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 *addr
, unsigned int instr
)
30 __put_user_size(instr
, addr
, 4, err
);
34 asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" :: "r" (addr
));
39 #ifdef CONFIG_STRICT_KERNEL_RWX
40 static DEFINE_PER_CPU(struct vm_struct
*, text_poke_area
);
42 static int text_area_cpu_up(unsigned int cpu
)
44 struct vm_struct
*area
;
46 area
= get_vm_area(PAGE_SIZE
, VM_ALLOC
);
48 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
52 this_cpu_write(text_poke_area
, area
);
57 static int text_area_cpu_down(unsigned int cpu
)
59 free_vm_area(this_cpu_read(text_poke_area
));
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().
71 static int __init
setup_text_poke_area(void)
73 BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN
,
74 "powerpc/text_poke:online", text_area_cpu_up
,
79 late_initcall(setup_text_poke_area
);
82 * This can be called for kernel text or a module.
84 static int map_patch_area(void *addr
, unsigned long text_poke_addr
)
89 if (is_vmalloc_addr(addr
))
90 pfn
= vmalloc_to_pfn(addr
);
92 pfn
= __pa_symbol(addr
) >> PAGE_SHIFT
;
94 err
= map_kernel_page(text_poke_addr
, (pfn
<< PAGE_SHIFT
),
95 pgprot_val(PAGE_KERNEL
));
97 pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr
, pfn
, err
);
104 static inline int unmap_patch_area(unsigned long addr
)
111 pgdp
= pgd_offset_k(addr
);
115 pudp
= pud_offset(pgdp
, addr
);
119 pmdp
= pmd_offset(pudp
, addr
);
123 ptep
= pte_offset_kernel(pmdp
, addr
);
127 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm
, ptep
, addr
);
130 * In hash, pte_clear flushes the tlb, in radix, we have to
132 pte_clear(&init_mm
, addr
, ptep
);
133 flush_tlb_kernel_range(addr
, addr
+ PAGE_SIZE
);
138 int patch_instruction(unsigned int *addr
, unsigned int instr
)
141 unsigned int *dest
= NULL
;
143 unsigned long text_poke_addr
;
144 unsigned long kaddr
= (unsigned long)addr
;
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
151 if (!this_cpu_read(*PTRRELOC(&text_poke_area
)))
152 return __patch_instruction(addr
, instr
);
154 local_irq_save(flags
);
156 text_poke_addr
= (unsigned long)__this_cpu_read(text_poke_area
)->addr
;
157 if (map_patch_area(addr
, text_poke_addr
)) {
162 dest
= (unsigned int *)(text_poke_addr
) +
163 ((kaddr
& ~PAGE_MASK
) / sizeof(unsigned int));
166 * We use __put_user_size so that we can handle faults while
167 * writing to dest and return err to handle faults gracefully
169 __put_user_size(instr
, dest
, 4, err
);
171 asm ("dcbst 0, %0; sync; icbi 0,%0; icbi 0,%1; sync; isync"
172 ::"r" (dest
), "r"(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 int patch_instruction(unsigned int *addr
, unsigned int instr
)
187 return __patch_instruction(addr
, instr
);
190 #endif /* CONFIG_STRICT_KERNEL_RWX */
191 NOKPROBE_SYMBOL(patch_instruction
);
193 int patch_branch(unsigned int *addr
, unsigned long target
, int flags
)
195 return patch_instruction(addr
, create_branch(addr
, target
, flags
));
198 bool is_offset_in_branch_range(long offset
)
201 * Powerpc branch instruction is :
204 * +---------+----------------+---+---+
205 * | opcode | LI |AA |LK |
206 * +---------+----------------+---+---+
207 * Where AA = 0 and LK = 0
209 * LI is a signed 24 bits integer. The real branch offset is computed
210 * by: imm32 = SignExtend(LI:'0b00', 32);
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
217 return (offset
>= -0x2000000 && offset
<= 0x1fffffc && !(offset
& 0x3));
221 * Helper to check if a given instruction is a conditional branch
222 * Derived from the conditional checks in analyse_instr()
224 bool is_conditional_branch(unsigned int instr
)
226 unsigned int opcode
= instr
>> 26;
228 if (opcode
== 16) /* bc, bca, bcl, bcla */
231 switch ((instr
>> 1) & 0x3ff) {
232 case 16: /* bclr, bclrl */
233 case 528: /* bcctr, bcctrl */
234 case 560: /* bctar, bctarl */
240 NOKPROBE_SYMBOL(is_conditional_branch
);
242 unsigned int create_branch(const unsigned int *addr
,
243 unsigned long target
, int flags
)
245 unsigned int instruction
;
249 if (! (flags
& BRANCH_ABSOLUTE
))
250 offset
= offset
- (unsigned long)addr
;
252 /* Check we can represent the target in the instruction format */
253 if (!is_offset_in_branch_range(offset
))
256 /* Mask out the flags and target, so they don't step on each other. */
257 instruction
= 0x48000000 | (flags
& 0x3) | (offset
& 0x03FFFFFC);
262 unsigned int create_cond_branch(const unsigned int *addr
,
263 unsigned long target
, int flags
)
265 unsigned int instruction
;
269 if (! (flags
& BRANCH_ABSOLUTE
))
270 offset
= offset
- (unsigned long)addr
;
272 /* Check we can represent the target in the instruction format */
273 if (offset
< -0x8000 || offset
> 0x7FFF || offset
& 0x3)
276 /* Mask out the flags and target, so they don't step on each other. */
277 instruction
= 0x40000000 | (flags
& 0x3FF0003) | (offset
& 0xFFFC);
282 static unsigned int branch_opcode(unsigned int instr
)
284 return (instr
>> 26) & 0x3F;
287 static int instr_is_branch_iform(unsigned int instr
)
289 return branch_opcode(instr
) == 18;
292 static int instr_is_branch_bform(unsigned int instr
)
294 return branch_opcode(instr
) == 16;
297 int instr_is_relative_branch(unsigned int instr
)
299 if (instr
& BRANCH_ABSOLUTE
)
302 return instr_is_branch_iform(instr
) || instr_is_branch_bform(instr
);
305 static unsigned long branch_iform_target(const unsigned int *instr
)
309 imm
= *instr
& 0x3FFFFFC;
311 /* If the top bit of the immediate value is set this is negative */
315 if ((*instr
& BRANCH_ABSOLUTE
) == 0)
316 imm
+= (unsigned long)instr
;
318 return (unsigned long)imm
;
321 static unsigned long branch_bform_target(const unsigned int *instr
)
325 imm
= *instr
& 0xFFFC;
327 /* If the top bit of the immediate value is set this is negative */
331 if ((*instr
& BRANCH_ABSOLUTE
) == 0)
332 imm
+= (unsigned long)instr
;
334 return (unsigned long)imm
;
337 unsigned long branch_target(const unsigned int *instr
)
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
);
347 int instr_is_branch_to_addr(const unsigned int *instr
, unsigned long addr
)
349 if (instr_is_branch_iform(*instr
) || instr_is_branch_bform(*instr
))
350 return branch_target(instr
) == addr
;
355 unsigned int translate_branch(const unsigned int *dest
, const unsigned int *src
)
357 unsigned long target
;
359 target
= branch_target(src
);
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
);
369 #ifdef CONFIG_PPC_BOOK3E_64
370 void __patch_exception(int exc
, unsigned long addr
)
372 extern unsigned int interrupt_base_book3e
;
373 unsigned int *ibase
= &interrupt_base_book3e
;
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
381 patch_branch(ibase
+ (exc
/ 4) + 1, addr
, 0);
385 #ifdef CONFIG_CODE_PATCHING_SELFTEST
387 static void __init
test_trampoline(void)
393 if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
395 static void __init
test_branch_iform(void)
400 addr
= (unsigned long)&instr
;
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));
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));
420 /* Absolute branch to 0x100 */
422 check(instr_is_branch_to_addr(&instr
, 0x100));
423 /* Absolute branch to 0x420fc */
425 check(instr_is_branch_to_addr(&instr
, 0x420fc));
426 /* Maximum positive relative branch, + 20MB - 4B */
428 check(instr_is_branch_to_addr(&instr
, addr
+ 0x1FFFFFC));
429 /* Smallest negative relative branch, - 4B */
431 check(instr_is_branch_to_addr(&instr
, addr
- 4));
432 /* Largest negative relative branch, - 32 MB */
434 check(instr_is_branch_to_addr(&instr
, addr
- 0x2000000));
436 /* Branch to self, with link */
437 instr
= create_branch(&instr
, addr
, BRANCH_SET_LINK
);
438 check(instr_is_branch_to_addr(&instr
, addr
));
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));
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));
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));
452 /* Out of range relative negative offset, - 32 MB + 4*/
453 instr
= create_branch(&instr
, addr
- 0x2000004, BRANCH_SET_LINK
);
456 /* Out of range relative positive offset, + 32 MB */
457 instr
= create_branch(&instr
, addr
+ 0x2000000, BRANCH_SET_LINK
);
460 /* Unaligned target */
461 instr
= create_branch(&instr
, addr
+ 3, BRANCH_SET_LINK
);
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);
470 static void __init
test_create_function_call(void)
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
));
482 static void __init
test_branch_bform(void)
485 unsigned int *iptr
, instr
, flags
;
488 addr
= (unsigned long)iptr
;
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));
499 /* Absolute conditional branch to 0x100 */
501 check(instr_is_branch_to_addr(&instr
, 0x100));
502 /* Absolute conditional branch to 0x20fc */
504 check(instr_is_branch_to_addr(&instr
, 0x20fc));
505 /* Maximum positive relative conditional branch, + 32 KB - 4B */
507 check(instr_is_branch_to_addr(&instr
, addr
+ 0x7FFC));
508 /* Smallest negative relative conditional branch, - 4B */
510 check(instr_is_branch_to_addr(&instr
, addr
- 4));
511 /* Largest negative relative conditional branch, - 32 KB */
513 check(instr_is_branch_to_addr(&instr
, addr
- 0x8000));
515 /* All condition code bits set & link */
516 flags
= 0x3ff000 | BRANCH_SET_LINK
;
519 instr
= create_cond_branch(iptr
, addr
, flags
);
520 check(instr_is_branch_to_addr(&instr
, addr
));
522 /* Branch to self - 0x100 */
523 instr
= create_cond_branch(iptr
, addr
- 0x100, flags
);
524 check(instr_is_branch_to_addr(&instr
, addr
- 0x100));
526 /* Branch to self + 0x100 */
527 instr
= create_cond_branch(iptr
, addr
+ 0x100, flags
);
528 check(instr_is_branch_to_addr(&instr
, addr
+ 0x100));
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));
534 /* Out of range relative negative offset, - 32 KB + 4*/
535 instr
= create_cond_branch(iptr
, addr
- 0x8004, flags
);
538 /* Out of range relative positive offset, + 32 KB */
539 instr
= create_cond_branch(iptr
, addr
+ 0x8000, flags
);
542 /* Unaligned target */
543 instr
= create_cond_branch(iptr
, addr
+ 3, flags
);
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);
552 static void __init
test_translate_branch(void)
558 buf
= vmalloc(PAGE_ALIGN(0x2000000 + 1));
563 /* Simple case, branch to self moved a little */
565 addr
= (unsigned long)p
;
566 patch_branch(p
, addr
, 0);
567 check(instr_is_branch_to_addr(p
, addr
));
569 patch_instruction(q
, translate_branch(q
, p
));
570 check(instr_is_branch_to_addr(q
, addr
));
572 /* Maximum negative case, move b . to addr + 32 MB */
574 addr
= (unsigned long)p
;
575 patch_branch(p
, addr
, 0);
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);
582 /* Maximum positive case, move x to x - 32 MB + 4 */
584 addr
= (unsigned long)p
;
585 patch_branch(p
, addr
, 0);
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);
592 /* Jump to x + 16 MB moved to x + 20 MB */
594 addr
= 0x1000000 + (unsigned long)buf
;
595 patch_branch(p
, addr
, BRANCH_SET_LINK
);
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
));
601 /* Jump to x + 16 MB moved to x - 16 MB + 4 */
603 addr
= 0x2000000 + (unsigned long)buf
;
604 patch_branch(p
, addr
, 0);
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
));
611 /* Conditional branch tests */
613 /* Simple case, branch to self moved a little */
615 addr
= (unsigned long)p
;
616 patch_instruction(p
, create_cond_branch(p
, addr
, 0));
617 check(instr_is_branch_to_addr(p
, addr
));
619 patch_instruction(q
, translate_branch(q
, p
));
620 check(instr_is_branch_to_addr(q
, addr
));
622 /* Maximum negative case, move b . to addr + 32 KB */
624 addr
= (unsigned long)p
;
625 patch_instruction(p
, create_cond_branch(p
, addr
, 0xFFFFFFFC));
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);
632 /* Maximum positive case, move x to x - 32 KB + 4 */
634 addr
= (unsigned long)p
;
635 patch_instruction(p
, create_cond_branch(p
, addr
, 0xFFFFFFFC));
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);
642 /* Jump to x + 12 KB moved to x + 20 KB */
644 addr
= 0x3000 + (unsigned long)buf
;
645 patch_instruction(p
, create_cond_branch(p
, addr
, BRANCH_SET_LINK
));
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
));
651 /* Jump to x + 8 KB moved to x - 8 KB + 4 */
653 addr
= 0x4000 + (unsigned long)buf
;
654 patch_instruction(p
, create_cond_branch(p
, addr
, 0));
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
));
660 /* Free the buffer we were using */
664 static int __init
test_code_patching(void)
666 printk(KERN_DEBUG
"Running code patching self-tests ...\n");
670 test_create_function_call();
671 test_translate_branch();
675 late_initcall(test_code_patching
);
677 #endif /* CONFIG_CODE_PATCHING_SELFTEST */