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