arch/parisc/kernel/unwind.c

   1 /*
   2  * Kernel unwinding support
   3  *
   4  * (c) 2002-2004 Randolph Chung <tausq@debian.org>
   5  *
   6  * Derived partially from the IA64 implementation. The PA-RISC
   7  * Runtime Architecture Document is also a useful reference to
   8  * understand what is happening here
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/slab.h>
  15 #include <linux/kallsyms.h>
  16
  17 #include <asm/uaccess.h>
  18 #include <asm/assembly.h>
  19
  20 #include <asm/unwind.h>
  21
  22 /* #define DEBUG 1 */
  23 #ifdef DEBUG
  24 #define dbg(x...) printk(x)
  25 #else
  26 #define dbg(x...)
  27 #endif
  28
  29 extern struct unwind_table_entry __start___unwind[];
  30 extern struct unwind_table_entry __stop___unwind[];
  31
  32 static spinlock_t unwind_lock;
  33 /*
  34  * the kernel unwind block is not dynamically allocated so that
  35  * we can call unwind_init as early in the bootup process as
  36  * possible (before the slab allocator is initialized)
  37  */
  38 static struct unwind_table kernel_unwind_table __read_mostly;
  39 static LIST_HEAD(unwind_tables);
  40
  41 static inline const struct unwind_table_entry *
  42 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
  43 {
  44         const struct unwind_table_entry *e = NULL;
  45         unsigned long lo, hi, mid;
  46
  47         lo = 0;
  48         hi = table->length - 1;
  49
  50         while (lo <= hi) {
  51                 mid = (hi - lo) / 2 + lo;
  52                 e = &table->table[mid];
  53                 if (addr < e->region_start)
  54                         hi = mid - 1;
  55                 else if (addr > e->region_end)
  56                         lo = mid + 1;
  57                 else
  58                         return e;
  59         }
  60
  61         return NULL;
  62 }
  63
  64 static const struct unwind_table_entry *
  65 find_unwind_entry(unsigned long addr)
  66 {
  67         struct unwind_table *table;
  68         const struct unwind_table_entry *e = NULL;
  69
  70         if (addr >= kernel_unwind_table.start &&
  71             addr <= kernel_unwind_table.end)
  72                 e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
  73         else
  74                 list_for_each_entry(table, &unwind_tables, list) {
  75                         if (addr >= table->start &&
  76                             addr <= table->end)
  77                                 e = find_unwind_entry_in_table(table, addr);
  78                         if (e)
  79                                 break;
  80                 }
  81
  82         return e;
  83 }
  84
  85 static void
  86 unwind_table_init(struct unwind_table *table, const char *name,
  87                   unsigned long base_addr, unsigned long gp,
  88                   void *table_start, void *table_end)
  89 {
  90         struct unwind_table_entry *start = table_start;
  91         struct unwind_table_entry *end =
  92                 (struct unwind_table_entry *)table_end - 1;
  93
  94         table->name = name;
  95         table->base_addr = base_addr;
  96         table->gp = gp;
  97         table->start = base_addr + start->region_start;
  98         table->end = base_addr + end->region_end;
  99         table->table = (struct unwind_table_entry *)table_start;
 100         table->length = end - start + 1;
 101         INIT_LIST_HEAD(&table->list);
 102
 103         for (; start <= end; start++) {
 104                 if (start < end &&
 105                     start->region_end > (start+1)->region_start) {
 106                         printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
 107                 }
 108
 109                 start->region_start += base_addr;
 110                 start->region_end += base_addr;
 111         }
 112 }
 113
 114 static void
 115 unwind_table_sort(struct unwind_table_entry *start,
 116                   struct unwind_table_entry *finish)
 117 {
 118         struct unwind_table_entry el, *p, *q;
 119
 120         for (p = start + 1; p < finish; ++p) {
 121                 if (p[0].region_start < p[-1].region_start) {
 122                         el = *p;
 123                         q = p;
 124                         do {
 125                                 q[0] = q[-1];
 126                                 --q;
 127                         } while (q > start &&
 128                                  el.region_start < q[-1].region_start);
 129                         *q = el;
 130                 }
 131         }
 132 }
 133
 134 struct unwind_table *
 135 unwind_table_add(const char *name, unsigned long base_addr,
 136                  unsigned long gp,
 137                  void *start, void *end)
 138 {
 139         struct unwind_table *table;
 140         unsigned long flags;
 141         struct unwind_table_entry *s = (struct unwind_table_entry *)start;
 142         struct unwind_table_entry *e = (struct unwind_table_entry *)end;
 143
 144         unwind_table_sort(s, e);
 145
 146         table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 147         if (table == NULL)
 148                 return NULL;
 149         unwind_table_init(table, name, base_addr, gp, start, end);
 150         spin_lock_irqsave(&unwind_lock, flags);
 151         list_add_tail(&table->list, &unwind_tables);
 152         spin_unlock_irqrestore(&unwind_lock, flags);
 153
 154         return table;
 155 }
 156
 157 void unwind_table_remove(struct unwind_table *table)
 158 {
 159         unsigned long flags;
 160
 161         spin_lock_irqsave(&unwind_lock, flags);
 162         list_del(&table->list);
 163         spin_unlock_irqrestore(&unwind_lock, flags);
 164
 165         kfree(table);
 166 }
 167
 168 /* Called from setup_arch to import the kernel unwind info */
 169 static int unwind_init(void)
 170 {
 171         long start, stop;
 172         register unsigned long gp __asm__ ("r27");
 173
 174         start = (long)&__start___unwind[0];
 175         stop = (long)&__stop___unwind[0];
 176
 177         spin_lock_init(&unwind_lock);
 178
 179         printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
 180             start, stop,
 181             (stop - start) / sizeof(struct unwind_table_entry));
 182
 183         unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
 184                           gp,
 185                           &__start___unwind[0], &__stop___unwind[0]);
 186 #if 0
 187         {
 188                 int i;
 189                 for (i = 0; i < 10; i++)
 190                 {
 191                         printk("region 0x%x-0x%x\n",
 192                                 __start___unwind[i].region_start,
 193                                 __start___unwind[i].region_end);
 194                 }
 195         }
 196 #endif
 197         return 0;
 198 }
 199
 200 static void unwind_frame_regs(struct unwind_frame_info *info)
 201 {
 202         const struct unwind_table_entry *e;
 203         unsigned long npc;
 204         unsigned int insn;
 205         long frame_size = 0;
 206         int looking_for_rp, rpoffset = 0;
 207
 208         e = find_unwind_entry(info->ip);
 209         if (e == NULL) {
 210                 unsigned long sp;
 211                 extern char _stext[], _etext[];
 212
 213                 dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
 214
 215 #ifdef CONFIG_KALLSYMS
 216                 /* Handle some frequent special cases.... */
 217                 {
 218                         char symname[KSYM_NAME_LEN+1];
 219                         char *modname;
 220                         unsigned long symsize, offset;
 221
 222                         kallsyms_lookup(info->ip, &symsize, &offset,
 223                                         &modname, symname);
 224
 225                         dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
 226
 227                         if (strcmp(symname, "_switch_to_ret") == 0) {
 228                                 info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
 229                                 info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
 230                                 dbg("_switch_to_ret @ %lx - setting "
 231                                     "prev_sp=%lx prev_ip=%lx\n",
 232                                     info->ip, info->prev_sp,
 233                                     info->prev_ip);
 234                                 return;
 235                         } else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
 236                                    strcmp(symname, "syscall_exit") == 0) {
 237                                 info->prev_ip = info->prev_sp = 0;
 238                                 return;
 239                         }
 240                 }
 241 #endif
 242
 243                 /* Since we are doing the unwinding blind, we don't know if
 244                    we are adjusting the stack correctly or extracting the rp
 245                    correctly. The rp is checked to see if it belongs to the
 246                    kernel text section, if not we assume we don't have a
 247                    correct stack frame and we continue to unwind the stack.
 248                    This is not quite correct, and will fail for loadable
 249                    modules. */
 250                 sp = info->sp & ~63;
 251                 do {
 252                         unsigned long tmp;
 253
 254                         info->prev_sp = sp - 64;
 255                         info->prev_ip = 0;
 256                         if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
 257                                 break;
 258                         info->prev_ip = tmp;
 259                         sp = info->prev_sp;
 260                 } while (info->prev_ip < (unsigned long)_stext ||
 261                          info->prev_ip > (unsigned long)_etext);
 262
 263                 info->rp = 0;
 264
 265                 dbg("analyzing func @ %lx with no unwind info, setting "
 266                     "prev_sp=%lx prev_ip=%lx\n", info->ip,
 267                     info->prev_sp, info->prev_ip);
 268         } else {
 269                 dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
 270                     "Save_RP = %d, Millicode = %d size = %u\n",
 271                     e->region_start, e->region_end, e->Save_SP, e->Save_RP,
 272                     e->Millicode, e->Total_frame_size);
 273
 274                 looking_for_rp = e->Save_RP;
 275
 276                 for (npc = e->region_start;
 277                      (frame_size < (e->Total_frame_size << 3) ||
 278                       looking_for_rp) &&
 279                      npc < info->ip;
 280                      npc += 4) {
 281
 282                         insn = *(unsigned int *)npc;
 283
 284                         if ((insn & 0xffffc000) == 0x37de0000 ||
 285                             (insn & 0xffe00000) == 0x6fc00000) {
 286                                 /* ldo X(sp), sp, or stwm X,D(sp) */
 287                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 288                                         ((insn & 0x3fff) >> 1);
 289                                 dbg("analyzing func @ %lx, insn=%08x @ "
 290                                     "%lx, frame_size = %ld\n", info->ip,
 291                                     insn, npc, frame_size);
 292                         } else if ((insn & 0xffe00008) == 0x73c00008) {
 293                                 /* std,ma X,D(sp) */
 294                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 295                                         (((insn >> 4) & 0x3ff) << 3);
 296                                 dbg("analyzing func @ %lx, insn=%08x @ "
 297                                     "%lx, frame_size = %ld\n", info->ip,
 298                                     insn, npc, frame_size);
 299                         } else if (insn == 0x6bc23fd9) {
 300                                 /* stw rp,-20(sp) */
 301                                 rpoffset = 20;
 302                                 looking_for_rp = 0;
 303                                 dbg("analyzing func @ %lx, insn=stw rp,"
 304                                     "-20(sp) @ %lx\n", info->ip, npc);
 305                         } else if (insn == 0x0fc212c1) {
 306                                 /* std rp,-16(sr0,sp) */
 307                                 rpoffset = 16;
 308                                 looking_for_rp = 0;
 309                                 dbg("analyzing func @ %lx, insn=std rp,"
 310                                     "-16(sp) @ %lx\n", info->ip, npc);
 311                         }
 312                 }
 313
 314                 info->prev_sp = info->sp - frame_size;
 315                 if (e->Millicode)
 316                         info->rp = info->r31;
 317                 else if (rpoffset)
 318                         info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 319                 info->prev_ip = info->rp;
 320                 info->rp = 0;
 321
 322                 dbg("analyzing func @ %lx, setting prev_sp=%lx "
 323                     "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
 324                     info->prev_ip, npc);
 325         }
 326 }
 327
 328 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 329                        struct pt_regs *regs)
 330 {
 331         memset(info, 0, sizeof(struct unwind_frame_info));
 332         info->t = t;
 333         info->sp = regs->gr[30];
 334         info->ip = regs->iaoq[0];
 335         info->rp = regs->gr[2];
 336         info->r31 = regs->gr[31];
 337
 338         dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
 339             t ? (int)t->pid : -1, info->sp, info->ip);
 340 }
 341
 342 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 343 {
 344         struct pt_regs *r = &t->thread.regs;
 345         struct pt_regs *r2;
 346
 347         r2 = (struct pt_regs *)kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
 348         if (!r2)
 349                 return;
 350         *r2 = *r;
 351         r2->gr[30] = r->ksp;
 352         r2->iaoq[0] = r->kpc;
 353         unwind_frame_init(info, t, r2);
 354         kfree(r2);
 355 }
 356
 357 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 358 {
 359         unwind_frame_init(info, current, regs);
 360 }
 361
 362 int unwind_once(struct unwind_frame_info *next_frame)
 363 {
 364         unwind_frame_regs(next_frame);
 365
 366         if (next_frame->prev_sp == 0 ||
 367             next_frame->prev_ip == 0)
 368                 return -1;
 369
 370         next_frame->sp = next_frame->prev_sp;
 371         next_frame->ip = next_frame->prev_ip;
 372         next_frame->prev_sp = 0;
 373         next_frame->prev_ip = 0;
 374
 375         dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
 376             next_frame->t ? (int)next_frame->t->pid : -1,
 377             next_frame->sp, next_frame->ip);
 378
 379         return 0;
 380 }
 381
 382 int unwind_to_user(struct unwind_frame_info *info)
 383 {
 384         int ret;
 385
 386         do {
 387                 ret = unwind_once(info);
 388         } while (!ret && !(info->ip & 3));
 389
 390         return ret;
 391 }
 392
 393 module_init(unwind_init);