Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm
[linux-2.6.git] / arch / arm / kernel / unwind.c
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 #ifdef CONFIG_THUMB2_KERNEL
66         FP = 7,
67 #else
68         FP = 11,
69 #endif
70         SP = 13,
71         LR = 14,
72         PC = 15
73 };
74
75 extern struct unwind_idx __start_unwind_idx[];
76 extern struct unwind_idx __stop_unwind_idx[];
77
78 static DEFINE_SPINLOCK(unwind_lock);
79 static LIST_HEAD(unwind_tables);
80
81 /* Convert a prel31 symbol to an absolute address */
82 #define prel31_to_addr(ptr)                             \
83 ({                                                      \
84         /* sign-extend to 32 bits */                    \
85         long offset = (((long)*(ptr)) << 1) >> 1;       \
86         (unsigned long)(ptr) + offset;                  \
87 })
88
89 /*
90  * Binary search in the unwind index. The entries entries are
91  * guaranteed to be sorted in ascending order by the linker.
92  */
93 static struct unwind_idx *search_index(unsigned long addr,
94                                        struct unwind_idx *first,
95                                        struct unwind_idx *last)
96 {
97         pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
98
99         if (addr < first->addr) {
100                 pr_warning("unwind: Unknown symbol address %08lx\n", addr);
101                 return NULL;
102         } else if (addr >= last->addr)
103                 return last;
104
105         while (first < last - 1) {
106                 struct unwind_idx *mid = first + ((last - first + 1) >> 1);
107
108                 if (addr < mid->addr)
109                         last = mid;
110                 else
111                         first = mid;
112         }
113
114         return first;
115 }
116
117 static struct unwind_idx *unwind_find_idx(unsigned long addr)
118 {
119         struct unwind_idx *idx = NULL;
120         unsigned long flags;
121
122         pr_debug("%s(%08lx)\n", __func__, addr);
123
124         if (core_kernel_text(addr))
125                 /* main unwind table */
126                 idx = search_index(addr, __start_unwind_idx,
127                                    __stop_unwind_idx - 1);
128         else {
129                 /* module unwind tables */
130                 struct unwind_table *table;
131
132                 spin_lock_irqsave(&unwind_lock, flags);
133                 list_for_each_entry(table, &unwind_tables, list) {
134                         if (addr >= table->begin_addr &&
135                             addr < table->end_addr) {
136                                 idx = search_index(addr, table->start,
137                                                    table->stop - 1);
138                                 break;
139                         }
140                 }
141                 spin_unlock_irqrestore(&unwind_lock, flags);
142         }
143
144         pr_debug("%s: idx = %p\n", __func__, idx);
145         return idx;
146 }
147
148 static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
149 {
150         unsigned long ret;
151
152         if (ctrl->entries <= 0) {
153                 pr_warning("unwind: Corrupt unwind table\n");
154                 return 0;
155         }
156
157         ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
158
159         if (ctrl->byte == 0) {
160                 ctrl->insn++;
161                 ctrl->entries--;
162                 ctrl->byte = 3;
163         } else
164                 ctrl->byte--;
165
166         return ret;
167 }
168
169 /*
170  * Execute the current unwind instruction.
171  */
172 static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
173 {
174         unsigned long insn = unwind_get_byte(ctrl);
175
176         pr_debug("%s: insn = %08lx\n", __func__, insn);
177
178         if ((insn & 0xc0) == 0x00)
179                 ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
180         else if ((insn & 0xc0) == 0x40)
181                 ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
182         else if ((insn & 0xf0) == 0x80) {
183                 unsigned long mask;
184                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
185                 int load_sp, reg = 4;
186
187                 insn = (insn << 8) | unwind_get_byte(ctrl);
188                 mask = insn & 0x0fff;
189                 if (mask == 0) {
190                         pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
191                                    insn);
192                         return -URC_FAILURE;
193                 }
194
195                 /* pop R4-R15 according to mask */
196                 load_sp = mask & (1 << (13 - 4));
197                 while (mask) {
198                         if (mask & 1)
199                                 ctrl->vrs[reg] = *vsp++;
200                         mask >>= 1;
201                         reg++;
202                 }
203                 if (!load_sp)
204                         ctrl->vrs[SP] = (unsigned long)vsp;
205         } else if ((insn & 0xf0) == 0x90 &&
206                    (insn & 0x0d) != 0x0d)
207                 ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
208         else if ((insn & 0xf0) == 0xa0) {
209                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
210                 int reg;
211
212                 /* pop R4-R[4+bbb] */
213                 for (reg = 4; reg <= 4 + (insn & 7); reg++)
214                         ctrl->vrs[reg] = *vsp++;
215                 if (insn & 0x80)
216                         ctrl->vrs[14] = *vsp++;
217                 ctrl->vrs[SP] = (unsigned long)vsp;
218         } else if (insn == 0xb0) {
219                 if (ctrl->vrs[PC] == 0)
220                         ctrl->vrs[PC] = ctrl->vrs[LR];
221                 /* no further processing */
222                 ctrl->entries = 0;
223         } else if (insn == 0xb1) {
224                 unsigned long mask = unwind_get_byte(ctrl);
225                 unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
226                 int reg = 0;
227
228                 if (mask == 0 || mask & 0xf0) {
229                         pr_warning("unwind: Spare encoding %04lx\n",
230                                (insn << 8) | mask);
231                         return -URC_FAILURE;
232                 }
233
234                 /* pop R0-R3 according to mask */
235                 while (mask) {
236                         if (mask & 1)
237                                 ctrl->vrs[reg] = *vsp++;
238                         mask >>= 1;
239                         reg++;
240                 }
241                 ctrl->vrs[SP] = (unsigned long)vsp;
242         } else if (insn == 0xb2) {
243                 unsigned long uleb128 = unwind_get_byte(ctrl);
244
245                 ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
246         } else {
247                 pr_warning("unwind: Unhandled instruction %02lx\n", insn);
248                 return -URC_FAILURE;
249         }
250
251         pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
252                  ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
253
254         return URC_OK;
255 }
256
257 /*
258  * Unwind a single frame starting with *sp for the symbol at *pc. It
259  * updates the *pc and *sp with the new values.
260  */
261 int unwind_frame(struct stackframe *frame)
262 {
263         unsigned long high, low;
264         struct unwind_idx *idx;
265         struct unwind_ctrl_block ctrl;
266
267         /* only go to a higher address on the stack */
268         low = frame->sp;
269         high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
270
271         pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
272                  frame->pc, frame->lr, frame->sp);
273
274         if (!kernel_text_address(frame->pc))
275                 return -URC_FAILURE;
276
277         idx = unwind_find_idx(frame->pc);
278         if (!idx) {
279                 pr_warning("unwind: Index not found %08lx\n", frame->pc);
280                 return -URC_FAILURE;
281         }
282
283         ctrl.vrs[FP] = frame->fp;
284         ctrl.vrs[SP] = frame->sp;
285         ctrl.vrs[LR] = frame->lr;
286         ctrl.vrs[PC] = 0;
287
288         if (idx->insn == 1)
289                 /* can't unwind */
290                 return -URC_FAILURE;
291         else if ((idx->insn & 0x80000000) == 0)
292                 /* prel31 to the unwind table */
293                 ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
294         else if ((idx->insn & 0xff000000) == 0x80000000)
295                 /* only personality routine 0 supported in the index */
296                 ctrl.insn = &idx->insn;
297         else {
298                 pr_warning("unwind: Unsupported personality routine %08lx in the index at %p\n",
299                            idx->insn, idx);
300                 return -URC_FAILURE;
301         }
302
303         /* check the personality routine */
304         if ((*ctrl.insn & 0xff000000) == 0x80000000) {
305                 ctrl.byte = 2;
306                 ctrl.entries = 1;
307         } else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
308                 ctrl.byte = 1;
309                 ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
310         } else {
311                 pr_warning("unwind: Unsupported personality routine %08lx at %p\n",
312                            *ctrl.insn, ctrl.insn);
313                 return -URC_FAILURE;
314         }
315
316         while (ctrl.entries > 0) {
317                 int urc = unwind_exec_insn(&ctrl);
318                 if (urc < 0)
319                         return urc;
320                 if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= high)
321                         return -URC_FAILURE;
322         }
323
324         if (ctrl.vrs[PC] == 0)
325                 ctrl.vrs[PC] = ctrl.vrs[LR];
326
327         /* check for infinite loop */
328         if (frame->pc == ctrl.vrs[PC])
329                 return -URC_FAILURE;
330
331         frame->fp = ctrl.vrs[FP];
332         frame->sp = ctrl.vrs[SP];
333         frame->lr = ctrl.vrs[LR];
334         frame->pc = ctrl.vrs[PC];
335
336         return URC_OK;
337 }
338
339 void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
340 {
341         struct stackframe frame;
342         register unsigned long current_sp asm ("sp");
343
344         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
345
346         if (!tsk)
347                 tsk = current;
348
349         if (regs) {
350                 frame.fp = regs->ARM_fp;
351                 frame.sp = regs->ARM_sp;
352                 frame.lr = regs->ARM_lr;
353                 frame.pc = regs->ARM_pc;
354         } else if (tsk == current) {
355                 frame.fp = (unsigned long)__builtin_frame_address(0);
356                 frame.sp = current_sp;
357                 frame.lr = (unsigned long)__builtin_return_address(0);
358                 frame.pc = (unsigned long)unwind_backtrace;
359         } else {
360                 /* task blocked in __switch_to */
361                 frame.fp = thread_saved_fp(tsk);
362                 frame.sp = thread_saved_sp(tsk);
363                 /*
364                  * The function calling __switch_to cannot be a leaf function
365                  * so LR is recovered from the stack.
366                  */
367                 frame.lr = 0;
368                 frame.pc = thread_saved_pc(tsk);
369         }
370
371         while (1) {
372                 int urc;
373                 unsigned long where = frame.pc;
374
375                 urc = unwind_frame(&frame);
376                 if (urc < 0)
377                         break;
378                 dump_backtrace_entry(where, frame.pc, frame.sp - 4);
379         }
380 }
381
382 struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
383                                       unsigned long text_addr,
384                                       unsigned long text_size)
385 {
386         unsigned long flags;
387         struct unwind_idx *idx;
388         struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
389
390         pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
391                  text_addr, text_size);
392
393         if (!tab)
394                 return tab;
395
396         tab->start = (struct unwind_idx *)start;
397         tab->stop = (struct unwind_idx *)(start + size);
398         tab->begin_addr = text_addr;
399         tab->end_addr = text_addr + text_size;
400
401         /* Convert the symbol addresses to absolute values */
402         for (idx = tab->start; idx < tab->stop; idx++)
403                 idx->addr = prel31_to_addr(&idx->addr);
404
405         spin_lock_irqsave(&unwind_lock, flags);
406         list_add_tail(&tab->list, &unwind_tables);
407         spin_unlock_irqrestore(&unwind_lock, flags);
408
409         return tab;
410 }
411
412 void unwind_table_del(struct unwind_table *tab)
413 {
414         unsigned long flags;
415
416         if (!tab)
417                 return;
418
419         spin_lock_irqsave(&unwind_lock, flags);
420         list_del(&tab->list);
421         spin_unlock_irqrestore(&unwind_lock, flags);
422
423         kfree(tab);
424 }
425
426 int __init unwind_init(void)
427 {
428         struct unwind_idx *idx;
429
430         /* Convert the symbol addresses to absolute values */
431         for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
432                 idx->addr = prel31_to_addr(&idx->addr);
433
434         pr_debug("unwind: ARM stack unwinding initialised\n");
435
436         return 0;
437 }