273
 274 unsigned int create_branch(const unsigned int *addr,
 275                            unsigned long target, int flags)
 276 {
 277         unsigned int instruction;
 278         long offset;
 279
 280         offset = target;
 281         if (! (flags & BRANCH_ABSOLUTE))
 282                 offset = offset - (unsigned long)addr;
 283
 284         /* Check we can represent the target in the instruction format */
 285         if (!is_offset_in_branch_range(offset))
 286                 return 0;
 287
 288         /* Mask out the flags and target, so they don't step on each other. */
 289         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
 290
 291         return instruction;
 292 }
 293
 294 unsigned int create_cond_branch(const unsigned int *addr,
 295                                 unsigned long target, int flags)
 296 {
 297         unsigned int instruction;
 298         long offset;
 299
 300         offset = target;
 301         if (! (flags & BRANCH_ABSOLUTE))
 302                 offset = offset - (unsigned long)addr;
 303
 304         /* Check we can represent the target in the instruction format */
 305         if (!is_offset_in_cond_branch_range(offset))
 306                 return 0;
 307
 308         /* Mask out the flags and target, so they don't step on each other. */
 309         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
 310
 311         return instruction;
 312 }
 313
 314 static unsigned int branch_opcode(unsigned int instr)
 315 {
 316         return (instr >> 26) & 0x3F;
 317 }
 318
 319 static int instr_is_branch_iform(unsigned int instr)
 320 {
 321         return branch_opcode(instr) == 18;
 322 }
 323
 324 static int instr_is_branch_bform(unsigned int instr)
 325 {
 326         return branch_opcode(instr) == 16;
 327 }
 328
 329 int instr_is_relative_branch(unsigned int instr)
 330 {
 331         if (instr & BRANCH_ABSOLUTE)
 332                 return 0;
 333
 334         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 335 }
 336
 337 int instr_is_relative_link_branch(unsigned int instr)
 338 {
 339         return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
 340 }
 341
 342 static unsigned long branch_iform_target(const unsigned int *instr)
 343 {
 344         signed long imm;
 345
 346         imm = *instr & 0x3FFFFFC;
 347
 348         /* If the top bit of the immediate value is set this is negative */
 349         if (imm & 0x2000000)
 350                 imm -= 0x4000000;
 351
 352         if ((*instr & BRANCH_ABSOLUTE) == 0)
 353                 imm += (unsigned long)instr;
 354
 355         return (unsigned long)imm;
 356 }
 357
 358 static unsigned long branch_bform_target(const unsigned int *instr)
 359 {
 360         signed long imm;
 361
 362         imm = *instr & 0xFFFC;
 363
 364         /* If the top bit of the immediate value is set this is negative */
 365         if (imm & 0x8000)
 366                 imm -= 0x10000;
 367
 368         if ((*instr & BRANCH_ABSOLUTE) == 0)
 369                 imm += (unsigned long)instr;
 370
 371         return (unsigned long)imm;
 372 }
 373
 374 unsigned long branch_target(const unsigned int *instr)
 375 {
 376         if (instr_is_branch_iform(*instr))
 377                 return branch_iform_target(instr);
 378         else if (instr_is_branch_bform(*instr))
 379                 return branch_bform_target(instr);
 380
 381         return 0;
 382 }
 383
 384 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 385 {
 386         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 387                 return branch_target(instr) == addr;
 388
 389         return 0;
 390 }
 391
 392 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 393 {
 394         unsigned long target;
 395
 396         target = branch_target(src);
 397
 398         if (instr_is_branch_iform(*src))
 399                 return create_branch(dest, target, *src);
 400         else if (instr_is_branch_bform(*src))
 401                 return create_cond_branch(dest, target, *src);
 402
 403         return 0;
 404 }
 405
 406 #ifdef CONFIG_PPC_BOOK3E_64
 407 void __patch_exception(int exc, unsigned long addr)
 408 {
 409         extern unsigned int interrupt_base_book3e;
 410         unsigned int *ibase = &interrupt_base_book3e;
 411
 412         /* Our exceptions vectors start with a NOP and -then- a branch
 413          * to deal with single stepping from userspace which stops on
 414          * the second instruction. Thus we need to patch the second
 415          * instruction of the exception, not the first one
 416          */
 417
 418         patch_branch(ibase + (exc / 4) + 1, addr, 0);
 419 }
 420 #endif
 421
 422 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 423
 424 static void __init test_trampoline(void)
 425 {
 426         asm ("nop;\n");
 427 }
 428
 429 #define check(x)        \
 430         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 431
 432 static void __init test_branch_iform(void)
 433 {
 434         unsigned int instr;
 435         unsigned long addr;
 436
 437         addr = (unsigned long)&instr;
 438
 439         /* The simplest case, branch to self, no flags */
 440         check(instr_is_branch_iform(0x48000000));
 441         /* All bits of target set, and flags */
 442         check(instr_is_branch_iform(0x4bffffff));
 443         /* High bit of opcode set, which is wrong */
 444         check(!instr_is_branch_iform(0xcbffffff));
 445         /* Middle bits of opcode set, which is wrong */
 446         check(!instr_is_branch_iform(0x7bffffff));
 447
 448         /* Simplest case, branch to self with link */
 449         check(instr_is_branch_iform(0x48000001));
 450         /* All bits of targets set */
 451         check(instr_is_branch_iform(0x4bfffffd));
 452         /* Some bits of targets set */
 453         check(instr_is_branch_iform(0x4bff00fd));
 454         /* Must be a valid branch to start with */
 455         check(!instr_is_branch_iform(0x7bfffffd));
 456
 457         /* Absolute branch to 0x100 */
 458         instr = 0x48000103;
 459         check(instr_is_branch_to_addr(&instr, 0x100));
 460         /* Absolute branch to 0x420fc */
 461         instr = 0x480420ff;
 462         check(instr_is_branch_to_addr(&instr, 0x420fc));
 463         /* Maximum positive relative branch, + 20MB - 4B */
 464         instr = 0x49fffffc;
 465         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 466         /* Smallest negative relative branch, - 4B */
 467         instr = 0x4bfffffc;
 468         check(instr_is_branch_to_addr(&instr, addr - 4));
 469         /* Largest negative relative branch, - 32 MB */
 470         instr = 0x4a000000;
 471         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 472
 473         /* Branch to self, with link */
 474         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 475         check(instr_is_branch_to_addr(&instr, addr));
 476
 477         /* Branch to self - 0x100, with link */
 478         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 479         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 480
 481         /* Branch to self + 0x100, no link */
 482         instr = create_branch(&instr, addr + 0x100, 0);
 483         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 484
 485         /* Maximum relative negative offset, - 32 MB */
 486         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 487         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 488
 489         /* Out of range relative negative offset, - 32 MB + 4*/
 490         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 491         check(instr == 0);
 492
 493         /* Out of range relative positive offset, + 32 MB */
 494         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 495         check(instr == 0);
 496
 497         /* Unaligned target */
 498         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 499         check(instr == 0);
 500
 501         /* Check flags are masked correctly */
 502         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 503         check(instr_is_branch_to_addr(&instr, addr));
 504         check(instr == 0x48000000);
 505 }
 506
 507 static void __init test_create_function_call(void)
 508 {
 509         unsigned int *iptr;
 510         unsigned long dest;
 511
 512         /* Check we can create a function call */
 513         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 514         dest = ppc_function_entry(test_create_function_call);
 515         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 516         check(instr_is_branch_to_addr(iptr, dest));
 517 }
 518
 519 static void __init test_branch_bform(void)
 520 {
 521         unsigned long addr;
 522         unsigned int *iptr, instr, flags;
 523
 524         iptr = &instr;
 525         addr = (unsigned long)iptr;
 526
 527         /* The simplest case, branch to self, no flags */
 528         check(instr_is_branch_bform(0x40000000));
 529         /* All bits of target set, and flags */
 530         check(instr_is_branch_bform(0x43ffffff));
 531         /* High bit of opcode set, which is wrong */
 532         check(!instr_is_branch_bform(0xc3ffffff));
 533         /* Middle bits of opcode set, which is wrong */
 534         check(!instr_is_branch_bform(0x7bffffff));
 535
 536         /* Absolute conditional branch to 0x100 */
 537         instr = 0x43ff0103;
 538         check(instr_is_branch_to_addr(&instr, 0x100));
 539         /* Absolute conditional branch to 0x20fc */
 540         instr = 0x43ff20ff;
 541         check(instr_is_branch_to_addr(&instr, 0x20fc));
 542         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 543         instr = 0x43ff7ffc;
 544         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 545         /* Smallest negative relative conditional branch, - 4B */
 546         instr = 0x43fffffc;
 547         check(instr_is_branch_to_addr(&instr, addr - 4));
 548         /* Largest negative relative conditional branch, - 32 KB */
 549         instr = 0x43ff8000;
 550         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 551
 552         /* All condition code bits set & link */
 553         flags = 0x3ff000 | BRANCH_SET_LINK;
 554
 555         /* Branch to self */
 556         instr = create_cond_branch(iptr, addr, flags);
 557         check(instr_is_branch_to_addr(&instr, addr));
 558
 559         /* Branch to self - 0x100 */
 560         instr = create_cond_branch(iptr, addr - 0x100, flags);
 561         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 562
 563         /* Branch to self + 0x100 */
 564         instr = create_cond_branch(iptr, addr + 0x100, flags);
 565         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 566
 567         /* Maximum relative negative offset, - 32 KB */
 568         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 569         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 570
 571         /* Out of range relative negative offset, - 32 KB + 4*/
 572         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 573         check(instr == 0);
 574
 575         /* Out of range relative positive offset, + 32 KB */
 576         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 577         check(instr == 0);
 578
 579         /* Unaligned target */
 580         instr = create_cond_branch(iptr, addr + 3, flags);
 581         check(instr == 0);
 582
 583         /* Check flags are masked correctly */
 584         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 585         check(instr_is_branch_to_addr(&instr, addr));
 586         check(instr == 0x43FF0000);
 587 }
 588
 589 static void __init test_translate_branch(void)
 590 {
 591         unsigned long addr;
 592         unsigned int *p, *q;
 593         void *buf;
 594
 595         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 596         check(buf);
 597         if (!buf)
 598                 return;
 599
 600         /* Simple case, branch to self moved a little */
 601         p = buf;
 602         addr = (unsigned long)p;
 603         patch_branch(p, addr, 0);
 604         check(instr_is_branch_to_addr(p, addr));
 605         q = p + 1;
 606         patch_instruction(q, translate_branch(q, p));
 607         check(instr_is_branch_to_addr(q, addr));
 608
 609         /* Maximum negative case, move b . to addr + 32 MB */
 610         p = buf;
 611         addr = (unsigned long)p;
 612         patch_branch(p, addr, 0);
 613         q = buf + 0x2000000;
 614         patch_instruction(q, translate_branch(q, p));
 615         check(instr_is_branch_to_addr(p, addr));
 616         check(instr_is_branch_to_addr(q, addr));
 617         check(*q == 0x4a000000);
 618
 619         /* Maximum positive case, move x to x - 32 MB + 4 */
 620         p = buf + 0x2000000;
 621         addr = (unsigned long)p;
 622         patch_branch(p, addr, 0);
 623         q = buf + 4;
 624         patch_instruction(q, translate_branch(q, p));
 625         check(instr_is_branch_to_addr(p, addr));
 626         check(instr_is_branch_to_addr(q, addr));
 627         check(*q == 0x49fffffc);
 628
 629         /* Jump to x + 16 MB moved to x + 20 MB */
 630         p = buf;
 631         addr = 0x1000000 + (unsigned long)buf;
 632         patch_branch(p, addr, BRANCH_SET_LINK);
 633         q = buf + 0x1400000;
 634         patch_instruction(q, translate_branch(q, p));
 635         check(instr_is_branch_to_addr(p, addr));
 636         check(instr_is_branch_to_addr(q, addr));
 637
 638         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 639         p = buf + 0x1000000;
 640         addr = 0x2000000 + (unsigned long)buf;
 641         patch_branch(p, addr, 0);
 642         q = buf + 4;
 643         patch_instruction(q, translate_branch(q, p));
 644         check(instr_is_branch_to_addr(p, addr));
 645         check(instr_is_branch_to_addr(q, addr));
 646
 647
 648         /* Conditional branch tests */
 649
 650         /* Simple case, branch to self moved a little */
 651         p = buf;
 652         addr = (unsigned long)p;
 653         patch_instruction(p, create_cond_branch(p, addr, 0));
 654         check(instr_is_branch_to_addr(p, addr));
 655         q = p + 1;
 656         patch_instruction(q, translate_branch(q, p));
 657         check(instr_is_branch_to_addr(q, addr));
 658
 659         /* Maximum negative case, move b . to addr + 32 KB */
 660         p = buf;
 661         addr = (unsigned long)p;
 662         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 663         q = buf + 0x8000;
 664         patch_instruction(q, translate_branch(q, p));
 665         check(instr_is_branch_to_addr(p, addr));
 666         check(instr_is_branch_to_addr(q, addr));
 667         check(*q == 0x43ff8000);
 668
 669         /* Maximum positive case, move x to x - 32 KB + 4 */
 670         p = buf + 0x8000;
 671         addr = (unsigned long)p;
 672         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 673         q = buf + 4;
 674         patch_instruction(q, translate_branch(q, p));
 675         check(instr_is_branch_to_addr(p, addr));
 676         check(instr_is_branch_to_addr(q, addr));
 677         check(*q == 0x43ff7ffc);
 678
 679         /* Jump to x + 12 KB moved to x + 20 KB */
 680         p = buf;
 681         addr = 0x3000 + (unsigned long)buf;
 682         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 683         q = buf + 0x5000;
 684         patch_instruction(q, translate_branch(q, p));
 685         check(instr_is_branch_to_addr(p, addr));
 686         check(instr_is_branch_to_addr(q, addr));
 687
 688         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 689         p = buf + 0x2000;
 690         addr = 0x4000 + (unsigned long)buf;
 691         patch_instruction(p, create_cond_branch(p, addr, 0));
 692         q = buf + 4;
 693         patch_instruction(q, translate_branch(q, p));
 694         check(instr_is_branch_to_addr(p, addr));
 695         check(instr_is_branch_to_addr(q, addr));
 696
 697         /* Free the buffer we were using */
 698         vfree(buf);
 699 }
 700
 701 static int __init test_code_patching(void)
 702 {
 703         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 704
 705         test_branch_iform();
 706         test_branch_bform();
 707         test_create_function_call();
 708         test_translate_branch();
 709
 710         return 0;
 711 }
 712 late_initcall(test_code_patching);
 713
 714 #endif /* CONFIG_CODE_PATCHING_SELFTEST */