summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/lib/code-patching.c
blob: 17e5b23643124347febe56a05f5deb7e1a2e361e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
/*
 *  Copyright 2008 Michael Ellerman, IBM Corporation.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <asm/page.h>
#include <asm/code-patching.h>
#include <asm/uaccess.h>


int patch_instruction(unsigned int *addr, unsigned int instr)
{
	int err;

	__put_user_size(instr, addr, 4, err);
	if (err)
		return err;
	asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
	return 0;
}

int patch_branch(unsigned int *addr, unsigned long target, int flags)
{
	return patch_instruction(addr, create_branch(addr, target, flags));
}

unsigned int create_branch(const unsigned int *addr,
			   unsigned long target, int flags)
{
	unsigned int instruction;
	long offset;

	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
		offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
		return 0;

	/* Mask out the flags and target, so they don't step on each other. */
	instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);

	return instruction;
}

unsigned int create_cond_branch(const unsigned int *addr,
				unsigned long target, int flags)
{
	unsigned int instruction;
	long offset;

	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
		offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
		return 0;

	/* Mask out the flags and target, so they don't step on each other. */
	instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);

	return instruction;
}

static unsigned int branch_opcode(unsigned int instr)
{
	return (instr >> 26) & 0x3F;
}

static int instr_is_branch_iform(unsigned int instr)
{
	return branch_opcode(instr) == 18;
}

static int instr_is_branch_bform(unsigned int instr)
{
	return branch_opcode(instr) == 16;
}

int instr_is_relative_branch(unsigned int instr)
{
	if (instr & BRANCH_ABSOLUTE)
		return 0;

	return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
}

static unsigned long branch_iform_target(const unsigned int *instr)
{
	signed long imm;

	imm = *instr & 0x3FFFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x2000000)
		imm -= 0x4000000;

	if ((*instr & BRANCH_ABSOLUTE) == 0)
		imm += (unsigned long)instr;

	return (unsigned long)imm;
}

static unsigned long branch_bform_target(const unsigned int *instr)
{
	signed long imm;

	imm = *instr & 0xFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x8000)
		imm -= 0x10000;

	if ((*instr & BRANCH_ABSOLUTE) == 0)
		imm += (unsigned long)instr;

	return (unsigned long)imm;
}

unsigned long branch_target(const unsigned int *instr)
{
	if (instr_is_branch_iform(*instr))
		return branch_iform_target(instr);
	else if (instr_is_branch_bform(*instr))
		return branch_bform_target(instr);

	return 0;
}

int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
{
	if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
		return branch_target(instr) == addr;

	return 0;
}

unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
{
	unsigned long target;

	target = branch_target(src);

	if (instr_is_branch_iform(*src))
		return create_branch(dest, target, *src);
	else if (instr_is_branch_bform(*src))
		return create_cond_branch(dest, target, *src);

	return 0;
}


#ifdef CONFIG_CODE_PATCHING_SELFTEST

static void __init test_trampoline(void)
{
	asm ("nop;\n");
}

#define check(x)	\
	if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);

static void __init test_branch_iform(void)
{
	unsigned int instr;
	unsigned long addr;

	addr = (unsigned long)&instr;

	/* The simplest case, branch to self, no flags */
	check(instr_is_branch_iform(0x48000000));
	/* All bits of target set, and flags */
	check(instr_is_branch_iform(0x4bffffff));
	/* High bit of opcode set, which is wrong */
	check(!instr_is_branch_iform(0xcbffffff));
	/* Middle bits of opcode set, which is wrong */
	check(!instr_is_branch_iform(0x7bffffff));

	/* Simplest case, branch to self with link */
	check(instr_is_branch_iform(0x48000001));
	/* All bits of targets set */
	check(instr_is_branch_iform(0x4bfffffd));
	/* Some bits of targets set */
	check(instr_is_branch_iform(0x4bff00fd));
	/* Must be a valid branch to start with */
	check(!instr_is_branch_iform(0x7bfffffd));

	/* Absolute branch to 0x100 */
	instr = 0x48000103;
	check(instr_is_branch_to_addr(&instr, 0x100));
	/* Absolute branch to 0x420fc */
	instr = 0x480420ff;
	check(instr_is_branch_to_addr(&instr, 0x420fc));
	/* Maximum positive relative branch, + 20MB - 4B */
	instr = 0x49fffffc;
	check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
	/* Smallest negative relative branch, - 4B */
	instr = 0x4bfffffc;
	check(instr_is_branch_to_addr(&instr, addr - 4));
	/* Largest negative relative branch, - 32 MB */
	instr = 0x4a000000;
	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

	/* Branch to self, with link */
	instr = create_branch(&instr, addr, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr));

	/* Branch to self - 0x100, with link */
	instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr - 0x100));

	/* Branch to self + 0x100, no link */
	instr = create_branch(&instr, addr + 0x100, 0);
	check(instr_is_branch_to_addr(&instr, addr + 0x100));

	/* Maximum relative negative offset, - 32 MB */
	instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

	/* Out of range relative negative offset, - 32 MB + 4*/
	instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
	check(instr == 0);

	/* Out of range relative positive offset, + 32 MB */
	instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
	check(instr == 0);

	/* Unaligned target */
	instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
	check(instr == 0);

	/* Check flags are masked correctly */
	instr = create_branch(&instr, addr, 0xFFFFFFFC);
	check(instr_is_branch_to_addr(&instr, addr));
	check(instr == 0x48000000);
}

static void __init test_create_function_call(void)
{
	unsigned int *iptr;
	unsigned long dest;

	/* Check we can create a function call */
	iptr = (unsigned int *)ppc_function_entry(test_trampoline);
	dest = ppc_function_entry(test_create_function_call);
	patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
	check(instr_is_branch_to_addr(iptr, dest));
}

static void __init test_branch_bform(void)
{
	unsigned long addr;
	unsigned int *iptr, instr, flags;

	iptr = &instr;
	addr = (unsigned long)iptr;

	/* The simplest case, branch to self, no flags */
	check(instr_is_branch_bform(0x40000000));
	/* All bits of target set, and flags */
	check(instr_is_branch_bform(0x43ffffff));
	/* High bit of opcode set, which is wrong */
	check(!instr_is_branch_bform(0xc3ffffff));
	/* Middle bits of opcode set, which is wrong */
	check(!instr_is_branch_bform(0x7bffffff));

	/* Absolute conditional branch to 0x100 */
	instr = 0x43ff0103;
	check(instr_is_branch_to_addr(&instr, 0x100));
	/* Absolute conditional branch to 0x20fc */
	instr = 0x43ff20ff;
	check(instr_is_branch_to_addr(&instr, 0x20fc));
	/* Maximum positive relative conditional branch, + 32 KB - 4B */
	instr = 0x43ff7ffc;
	check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
	/* Smallest negative relative conditional branch, - 4B */
	instr = 0x43fffffc;
	check(instr_is_branch_to_addr(&instr, addr - 4));
	/* Largest negative relative conditional branch, - 32 KB */
	instr = 0x43ff8000;
	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

	/* All condition code bits set & link */
	flags = 0x3ff000 | BRANCH_SET_LINK;

	/* Branch to self */
	instr = create_cond_branch(iptr, addr, flags);
	check(instr_is_branch_to_addr(&instr, addr));

	/* Branch to self - 0x100 */
	instr = create_cond_branch(iptr, addr - 0x100, flags);
	check(instr_is_branch_to_addr(&instr, addr - 0x100));

	/* Branch to self + 0x100 */
	instr = create_cond_branch(iptr, addr + 0x100, flags);
	check(instr_is_branch_to_addr(&instr, addr + 0x100));

	/* Maximum relative negative offset, - 32 KB */
	instr = create_cond_branch(iptr, addr - 0x8000, flags);
	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

	/* Out of range relative negative offset, - 32 KB + 4*/
	instr = create_cond_branch(iptr, addr - 0x8004, flags);
	check(instr == 0);

	/* Out of range relative positive offset, + 32 KB */
	instr = create_cond_branch(iptr, addr + 0x8000, flags);
	check(instr == 0);

	/* Unaligned target */
	instr = create_cond_branch(iptr, addr + 3, flags);
	check(instr == 0);

	/* Check flags are masked correctly */
	instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
	check(instr_is_branch_to_addr(&instr, addr));
	check(instr == 0x43FF0000);
}

static void __init test_translate_branch(void)
{
	unsigned long addr;
	unsigned int *p, *q;
	void *buf;

	buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
	check(buf);
	if (!buf)
		return;

	/* Simple case, branch to self moved a little */
	p = buf;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	check(instr_is_branch_to_addr(p, addr));
	q = p + 1;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(q, addr));

	/* Maximum negative case, move b . to addr + 32 MB */
	p = buf;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	q = buf + 0x2000000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x4a000000);

	/* Maximum positive case, move x to x - 32 MB + 4 */
	p = buf + 0x2000000;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x49fffffc);

	/* Jump to x + 16 MB moved to x + 20 MB */
	p = buf;
	addr = 0x1000000 + (unsigned long)buf;
	patch_branch(p, addr, BRANCH_SET_LINK);
	q = buf + 0x1400000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Jump to x + 16 MB moved to x - 16 MB + 4 */
	p = buf + 0x1000000;
	addr = 0x2000000 + (unsigned long)buf;
	patch_branch(p, addr, 0);
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));


	/* Conditional branch tests */

	/* Simple case, branch to self moved a little */
	p = buf;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0));
	check(instr_is_branch_to_addr(p, addr));
	q = p + 1;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(q, addr));

	/* Maximum negative case, move b . to addr + 32 KB */
	p = buf;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
	q = buf + 0x8000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x43ff8000);

	/* Maximum positive case, move x to x - 32 KB + 4 */
	p = buf + 0x8000;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x43ff7ffc);

	/* Jump to x + 12 KB moved to x + 20 KB */
	p = buf;
	addr = 0x3000 + (unsigned long)buf;
	patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
	q = buf + 0x5000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Jump to x + 8 KB moved to x - 8 KB + 4 */
	p = buf + 0x2000;
	addr = 0x4000 + (unsigned long)buf;
	patch_instruction(p, create_cond_branch(p, addr, 0));
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Free the buffer we were using */
	vfree(buf);
}

static int __init test_code_patching(void)
{
	printk(KERN_DEBUG "Running code patching self-tests ...\n");

	test_branch_iform();
	test_branch_bform();
	test_create_function_call();
	test_translate_branch();

	return 0;
}
late_initcall(test_code_patching);

#endif /* CONFIG_CODE_PATCHING_SELFTEST */