kernel/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 #ifdef CONFIG_PPC_BOOK3E_64
 163 void __patch_exception(int exc, unsigned long addr)
 164 {
 165         extern unsigned int interrupt_base_book3e;
 166         unsigned int *ibase = &interrupt_base_book3e;
 167
 168         /* Our exceptions vectors start with a NOP and -then- a branch
 169          * to deal with single stepping from userspace which stops on
 170          * the second instruction. Thus we need to patch the second
 171          * instruction of the exception, not the first one
 172          */
 173
 174         patch_branch(ibase + (exc / 4) + 1, addr, 0);
 175 }
 176 #endif
 177
 178 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 179
 180 static void __init test_trampoline(void)
 181 {
 182         asm ("nop;\n");
 183 }
 184
 185 #define check(x)        \
 186         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 187
 188 static void __init test_branch_iform(void)
 189 {
 190         unsigned int instr;
 191         unsigned long addr;
 192
 193         addr = (unsigned long)&instr;
 194
 195         /* The simplest case, branch to self, no flags */
 196         check(instr_is_branch_iform(0x48000000));
 197         /* All bits of target set, and flags */
 198         check(instr_is_branch_iform(0x4bffffff));
 199         /* High bit of opcode set, which is wrong */
 200         check(!instr_is_branch_iform(0xcbffffff));
 201         /* Middle bits of opcode set, which is wrong */
 202         check(!instr_is_branch_iform(0x7bffffff));
 203
 204         /* Simplest case, branch to self with link */
 205         check(instr_is_branch_iform(0x48000001));
 206         /* All bits of targets set */
 207         check(instr_is_branch_iform(0x4bfffffd));
 208         /* Some bits of targets set */
 209         check(instr_is_branch_iform(0x4bff00fd));
 210         /* Must be a valid branch to start with */
 211         check(!instr_is_branch_iform(0x7bfffffd));
 212
 213         /* Absolute branch to 0x100 */
 214         instr = 0x48000103;
 215         check(instr_is_branch_to_addr(&instr, 0x100));
 216         /* Absolute branch to 0x420fc */
 217         instr = 0x480420ff;
 218         check(instr_is_branch_to_addr(&instr, 0x420fc));
 219         /* Maximum positive relative branch, + 20MB - 4B */
 220         instr = 0x49fffffc;
 221         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 222         /* Smallest negative relative branch, - 4B */
 223         instr = 0x4bfffffc;
 224         check(instr_is_branch_to_addr(&instr, addr - 4));
 225         /* Largest negative relative branch, - 32 MB */
 226         instr = 0x4a000000;
 227         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 228
 229         /* Branch to self, with link */
 230         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 231         check(instr_is_branch_to_addr(&instr, addr));
 232
 233         /* Branch to self - 0x100, with link */
 234         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 235         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 236
 237         /* Branch to self + 0x100, no link */
 238         instr = create_branch(&instr, addr + 0x100, 0);
 239         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 240
 241         /* Maximum relative negative offset, - 32 MB */
 242         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 243         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 244
 245         /* Out of range relative negative offset, - 32 MB + 4*/
 246         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 247         check(instr == 0);
 248
 249         /* Out of range relative positive offset, + 32 MB */
 250         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 251         check(instr == 0);
 252
 253         /* Unaligned target */
 254         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 255         check(instr == 0);
 256
 257         /* Check flags are masked correctly */
 258         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 259         check(instr_is_branch_to_addr(&instr, addr));
 260         check(instr == 0x48000000);
 261 }
 262
 263 static void __init test_create_function_call(void)
 264 {
 265         unsigned int *iptr;
 266         unsigned long dest;
 267
 268         /* Check we can create a function call */
 269         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 270         dest = ppc_function_entry(test_create_function_call);
 271         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 272         check(instr_is_branch_to_addr(iptr, dest));
 273 }
 274
 275 static void __init test_branch_bform(void)
 276 {
 277         unsigned long addr;
 278         unsigned int *iptr, instr, flags;
 279
 280         iptr = &instr;
 281         addr = (unsigned long)iptr;
 282
 283         /* The simplest case, branch to self, no flags */
 284         check(instr_is_branch_bform(0x40000000));
 285         /* All bits of target set, and flags */
 286         check(instr_is_branch_bform(0x43ffffff));
 287         /* High bit of opcode set, which is wrong */
 288         check(!instr_is_branch_bform(0xc3ffffff));
 289         /* Middle bits of opcode set, which is wrong */
 290         check(!instr_is_branch_bform(0x7bffffff));
 291
 292         /* Absolute conditional branch to 0x100 */
 293         instr = 0x43ff0103;
 294         check(instr_is_branch_to_addr(&instr, 0x100));
 295         /* Absolute conditional branch to 0x20fc */
 296         instr = 0x43ff20ff;
 297         check(instr_is_branch_to_addr(&instr, 0x20fc));
 298         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 299         instr = 0x43ff7ffc;
 300         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 301         /* Smallest negative relative conditional branch, - 4B */
 302         instr = 0x43fffffc;
 303         check(instr_is_branch_to_addr(&instr, addr - 4));
 304         /* Largest negative relative conditional branch, - 32 KB */
 305         instr = 0x43ff8000;
 306         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 307
 308         /* All condition code bits set & link */
 309         flags = 0x3ff000 | BRANCH_SET_LINK;
 310
 311         /* Branch to self */
 312         instr = create_cond_branch(iptr, addr, flags);
 313         check(instr_is_branch_to_addr(&instr, addr));
 314
 315         /* Branch to self - 0x100 */
 316         instr = create_cond_branch(iptr, addr - 0x100, flags);
 317         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 318
 319         /* Branch to self + 0x100 */
 320         instr = create_cond_branch(iptr, addr + 0x100, flags);
 321         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 322
 323         /* Maximum relative negative offset, - 32 KB */
 324         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 325         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 326
 327         /* Out of range relative negative offset, - 32 KB + 4*/
 328         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 329         check(instr == 0);
 330
 331         /* Out of range relative positive offset, + 32 KB */
 332         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 333         check(instr == 0);
 334
 335         /* Unaligned target */
 336         instr = create_cond_branch(iptr, addr + 3, flags);
 337         check(instr == 0);
 338
 339         /* Check flags are masked correctly */
 340         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 341         check(instr_is_branch_to_addr(&instr, addr));
 342         check(instr == 0x43FF0000);
 343 }
 344
 345 static void __init test_translate_branch(void)
 346 {
 347         unsigned long addr;
 348         unsigned int *p, *q;
 349         void *buf;
 350
 351         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 352         check(buf);
 353         if (!buf)
 354                 return;
 355
 356         /* Simple case, branch to self moved a little */
 357         p = buf;
 358         addr = (unsigned long)p;
 359         patch_branch(p, addr, 0);
 360         check(instr_is_branch_to_addr(p, addr));
 361         q = p + 1;
 362         patch_instruction(q, translate_branch(q, p));
 363         check(instr_is_branch_to_addr(q, addr));
 364
 365         /* Maximum negative case, move b . to addr + 32 MB */
 366         p = buf;
 367         addr = (unsigned long)p;
 368         patch_branch(p, addr, 0);
 369         q = buf + 0x2000000;
 370         patch_instruction(q, translate_branch(q, p));
 371         check(instr_is_branch_to_addr(p, addr));
 372         check(instr_is_branch_to_addr(q, addr));
 373         check(*q == 0x4a000000);
 374
 375         /* Maximum positive case, move x to x - 32 MB + 4 */
 376         p = buf + 0x2000000;
 377         addr = (unsigned long)p;
 378         patch_branch(p, addr, 0);
 379         q = buf + 4;
 380         patch_instruction(q, translate_branch(q, p));
 381         check(instr_is_branch_to_addr(p, addr));
 382         check(instr_is_branch_to_addr(q, addr));
 383         check(*q == 0x49fffffc);
 384
 385         /* Jump to x + 16 MB moved to x + 20 MB */
 386         p = buf;
 387         addr = 0x1000000 + (unsigned long)buf;
 388         patch_branch(p, addr, BRANCH_SET_LINK);
 389         q = buf + 0x1400000;
 390         patch_instruction(q, translate_branch(q, p));
 391         check(instr_is_branch_to_addr(p, addr));
 392         check(instr_is_branch_to_addr(q, addr));
 393
 394         /* Jump to x + 16 MB moved to x - 16 MB + 4 */
 395         p = buf + 0x1000000;
 396         addr = 0x2000000 + (unsigned long)buf;
 397         patch_branch(p, addr, 0);
 398         q = buf + 4;
 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
 403
 404         /* Conditional branch tests */
 405
 406         /* Simple case, branch to self moved a little */
 407         p = buf;
 408         addr = (unsigned long)p;
 409         patch_instruction(p, create_cond_branch(p, addr, 0));
 410         check(instr_is_branch_to_addr(p, addr));
 411         q = p + 1;
 412         patch_instruction(q, translate_branch(q, p));
 413         check(instr_is_branch_to_addr(q, addr));
 414
 415         /* Maximum negative case, move b . to addr + 32 KB */
 416         p = buf;
 417         addr = (unsigned long)p;
 418         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 419         q = buf + 0x8000;
 420         patch_instruction(q, translate_branch(q, p));
 421         check(instr_is_branch_to_addr(p, addr));
 422         check(instr_is_branch_to_addr(q, addr));
 423         check(*q == 0x43ff8000);
 424
 425         /* Maximum positive case, move x to x - 32 KB + 4 */
 426         p = buf + 0x8000;
 427         addr = (unsigned long)p;
 428         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 429         q = buf + 4;
 430         patch_instruction(q, translate_branch(q, p));
 431         check(instr_is_branch_to_addr(p, addr));
 432         check(instr_is_branch_to_addr(q, addr));
 433         check(*q == 0x43ff7ffc);
 434
 435         /* Jump to x + 12 KB moved to x + 20 KB */
 436         p = buf;
 437         addr = 0x3000 + (unsigned long)buf;
 438         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 439         q = buf + 0x5000;
 440         patch_instruction(q, translate_branch(q, p));
 441         check(instr_is_branch_to_addr(p, addr));
 442         check(instr_is_branch_to_addr(q, addr));
 443
 444         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 445         p = buf + 0x2000;
 446         addr = 0x4000 + (unsigned long)buf;
 447         patch_instruction(p, create_cond_branch(p, addr, 0));
 448         q = buf + 4;
 449         patch_instruction(q, translate_branch(q, p));
 450         check(instr_is_branch_to_addr(p, addr));
 451         check(instr_is_branch_to_addr(q, addr));
 452
 453         /* Free the buffer we were using */
 454         vfree(buf);
 455 }
 456
 457 static int __init test_code_patching(void)
 458 {
 459         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 460
 461         test_branch_iform();
 462         test_branch_bform();
 463         test_create_function_call();
 464         test_translate_branch();
 465
 466         return 0;
 467 }
 468 late_initcall(test_code_patching);
 469
 470 #endif /* CONFIG_CODE_PATCHING_SELFTEST */