/* Create descriptor from ELF descriptor for processing file.

   Copyright (C) 2002-2011, 2014, 2015, 2017, 2018 Red Hat, Inc.

   This file is part of elfutils.

   This file is free software; you can redistribute it and/or modify

   it under the terms of either

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at

       your option) any later version

   or

     * the GNU General Public License as published by the Free

       Software Foundation; either version 2 of the License, or (at

       your option) any later version

   or both in parallel, as here.

   elfutils is distributed in the hope that it will be useful, but

   WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   General Public License for more details.

   You should have received copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H

# include <config.h>

#endif

#include <assert.h>

#include <stdbool.h>

#include <stddef.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <endian.h>

#include "libelfP.h"

#include "libdwP.h"

/* Section names.  (Note .debug_str_offsets is the largest 19 chars.)  */

static const char dwarf_scnnames[IDX_last][19] =

{

  [IDX_debug_info] = ".debug_info",

  [IDX_debug_types] = ".debug_types",

  [IDX_debug_abbrev] = ".debug_abbrev",

  [IDX_debug_addr] = ".debug_addr",

  [IDX_debug_aranges] = ".debug_aranges",

  [IDX_debug_line] = ".debug_line",

  [IDX_debug_line_str] = ".debug_line_str",

  [IDX_debug_frame] = ".debug_frame",

  [IDX_debug_loc] = ".debug_loc",

  [IDX_debug_loclists] = ".debug_loclists",

  [IDX_debug_pubnames] = ".debug_pubnames",

  [IDX_debug_str] = ".debug_str",

  [IDX_debug_str_offsets] = ".debug_str_offsets",

  [IDX_debug_macinfo] = ".debug_macinfo",

  [IDX_debug_macro] = ".debug_macro",

  [IDX_debug_ranges] = ".debug_ranges",

  [IDX_debug_rnglists] = ".debug_rnglists",

  [IDX_gnu_debugaltlink] = ".gnu_debugaltlink"

};

#define ndwarf_scnnames (sizeof (dwarf_scnnames) / sizeof (dwarf_scnnames[0]))

static Dwarf *

check_section (Dwarf *result, size_t shstrndx, Elf_Scn *scn, bool inscngrp)

{

  GElf_Shdr shdr_mem;

  GElf_Shdr *shdr;

  /* Get the section header data.  */

  shdr = gelf_getshdr (scn, &shdr_mem);

  if (shdr == NULL)

    /* We may read /proc/PID/mem with only program headers mapped and section

       headers out of the mapped pages.  */

    goto err;

  /* Ignore any SHT_NOBITS sections.  Debugging sections should not

     have been stripped, but in case of a corrupt file we won't try

     to look at the missing data.  */

  if (unlikely (shdr->sh_type == SHT_NOBITS))

    return result;

  /* Make sure the section is part of a section group only iff we

     really need it.  If we are looking for the global (= non-section

     group debug info) we have to ignore all the info in section

     groups.  If we are looking into a section group we cannot look at

     a section which isn't part of the section group.  */

  if (! inscngrp && (shdr->sh_flags & SHF_GROUP) != 0)

    /* Ignore the section.  */

    return result;

  /* We recognize the DWARF section by their names.  This is not very

     safe and stable but the best we can do.  */

  const char *scnname = elf_strptr (result->elf, shstrndx,

				    shdr->sh_name);

  if (scnname == NULL)

    {

      /* The section name must be valid.  Otherwise is the ELF file

	 invalid.  */

    err:

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      __libdw_seterrno (DWARF_E_INVALID_ELF);

      free (result);

      return NULL;

    }

  /* Recognize the various sections.  Most names start with .debug_.  */

  size_t cnt;

  bool gnu_compressed = false;

  for (cnt = 0; cnt < ndwarf_scnnames; ++cnt)

    {

      size_t dbglen = strlen (dwarf_scnnames[cnt]);

      size_t scnlen = strlen (scnname);

      if (strncmp (scnname, dwarf_scnnames[cnt], dbglen) == 0

	  && (dbglen == scnlen

	      || (scnlen == dbglen + 4

		  && strstr (scnname, ".dwo") == scnname + dbglen)))

	break;

      else if (scnname[0] == '.' && scnname[1] == 'z'

	       && (strncmp (&scnname[2], &dwarf_scnnames[cnt][1],

			    dbglen - 1) == 0

		   && (scnlen == dbglen + 1

		       || (scnlen == dbglen + 5

			   && strstr (scnname,

				      ".dwo") == scnname + dbglen + 1))))

	{

	  gnu_compressed = true;

	  break;

	}

      else if (scnlen > 14 /* .gnu.debuglto_ prefix. */

	       && strncmp (scnname, ".gnu.debuglto_", 14) == 0

	       && strcmp (&scnname[14], dwarf_scnnames[cnt]) == 0)

	break;

    }

  if (cnt >= ndwarf_scnnames)

    /* Not a debug section; ignore it. */

    return result;

  if (unlikely (result->sectiondata[cnt] != NULL))

    /* A section appears twice.  That's bad.  We ignore the section.  */

    return result;

  /* We cannot know whether or not a GNU compressed section has already

     been uncompressed or not, so ignore any errors.  */

  if (gnu_compressed)

    elf_compress_gnu (scn, 0, 0);

  if ((shdr->sh_flags & SHF_COMPRESSED) != 0)

    {

      if (elf_compress (scn, 0, 0) < 0)

	{

	  /* It would be nice if we could fail with a specific error.

	     But we don't know if this was an essential section or not.

	     So just continue for now. See also valid_p().  */

	  return result;

	}

    }

  /* Get the section data.  */

  Elf_Data *data = elf_getdata (scn, NULL);

  if (data == NULL)

    goto err;

  if (data->d_buf == NULL || data->d_size == 0)

    /* No data actually available, ignore it. */

    return result;

  /* We can now read the section data into results. */

  result->sectiondata[cnt] = data;

  return result;

}

/* Helper function to set debugdir field.  We want to cache the dir

   where we found this Dwarf ELF file to locate alt and dwo files.  */

char *

__libdw_debugdir (int fd)

{

  /* strlen ("/proc/self/fd/") = 14 + strlen (<MAXINT>) = 10 + 1 = 25.  */

  char devfdpath[25];

  sprintf (devfdpath, "/proc/self/fd/%u", fd);

  char *fdpath = realpath (devfdpath, NULL);

  char *fddir;

  if (fdpath != NULL && fdpath[0] == '/'

      && (fddir = strrchr (fdpath, '/')) != NULL)

    {

      *++fddir = '\0';

      return fdpath;

    }

  return NULL;

}

/* Check whether all the necessary DWARF information is available.  */

static Dwarf *

valid_p (Dwarf *result)

{

  /* We looked at all the sections.  Now determine whether all the

     sections with debugging information we need are there.

     Require at least one section that can be read "standalone".  */

  if (likely (result != NULL)

      && unlikely (result->sectiondata[IDX_debug_info] == NULL

		   && result->sectiondata[IDX_debug_line] == NULL

		   && result->sectiondata[IDX_debug_frame] == NULL))

    {

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      __libdw_seterrno (DWARF_E_NO_DWARF);

      free (result);

      result = NULL;

    }

  /* For dwarf_location_attr () we need a "fake" CU to indicate

     where the "fake" attribute data comes from.  This is a block

     inside the .debug_loc or .debug_loclists section.  */

  if (result != NULL && result->sectiondata[IDX_debug_loc] != NULL)

    {

      result->fake_loc_cu = (Dwarf_CU *) malloc (sizeof (Dwarf_CU));

      if (unlikely (result->fake_loc_cu == NULL))

	{

	  Dwarf_Sig8_Hash_free (&result->sig8_hash);

	  __libdw_seterrno (DWARF_E_NOMEM);

	  free (result);

	  result = NULL;

	}

      else

	{

	  result->fake_loc_cu->sec_idx = IDX_debug_loc;

	  result->fake_loc_cu->dbg = result;

	  result->fake_loc_cu->startp

	    = result->sectiondata[IDX_debug_loc]->d_buf;

	  result->fake_loc_cu->endp

	    = (result->sectiondata[IDX_debug_loc]->d_buf

	       + result->sectiondata[IDX_debug_loc]->d_size);

	  result->fake_loc_cu->locs = NULL;

	  result->fake_loc_cu->address_size = 0;

	  result->fake_loc_cu->version = 0;

	  result->fake_loc_cu->split = NULL;

	}

    }

  if (result != NULL && result->sectiondata[IDX_debug_loclists] != NULL)

    {

      result->fake_loclists_cu = (Dwarf_CU *) malloc (sizeof (Dwarf_CU));

      if (unlikely (result->fake_loclists_cu == NULL))

	{

	  Dwarf_Sig8_Hash_free (&result->sig8_hash);

	  __libdw_seterrno (DWARF_E_NOMEM);

	  free (result->fake_loc_cu);

	  free (result);

	  result = NULL;

	}

      else

	{

	  result->fake_loclists_cu->sec_idx = IDX_debug_loclists;

	  result->fake_loclists_cu->dbg = result;

	  result->fake_loclists_cu->startp

	    = result->sectiondata[IDX_debug_loclists]->d_buf;

	  result->fake_loclists_cu->endp

	    = (result->sectiondata[IDX_debug_loclists]->d_buf

	       + result->sectiondata[IDX_debug_loclists]->d_size);

	  result->fake_loclists_cu->locs = NULL;

	  result->fake_loclists_cu->address_size = 0;

	  result->fake_loclists_cu->version = 0;

	  result->fake_loclists_cu->split = NULL;

	}

    }

  /* For DW_OP_constx/GNU_const_index and DW_OP_addrx/GNU_addr_index

     the dwarf_location_attr () will need a "fake" address CU to

     indicate where the attribute data comes from.  This is a just

     inside the .debug_addr section, if it exists.  */

  if (result != NULL && result->sectiondata[IDX_debug_addr] != NULL)

    {

      result->fake_addr_cu = (Dwarf_CU *) malloc (sizeof (Dwarf_CU));

      if (unlikely (result->fake_addr_cu == NULL))

	{

	  Dwarf_Sig8_Hash_free (&result->sig8_hash);

	  __libdw_seterrno (DWARF_E_NOMEM);

	  free (result->fake_loc_cu);

	  free (result->fake_loclists_cu);

	  free (result);

	  result = NULL;

	}

      else

	{

	  result->fake_addr_cu->sec_idx = IDX_debug_addr;

	  result->fake_addr_cu->dbg = result;

	  result->fake_addr_cu->startp

	    = result->sectiondata[IDX_debug_addr]->d_buf;

	  result->fake_addr_cu->endp

	    = (result->sectiondata[IDX_debug_addr]->d_buf

	       + result->sectiondata[IDX_debug_addr]->d_size);

	  result->fake_addr_cu->locs = NULL;

	  result->fake_addr_cu->address_size = 0;

	  result->fake_addr_cu->version = 0;

	  result->fake_addr_cu->split = NULL;

	}

    }

  if (result != NULL)

    result->debugdir = __libdw_debugdir (result->elf->fildes);

  return result;

}

static Dwarf *

global_read (Dwarf *result, Elf *elf, size_t shstrndx)

{

  Elf_Scn *scn = NULL;

  while (result != NULL && (scn = elf_nextscn (elf, scn)) != NULL)

    result = check_section (result, shstrndx, scn, false);

  return valid_p (result);

}

static Dwarf *

scngrp_read (Dwarf *result, Elf *elf, size_t shstrndx, Elf_Scn *scngrp)

{

  GElf_Shdr shdr_mem;

  GElf_Shdr *shdr = gelf_getshdr (scngrp, &shdr_mem);

  if (shdr == NULL)

    {

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      __libdw_seterrno (DWARF_E_INVALID_ELF);

      free (result);

      return NULL;

    }

  if ((shdr->sh_flags & SHF_COMPRESSED) != 0

      && elf_compress (scngrp, 0, 0) < 0)

    {

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      __libdw_seterrno (DWARF_E_COMPRESSED_ERROR);

      free (result);

      return NULL;

    }

  /* SCNGRP is the section descriptor for a section group which might

     contain debug sections.  */

  Elf_Data *data = elf_getdata (scngrp, NULL);

  if (data == NULL)

    {

      /* We cannot read the section content.  Fail!  */

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      free (result);

      return NULL;

    }

  /* The content of the section is a number of 32-bit words which

     represent section indices.  The first word is a flag word.  */

  Elf32_Word *scnidx = (Elf32_Word *) data->d_buf;

  size_t cnt;

  for (cnt = 1; cnt * sizeof (Elf32_Word) <= data->d_size; ++cnt)

    {

      Elf_Scn *scn = elf_getscn (elf, scnidx[cnt]);

      if (scn == NULL)

	{

	  /* A section group refers to a non-existing section.  Should

	     never happen.  */

	  Dwarf_Sig8_Hash_free (&result->sig8_hash);

	  __libdw_seterrno (DWARF_E_INVALID_ELF);

	  free (result);

	  return NULL;

	}

      result = check_section (result, shstrndx, scn, true);

      if (result == NULL)

	break;

    }

  return valid_p (result);

}

Dwarf *

dwarf_begin_elf (Elf *elf, Dwarf_Cmd cmd, Elf_Scn *scngrp)

{

  GElf_Ehdr *ehdr;

  GElf_Ehdr ehdr_mem;

  /* Get the ELF header of the file.  We need various pieces of

     information from it.  */

  ehdr = gelf_getehdr (elf, &ehdr_mem);

  if (ehdr == NULL)

    {

      if (elf_kind (elf) != ELF_K_ELF)

	__libdw_seterrno (DWARF_E_NOELF);

      else

	__libdw_seterrno (DWARF_E_GETEHDR_ERROR);

      return NULL;

    }

  /* Default memory allocation size.  */

  size_t mem_default_size = sysconf (_SC_PAGESIZE) - 4 * sizeof (void *);

  assert (sizeof (struct Dwarf) < mem_default_size);

  /* Allocate the data structure.  */

  Dwarf *result = (Dwarf *) calloc (1, sizeof (Dwarf));

  if (unlikely (result == NULL)

      || unlikely (Dwarf_Sig8_Hash_init (&result->sig8_hash, 11) < 0))

    {

      free (result);

      __libdw_seterrno (DWARF_E_NOMEM);

      return NULL;

    }

  /* Fill in some values.  */

  if ((BYTE_ORDER == LITTLE_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2MSB)

      || (BYTE_ORDER == BIG_ENDIAN && ehdr->e_ident[EI_DATA] == ELFDATA2LSB))

    result->other_byte_order = true;

  result->elf = elf;

  result->alt_fd = -1;

  /* Initialize the memory handling.  Initial blocks are allocated on first

     actual allocation.  */

  result->mem_default_size = mem_default_size;

  result->oom_handler = __libdw_oom;

  if (pthread_rwlock_init(&result->mem_rwl, NULL) != 0)

    {

      free (result);

      __libdw_seterrno (DWARF_E_NOMEM); /* no memory.  */

      return NULL;

    }

  result->mem_stacks = 0;

  result->mem_tails = NULL;

  if (cmd == DWARF_C_READ || cmd == DWARF_C_RDWR)

    {

      /* All sections are recognized by name, so pass the section header

	 string index along to easily get the section names.  */

      size_t shstrndx;

      if (elf_getshdrstrndx (elf, &shstrndx) != 0)

	{

	  Dwarf_Sig8_Hash_free (&result->sig8_hash);

	  __libdw_seterrno (DWARF_E_INVALID_ELF);

	  free (result);

	  return NULL;

	}

      /* If the caller provides a section group we get the DWARF

	 sections only from this setion group.  Otherwise we search

	 for the first section with the required name.  Further

	 sections with the name are ignored.  The DWARF specification

	 does not really say this is allowed.  */

      if (scngrp == NULL)

	return global_read (result, elf, shstrndx);

      else

	return scngrp_read (result, elf, shstrndx, scngrp);

    }

  else if (cmd == DWARF_C_WRITE)

    {

      Dwarf_Sig8_Hash_free (&result->sig8_hash);

      __libdw_seterrno (DWARF_E_UNIMPL);

      free (result);

      return NULL;

    }

  Dwarf_Sig8_Hash_free (&result->sig8_hash);

  __libdw_seterrno (DWARF_E_INVALID_CMD);

  free (result);

  return NULL;

}

INTDEF(dwarf_begin_elf)