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      1 /* Recover relocatibility for addresses computed from debug information.
      2    Copyright (C) 2005, 2006, 2007, 2008 Red Hat, Inc.
      3    This file is part of Red Hat elfutils.
      4 
      5    Red Hat elfutils is free software; you can redistribute it and/or modify
      6    it under the terms of the GNU General Public License as published by the
      7    Free Software Foundation; version 2 of the License.
      8 
      9    Red Hat elfutils is distributed in the hope that it will be useful, but
     10    WITHOUT ANY WARRANTY; without even the implied warranty of
     11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     12    General Public License for more details.
     13 
     14    You should have received a copy of the GNU General Public License along
     15    with Red Hat elfutils; if not, write to the Free Software Foundation,
     16    Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
     17 
     18    In addition, as a special exception, Red Hat, Inc. gives You the
     19    additional right to link the code of Red Hat elfutils with code licensed
     20    under any Open Source Initiative certified open source license
     21    (http://www.opensource.org/licenses/index.php) which requires the
     22    distribution of source code with any binary distribution and to
     23    distribute linked combinations of the two.  Non-GPL Code permitted under
     24    this exception must only link to the code of Red Hat elfutils through
     25    those well defined interfaces identified in the file named EXCEPTION
     26    found in the source code files (the "Approved Interfaces").  The files
     27    of Non-GPL Code may instantiate templates or use macros or inline
     28    functions from the Approved Interfaces without causing the resulting
     29    work to be covered by the GNU General Public License.  Only Red Hat,
     30    Inc. may make changes or additions to the list of Approved Interfaces.
     31    Red Hat's grant of this exception is conditioned upon your not adding
     32    any new exceptions.  If you wish to add a new Approved Interface or
     33    exception, please contact Red Hat.  You must obey the GNU General Public
     34    License in all respects for all of the Red Hat elfutils code and other
     35    code used in conjunction with Red Hat elfutils except the Non-GPL Code
     36    covered by this exception.  If you modify this file, you may extend this
     37    exception to your version of the file, but you are not obligated to do
     38    so.  If you do not wish to provide this exception without modification,
     39    you must delete this exception statement from your version and license
     40    this file solely under the GPL without exception.
     41 
     42    Red Hat elfutils is an included package of the Open Invention Network.
     43    An included package of the Open Invention Network is a package for which
     44    Open Invention Network licensees cross-license their patents.  No patent
     45    license is granted, either expressly or impliedly, by designation as an
     46    included package.  Should you wish to participate in the Open Invention
     47    Network licensing program, please visit www.openinventionnetwork.com
     48    <http://www.openinventionnetwork.com>.  */
     49 
     50 #include "libdwflP.h"
     51 #include <fcntl.h>
     52 #include <unistd.h>
     53 
     54 /* Since dwfl_report_elf lays out the sections already, this will only be
     55    called when the section headers of the debuginfo file are being
     56    consulted instead, or for the section placed at 0.  With binutils
     57    strip-to-debug, the symbol table is in the debuginfo file and relocation
     58    looks there.  */
     59 int
     60 dwfl_offline_section_address (Dwfl_Module *mod,
     61 			      void **userdata __attribute__ ((unused)),
     62 			      const char *modname __attribute__ ((unused)),
     63 			      Dwarf_Addr base __attribute__ ((unused)),
     64 			      const char *secname __attribute__ ((unused)),
     65 			      Elf32_Word shndx,
     66 			      const GElf_Shdr *shdr __attribute__ ((unused)),
     67 			      Dwarf_Addr *addr)
     68 {
     69   assert (mod->e_type == ET_REL);
     70   assert (shdr->sh_addr == 0);
     71   assert (shdr->sh_flags & SHF_ALLOC);
     72 
     73   if (mod->debug.elf == NULL)
     74     /* We are only here because sh_addr is zero even though layout is complete.
     75        The first section in the first file under -e is placed at 0.  */
     76     return 0;
     77 
     78   /* The section numbers might not match between the two files.
     79      The best we can rely on is the order of SHF_ALLOC sections.  */
     80 
     81   Elf_Scn *ourscn = elf_getscn (mod->debug.elf, shndx);
     82   Elf_Scn *scn = NULL;
     83   uint_fast32_t skip_alloc = 0;
     84   while ((scn = elf_nextscn (mod->debug.elf, scn)) != ourscn)
     85     {
     86       assert (scn != NULL);
     87       GElf_Shdr shdr_mem;
     88       GElf_Shdr *sh = gelf_getshdr (scn, &shdr_mem);
     89       if (unlikely (sh == NULL))
     90 	return -1;
     91       if (sh->sh_flags & SHF_ALLOC)
     92 	++skip_alloc;
     93     }
     94 
     95   scn = NULL;
     96   while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
     97     {
     98       GElf_Shdr shdr_mem;
     99       GElf_Shdr *main_shdr = gelf_getshdr (scn, &shdr_mem);
    100       if (unlikely (main_shdr == NULL))
    101 	return -1;
    102       if ((main_shdr->sh_flags & SHF_ALLOC) && skip_alloc-- == 0)
    103 	{
    104 	  assert (main_shdr->sh_flags == shdr->sh_flags);
    105 	  *addr = main_shdr->sh_addr;
    106 	  return 0;
    107 	}
    108     }
    109 
    110   /* This should never happen.  */
    111   return -1;
    112 }
    113 INTDEF (dwfl_offline_section_address)
    114 
    115 /* Forward declarations.  */
    116 static Dwfl_Module *process_elf (Dwfl *dwfl, const char *name,
    117 				 const char *file_name, int fd, Elf *elf);
    118 static Dwfl_Module *process_archive (Dwfl *dwfl, const char *name,
    119 				     const char *file_name, int fd, Elf *elf,
    120 				     int (*predicate) (const char *module,
    121 						       const char *file));
    122 
    123 /* Report one module for an ELF file, or many for an archive.
    124    Always consumes ELF and FD.  */
    125 static Dwfl_Module *
    126 process_file (Dwfl *dwfl, const char *name, const char *file_name, int fd,
    127 	      Elf *elf, int (*predicate) (const char *module,
    128 					  const char *file))
    129 {
    130   switch (elf_kind (elf))
    131     {
    132     default:
    133     case ELF_K_NONE:
    134       __libdwfl_seterrno (elf == NULL ? DWFL_E_LIBELF : DWFL_E_BADELF);
    135       return NULL;
    136 
    137     case ELF_K_ELF:
    138       return process_elf (dwfl, name, file_name, fd, elf);
    139 
    140     case ELF_K_AR:
    141       return process_archive (dwfl, name, file_name, fd, elf, predicate);
    142     }
    143 }
    144 
    145 /* Report the open ELF file as a module.  Always consumes ELF and FD.  */
    146 static Dwfl_Module *
    147 process_elf (Dwfl *dwfl, const char *name, const char *file_name, int fd,
    148 	     Elf *elf)
    149 {
    150   Dwfl_Module *mod = __libdwfl_report_elf (dwfl, name, file_name, fd, elf,
    151 					   dwfl->offline_next_address);
    152   if (mod != NULL)
    153     {
    154       /* If this is an ET_EXEC file with fixed addresses, the address range
    155 	 it consumed may or may not intersect with the arbitrary range we
    156 	 will use for relocatable modules.  Make sure we always use a free
    157 	 range for the offline allocations.  If this module did use
    158 	 offline_next_address, it may have rounded it up for the module's
    159 	 alignment requirements.  */
    160       if ((dwfl->offline_next_address >= mod->low_addr
    161 	   || mod->low_addr - dwfl->offline_next_address < OFFLINE_REDZONE)
    162 	  && dwfl->offline_next_address < mod->high_addr + OFFLINE_REDZONE)
    163 	dwfl->offline_next_address = mod->high_addr + OFFLINE_REDZONE;
    164 
    165       /* Don't keep the file descriptor around.  */
    166       if (mod->main.fd != -1 && elf_cntl (mod->main.elf, ELF_C_FDREAD) == 0)
    167 	{
    168 	  close (mod->main.fd);
    169 	  mod->main.fd = -1;
    170 	}
    171     }
    172 
    173   return mod;
    174 }
    175 
    176 /* Always consumes MEMBER.  Returns elf_next result on success.
    177    For errors returns ELF_C_NULL with *MOD set to null.  */
    178 static Elf_Cmd
    179 process_archive_member (Dwfl *dwfl, const char *name, const char *file_name,
    180 			int (*predicate) (const char *module, const char *file),
    181 			int fd, Elf *member, Dwfl_Module **mod)
    182 {
    183   const Elf_Arhdr *h = elf_getarhdr (member);
    184   if (unlikely (h == NULL))
    185     {
    186       __libdwfl_seterrno (DWFL_E_LIBELF);
    187     fail:
    188       elf_end (member);
    189       *mod = NULL;
    190       return ELF_C_NULL;
    191     }
    192 
    193   if (!strcmp (h->ar_name, "/") || !strcmp (h->ar_name, "//"))
    194     {
    195     skip:;
    196       /* Skip this and go to the next.  */
    197       Elf_Cmd result = elf_next (member);
    198       elf_end (member);
    199       return result;
    200     }
    201 
    202   char *member_name;
    203   if (unlikely (asprintf (&member_name, "%s(%s)", file_name, h->ar_name) < 0))
    204     {
    205     nomem:
    206       __libdwfl_seterrno (DWFL_E_NOMEM);
    207       elf_end (member);
    208       *mod = NULL;
    209       return ELF_C_NULL;
    210     }
    211 
    212   char *module_name = NULL;
    213   if (name == NULL || name[0] == '\0')
    214     name = h->ar_name;
    215   else if (unlikely (asprintf (&module_name, "%s:%s", name, h->ar_name) < 0))
    216     {
    217       free (member_name);
    218       goto nomem;
    219     }
    220   else
    221     name = module_name;
    222 
    223   if (predicate != NULL)
    224     {
    225       /* Let the predicate decide whether to use this one.  */
    226       int want = (*predicate) (name, member_name);
    227       if (want <= 0)
    228 	{
    229 	  free (member_name);
    230 	  free (module_name);
    231 	  if (unlikely (want < 0))
    232 	    {
    233 	      __libdwfl_seterrno (DWFL_E_CB);
    234 	      goto fail;
    235 	    }
    236 	  goto skip;
    237 	}
    238     }
    239 
    240   /* We let __libdwfl_report_elf cache the fd in mod->main.fd,
    241      though it's the same fd for all the members.
    242      On module teardown we will close it only on the last Elf reference.  */
    243   *mod = process_file (dwfl, name, member_name, fd, member, predicate);
    244   free (member_name);
    245   free (module_name);
    246 
    247   if (*mod == NULL)		/* process_file called elf_end.  */
    248     return ELF_C_NULL;
    249 
    250   /* Advance the archive-reading offset for the next iteration.  */
    251   return elf_next (member);
    252 }
    253 
    254 /* Report each member of the archive as its own module.  */
    255 static Dwfl_Module *
    256 process_archive (Dwfl *dwfl, const char *name, const char *file_name, int fd,
    257 		 Elf *archive,
    258 		 int (*predicate) (const char *module, const char *file))
    259 
    260 {
    261   Dwfl_Module *mod = NULL;
    262   Elf *member = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, archive);
    263   if (unlikely (member == NULL)) /* Empty archive.  */
    264     {
    265       __libdwfl_seterrno (DWFL_E_BADELF);
    266       return NULL;
    267     }
    268 
    269   while (process_archive_member (dwfl, name, file_name, predicate,
    270 				 fd, member, &mod) != ELF_C_NULL)
    271     member = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, archive);
    272 
    273   /* We can drop the archive Elf handle even if we're still using members
    274      in live modules.  When the last module's elf_end on a member returns
    275      zero, that module will close FD.  If no modules survived the predicate,
    276      we are all done with the file right here.  */
    277   if (mod != NULL		/* If no modules, caller will clean up.  */
    278       && elf_end (archive) == 0)
    279     close (fd);
    280 
    281   return mod;
    282 }
    283 
    284 Dwfl_Module *
    285 internal_function
    286 __libdwfl_report_offline (Dwfl *dwfl, const char *name,
    287 			  const char *file_name, int fd, bool closefd,
    288 			  int (*predicate) (const char *module,
    289 					    const char *file))
    290 {
    291   Elf *elf = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, NULL);
    292   Dwfl_Module *mod = process_file (dwfl, name, file_name, fd, elf, predicate);
    293   if (mod == NULL)
    294     {
    295       elf_end (elf);
    296       if (closefd)
    297 	close (fd);
    298     }
    299   return mod;
    300 }
    301 
    302 Dwfl_Module *
    303 dwfl_report_offline (Dwfl *dwfl, const char *name,
    304 		     const char *file_name, int fd)
    305 {
    306   if (dwfl == NULL)
    307     return NULL;
    308 
    309   bool closefd = false;
    310   if (fd < 0)
    311     {
    312       closefd = true;
    313       fd = open64 (file_name, O_RDONLY);
    314       if (fd < 0)
    315 	{
    316 	  __libdwfl_seterrno (DWFL_E_ERRNO);
    317 	  return NULL;
    318 	}
    319     }
    320 
    321   return __libdwfl_report_offline (dwfl, name, file_name, fd, closefd, NULL);
    322 }
    323 INTDEF (dwfl_report_offline)
    324