/* Find an ELF file for a module from its build ID.

   Copyright (C) 2007-2010, 2014, 2015, 2019 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 "libdwflP.h"

#include <inttypes.h>

#include <fcntl.h>

#include <unistd.h>

#include "system.h"

int

internal_function

__libdwfl_open_by_build_id (Dwfl_Module *mod, bool debug, char **file_name,

			    const size_t id_len, const uint8_t *id)

{

  /* We don't handle very short or really large build-ids.  We need at

     at least 3 and allow for up to 64 (normally ids are 20 long).  */

#define MIN_BUILD_ID_BYTES 3

#define MAX_BUILD_ID_BYTES 64

  if (id_len < MIN_BUILD_ID_BYTES || id_len > MAX_BUILD_ID_BYTES)

    {

    bad_id:

      __libdwfl_seterrno (DWFL_E_WRONG_ID_ELF);

      return -1;

    }

  /* Search debuginfo_path directories' .build-id/ subdirectories.  */

  char id_name[sizeof "/.build-id/" + 1 + MAX_BUILD_ID_BYTES * 2

	       + sizeof ".debug" - 1];

  strcpy (id_name, "/.build-id/");

  int n = snprintf (&id_name[sizeof "/.build-id/" - 1],

		    4, "%02" PRIx8 "/", (uint8_t) id[0]);

  if (n != 3)

    goto bad_id;;

  for (size_t i = 1; i < id_len; ++i)

    {

      n = snprintf (&id_name[sizeof "/.build-id/" - 1 + 3 + (i - 1) * 2],

		    3, "%02" PRIx8, (uint8_t) id[i]);

      if (n != 2)

	goto bad_id;

    }

  if (debug)

    strcpy (&id_name[sizeof "/.build-id/" - 1 + 3 + (id_len - 1) * 2],

	    ".debug");

  const Dwfl_Callbacks *const cb = mod->dwfl->callbacks;

  char *path = strdup ((cb->debuginfo_path ? *cb->debuginfo_path : NULL)

		       ?: DEFAULT_DEBUGINFO_PATH);

  if (path == NULL)

    return -1;

  int fd = -1;

  char *dir;

  char *paths = path;

  while (fd < 0 && (dir = strsep (&paths, ":")) != NULL)

    {

      if (dir[0] == '+' || dir[0] == '-')

	++dir;

      /* Only absolute directory names are useful to us.  */

      if (dir[0] != '/')

	continue;

      size_t dirlen = strlen (dir);

      char *name = malloc (dirlen + sizeof id_name);

      if (unlikely (name == NULL))

	break;

      memcpy (mempcpy (name, dir, dirlen), id_name, sizeof id_name);

      fd = TEMP_FAILURE_RETRY (open (name, O_RDONLY));

      if (fd >= 0)

	{

	  if (*file_name != NULL)

	    free (*file_name);

	  *file_name = realpath (name, NULL);

	  if (*file_name == NULL)

	    {

	      *file_name = name;

	      name = NULL;

	    }

	}

      free (name);

    }

  free (path);

  /* If we simply found nothing, clear errno.  If we had some other error

     with the file, report that.  Possibly this should treat other errors

     like ENOENT too.  But ignoring all errors could mask some that should

     be reported.  */

  if (fd < 0 && errno == ENOENT)

    errno = 0;

  return fd;

}

int

internal_function

__libdwfl_open_mod_by_build_id (Dwfl_Module *mod, bool debug, char **file_name)

{

  /* If *FILE_NAME was primed into the module, leave it there

     as the fallback when we have nothing to offer.  */

  errno = 0;

  if (mod->build_id_len <= 0)

    return -1;

  const size_t id_len = mod->build_id_len;

  const uint8_t *id = mod->build_id_bits;

  return __libdwfl_open_by_build_id (mod, debug, file_name, id_len, id);

}

int

dwfl_build_id_find_elf (Dwfl_Module *mod,

			void **userdata __attribute__ ((unused)),

			const char *modname __attribute__ ((unused)),

			Dwarf_Addr base __attribute__ ((unused)),

			char **file_name, Elf **elfp)

{

  *elfp = NULL;

  if (mod->is_executable

      && mod->dwfl->user_core != NULL

      && mod->dwfl->user_core->executable_for_core != NULL)

    {

      /* When dwfl_core_file_report was called with a non-NULL executable file

	 name this callback will replace the Dwfl_Module main.name with the

	 recorded executable file when MOD was identified as main executable

	 (which then triggers opening and reporting of the executable).  */

      const char *executable = mod->dwfl->user_core->executable_for_core;

      int fd = open (executable, O_RDONLY);

      if (fd >= 0)

	{

	  *file_name = strdup (executable);

	  if (*file_name != NULL)

	    return fd;

	  else

	    close (fd);

	}

    }

  int fd = __libdwfl_open_mod_by_build_id (mod, false, file_name);

  if (fd >= 0)

    {

      Dwfl_Error error = __libdw_open_file (&fd, elfp, true, false);

      if (error != DWFL_E_NOERROR)

	__libdwfl_seterrno (error);

      else if (__libdwfl_find_build_id (mod, false, *elfp) == 2)

	{

	  /* This is a backdoor signal to short-circuit the ID refresh.  */

	  mod->main.valid = true;

	  return fd;

	}

      else

	{

	  /* This file does not contain the ID it should!  */

	  elf_end (*elfp);

	  *elfp = NULL;

	  close (fd);

	  fd = -1;

	}

      free (*file_name);

      *file_name = NULL;

    }

  else

    {

#ifdef ENABLE_LIBDEBUGINFOD

      /* If all else fails and a build-id is available, query the

	 debuginfo-server if enabled.  */

      if (fd < 0 && mod->build_id_len > 0)

	fd = __libdwfl_debuginfod_find_executable (mod->dwfl,

						   mod->build_id_bits,

						   mod->build_id_len);

#endif

    }

  if (fd < 0 && errno == 0 && mod->build_id_len > 0)

    /* Setting this with no file yet loaded is a marker that

       the build ID is authoritative even if we also know a

       putative *FILE_NAME.  */

    mod->main.valid = true;

  return fd;

}

INTDEF (dwfl_build_id_find_elf)