sysdeps/generic/unwind-dw2-fde-glibc.c

   1 /* Copyright (C) 2001, 2002, 2007 Free Software Foundation, Inc.
   2    Contributed by Jakub Jelinek <jakub@redhat.com>.
   3
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library 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 GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 /* Locate the FDE entry for a given address, using PT_GNU_EH_FRAME ELF
  22    segment and dl_iterate_phdr to avoid register/deregister calls at
  23    DSO load/unload.  */
  24
  25 #ifdef _LIBC
  26 # include <shlib-compat.h>
  27 #endif
  28
  29 #if !defined _LIBC || SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_2_5)
  30
  31 #include <link.h>
  32 #include <stddef.h>
  33
  34 #define _Unwind_Find_FDE _Unwind_Find_registered_FDE
  35
  36 #include <unwind-dw2-fde.c>
  37
  38 #undef _Unwind_Find_FDE
  39
  40 extern fde * _Unwind_Find_registered_FDE (void *pc,
  41                                           struct dwarf_eh_bases *bases);
  42 extern fde * _Unwind_Find_FDE (void *, struct dwarf_eh_bases *);
  43
  44 struct unw_eh_callback_data
  45 {
  46   _Unwind_Ptr pc;
  47   void *tbase;
  48   void *dbase;
  49   void *func;
  50   fde *ret;
  51 };
  52
  53 struct unw_eh_frame_hdr
  54 {
  55   unsigned char version;
  56   unsigned char eh_frame_ptr_enc;
  57   unsigned char fde_count_enc;
  58   unsigned char table_enc;
  59 };
  60
  61 /* Like base_of_encoded_value, but take the base from a struct object
  62    instead of an _Unwind_Context.  */
  63
  64 static _Unwind_Ptr
  65 base_from_cb_data (unsigned char encoding, struct unw_eh_callback_data *data)
  66 {
  67   if (encoding == DW_EH_PE_omit)
  68     return 0;
  69
  70   switch (encoding & 0x70)
  71     {
  72     case DW_EH_PE_absptr:
  73     case DW_EH_PE_pcrel:
  74     case DW_EH_PE_aligned:
  75       return 0;
  76
  77     case DW_EH_PE_textrel:
  78       return (_Unwind_Ptr) data->tbase;
  79     case DW_EH_PE_datarel:
  80       return (_Unwind_Ptr) data->dbase;
  81     }
  82   abort ();
  83 }
  84
  85 static int
  86 _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
  87 {
  88   struct unw_eh_callback_data *data = (struct unw_eh_callback_data *) ptr;
  89   const ElfW(Phdr) *phdr, *p_eh_frame_hdr, *p_dynamic;
  90   long n, match;
  91   _Unwind_Ptr load_base;
  92   const unsigned char *p;
  93   const struct unw_eh_frame_hdr *hdr;
  94   _Unwind_Ptr eh_frame;
  95   struct object ob;
  96
  97   /* Make sure struct dl_phdr_info is at least as big as we need.  */
  98   if (size < offsetof (struct dl_phdr_info, dlpi_phnum)
  99              + sizeof (info->dlpi_phnum))
 100     return -1;
 101
 102   match = 0;
 103   phdr = info->dlpi_phdr;
 104   load_base = info->dlpi_addr;
 105   p_eh_frame_hdr = NULL;
 106   p_dynamic = NULL;
 107
 108   /* See if PC falls into one of the loaded segments.  Find the eh_frame
 109      segment at the same time.  */
 110   for (n = info->dlpi_phnum; --n >= 0; phdr++)
 111     {
 112       if (phdr->p_type == PT_LOAD)
 113         {
 114           _Unwind_Ptr vaddr = phdr->p_vaddr + load_base;
 115           if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz)
 116             match = 1;
 117         }
 118       else if (phdr->p_type == PT_GNU_EH_FRAME)
 119         p_eh_frame_hdr = phdr;
 120       else if (phdr->p_type == PT_DYNAMIC)
 121         p_dynamic = phdr;
 122     }
 123   if (!match || !p_eh_frame_hdr)
 124     return 0;
 125
 126   /* Read .eh_frame_hdr header.  */
 127   hdr = (const struct unw_eh_frame_hdr *)
 128         (p_eh_frame_hdr->p_vaddr + load_base);
 129   if (hdr->version != 1)
 130     return 1;
 131
 132 #ifdef CRT_GET_RFIB_DATA
 133 # ifdef __i386__
 134   data->dbase = NULL;
 135   if (p_dynamic)
 136     {
 137       /* For dynamicly linked executables and shared libraries,
 138          DT_PLTGOT is the gp value for that object.  */
 139       ElfW(Dyn) *dyn = (ElfW(Dyn) *)(p_dynamic->p_vaddr + load_base);
 140       for (; dyn->d_tag != DT_NULL ; dyn++)
 141         if (dyn->d_tag == DT_PLTGOT)
 142           {
 143             /* On IA-32, _DYNAMIC is writable and GLIBC has relocated it.  */
 144             data->dbase = (void *) dyn->d_un.d_ptr;
 145             break;
 146           }
 147     }
 148 # else
 149 #  error What is DW_EH_PE_datarel base on this platform?
 150 # endif
 151 #endif
 152 #ifdef CRT_GET_RFIB_TEXT
 153 # error What is DW_EH_PE_textrel base on this platform?
 154 #endif
 155
 156   p = read_encoded_value_with_base (hdr->eh_frame_ptr_enc,
 157                                     base_from_cb_data (hdr->eh_frame_ptr_enc,
 158                                                        data),
 159                                     (const unsigned char *) (hdr + 1),
 160                                     &eh_frame);
 161
 162   /* We require here specific table encoding to speed things up.
 163      Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start
 164      as base, not the processor specific DW_EH_PE_datarel.  */
 165   if (hdr->fde_count_enc != DW_EH_PE_omit
 166       && hdr->table_enc == (DW_EH_PE_datarel | DW_EH_PE_sdata4))
 167     {
 168       _Unwind_Ptr fde_count;
 169
 170       p = read_encoded_value_with_base (hdr->fde_count_enc,
 171                                         base_from_cb_data (hdr->fde_count_enc,
 172                                                            data),
 173                                         p, &fde_count);
 174       /* Shouldn't happen.  */
 175       if (fde_count == 0)
 176         return 1;
 177       if ((((_Unwind_Ptr) p) & 3) == 0)
 178         {
 179           struct fde_table {
 180             signed initial_loc __attribute__ ((mode (SI)));
 181             signed fde __attribute__ ((mode (SI)));
 182           };
 183           const struct fde_table *table = (const struct fde_table *) p;
 184           size_t lo, hi, mid;
 185           _Unwind_Ptr data_base = (_Unwind_Ptr) hdr;
 186           fde *f;
 187           unsigned int f_enc, f_enc_size;
 188           _Unwind_Ptr range;
 189
 190           mid = fde_count - 1;
 191           if (data->pc < table[0].initial_loc + data_base)
 192             return 1;
 193           else if (data->pc < table[mid].initial_loc + data_base)
 194             {
 195               lo = 0;
 196               hi = mid;
 197
 198               while (lo < hi)
 199                 {
 200                   mid = (lo + hi) / 2;
 201                   if (data->pc < table[mid].initial_loc + data_base)
 202                     hi = mid;
 203                   else if (data->pc >= table[mid + 1].initial_loc + data_base)
 204                     lo = mid + 1;
 205                   else
 206                     break;
 207                 }
 208
 209               if (lo >= hi)
 210                 __gxx_abort ();
 211             }
 212
 213           f = (fde *) (table[mid].fde + data_base);
 214           f_enc = get_fde_encoding (f);
 215           f_enc_size = size_of_encoded_value (f_enc);
 216           read_encoded_value_with_base (f_enc & 0x0f, 0,
 217                                         &f->pc_begin[f_enc_size], &range);
 218           if (data->pc < table[mid].initial_loc + data_base + range)
 219             data->ret = f;
 220           data->func = (void *) (table[mid].initial_loc + data_base);
 221           return 1;
 222         }
 223     }
 224
 225   /* We have no sorted search table, so need to go the slow way.
 226      As soon as GLIBC will provide API so to notify that a library has been
 227      removed, we could cache this (and thus use search_object).  */
 228   ob.pc_begin = NULL;
 229   ob.tbase = data->tbase;
 230   ob.dbase = data->dbase;
 231   ob.u.single = (fde *) eh_frame;
 232   ob.s.i = 0;
 233   ob.s.b.mixed_encoding = 1;  /* Need to assume worst case.  */
 234   data->ret = linear_search_fdes (&ob, (fde *) eh_frame, (void *) data->pc);
 235   if (data->ret != NULL)
 236     {
 237       unsigned int encoding = get_fde_encoding (data->ret);
 238       _Unwind_Ptr func;
 239       read_encoded_value_with_base (encoding,
 240                                     base_from_cb_data (encoding, data),
 241                                     data->ret->pc_begin, &func);
 242       data->func = (void *) func;
 243     }
 244   return 1;
 245 }
 246
 247 # ifdef _LIBC
 248 # define dl_iterate_phdr __dl_iterate_phdr
 249 # endif
 250
 251 fde *
 252 _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
 253 {
 254   struct unw_eh_callback_data data;
 255   fde *ret;
 256
 257   ret = _Unwind_Find_registered_FDE (pc, bases);
 258   if (ret != NULL)
 259     return ret;
 260
 261   data.pc = (_Unwind_Ptr) pc;
 262   data.tbase = NULL;
 263   data.dbase = NULL;
 264   data.func = NULL;
 265   data.ret = NULL;
 266
 267   if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0)
 268     return NULL;
 269
 270   if (data.ret)
 271     {
 272       bases->tbase = data.tbase;
 273       bases->dbase = data.dbase;
 274       bases->func = data.func;
 275     }
 276   return data.ret;
 277 }
 278
 279 #endif