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 #include <asm/setup.h>
  18 #include <asm/sections.h>
  19
  20
  21 static inline bool is_init(unsigned int *addr)
  22 {
  23         return addr >= (unsigned int *)__init_begin && addr < (unsigned int *)__init_end;
  24 }
  25
  26 int patch_instruction(unsigned int *addr, unsigned int instr)
  27 {
  28         int err;
  29
  30         /* Make sure we aren't patching a freed init section */
  31         if (*PTRRELOC(&init_mem_is_free) && is_init(addr)) {
  32                 pr_debug("Skipping init section patching addr: 0x%px\n", addr);
  33                 return 0;
  34         }
  35
  36         __put_user_size(instr, addr, 4, err);
  37         if (err)
  38                 return err;
  39         asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
  40         return 0;
  41 }
  42
  43 int patch_branch(unsigned int *addr, unsigned long target, int flags)
  44 {
  45         return patch_instruction(addr, create_branch(addr, target, flags));
  46 }
  47
  48 int patch_branch_site(s32 *site, unsigned long target, int flags)
  49 {
  50         unsigned int *addr;
  51
  52         addr = (unsigned int *)((unsigned long)site + *site);
  53         return patch_instruction(addr, create_branch(addr, target, flags));
  54 }
  55
  56 int patch_instruction_site(s32 *site, unsigned int instr)
  57 {
  58         unsigned int *addr;
  59
  60         addr = (unsigned int *)((unsigned long)site + *site);
  61         return patch_instruction(addr, instr);
  62 }
  63
  64 unsigned int create_branch(const unsigned int *addr,
  65                            unsigned long target, int flags)
  66 {
  67         unsigned int instruction;
  68         long offset;
  69
  70         offset = target;
  71         if (! (flags & BRANCH_ABSOLUTE))
  72                 offset = offset - (unsigned long)addr;
  73
  74         /* Check we can represent the target in the instruction format */
  75         if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
  76                 return 0;
  77
  78         /* Mask out the flags and target, so they don't step on each other. */
  79         instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
  80
  81         return instruction;
  82 }
  83
  84 unsigned int create_cond_branch(const unsigned int *addr,
  85                                 unsigned long target, int flags)
  86 {
  87         unsigned int instruction;
  88         long offset;
  89
  90         offset = target;
  91         if (! (flags & BRANCH_ABSOLUTE))
  92                 offset = offset - (unsigned long)addr;
  93
  94         /* Check we can represent the target in the instruction format */
  95         if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
  96                 return 0;
  97
  98         /* Mask out the flags and target, so they don't step on each other. */
  99         instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
 100
 101         return instruction;
 102 }
 103
 104 static unsigned int branch_opcode(unsigned int instr)
 105 {
 106         return (instr >> 26) & 0x3F;
 107 }
 108
 109 static int instr_is_branch_iform(unsigned int instr)
 110 {
 111         return branch_opcode(instr) == 18;
 112 }
 113
 114 static int instr_is_branch_bform(unsigned int instr)
 115 {
 116         return branch_opcode(instr) == 16;
 117 }
 118
 119 int instr_is_relative_branch(unsigned int instr)
 120 {
 121         if (instr & BRANCH_ABSOLUTE)
 122                 return 0;
 123
 124         return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 125 }
 126
 127 static unsigned long branch_iform_target(const unsigned int *instr)
 128 {
 129         signed long imm;
 130
 131         imm = *instr & 0x3FFFFFC;
 132
 133         /* If the top bit of the immediate value is set this is negative */
 134         if (imm & 0x2000000)
 135                 imm -= 0x4000000;
 136
 137         if ((*instr & BRANCH_ABSOLUTE) == 0)
 138                 imm += (unsigned long)instr;
 139
 140         return (unsigned long)imm;
 141 }
 142
 143 static unsigned long branch_bform_target(const unsigned int *instr)
 144 {
 145         signed long imm;
 146
 147         imm = *instr & 0xFFFC;
 148
 149         /* If the top bit of the immediate value is set this is negative */
 150         if (imm & 0x8000)
 151                 imm -= 0x10000;
 152
 153         if ((*instr & BRANCH_ABSOLUTE) == 0)
 154                 imm += (unsigned long)instr;
 155
 156         return (unsigned long)imm;
 157 }
 158
 159 unsigned long branch_target(const unsigned int *instr)
 160 {
 161         if (instr_is_branch_iform(*instr))
 162                 return branch_iform_target(instr);
 163         else if (instr_is_branch_bform(*instr))
 164                 return branch_bform_target(instr);
 165
 166         return 0;
 167 }
 168
 169 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 170 {
 171         if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 172                 return branch_target(instr) == addr;
 173
 174         return 0;
 175 }
 176
 177 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 178 {
 179         unsigned long target;
 180
 181         target = branch_target(src);
 182
 183         if (instr_is_branch_iform(*src))
 184                 return create_branch(dest, target, *src);
 185         else if (instr_is_branch_bform(*src))
 186                 return create_cond_branch(dest, target, *src);
 187
 188         return 0;
 189 }
 190
 191 #ifdef CONFIG_PPC_BOOK3E_64
 192 void __patch_exception(int exc, unsigned long addr)
 193 {
 194         extern unsigned int interrupt_base_book3e;
 195         unsigned int *ibase = &interrupt_base_book3e;
 196
 197         /* Our exceptions vectors start with a NOP and -then- a branch
 198          * to deal with single stepping from userspace which stops on
 199          * the second instruction. Thus we need to patch the second
 200          * instruction of the exception, not the first one
 201          */
 202
 203         patch_branch(ibase + (exc / 4) + 1, addr, 0);
 204 }
 205 #endif
 206
 207 #ifdef CONFIG_CODE_PATCHING_SELFTEST
 208
 209 static void __init test_trampoline(void)
 210 {
 211         asm ("nop;\n");
 212 }
 213
 214 #define check(x)        \
 215         if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
 216
 217 static void __init test_branch_iform(void)
 218 {
 219         unsigned int instr;
 220         unsigned long addr;
 221
 222         addr = (unsigned long)&instr;
 223
 224         /* The simplest case, branch to self, no flags */
 225         check(instr_is_branch_iform(0x48000000));
 226         /* All bits of target set, and flags */
 227         check(instr_is_branch_iform(0x4bffffff));
 228         /* High bit of opcode set, which is wrong */
 229         check(!instr_is_branch_iform(0xcbffffff));
 230         /* Middle bits of opcode set, which is wrong */
 231         check(!instr_is_branch_iform(0x7bffffff));
 232
 233         /* Simplest case, branch to self with link */
 234         check(instr_is_branch_iform(0x48000001));
 235         /* All bits of targets set */
 236         check(instr_is_branch_iform(0x4bfffffd));
 237         /* Some bits of targets set */
 238         check(instr_is_branch_iform(0x4bff00fd));
 239         /* Must be a valid branch to start with */
 240         check(!instr_is_branch_iform(0x7bfffffd));
 241
 242         /* Absolute branch to 0x100 */
 243         instr = 0x48000103;
 244         check(instr_is_branch_to_addr(&instr, 0x100));
 245         /* Absolute branch to 0x420fc */
 246         instr = 0x480420ff;
 247         check(instr_is_branch_to_addr(&instr, 0x420fc));
 248         /* Maximum positive relative branch, + 20MB - 4B */
 249         instr = 0x49fffffc;
 250         check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 251         /* Smallest negative relative branch, - 4B */
 252         instr = 0x4bfffffc;
 253         check(instr_is_branch_to_addr(&instr, addr - 4));
 254         /* Largest negative relative branch, - 32 MB */
 255         instr = 0x4a000000;
 256         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 257
 258         /* Branch to self, with link */
 259         instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 260         check(instr_is_branch_to_addr(&instr, addr));
 261
 262         /* Branch to self - 0x100, with link */
 263         instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 264         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 265
 266         /* Branch to self + 0x100, no link */
 267         instr = create_branch(&instr, addr + 0x100, 0);
 268         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 269
 270         /* Maximum relative negative offset, - 32 MB */
 271         instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 272         check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
 273
 274         /* Out of range relative negative offset, - 32 MB + 4*/
 275         instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 276         check(instr == 0);
 277
 278         /* Out of range relative positive offset, + 32 MB */
 279         instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 280         check(instr == 0);
 281
 282         /* Unaligned target */
 283         instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 284         check(instr == 0);
 285
 286         /* Check flags are masked correctly */
 287         instr = create_branch(&instr, addr, 0xFFFFFFFC);
 288         check(instr_is_branch_to_addr(&instr, addr));
 289         check(instr == 0x48000000);
 290 }
 291
 292 static void __init test_create_function_call(void)
 293 {
 294         unsigned int *iptr;
 295         unsigned long dest;
 296
 297         /* Check we can create a function call */
 298         iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 299         dest = ppc_function_entry(test_create_function_call);
 300         patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 301         check(instr_is_branch_to_addr(iptr, dest));
 302 }
 303
 304 static void __init test_branch_bform(void)
 305 {
 306         unsigned long addr;
 307         unsigned int *iptr, instr, flags;
 308
 309         iptr = &instr;
 310         addr = (unsigned long)iptr;
 311
 312         /* The simplest case, branch to self, no flags */
 313         check(instr_is_branch_bform(0x40000000));
 314         /* All bits of target set, and flags */
 315         check(instr_is_branch_bform(0x43ffffff));
 316         /* High bit of opcode set, which is wrong */
 317         check(!instr_is_branch_bform(0xc3ffffff));
 318         /* Middle bits of opcode set, which is wrong */
 319         check(!instr_is_branch_bform(0x7bffffff));
 320
 321         /* Absolute conditional branch to 0x100 */
 322         instr = 0x43ff0103;
 323         check(instr_is_branch_to_addr(&instr, 0x100));
 324         /* Absolute conditional branch to 0x20fc */
 325         instr = 0x43ff20ff;
 326         check(instr_is_branch_to_addr(&instr, 0x20fc));
 327         /* Maximum positive relative conditional branch, + 32 KB - 4B */
 328         instr = 0x43ff7ffc;
 329         check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 330         /* Smallest negative relative conditional branch, - 4B */
 331         instr = 0x43fffffc;
 332         check(instr_is_branch_to_addr(&instr, addr - 4));
 333         /* Largest negative relative conditional branch, - 32 KB */
 334         instr = 0x43ff8000;
 335         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 336
 337         /* All condition code bits set & link */
 338         flags = 0x3ff000 | BRANCH_SET_LINK;
 339
 340         /* Branch to self */
 341         instr = create_cond_branch(iptr, addr, flags);
 342         check(instr_is_branch_to_addr(&instr, addr));
 343
 344         /* Branch to self - 0x100 */
 345         instr = create_cond_branch(iptr, addr - 0x100, flags);
 346         check(instr_is_branch_to_addr(&instr, addr - 0x100));
 347
 348         /* Branch to self + 0x100 */
 349         instr = create_cond_branch(iptr, addr + 0x100, flags);
 350         check(instr_is_branch_to_addr(&instr, addr + 0x100));
 351
 352         /* Maximum relative negative offset, - 32 KB */
 353         instr = create_cond_branch(iptr, addr - 0x8000, flags);
 354         check(instr_is_branch_to_addr(&instr, addr - 0x8000));
 355
 356         /* Out of range relative negative offset, - 32 KB + 4*/
 357         instr = create_cond_branch(iptr, addr - 0x8004, flags);
 358         check(instr == 0);
 359
 360         /* Out of range relative positive offset, + 32 KB */
 361         instr = create_cond_branch(iptr, addr + 0x8000, flags);
 362         check(instr == 0);
 363
 364         /* Unaligned target */
 365         instr = create_cond_branch(iptr, addr + 3, flags);
 366         check(instr == 0);
 367
 368         /* Check flags are masked correctly */
 369         instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 370         check(instr_is_branch_to_addr(&instr, addr));
 371         check(instr == 0x43FF0000);
 372 }
 373
 374 static void __init test_translate_branch(void)
 375 {
 376         unsigned long addr;
 377         unsigned int *p, *q;
 378         void *buf;
 379
 380         buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 381         check(buf);
 382         if (!buf)
 383                 return;
 384
 385         /* Simple case, branch to self moved a little */
 386         p = buf;
 387         addr = (unsigned long)p;
 388         patch_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 MB */
 395         p = buf;
 396         addr = (unsigned long)p;
 397         patch_branch(p, addr, 0);
 398         q = buf + 0x2000000;
 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 == 0x4a000000);
 403
 404         /* Maximum positive case, move x to x - 32 MB + 4 */
 405         p = buf + 0x2000000;
 406         addr = (unsigned long)p;
 407         patch_branch(p, addr, 0);
 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 == 0x49fffffc);
 413
 414         /* Jump to x + 16 MB moved to x + 20 MB */
 415         p = buf;
 416         addr = 0x1000000 + (unsigned long)buf;
 417         patch_branch(p, addr, BRANCH_SET_LINK);
 418         q = buf + 0x1400000;
 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 + 16 MB moved to x - 16 MB + 4 */
 424         p = buf + 0x1000000;
 425         addr = 0x2000000 + (unsigned long)buf;
 426         patch_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
 433         /* Conditional branch tests */
 434
 435         /* Simple case, branch to self moved a little */
 436         p = buf;
 437         addr = (unsigned long)p;
 438         patch_instruction(p, create_cond_branch(p, addr, 0));
 439         check(instr_is_branch_to_addr(p, addr));
 440         q = p + 1;
 441         patch_instruction(q, translate_branch(q, p));
 442         check(instr_is_branch_to_addr(q, addr));
 443
 444         /* Maximum negative case, move b . to addr + 32 KB */
 445         p = buf;
 446         addr = (unsigned long)p;
 447         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 448         q = buf + 0x8000;
 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         check(*q == 0x43ff8000);
 453
 454         /* Maximum positive case, move x to x - 32 KB + 4 */
 455         p = buf + 0x8000;
 456         addr = (unsigned long)p;
 457         patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 458         q = buf + 4;
 459         patch_instruction(q, translate_branch(q, p));
 460         check(instr_is_branch_to_addr(p, addr));
 461         check(instr_is_branch_to_addr(q, addr));
 462         check(*q == 0x43ff7ffc);
 463
 464         /* Jump to x + 12 KB moved to x + 20 KB */
 465         p = buf;
 466         addr = 0x3000 + (unsigned long)buf;
 467         patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 468         q = buf + 0x5000;
 469         patch_instruction(q, translate_branch(q, p));
 470         check(instr_is_branch_to_addr(p, addr));
 471         check(instr_is_branch_to_addr(q, addr));
 472
 473         /* Jump to x + 8 KB moved to x - 8 KB + 4 */
 474         p = buf + 0x2000;
 475         addr = 0x4000 + (unsigned long)buf;
 476         patch_instruction(p, create_cond_branch(p, addr, 0));
 477         q = buf + 4;
 478         patch_instruction(q, translate_branch(q, p));
 479         check(instr_is_branch_to_addr(p, addr));
 480         check(instr_is_branch_to_addr(q, addr));
 481
 482         /* Free the buffer we were using */
 483         vfree(buf);
 484 }
 485
 486 static int __init test_code_patching(void)
 487 {
 488         printk(KERN_DEBUG "Running code patching self-tests ...\n");
 489
 490         test_branch_iform();
 491         test_branch_bform();
 492         test_create_function_call();
 493         test_translate_branch();
 494
 495         return 0;
 496 }
 497 late_initcall(test_code_patching);
 498
 499 #endif /* CONFIG_CODE_PATCHING_SELFTEST */