1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright 2008 Michael Ellerman, IBM Corporation.
6 #include <linux/kernel.h>
7 #include <linux/kprobes.h>
8 #include <linux/vmalloc.h>
9 #include <linux/init.h>
11 #include <linux/cpuhotplug.h>
12 #include <linux/slab.h>
13 #include <linux/uaccess.h>
15 #include <asm/pgtable.h>
16 #include <asm/tlbflush.h>
18 #include <asm/code-patching.h>
19 #include <asm/setup.h>
21 static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
22 unsigned int *patch_addr)
26 __put_user_asm(instr, patch_addr, err, "stw");
30 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
36 int raw_patch_instruction(unsigned int *addr, unsigned int instr)
38 return __patch_instruction(addr, instr, addr);
41 #ifdef CONFIG_STRICT_KERNEL_RWX
42 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
44 static int text_area_cpu_up(unsigned int cpu)
46 struct vm_struct *area;
48 area = get_vm_area(PAGE_SIZE, VM_ALLOC);
50 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
54 this_cpu_write(text_poke_area, area);
59 static int text_area_cpu_down(unsigned int cpu)
61 free_vm_area(this_cpu_read(text_poke_area));
66 * Run as a late init call. This allows all the boot time patching to be done
67 * simply by patching the code, and then we're called here prior to
68 * mark_rodata_ro(), which happens after all init calls are run. Although
69 * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
70 * it as being preferable to a kernel that will crash later when someone tries
71 * to use patch_instruction().
73 static int __init setup_text_poke_area(void)
75 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
76 "powerpc/text_poke:online", text_area_cpu_up,
81 late_initcall(setup_text_poke_area);
84 * This can be called for kernel text or a module.
86 static int map_patch_area(void *addr, unsigned long text_poke_addr)
91 if (is_vmalloc_addr(addr))
92 pfn = vmalloc_to_pfn(addr);
94 pfn = __pa_symbol(addr) >> PAGE_SHIFT;
96 err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
98 pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
105 static inline int unmap_patch_area(unsigned long addr)
112 pgdp = pgd_offset_k(addr);
116 pudp = pud_offset(pgdp, addr);
120 pmdp = pmd_offset(pudp, addr);
124 ptep = pte_offset_kernel(pmdp, addr);
128 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);
131 * In hash, pte_clear flushes the tlb, in radix, we have to
133 pte_clear(&init_mm, addr, ptep);
134 flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
139 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
142 unsigned int *patch_addr = NULL;
144 unsigned long text_poke_addr;
145 unsigned long kaddr = (unsigned long)addr;
148 * During early early boot patch_instruction is called
149 * when text_poke_area is not ready, but we still need
150 * to allow patching. We just do the plain old patching
152 if (!this_cpu_read(text_poke_area))
153 return raw_patch_instruction(addr, instr);
155 local_irq_save(flags);
157 text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
158 if (map_patch_area(addr, text_poke_addr)) {
163 patch_addr = (unsigned int *)(text_poke_addr) +
164 ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
166 __patch_instruction(addr, instr, patch_addr);
168 err = unmap_patch_area(text_poke_addr);
170 pr_warn("failed to unmap %lx\n", text_poke_addr);
173 local_irq_restore(flags);
177 #else /* !CONFIG_STRICT_KERNEL_RWX */
179 static int do_patch_instruction(unsigned int *addr, unsigned int instr)
181 return raw_patch_instruction(addr, instr);
184 #endif /* CONFIG_STRICT_KERNEL_RWX */
186 int patch_instruction(unsigned int *addr, unsigned int instr)
188 /* Make sure we aren't patching a freed init section */
189 if (init_mem_is_free && init_section_contains(addr, 4)) {
190 pr_debug("Skipping init section patching addr: 0x%px\n", addr);
193 return do_patch_instruction(addr, instr);
195 NOKPROBE_SYMBOL(patch_instruction);
197 int patch_branch(unsigned int *addr, unsigned long target, int flags)
199 return patch_instruction(addr, create_branch(addr, target, flags));
202 bool is_offset_in_branch_range(long offset)
205 * Powerpc branch instruction is :
208 * +---------+----------------+---+---+
209 * | opcode | LI |AA |LK |
210 * +---------+----------------+---+---+
211 * Where AA = 0 and LK = 0
213 * LI is a signed 24 bits integer. The real branch offset is computed
214 * by: imm32 = SignExtend(LI:'0b00', 32);
216 * So the maximum forward branch should be:
217 * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc
218 * The maximum backward branch should be:
219 * (0xff800000 << 2) = 0xfe000000 = -0x2000000
221 return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
224 bool is_offset_in_cond_branch_range(long offset)
226 return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3);
230 * Helper to check if a given instruction is a conditional branch
231 * Derived from the conditional checks in analyse_instr()
233 bool is_conditional_branch(unsigned int instr)
235 unsigned int opcode = instr >> 26;
237 if (opcode == 16) /* bc, bca, bcl, bcla */
240 switch ((instr >> 1) & 0x3ff) {
241 case 16: /* bclr, bclrl */
242 case 528: /* bcctr, bcctrl */
243 case 560: /* bctar, bctarl */
249 NOKPROBE_SYMBOL(is_conditional_branch);
251 unsigned int create_branch(const unsigned int *addr,
252 unsigned long target, int flags)
254 unsigned int instruction;
258 if (! (flags & BRANCH_ABSOLUTE))
259 offset = offset - (unsigned long)addr;
261 /* Check we can represent the target in the instruction format */
262 if (!is_offset_in_branch_range(offset))
265 /* Mask out the flags and target, so they don't step on each other. */
266 instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
271 unsigned int create_cond_branch(const unsigned int *addr,
272 unsigned long target, int flags)
274 unsigned int instruction;
278 if (! (flags & BRANCH_ABSOLUTE))
279 offset = offset - (unsigned long)addr;
281 /* Check we can represent the target in the instruction format */
282 if (!is_offset_in_cond_branch_range(offset))
285 /* Mask out the flags and target, so they don't step on each other. */
286 instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
291 static unsigned int branch_opcode(unsigned int instr)
293 return (instr >> 26) & 0x3F;
296 static int instr_is_branch_iform(unsigned int instr)
298 return branch_opcode(instr) == 18;
301 static int instr_is_branch_bform(unsigned int instr)
303 return branch_opcode(instr) == 16;
306 int instr_is_relative_branch(unsigned int instr)
308 if (instr & BRANCH_ABSOLUTE)
311 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
314 int instr_is_relative_link_branch(unsigned int instr)
316 return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
319 static unsigned long branch_iform_target(const unsigned int *instr)
323 imm = *instr & 0x3FFFFFC;
325 /* If the top bit of the immediate value is set this is negative */
329 if ((*instr & BRANCH_ABSOLUTE) == 0)
330 imm += (unsigned long)instr;
332 return (unsigned long)imm;
335 static unsigned long branch_bform_target(const unsigned int *instr)
339 imm = *instr & 0xFFFC;
341 /* If the top bit of the immediate value is set this is negative */
345 if ((*instr & BRANCH_ABSOLUTE) == 0)
346 imm += (unsigned long)instr;
348 return (unsigned long)imm;
351 unsigned long branch_target(const unsigned int *instr)
353 if (instr_is_branch_iform(*instr))
354 return branch_iform_target(instr);
355 else if (instr_is_branch_bform(*instr))
356 return branch_bform_target(instr);
361 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
363 if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
364 return branch_target(instr) == addr;
369 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
371 unsigned long target;
373 target = branch_target(src);
375 if (instr_is_branch_iform(*src))
376 return create_branch(dest, target, *src);
377 else if (instr_is_branch_bform(*src))
378 return create_cond_branch(dest, target, *src);
383 #ifdef CONFIG_PPC_BOOK3E_64
384 void __patch_exception(int exc, unsigned long addr)
386 extern unsigned int interrupt_base_book3e;
387 unsigned int *ibase = &interrupt_base_book3e;
389 /* Our exceptions vectors start with a NOP and -then- a branch
390 * to deal with single stepping from userspace which stops on
391 * the second instruction. Thus we need to patch the second
392 * instruction of the exception, not the first one
395 patch_branch(ibase + (exc / 4) + 1, addr, 0);
399 #ifdef CONFIG_CODE_PATCHING_SELFTEST
401 static void __init test_trampoline(void)
407 if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
409 static void __init test_branch_iform(void)
414 addr = (unsigned long)&instr;
416 /* The simplest case, branch to self, no flags */
417 check(instr_is_branch_iform(0x48000000));
418 /* All bits of target set, and flags */
419 check(instr_is_branch_iform(0x4bffffff));
420 /* High bit of opcode set, which is wrong */
421 check(!instr_is_branch_iform(0xcbffffff));
422 /* Middle bits of opcode set, which is wrong */
423 check(!instr_is_branch_iform(0x7bffffff));
425 /* Simplest case, branch to self with link */
426 check(instr_is_branch_iform(0x48000001));
427 /* All bits of targets set */
428 check(instr_is_branch_iform(0x4bfffffd));
429 /* Some bits of targets set */
430 check(instr_is_branch_iform(0x4bff00fd));
431 /* Must be a valid branch to start with */
432 check(!instr_is_branch_iform(0x7bfffffd));
434 /* Absolute branch to 0x100 */
436 check(instr_is_branch_to_addr(&instr, 0x100));
437 /* Absolute branch to 0x420fc */
439 check(instr_is_branch_to_addr(&instr, 0x420fc));
440 /* Maximum positive relative branch, + 20MB - 4B */
442 check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
443 /* Smallest negative relative branch, - 4B */
445 check(instr_is_branch_to_addr(&instr, addr - 4));
446 /* Largest negative relative branch, - 32 MB */
448 check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
450 /* Branch to self, with link */
451 instr = create_branch(&instr, addr, BRANCH_SET_LINK);
452 check(instr_is_branch_to_addr(&instr, addr));
454 /* Branch to self - 0x100, with link */
455 instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
456 check(instr_is_branch_to_addr(&instr, addr - 0x100));
458 /* Branch to self + 0x100, no link */
459 instr = create_branch(&instr, addr + 0x100, 0);
460 check(instr_is_branch_to_addr(&instr, addr + 0x100));
462 /* Maximum relative negative offset, - 32 MB */
463 instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
464 check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
466 /* Out of range relative negative offset, - 32 MB + 4*/
467 instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
470 /* Out of range relative positive offset, + 32 MB */
471 instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
474 /* Unaligned target */
475 instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
478 /* Check flags are masked correctly */
479 instr = create_branch(&instr, addr, 0xFFFFFFFC);
480 check(instr_is_branch_to_addr(&instr, addr));
481 check(instr == 0x48000000);
484 static void __init test_create_function_call(void)
489 /* Check we can create a function call */
490 iptr = (unsigned int *)ppc_function_entry(test_trampoline);
491 dest = ppc_function_entry(test_create_function_call);
492 patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
493 check(instr_is_branch_to_addr(iptr, dest));
496 static void __init test_branch_bform(void)
499 unsigned int *iptr, instr, flags;
502 addr = (unsigned long)iptr;
504 /* The simplest case, branch to self, no flags */
505 check(instr_is_branch_bform(0x40000000));
506 /* All bits of target set, and flags */
507 check(instr_is_branch_bform(0x43ffffff));
508 /* High bit of opcode set, which is wrong */
509 check(!instr_is_branch_bform(0xc3ffffff));
510 /* Middle bits of opcode set, which is wrong */
511 check(!instr_is_branch_bform(0x7bffffff));
513 /* Absolute conditional branch to 0x100 */
515 check(instr_is_branch_to_addr(&instr, 0x100));
516 /* Absolute conditional branch to 0x20fc */
518 check(instr_is_branch_to_addr(&instr, 0x20fc));
519 /* Maximum positive relative conditional branch, + 32 KB - 4B */
521 check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
522 /* Smallest negative relative conditional branch, - 4B */
524 check(instr_is_branch_to_addr(&instr, addr - 4));
525 /* Largest negative relative conditional branch, - 32 KB */
527 check(instr_is_branch_to_addr(&instr, addr - 0x8000));
529 /* All condition code bits set & link */
530 flags = 0x3ff000 | BRANCH_SET_LINK;
533 instr = create_cond_branch(iptr, addr, flags);
534 check(instr_is_branch_to_addr(&instr, addr));
536 /* Branch to self - 0x100 */
537 instr = create_cond_branch(iptr, addr - 0x100, flags);
538 check(instr_is_branch_to_addr(&instr, addr - 0x100));
540 /* Branch to self + 0x100 */
541 instr = create_cond_branch(iptr, addr + 0x100, flags);
542 check(instr_is_branch_to_addr(&instr, addr + 0x100));
544 /* Maximum relative negative offset, - 32 KB */
545 instr = create_cond_branch(iptr, addr - 0x8000, flags);
546 check(instr_is_branch_to_addr(&instr, addr - 0x8000));
548 /* Out of range relative negative offset, - 32 KB + 4*/
549 instr = create_cond_branch(iptr, addr - 0x8004, flags);
552 /* Out of range relative positive offset, + 32 KB */
553 instr = create_cond_branch(iptr, addr + 0x8000, flags);
556 /* Unaligned target */
557 instr = create_cond_branch(iptr, addr + 3, flags);
560 /* Check flags are masked correctly */
561 instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
562 check(instr_is_branch_to_addr(&instr, addr));
563 check(instr == 0x43FF0000);
566 static void __init test_translate_branch(void)
572 buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
577 /* Simple case, branch to self moved a little */
579 addr = (unsigned long)p;
580 patch_branch(p, addr, 0);
581 check(instr_is_branch_to_addr(p, addr));
583 patch_instruction(q, translate_branch(q, p));
584 check(instr_is_branch_to_addr(q, addr));
586 /* Maximum negative case, move b . to addr + 32 MB */
588 addr = (unsigned long)p;
589 patch_branch(p, addr, 0);
591 patch_instruction(q, translate_branch(q, p));
592 check(instr_is_branch_to_addr(p, addr));
593 check(instr_is_branch_to_addr(q, addr));
594 check(*q == 0x4a000000);
596 /* Maximum positive case, move x to x - 32 MB + 4 */
598 addr = (unsigned long)p;
599 patch_branch(p, addr, 0);
601 patch_instruction(q, translate_branch(q, p));
602 check(instr_is_branch_to_addr(p, addr));
603 check(instr_is_branch_to_addr(q, addr));
604 check(*q == 0x49fffffc);
606 /* Jump to x + 16 MB moved to x + 20 MB */
608 addr = 0x1000000 + (unsigned long)buf;
609 patch_branch(p, addr, BRANCH_SET_LINK);
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));
615 /* Jump to x + 16 MB moved to x - 16 MB + 4 */
617 addr = 0x2000000 + (unsigned long)buf;
618 patch_branch(p, addr, 0);
620 patch_instruction(q, translate_branch(q, p));
621 check(instr_is_branch_to_addr(p, addr));
622 check(instr_is_branch_to_addr(q, addr));
625 /* Conditional branch tests */
627 /* Simple case, branch to self moved a little */
629 addr = (unsigned long)p;
630 patch_instruction(p, create_cond_branch(p, addr, 0));
631 check(instr_is_branch_to_addr(p, addr));
633 patch_instruction(q, translate_branch(q, p));
634 check(instr_is_branch_to_addr(q, addr));
636 /* Maximum negative case, move b . to addr + 32 KB */
638 addr = (unsigned long)p;
639 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
641 patch_instruction(q, translate_branch(q, p));
642 check(instr_is_branch_to_addr(p, addr));
643 check(instr_is_branch_to_addr(q, addr));
644 check(*q == 0x43ff8000);
646 /* Maximum positive case, move x to x - 32 KB + 4 */
648 addr = (unsigned long)p;
649 patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
651 patch_instruction(q, translate_branch(q, p));
652 check(instr_is_branch_to_addr(p, addr));
653 check(instr_is_branch_to_addr(q, addr));
654 check(*q == 0x43ff7ffc);
656 /* Jump to x + 12 KB moved to x + 20 KB */
658 addr = 0x3000 + (unsigned long)buf;
659 patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
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));
665 /* Jump to x + 8 KB moved to x - 8 KB + 4 */
667 addr = 0x4000 + (unsigned long)buf;
668 patch_instruction(p, create_cond_branch(p, addr, 0));
670 patch_instruction(q, translate_branch(q, p));
671 check(instr_is_branch_to_addr(p, addr));
672 check(instr_is_branch_to_addr(q, addr));
674 /* Free the buffer we were using */
678 static int __init test_code_patching(void)
680 printk(KERN_DEBUG "Running code patching self-tests ...\n");
684 test_create_function_call();
685 test_translate_branch();
689 late_initcall(test_code_patching);
691 #endif /* CONFIG_CODE_PATCHING_SELFTEST */