arch/powerpc/lib/code-patching.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  Copyright 2008 Michael Ellerman, IBM Corporation.
   4  */
   5
   6 #include <linux/kernel.h>
   7 #include <linux/kprobes.h>
   8 #include <linux/vmalloc.h>
   9 #include <linux/init.h>
  10 #include <linux/mm.h>
  11 #include <linux/cpuhotplug.h>
  12 #include <linux/slab.h>
  13 #include <linux/uaccess.h>
  14
  15 #include <asm/pgtable.h>
  16 #include <asm/tlbflush.h>
  17 #include <asm/page.h>
  18 #include <asm/code-patching.h>
  19 #include <asm/setup.h>
  20
  21 static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
  22                                unsigned int *patch_addr)
  23 {
  24         int err = 0;
  25
  26         __put_user_asm(instr, patch_addr, err, "stw");
  27         if (err)
  28                 return err;
  29
  30         asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
  31                                                             "r" (exec_addr));
  32
  33         return 0;
  34 }
  35
  36 int raw_patch_instruction(unsigned int *addr, unsigned int instr)
  37 {
  38         return __patch_instruction(addr, instr, addr);
  39 }
  40
  41 #ifdef CONFIG_STRICT_KERNEL_RWX
  42 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
  43
  44 static int text_area_cpu_up(unsigned int cpu)
  45 {
  46         struct vm_struct *area;
  47
  48         area = get_vm_area(PAGE_SIZE, VM_ALLOC);
  49         if (!area) {
  50                 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
  51                         cpu);
  52                 return -1;
  53         }
  54         this_cpu_write(text_poke_area, area);
  55
  56         return 0;
  57 }
  58
  59 static int text_area_cpu_down(unsigned int cpu)
  60 {
  61         free_vm_area(this_cpu_read(text_poke_area));
  62         return 0;
  63 }
  64
  65 /*
  66  * Run as a late init call. This allows all the boot time patching to be done
  67  * simply by patching the code, and then we're called here prior to
  68  * mark_rodata_ro(), which happens after all init calls are run. Although
  69  * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
  70  * it as being preferable to a kernel that will crash later when someone tries
  71  * to use patch_instruction().
  72  */
  73 static int __init setup_text_poke_area(void)
  74 {
  75         BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
  76                 "powerpc/text_poke:online", text_area_cpu_up,
  77                 text_area_cpu_down));
  78
  79         return 0;
  80 }
  81 late_initcall(setup_text_poke_area);
  82
  83 /*
  84  * This can be called for kernel text or a module.
  85  */
  86 static int map_patch_area(void *addr, unsigned long text_poke_addr)
  87 {
  88         unsigned long pfn;
  89         int err;
  90
  91         if (is_vmalloc_addr(addr))
  92                 pfn = vmalloc_to_pfn(addr);
  93         else
  94                 pfn = __pa_symbol(addr) >> PAGE_SHIFT;
  95
  96         err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
  97
  98         pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
  99         if (err)
 100                 return -1;
 101
 102         return 0;
 103 }
 104
 105 static inline int unmap_patch_area(unsigned long addr)
 106 {
 107         pte_t *ptep;
 108         pmd_t *pmdp;
 109         pud_t *pudp;
 110         pgd_t *pgdp;
 111
 112         pgdp = pgd_offset_k(addr);
 113         if (unlikely(!pgdp))
 114                 return -EINVAL;
 115
 116         pudp = pud_offset(pgdp, addr);
 117         if (unlikely(!pudp))
 118                 return -EINVAL;
 119
 120         pmdp = pmd_offset(pudp, addr);
 121         if (unlikely(!pmdp))
 122                 return -EINVAL;
 123
 124         ptep = pte_offset_kernel(pmdp, addr);
 125         if (unlikely(!ptep))
 126                 return -EINVAL;
 127
 128         pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);
 129
 130         /*
 131          * In hash, pte_clear flushes the tlb, in radix, we have to
 132          */
 133         pte_clear(&init_mm, addr, ptep);
 134         flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 135
 136         return 0;
 137 }
 138
 139 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 140 {
 141         int err;
 142         unsigned int *patch_addr = NULL;
 143         unsigned long flags;
 144         unsigned long text_poke_addr;
 145         unsigned long kaddr = (unsigned long)addr;
 146
 147         /*
 148          * During early early boot patch_instruction is called
 149          * when text_poke_area is not ready, but we still need
 150          * to allow patching. We just do the plain old patching
 151          */
 152         if (!this_cpu_read(text_poke_area))
 153                 return raw_patch_instruction(addr, instr);
 154
 155         local_irq_save(flags);
 156
 157         text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
 158         if (map_patch_area(addr, text_poke_addr)) {
 159                 err = -1;
 160                 goto out;
 161         }
 162
 163         patch_addr = (unsigned int *)(text_poke_addr) +
 164                         ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
 165
 166         __patch_instruction(addr, instr, patch_addr);
 167
 168         err = unmap_patch_area(text_poke_addr);
 169         if (err)
 170                 pr_warn("failed to unmap %lx\n", text_poke_addr);
 171
 172 out:
 173         local_irq_restore(flags);
 174
 175         return err;
 176 }
 177 #else /* !CONFIG_STRICT_KERNEL_RWX */
 178
 179 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
 180 {
 181         return raw_patch_instruction(addr, instr);
 182 }
 183
 184 #endif /* CONFIG_STRICT_KERNEL_RWX */
 185
 186 int patch_instruction(unsigned int *addr, unsigned int instr)
 187 {
 188         /* Make sure we aren't patching a freed init section */
 189         if (init_mem_is_free && init_section_contains(addr, 4)) {
 190                 pr_debug("Skipping init section patching addr: 0x%px\n", addr);
 191                 return 0;
 192         }
 193         return do_patch_instruction(addr, instr);
 194 }
 195 NOKPROBE_SYMBOL(patch_instruction);
 196
 197 int patch_branch(unsigned int *addr, unsigned long target, int flags)
 198 {
 199         return patch_instruction(addr, create_branch(addr, target, flags));
 200 }
 201
 202 bool is_offset_in_branch_range(long offset)
 203 {
 204         /*
 205          * Powerpc branch instruction is :
 206          *
 207          *  0         6                 30   31
 208          *  +---------+----------------+---+---+
 209          *  | opcode  |     LI         |AA |LK |
 210          *  +---------+----------------+---+---+
 211          *  Where AA = 0 and LK = 0
 212          *
 213          * LI is a signed 24 bits integer. The real branch offset is computed
 214          * by: imm32 = SignExtend(LI:'0b00', 32);
 215          *
 216          * So the maximum forward branch should be:
 217          *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
 218          * The maximum backward branch should be:
 219          *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
 220          */
 221         return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
 222 }
 223
 224 /*
 225  * Helper to check if a given instruction is a conditional branch
 226  * Derived from the conditional checks in analyse_instr()
 227  */
 228 bool is_conditional_branch(unsigned int instr)
 229 {
 230         unsigned int opcode = instr >> 26;
 231
 232         if (opcode == 16)       /* bc, bca, bcl, bcla */
 233                 return true;
 234         if (opcode == 19) {
 235                 switch ((instr >> 1) & 0x3ff) {
 236                 case 16:        /* bclr, bclrl */
 237                 case 528:       /* bcctr, bcctrl */
 238                 case 560:       /* bctar, bctarl */
 239                         return true;
 240                 }
 241         }
 242         return false;
 243 }
 244 NOKPROBE_SYMBOL(is_conditional_branch);
 245
 246 unsigned int create_branch(const unsigned int *addr,
 247                            unsigned long target, int flags)
 248 {
 249         unsigned int instruction;
 250         long offset;
 251
 252         offset = target;
 253         if (! (flags & BRANCH_ABSOLUTE))
 254                 offset = offset - (unsigned long)addr;
 255
 256         /* Check we can represent the target in the instruction format */
 257         if (!is_offset_in_branch_range(offset))
 258                 return 0;
 259
 260         /* Mask out the flags and target, so they don't step on each other. */
 261         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
 262
 263         return instruction;
 264 }
 265
 266 unsigned int create_cond_branch(const unsigned int *addr,
 267                                 unsigned long target, int flags)
 268 {
 269         unsigned int instruction;
 270         long offset;
 271
 272         offset = target;
 273         if (! (flags & BRANCH_ABSOLUTE))
 274                 offset = offset - (unsigned long)addr;
 275
 276         /* Check we can represent the target in the instruction format */
 277         if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
 278                 return 0;
 279
 280         /* Mask out the flags and target, so they don't step on each other. */
 281         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
 282
 283         return instruction;
 284 }
 285
 286 static unsigned int branch_opcode(unsigned int instr)
 287 {
 288         return (instr >> 26) & 0x3F;
 289 }
 290
 291 static int instr_is_branch_iform(unsigned int instr)
 292 {
 293         return branch_opcode(instr) == 18;
 294 }
 295
 296 static int instr_is_branch_bform(unsigned int instr)
 297 {
 298         return branch_opcode(instr) == 16;
 299 }
 300
 301 int instr_is_relative_branch(unsigned int instr)
 302 {
 303         if (instr & BRANCH_ABSOLUTE)
 304                 return 0;
 305
 306         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 307 }
 308
 309 int instr_is_relative_link_branch(unsigned int instr)
 310 {
 311         return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
 312 }
 313
 314 static unsigned long branch_iform_target(const unsigned int *instr)
 315 {
 316         signed long imm;
 317
 318         imm = *instr & 0x3FFFFFC;
 319
 320         /* If the top bit of the immediate value is set this is negative */
 321         if (imm & 0x2000000)
 322                 imm -= 0x4000000;
 323
 324         if ((*instr & BRANCH_ABSOLUTE) == 0)
 325                 imm += (unsigned long)instr;
 326
 327         return (unsigned long)imm;
 328 }
 329
 330 static unsigned long branch_bform_target(const unsigned int *instr)
 331 {
 332         signed long imm;
 333
 334         imm = *instr & 0xFFFC;
 335
 336         /* If the top bit of the immediate value is set this is negative */
 337         if (imm & 0x8000)
 338                 imm -= 0x10000;
 339
 340         if ((*instr & BRANCH_ABSOLUTE) == 0)
 341                 imm += (unsigned long)instr;
 342
 343         return (unsigned long)imm;
 344 }
 345
 346 unsigned long branch_target(const unsigned int *instr)
 347 {
 348         if (instr_is_branch_iform(*instr))
 349                 return branch_iform_target(instr);
 350         else if (instr_is_branch_bform(*instr))
 351                 return branch_bform_target(instr);
 352
 353         return 0;
 354 }
 355
 356 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 357 {
 358         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 359                 return branch_target(instr) == addr;
 360
 361         return 0;
 362 }
 363
 364 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 365 {
 366         unsigned long target;
 367
 368         target = branch_target(src);
 369
 370         if (instr_is_branch_iform(*src))
 371                 return create_branch(dest, target, *src);
 372         else if (instr_is_branch_bform(*src))
 373                 return create_cond_branch(dest, target, *src);
 374
 375         return 0;
 376 }
 377
 378 #ifdef CONFIG_PPC_BOOK3E_64
 379 void __patch_exception(int exc, unsigned long addr)
 380 {
 381         extern unsigned int interrupt_base_book3e;
 382         unsigned int *ibase = &interrupt_base_book3e;
 383
 384         /* Our exceptions vectors start with a NOP and -then- a branch
 385          * to deal with single stepping from userspace which stops on
 386          * the second instruction. Thus we need to patch the second
 387          * instruction of the exception, not the first one
 388          */
 389
 390         patch_branch(ibase + (exc / 4) + 1, addr, 0);
 391 }
 392 #endif
 393
 394 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 395
 396 static void __init test_trampoline(void)
 397 {
 398         asm ("nop;\n");
 399 }
 400
 401 #define check(x)        \
 402         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 403
 404 static void __init test_branch_iform(void)
 405 {
 406         unsigned int instr;
 407         unsigned long addr;
 408
 409         addr = (unsigned long)&instr;
 410
 411         /* The simplest case, branch to self, no flags */
 412         check(instr_is_branch_iform(0x48000000));
 413         /* All bits of target set, and flags */
 414         check(instr_is_branch_iform(0x4bffffff));
 415         /* High bit of opcode set, which is wrong */
 416         check(!instr_is_branch_iform(0xcbffffff));
 417         /* Middle bits of opcode set, which is wrong */
 418         check(!instr_is_branch_iform(0x7bffffff));
 419
 420         /* Simplest case, branch to self with link */
 421         check(instr_is_branch_iform(0x48000001));
 422         /* All bits of targets set */
 423         check(instr_is_branch_iform(0x4bfffffd));
 424         /* Some bits of targets set */
 425         check(instr_is_branch_iform(0x4bff00fd));
 426         /* Must be a valid branch to start with */
 427         check(!instr_is_branch_iform(0x7bfffffd));
 428
 429         /* Absolute branch to 0x100 */
 430         instr = 0x48000103;
 431         check(instr_is_branch_to_addr(&instr, 0x100));
 432         /* Absolute branch to 0x420fc */
 433         instr = 0x480420ff;
 434         check(instr_is_branch_to_addr(&instr, 0x420fc));
 435         /* Maximum positive relative branch, + 20MB - 4B */
 436         instr = 0x49fffffc;
 437         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 438         /* Smallest negative relative branch, - 4B */
 439         instr = 0x4bfffffc;
 440         check(instr_is_branch_to_addr(&instr, addr - 4));
 441         /* Largest negative relative branch, - 32 MB */
 442         instr = 0x4a000000;
 443         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 444
 445         /* Branch to self, with link */
 446         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 447         check(instr_is_branch_to_addr(&instr, addr));
 448
 449         /* Branch to self - 0x100, with link */
 450         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 451         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 452
 453         /* Branch to self + 0x100, no link */
 454         instr = create_branch(&instr, addr + 0x100, 0);
 455         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 456
 457         /* Maximum relative negative offset, - 32 MB */
 458         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 459         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 460
 461         /* Out of range relative negative offset, - 32 MB + 4*/
 462         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 463         check(instr == 0);
 464
 465         /* Out of range relative positive offset, + 32 MB */
 466         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 467         check(instr == 0);
 468
 469         /* Unaligned target */
 470         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 471         check(instr == 0);
 472
 473         /* Check flags are masked correctly */
 474         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 475         check(instr_is_branch_to_addr(&instr, addr));
 476         check(instr == 0x48000000);
 477 }
 478
 479 static void __init test_create_function_call(void)
 480 {
 481         unsigned int *iptr;
 482         unsigned long dest;
 483
 484         /* Check we can create a function call */
 485         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 486         dest = ppc_function_entry(test_create_function_call);
 487         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 488         check(instr_is_branch_to_addr(iptr, dest));
 489 }
 490
 491 static void __init test_branch_bform(void)
 492 {
 493         unsigned long addr;
 494         unsigned int *iptr, instr, flags;
 495
 496         iptr = &instr;
 497         addr = (unsigned long)iptr;
 498
 499         /* The simplest case, branch to self, no flags */
 500         check(instr_is_branch_bform(0x40000000));
 501         /* All bits of target set, and flags */
 502         check(instr_is_branch_bform(0x43ffffff));
 503         /* High bit of opcode set, which is wrong */
 504         check(!instr_is_branch_bform(0xc3ffffff));
 505         /* Middle bits of opcode set, which is wrong */
 506         check(!instr_is_branch_bform(0x7bffffff));
 507
 508         /* Absolute conditional branch to 0x100 */
 509         instr = 0x43ff0103;
 510         check(instr_is_branch_to_addr(&instr, 0x100));
 511         /* Absolute conditional branch to 0x20fc */
 512         instr = 0x43ff20ff;
 513         check(instr_is_branch_to_addr(&instr, 0x20fc));
 514         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 515         instr = 0x43ff7ffc;
 516         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 517         /* Smallest negative relative conditional branch, - 4B */
 518         instr = 0x43fffffc;
 519         check(instr_is_branch_to_addr(&instr, addr - 4));
 520         /* Largest negative relative conditional branch, - 32 KB */
 521         instr = 0x43ff8000;
 522         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 523
 524         /* All condition code bits set & link */
 525         flags = 0x3ff000 | BRANCH_SET_LINK;
 526
 527         /* Branch to self */
 528         instr = create_cond_branch(iptr, addr, flags);
 529         check(instr_is_branch_to_addr(&instr, addr));
 530
 531         /* Branch to self - 0x100 */
 532         instr = create_cond_branch(iptr, addr - 0x100, flags);
 533         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 534
 535         /* Branch to self + 0x100 */
 536         instr = create_cond_branch(iptr, addr + 0x100, flags);
 537         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 538
 539         /* Maximum relative negative offset, - 32 KB */
 540         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 541         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 542
 543         /* Out of range relative negative offset, - 32 KB + 4*/
 544         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 545         check(instr == 0);
 546
 547         /* Out of range relative positive offset, + 32 KB */
 548         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 549         check(instr == 0);
 550
 551         /* Unaligned target */
 552         instr = create_cond_branch(iptr, addr + 3, flags);
 553         check(instr == 0);
 554
 555         /* Check flags are masked correctly */
 556         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 557         check(instr_is_branch_to_addr(&instr, addr));
 558         check(instr == 0x43FF0000);
 559 }
 560
 561 static void __init test_translate_branch(void)
 562 {
 563         unsigned long addr;
 564         unsigned int *p, *q;
 565         void *buf;
 566
 567         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 568         check(buf);
 569         if (!buf)
 570                 return;
 571
 572         /* Simple case, branch to self moved a little */
 573         p = buf;
 574         addr = (unsigned long)p;
 575         patch_branch(p, addr, 0);
 576         check(instr_is_branch_to_addr(p, addr));
 577         q = p + 1;
 578         patch_instruction(q, translate_branch(q, p));
 579         check(instr_is_branch_to_addr(q, addr));
 580
 581         /* Maximum negative case, move b . to addr + 32 MB */
 582         p = buf;
 583         addr = (unsigned long)p;
 584         patch_branch(p, addr, 0);
 585         q = buf + 0x2000000;
 586         patch_instruction(q, translate_branch(q, p));
 587         check(instr_is_branch_to_addr(p, addr));
 588         check(instr_is_branch_to_addr(q, addr));
 589         check(*q == 0x4a000000);
 590
 591         /* Maximum positive case, move x to x - 32 MB + 4 */
 592         p = buf + 0x2000000;
 593         addr = (unsigned long)p;
 594         patch_branch(p, addr, 0);
 595         q = buf + 4;
 596         patch_instruction(q, translate_branch(q, p));
 597         check(instr_is_branch_to_addr(p, addr));
 598         check(instr_is_branch_to_addr(q, addr));
 599         check(*q == 0x49fffffc);
 600
 601         /* Jump to x + 16 MB moved to x + 20 MB */
 602         p = buf;
 603         addr = 0x1000000 + (unsigned long)buf;
 604         patch_branch(p, addr, BRANCH_SET_LINK);
 605         q = buf + 0x1400000;
 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         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 611         p = buf + 0x1000000;
 612         addr = 0x2000000 + (unsigned long)buf;
 613         patch_branch(p, addr, 0);
 614         q = buf + 4;
 615         patch_instruction(q, translate_branch(q, p));
 616         check(instr_is_branch_to_addr(p, addr));
 617         check(instr_is_branch_to_addr(q, addr));
 618
 619
 620         /* Conditional branch tests */
 621
 622         /* Simple case, branch to self moved a little */
 623         p = buf;
 624         addr = (unsigned long)p;
 625         patch_instruction(p, create_cond_branch(p, addr, 0));
 626         check(instr_is_branch_to_addr(p, addr));
 627         q = p + 1;
 628         patch_instruction(q, translate_branch(q, p));
 629         check(instr_is_branch_to_addr(q, addr));
 630
 631         /* Maximum negative case, move b . to addr + 32 KB */
 632         p = buf;
 633         addr = (unsigned long)p;
 634         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 635         q = buf + 0x8000;
 636         patch_instruction(q, translate_branch(q, p));
 637         check(instr_is_branch_to_addr(p, addr));
 638         check(instr_is_branch_to_addr(q, addr));
 639         check(*q == 0x43ff8000);
 640
 641         /* Maximum positive case, move x to x - 32 KB + 4 */
 642         p = buf + 0x8000;
 643         addr = (unsigned long)p;
 644         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 645         q = buf + 4;
 646         patch_instruction(q, translate_branch(q, p));
 647         check(instr_is_branch_to_addr(p, addr));
 648         check(instr_is_branch_to_addr(q, addr));
 649         check(*q == 0x43ff7ffc);
 650
 651         /* Jump to x + 12 KB moved to x + 20 KB */
 652         p = buf;
 653         addr = 0x3000 + (unsigned long)buf;
 654         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 655         q = buf + 0x5000;
 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         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 661         p = buf + 0x2000;
 662         addr = 0x4000 + (unsigned long)buf;
 663         patch_instruction(p, create_cond_branch(p, addr, 0));
 664         q = buf + 4;
 665         patch_instruction(q, translate_branch(q, p));
 666         check(instr_is_branch_to_addr(p, addr));
 667         check(instr_is_branch_to_addr(q, addr));
 668
 669         /* Free the buffer we were using */
 670         vfree(buf);
 671 }
 672
 673 static int __init test_code_patching(void)
 674 {
 675         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 676
 677         test_branch_iform();
 678         test_branch_bform();
 679         test_create_function_call();
 680         test_translate_branch();
 681
 682         return 0;
 683 }
 684 late_initcall(test_code_patching);
 685
 686 #endif /* CONFIG_CODE_PATCHING_SELFTEST */