aboutsummaryrefslogtreecommitdiff
path: root/arch/powerpc/kernel/ftrace.c
blob: 3271cd698e4c5e3c10feb264388f7e63a9594e6b (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
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
/*
 * Code for replacing ftrace calls with jumps.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 *
 * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
 *
 */

#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>

#include <asm/cacheflush.h>
#include <asm/code-patching.h>
#include <asm/ftrace.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt , ...)	do { } while (0)
#endif

static unsigned int ftrace_nop = PPC_NOP_INSTR;

#ifdef CONFIG_PPC32
# define GET_ADDR(addr) addr
#else
/* PowerPC64's functions are data that points to the functions */
# define GET_ADDR(addr) (*(unsigned long *)addr)
#endif


static unsigned int ftrace_calc_offset(long ip, long addr)
{
	return (int)(addr - ip);
}

static unsigned char *ftrace_nop_replace(void)
{
	return (char *)&ftrace_nop;
}

static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
	static unsigned int op;

	/*
	 * It would be nice to just use create_function_call, but that will
	 * update the code itself. Here we need to just return the
	 * instruction that is going to be modified, without modifying the
	 * code.
	 */
	addr = GET_ADDR(addr);

	/* Set to "bl addr" */
	op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);

	/*
	 * No locking needed, this must be called via kstop_machine
	 * which in essence is like running on a uniprocessor machine.
	 */
	return (unsigned char *)&op;
}

#ifdef CONFIG_PPC64
# define _ASM_ALIGN	" .align 3 "
# define _ASM_PTR	" .llong "
#else
# define _ASM_ALIGN	" .align 2 "
# define _ASM_PTR	" .long "
#endif

static int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
		   unsigned char *new_code)
{
	unsigned char replaced[MCOUNT_INSN_SIZE];

	/*
	 * Note: Due to modules and __init, code can
	 *  disappear and change, we need to protect against faulting
	 *  as well as code changing. We do this by using the
	 *  probe_kernel_* functions.
	 *
	 * No real locking needed, this code is run through
	 * kstop_machine, or before SMP starts.
	 */

	/* read the text we want to modify */
	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* Make sure it is what we expect it to be */
	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
		return -EINVAL;

	/* replace the text with the new text */
	if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
		return -EPERM;

	flush_icache_range(ip, ip + 8);

	return 0;
}

/*
 * Helper functions that are the same for both PPC64 and PPC32.
 */
static int test_24bit_addr(unsigned long ip, unsigned long addr)
{
	long diff;

	/*
	 * Can we get to addr from ip in 24 bits?
	 *  (26 really, since we mulitply by 4 for 4 byte alignment)
	 */
	diff = addr - ip;

	/*
	 * Return true if diff is less than 1 << 25
	 *  and greater than -1 << 26.
	 */
	return (diff < (1 << 25)) && (diff > (-1 << 26));
}

static int is_bl_op(unsigned int op)
{
	return (op & 0xfc000003) == 0x48000001;
}

static int test_offset(unsigned long offset)
{
	return (offset + 0x2000000 > 0x3ffffff) || ((offset & 3) != 0);
}

static unsigned long find_bl_target(unsigned long ip, unsigned int op)
{
	static int offset;

	offset = (op & 0x03fffffc);
	/* make it signed */
	if (offset & 0x02000000)
		offset |= 0xfe000000;

	return ip + (long)offset;
}

static unsigned int branch_offset(unsigned long offset)
{
	/* return "bl ip+offset" */
	return 0x48000001 | (offset & 0x03fffffc);
}

#ifdef CONFIG_PPC64
static int
__ftrace_make_nop(struct module *mod,
		  struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char replaced[MCOUNT_INSN_SIZE * 2];
	unsigned int *op = (unsigned *)&replaced;
	unsigned char jmp[8];
	unsigned long *ptr = (unsigned long *)&jmp;
	unsigned long ip = rec->ip;
	unsigned long tramp;
	int offset;

	/* read where this goes */
	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(*op)) {
		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
		return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, *op);

	/*
	 * On PPC64 the trampoline looks like:
	 * 0x3d, 0x82, 0x00, 0x00,    addis   r12,r2, <high>
	 * 0x39, 0x8c, 0x00, 0x00,    addi    r12,r12, <low>
	 *   Where the bytes 2,3,6 and 7 make up the 32bit offset
	 *   to the TOC that holds the pointer.
	 *   to jump to.
	 * 0xf8, 0x41, 0x00, 0x28,    std     r2,40(r1)
	 * 0xe9, 0x6c, 0x00, 0x20,    ld      r11,32(r12)
	 *   The actually address is 32 bytes from the offset
	 *   into the TOC.
	 * 0xe8, 0x4c, 0x00, 0x28,    ld      r2,40(r12)
	 */

	DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);

	/* Find where the trampoline jumps to */
	if (probe_kernel_read(jmp, (void *)tramp, 8)) {
		printk(KERN_ERR "Failed to read %lx\n", tramp);
		return -EFAULT;
	}

	DEBUGP(" %08x %08x",
	       (unsigned)(*ptr >> 32),
	       (unsigned)*ptr);

	offset = (unsigned)jmp[2] << 24 |
		(unsigned)jmp[3] << 16 |
		(unsigned)jmp[6] << 8 |
		(unsigned)jmp[7];

	DEBUGP(" %x ", offset);

	/* get the address this jumps too */
	tramp = mod->arch.toc + offset + 32;
	DEBUGP("toc: %lx", tramp);

	if (probe_kernel_read(jmp, (void *)tramp, 8)) {
		printk(KERN_ERR "Failed to read %lx\n", tramp);
		return -EFAULT;
	}

	DEBUGP(" %08x %08x\n",
	       (unsigned)(*ptr >> 32),
	       (unsigned)*ptr);

	/* This should match what was called */
	if (*ptr != GET_ADDR(addr)) {
		printk(KERN_ERR "addr does not match %lx\n", *ptr);
		return -EINVAL;
	}

	/*
	 * We want to nop the line, but the next line is
	 *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)
	 * This needs to be turned to a nop too.
	 */
	if (probe_kernel_read(replaced, (void *)(ip+4), MCOUNT_INSN_SIZE))
		return -EFAULT;

	if (*op != 0xe8410028) {
		printk(KERN_ERR "Next line is not ld! (%08x)\n", *op);
		return -EINVAL;
	}

	/*
	 * Milton Miller pointed out that we can not blindly do nops.
	 * If a task was preempted when calling a trace function,
	 * the nops will remove the way to restore the TOC in r2
	 * and the r2 TOC will get corrupted.
	 */

	/*
	 * Replace:
	 *   bl <tramp>  <==== will be replaced with "b 1f"
	 *   ld r2,40(r1)
	 *  1:
	 */
	op[0] = 0x48000008;	/* b +8 */

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
		return -EPERM;

	return 0;
}

#else /* !PPC64 */
static int
__ftrace_make_nop(struct module *mod,
		  struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char replaced[MCOUNT_INSN_SIZE];
	unsigned int *op = (unsigned *)&replaced;
	unsigned char jmp[8];
	unsigned int *ptr = (unsigned int *)&jmp;
	unsigned long ip = rec->ip;
	unsigned long tramp;
	int offset;

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* Make sure that that this is still a 24bit jump */
	if (!is_bl_op(*op)) {
		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
		return -EINVAL;
	}

	/* lets find where the pointer goes */
	tramp = find_bl_target(ip, *op);

	/*
	 * On PPC32 the trampoline looks like:
	 * lis r11,sym@ha
	 * addi r11,r11,sym@l
	 * mtctr r11
	 * bctr
	 */

	DEBUGP("ip:%lx jumps to %lx", ip, tramp);

	/* Find where the trampoline jumps to */
	if (probe_kernel_read(jmp, (void *)tramp, 8)) {
		printk(KERN_ERR "Failed to read %lx\n", tramp);
		return -EFAULT;
	}

	DEBUGP(" %08x %08x ", ptr[0], ptr[1]);

	tramp = (ptr[1] & 0xffff) |
		((ptr[0] & 0xffff) << 16);
	if (tramp & 0x8000)
		tramp -= 0x10000;

	DEBUGP(" %x ", tramp);

	if (tramp != addr) {
		printk(KERN_ERR
		       "Trampoline location %08lx does not match addr\n",
		       tramp);
		return -EINVAL;
	}

	op[0] = PPC_NOP_INSTR;

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
		return -EPERM;

	return 0;
}
#endif /* PPC64 */

int ftrace_make_nop(struct module *mod,
		    struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char *old, *new;
	unsigned long ip = rec->ip;

	/*
	 * If the calling address is more that 24 bits away,
	 * then we had to use a trampoline to make the call.
	 * Otherwise just update the call site.
	 */
	if (test_24bit_addr(ip, addr)) {
		/* within range */
		old = ftrace_call_replace(ip, addr);
		new = ftrace_nop_replace();
		return ftrace_modify_code(ip, old, new);
	}

	/*
	 * Out of range jumps are called from modules.
	 * We should either already have a pointer to the module
	 * or it has been passed in.
	 */
	if (!rec->arch.mod) {
		if (!mod) {
			printk(KERN_ERR "No module loaded addr=%lx\n",
			       addr);
			return -EFAULT;
		}
		rec->arch.mod = mod;
	} else if (mod) {
		if (mod != rec->arch.mod) {
			printk(KERN_ERR
			       "Record mod %p not equal to passed in mod %p\n",
			       rec->arch.mod, mod);
			return -EINVAL;
		}
		/* nothing to do if mod == rec->arch.mod */
	} else
		mod = rec->arch.mod;

	return __ftrace_make_nop(mod, rec, addr);

}

#ifdef CONFIG_PPC64
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char replaced[MCOUNT_INSN_SIZE * 2];
	unsigned int *op = (unsigned *)&replaced;
	unsigned long ip = rec->ip;
	unsigned long offset;

	/* read where this goes */
	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE * 2))
		return -EFAULT;

	/*
	 * It should be pointing to two nops or
	 *  b +8; ld r2,40(r1)
	 */
	if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
	    ((op[0] != PPC_NOP_INSTR) || (op[1] != PPC_NOP_INSTR))) {
		printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
		return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
		printk(KERN_ERR "No ftrace trampoline\n");
		return -EINVAL;
	}

	/* now calculate a jump to the ftrace caller trampoline */
	offset = rec->arch.mod->arch.tramp - ip;

	if (test_offset(offset)) {
		printk(KERN_ERR "REL24 %li out of range!\n",
		       (long int)offset);
		return -EINVAL;
	}

	/* Set to "bl addr" */
	op[0] = branch_offset(offset);
	/* ld r2,40(r1) */
	op[1] = 0xe8410028;

	DEBUGP("write to %lx\n", rec->ip);

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2))
		return -EPERM;

	return 0;
}
#else
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char replaced[MCOUNT_INSN_SIZE];
	unsigned int *op = (unsigned *)&replaced;
	unsigned long ip = rec->ip;
	unsigned long offset;

	/* read where this goes */
	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
		return -EFAULT;

	/* It should be pointing to a nop */
	if (op[0] != PPC_NOP_INSTR) {
		printk(KERN_ERR "Expected NOP but have %x\n", op[0]);
		return -EINVAL;
	}

	/* If we never set up a trampoline to ftrace_caller, then bail */
	if (!rec->arch.mod->arch.tramp) {
		printk(KERN_ERR "No ftrace trampoline\n");
		return -EINVAL;
	}

	/* now calculate a jump to the ftrace caller trampoline */
	offset = rec->arch.mod->arch.tramp - ip;

	if (test_offset(offset)) {
		printk(KERN_ERR "REL24 %li out of range!\n",
		       (long int)offset);
		return -EINVAL;
	}

	/* Set to "bl addr" */
	op[0] = branch_offset(offset);

	DEBUGP("write to %lx\n", rec->ip);

	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
		return -EPERM;

	return 0;
}
#endif /* CONFIG_PPC64 */

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned char *old, *new;
	unsigned long ip = rec->ip;

	/*
	 * If the calling address is more that 24 bits away,
	 * then we had to use a trampoline to make the call.
	 * Otherwise just update the call site.
	 */
	if (test_24bit_addr(ip, addr)) {
		/* within range */
		old = ftrace_nop_replace();
		new = ftrace_call_replace(ip, addr);
		return ftrace_modify_code(ip, old, new);
	}

	/*
	 * Out of range jumps are called from modules.
	 * Being that we are converting from nop, it had better
	 * already have a module defined.
	 */
	if (!rec->arch.mod) {
		printk(KERN_ERR "No module loaded\n");
		return -EINVAL;
	}

	return __ftrace_make_call(rec, addr);
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned long ip = (unsigned long)(&ftrace_call);
	unsigned char old[MCOUNT_INSN_SIZE], *new;
	int ret;

	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
	new = ftrace_call_replace(ip, (unsigned long)func);
	ret = ftrace_modify_code(ip, old, new);

	return ret;
}

int __init ftrace_dyn_arch_init(void *data)
{
	/* caller expects data to be zero */
	unsigned long *p = data;

	*p = 0;

	return 0;
}