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