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 #include <asm/uaccess.h>
  17
  18
  19 int patch_instruction(unsigned int *addr, unsigned int instr)
  20 {
  21         int err;
  22
  23         __put_user_size(instr, addr, 4, err);
  24         if (err)
  25                 return err;
  26         asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
  27         return 0;
  28 }
  29
  30 int patch_branch(unsigned int *addr, unsigned long target, int flags)
  31 {
  32         return patch_instruction(addr, create_branch(addr, target, flags));
  33 }
  34
  35 unsigned int create_branch(const unsigned int *addr,
  36                            unsigned long target, int flags)
  37 {
  38         unsigned int instruction;
  39         long offset;
  40
  41         offset = target;
  42         if (! (flags & BRANCH_ABSOLUTE))
  43                 offset = offset - (unsigned long)addr;
  44
  45         /* Check we can represent the target in the instruction format */
  46         if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
  47                 return 0;
  48
  49         /* Mask out the flags and target, so they don't step on each other. */
  50         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
  51
  52         return instruction;
  53 }
  54
  55 unsigned int create_cond_branch(const unsigned int *addr,
  56                                 unsigned long target, int flags)
  57 {
  58         unsigned int instruction;
  59         long offset;
  60
  61         offset = target;
  62         if (! (flags & BRANCH_ABSOLUTE))
  63                 offset = offset - (unsigned long)addr;
  64
  65         /* Check we can represent the target in the instruction format */
  66         if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
  67                 return 0;
  68
  69         /* Mask out the flags and target, so they don't step on each other. */
  70         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
  71
  72         return instruction;
  73 }
  74
  75 static unsigned int branch_opcode(unsigned int instr)
  76 {
  77         return (instr >> 26) & 0x3F;
  78 }
  79
  80 static int instr_is_branch_iform(unsigned int instr)
  81 {
  82         return branch_opcode(instr) == 18;
  83 }
  84
  85 static int instr_is_branch_bform(unsigned int instr)
  86 {
  87         return branch_opcode(instr) == 16;
  88 }
  89
  90 int instr_is_relative_branch(unsigned int instr)
  91 {
  92         if (instr & BRANCH_ABSOLUTE)
  93                 return 0;
  94
  95         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
  96 }
  97
  98 static unsigned long branch_iform_target(const unsigned int *instr)
  99 {
 100         signed long imm;
 101
 102         imm = *instr & 0x3FFFFFC;
 103
 104         /* If the top bit of the immediate value is set this is negative */
 105         if (imm & 0x2000000)
 106                 imm -= 0x4000000;
 107
 108         if ((*instr & BRANCH_ABSOLUTE) == 0)
 109                 imm += (unsigned long)instr;
 110
 111         return (unsigned long)imm;
 112 }
 113
 114 static unsigned long branch_bform_target(const unsigned int *instr)
 115 {
 116         signed long imm;
 117
 118         imm = *instr & 0xFFFC;
 119
 120         /* If the top bit of the immediate value is set this is negative */
 121         if (imm & 0x8000)
 122                 imm -= 0x10000;
 123
 124         if ((*instr & BRANCH_ABSOLUTE) == 0)
 125                 imm += (unsigned long)instr;
 126
 127         return (unsigned long)imm;
 128 }
 129
 130 unsigned long branch_target(const unsigned int *instr)
 131 {
 132         if (instr_is_branch_iform(*instr))
 133                 return branch_iform_target(instr);
 134         else if (instr_is_branch_bform(*instr))
 135                 return branch_bform_target(instr);
 136
 137         return 0;
 138 }
 139
 140 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 141 {
 142         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 143                 return branch_target(instr) == addr;
 144
 145         return 0;
 146 }
 147
 148 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 149 {
 150         unsigned long target;
 151
 152         target = branch_target(src);
 153
 154         if (instr_is_branch_iform(*src))
 155                 return create_branch(dest, target, *src);
 156         else if (instr_is_branch_bform(*src))
 157                 return create_cond_branch(dest, target, *src);
 158
 159         return 0;
 160 }
 161
 162
 163 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 164
 165 static void __init test_trampoline(void)
 166 {
 167         asm ("nop;\n");
 168 }
 169
 170 #define check(x)        \
 171         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 172
 173 static void __init test_branch_iform(void)
 174 {
 175         unsigned int instr;
 176         unsigned long addr;
 177
 178         addr = (unsigned long)&instr;
 179
 180         /* The simplest case, branch to self, no flags */
 181         check(instr_is_branch_iform(0x48000000));
 182         /* All bits of target set, and flags */
 183         check(instr_is_branch_iform(0x4bffffff));
 184         /* High bit of opcode set, which is wrong */
 185         check(!instr_is_branch_iform(0xcbffffff));
 186         /* Middle bits of opcode set, which is wrong */
 187         check(!instr_is_branch_iform(0x7bffffff));
 188
 189         /* Simplest case, branch to self with link */
 190         check(instr_is_branch_iform(0x48000001));
 191         /* All bits of targets set */
 192         check(instr_is_branch_iform(0x4bfffffd));
 193         /* Some bits of targets set */
 194         check(instr_is_branch_iform(0x4bff00fd));
 195         /* Must be a valid branch to start with */
 196         check(!instr_is_branch_iform(0x7bfffffd));
 197
 198         /* Absolute branch to 0x100 */
 199         instr = 0x48000103;
 200         check(instr_is_branch_to_addr(&instr, 0x100));
 201         /* Absolute branch to 0x420fc */
 202         instr = 0x480420ff;
 203         check(instr_is_branch_to_addr(&instr, 0x420fc));
 204         /* Maximum positive relative branch, + 20MB - 4B */
 205         instr = 0x49fffffc;
 206         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 207         /* Smallest negative relative branch, - 4B */
 208         instr = 0x4bfffffc;
 209         check(instr_is_branch_to_addr(&instr, addr - 4));
 210         /* Largest negative relative branch, - 32 MB */
 211         instr = 0x4a000000;
 212         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 213
 214         /* Branch to self, with link */
 215         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 216         check(instr_is_branch_to_addr(&instr, addr));
 217
 218         /* Branch to self - 0x100, with link */
 219         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 220         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 221
 222         /* Branch to self + 0x100, no link */
 223         instr = create_branch(&instr, addr + 0x100, 0);
 224         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 225
 226         /* Maximum relative negative offset, - 32 MB */
 227         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 228         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 229
 230         /* Out of range relative negative offset, - 32 MB + 4*/
 231         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 232         check(instr == 0);
 233
 234         /* Out of range relative positive offset, + 32 MB */
 235         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 236         check(instr == 0);
 237
 238         /* Unaligned target */
 239         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 240         check(instr == 0);
 241
 242         /* Check flags are masked correctly */
 243         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 244         check(instr_is_branch_to_addr(&instr, addr));
 245         check(instr == 0x48000000);
 246 }
 247
 248 static void __init test_create_function_call(void)
 249 {
 250         unsigned int *iptr;
 251         unsigned long dest;
 252
 253         /* Check we can create a function call */
 254         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 255         dest = ppc_function_entry(test_create_function_call);
 256         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 257         check(instr_is_branch_to_addr(iptr, dest));
 258 }
 259
 260 static void __init test_branch_bform(void)
 261 {
 262         unsigned long addr;
 263         unsigned int *iptr, instr, flags;
 264
 265         iptr = &instr;
 266         addr = (unsigned long)iptr;
 267
 268         /* The simplest case, branch to self, no flags */
 269         check(instr_is_branch_bform(0x40000000));
 270         /* All bits of target set, and flags */
 271         check(instr_is_branch_bform(0x43ffffff));
 272         /* High bit of opcode set, which is wrong */
 273         check(!instr_is_branch_bform(0xc3ffffff));
 274         /* Middle bits of opcode set, which is wrong */
 275         check(!instr_is_branch_bform(0x7bffffff));
 276
 277         /* Absolute conditional branch to 0x100 */
 278         instr = 0x43ff0103;
 279         check(instr_is_branch_to_addr(&instr, 0x100));
 280         /* Absolute conditional branch to 0x20fc */
 281         instr = 0x43ff20ff;
 282         check(instr_is_branch_to_addr(&instr, 0x20fc));
 283         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 284         instr = 0x43ff7ffc;
 285         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 286         /* Smallest negative relative conditional branch, - 4B */
 287         instr = 0x43fffffc;
 288         check(instr_is_branch_to_addr(&instr, addr - 4));
 289         /* Largest negative relative conditional branch, - 32 KB */
 290         instr = 0x43ff8000;
 291         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 292
 293         /* All condition code bits set & link */
 294         flags = 0x3ff000 | BRANCH_SET_LINK;
 295
 296         /* Branch to self */
 297         instr = create_cond_branch(iptr, addr, flags);
 298         check(instr_is_branch_to_addr(&instr, addr));
 299
 300         /* Branch to self - 0x100 */
 301         instr = create_cond_branch(iptr, addr - 0x100, flags);
 302         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 303
 304         /* Branch to self + 0x100 */
 305         instr = create_cond_branch(iptr, addr + 0x100, flags);
 306         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 307
 308         /* Maximum relative negative offset, - 32 KB */
 309         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 310         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 311
 312         /* Out of range relative negative offset, - 32 KB + 4*/
 313         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 314         check(instr == 0);
 315
 316         /* Out of range relative positive offset, + 32 KB */
 317         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 318         check(instr == 0);
 319
 320         /* Unaligned target */
 321         instr = create_cond_branch(iptr, addr + 3, flags);
 322         check(instr == 0);
 323
 324         /* Check flags are masked correctly */
 325         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 326         check(instr_is_branch_to_addr(&instr, addr));
 327         check(instr == 0x43FF0000);
 328 }
 329
 330 static void __init test_translate_branch(void)
 331 {
 332         unsigned long addr;
 333         unsigned int *p, *q;
 334         void *buf;
 335
 336         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 337         check(buf);
 338         if (!buf)
 339                 return;
 340
 341         /* Simple case, branch to self moved a little */
 342         p = buf;
 343         addr = (unsigned long)p;
 344         patch_branch(p, addr, 0);
 345         check(instr_is_branch_to_addr(p, addr));
 346         q = p + 1;
 347         patch_instruction(q, translate_branch(q, p));
 348         check(instr_is_branch_to_addr(q, addr));
 349
 350         /* Maximum negative case, move b . to addr + 32 MB */
 351         p = buf;
 352         addr = (unsigned long)p;
 353         patch_branch(p, addr, 0);
 354         q = buf + 0x2000000;
 355         patch_instruction(q, translate_branch(q, p));
 356         check(instr_is_branch_to_addr(p, addr));
 357         check(instr_is_branch_to_addr(q, addr));
 358         check(*q == 0x4a000000);
 359
 360         /* Maximum positive case, move x to x - 32 MB + 4 */
 361         p = buf + 0x2000000;
 362         addr = (unsigned long)p;
 363         patch_branch(p, addr, 0);
 364         q = buf + 4;
 365         patch_instruction(q, translate_branch(q, p));
 366         check(instr_is_branch_to_addr(p, addr));
 367         check(instr_is_branch_to_addr(q, addr));
 368         check(*q == 0x49fffffc);
 369
 370         /* Jump to x + 16 MB moved to x + 20 MB */
 371         p = buf;
 372         addr = 0x1000000 + (unsigned long)buf;
 373         patch_branch(p, addr, BRANCH_SET_LINK);
 374         q = buf + 0x1400000;
 375         patch_instruction(q, translate_branch(q, p));
 376         check(instr_is_branch_to_addr(p, addr));
 377         check(instr_is_branch_to_addr(q, addr));
 378
 379         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 380         p = buf + 0x1000000;
 381         addr = 0x2000000 + (unsigned long)buf;
 382         patch_branch(p, addr, 0);
 383         q = buf + 4;
 384         patch_instruction(q, translate_branch(q, p));
 385         check(instr_is_branch_to_addr(p, addr));
 386         check(instr_is_branch_to_addr(q, addr));
 387
 388
 389         /* Conditional branch tests */
 390
 391         /* Simple case, branch to self moved a little */
 392         p = buf;
 393         addr = (unsigned long)p;
 394         patch_instruction(p, create_cond_branch(p, addr, 0));
 395         check(instr_is_branch_to_addr(p, addr));
 396         q = p + 1;
 397         patch_instruction(q, translate_branch(q, p));
 398         check(instr_is_branch_to_addr(q, addr));
 399
 400         /* Maximum negative case, move b . to addr + 32 KB */
 401         p = buf;
 402         addr = (unsigned long)p;
 403         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 404         q = buf + 0x8000;
 405         patch_instruction(q, translate_branch(q, p));
 406         check(instr_is_branch_to_addr(p, addr));
 407         check(instr_is_branch_to_addr(q, addr));
 408         check(*q == 0x43ff8000);
 409
 410         /* Maximum positive case, move x to x - 32 KB + 4 */
 411         p = buf + 0x8000;
 412         addr = (unsigned long)p;
 413         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 414         q = buf + 4;
 415         patch_instruction(q, translate_branch(q, p));
 416         check(instr_is_branch_to_addr(p, addr));
 417         check(instr_is_branch_to_addr(q, addr));
 418         check(*q == 0x43ff7ffc);
 419
 420         /* Jump to x + 12 KB moved to x + 20 KB */
 421         p = buf;
 422         addr = 0x3000 + (unsigned long)buf;
 423         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 424         q = buf + 0x5000;
 425         patch_instruction(q, translate_branch(q, p));
 426         check(instr_is_branch_to_addr(p, addr));
 427         check(instr_is_branch_to_addr(q, addr));
 428
 429         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 430         p = buf + 0x2000;
 431         addr = 0x4000 + (unsigned long)buf;
 432         patch_instruction(p, create_cond_branch(p, addr, 0));
 433         q = buf + 4;
 434         patch_instruction(q, translate_branch(q, p));
 435         check(instr_is_branch_to_addr(p, addr));
 436         check(instr_is_branch_to_addr(q, addr));
 437
 438         /* Free the buffer we were using */
 439         vfree(buf);
 440 }
 441
 442 static int __init test_code_patching(void)
 443 {
 444         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 445
 446         test_branch_iform();
 447         test_branch_bform();
 448         test_create_function_call();
 449         test_translate_branch();
 450
 451         return 0;
 452 }
 453 late_initcall(test_code_patching);
 454
 455 #endif /* CONFIG_CODE_PATCHING_SELFTEST */