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/kernel.h>
  12 #include <linux/init.h>
  13 #include <linux/sched.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 #define KERNEL_START (KERNEL_BINARY_TEXT_START - 0x1000)
  30
  31 extern struct unwind_table_entry __start___unwind[];
  32 extern struct unwind_table_entry __stop___unwind[];
  33
  34 static spinlock_t unwind_lock;
  35 /*
  36  * the kernel unwind block is not dynamically allocated so that
  37  * we can call unwind_init as early in the bootup process as
  38  * possible (before the slab allocator is initialized)
  39  */
  40 static struct unwind_table kernel_unwind_table __read_mostly;
  41 static LIST_HEAD(unwind_tables);
  42
  43 static inline const struct unwind_table_entry *
  44 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
  45 {
  46         const struct unwind_table_entry *e = NULL;
  47         unsigned long lo, hi, mid;
  48
  49         lo = 0;
  50         hi = table->length - 1;
  51
  52         while (lo <= hi) {
  53                 mid = (hi - lo) / 2 + lo;
  54                 e = &table->table[mid];
  55                 if (addr < e->region_start)
  56                         hi = mid - 1;
  57                 else if (addr > e->region_end)
  58                         lo = mid + 1;
  59                 else
  60                         return e;
  61         }
  62
  63         return NULL;
  64 }
  65
  66 static const struct unwind_table_entry *
  67 find_unwind_entry(unsigned long addr)
  68 {
  69         struct unwind_table *table;
  70         const struct unwind_table_entry *e = NULL;
  71
  72         if (addr >= kernel_unwind_table.start &&
  73             addr <= kernel_unwind_table.end)
  74                 e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
  75         else
  76                 list_for_each_entry(table, &unwind_tables, list) {
  77                         if (addr >= table->start &&
  78                             addr <= table->end)
  79                                 e = find_unwind_entry_in_table(table, addr);
  80                         if (e)
  81                                 break;
  82                 }
  83
  84         return e;
  85 }
  86
  87 static void
  88 unwind_table_init(struct unwind_table *table, const char *name,
  89                   unsigned long base_addr, unsigned long gp,
  90                   void *table_start, void *table_end)
  91 {
  92         struct unwind_table_entry *start = table_start;
  93         struct unwind_table_entry *end =
  94                 (struct unwind_table_entry *)table_end - 1;
  95
  96         table->name = name;
  97         table->base_addr = base_addr;
  98         table->gp = gp;
  99         table->start = base_addr + start->region_start;
 100         table->end = base_addr + end->region_end;
 101         table->table = (struct unwind_table_entry *)table_start;
 102         table->length = end - start + 1;
 103         INIT_LIST_HEAD(&table->list);
 104
 105         for (; start <= end; start++) {
 106                 if (start < end &&
 107                     start->region_end > (start+1)->region_start) {
 108                         printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
 109                 }
 110
 111                 start->region_start += base_addr;
 112                 start->region_end += base_addr;
 113         }
 114 }
 115
 116 static void
 117 unwind_table_sort(struct unwind_table_entry *start,
 118                   struct unwind_table_entry *finish)
 119 {
 120         struct unwind_table_entry el, *p, *q;
 121
 122         for (p = start + 1; p < finish; ++p) {
 123                 if (p[0].region_start < p[-1].region_start) {
 124                         el = *p;
 125                         q = p;
 126                         do {
 127                                 q[0] = q[-1];
 128                                 --q;
 129                         } while (q > start &&
 130                                  el.region_start < q[-1].region_start);
 131                         *q = el;
 132                 }
 133         }
 134 }
 135
 136 struct unwind_table *
 137 unwind_table_add(const char *name, unsigned long base_addr,
 138                  unsigned long gp,
 139                  void *start, void *end)
 140 {
 141         struct unwind_table *table;
 142         unsigned long flags;
 143         struct unwind_table_entry *s = (struct unwind_table_entry *)start;
 144         struct unwind_table_entry *e = (struct unwind_table_entry *)end;
 145
 146         unwind_table_sort(s, e);
 147
 148         table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 149         if (table == NULL)
 150                 return NULL;
 151         unwind_table_init(table, name, base_addr, gp, start, end);
 152         spin_lock_irqsave(&unwind_lock, flags);
 153         list_add_tail(&table->list, &unwind_tables);
 154         spin_unlock_irqrestore(&unwind_lock, flags);
 155
 156         return table;
 157 }
 158
 159 void unwind_table_remove(struct unwind_table *table)
 160 {
 161         unsigned long flags;
 162
 163         spin_lock_irqsave(&unwind_lock, flags);
 164         list_del(&table->list);
 165         spin_unlock_irqrestore(&unwind_lock, flags);
 166
 167         kfree(table);
 168 }
 169
 170 /* Called from setup_arch to import the kernel unwind info */
 171 static int unwind_init(void)
 172 {
 173         long start, stop;
 174         register unsigned long gp __asm__ ("r27");
 175
 176         start = (long)&__start___unwind[0];
 177         stop = (long)&__stop___unwind[0];
 178
 179         spin_lock_init(&unwind_lock);
 180
 181         printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
 182             start, stop,
 183             (stop - start) / sizeof(struct unwind_table_entry));
 184
 185         unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
 186                           gp,
 187                           &__start___unwind[0], &__stop___unwind[0]);
 188 #if 0
 189         {
 190                 int i;
 191                 for (i = 0; i < 10; i++)
 192                 {
 193                         printk("region 0x%x-0x%x\n",
 194                                 __start___unwind[i].region_start,
 195                                 __start___unwind[i].region_end);
 196                 }
 197         }
 198 #endif
 199         return 0;
 200 }
 201
 202 static void unwind_frame_regs(struct unwind_frame_info *info)
 203 {
 204         const struct unwind_table_entry *e;
 205         unsigned long npc;
 206         unsigned int insn;
 207         long frame_size = 0;
 208         int looking_for_rp, rpoffset = 0;
 209
 210         e = find_unwind_entry(info->ip);
 211         if (e == NULL) {
 212                 unsigned long sp;
 213                 extern char _stext[], _etext[];
 214
 215                 dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
 216
 217 #ifdef CONFIG_KALLSYMS
 218                 /* Handle some frequent special cases.... */
 219                 {
 220                         char symname[KSYM_NAME_LEN+1];
 221                         char *modname;
 222
 223                         kallsyms_lookup(info->ip, NULL, NULL, &modname,
 224                                 symname);
 225
 226                         dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
 227
 228                         if (strcmp(symname, "_switch_to_ret") == 0) {
 229                                 info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
 230                                 info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
 231                                 dbg("_switch_to_ret @ %lx - setting "
 232                                     "prev_sp=%lx prev_ip=%lx\n",
 233                                     info->ip, info->prev_sp,
 234                                     info->prev_ip);
 235                                 return;
 236                         } else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
 237                                    strcmp(symname, "syscall_exit") == 0) {
 238                                 info->prev_ip = info->prev_sp = 0;
 239                                 return;
 240                         }
 241                 }
 242 #endif
 243
 244                 /* Since we are doing the unwinding blind, we don't know if
 245                    we are adjusting the stack correctly or extracting the rp
 246                    correctly. The rp is checked to see if it belongs to the
 247                    kernel text section, if not we assume we don't have a
 248                    correct stack frame and we continue to unwind the stack.
 249                    This is not quite correct, and will fail for loadable
 250                    modules. */
 251                 sp = info->sp & ~63;
 252                 do {
 253                         unsigned long tmp;
 254
 255                         info->prev_sp = sp - 64;
 256                         info->prev_ip = 0;
 257                         if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
 258                                 break;
 259                         info->prev_ip = tmp;
 260                         sp = info->prev_sp;
 261                 } while (info->prev_ip < (unsigned long)_stext ||
 262                          info->prev_ip > (unsigned long)_etext);
 263
 264                 info->rp = 0;
 265
 266                 dbg("analyzing func @ %lx with no unwind info, setting "
 267                     "prev_sp=%lx prev_ip=%lx\n", info->ip,
 268                     info->prev_sp, info->prev_ip);
 269         } else {
 270                 dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
 271                     "Save_RP = %d, Millicode = %d size = %u\n",
 272                     e->region_start, e->region_end, e->Save_SP, e->Save_RP,
 273                     e->Millicode, e->Total_frame_size);
 274
 275                 looking_for_rp = e->Save_RP;
 276
 277                 for (npc = e->region_start;
 278                      (frame_size < (e->Total_frame_size << 3) ||
 279                       looking_for_rp) &&
 280                      npc < info->ip;
 281                      npc += 4) {
 282
 283                         insn = *(unsigned int *)npc;
 284
 285                         if ((insn & 0xffffc000) == 0x37de0000 ||
 286                             (insn & 0xffe00000) == 0x6fc00000) {
 287                                 /* ldo X(sp), sp, or stwm X,D(sp) */
 288                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 289                                         ((insn & 0x3fff) >> 1);
 290                                 dbg("analyzing func @ %lx, insn=%08x @ "
 291                                     "%lx, frame_size = %ld\n", info->ip,
 292                                     insn, npc, frame_size);
 293                         } else if ((insn & 0xffe00008) == 0x73c00008) {
 294                                 /* std,ma X,D(sp) */
 295                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 296                                         (((insn >> 4) & 0x3ff) << 3);
 297                                 dbg("analyzing func @ %lx, insn=%08x @ "
 298                                     "%lx, frame_size = %ld\n", info->ip,
 299                                     insn, npc, frame_size);
 300                         } else if (insn == 0x6bc23fd9) {
 301                                 /* stw rp,-20(sp) */
 302                                 rpoffset = 20;
 303                                 looking_for_rp = 0;
 304                                 dbg("analyzing func @ %lx, insn=stw rp,"
 305                                     "-20(sp) @ %lx\n", info->ip, npc);
 306                         } else if (insn == 0x0fc212c1) {
 307                                 /* std rp,-16(sr0,sp) */
 308                                 rpoffset = 16;
 309                                 looking_for_rp = 0;
 310                                 dbg("analyzing func @ %lx, insn=std rp,"
 311                                     "-16(sp) @ %lx\n", info->ip, npc);
 312                         }
 313                 }
 314
 315                 info->prev_sp = info->sp - frame_size;
 316                 if (e->Millicode)
 317                         info->rp = info->r31;
 318                 else if (rpoffset)
 319                         info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 320                 info->prev_ip = info->rp;
 321                 info->rp = 0;
 322
 323                 dbg("analyzing func @ %lx, setting prev_sp=%lx "
 324                     "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
 325                     info->prev_ip, npc);
 326         }
 327 }
 328
 329 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 330                        struct pt_regs *regs)
 331 {
 332         memset(info, 0, sizeof(struct unwind_frame_info));
 333         info->t = t;
 334         info->sp = regs->gr[30];
 335         info->ip = regs->iaoq[0];
 336         info->rp = regs->gr[2];
 337         info->r31 = regs->gr[31];
 338
 339         dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
 340             t ? (int)t->pid : -1, info->sp, info->ip);
 341 }
 342
 343 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 344 {
 345         struct pt_regs *r = &t->thread.regs;
 346         struct pt_regs *r2;
 347
 348         r2 = kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
 349         if (!r2)
 350                 return;
 351         *r2 = *r;
 352         r2->gr[30] = r->ksp;
 353         r2->iaoq[0] = r->kpc;
 354         unwind_frame_init(info, t, r2);
 355         kfree(r2);
 356 }
 357
 358 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 359 {
 360         unwind_frame_init(info, current, regs);
 361 }
 362
 363 int unwind_once(struct unwind_frame_info *next_frame)
 364 {
 365         unwind_frame_regs(next_frame);
 366
 367         if (next_frame->prev_sp == 0 ||
 368             next_frame->prev_ip == 0)
 369                 return -1;
 370
 371         next_frame->sp = next_frame->prev_sp;
 372         next_frame->ip = next_frame->prev_ip;
 373         next_frame->prev_sp = 0;
 374         next_frame->prev_ip = 0;
 375
 376         dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
 377             next_frame->t ? (int)next_frame->t->pid : -1,
 378             next_frame->sp, next_frame->ip);
 379
 380         return 0;
 381 }
 382
 383 int unwind_to_user(struct unwind_frame_info *info)
 384 {
 385         int ret;
 386
 387         do {
 388                 ret = unwind_once(info);
 389         } while (!ret && !(info->ip & 3));
 390
 391         return ret;
 392 }
 393
 394 module_init(unwind_init);