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/kprobes.h> 12 #include <linux/vmalloc.h> 13 #include <linux/init.h> 14 #include <linux/mm.h> 15 #include <linux/cpuhotplug.h> 16 #include <linux/slab.h> 17 #include <linux/uaccess.h> 18 #include <linux/kprobes.h> 19 20 #include <asm/pgtable.h> 21 #include <asm/tlbflush.h> 22 #include <asm/page.h> 23 #include <asm/code-patching.h> 24 #include <asm/setup.h> 25 26 static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, 27 unsigned int *patch_addr) 28 { 29 int err; 30 31 __put_user_size(instr, patch_addr, 4, err); 32 if (err) 33 return err; 34 35 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr), 36 "r" (exec_addr)); 37 38 return 0; 39 } 40 41 int raw_patch_instruction(unsigned int *addr, unsigned int instr) 42 { 43 return __patch_instruction(addr, instr, addr); 44 } 45 46 #ifdef CONFIG_STRICT_KERNEL_RWX 47 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); 48 49 static int text_area_cpu_up(unsigned int cpu) 50 { 51 struct vm_struct *area; 52 53 area = get_vm_area(PAGE_SIZE, VM_ALLOC); 54 if (!area) { 55 WARN_ONCE(1, "Failed to create text area for cpu %d\n", 56 cpu); 57 return -1; 58 } 59 this_cpu_write(text_poke_area, area); 60 61 return 0; 62 } 63 64 static int text_area_cpu_down(unsigned int cpu) 65 { 66 free_vm_area(this_cpu_read(text_poke_area)); 67 return 0; 68 } 69 70 /* 71 * Run as a late init call. This allows all the boot time patching to be done 72 * simply by patching the code, and then we're called here prior to 73 * mark_rodata_ro(), which happens after all init calls are run. Although 74 * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge 75 * it as being preferable to a kernel that will crash later when someone tries 76 * to use patch_instruction(). 77 */ 78 static int __init setup_text_poke_area(void) 79 { 80 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 81 "powerpc/text_poke:online", text_area_cpu_up, 82 text_area_cpu_down)); 83 84 return 0; 85 } 86 late_initcall(setup_text_poke_area); 87 88 /* 89 * This can be called for kernel text or a module. 90 */ 91 static int map_patch_area(void *addr, unsigned long text_poke_addr) 92 { 93 unsigned long pfn; 94 int err; 95 96 if (is_vmalloc_addr(addr)) 97 pfn = vmalloc_to_pfn(addr); 98 else 99 pfn = __pa_symbol(addr) >> PAGE_SHIFT; 100 101 err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), 102 pgprot_val(PAGE_KERNEL)); 103 104 pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err); 105 if (err) 106 return -1; 107 108 return 0; 109 } 110 111 static inline int unmap_patch_area(unsigned long addr) 112 { 113 pte_t *ptep; 114 pmd_t *pmdp; 115 pud_t *pudp; 116 pgd_t *pgdp; 117 118 pgdp = pgd_offset_k(addr); 119 if (unlikely(!pgdp)) 120 return -EINVAL; 121 122 pudp = pud_offset(pgdp, addr); 123 if (unlikely(!pudp)) 124 return -EINVAL; 125 126 pmdp = pmd_offset(pudp, addr); 127 if (unlikely(!pmdp)) 128 return -EINVAL; 129 130 ptep = pte_offset_kernel(pmdp, addr); 131 if (unlikely(!ptep)) 132 return -EINVAL; 133 134 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); 135 136 /* 137 * In hash, pte_clear flushes the tlb, in radix, we have to 138 */ 139 pte_clear(&init_mm, addr, ptep); 140 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 141 142 return 0; 143 } 144 145 int patch_instruction(unsigned int *addr, unsigned int instr) 146 { 147 int err; 148 unsigned int *patch_addr = NULL; 149 unsigned long flags; 150 unsigned long text_poke_addr; 151 unsigned long kaddr = (unsigned long)addr; 152 153 /* 154 * During early early boot patch_instruction is called 155 * when text_poke_area is not ready, but we still need 156 * to allow patching. We just do the plain old patching 157 */ 158 if (!this_cpu_read(text_poke_area)) 159 return raw_patch_instruction(addr, instr); 160 161 local_irq_save(flags); 162 163 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; 164 if (map_patch_area(addr, text_poke_addr)) { 165 err = -1; 166 goto out; 167 } 168 169 patch_addr = (unsigned int *)(text_poke_addr) + 170 ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); 171 172 __patch_instruction(addr, instr, patch_addr); 173 174 err = unmap_patch_area(text_poke_addr); 175 if (err) 176 pr_warn("failed to unmap %lx\n", text_poke_addr); 177 178 out: 179 local_irq_restore(flags); 180 181 return err; 182 } 183 #else /* !CONFIG_STRICT_KERNEL_RWX */ 184 185 int patch_instruction(unsigned int *addr, unsigned int instr) 186 { 187 return raw_patch_instruction(addr, instr); 188 } 189 190 #endif /* CONFIG_STRICT_KERNEL_RWX */ 191 NOKPROBE_SYMBOL(patch_instruction); 192 193 int patch_branch(unsigned int *addr, unsigned long target, int flags) 194 { 195 return patch_instruction(addr, create_branch(addr, target, flags)); 196 } 197 198 bool is_offset_in_branch_range(long offset) 199 { 200 /* 201 * Powerpc branch instruction is : 202 * 203 * 0 6 30 31 204 * +---------+----------------+---+---+ 205 * | opcode | LI |AA |LK | 206 * +---------+----------------+---+---+ 207 * Where AA = 0 and LK = 0 208 * 209 * LI is a signed 24 bits integer. The real branch offset is computed 210 * by: imm32 = SignExtend(LI:'0b00', 32); 211 * 212 * So the maximum forward branch should be: 213 * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc 214 * The maximum backward branch should be: 215 * (0xff800000 << 2) = 0xfe000000 = -0x2000000 216 */ 217 return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); 218 } 219 220 /* 221 * Helper to check if a given instruction is a conditional branch 222 * Derived from the conditional checks in analyse_instr() 223 */ 224 bool is_conditional_branch(unsigned int instr) 225 { 226 unsigned int opcode = instr >> 26; 227 228 if (opcode == 16) /* bc, bca, bcl, bcla */ 229 return true; 230 if (opcode == 19) { 231 switch ((instr >> 1) & 0x3ff) { 232 case 16: /* bclr, bclrl */ 233 case 528: /* bcctr, bcctrl */ 234 case 560: /* bctar, bctarl */ 235 return true; 236 } 237 } 238 return false; 239 } 240 NOKPROBE_SYMBOL(is_conditional_branch); 241 242 unsigned int create_branch(const unsigned int *addr, 243 unsigned long target, int flags) 244 { 245 unsigned int instruction; 246 long offset; 247 248 offset = target; 249 if (! (flags & BRANCH_ABSOLUTE)) 250 offset = offset - (unsigned long)addr; 251 252 /* Check we can represent the target in the instruction format */ 253 if (!is_offset_in_branch_range(offset)) 254 return 0; 255 256 /* Mask out the flags and target, so they don't step on each other. */ 257 instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC); 258 259 return instruction; 260 } 261 262 unsigned int create_cond_branch(const unsigned int *addr, 263 unsigned long target, int flags) 264 { 265 unsigned int instruction; 266 long offset; 267 268 offset = target; 269 if (! (flags & BRANCH_ABSOLUTE)) 270 offset = offset - (unsigned long)addr; 271 272 /* Check we can represent the target in the instruction format */ 273 if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3) 274 return 0; 275 276 /* Mask out the flags and target, so they don't step on each other. */ 277 instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC); 278 279 return instruction; 280 } 281 282 static unsigned int branch_opcode(unsigned int instr) 283 { 284 return (instr >> 26) & 0x3F; 285 } 286 287 static int instr_is_branch_iform(unsigned int instr) 288 { 289 return branch_opcode(instr) == 18; 290 } 291 292 static int instr_is_branch_bform(unsigned int instr) 293 { 294 return branch_opcode(instr) == 16; 295 } 296 297 int instr_is_relative_branch(unsigned int instr) 298 { 299 if (instr & BRANCH_ABSOLUTE) 300 return 0; 301 302 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); 303 } 304 305 int instr_is_relative_link_branch(unsigned int instr) 306 { 307 return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK); 308 } 309 310 static unsigned long branch_iform_target(const unsigned int *instr) 311 { 312 signed long imm; 313 314 imm = *instr & 0x3FFFFFC; 315 316 /* If the top bit of the immediate value is set this is negative */ 317 if (imm & 0x2000000) 318 imm -= 0x4000000; 319 320 if ((*instr & BRANCH_ABSOLUTE) == 0) 321 imm += (unsigned long)instr; 322 323 return (unsigned long)imm; 324 } 325 326 static unsigned long branch_bform_target(const unsigned int *instr) 327 { 328 signed long imm; 329 330 imm = *instr & 0xFFFC; 331 332 /* If the top bit of the immediate value is set this is negative */ 333 if (imm & 0x8000) 334 imm -= 0x10000; 335 336 if ((*instr & BRANCH_ABSOLUTE) == 0) 337 imm += (unsigned long)instr; 338 339 return (unsigned long)imm; 340 } 341 342 unsigned long branch_target(const unsigned int *instr) 343 { 344 if (instr_is_branch_iform(*instr)) 345 return branch_iform_target(instr); 346 else if (instr_is_branch_bform(*instr)) 347 return branch_bform_target(instr); 348 349 return 0; 350 } 351 352 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr) 353 { 354 if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr)) 355 return branch_target(instr) == addr; 356 357 return 0; 358 } 359 360 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src) 361 { 362 unsigned long target; 363 364 target = branch_target(src); 365 366 if (instr_is_branch_iform(*src)) 367 return create_branch(dest, target, *src); 368 else if (instr_is_branch_bform(*src)) 369 return create_cond_branch(dest, target, *src); 370 371 return 0; 372 } 373 374 #ifdef CONFIG_PPC_BOOK3E_64 375 void __patch_exception(int exc, unsigned long addr) 376 { 377 extern unsigned int interrupt_base_book3e; 378 unsigned int *ibase = &interrupt_base_book3e; 379 380 /* Our exceptions vectors start with a NOP and -then- a branch 381 * to deal with single stepping from userspace which stops on 382 * the second instruction. Thus we need to patch the second 383 * instruction of the exception, not the first one 384 */ 385 386 patch_branch(ibase + (exc / 4) + 1, addr, 0); 387 } 388 #endif 389 390 #ifdef CONFIG_CODE_PATCHING_SELFTEST 391 392 static void __init test_trampoline(void) 393 { 394 asm ("nop;\n"); 395 } 396 397 #define check(x) \ 398 if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__); 399 400 static void __init test_branch_iform(void) 401 { 402 unsigned int instr; 403 unsigned long addr; 404 405 addr = (unsigned long)&instr; 406 407 /* The simplest case, branch to self, no flags */ 408 check(instr_is_branch_iform(0x48000000)); 409 /* All bits of target set, and flags */ 410 check(instr_is_branch_iform(0x4bffffff)); 411 /* High bit of opcode set, which is wrong */ 412 check(!instr_is_branch_iform(0xcbffffff)); 413 /* Middle bits of opcode set, which is wrong */ 414 check(!instr_is_branch_iform(0x7bffffff)); 415 416 /* Simplest case, branch to self with link */ 417 check(instr_is_branch_iform(0x48000001)); 418 /* All bits of targets set */ 419 check(instr_is_branch_iform(0x4bfffffd)); 420 /* Some bits of targets set */ 421 check(instr_is_branch_iform(0x4bff00fd)); 422 /* Must be a valid branch to start with */ 423 check(!instr_is_branch_iform(0x7bfffffd)); 424 425 /* Absolute branch to 0x100 */ 426 instr = 0x48000103; 427 check(instr_is_branch_to_addr(&instr, 0x100)); 428 /* Absolute branch to 0x420fc */ 429 instr = 0x480420ff; 430 check(instr_is_branch_to_addr(&instr, 0x420fc)); 431 /* Maximum positive relative branch, + 20MB - 4B */ 432 instr = 0x49fffffc; 433 check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC)); 434 /* Smallest negative relative branch, - 4B */ 435 instr = 0x4bfffffc; 436 check(instr_is_branch_to_addr(&instr, addr - 4)); 437 /* Largest negative relative branch, - 32 MB */ 438 instr = 0x4a000000; 439 check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); 440 441 /* Branch to self, with link */ 442 instr = create_branch(&instr, addr, BRANCH_SET_LINK); 443 check(instr_is_branch_to_addr(&instr, addr)); 444 445 /* Branch to self - 0x100, with link */ 446 instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK); 447 check(instr_is_branch_to_addr(&instr, addr - 0x100)); 448 449 /* Branch to self + 0x100, no link */ 450 instr = create_branch(&instr, addr + 0x100, 0); 451 check(instr_is_branch_to_addr(&instr, addr + 0x100)); 452 453 /* Maximum relative negative offset, - 32 MB */ 454 instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK); 455 check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); 456 457 /* Out of range relative negative offset, - 32 MB + 4*/ 458 instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK); 459 check(instr == 0); 460 461 /* Out of range relative positive offset, + 32 MB */ 462 instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK); 463 check(instr == 0); 464 465 /* Unaligned target */ 466 instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK); 467 check(instr == 0); 468 469 /* Check flags are masked correctly */ 470 instr = create_branch(&instr, addr, 0xFFFFFFFC); 471 check(instr_is_branch_to_addr(&instr, addr)); 472 check(instr == 0x48000000); 473 } 474 475 static void __init test_create_function_call(void) 476 { 477 unsigned int *iptr; 478 unsigned long dest; 479 480 /* Check we can create a function call */ 481 iptr = (unsigned int *)ppc_function_entry(test_trampoline); 482 dest = ppc_function_entry(test_create_function_call); 483 patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK)); 484 check(instr_is_branch_to_addr(iptr, dest)); 485 } 486 487 static void __init test_branch_bform(void) 488 { 489 unsigned long addr; 490 unsigned int *iptr, instr, flags; 491 492 iptr = &instr; 493 addr = (unsigned long)iptr; 494 495 /* The simplest case, branch to self, no flags */ 496 check(instr_is_branch_bform(0x40000000)); 497 /* All bits of target set, and flags */ 498 check(instr_is_branch_bform(0x43ffffff)); 499 /* High bit of opcode set, which is wrong */ 500 check(!instr_is_branch_bform(0xc3ffffff)); 501 /* Middle bits of opcode set, which is wrong */ 502 check(!instr_is_branch_bform(0x7bffffff)); 503 504 /* Absolute conditional branch to 0x100 */ 505 instr = 0x43ff0103; 506 check(instr_is_branch_to_addr(&instr, 0x100)); 507 /* Absolute conditional branch to 0x20fc */ 508 instr = 0x43ff20ff; 509 check(instr_is_branch_to_addr(&instr, 0x20fc)); 510 /* Maximum positive relative conditional branch, + 32 KB - 4B */ 511 instr = 0x43ff7ffc; 512 check(instr_is_branch_to_addr(&instr, addr + 0x7FFC)); 513 /* Smallest negative relative conditional branch, - 4B */ 514 instr = 0x43fffffc; 515 check(instr_is_branch_to_addr(&instr, addr - 4)); 516 /* Largest negative relative conditional branch, - 32 KB */ 517 instr = 0x43ff8000; 518 check(instr_is_branch_to_addr(&instr, addr - 0x8000)); 519 520 /* All condition code bits set & link */ 521 flags = 0x3ff000 | BRANCH_SET_LINK; 522 523 /* Branch to self */ 524 instr = create_cond_branch(iptr, addr, flags); 525 check(instr_is_branch_to_addr(&instr, addr)); 526 527 /* Branch to self - 0x100 */ 528 instr = create_cond_branch(iptr, addr - 0x100, flags); 529 check(instr_is_branch_to_addr(&instr, addr - 0x100)); 530 531 /* Branch to self + 0x100 */ 532 instr = create_cond_branch(iptr, addr + 0x100, flags); 533 check(instr_is_branch_to_addr(&instr, addr + 0x100)); 534 535 /* Maximum relative negative offset, - 32 KB */ 536 instr = create_cond_branch(iptr, addr - 0x8000, flags); 537 check(instr_is_branch_to_addr(&instr, addr - 0x8000)); 538 539 /* Out of range relative negative offset, - 32 KB + 4*/ 540 instr = create_cond_branch(iptr, addr - 0x8004, flags); 541 check(instr == 0); 542 543 /* Out of range relative positive offset, + 32 KB */ 544 instr = create_cond_branch(iptr, addr + 0x8000, flags); 545 check(instr == 0); 546 547 /* Unaligned target */ 548 instr = create_cond_branch(iptr, addr + 3, flags); 549 check(instr == 0); 550 551 /* Check flags are masked correctly */ 552 instr = create_cond_branch(iptr, addr, 0xFFFFFFFC); 553 check(instr_is_branch_to_addr(&instr, addr)); 554 check(instr == 0x43FF0000); 555 } 556 557 static void __init test_translate_branch(void) 558 { 559 unsigned long addr; 560 unsigned int *p, *q; 561 void *buf; 562 563 buf = vmalloc(PAGE_ALIGN(0x2000000 + 1)); 564 check(buf); 565 if (!buf) 566 return; 567 568 /* Simple case, branch to self moved a little */ 569 p = buf; 570 addr = (unsigned long)p; 571 patch_branch(p, addr, 0); 572 check(instr_is_branch_to_addr(p, addr)); 573 q = p + 1; 574 patch_instruction(q, translate_branch(q, p)); 575 check(instr_is_branch_to_addr(q, addr)); 576 577 /* Maximum negative case, move b . to addr + 32 MB */ 578 p = buf; 579 addr = (unsigned long)p; 580 patch_branch(p, addr, 0); 581 q = buf + 0x2000000; 582 patch_instruction(q, translate_branch(q, p)); 583 check(instr_is_branch_to_addr(p, addr)); 584 check(instr_is_branch_to_addr(q, addr)); 585 check(*q == 0x4a000000); 586 587 /* Maximum positive case, move x to x - 32 MB + 4 */ 588 p = buf + 0x2000000; 589 addr = (unsigned long)p; 590 patch_branch(p, addr, 0); 591 q = buf + 4; 592 patch_instruction(q, translate_branch(q, p)); 593 check(instr_is_branch_to_addr(p, addr)); 594 check(instr_is_branch_to_addr(q, addr)); 595 check(*q == 0x49fffffc); 596 597 /* Jump to x + 16 MB moved to x + 20 MB */ 598 p = buf; 599 addr = 0x1000000 + (unsigned long)buf; 600 patch_branch(p, addr, BRANCH_SET_LINK); 601 q = buf + 0x1400000; 602 patch_instruction(q, translate_branch(q, p)); 603 check(instr_is_branch_to_addr(p, addr)); 604 check(instr_is_branch_to_addr(q, addr)); 605 606 /* Jump to x + 16 MB moved to x - 16 MB + 4 */ 607 p = buf + 0x1000000; 608 addr = 0x2000000 + (unsigned long)buf; 609 patch_branch(p, addr, 0); 610 q = buf + 4; 611 patch_instruction(q, translate_branch(q, p)); 612 check(instr_is_branch_to_addr(p, addr)); 613 check(instr_is_branch_to_addr(q, addr)); 614 615 616 /* Conditional branch tests */ 617 618 /* Simple case, branch to self moved a little */ 619 p = buf; 620 addr = (unsigned long)p; 621 patch_instruction(p, create_cond_branch(p, addr, 0)); 622 check(instr_is_branch_to_addr(p, addr)); 623 q = p + 1; 624 patch_instruction(q, translate_branch(q, p)); 625 check(instr_is_branch_to_addr(q, addr)); 626 627 /* Maximum negative case, move b . to addr + 32 KB */ 628 p = buf; 629 addr = (unsigned long)p; 630 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); 631 q = buf + 0x8000; 632 patch_instruction(q, translate_branch(q, p)); 633 check(instr_is_branch_to_addr(p, addr)); 634 check(instr_is_branch_to_addr(q, addr)); 635 check(*q == 0x43ff8000); 636 637 /* Maximum positive case, move x to x - 32 KB + 4 */ 638 p = buf + 0x8000; 639 addr = (unsigned long)p; 640 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); 641 q = buf + 4; 642 patch_instruction(q, translate_branch(q, p)); 643 check(instr_is_branch_to_addr(p, addr)); 644 check(instr_is_branch_to_addr(q, addr)); 645 check(*q == 0x43ff7ffc); 646 647 /* Jump to x + 12 KB moved to x + 20 KB */ 648 p = buf; 649 addr = 0x3000 + (unsigned long)buf; 650 patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK)); 651 q = buf + 0x5000; 652 patch_instruction(q, translate_branch(q, p)); 653 check(instr_is_branch_to_addr(p, addr)); 654 check(instr_is_branch_to_addr(q, addr)); 655 656 /* Jump to x + 8 KB moved to x - 8 KB + 4 */ 657 p = buf + 0x2000; 658 addr = 0x4000 + (unsigned long)buf; 659 patch_instruction(p, create_cond_branch(p, addr, 0)); 660 q = buf + 4; 661 patch_instruction(q, translate_branch(q, p)); 662 check(instr_is_branch_to_addr(p, addr)); 663 check(instr_is_branch_to_addr(q, addr)); 664 665 /* Free the buffer we were using */ 666 vfree(buf); 667 } 668 669 static int __init test_code_patching(void) 670 { 671 printk(KERN_DEBUG "Running code patching self-tests ...\n"); 672 673 test_branch_iform(); 674 test_branch_bform(); 675 test_create_function_call(); 676 test_translate_branch(); 677 678 return 0; 679 } 680 late_initcall(test_code_patching); 681 682 #endif /* CONFIG_CODE_PATCHING_SELFTEST */ 683