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                 list_for_each_entry(table, &unwind_tables, list) {
  80                         if (addr >= table->start &&
  81                             addr <= table->end)
  82                                 e = find_unwind_entry_in_table(table, addr);
  83                         if (e)
  84                                 break;
  85                 }
  86
  87         return e;
  88 }
  89
  90 static void
  91 unwind_table_init(struct unwind_table *table, const char *name,
  92                   unsigned long base_addr, unsigned long gp,
  93                   void *table_start, void *table_end)
  94 {
  95         struct unwind_table_entry *start = table_start;
  96         struct unwind_table_entry *end =
  97                 (struct unwind_table_entry *)table_end - 1;
  98
  99         table->name = name;
 100         table->base_addr = base_addr;
 101         table->gp = gp;
 102         table->start = base_addr + start->region_start;
 103         table->end = base_addr + end->region_end;
 104         table->table = (struct unwind_table_entry *)table_start;
 105         table->length = end - start + 1;
 106         INIT_LIST_HEAD(&table->list);
 107
 108         for (; start <= end; start++) {
 109                 if (start < end &&
 110                     start->region_end > (start+1)->region_start) {
 111                         printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
 112                 }
 113
 114                 start->region_start += base_addr;
 115                 start->region_end += base_addr;
 116         }
 117 }
 118
 119 static int cmp_unwind_table_entry(const void *a, const void *b)
 120 {
 121         return ((const struct unwind_table_entry *)a)->region_start
 122              - ((const struct unwind_table_entry *)b)->region_start;
 123 }
 124
 125 static void
 126 unwind_table_sort(struct unwind_table_entry *start,
 127                   struct unwind_table_entry *finish)
 128 {
 129         sort(start, finish - start, sizeof(struct unwind_table_entry),
 130              cmp_unwind_table_entry, NULL);
 131 }
 132
 133 struct unwind_table *
 134 unwind_table_add(const char *name, unsigned long base_addr,
 135                  unsigned long gp,
 136                  void *start, void *end)
 137 {
 138         struct unwind_table *table;
 139         unsigned long flags;
 140         struct unwind_table_entry *s = (struct unwind_table_entry *)start;
 141         struct unwind_table_entry *e = (struct unwind_table_entry *)end;
 142
 143         unwind_table_sort(s, e);
 144
 145         table = kmalloc(sizeof(struct unwind_table), GFP_USER);
 146         if (table == NULL)
 147                 return NULL;
 148         unwind_table_init(table, name, base_addr, gp, start, end);
 149         spin_lock_irqsave(&unwind_lock, flags);
 150         list_add_tail(&table->list, &unwind_tables);
 151         spin_unlock_irqrestore(&unwind_lock, flags);
 152
 153         return table;
 154 }
 155
 156 void unwind_table_remove(struct unwind_table *table)
 157 {
 158         unsigned long flags;
 159
 160         spin_lock_irqsave(&unwind_lock, flags);
 161         list_del(&table->list);
 162         spin_unlock_irqrestore(&unwind_lock, flags);
 163
 164         kfree(table);
 165 }
 166
 167 /* Called from setup_arch to import the kernel unwind info */
 168 int unwind_init(void)
 169 {
 170         long start, stop;
 171         register unsigned long gp __asm__ ("r27");
 172
 173         start = (long)&__start___unwind[0];
 174         stop = (long)&__stop___unwind[0];
 175
 176         spin_lock_init(&unwind_lock);
 177
 178         printk("unwind_init: start = 0x%lx, end = 0x%lx, entries = %lu\n",
 179             start, stop,
 180             (stop - start) / sizeof(struct unwind_table_entry));
 181
 182         unwind_table_init(&kernel_unwind_table, "kernel", KERNEL_START,
 183                           gp,
 184                           &__start___unwind[0], &__stop___unwind[0]);
 185 #if 0
 186         {
 187                 int i;
 188                 for (i = 0; i < 10; i++)
 189                 {
 190                         printk("region 0x%x-0x%x\n",
 191                                 __start___unwind[i].region_start,
 192                                 __start___unwind[i].region_end);
 193                 }
 194         }
 195 #endif
 196         return 0;
 197 }
 198
 199 #ifdef CONFIG_64BIT
 200 #define get_func_addr(fptr) fptr[2]
 201 #else
 202 #define get_func_addr(fptr) fptr[0]
 203 #endif
 204
 205 static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
 206 {
 207         extern void handle_interruption(int, struct pt_regs *);
 208         static unsigned long *hi = (unsigned long *)&handle_interruption;
 209
 210         if (pc == get_func_addr(hi)) {
 211                 struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
 212                 dbg("Unwinding through handle_interruption()\n");
 213                 info->prev_sp = regs->gr[30];
 214                 info->prev_ip = regs->iaoq[0];
 215
 216                 return 1;
 217         }
 218
 219         return 0;
 220 }
 221
 222 static void unwind_frame_regs(struct unwind_frame_info *info)
 223 {
 224         const struct unwind_table_entry *e;
 225         unsigned long npc;
 226         unsigned int insn;
 227         long frame_size = 0;
 228         int looking_for_rp, rpoffset = 0;
 229
 230         e = find_unwind_entry(info->ip);
 231         if (e == NULL) {
 232                 unsigned long sp;
 233                 extern char _stext[], _etext[];
 234
 235                 dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
 236
 237 #ifdef CONFIG_KALLSYMS
 238                 /* Handle some frequent special cases.... */
 239                 {
 240                         char symname[KSYM_NAME_LEN];
 241                         char *modname;
 242
 243                         kallsyms_lookup(info->ip, NULL, NULL, &modname,
 244                                 symname);
 245
 246                         dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
 247
 248                         if (strcmp(symname, "_switch_to_ret") == 0) {
 249                                 info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
 250                                 info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
 251                                 dbg("_switch_to_ret @ %lx - setting "
 252                                     "prev_sp=%lx prev_ip=%lx\n",
 253                                     info->ip, info->prev_sp,
 254                                     info->prev_ip);
 255                                 return;
 256                         } else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
 257                                    strcmp(symname, "syscall_exit") == 0) {
 258                                 info->prev_ip = info->prev_sp = 0;
 259                                 return;
 260                         }
 261                 }
 262 #endif
 263
 264                 /* Since we are doing the unwinding blind, we don't know if
 265                    we are adjusting the stack correctly or extracting the rp
 266                    correctly. The rp is checked to see if it belongs to the
 267                    kernel text section, if not we assume we don't have a
 268                    correct stack frame and we continue to unwind the stack.
 269                    This is not quite correct, and will fail for loadable
 270                    modules. */
 271                 sp = info->sp & ~63;
 272                 do {
 273                         unsigned long tmp;
 274
 275                         info->prev_sp = sp - 64;
 276                         info->prev_ip = 0;
 277                         if (get_user(tmp, (unsigned long *)(info->prev_sp - RP_OFFSET)))
 278                                 break;
 279                         info->prev_ip = tmp;
 280                         sp = info->prev_sp;
 281                 } while (info->prev_ip < (unsigned long)_stext ||
 282                          info->prev_ip > (unsigned long)_etext);
 283
 284                 info->rp = 0;
 285
 286                 dbg("analyzing func @ %lx with no unwind info, setting "
 287                     "prev_sp=%lx prev_ip=%lx\n", info->ip,
 288                     info->prev_sp, info->prev_ip);
 289         } else {
 290                 dbg("e->start = 0x%x, e->end = 0x%x, Save_SP = %d, "
 291                     "Save_RP = %d, Millicode = %d size = %u\n",
 292                     e->region_start, e->region_end, e->Save_SP, e->Save_RP,
 293                     e->Millicode, e->Total_frame_size);
 294
 295                 looking_for_rp = e->Save_RP;
 296
 297                 for (npc = e->region_start;
 298                      (frame_size < (e->Total_frame_size << 3) ||
 299                       looking_for_rp) &&
 300                      npc < info->ip;
 301                      npc += 4) {
 302
 303                         insn = *(unsigned int *)npc;
 304
 305                         if ((insn & 0xffffc000) == 0x37de0000 ||
 306                             (insn & 0xffe00000) == 0x6fc00000) {
 307                                 /* ldo X(sp), sp, or stwm X,D(sp) */
 308                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 309                                         ((insn & 0x3fff) >> 1);
 310                                 dbg("analyzing func @ %lx, insn=%08x @ "
 311                                     "%lx, frame_size = %ld\n", info->ip,
 312                                     insn, npc, frame_size);
 313                         } else if ((insn & 0xffe00008) == 0x73c00008) {
 314                                 /* std,ma X,D(sp) */
 315                                 frame_size += (insn & 0x1 ? -1 << 13 : 0) |
 316                                         (((insn >> 4) & 0x3ff) << 3);
 317                                 dbg("analyzing func @ %lx, insn=%08x @ "
 318                                     "%lx, frame_size = %ld\n", info->ip,
 319                                     insn, npc, frame_size);
 320                         } else if (insn == 0x6bc23fd9) {
 321                                 /* stw rp,-20(sp) */
 322                                 rpoffset = 20;
 323                                 looking_for_rp = 0;
 324                                 dbg("analyzing func @ %lx, insn=stw rp,"
 325                                     "-20(sp) @ %lx\n", info->ip, npc);
 326                         } else if (insn == 0x0fc212c1) {
 327                                 /* std rp,-16(sr0,sp) */
 328                                 rpoffset = 16;
 329                                 looking_for_rp = 0;
 330                                 dbg("analyzing func @ %lx, insn=std rp,"
 331                                     "-16(sp) @ %lx\n", info->ip, npc);
 332                         }
 333                 }
 334
 335                 if (!unwind_special(info, e->region_start, frame_size)) {
 336                         info->prev_sp = info->sp - frame_size;
 337                         if (e->Millicode)
 338                                 info->rp = info->r31;
 339                         else if (rpoffset)
 340                                 info->rp = *(unsigned long *)(info->prev_sp - rpoffset);
 341                         info->prev_ip = info->rp;
 342                         info->rp = 0;
 343                 }
 344
 345                 dbg("analyzing func @ %lx, setting prev_sp=%lx "
 346                     "prev_ip=%lx npc=%lx\n", info->ip, info->prev_sp,
 347                     info->prev_ip, npc);
 348         }
 349 }
 350
 351 void unwind_frame_init(struct unwind_frame_info *info, struct task_struct *t,
 352                        struct pt_regs *regs)
 353 {
 354         memset(info, 0, sizeof(struct unwind_frame_info));
 355         info->t = t;
 356         info->sp = regs->gr[30];
 357         info->ip = regs->iaoq[0];
 358         info->rp = regs->gr[2];
 359         info->r31 = regs->gr[31];
 360
 361         dbg("(%d) Start unwind from sp=%08lx ip=%08lx\n",
 362             t ? (int)t->pid : -1, info->sp, info->ip);
 363 }
 364
 365 void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct task_struct *t)
 366 {
 367         struct pt_regs *r = &t->thread.regs;
 368         struct pt_regs *r2;
 369
 370         r2 = kmalloc(sizeof(struct pt_regs), GFP_ATOMIC);
 371         if (!r2)
 372                 return;
 373         *r2 = *r;
 374         r2->gr[30] = r->ksp;
 375         r2->iaoq[0] = r->kpc;
 376         unwind_frame_init(info, t, r2);
 377         kfree(r2);
 378 }
 379
 380 void unwind_frame_init_running(struct unwind_frame_info *info, struct pt_regs *regs)
 381 {
 382         unwind_frame_init(info, current, regs);
 383 }
 384
 385 int unwind_once(struct unwind_frame_info *next_frame)
 386 {
 387         unwind_frame_regs(next_frame);
 388
 389         if (next_frame->prev_sp == 0 ||
 390             next_frame->prev_ip == 0)
 391                 return -1;
 392
 393         next_frame->sp = next_frame->prev_sp;
 394         next_frame->ip = next_frame->prev_ip;
 395         next_frame->prev_sp = 0;
 396         next_frame->prev_ip = 0;
 397
 398         dbg("(%d) Continue unwind to sp=%08lx ip=%08lx\n",
 399             next_frame->t ? (int)next_frame->t->pid : -1,
 400             next_frame->sp, next_frame->ip);
 401
 402         return 0;
 403 }
 404
 405 int unwind_to_user(struct unwind_frame_info *info)
 406 {
 407         int ret;
 408
 409         do {
 410                 ret = unwind_once(info);
 411         } while (!ret && !(info->ip & 3));
 412
 413         return ret;
 414 }
 415
 416 unsigned long return_address(unsigned int level)
 417 {
 418         struct unwind_frame_info info;
 419         struct pt_regs r;
 420         unsigned long sp;
 421
 422         /* initialize unwind info */
 423         asm volatile ("copy %%r30, %0" : "=r"(sp));
 424         memset(&r, 0, sizeof(struct pt_regs));
 425         r.iaoq[0] = (unsigned long) current_text_addr();
 426         r.gr[2] = (unsigned long) __builtin_return_address(0);
 427         r.gr[30] = sp;
 428         unwind_frame_init(&info, current, &r);
 429
 430         /* unwind stack */
 431         ++level;
 432         do {
 433                 if (unwind_once(&info) < 0 || info.ip == 0)
 434                         return 0;
 435                 if (!__kernel_text_address(info.ip)) {
 436                         return 0;
 437                 }
 438         } while (info.ip && level--);
 439
 440         return info.ip;
 441 }