1 /*
2 * arch/arm/kernel/unwind.c
3 *
4 * Copyright (C) 2008 ARM Limited
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 *
20 * Stack unwinding support for ARM
21 *
22 * An ARM EABI version of gcc is required to generate the unwind
23 * tables. For information about the structure of the unwind tables,
24 * see "Exception Handling ABI for the ARM Architecture" at:
25 *
26 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
27 */
28
29 #include <linux/kernel.h>
30 #include <linux/init.h>
31 #include <linux/module.h>
32 #include <linux/sched.h>
33 #include <linux/slab.h>
34 #include <linux/spinlock.h>
35 #include <linux/list.h>
36
37 #include <asm/stacktrace.h>
38 #include <asm/traps.h>
39 #include <asm/unwind.h>
40
41 /* Dummy functions to avoid linker complaints */
42 void __aeabi_unwind_cpp_pr0(void)
43 {
44 };
45 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
46
47 void __aeabi_unwind_cpp_pr1(void)
48 {
49 };
50 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
51
52 void __aeabi_unwind_cpp_pr2(void)
53 {
54 };
55 EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
56
57 struct unwind_ctrl_block {
58 unsigned long vrs[16]; /* virtual register set */
59 unsigned long *insn; /* pointer to the current instructions word */
60 int entries; /* number of entries left to interpret */
61 int byte; /* current byte number in the instructions word */
62 };
63
64 enum regs {
65 FP = 11,
66 SP = 13,
67 LR = 14,
68 PC = 15
69 };
70
71 extern struct unwind_idx __start_unwind_idx[];
72 extern struct unwind_idx __stop_unwind_idx[];
73
74 static DEFINE_SPINLOCK(unwind_lock);
75 static LIST_HEAD(unwind_tables);
76
77 /* Convert a prel31 symbol to an absolute address */
78 #define prel31_to_addr(ptr) \
79 ({ \
80 /* sign-extend to 32 bits */ \
81 long offset = (((long)*(ptr)) << 1) >> 1; \
82 (unsigned long)(ptr) + offset; \
83 })
84
85 /*
86 * Binary search in the unwind index. The entries entries are
87 * guaranteed to be sorted in ascending order by the linker.
88 */
89 static struct unwind_idx *search_index(unsigned long addr,
90 struct unwind_idx *first,
91 struct unwind_idx *last)
92 {
93 pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
94
95 if (addr < first->addr) {
96 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
97 return NULL;
98 } else if (addr >= last->addr)
99 return last;
100
101 while (first < last - 1) {
102 struct unwind_idx *mid = first + ((last - first + 1) >> 1);
103
104 if (addr < mid->addr)
105 last = mid;
106 else
107 first = mid;
108 }
109
110 return first;
111 }
112
113 static struct unwind_idx *unwind_find_idx(unsigned long addr)
114 {
115 struct unwind_idx *idx = NULL;
116 unsigned long flags;
117
118 pr_debug("%s(%08lx)\n", __func__, addr);
119
120 if (core_kernel_text(addr))
121 /* main unwind table */
122 idx = search_index(addr, __start_unwind_idx,
123 __stop_unwind_idx - 1);
124 else {
125 /* module unwind tables */
126 struct unwind_table *table;
127
128 spin_lock_irqsave(&unwind_lock, flags);
129 list_for_each_entry(table, &unwind_tables, list) {
130 if (addr >= table->begin_addr &&
131 addr < table->end_addr) {
132 idx = search_index(addr, table->start,
133 table->stop - 1);
134 break;
135 }
136 }
137 spin_unlock_irqrestore(&unwind_lock, flags);
138 }
139
140 pr_debug("%s: idx = %p\n", __func__, idx);
141 return idx;
142 }
143
144 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
145 {
146 unsigned long ret;
147
148 if (ctrl->entries <= 0) {
149 pr_warning("unwind: Corrupt unwind table\n");
150 return 0;
151 }
152
153 ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
154
155 if (ctrl->byte == 0) {
156 ctrl->insn++;
157 ctrl->entries--;
158 ctrl->byte = 3;
159 } else
160 ctrl->byte--;
161
162 return ret;
163 }
164
165 /*
166 * Execute the current unwind instruction.
167 */
168 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
169 {
170 unsigned long insn = unwind_get_byte(ctrl);
171
172 pr_debug("%s: insn = %08lx\n", __func__, insn);
173
174 if ((insn & 0xc0) == 0x00)
175 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
176 else if ((insn & 0xc0) == 0x40)
177 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
178 else if ((insn & 0xf0) == 0x80) {
179 unsigned long mask;
180 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
181 int load_sp, reg = 4;
182
183 insn = (insn << 8) | unwind_get_byte(ctrl);
184 mask = insn & 0x0fff;
185 if (mask == 0) {
186 pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
187 insn);
188 return -URC_FAILURE;
189 }
190
191 /* pop R4-R15 according to mask */
192 load_sp = mask & (1 << (13 - 4));
193 while (mask) {
194 if (mask & 1)
195 ctrl->vrs[reg] = *vsp++;
196 mask >>= 1;
197 reg++;
198 }
199 if (!load_sp)
200 ctrl->vrs[SP] = (unsigned long)vsp;
201 } else if ((insn & 0xf0) == 0x90 &&
202 (insn & 0x0d) != 0x0d)
203 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
204 else if ((insn & 0xf0) == 0xa0) {
205 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
206 int reg;
207
208 /* pop R4-R[4+bbb] */
209 for (reg = 4; reg <= 4 + (insn & 7); reg++)
210 ctrl->vrs[reg] = *vsp++;
211 if (insn & 0x80)
212 ctrl->vrs[14] = *vsp++;
213 ctrl->vrs[SP] = (unsigned long)vsp;
214 } else if (insn == 0xb0) {
215 if (ctrl->vrs[PC] == 0)
216 ctrl->vrs[PC] = ctrl->vrs[LR];
217 /* no further processing */
218 ctrl->entries = 0;
219 } else if (insn == 0xb1) {
220 unsigned long mask = unwind_get_byte(ctrl);
221 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
222 int reg = 0;
223
224 if (mask == 0 || mask & 0xf0) {
225 pr_warning("unwind: Spare encoding %04lx\n",
226 (insn << 8) | mask);
227 return -URC_FAILURE;
228 }
229
230 /* pop R0-R3 according to mask */
231 while (mask) {
232 if (mask & 1)
233 ctrl->vrs[reg] = *vsp++;
234 mask >>= 1;
235 reg++;
236 }
237 ctrl->vrs[SP] = (unsigned long)vsp;
238 } else if (insn == 0xb2) {
239 unsigned long uleb128 = unwind_get_byte(ctrl);
240
241 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
242 } else {
243 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
244 return -URC_FAILURE;
245 }
246
247 pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
248 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
249
250 return URC_OK;
251 }
252
253 /*
254 * Unwind a single frame starting with *sp for the symbol at *pc. It
255 * updates the *pc and *sp with the new values.
256 */
257 int unwind_frame(struct stackframe *frame)
258 {
259 unsigned long high, low;
260 struct unwind_idx *idx;
261 struct unwind_ctrl_block ctrl;
262
263 /* only go to a higher address on the stack */
264 low = frame->sp;
265 high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
266
267 pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
268 frame->pc, frame->lr, frame->sp);
269
270 if (!kernel_text_address(frame->pc))
271 return -URC_FAILURE;
272
273 idx = unwind_find_idx(frame->pc);
274 if (!idx) {
275 pr_warning("unwind: Index not found %08lx\n", frame->pc);
276 return -URC_FAILURE;
277 }
278
279 ctrl.vrs[FP] = frame->fp;
280 ctrl.vrs[SP] = frame->sp;
281 ctrl.vrs[LR] = frame->lr;
282 ctrl.vrs[PC] = 0;
283
284 if (idx->insn == 1)
285 /* can't unwind */
286 return -URC_FAILURE;
287 else if ((idx->insn & 0x80000000) == 0)
288 /* prel31 to the unwind table */
289 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
290 else if ((idx->insn & 0xff000000) == 0x80000000)
291 /* only personality routine 0 supported in the index */
292 ctrl.insn = &idx->insn;
293 else {
294 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
295 idx->insn, idx);
296 return -URC_FAILURE;
297 }
298
299 /* check the personality routine */
300 if ((*ctrl.insn & 0xff000000) == 0x80000000) {
301 ctrl.byte = 2;
302 ctrl.entries = 1;
303 } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
304 ctrl.byte = 1;
305 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
306 } else {
307 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
308 *ctrl.insn, ctrl.insn);
309 return -URC_FAILURE;
310 }
311
312 while (ctrl.entries > 0) {
313 int urc = unwind_exec_insn(&ctrl);
314 if (urc < 0)
315 return urc;
316 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
317 return -URC_FAILURE;
318 }
319
320 if (ctrl.vrs[PC] == 0)
321 ctrl.vrs[PC] = ctrl.vrs[LR];
322
323 /* check for infinite loop */
324 if (frame->pc == ctrl.vrs[PC])
325 return -URC_FAILURE;
326
327 frame->fp = ctrl.vrs[FP];
328 frame->sp = ctrl.vrs[SP];
329 frame->lr = ctrl.vrs[LR];
330 frame->pc = ctrl.vrs[PC];
331
332 return URC_OK;
333 }
334
335 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
336 {
337 struct stackframe frame;
338 register unsigned long current_sp asm ("sp");
339
340 pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
341
342 if (!tsk)
343 tsk = current;
344
345 if (regs) {
346 frame.fp = regs->ARM_fp;
347 frame.sp = regs->ARM_sp;
348 frame.lr = regs->ARM_lr;
349 frame.pc = regs->ARM_pc;
350 } else if (tsk == current) {
351 frame.fp = (unsigned long)__builtin_frame_address(0);
352 frame.sp = current_sp;
353 frame.lr = (unsigned long)__builtin_return_address(0);
354 frame.pc = (unsigned long)unwind_backtrace;
355 } else {
356 /* task blocked in __switch_to */
357 frame.fp = thread_saved_fp(tsk);
358 frame.sp = thread_saved_sp(tsk);
359 /*
360 * The function calling __switch_to cannot be a leaf function
361 * so LR is recovered from the stack.
362 */
363 frame.lr = 0;
364 frame.pc = thread_saved_pc(tsk);
365 }
366
367 while (1) {
368 int urc;
369 unsigned long where = frame.pc;
370
371 urc = unwind_frame(&frame);
372 if (urc < 0)
373 break;
374 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
375 }
376 }
377
378 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
379 unsigned long text_addr,
380 unsigned long text_size)
381 {
382 unsigned long flags;
383 struct unwind_idx *idx;
384 struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
385
386 pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
387 text_addr, text_size);
388
389 if (!tab)
390 return tab;
391
392 tab->start = (struct unwind_idx *)start;
393 tab->stop = (struct unwind_idx *)(start + size);
394 tab->begin_addr = text_addr;
395 tab->end_addr = text_addr + text_size;
396
397 /* Convert the symbol addresses to absolute values */
398 for (idx = tab->start; idx < tab->stop; idx++)
399 idx->addr = prel31_to_addr(&idx->addr);
400
401 spin_lock_irqsave(&unwind_lock, flags);
402 list_add_tail(&tab->list, &unwind_tables);
403 spin_unlock_irqrestore(&unwind_lock, flags);
404
405 return tab;
406 }
407
408 void unwind_table_del(struct unwind_table *tab)
409 {
410 unsigned long flags;
411
412 if (!tab)
413 return;
414
415 spin_lock_irqsave(&unwind_lock, flags);
416 list_del(&tab->list);
417 spin_unlock_irqrestore(&unwind_lock, flags);
418
419 kfree(tab);
420 }
421
422 int __init unwind_init(void)
423 {
424 struct unwind_idx *idx;
425
426 /* Convert the symbol addresses to absolute values */
427 for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
428 idx->addr = prel31_to_addr(&idx->addr);
429
430 pr_debug("unwind: ARM stack unwinding initialised\n");
431
432 return 0;
433 }
434
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