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      1 /* libunwind - a platform-independent unwind library
      2    Copyright (C) 2003-2004 Hewlett-Packard Co
      3 	Contributed by David Mosberger-Tang <davidm (at) hpl.hp.com>
      4 
      5 This file is part of libunwind.
      6 
      7 Permission is hereby granted, free of charge, to any person obtaining
      8 a copy of this software and associated documentation files (the
      9 "Software"), to deal in the Software without restriction, including
     10 without limitation the rights to use, copy, modify, merge, publish,
     11 distribute, sublicense, and/or sell copies of the Software, and to
     12 permit persons to whom the Software is furnished to do so, subject to
     13 the following conditions:
     14 
     15 The above copyright notice and this permission notice shall be
     16 included in all copies or substantial portions of the Software.
     17 
     18 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     19 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     20 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     21 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
     22 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
     23 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
     24 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
     25 #include <elf.h>
     26 #include <fcntl.h>
     27 #include <string.h>
     28 #include <unistd.h>
     29 
     30 #include <sys/mman.h>
     31 
     32 #include "libunwind_i.h"
     33 #include "elf64.h"
     34 
     35 static unw_word_t
     36 find_gp (struct elf_dyn_info *edi, Elf64_Phdr *pdyn, Elf64_Addr load_base)
     37 {
     38   Elf64_Off soff, str_soff;
     39   Elf64_Ehdr *ehdr = edi->ei.image;
     40   Elf64_Shdr *shdr;
     41   Elf64_Shdr *str_shdr;
     42   Elf64_Addr gp = 0;
     43   char *strtab;
     44   int i;
     45 
     46   if (pdyn)
     47     {
     48       /* If we have a PT_DYNAMIC program header, fetch the gp-value
     49 	 from the DT_PLTGOT entry.  */
     50       Elf64_Dyn *dyn = (Elf64_Dyn *) (pdyn->p_offset + (char *) edi->ei.image);
     51       for (; dyn->d_tag != DT_NULL; ++dyn)
     52 	if (dyn->d_tag == DT_PLTGOT)
     53 	  {
     54 	    gp = (Elf64_Addr) dyn->d_un.d_ptr + load_base;
     55 	    goto done;
     56 	  }
     57     }
     58 
     59   /* Without a PT_DYAMIC header, lets try to look for a non-empty .opd
     60      section.  If there is such a section, we know it's full of
     61      function descriptors, and we can simply pick up the gp from the
     62      second word of the first entry in this table.  */
     63 
     64   soff = ehdr->e_shoff;
     65   str_soff = soff + (ehdr->e_shstrndx * ehdr->e_shentsize);
     66 
     67   if (soff + ehdr->e_shnum * ehdr->e_shentsize > edi->ei.size)
     68     {
     69       Debug (1, "section table outside of image? (%lu > %lu)",
     70 	     soff + ehdr->e_shnum * ehdr->e_shentsize,
     71 	     edi->ei.size);
     72       goto done;
     73     }
     74 
     75   shdr = (Elf64_Shdr *) ((char *) edi->ei.image + soff);
     76   str_shdr = (Elf64_Shdr *) ((char *) edi->ei.image + str_soff);
     77   strtab = (char *) edi->ei.image + str_shdr->sh_offset;
     78   for (i = 0; i < ehdr->e_shnum; ++i)
     79     {
     80       if (strcmp (strtab + shdr->sh_name, ".opd") == 0
     81 	  && shdr->sh_size >= 16)
     82 	{
     83 	  gp = ((Elf64_Addr *) ((char *) edi->ei.image + shdr->sh_offset))[1];
     84 	  goto done;
     85 	}
     86       shdr = (Elf64_Shdr *) (((char *) shdr) + ehdr->e_shentsize);
     87     }
     88 
     89  done:
     90   Debug (16, "image at %p, gp = %lx\n", edi->ei.image, gp);
     91   return gp;
     92 }
     93 
     94 int
     95 ia64_find_unwind_table (struct elf_dyn_info *edi, unw_addr_space_t as,
     96 			 char *path, unw_word_t segbase, unw_word_t mapoff,
     97 			 unw_word_t ip)
     98 {
     99   Elf64_Phdr *phdr, *ptxt = NULL, *punw = NULL, *pdyn = NULL;
    100   Elf64_Ehdr *ehdr;
    101   int i;
    102 
    103   if (!_Uelf64_valid_object (&edi->ei))
    104     return -UNW_ENOINFO;
    105 
    106   ehdr = edi->ei.image;
    107   phdr = (Elf64_Phdr *) ((char *) edi->ei.image + ehdr->e_phoff);
    108 
    109   for (i = 0; i < ehdr->e_phnum; ++i)
    110     {
    111       switch (phdr[i].p_type)
    112 	{
    113 	case PT_LOAD:
    114 	  if (phdr[i].p_offset == mapoff)
    115 	    ptxt = phdr + i;
    116 	  break;
    117 
    118 	case PT_IA_64_UNWIND:
    119 	  punw = phdr + i;
    120 	  break;
    121 
    122 	case PT_DYNAMIC:
    123 	  pdyn = phdr + i;
    124 	  break;
    125 
    126 	default:
    127 	  break;
    128 	}
    129     }
    130   if (!ptxt || !punw)
    131     return 0;
    132 
    133   edi->di_cache.start_ip = segbase;
    134   edi->di_cache.end_ip = edi->di_cache.start_ip + ptxt->p_memsz;
    135   edi->di_cache.gp = find_gp (edi, pdyn, segbase - ptxt->p_vaddr);
    136   edi->di_cache.format = UNW_INFO_FORMAT_TABLE;
    137   edi->di_cache.u.ti.name_ptr = 0;
    138   edi->di_cache.u.ti.segbase = segbase;
    139   edi->di_cache.u.ti.table_len = punw->p_memsz / sizeof (unw_word_t);
    140   edi->di_cache.u.ti.table_data = (unw_word_t *)
    141     ((char *) edi->ei.image + (punw->p_vaddr - ptxt->p_vaddr));
    142   return 1;
    143 }
    144