2 * Copyright 2008 Michael Ellerman, IBM Corporation.
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.
10 #include <linux/kernel.h>
11 #include <linux/kprobes.h>
12 #include <linux/vmalloc.h>
13 #include <linux/init.h>
15 #include <linux/cpuhotplug.h>
16 #include <linux/slab.h>
17 #include <linux/uaccess.h>
18 #include <linux/kprobes.h>
20 #include <asm/pgtable.h>
21 #include <asm/tlbflush.h>
23 #include <asm/code-patching.h>
24 #include <asm/setup.h>
26 static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
27 unsigned int *patch_addr)
31 __put_user_size(instr, patch_addr, 4, err);
35 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
41 int raw_patch_instruction(unsigned int *addr, unsigned int instr)
43 return __patch_instruction(addr, instr, addr);
46 #ifdef CONFIG_STRICT_KERNEL_RWX
47 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
49 static int text_area_cpu_up(unsigned int cpu)
51 struct vm_struct *area;
53 area = get_vm_area(PAGE_SIZE, VM_ALLOC);
55 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
59 this_cpu_write(text_poke_area, area);
64 static int text_area_cpu_down(unsigned int cpu)
66 free_vm_area(this_cpu_read(text_poke_area));
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().
78 static int __init setup_text_poke_area(void)
80 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
81 "powerpc/text_poke:online", text_area_cpu_up,
86 late_initcall(setup_text_poke_area);
89 * This can be called for kernel text or a module.
91 static int map_patch_area(void *addr, unsigned long text_poke_addr)
96 if (is_vmalloc_addr(addr))
97 pfn = vmalloc_to_pfn(addr);
99 pfn = __pa_symbol(addr) >> PAGE_SHIFT;
101 err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT),
102 pgprot_val(PAGE_KERNEL));
104 pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
111 static inline int unmap_patch_area(unsigned long addr)
118 pgdp = pgd_offset_k(addr);
122 pudp = pud_offset(pgdp, addr);
126 pmdp = pmd_offset(pudp, addr);
130 ptep = pte_offset_kernel(pmdp, addr);
134 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);
137 * In hash, pte_clear flushes the tlb, in radix, we have to
139 pte_clear(&init_mm, addr, ptep);
140 flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
145 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
148 unsigned int *patch_addr = NULL;
150 unsigned long text_poke_addr;
151 unsigned long kaddr = (unsigned long)addr;
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
158 if (!this_cpu_read(text_poke_area))
159 return raw_patch_instruction(addr, instr);
161 local_irq_save(flags);
163 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
164 if (map_patch_area(addr, text_poke_addr)) {
169 patch_addr = (unsigned int *)(text_poke_addr) +
170 ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
172 __patch_instruction(addr, instr, patch_addr);
174 err = unmap_patch_area(text_poke_addr);
176 pr_warn("failed to unmap %lx\n", text_poke_addr);
179 local_irq_restore(flags);
183 #else /* !CONFIG_STRICT_KERNEL_RWX */
185 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
187 return raw_patch_instruction(addr, instr);
190 #endif /* CONFIG_STRICT_KERNEL_RWX */
192 int patch_instruction(unsigned int *addr, unsigned int instr)
194 /* Make sure we aren't patching a freed init section */
195 if (init_mem_is_free && init_section_contains(addr, 4)) {
196 pr_debug("Skipping init section patching addr: 0x%px\n", addr);
199 return do_patch_instruction(addr, instr);
201 NOKPROBE_SYMBOL(patch_instruction);
203 int patch_branch(unsigned int *addr, unsigned long target, int flags)
205 return patch_instruction(addr, create_branch(addr, target, flags));
208 int patch_branch_site(s32 *site, unsigned long target, int flags)
212 addr = (unsigned int *)((unsigned long)site + *site);
213 return patch_instruction(addr, create_branch(addr, target, flags));
216 int patch_instruction_site(s32 *site, unsigned int instr)
220 addr = (unsigned int *)((unsigned long)site + *site);
221 return patch_instruction(addr, instr);
224 bool is_offset_in_branch_range(long offset)
227 * Powerpc branch instruction is :
230 * +---------+----------------+---+---+
231 * | opcode | LI |AA |LK |
232 * +---------+----------------+---+---+
233 * Where AA = 0 and LK = 0
235 * LI is a signed 24 bits integer. The real branch offset is computed
236 * by: imm32 = SignExtend(LI:'0b00', 32);
238 * So the maximum forward branch should be:
239 * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc
240 * The maximum backward branch should be:
241 * (0xff800000 << 2) = 0xfe000000 = -0x2000000
243 return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
246 bool is_offset_in_cond_branch_range(long offset)
248 return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
252 * Helper to check if a given instruction is a conditional branch
253 * Derived from the conditional checks in analyse_instr()
255 bool is_conditional_branch(unsigned int instr)
257 unsigned int opcode = instr >> 26;
259 if (opcode == 16) /* bc, bca, bcl, bcla */
262 switch ((instr >> 1) & 0x3ff) {
263 case 16: /* bclr, bclrl */
264 case 528: /* bcctr, bcctrl */
265 case 560: /* bctar, bctarl */
271 NOKPROBE_SYMBOL(is_conditional_branch);
273 unsigned int create_branch(const unsigned int *addr,
274 unsigned long target, int flags)
276 unsigned int instruction;
280 if (! (flags & BRANCH_ABSOLUTE))
281 offset = offset - (unsigned long)addr;
283 /* Check we can represent the target in the instruction format */
284 if (!is_offset_in_branch_range(offset))
287 /* Mask out the flags and target, so they don't step on each other. */
288 instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
293 unsigned int create_cond_branch(const unsigned int *addr,
294 unsigned long target, int flags)
296 unsigned int instruction;
300 if (! (flags & BRANCH_ABSOLUTE))
301 offset = offset - (unsigned long)addr;
303 /* Check we can represent the target in the instruction format */
304 if (!is_offset_in_cond_branch_range(offset))
307 /* Mask out the flags and target, so they don't step on each other. */
308 instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
313 static unsigned int branch_opcode(unsigned int instr)
315 return (instr >> 26) & 0x3F;
318 static int instr_is_branch_iform(unsigned int instr)
320 return branch_opcode(instr) == 18;
323 static int instr_is_branch_bform(unsigned int instr)
325 return branch_opcode(instr) == 16;
328 int instr_is_relative_branch(unsigned int instr)
330 if (instr & BRANCH_ABSOLUTE)
333 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
336 int instr_is_relative_link_branch(unsigned int instr)
338 return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
341 static unsigned long branch_iform_target(const unsigned int *instr)
345 imm = *instr & 0x3FFFFFC;
347 /* If the top bit of the immediate value is set this is negative */
351 if ((*instr & BRANCH_ABSOLUTE) == 0)
352 imm += (unsigned long)instr;
354 return (unsigned long)imm;
357 static unsigned long branch_bform_target(const unsigned int *instr)
361 imm = *instr & 0xFFFC;
363 /* If the top bit of the immediate value is set this is negative */
367 if ((*instr & BRANCH_ABSOLUTE) == 0)
368 imm += (unsigned long)instr;
370 return (unsigned long)imm;
373 unsigned long branch_target(const unsigned int *instr)
375 if (instr_is_branch_iform(*instr))
376 return branch_iform_target(instr);
377 else if (instr_is_branch_bform(*instr))
378 return branch_bform_target(instr);
383 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
385 if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
386 return branch_target(instr) == addr;
391 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
393 unsigned long target;
395 target = branch_target(src);
397 if (instr_is_branch_iform(*src))
398 return create_branch(dest, target, *src);
399 else if (instr_is_branch_bform(*src))
400 return create_cond_branch(dest, target, *src);
405 #ifdef CONFIG_PPC_BOOK3E_64
406 void __patch_exception(int exc, unsigned long addr)
408 extern unsigned int interrupt_base_book3e;
409 unsigned int *ibase = &interrupt_base_book3e;
411 /* Our exceptions vectors start with a NOP and -then- a branch
412 * to deal with single stepping from userspace which stops on
413 * the second instruction. Thus we need to patch the second
414 * instruction of the exception, not the first one
417 patch_branch(ibase + (exc / 4) + 1, addr, 0);
421 #ifdef CONFIG_CODE_PATCHING_SELFTEST
423 static void __init test_trampoline(void)
429 if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
431 static void __init test_branch_iform(void)
436 addr = (unsigned long)&instr;
438 /* The simplest case, branch to self, no flags */
439 check(instr_is_branch_iform(0x48000000));
440 /* All bits of target set, and flags */
441 check(instr_is_branch_iform(0x4bffffff));
442 /* High bit of opcode set, which is wrong */
443 check(!instr_is_branch_iform(0xcbffffff));
444 /* Middle bits of opcode set, which is wrong */
445 check(!instr_is_branch_iform(0x7bffffff));
447 /* Simplest case, branch to self with link */
448 check(instr_is_branch_iform(0x48000001));
449 /* All bits of targets set */
450 check(instr_is_branch_iform(0x4bfffffd));
451 /* Some bits of targets set */
452 check(instr_is_branch_iform(0x4bff00fd));
453 /* Must be a valid branch to start with */
454 check(!instr_is_branch_iform(0x7bfffffd));
456 /* Absolute branch to 0x100 */
458 check(instr_is_branch_to_addr(&instr, 0x100));
459 /* Absolute branch to 0x420fc */
461 check(instr_is_branch_to_addr(&instr, 0x420fc));
462 /* Maximum positive relative branch, + 20MB - 4B */
464 check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
465 /* Smallest negative relative branch, - 4B */
467 check(instr_is_branch_to_addr(&instr, addr - 4));
468 /* Largest negative relative branch, - 32 MB */
470 check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
472 /* Branch to self, with link */
473 instr = create_branch(&instr, addr, BRANCH_SET_LINK);
474 check(instr_is_branch_to_addr(&instr, addr));
476 /* Branch to self - 0x100, with link */
477 instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
478 check(instr_is_branch_to_addr(&instr, addr - 0x100));
480 /* Branch to self + 0x100, no link */
481 instr = create_branch(&instr, addr + 0x100, 0);
482 check(instr_is_branch_to_addr(&instr, addr + 0x100));
484 /* Maximum relative negative offset, - 32 MB */
485 instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
486 check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
488 /* Out of range relative negative offset, - 32 MB + 4*/
489 instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
492 /* Out of range relative positive offset, + 32 MB */
493 instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
496 /* Unaligned target */
497 instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
500 /* Check flags are masked correctly */
501 instr = create_branch(&instr, addr, 0xFFFFFFFC);
502 check(instr_is_branch_to_addr(&instr, addr));
503 check(instr == 0x48000000);
506 static void __init test_create_function_call(void)
511 /* Check we can create a function call */
512 iptr = (unsigned int *)ppc_function_entry(test_trampoline);
513 dest = ppc_function_entry(test_create_function_call);
514 patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
515 check(instr_is_branch_to_addr(iptr, dest));
518 static void __init test_branch_bform(void)
521 unsigned int *iptr, instr, flags;
524 addr = (unsigned long)iptr;
526 /* The simplest case, branch to self, no flags */
527 check(instr_is_branch_bform(0x40000000));
528 /* All bits of target set, and flags */
529 check(instr_is_branch_bform(0x43ffffff));
530 /* High bit of opcode set, which is wrong */
531 check(!instr_is_branch_bform(0xc3ffffff));
532 /* Middle bits of opcode set, which is wrong */
533 check(!instr_is_branch_bform(0x7bffffff));
535 /* Absolute conditional branch to 0x100 */
537 check(instr_is_branch_to_addr(&instr, 0x100));
538 /* Absolute conditional branch to 0x20fc */
540 check(instr_is_branch_to_addr(&instr, 0x20fc));
541 /* Maximum positive relative conditional branch, + 32 KB - 4B */
543 check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
544 /* Smallest negative relative conditional branch, - 4B */
546 check(instr_is_branch_to_addr(&instr, addr - 4));
547 /* Largest negative relative conditional branch, - 32 KB */
549 check(instr_is_branch_to_addr(&instr, addr - 0x8000));
551 /* All condition code bits set & link */
552 flags = 0x3ff000 | BRANCH_SET_LINK;
555 instr = create_cond_branch(iptr, addr, flags);
556 check(instr_is_branch_to_addr(&instr, addr));
558 /* Branch to self - 0x100 */
559 instr = create_cond_branch(iptr, addr - 0x100, flags);
560 check(instr_is_branch_to_addr(&instr, addr - 0x100));
562 /* Branch to self + 0x100 */
563 instr = create_cond_branch(iptr, addr + 0x100, flags);
564 check(instr_is_branch_to_addr(&instr, addr + 0x100));
566 /* Maximum relative negative offset, - 32 KB */
567 instr = create_cond_branch(iptr, addr - 0x8000, flags);
568 check(instr_is_branch_to_addr(&instr, addr - 0x8000));
570 /* Out of range relative negative offset, - 32 KB + 4*/
571 instr = create_cond_branch(iptr, addr - 0x8004, flags);
574 /* Out of range relative positive offset, + 32 KB */
575 instr = create_cond_branch(iptr, addr + 0x8000, flags);
578 /* Unaligned target */
579 instr = create_cond_branch(iptr, addr + 3, flags);
582 /* Check flags are masked correctly */
583 instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
584 check(instr_is_branch_to_addr(&instr, addr));
585 check(instr == 0x43FF0000);
588 static void __init test_translate_branch(void)
594 buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
599 /* Simple case, branch to self moved a little */
601 addr = (unsigned long)p;
602 patch_branch(p, addr, 0);
603 check(instr_is_branch_to_addr(p, addr));
605 patch_instruction(q, translate_branch(q, p));
606 check(instr_is_branch_to_addr(q, addr));
608 /* Maximum negative case, move b . to addr + 32 MB */
610 addr = (unsigned long)p;
611 patch_branch(p, addr, 0);
613 patch_instruction(q, translate_branch(q, p));
614 check(instr_is_branch_to_addr(p, addr));
615 check(instr_is_branch_to_addr(q, addr));
616 check(*q == 0x4a000000);
618 /* Maximum positive case, move x to x - 32 MB + 4 */
620 addr = (unsigned long)p;
621 patch_branch(p, addr, 0);
623 patch_instruction(q, translate_branch(q, p));
624 check(instr_is_branch_to_addr(p, addr));
625 check(instr_is_branch_to_addr(q, addr));
626 check(*q == 0x49fffffc);
628 /* Jump to x + 16 MB moved to x + 20 MB */
630 addr = 0x1000000 + (unsigned long)buf;
631 patch_branch(p, addr, BRANCH_SET_LINK);
633 patch_instruction(q, translate_branch(q, p));
634 check(instr_is_branch_to_addr(p, addr));
635 check(instr_is_branch_to_addr(q, addr));
637 /* Jump to x + 16 MB moved to x - 16 MB + 4 */
639 addr = 0x2000000 + (unsigned long)buf;
640 patch_branch(p, addr, 0);
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));
647 /* Conditional branch tests */
649 /* Simple case, branch to self moved a little */
651 addr = (unsigned long)p;
652 patch_instruction(p, create_cond_branch(p, addr, 0));
653 check(instr_is_branch_to_addr(p, addr));
655 patch_instruction(q, translate_branch(q, p));
656 check(instr_is_branch_to_addr(q, addr));
658 /* Maximum negative case, move b . to addr + 32 KB */
660 addr = (unsigned long)p;
661 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
663 patch_instruction(q, translate_branch(q, p));
664 check(instr_is_branch_to_addr(p, addr));
665 check(instr_is_branch_to_addr(q, addr));
666 check(*q == 0x43ff8000);
668 /* Maximum positive case, move x to x - 32 KB + 4 */
670 addr = (unsigned long)p;
671 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
673 patch_instruction(q, translate_branch(q, p));
674 check(instr_is_branch_to_addr(p, addr));
675 check(instr_is_branch_to_addr(q, addr));
676 check(*q == 0x43ff7ffc);
678 /* Jump to x + 12 KB moved to x + 20 KB */
680 addr = 0x3000 + (unsigned long)buf;
681 patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
683 patch_instruction(q, translate_branch(q, p));
684 check(instr_is_branch_to_addr(p, addr));
685 check(instr_is_branch_to_addr(q, addr));
687 /* Jump to x + 8 KB moved to x - 8 KB + 4 */
689 addr = 0x4000 + (unsigned long)buf;
690 patch_instruction(p, create_cond_branch(p, addr, 0));
692 patch_instruction(q, translate_branch(q, p));
693 check(instr_is_branch_to_addr(p, addr));
694 check(instr_is_branch_to_addr(q, addr));
696 /* Free the buffer we were using */
700 static int __init test_code_patching(void)
702 printk(KERN_DEBUG "Running code patching self-tests ...\n");
706 test_create_function_call();
707 test_translate_branch();
711 late_initcall(test_code_patching);
713 #endif /* CONFIG_CODE_PATCHING_SELFTEST */