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/vmalloc.h>
  12 #include <linux/init.h>
  13 #include <asm/page.h>
  14 #include <asm/code-patching.h>
  15
  16
  17 void patch_instruction(unsigned int *addr, unsigned int instr)
  18 {
  19         *addr = instr;
  20         asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
  21 }
  22
  23 void patch_branch(unsigned int *addr, unsigned long target, int flags)
  24 {
  25         patch_instruction(addr, create_branch(addr, target, flags));
  26 }
  27
  28 unsigned int create_branch(const unsigned int *addr,
  29                            unsigned long target, int flags)
  30 {
  31         unsigned int instruction;
  32         long offset;
  33
  34         offset = target;
  35         if (! (flags & BRANCH_ABSOLUTE))
  36                 offset = offset - (unsigned long)addr;
  37
  38         /* Check we can represent the target in the instruction format */
  39         if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
  40                 return 0;
  41
  42         /* Mask out the flags and target, so they don't step on each other. */
  43         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
  44
  45         return instruction;
  46 }
  47
  48 unsigned int create_cond_branch(const unsigned int *addr,
  49                                 unsigned long target, int flags)
  50 {
  51         unsigned int instruction;
  52         long offset;
  53
  54         offset = target;
  55         if (! (flags & BRANCH_ABSOLUTE))
  56                 offset = offset - (unsigned long)addr;
  57
  58         /* Check we can represent the target in the instruction format */
  59         if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
  60                 return 0;
  61
  62         /* Mask out the flags and target, so they don't step on each other. */
  63         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
  64
  65         return instruction;
  66 }
  67
  68 static unsigned int branch_opcode(unsigned int instr)
  69 {
  70         return (instr >> 26) & 0x3F;
  71 }
  72
  73 static int instr_is_branch_iform(unsigned int instr)
  74 {
  75         return branch_opcode(instr) == 18;
  76 }
  77
  78 static int instr_is_branch_bform(unsigned int instr)
  79 {
  80         return branch_opcode(instr) == 16;
  81 }
  82
  83 int instr_is_relative_branch(unsigned int instr)
  84 {
  85         if (instr & BRANCH_ABSOLUTE)
  86                 return 0;
  87
  88         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
  89 }
  90
  91 static unsigned long branch_iform_target(const unsigned int *instr)
  92 {
  93         signed long imm;
  94
  95         imm = *instr & 0x3FFFFFC;
  96
  97         /* If the top bit of the immediate value is set this is negative */
  98         if (imm & 0x2000000)
  99                 imm -= 0x4000000;
 100
 101         if ((*instr & BRANCH_ABSOLUTE) == 0)
 102                 imm += (unsigned long)instr;
 103
 104         return (unsigned long)imm;
 105 }
 106
 107 static unsigned long branch_bform_target(const unsigned int *instr)
 108 {
 109         signed long imm;
 110
 111         imm = *instr & 0xFFFC;
 112
 113         /* If the top bit of the immediate value is set this is negative */
 114         if (imm & 0x8000)
 115                 imm -= 0x10000;
 116
 117         if ((*instr & BRANCH_ABSOLUTE) == 0)
 118                 imm += (unsigned long)instr;
 119
 120         return (unsigned long)imm;
 121 }
 122
 123 unsigned long branch_target(const unsigned int *instr)
 124 {
 125         if (instr_is_branch_iform(*instr))
 126                 return branch_iform_target(instr);
 127         else if (instr_is_branch_bform(*instr))
 128                 return branch_bform_target(instr);
 129
 130         return 0;
 131 }
 132
 133 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 134 {
 135         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 136                 return branch_target(instr) == addr;
 137
 138         return 0;
 139 }
 140
 141 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 142 {
 143         unsigned long target;
 144
 145         target = branch_target(src);
 146
 147         if (instr_is_branch_iform(*src))
 148                 return create_branch(dest, target, *src);
 149         else if (instr_is_branch_bform(*src))
 150                 return create_cond_branch(dest, target, *src);
 151
 152         return 0;
 153 }
 154
 155
 156 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 157
 158 static void __init test_trampoline(void)
 159 {
 160         asm ("nop;\n");
 161 }
 162
 163 #define check(x)        \
 164         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 165
 166 static void __init test_branch_iform(void)
 167 {
 168         unsigned int instr;
 169         unsigned long addr;
 170
 171         addr = (unsigned long)&instr;
 172
 173         /* The simplest case, branch to self, no flags */
 174         check(instr_is_branch_iform(0x48000000));
 175         /* All bits of target set, and flags */
 176         check(instr_is_branch_iform(0x4bffffff));
 177         /* High bit of opcode set, which is wrong */
 178         check(!instr_is_branch_iform(0xcbffffff));
 179         /* Middle bits of opcode set, which is wrong */
 180         check(!instr_is_branch_iform(0x7bffffff));
 181
 182         /* Simplest case, branch to self with link */
 183         check(instr_is_branch_iform(0x48000001));
 184         /* All bits of targets set */
 185         check(instr_is_branch_iform(0x4bfffffd));
 186         /* Some bits of targets set */
 187         check(instr_is_branch_iform(0x4bff00fd));
 188         /* Must be a valid branch to start with */
 189         check(!instr_is_branch_iform(0x7bfffffd));
 190
 191         /* Absolute branch to 0x100 */
 192         instr = 0x48000103;
 193         check(instr_is_branch_to_addr(&instr, 0x100));
 194         /* Absolute branch to 0x420fc */
 195         instr = 0x480420ff;
 196         check(instr_is_branch_to_addr(&instr, 0x420fc));
 197         /* Maximum positive relative branch, + 20MB - 4B */
 198         instr = 0x49fffffc;
 199         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 200         /* Smallest negative relative branch, - 4B */
 201         instr = 0x4bfffffc;
 202         check(instr_is_branch_to_addr(&instr, addr - 4));
 203         /* Largest negative relative branch, - 32 MB */
 204         instr = 0x4a000000;
 205         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 206
 207         /* Branch to self, with link */
 208         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 209         check(instr_is_branch_to_addr(&instr, addr));
 210
 211         /* Branch to self - 0x100, with link */
 212         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 213         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 214
 215         /* Branch to self + 0x100, no link */
 216         instr = create_branch(&instr, addr + 0x100, 0);
 217         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 218
 219         /* Maximum relative negative offset, - 32 MB */
 220         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 221         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 222
 223         /* Out of range relative negative offset, - 32 MB + 4*/
 224         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 225         check(instr == 0);
 226
 227         /* Out of range relative positive offset, + 32 MB */
 228         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 229         check(instr == 0);
 230
 231         /* Unaligned target */
 232         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 233         check(instr == 0);
 234
 235         /* Check flags are masked correctly */
 236         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 237         check(instr_is_branch_to_addr(&instr, addr));
 238         check(instr == 0x48000000);
 239 }
 240
 241 static void __init test_create_function_call(void)
 242 {
 243         unsigned int *iptr;
 244         unsigned long dest;
 245
 246         /* Check we can create a function call */
 247         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 248         dest = ppc_function_entry(test_create_function_call);
 249         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 250         check(instr_is_branch_to_addr(iptr, dest));
 251 }
 252
 253 static void __init test_branch_bform(void)
 254 {
 255         unsigned long addr;
 256         unsigned int *iptr, instr, flags;
 257
 258         iptr = &instr;
 259         addr = (unsigned long)iptr;
 260
 261         /* The simplest case, branch to self, no flags */
 262         check(instr_is_branch_bform(0x40000000));
 263         /* All bits of target set, and flags */
 264         check(instr_is_branch_bform(0x43ffffff));
 265         /* High bit of opcode set, which is wrong */
 266         check(!instr_is_branch_bform(0xc3ffffff));
 267         /* Middle bits of opcode set, which is wrong */
 268         check(!instr_is_branch_bform(0x7bffffff));
 269
 270         /* Absolute conditional branch to 0x100 */
 271         instr = 0x43ff0103;
 272         check(instr_is_branch_to_addr(&instr, 0x100));
 273         /* Absolute conditional branch to 0x20fc */
 274         instr = 0x43ff20ff;
 275         check(instr_is_branch_to_addr(&instr, 0x20fc));
 276         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 277         instr = 0x43ff7ffc;
 278         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 279         /* Smallest negative relative conditional branch, - 4B */
 280         instr = 0x43fffffc;
 281         check(instr_is_branch_to_addr(&instr, addr - 4));
 282         /* Largest negative relative conditional branch, - 32 KB */
 283         instr = 0x43ff8000;
 284         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 285
 286         /* All condition code bits set & link */
 287         flags = 0x3ff000 | BRANCH_SET_LINK;
 288
 289         /* Branch to self */
 290         instr = create_cond_branch(iptr, addr, flags);
 291         check(instr_is_branch_to_addr(&instr, addr));
 292
 293         /* Branch to self - 0x100 */
 294         instr = create_cond_branch(iptr, addr - 0x100, flags);
 295         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 296
 297         /* Branch to self + 0x100 */
 298         instr = create_cond_branch(iptr, addr + 0x100, flags);
 299         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 300
 301         /* Maximum relative negative offset, - 32 KB */
 302         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 303         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 304
 305         /* Out of range relative negative offset, - 32 KB + 4*/
 306         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 307         check(instr == 0);
 308
 309         /* Out of range relative positive offset, + 32 KB */
 310         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 311         check(instr == 0);
 312
 313         /* Unaligned target */
 314         instr = create_cond_branch(iptr, addr + 3, flags);
 315         check(instr == 0);
 316
 317         /* Check flags are masked correctly */
 318         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 319         check(instr_is_branch_to_addr(&instr, addr));
 320         check(instr == 0x43FF0000);
 321 }
 322
 323 static void __init test_translate_branch(void)
 324 {
 325         unsigned long addr;
 326         unsigned int *p, *q;
 327         void *buf;
 328
 329         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 330         check(buf);
 331         if (!buf)
 332                 return;
 333
 334         /* Simple case, branch to self moved a little */
 335         p = buf;
 336         addr = (unsigned long)p;
 337         patch_branch(p, addr, 0);
 338         check(instr_is_branch_to_addr(p, addr));
 339         q = p + 1;
 340         patch_instruction(q, translate_branch(q, p));
 341         check(instr_is_branch_to_addr(q, addr));
 342
 343         /* Maximum negative case, move b . to addr + 32 MB */
 344         p = buf;
 345         addr = (unsigned long)p;
 346         patch_branch(p, addr, 0);
 347         q = buf + 0x2000000;
 348         patch_instruction(q, translate_branch(q, p));
 349         check(instr_is_branch_to_addr(p, addr));
 350         check(instr_is_branch_to_addr(q, addr));
 351         check(*q == 0x4a000000);
 352
 353         /* Maximum positive case, move x to x - 32 MB + 4 */
 354         p = buf + 0x2000000;
 355         addr = (unsigned long)p;
 356         patch_branch(p, addr, 0);
 357         q = buf + 4;
 358         patch_instruction(q, translate_branch(q, p));
 359         check(instr_is_branch_to_addr(p, addr));
 360         check(instr_is_branch_to_addr(q, addr));
 361         check(*q == 0x49fffffc);
 362
 363         /* Jump to x + 16 MB moved to x + 20 MB */
 364         p = buf;
 365         addr = 0x1000000 + (unsigned long)buf;
 366         patch_branch(p, addr, BRANCH_SET_LINK);
 367         q = buf + 0x1400000;
 368         patch_instruction(q, translate_branch(q, p));
 369         check(instr_is_branch_to_addr(p, addr));
 370         check(instr_is_branch_to_addr(q, addr));
 371
 372         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 373         p = buf + 0x1000000;
 374         addr = 0x2000000 + (unsigned long)buf;
 375         patch_branch(p, addr, 0);
 376         q = buf + 4;
 377         patch_instruction(q, translate_branch(q, p));
 378         check(instr_is_branch_to_addr(p, addr));
 379         check(instr_is_branch_to_addr(q, addr));
 380
 381
 382         /* Conditional branch tests */
 383
 384         /* Simple case, branch to self moved a little */
 385         p = buf;
 386         addr = (unsigned long)p;
 387         patch_instruction(p, create_cond_branch(p, addr, 0));
 388         check(instr_is_branch_to_addr(p, addr));
 389         q = p + 1;
 390         patch_instruction(q, translate_branch(q, p));
 391         check(instr_is_branch_to_addr(q, addr));
 392
 393         /* Maximum negative case, move b . to addr + 32 KB */
 394         p = buf;
 395         addr = (unsigned long)p;
 396         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 397         q = buf + 0x8000;
 398         patch_instruction(q, translate_branch(q, p));
 399         check(instr_is_branch_to_addr(p, addr));
 400         check(instr_is_branch_to_addr(q, addr));
 401         check(*q == 0x43ff8000);
 402
 403         /* Maximum positive case, move x to x - 32 KB + 4 */
 404         p = buf + 0x8000;
 405         addr = (unsigned long)p;
 406         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 407         q = buf + 4;
 408         patch_instruction(q, translate_branch(q, p));
 409         check(instr_is_branch_to_addr(p, addr));
 410         check(instr_is_branch_to_addr(q, addr));
 411         check(*q == 0x43ff7ffc);
 412
 413         /* Jump to x + 12 KB moved to x + 20 KB */
 414         p = buf;
 415         addr = 0x3000 + (unsigned long)buf;
 416         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 417         q = buf + 0x5000;
 418         patch_instruction(q, translate_branch(q, p));
 419         check(instr_is_branch_to_addr(p, addr));
 420         check(instr_is_branch_to_addr(q, addr));
 421
 422         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 423         p = buf + 0x2000;
 424         addr = 0x4000 + (unsigned long)buf;
 425         patch_instruction(p, create_cond_branch(p, addr, 0));
 426         q = buf + 4;
 427         patch_instruction(q, translate_branch(q, p));
 428         check(instr_is_branch_to_addr(p, addr));
 429         check(instr_is_branch_to_addr(q, addr));
 430
 431         /* Free the buffer we were using */
 432         vfree(buf);
 433 }
 434
 435 static int __init test_code_patching(void)
 436 {
 437         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 438
 439         test_branch_iform();
 440         test_branch_bform();
 441         test_create_function_call();
 442         test_translate_branch();
 443
 444         return 0;
 445 }
 446 late_initcall(test_code_patching);
 447
 448 #endif /* CONFIG_CODE_PATCHING_SELFTEST */