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 #include <linux/sort.h>
  17
  18 #include <asm/uaccess.h>
  19 #include <asm/assembly.h>
  20 #include <asm/asm-offsets.h>
  21 #include <asm/ptrace.h>
  22
  23 #include <asm/unwind.h>
  24
  25 /* #define DEBUG 1 */
  26 #ifdef DEBUG
  27 #define dbg(x...) printk(x)
  28 #else
  29 #define dbg(x...)
  30 #endif
  31
  32 #define KERNEL_START (KERNEL_BINARY_TEXT_START)
  33
  34 extern struct unwind_table_entry __start___unwind[];
  35 extern struct unwind_table_entry __stop___unwind[];
  36
  37 static spinlock_t unwind_lock;
  38 /*
  39  * the kernel unwind block is not dynamically allocated so that
  40  * we can call unwind_init as early in the bootup process as
  41  * possible (before the slab allocator is initialized)
  42  */
  43 static struct unwind_table kernel_unwind_table __read_mostly;
  44 static LIST_HEAD(unwind_tables);
  45
  46 static inline const struct unwind_table_entry *
  47 find_unwind_entry_in_table(const struct unwind_table *table, unsigned long addr)
  48 {
  49         const struct unwind_table_entry *e = NULL;
  50         unsigned long lo, hi, mid;
  51
  52         lo = 0;
  53         hi = table->length - 1;
  54
  55         while (lo <= hi) {
  56                 mid = (hi - lo) / 2 + lo;
  57                 e = &table->table[mid];
  58                 if (addr < e->region_start)
  59                         hi = mid - 1;
  60                 else if (addr > e->region_end)
  61                         lo = mid + 1;
  62                 else
  63                         return e;
  64         }
  65
  66         return NULL;
  67 }
  68
  69 static const struct unwind_table_entry *
  70 find_unwind_entry(unsigned long addr)
  71 {
  72         struct unwind_table *table;
  73         const struct unwind_table_entry *e = NULL;
  74
  75         if (addr >= kernel_unwind_table.start &&
  76             addr <= kernel_unwind_table.end)
  77                 e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
  78         else {
  79                 unsigned long flags;
  80
  81                 spin_lock_irqsave(&unwind_lock, flags);
  82                 list_for_each_entry(table, &unwind_tables, list) {
  83                         if (addr >= table->start &&
  84                             addr <= table->end)
  85                                 e = find_unwind_entry_in_table(table, addr);
  86                         if (e) {
  87                                 /* Move-to-front to exploit common traces */
  88                                 list_move(&table->list, &unwind_tables);
  89                                 break;
  90                         }
  91                 }
  92                 spin_unlock_irqrestore(&unwind_lock, flags);
  93         }
  94
  95         return e;
  96 }
  97
  98 static void
  99 unwind_table_init(struct unwind_table *table, const char *name,
 100                   unsigned long base_addr, unsigned long gp,
 101                   void *table_start, void *table_end)
 102 {
 103         struct unwind_table_entry *start = table_start;
 104         struct unwind_table_entry *end =
 105                 (struct unwind_table_entry *)table_end - 1;
 106
 107         table->name = name;
 108         table->base_addr = base_addr;
 109         table->gp = gp;
 110         table->start = base_addr + start->region_start;
 111         table->end = base_addr + end->region_end;
 112         table->table = (struct unwind_table_entry *)table_start;
 113         table->length = end - start + 1;
 114         INIT_LIST_HEAD(&table->list);
 115
 116         for (; start <= end; start++) {
 117                 if (start < end &&
 118                     start->region_end > (start+1)->region_start) {
 119                         printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
 120                 }
 121
 122                 start->region_start += base_addr;
 123                 start->region_end += base_addr;
 124         }
 125 }
 126
 127 static int cmp_unwind_table_entry(const void *a, const void *b)
 128 {
 129         return ((const struct unwind_table_entry *)a)->region_start
 130              - ((const struct unwind_table_entry *)b)->region_start;
 131 }
 132
 133 static void
 134 unwind_table_sort(struct unwind_table_entry *start,
 135                   struct unwind_table_entry *finish)
 136 {
 137         sort(start, finish - start, sizeof(struct unwind_table_entry),
 138              cmp_unwind_table_entry, NULL);
 139 }
 140
 141 struct unwind_table *
 142 unwind_table_add(const char *name, unsigned long base_addr,
 143                  unsigned long gp,
 144                  void *start, void *end)
 145 {
 146         struct unwind_table *table;
 147         unsigned long flags;
 148         struct unwind_table_entry *s = (struct unwind_table_entry *)start;
 149         struct unwind_table_entry *e = (struct unwind_table_entry *)end;
 150
 151         unwind_table_sort(s, e);
 152
 153         table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 154         if (table == NULL)
 155                 return NULL;
 156         unwind_table_init(table, name, base_addr, gp, start, end);
 157         spin_lock_irqsave(&unwind_lock, flags);
 158         list_add_tail(&table->list, &unwind_tables);
 159         spin_unlock_irqrestore(&unwind_lock, flags);
 160
 161         return table;
 162 }
 163
 164 void unwind_table_remove(struct unwind_table *table)
 165 {
 166         unsigned long flags;
 167
 168         spin_lock_irqsave(&unwind_lock, flags);
 169         list_del(&table->list);
 170         spin_unlock_irqrestore(&unwind_lock, flags);
 171
 172         kfree(table);
 173 }
 174
 175 /* Called from setup_arch to import the kernel unwind info */
 176 int __init unwind_init(void)
 177 {
 178         long start, stop;
 179         register unsigned long gp __asm__ ("r27");
 180
 181         start = (long)&__start___unwind[0];
 182         stop = (long)&__stop___unwind[0];
 183
 184         spin_lock_init(&unwind_lock);
 185
 186         printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
 187             start, stop,
 188             (stop - start) / sizeof(struct unwind_table_entry));
 189
 190         unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
 191                           gp,
 192                           &__start___unwind[0], &__stop___unwind[0]);
 193 #if 0
 194         {
 195                 int i;
 196                 for (i = 0; i < 10; i++)
 197                 {
 198                         printk("region 0x%x-0x%x\n",
 199                                 __start___unwind[i].region_start,
 200                                 __start___unwind[i].region_end);
 201                 }
 202         }
 203 #endif
 204         return 0;
 205 }
 206
 207 #ifdef CONFIG_64BIT
 208 #define get_func_addr(fptr) fptr[2]
 209 #else
 210 #define get_func_addr(fptr) fptr[0]
 211 #endif
 212
 213 static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
 214 {
 215         extern void handle_interruption(int, struct pt_regs *);
 216         static unsigned long *hi = (unsigned long *)&handle_interruption;
 217
 218         if (pc == get_func_addr(hi)) {
 219                 struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
 220                 dbg("Unwinding through handle_interruption()\n");
 221                 info->prev_sp = regs->gr[30];
 222                 info->prev_ip = regs->iaoq[0];
 223
 224                 return 1;
 225         }
 226
 227         return 0;
 228 }
 229
 230 static void unwind_frame_regs(struct unwind_frame_info *info)
 231 {
 232         const struct unwind_table_entry *e;
 233         unsigned long npc;
 234         unsigned int insn;
 235         long frame_size = 0;
 236         int looking_for_rp, rpoffset = 0;
 237
 238         e = find_unwind_entry(info->ip);
 239         if (e == NULL) {
 240                 unsigned long sp;
 241
 242                 dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
 243
 244 #ifdef CONFIG_KALLSYMS
 245                 /* Handle some frequent special cases.... */
 246                 {
 247                         char symname[KSYM_NAME_LEN];
 248                         char *modname;
 249
 250                         kallsyms_lookup(info->ip, NULL, NULL, &modname,
 251                                 symname);
 252
 253                         dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
 254
 255                         if (strcmp(symname, "_switch_to_ret") == 0) {
 256                                 info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
 257                                 info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
 258                                 dbg("_switch_to_ret @ %lx - setting "
 259                                     "prev_sp=%lx prev_ip=%lx\n",
 260                                     info->ip, info->prev_sp,
 261                                     info->prev_ip);
 262                                 return;
 263                         } else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
 264                                    strcmp(symname, "syscall_exit") == 0) {
 265                                 info->prev_ip = info->prev_sp = 0;
 266                                 return;
 267                         }
 268                 }
 269 #endif
 270
 271                 /* Since we are doing the unwinding blind, we don't know if
 272                    we are adjusting the stack correctly or extracting the rp
 273                    correctly. The rp is checked to see if it belongs to the
 274                    kernel text section, if not we assume we don't have a
 275                    correct stack frame and we continue to unwind the stack.
 276                    This is not quite correct, and will fail for loadable
 277                    modules. */
 278                 sp = info->sp & ~63;
 279                 do {
 280                         unsigned long tmp;
 281
 282                         info->prev_sp = sp - 64;
 283                         info->prev_ip = 0;
 284                         if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
 285                                 break;
 286                         info->prev_ip = tmp;
 287                         sp = info->prev_sp;
 288                 } while (!kernel_text_address(info->prev_ip));
 289
 290                 info->rp = 0;
 291
 292                 dbg("analyzing func @ %lx with no unwind info, setting "
 293                     "prev_sp=%lx prev_ip=%lx\n", info->ip,
 294                     info->prev_sp, info->prev_ip);
 295         } else {
 296                 dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
 297                     "Save_RP = %d, Millicode = %d size = %u\n",
 298                     e->region_start, e->region_end, e->Save_SP, e->Save_RP,
 299                     e->Millicode, e->Total_frame_size);
 300
 301                 looking_for_rp = e->Save_RP;
 302
 303                 for (npc = e->region_start;
 304                      (frame_size < (e->Total_frame_size << 3) ||
 305                       looking_for_rp) &&
 306                      npc < info->ip;
 307                      npc += 4) {
 308
 309                         insn = *(unsigned int *)npc;
 310
 311                         if ((insn & 0xffffc001) == 0x37de0000 ||
 312                             (insn & 0xffe00001) == 0x6fc00000) {
 313                                 /* ldo X(sp), sp, or stwm X,D(sp) */
 314                                 frame_size += (insn & 0x3fff) >> 1;
 315                                 dbg("analyzing func @ %lx, insn=%08x @ "
 316                                     "%lx, frame_size = %ld\n", info->ip,
 317                                     insn, npc, frame_size);
 318                         } else if ((insn & 0xffe00009) == 0x73c00008) {
 319                                 /* std,ma X,D(sp) */
 320                                 frame_size += ((insn >> 4) & 0x3ff) << 3;
 321                                 dbg("analyzing func @ %lx, insn=%08x @ "
 322                                     "%lx, frame_size = %ld\n", info->ip,
 323                                     insn, npc, frame_size);
 324                         } else if (insn == 0x6bc23fd9) {
 325                                 /* stw rp,-20(sp) */
 326                                 rpoffset = 20;
 327                                 looking_for_rp = 0;
 328                                 dbg("analyzing func @ %lx, insn=stw rp,"
 329                                     "-20(sp) @ %lx\n", info->ip, npc);
 330                         } else if (insn == 0x0fc212c1) {
 331                                 /* std rp,-16(sr0,sp) */
 332                                 rpoffset = 16;
 333                                 looking_for_rp = 0;
 334                                 dbg("analyzing func @ %lx, insn=std rp,"
 335                                     "-16(sp) @ %lx\n", info->ip, npc);
 336                         }
 337                 }
 338
 339                 if (frame_size > e->Total_frame_size << 3)
 340                         frame_size = e->Total_frame_size << 3;
 341
 342                 if (!unwind_special(info, e->region_start, frame_size)) {
 343                         info->prev_sp = info->sp - frame_size;
 344                         if (e->Millicode)
 345                                 info->rp = info->r31;
 346                         else if (rpoffset)
 347                                 info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 348                         info->prev_ip = info->rp;
 349                         info->rp = 0;
 350                 }
 351
 352                 dbg("analyzing func @ %lx, setting prev_sp=%lx "
 353                     "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
 354                     info->prev_ip, npc);
 355         }
 356 }
 357
 358 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 359                        struct pt_regs *regs)
 360 {
 361         memset(info, 0, sizeof(struct unwind_frame_info));
 362         info->t = t;
 363         info->sp = regs->gr[30];
 364         info->ip = regs->iaoq[0];
 365         info->rp = regs->gr[2];
 366         info->r31 = regs->gr[31];
 367
 368         dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
 369             t ? (int)t->pid : -1, info->sp, info->ip);
 370 }
 371
 372 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 373 {
 374         struct pt_regs *r = &t->thread.regs;
 375         struct pt_regs *r2;
 376
 377         r2 = kmalloc(sizeof(struct pt_regs), GFP_ATOMIC);
 378         if (!r2)
 379                 return;
 380         *r2 = *r;
 381         r2->gr[30] = r->ksp;
 382         r2->iaoq[0] = r->kpc;
 383         unwind_frame_init(info, t, r2);
 384         kfree(r2);
 385 }
 386
 387 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 388 {
 389         unwind_frame_init(info, current, regs);
 390 }
 391
 392 int unwind_once(struct unwind_frame_info *next_frame)
 393 {
 394         unwind_frame_regs(next_frame);
 395
 396         if (next_frame->prev_sp == 0 ||
 397             next_frame->prev_ip == 0)
 398                 return -1;
 399
 400         next_frame->sp = next_frame->prev_sp;
 401         next_frame->ip = next_frame->prev_ip;
 402         next_frame->prev_sp = 0;
 403         next_frame->prev_ip = 0;
 404
 405         dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
 406             next_frame->t ? (int)next_frame->t->pid : -1,
 407             next_frame->sp, next_frame->ip);
 408
 409         return 0;
 410 }
 411
 412 int unwind_to_user(struct unwind_frame_info *info)
 413 {
 414         int ret;
 415
 416         do {
 417                 ret = unwind_once(info);
 418         } while (!ret && !(info->ip & 3));
 419
 420         return ret;
 421 }
 422
 423 unsigned long return_address(unsigned int level)
 424 {
 425         struct unwind_frame_info info;
 426         struct pt_regs r;
 427         unsigned long sp;
 428
 429         /* initialize unwind info */
 430         asm volatile ("copy %%r30, %0" : "=r"(sp));
 431         memset(&r, 0, sizeof(struct pt_regs));
 432         r.iaoq[0] = (unsigned long) current_text_addr();
 433         r.gr[2] = (unsigned long) __builtin_return_address(0);
 434         r.gr[30] = sp;
 435         unwind_frame_init(&info, current, &r);
 436
 437         /* unwind stack */
 438         ++level;
 439         do {
 440                 if (unwind_once(&info) < 0 || info.ip == 0)
 441                         return 0;
 442                 if (!kernel_text_address(info.ip))
 443                         return 0;
 444         } while (info.ip && level--);
 445
 446         return info.ip;
 447 }