summaryrefslogtreecommitdiffstats
path: root/arch/sh/kernel/cpu/sh5/unwind.c
blob: 10aed41757fc8247f9e1c271623907b31192607b (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
/*
 * arch/sh/kernel/cpu/sh5/unwind.c
 *
 * Copyright (C) 2004  Paul Mundt
 * Copyright (C) 2004  Richard Curnow
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <asm/page.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
#include <asm/io.h>
#include <asm/unwinder.h>
#include <asm/stacktrace.h>

static u8 regcache[63];

/*
 * Finding the previous stack frame isn't horribly straightforward as it is
 * on some other platforms. In the sh64 case, we don't have "linked" stack
 * frames, so we need to do a bit of work to determine the previous frame,
 * and in turn, the previous r14/r18 pair.
 *
 * There are generally a few cases which determine where we can find out
 * the r14/r18 values. In the general case, this can be determined by poking
 * around the prologue of the symbol PC is in (note that we absolutely must
 * have frame pointer support as well as the kernel symbol table mapped,
 * otherwise we can't even get this far).
 *
 * In other cases, such as the interrupt/exception path, we can poke around
 * the sp/fp.
 *
 * Notably, this entire approach is somewhat error prone, and in the event
 * that the previous frame cannot be determined, that's all we can do.
 * Either way, this still leaves us with a more correct backtrace then what
 * we would be able to come up with by walking the stack (which is garbage
 * for anything beyond the first frame).
 *						-- PFM.
 */
static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
		      unsigned long *pprev_fp, unsigned long *pprev_pc,
		      struct pt_regs *regs)
{
	const char *sym;
	char namebuf[128];
	unsigned long offset;
	unsigned long prologue = 0;
	unsigned long fp_displacement = 0;
	unsigned long fp_prev = 0;
	unsigned long offset_r14 = 0, offset_r18 = 0;
	int i, found_prologue_end = 0;

	sym = kallsyms_lookup(pc, NULL, &offset, NULL, namebuf);
	if (!sym)
		return -EINVAL;

	prologue = pc - offset;
	if (!prologue)
		return -EINVAL;

	/* Validate fp, to avoid risk of dereferencing a bad pointer later.
	   Assume 128Mb since that's the amount of RAM on a Cayman.  Modify
	   when there is an SH-5 board with more. */
	if ((fp < (unsigned long) phys_to_virt(__MEMORY_START)) ||
	    (fp >= (unsigned long)(phys_to_virt(__MEMORY_START)) + 128*1024*1024) ||
	    ((fp & 7) != 0)) {
		return -EINVAL;
	}

	/*
	 * Depth to walk, depth is completely arbitrary.
	 */
	for (i = 0; i < 100; i++, prologue += sizeof(unsigned long)) {
		unsigned long op;
		u8 major, minor;
		u8 src, dest, disp;

		op = *(unsigned long *)prologue;

		major = (op >> 26) & 0x3f;
		src   = (op >> 20) & 0x3f;
		minor = (op >> 16) & 0xf;
		disp  = (op >> 10) & 0x3f;
		dest  = (op >>  4) & 0x3f;

		/*
		 * Stack frame creation happens in a number of ways.. in the
		 * general case when the stack frame is less than 511 bytes,
		 * it's generally created by an addi or addi.l:
		 *
		 *	addi/addi.l r15, -FRAME_SIZE, r15
		 *
		 * in the event that the frame size is bigger than this, it's
		 * typically created using a movi/sub pair as follows:
		 *
		 *	movi	FRAME_SIZE, rX
		 *	sub	r15, rX, r15
		 */

		switch (major) {
		case (0x00 >> 2):
			switch (minor) {
			case 0x8: /* add.l */
			case 0x9: /* add */
				/* Look for r15, r63, r14 */
				if (src == 15 && disp == 63 && dest == 14)
					found_prologue_end = 1;

				break;
			case 0xa: /* sub.l */
			case 0xb: /* sub */
				if (src != 15 || dest != 15)
					continue;

				fp_displacement -= regcache[disp];
				fp_prev = fp - fp_displacement;
				break;
			}
			break;
		case (0xa8 >> 2): /* st.l */
			if (src != 15)
				continue;

			switch (dest) {
			case 14:
				if (offset_r14 || fp_displacement == 0)
					continue;

				offset_r14 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
				offset_r14 *= sizeof(unsigned long);
				offset_r14 += fp_displacement;
				break;
			case 18:
				if (offset_r18 || fp_displacement == 0)
					continue;

				offset_r18 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
				offset_r18 *= sizeof(unsigned long);
				offset_r18 += fp_displacement;
				break;
			}

			break;
		case (0xcc >> 2): /* movi */
			if (dest >= 63) {
				printk(KERN_NOTICE "%s: Invalid dest reg %d "
				       "specified in movi handler. Failed "
				       "opcode was 0x%lx: ", __func__,
				       dest, op);

				continue;
			}

			/* Sign extend */
			regcache[dest] =
				((((s64)(u64)op >> 10) & 0xffff) << 54) >> 54;
			break;
		case (0xd0 >> 2): /* addi */
		case (0xd4 >> 2): /* addi.l */
			/* Look for r15, -FRAME_SIZE, r15 */
			if (src != 15 || dest != 15)
				continue;

			/* Sign extended frame size.. */
			fp_displacement +=
				(u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
			fp_prev = fp - fp_displacement;
			break;
		}

		if (found_prologue_end && offset_r14 && (offset_r18 || *pprev_pc) && fp_prev)
			break;
	}

	if (offset_r14 == 0 || fp_prev == 0) {
		if (!offset_r14)
			pr_debug("Unable to find r14 offset\n");
		if (!fp_prev)
			pr_debug("Unable to find previous fp\n");

		return -EINVAL;
	}

	/* For innermost leaf function, there might not be a offset_r18 */
	if (!*pprev_pc && (offset_r18 == 0))
		return -EINVAL;

	*pprev_fp = *(unsigned long *)(fp_prev + offset_r14);

	if (offset_r18)
		*pprev_pc = *(unsigned long *)(fp_prev + offset_r18);

	*pprev_pc &= ~1;

	return 0;
}

/*
 * Don't put this on the stack since we'll want to call in to
 * sh64_unwinder_dump() when we're close to underflowing the stack
 * anyway.
 */
static struct pt_regs here_regs;

extern const char syscall_ret;
extern const char ret_from_syscall;
extern const char ret_from_exception;
extern const char ret_from_irq;

static void sh64_unwind_inner(const struct stacktrace_ops *ops,
			      void *data, struct pt_regs *regs);

static inline void unwind_nested(const struct stacktrace_ops *ops, void *data,
				 unsigned long pc, unsigned long fp)
{
	if ((fp >= __MEMORY_START) &&
	    ((fp & 7) == 0))
		sh64_unwind_inner(ops, data, (struct pt_regs *)fp);
}

static void sh64_unwind_inner(const struct stacktrace_ops *ops,
			      void *data, struct pt_regs *regs)
{
	unsigned long pc, fp;
	int ofs = 0;
	int first_pass;

	pc = regs->pc & ~1;
	fp = regs->regs[14];

	first_pass = 1;
	for (;;) {
		int cond;
		unsigned long next_fp, next_pc;

		if (pc == ((unsigned long)&syscall_ret & ~1)) {
			printk("SYSCALL\n");
			unwind_nested(ops, data, pc, fp);
			return;
		}

		if (pc == ((unsigned long)&ret_from_syscall & ~1)) {
			printk("SYSCALL (PREEMPTED)\n");
			unwind_nested(ops, data, pc, fp);
			return;
		}

		/* In this case, the PC is discovered by lookup_prev_stack_frame but
		   it has 4 taken off it to look like the 'caller' */
		if (pc == ((unsigned long)&ret_from_exception & ~1)) {
			printk("EXCEPTION\n");
			unwind_nested(ops, data, pc, fp);
			return;
		}

		if (pc == ((unsigned long)&ret_from_irq & ~1)) {
			printk("IRQ\n");
			unwind_nested(ops, data, pc, fp);
			return;
		}

		cond = ((pc >= __MEMORY_START) && (fp >= __MEMORY_START) &&
			((pc & 3) == 0) && ((fp & 7) == 0));

		pc -= ofs;

		ops->address(data, pc, 1);

		if (first_pass) {
			/* If the innermost frame is a leaf function, it's
			 * possible that r18 is never saved out to the stack.
			 */
			next_pc = regs->regs[18];
		} else {
			next_pc = 0;
		}

		if (lookup_prev_stack_frame(fp, pc, &next_fp, &next_pc, regs) == 0) {
			ofs = sizeof(unsigned long);
			pc = next_pc & ~1;
			fp = next_fp;
		} else {
			printk("Unable to lookup previous stack frame\n");
			break;
		}
		first_pass = 0;
	}

	printk("\n");
}

static void sh64_unwinder_dump(struct task_struct *task,
			       struct pt_regs *regs,
			       unsigned long *sp,
			       const struct stacktrace_ops *ops,
			       void *data)
{
	if (!regs) {
		/*
		 * Fetch current regs if we have no other saved state to back
		 * trace from.
		 */
		regs = &here_regs;

		__asm__ __volatile__ ("ori r14, 0, %0" : "=r" (regs->regs[14]));
		__asm__ __volatile__ ("ori r15, 0, %0" : "=r" (regs->regs[15]));
		__asm__ __volatile__ ("ori r18, 0, %0" : "=r" (regs->regs[18]));

		__asm__ __volatile__ ("gettr tr0, %0" : "=r" (regs->tregs[0]));
		__asm__ __volatile__ ("gettr tr1, %0" : "=r" (regs->tregs[1]));
		__asm__ __volatile__ ("gettr tr2, %0" : "=r" (regs->tregs[2]));
		__asm__ __volatile__ ("gettr tr3, %0" : "=r" (regs->tregs[3]));
		__asm__ __volatile__ ("gettr tr4, %0" : "=r" (regs->tregs[4]));
		__asm__ __volatile__ ("gettr tr5, %0" : "=r" (regs->tregs[5]));
		__asm__ __volatile__ ("gettr tr6, %0" : "=r" (regs->tregs[6]));
		__asm__ __volatile__ ("gettr tr7, %0" : "=r" (regs->tregs[7]));

		__asm__ __volatile__ (
			"pta 0f, tr0\n\t"
			"blink tr0, %0\n\t"
			"0: nop"
			: "=r" (regs->pc)
		);
	}

	sh64_unwind_inner(ops, data, regs);
}

static struct unwinder sh64_unwinder = {
	.name	= "sh64-unwinder",
	.dump	= sh64_unwinder_dump,
	.rating	= 150,
};

static int __init sh64_unwinder_init(void)
{
	return unwinder_register(&sh64_unwinder);
}
early_initcall(sh64_unwinder_init);
OpenPOWER on IntegriCloud