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 *addr, unsigned int instr) 27 { 28 int err; 29 30 __put_user_size(instr, addr, 4, err); 31 if (err) 32 return err; 33 34 asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" :: "r" (addr)); 35 36 return 0; 37 } 38 39 #ifdef CONFIG_STRICT_KERNEL_RWX 40 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); 41 42 static int text_area_cpu_up(unsigned int cpu) 43 { 44 struct vm_struct *area; 45 46 area = get_vm_area(PAGE_SIZE, VM_ALLOC); 47 if (!area) { 48 WARN_ONCE(1, "Failed to create text area for cpu %d\n", 49 cpu); 50 return -1; 51 } 52 this_cpu_write(text_poke_area, area); 53 54 return 0; 55 } 56 57 static int text_area_cpu_down(unsigned int cpu) 58 { 59 free_vm_area(this_cpu_read(text_poke_area)); 60 return 0; 61 } 62 63 /* 64 * Run as a late init call. This allows all the boot time patching to be done 65 * simply by patching the code, and then we're called here prior to 66 * mark_rodata_ro(), which happens after all init calls are run. Although 67 * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge 68 * it as being preferable to a kernel that will crash later when someone tries 69 * to use patch_instruction(). 70 */ 71 static int __init setup_text_poke_area(void) 72 { 73 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 74 "powerpc/text_poke:online", text_area_cpu_up, 75 text_area_cpu_down)); 76 77 return 0; 78 } 79 late_initcall(setup_text_poke_area); 80 81 /* 82 * This can be called for kernel text or a module. 83 */ 84 static int map_patch_area(void *addr, unsigned long text_poke_addr) 85 { 86 unsigned long pfn; 87 int err; 88 89 if (is_vmalloc_addr(addr)) 90 pfn = vmalloc_to_pfn(addr); 91 else 92 pfn = __pa_symbol(addr) >> PAGE_SHIFT; 93 94 err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), 95 pgprot_val(PAGE_KERNEL)); 96 97 pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err); 98 if (err) 99 return -1; 100 101 return 0; 102 } 103 104 static inline int unmap_patch_area(unsigned long addr) 105 { 106 pte_t *ptep; 107 pmd_t *pmdp; 108 pud_t *pudp; 109 pgd_t *pgdp; 110 111 pgdp = pgd_offset_k(addr); 112 if (unlikely(!pgdp)) 113 return -EINVAL; 114 115 pudp = pud_offset(pgdp, addr); 116 if (unlikely(!pudp)) 117 return -EINVAL; 118 119 pmdp = pmd_offset(pudp, addr); 120 if (unlikely(!pmdp)) 121 return -EINVAL; 122 123 ptep = pte_offset_kernel(pmdp, addr); 124 if (unlikely(!ptep)) 125 return -EINVAL; 126 127 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); 128 129 /* 130 * In hash, pte_clear flushes the tlb, in radix, we have to 131 */ 132 pte_clear(&init_mm, addr, ptep); 133 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 134 135 return 0; 136 } 137 138 int patch_instruction(unsigned int *addr, unsigned int instr) 139 { 140 int err; 141 unsigned int *dest = NULL; 142 unsigned long flags; 143 unsigned long text_poke_addr; 144 unsigned long kaddr = (unsigned long)addr; 145 146 /* 147 * During early early boot patch_instruction is called 148 * when text_poke_area is not ready, but we still need 149 * to allow patching. We just do the plain old patching 150 */ 151 if (!this_cpu_read(*PTRRELOC(&text_poke_area))) 152 return __patch_instruction(addr, instr); 153 154 local_irq_save(flags); 155 156 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; 157 if (map_patch_area(addr, text_poke_addr)) { 158 err = -1; 159 goto out; 160 } 161 162 dest = (unsigned int *)(text_poke_addr) + 163 ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); 164 165 /* 166 * We use __put_user_size so that we can handle faults while 167 * writing to dest and return err to handle faults gracefully 168 */ 169 __put_user_size(instr, dest, 4, err); 170 if (!err) 171 asm ("dcbst 0, %0; sync; icbi 0,%0; icbi 0,%1; sync; isync" 172 ::"r" (dest), "r"(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 __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 static unsigned long branch_iform_target(const unsigned int *instr) 306 { 307 signed long imm; 308 309 imm = *instr & 0x3FFFFFC; 310 311 /* If the top bit of the immediate value is set this is negative */ 312 if (imm & 0x2000000) 313 imm -= 0x4000000; 314 315 if ((*instr & BRANCH_ABSOLUTE) == 0) 316 imm += (unsigned long)instr; 317 318 return (unsigned long)imm; 319 } 320 321 static unsigned long branch_bform_target(const unsigned int *instr) 322 { 323 signed long imm; 324 325 imm = *instr & 0xFFFC; 326 327 /* If the top bit of the immediate value is set this is negative */ 328 if (imm & 0x8000) 329 imm -= 0x10000; 330 331 if ((*instr & BRANCH_ABSOLUTE) == 0) 332 imm += (unsigned long)instr; 333 334 return (unsigned long)imm; 335 } 336 337 unsigned long branch_target(const unsigned int *instr) 338 { 339 if (instr_is_branch_iform(*instr)) 340 return branch_iform_target(instr); 341 else if (instr_is_branch_bform(*instr)) 342 return branch_bform_target(instr); 343 344 return 0; 345 } 346 347 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr) 348 { 349 if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr)) 350 return branch_target(instr) == addr; 351 352 return 0; 353 } 354 355 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src) 356 { 357 unsigned long target; 358 359 target = branch_target(src); 360 361 if (instr_is_branch_iform(*src)) 362 return create_branch(dest, target, *src); 363 else if (instr_is_branch_bform(*src)) 364 return create_cond_branch(dest, target, *src); 365 366 return 0; 367 } 368 369 #ifdef CONFIG_PPC_BOOK3E_64 370 void __patch_exception(int exc, unsigned long addr) 371 { 372 extern unsigned int interrupt_base_book3e; 373 unsigned int *ibase = &interrupt_base_book3e; 374 375 /* Our exceptions vectors start with a NOP and -then- a branch 376 * to deal with single stepping from userspace which stops on 377 * the second instruction. Thus we need to patch the second 378 * instruction of the exception, not the first one 379 */ 380 381 patch_branch(ibase + (exc / 4) + 1, addr, 0); 382 } 383 #endif 384 385 #ifdef CONFIG_CODE_PATCHING_SELFTEST 386 387 static void __init test_trampoline(void) 388 { 389 asm ("nop;\n"); 390 } 391 392 #define check(x) \ 393 if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__); 394 395 static void __init test_branch_iform(void) 396 { 397 unsigned int instr; 398 unsigned long addr; 399 400 addr = (unsigned long)&instr; 401 402 /* The simplest case, branch to self, no flags */ 403 check(instr_is_branch_iform(0x48000000)); 404 /* All bits of target set, and flags */ 405 check(instr_is_branch_iform(0x4bffffff)); 406 /* High bit of opcode set, which is wrong */ 407 check(!instr_is_branch_iform(0xcbffffff)); 408 /* Middle bits of opcode set, which is wrong */ 409 check(!instr_is_branch_iform(0x7bffffff)); 410 411 /* Simplest case, branch to self with link */ 412 check(instr_is_branch_iform(0x48000001)); 413 /* All bits of targets set */ 414 check(instr_is_branch_iform(0x4bfffffd)); 415 /* Some bits of targets set */ 416 check(instr_is_branch_iform(0x4bff00fd)); 417 /* Must be a valid branch to start with */ 418 check(!instr_is_branch_iform(0x7bfffffd)); 419 420 /* Absolute branch to 0x100 */ 421 instr = 0x48000103; 422 check(instr_is_branch_to_addr(&instr, 0x100)); 423 /* Absolute branch to 0x420fc */ 424 instr = 0x480420ff; 425 check(instr_is_branch_to_addr(&instr, 0x420fc)); 426 /* Maximum positive relative branch, + 20MB - 4B */ 427 instr = 0x49fffffc; 428 check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC)); 429 /* Smallest negative relative branch, - 4B */ 430 instr = 0x4bfffffc; 431 check(instr_is_branch_to_addr(&instr, addr - 4)); 432 /* Largest negative relative branch, - 32 MB */ 433 instr = 0x4a000000; 434 check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); 435 436 /* Branch to self, with link */ 437 instr = create_branch(&instr, addr, BRANCH_SET_LINK); 438 check(instr_is_branch_to_addr(&instr, addr)); 439 440 /* Branch to self - 0x100, with link */ 441 instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK); 442 check(instr_is_branch_to_addr(&instr, addr - 0x100)); 443 444 /* Branch to self + 0x100, no link */ 445 instr = create_branch(&instr, addr + 0x100, 0); 446 check(instr_is_branch_to_addr(&instr, addr + 0x100)); 447 448 /* Maximum relative negative offset, - 32 MB */ 449 instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK); 450 check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); 451 452 /* Out of range relative negative offset, - 32 MB + 4*/ 453 instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK); 454 check(instr == 0); 455 456 /* Out of range relative positive offset, + 32 MB */ 457 instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK); 458 check(instr == 0); 459 460 /* Unaligned target */ 461 instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK); 462 check(instr == 0); 463 464 /* Check flags are masked correctly */ 465 instr = create_branch(&instr, addr, 0xFFFFFFFC); 466 check(instr_is_branch_to_addr(&instr, addr)); 467 check(instr == 0x48000000); 468 } 469 470 static void __init test_create_function_call(void) 471 { 472 unsigned int *iptr; 473 unsigned long dest; 474 475 /* Check we can create a function call */ 476 iptr = (unsigned int *)ppc_function_entry(test_trampoline); 477 dest = ppc_function_entry(test_create_function_call); 478 patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK)); 479 check(instr_is_branch_to_addr(iptr, dest)); 480 } 481 482 static void __init test_branch_bform(void) 483 { 484 unsigned long addr; 485 unsigned int *iptr, instr, flags; 486 487 iptr = &instr; 488 addr = (unsigned long)iptr; 489 490 /* The simplest case, branch to self, no flags */ 491 check(instr_is_branch_bform(0x40000000)); 492 /* All bits of target set, and flags */ 493 check(instr_is_branch_bform(0x43ffffff)); 494 /* High bit of opcode set, which is wrong */ 495 check(!instr_is_branch_bform(0xc3ffffff)); 496 /* Middle bits of opcode set, which is wrong */ 497 check(!instr_is_branch_bform(0x7bffffff)); 498 499 /* Absolute conditional branch to 0x100 */ 500 instr = 0x43ff0103; 501 check(instr_is_branch_to_addr(&instr, 0x100)); 502 /* Absolute conditional branch to 0x20fc */ 503 instr = 0x43ff20ff; 504 check(instr_is_branch_to_addr(&instr, 0x20fc)); 505 /* Maximum positive relative conditional branch, + 32 KB - 4B */ 506 instr = 0x43ff7ffc; 507 check(instr_is_branch_to_addr(&instr, addr + 0x7FFC)); 508 /* Smallest negative relative conditional branch, - 4B */ 509 instr = 0x43fffffc; 510 check(instr_is_branch_to_addr(&instr, addr - 4)); 511 /* Largest negative relative conditional branch, - 32 KB */ 512 instr = 0x43ff8000; 513 check(instr_is_branch_to_addr(&instr, addr - 0x8000)); 514 515 /* All condition code bits set & link */ 516 flags = 0x3ff000 | BRANCH_SET_LINK; 517 518 /* Branch to self */ 519 instr = create_cond_branch(iptr, addr, flags); 520 check(instr_is_branch_to_addr(&instr, addr)); 521 522 /* Branch to self - 0x100 */ 523 instr = create_cond_branch(iptr, addr - 0x100, flags); 524 check(instr_is_branch_to_addr(&instr, addr - 0x100)); 525 526 /* Branch to self + 0x100 */ 527 instr = create_cond_branch(iptr, addr + 0x100, flags); 528 check(instr_is_branch_to_addr(&instr, addr + 0x100)); 529 530 /* Maximum relative negative offset, - 32 KB */ 531 instr = create_cond_branch(iptr, addr - 0x8000, flags); 532 check(instr_is_branch_to_addr(&instr, addr - 0x8000)); 533 534 /* Out of range relative negative offset, - 32 KB + 4*/ 535 instr = create_cond_branch(iptr, addr - 0x8004, flags); 536 check(instr == 0); 537 538 /* Out of range relative positive offset, + 32 KB */ 539 instr = create_cond_branch(iptr, addr + 0x8000, flags); 540 check(instr == 0); 541 542 /* Unaligned target */ 543 instr = create_cond_branch(iptr, addr + 3, flags); 544 check(instr == 0); 545 546 /* Check flags are masked correctly */ 547 instr = create_cond_branch(iptr, addr, 0xFFFFFFFC); 548 check(instr_is_branch_to_addr(&instr, addr)); 549 check(instr == 0x43FF0000); 550 } 551 552 static void __init test_translate_branch(void) 553 { 554 unsigned long addr; 555 unsigned int *p, *q; 556 void *buf; 557 558 buf = vmalloc(PAGE_ALIGN(0x2000000 + 1)); 559 check(buf); 560 if (!buf) 561 return; 562 563 /* Simple case, branch to self moved a little */ 564 p = buf; 565 addr = (unsigned long)p; 566 patch_branch(p, addr, 0); 567 check(instr_is_branch_to_addr(p, addr)); 568 q = p + 1; 569 patch_instruction(q, translate_branch(q, p)); 570 check(instr_is_branch_to_addr(q, addr)); 571 572 /* Maximum negative case, move b . to addr + 32 MB */ 573 p = buf; 574 addr = (unsigned long)p; 575 patch_branch(p, addr, 0); 576 q = buf + 0x2000000; 577 patch_instruction(q, translate_branch(q, p)); 578 check(instr_is_branch_to_addr(p, addr)); 579 check(instr_is_branch_to_addr(q, addr)); 580 check(*q == 0x4a000000); 581 582 /* Maximum positive case, move x to x - 32 MB + 4 */ 583 p = buf + 0x2000000; 584 addr = (unsigned long)p; 585 patch_branch(p, addr, 0); 586 q = buf + 4; 587 patch_instruction(q, translate_branch(q, p)); 588 check(instr_is_branch_to_addr(p, addr)); 589 check(instr_is_branch_to_addr(q, addr)); 590 check(*q == 0x49fffffc); 591 592 /* Jump to x + 16 MB moved to x + 20 MB */ 593 p = buf; 594 addr = 0x1000000 + (unsigned long)buf; 595 patch_branch(p, addr, BRANCH_SET_LINK); 596 q = buf + 0x1400000; 597 patch_instruction(q, translate_branch(q, p)); 598 check(instr_is_branch_to_addr(p, addr)); 599 check(instr_is_branch_to_addr(q, addr)); 600 601 /* Jump to x + 16 MB moved to x - 16 MB + 4 */ 602 p = buf + 0x1000000; 603 addr = 0x2000000 + (unsigned long)buf; 604 patch_branch(p, addr, 0); 605 q = buf + 4; 606 patch_instruction(q, translate_branch(q, p)); 607 check(instr_is_branch_to_addr(p, addr)); 608 check(instr_is_branch_to_addr(q, addr)); 609 610 611 /* Conditional branch tests */ 612 613 /* Simple case, branch to self moved a little */ 614 p = buf; 615 addr = (unsigned long)p; 616 patch_instruction(p, create_cond_branch(p, addr, 0)); 617 check(instr_is_branch_to_addr(p, addr)); 618 q = p + 1; 619 patch_instruction(q, translate_branch(q, p)); 620 check(instr_is_branch_to_addr(q, addr)); 621 622 /* Maximum negative case, move b . to addr + 32 KB */ 623 p = buf; 624 addr = (unsigned long)p; 625 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); 626 q = buf + 0x8000; 627 patch_instruction(q, translate_branch(q, p)); 628 check(instr_is_branch_to_addr(p, addr)); 629 check(instr_is_branch_to_addr(q, addr)); 630 check(*q == 0x43ff8000); 631 632 /* Maximum positive case, move x to x - 32 KB + 4 */ 633 p = buf + 0x8000; 634 addr = (unsigned long)p; 635 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); 636 q = buf + 4; 637 patch_instruction(q, translate_branch(q, p)); 638 check(instr_is_branch_to_addr(p, addr)); 639 check(instr_is_branch_to_addr(q, addr)); 640 check(*q == 0x43ff7ffc); 641 642 /* Jump to x + 12 KB moved to x + 20 KB */ 643 p = buf; 644 addr = 0x3000 + (unsigned long)buf; 645 patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK)); 646 q = buf + 0x5000; 647 patch_instruction(q, translate_branch(q, p)); 648 check(instr_is_branch_to_addr(p, addr)); 649 check(instr_is_branch_to_addr(q, addr)); 650 651 /* Jump to x + 8 KB moved to x - 8 KB + 4 */ 652 p = buf + 0x2000; 653 addr = 0x4000 + (unsigned long)buf; 654 patch_instruction(p, create_cond_branch(p, addr, 0)); 655 q = buf + 4; 656 patch_instruction(q, translate_branch(q, p)); 657 check(instr_is_branch_to_addr(p, addr)); 658 check(instr_is_branch_to_addr(q, addr)); 659 660 /* Free the buffer we were using */ 661 vfree(buf); 662 } 663 664 static int __init test_code_patching(void) 665 { 666 printk(KERN_DEBUG "Running code patching self-tests ...\n"); 667 668 test_branch_iform(); 669 test_branch_bform(); 670 test_create_function_call(); 671 test_translate_branch(); 672 673 return 0; 674 } 675 late_initcall(test_code_patching); 676 677 #endif /* CONFIG_CODE_PATCHING_SELFTEST */ 678