libgcc/unwind-dw2-fde-dip.c

   1 /* Copyright (C) 2001-2015 Free Software Foundation, Inc.
   2    Contributed by Jakub Jelinek <jakub@redhat.com>.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GCC is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* Locate the FDE entry for a given address, using PT_GNU_EH_FRAME ELF
  26    segment and dl_iterate_phdr to avoid register/deregister calls at
  27    DSO load/unload.  */
  28
  29 #ifndef _GNU_SOURCE
  30 #define _GNU_SOURCE 1
  31 #endif
  32
  33 #include "tconfig.h"
  34 #include "tsystem.h"
  35 #if !defined(inhibit_libc) && !defined(__OpenBSD__)
  36 #include <elf.h>                /* Get DT_CONFIG.  */
  37 #endif
  38 #include "coretypes.h"
  39 #include "tm.h"
  40 #include "libgcc_tm.h"
  41 #include "dwarf2.h"
  42 #include "unwind.h"
  43 #define NO_BASE_OF_ENCODED_VALUE
  44 #include "unwind-pe.h"
  45 #include "unwind-dw2-fde.h"
  46 #include "unwind-compat.h"
  47 #include "gthr.h"
  48
  49 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
  50     && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
  51         || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
  52 # define USE_PT_GNU_EH_FRAME
  53 #endif
  54
  55 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
  56     && defined(__BIONIC__)
  57 # define USE_PT_GNU_EH_FRAME
  58 #endif
  59
  60 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
  61     && defined(TARGET_DL_ITERATE_PHDR) \
  62     && (defined(__DragonFly__) || defined(__FreeBSD__))
  63 # define ElfW __ElfN
  64 # define USE_PT_GNU_EH_FRAME
  65 #endif
  66
  67 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
  68     && defined(__OpenBSD__)
  69 # define ElfW(type) Elf_##type
  70 # define USE_PT_GNU_EH_FRAME
  71 #endif
  72
  73 #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
  74     && defined(TARGET_DL_ITERATE_PHDR) \
  75     && defined(__sun__) && defined(__svr4__)
  76 # define USE_PT_GNU_EH_FRAME
  77 #endif
  78
  79 #if defined(USE_PT_GNU_EH_FRAME)
  80
  81 #include <link.h>
  82
  83 #ifndef __RELOC_POINTER
  84 # define __RELOC_POINTER(ptr, base) ((ptr) + (base))
  85 #endif
  86
  87 static const fde * _Unwind_Find_registered_FDE (void *pc, struct dwarf_eh_bases *bases);
  88
  89 #define _Unwind_Find_FDE _Unwind_Find_registered_FDE
  90 #include "unwind-dw2-fde.c"
  91 #undef _Unwind_Find_FDE
  92
  93 #ifndef PT_GNU_EH_FRAME
  94 #define PT_GNU_EH_FRAME (PT_LOOS + 0x474e550)
  95 #endif
  96
  97 struct unw_eh_callback_data
  98 {
  99   _Unwind_Ptr pc;
 100   void *tbase;
 101   void *dbase;
 102   void *func;
 103   const fde *ret;
 104   int check_cache;
 105 };
 106
 107 struct unw_eh_frame_hdr
 108 {
 109   unsigned char version;
 110   unsigned char eh_frame_ptr_enc;
 111   unsigned char fde_count_enc;
 112   unsigned char table_enc;
 113 };
 114
 115 #define FRAME_HDR_CACHE_SIZE 8
 116
 117 static struct frame_hdr_cache_element
 118 {
 119   _Unwind_Ptr pc_low;
 120   _Unwind_Ptr pc_high;
 121   _Unwind_Ptr load_base;
 122   const ElfW(Phdr) *p_eh_frame_hdr;
 123   const ElfW(Phdr) *p_dynamic;
 124   struct frame_hdr_cache_element *link;
 125 } frame_hdr_cache[FRAME_HDR_CACHE_SIZE];
 126
 127 static struct frame_hdr_cache_element *frame_hdr_cache_head;
 128
 129 /* Like base_of_encoded_value, but take the base from a struct
 130    unw_eh_callback_data instead of an _Unwind_Context.  */
 131
 132 static _Unwind_Ptr
 133 base_from_cb_data (unsigned char encoding, struct unw_eh_callback_data *data)
 134 {
 135   if (encoding == DW_EH_PE_omit)
 136     return 0;
 137
 138   switch (encoding & 0x70)
 139     {
 140     case DW_EH_PE_absptr:
 141     case DW_EH_PE_pcrel:
 142     case DW_EH_PE_aligned:
 143       return 0;
 144
 145     case DW_EH_PE_textrel:
 146       return (_Unwind_Ptr) data->tbase;
 147     case DW_EH_PE_datarel:
 148       return (_Unwind_Ptr) data->dbase;
 149     default:
 150       gcc_unreachable ();
 151     }
 152 }
 153
 154 static int
 155 _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
 156 {
 157   struct unw_eh_callback_data *data = (struct unw_eh_callback_data *) ptr;
 158   const ElfW(Phdr) *phdr, *p_eh_frame_hdr, *p_dynamic;
 159   long n, match;
 160 #ifdef __FRV_FDPIC__
 161   struct elf32_fdpic_loadaddr load_base;
 162 #else
 163   _Unwind_Ptr load_base;
 164 #endif
 165   const unsigned char *p;
 166   const struct unw_eh_frame_hdr *hdr;
 167   _Unwind_Ptr eh_frame;
 168   struct object ob;
 169   _Unwind_Ptr pc_low = 0, pc_high = 0;
 170
 171   struct ext_dl_phdr_info
 172     {
 173       ElfW(Addr) dlpi_addr;
 174       const char *dlpi_name;
 175       const ElfW(Phdr) *dlpi_phdr;
 176       ElfW(Half) dlpi_phnum;
 177       unsigned long long int dlpi_adds;
 178       unsigned long long int dlpi_subs;
 179     };
 180
 181   match = 0;
 182   phdr = info->dlpi_phdr;
 183   load_base = info->dlpi_addr;
 184   p_eh_frame_hdr = NULL;
 185   p_dynamic = NULL;
 186
 187   struct frame_hdr_cache_element *prev_cache_entry = NULL,
 188     *last_cache_entry = NULL;
 189
 190   if (data->check_cache && size >= sizeof (struct ext_dl_phdr_info))
 191     {
 192       static unsigned long long adds = -1ULL, subs;
 193       struct ext_dl_phdr_info *einfo = (struct ext_dl_phdr_info *) info;
 194
 195       /* We use a least recently used cache replacement policy.  Also,
 196          the most recently used cache entries are placed at the head
 197          of the search chain.  */
 198
 199       if (einfo->dlpi_adds == adds && einfo->dlpi_subs == subs)
 200         {
 201           /* Find data->pc in shared library cache.
 202              Set load_base, p_eh_frame_hdr and p_dynamic
 203              plus match from the cache and goto
 204              "Read .eh_frame_hdr header." below.  */
 205
 206           struct frame_hdr_cache_element *cache_entry;
 207
 208           for (cache_entry = frame_hdr_cache_head;
 209                cache_entry;
 210                cache_entry = cache_entry->link)
 211             {
 212               if (data->pc >= cache_entry->pc_low
 213                   && data->pc < cache_entry->pc_high)
 214                 {
 215                   load_base = cache_entry->load_base;
 216                   p_eh_frame_hdr = cache_entry->p_eh_frame_hdr;
 217                   p_dynamic = cache_entry->p_dynamic;
 218
 219                   /* And move the entry we're using to the head.  */
 220                   if (cache_entry != frame_hdr_cache_head)
 221                     {
 222                       prev_cache_entry->link = cache_entry->link;
 223                       cache_entry->link = frame_hdr_cache_head;
 224                       frame_hdr_cache_head = cache_entry;
 225                     }
 226                   goto found;
 227                 }
 228
 229               last_cache_entry = cache_entry;
 230               /* Exit early if we found an unused entry.  */
 231               if ((cache_entry->pc_low | cache_entry->pc_high) == 0)
 232                 break;
 233               if (cache_entry->link != NULL)
 234                 prev_cache_entry = cache_entry;
 235             }
 236         }
 237       else
 238         {
 239           adds = einfo->dlpi_adds;
 240           subs = einfo->dlpi_subs;
 241           /* Initialize the cache.  Create a chain of cache entries,
 242              with the final one terminated by a NULL link.  */
 243           int i;
 244           for (i = 0; i < FRAME_HDR_CACHE_SIZE; i++)
 245             {
 246               frame_hdr_cache[i].pc_low = 0;
 247               frame_hdr_cache[i].pc_high = 0;
 248               frame_hdr_cache[i].link = &frame_hdr_cache[i+1];
 249             }
 250           frame_hdr_cache[i-1].link = NULL;
 251           frame_hdr_cache_head = &frame_hdr_cache[0];
 252           data->check_cache = 0;
 253         }
 254     }
 255
 256   /* Make sure struct dl_phdr_info is at least as big as we need.  */
 257   if (size < offsetof (struct dl_phdr_info, dlpi_phnum)
 258              + sizeof (info->dlpi_phnum))
 259     return -1;
 260
 261   /* See if PC falls into one of the loaded segments.  Find the eh_frame
 262      segment at the same time.  */
 263   for (n = info->dlpi_phnum; --n >= 0; phdr++)
 264     {
 265       if (phdr->p_type == PT_LOAD)
 266         {
 267           _Unwind_Ptr vaddr = (_Unwind_Ptr)
 268             __RELOC_POINTER (phdr->p_vaddr, load_base);
 269           if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz)
 270             {
 271               match = 1;
 272               pc_low = vaddr;
 273               pc_high =  vaddr + phdr->p_memsz;
 274             }
 275         }
 276       else if (phdr->p_type == PT_GNU_EH_FRAME)
 277         p_eh_frame_hdr = phdr;
 278 #ifdef PT_SUNW_UNWIND
 279       /* Sun ld emits PT_SUNW_UNWIND .eh_frame_hdr sections instead of
 280          PT_SUNW_EH_FRAME/PT_GNU_EH_FRAME, so accept them as well.  */
 281       else if (phdr->p_type == PT_SUNW_UNWIND)
 282         p_eh_frame_hdr = phdr;
 283 #endif
 284       else if (phdr->p_type == PT_DYNAMIC)
 285         p_dynamic = phdr;
 286     }
 287
 288   if (!match)
 289     return 0;
 290
 291   if (size >= sizeof (struct ext_dl_phdr_info))
 292     {
 293       /* Move the cache entry we're about to overwrite to the head of
 294          the list.  If either last_cache_entry or prev_cache_entry are
 295          NULL, that cache entry is already at the head.  */
 296       if (last_cache_entry != NULL && prev_cache_entry != NULL)
 297         {
 298           prev_cache_entry->link = last_cache_entry->link;
 299           last_cache_entry->link = frame_hdr_cache_head;
 300           frame_hdr_cache_head = last_cache_entry;
 301         }
 302
 303       frame_hdr_cache_head->load_base = load_base;
 304       frame_hdr_cache_head->p_eh_frame_hdr = p_eh_frame_hdr;
 305       frame_hdr_cache_head->p_dynamic = p_dynamic;
 306       frame_hdr_cache_head->pc_low = pc_low;
 307       frame_hdr_cache_head->pc_high = pc_high;
 308     }
 309
 310  found:
 311
 312   if (!p_eh_frame_hdr)
 313     return 0;
 314
 315   /* Read .eh_frame_hdr header.  */
 316   hdr = (const struct unw_eh_frame_hdr *)
 317     __RELOC_POINTER (p_eh_frame_hdr->p_vaddr, load_base);
 318   if (hdr->version != 1)
 319     return 1;
 320
 321 #ifdef CRT_GET_RFIB_DATA
 322 # ifdef __i386__
 323   data->dbase = NULL;
 324   if (p_dynamic)
 325     {
 326       /* For dynamically linked executables and shared libraries,
 327          DT_PLTGOT is the gp value for that object.  */
 328       ElfW(Dyn) *dyn = (ElfW(Dyn) *)
 329         __RELOC_POINTER (p_dynamic->p_vaddr, load_base);
 330       for (; dyn->d_tag != DT_NULL ; dyn++)
 331         if (dyn->d_tag == DT_PLTGOT)
 332           {
 333             data->dbase = (void *) dyn->d_un.d_ptr;
 334 #if defined __linux__
 335             /* On IA-32 Linux, _DYNAMIC is writable and GLIBC has
 336                relocated it.  */
 337 #elif defined __sun__ && defined __svr4__
 338             /* On Solaris 2/x86, we need to do this ourselves.  */
 339             data->dbase += load_base;
 340 #endif
 341             break;
 342           }
 343     }
 344 # elif defined __FRV_FDPIC__ && defined __linux__
 345   data->dbase = load_base.got_value;
 346 # else
 347 #  error What is DW_EH_PE_datarel base on this platform?
 348 # endif
 349 #endif
 350
 351   p = read_encoded_value_with_base (hdr->eh_frame_ptr_enc,
 352                                     base_from_cb_data (hdr->eh_frame_ptr_enc,
 353                                                        data),
 354                                     (const unsigned char *) (hdr + 1),
 355                                     &eh_frame);
 356
 357   /* We require here specific table encoding to speed things up.
 358      Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start
 359      as base, not the processor specific DW_EH_PE_datarel.  */
 360   if (hdr->fde_count_enc != DW_EH_PE_omit
 361       && hdr->table_enc == (DW_EH_PE_datarel | DW_EH_PE_sdata4))
 362     {
 363       _Unwind_Ptr fde_count;
 364
 365       p = read_encoded_value_with_base (hdr->fde_count_enc,
 366                                         base_from_cb_data (hdr->fde_count_enc,
 367                                                            data),
 368                                         p, &fde_count);
 369       /* Shouldn't happen.  */
 370       if (fde_count == 0)
 371         return 1;
 372       if ((((_Unwind_Ptr) p) & 3) == 0)
 373         {
 374           struct fde_table {
 375             signed initial_loc __attribute__ ((mode (SI)));
 376             signed fde __attribute__ ((mode (SI)));
 377           };
 378           const struct fde_table *table = (const struct fde_table *) p;
 379           size_t lo, hi, mid;
 380           _Unwind_Ptr data_base = (_Unwind_Ptr) hdr;
 381           fde *f;
 382           unsigned int f_enc, f_enc_size;
 383           _Unwind_Ptr range;
 384
 385           mid = fde_count - 1;
 386           if (data->pc < table[0].initial_loc + data_base)
 387             return 1;
 388           else if (data->pc < table[mid].initial_loc + data_base)
 389             {
 390               lo = 0;
 391               hi = mid;
 392
 393               while (lo < hi)
 394                 {
 395                   mid = (lo + hi) / 2;
 396                   if (data->pc < table[mid].initial_loc + data_base)
 397                     hi = mid;
 398                   else if (data->pc >= table[mid + 1].initial_loc + data_base)
 399                     lo = mid + 1;
 400                   else
 401                     break;
 402                 }
 403
 404               gcc_assert (lo < hi);
 405             }
 406
 407           f = (fde *) (table[mid].fde + data_base);
 408           f_enc = get_fde_encoding (f);
 409           f_enc_size = size_of_encoded_value (f_enc);
 410           read_encoded_value_with_base (f_enc & 0x0f, 0,
 411                                         &f->pc_begin[f_enc_size], &range);
 412           if (data->pc < table[mid].initial_loc + data_base + range)
 413             data->ret = f;
 414           data->func = (void *) (table[mid].initial_loc + data_base);
 415           return 1;
 416         }
 417     }
 418
 419   /* We have no sorted search table, so need to go the slow way.
 420      As soon as GLIBC will provide API so to notify that a library has been
 421      removed, we could cache this (and thus use search_object).  */
 422   ob.pc_begin = NULL;
 423   ob.tbase = data->tbase;
 424   ob.dbase = data->dbase;
 425   ob.u.single = (fde *) eh_frame;
 426   ob.s.i = 0;
 427   ob.s.b.mixed_encoding = 1;  /* Need to assume worst case.  */
 428   data->ret = linear_search_fdes (&ob, (fde *) eh_frame, (void *) data->pc);
 429   if (data->ret != NULL)
 430     {
 431       _Unwind_Ptr func;
 432       unsigned int encoding = get_fde_encoding (data->ret);
 433
 434       read_encoded_value_with_base (encoding,
 435                                     base_from_cb_data (encoding, data),
 436                                     data->ret->pc_begin, &func);
 437       data->func = (void *) func;
 438     }
 439   return 1;
 440 }
 441
 442 const fde *
 443 _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
 444 {
 445   struct unw_eh_callback_data data;
 446   const fde *ret;
 447
 448   ret = _Unwind_Find_registered_FDE (pc, bases);
 449   if (ret != NULL)
 450     return ret;
 451
 452   data.pc = (_Unwind_Ptr) pc;
 453   data.tbase = NULL;
 454   data.dbase = NULL;
 455   data.func = NULL;
 456   data.ret = NULL;
 457   data.check_cache = 1;
 458
 459   if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0)
 460     return NULL;
 461
 462   if (data.ret)
 463     {
 464       bases->tbase = data.tbase;
 465       bases->dbase = data.dbase;
 466       bases->func = data.func;
 467     }
 468   return data.ret;
 469 }
 470
 471 #else
 472 /* Prevent multiple include of header files.  */
 473 #define _Unwind_Find_FDE _Unwind_Find_FDE
 474 #include "unwind-dw2-fde.c"
 475 #endif
 476
 477 #if defined (USE_GAS_SYMVER) && defined (SHARED) && defined (USE_LIBUNWIND_EXCEPTIONS)
 478 alias (_Unwind_Find_FDE);
 479 #endif