gdb/dwarf2/dwz.c - binutils-gdb - Git at Google

 /* DWARF DWZ handling for GDB.

    Copyright (C) 2003-2021 Free Software Foundation, Inc.

    This file is part of GDB.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    This program 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 a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

 #include "defs.h"
 #include "dwarf2/dwz.h"

 #include "build-id.h"
 #include "debuginfod-support.h"
 #include "dwarf2/read.h"
 #include "dwarf2/sect-names.h"
 #include "filenames.h"
 #include "gdb_bfd.h"
 #include "gdbcore.h"
 #include "gdbsupport/pathstuff.h"
 #include "gdbsupport/scoped_fd.h"

 const char *
 dwz_file::read_string (struct objfile *objfile, LONGEST str_offset)
 {
   str.read (objfile);

   if (str.buffer == NULL)
     error (_("DW_FORM_GNU_strp_alt used without .debug_str "
 	     "section [in module %s]"),
 	   bfd_get_filename (dwz_bfd.get ()));
   if (str_offset >= str.size)
     error (_("DW_FORM_GNU_strp_alt pointing outside of "
 	     ".debug_str section [in module %s]"),
 	   bfd_get_filename (dwz_bfd.get ()));
   gdb_assert (HOST_CHAR_BIT == 8);
   if (str.buffer[str_offset] == '\0')
     return NULL;
   return (const char *) (str.buffer + str_offset);
 }

 /* A helper function to find the sections for a .dwz file.  */

 static void
 locate_dwz_sections (bfd *abfd, asection *sectp, dwz_file *dwz_file)
 {
   /* Note that we only support the standard ELF names, because .dwz
      is ELF-only (at the time of writing).  */
   if (dwarf2_elf_names.abbrev.matches (sectp->name))
     {
       dwz_file->abbrev.s.section = sectp;
       dwz_file->abbrev.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.info.matches (sectp->name))
     {
       dwz_file->info.s.section = sectp;
       dwz_file->info.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.str.matches (sectp->name))
     {
       dwz_file->str.s.section = sectp;
       dwz_file->str.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.line.matches (sectp->name))
     {
       dwz_file->line.s.section = sectp;
       dwz_file->line.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.macro.matches (sectp->name))
     {
       dwz_file->macro.s.section = sectp;
       dwz_file->macro.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.gdb_index.matches (sectp->name))
     {
       dwz_file->gdb_index.s.section = sectp;
       dwz_file->gdb_index.size = bfd_section_size (sectp);
     }
   else if (dwarf2_elf_names.debug_names.matches (sectp->name))
     {
       dwz_file->debug_names.s.section = sectp;
       dwz_file->debug_names.size = bfd_section_size (sectp);
     }
 }

 /* Attempt to find a .dwz file (whose full path is represented by
    FILENAME) in all of the specified debug file directories provided.

    Return the equivalent gdb_bfd_ref_ptr of the .dwz file found, or
    nullptr if it could not find anything.  */

 static gdb_bfd_ref_ptr
 dwz_search_other_debugdirs (std::string &filename, bfd_byte *buildid,
 			    size_t buildid_len)
 {
   /* Let's assume that the path represented by FILENAME has the
      "/.dwz/" subpath in it.  This is what (most) GNU/Linux
      distributions do, anyway.  */
   size_t dwz_pos = filename.find ("/.dwz/");

   if (dwz_pos == std::string::npos)
     return nullptr;

   /* This is an obvious assertion, but it's here more to educate
      future readers of this code that FILENAME at DWZ_POS *must*
      contain a directory separator.  */
   gdb_assert (IS_DIR_SEPARATOR (filename[dwz_pos]));

   gdb_bfd_ref_ptr dwz_bfd;
   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
     = dirnames_to_char_ptr_vec (debug_file_directory.c_str ());

   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
     {
       /* The idea is to iterate over the
 	 debug file directories provided by the user and
 	 replace the hard-coded path in the "filename" by each
 	 debug-file-directory.

 	 For example, suppose that filename is:

 	   /usr/lib/debug/.dwz/foo.dwz

 	 And suppose that we have "$HOME/bar" as the
 	 debug-file-directory.  We would then adjust filename
 	 to look like:

 	   $HOME/bar/.dwz/foo.dwz

 	 which would hopefully allow us to find the alt debug
 	 file.  */
       std::string ddir = debugdir.get ();

       if (ddir.empty ())
 	continue;

       /* Make sure the current debug-file-directory ends with a
 	 directory separator.  This is needed because, if FILENAME
 	 contains something like "/usr/lib/abcde/.dwz/foo.dwz" and
 	 DDIR is "/usr/lib/abc", then could wrongfully skip it
 	 below.  */
       if (!IS_DIR_SEPARATOR (ddir.back ()))
 	ddir += SLASH_STRING;

       /* Check whether the beginning of FILENAME is DDIR.  If it is,
 	 then we are dealing with a file which we already attempted to
 	 open before, so we just skip it and continue processing the
 	 remaining debug file directories.  */
       if (filename.size () > ddir.size ()
 	  && filename.compare (0, ddir.size (), ddir) == 0)
 	continue;

       /* Replace FILENAME's default debug-file-directory with
 	 DDIR.  */
       std::string new_filename = ddir + &filename[dwz_pos + 1];

       dwz_bfd = gdb_bfd_open (new_filename.c_str (), gnutarget);

       if (dwz_bfd == nullptr)
 	continue;

       if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
 	{
 	  dwz_bfd.reset (nullptr);
 	  continue;
 	}

       /* Found it.  */
       break;
     }

   return dwz_bfd;
 }

 /* See dwz.h.  */

 struct dwz_file *
 dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd, bool require)
 {
   bfd_size_type buildid_len_arg;
   size_t buildid_len;
   bfd_byte *buildid;

   if (per_bfd->dwz_file != NULL)
     return per_bfd->dwz_file.get ();

   bfd_set_error (bfd_error_no_error);
   gdb::unique_xmalloc_ptr<char> data
     (bfd_get_alt_debug_link_info (per_bfd->obfd,
 				  &buildid_len_arg, &buildid));
   if (data == NULL)
     {
       if (bfd_get_error () == bfd_error_no_error)
 	{
 	  if (!require)
 	    return nullptr;
 	  error (_("could not read '.gnu_debugaltlink' section"));
 	}
       error (_("could not read '.gnu_debugaltlink' section: %s"),
 	     bfd_errmsg (bfd_get_error ()));
     }

   gdb::unique_xmalloc_ptr<bfd_byte> buildid_holder (buildid);

   buildid_len = (size_t) buildid_len_arg;

   std::string filename = data.get ();

   if (!IS_ABSOLUTE_PATH (filename.c_str ()))
     {
       gdb::unique_xmalloc_ptr<char> abs
 	= gdb_realpath (bfd_get_filename (per_bfd->obfd));

       filename = ldirname (abs.get ()) + SLASH_STRING + filename;
     }

   /* First try the file name given in the section.  If that doesn't
      work, try to use the build-id instead.  */
   gdb_bfd_ref_ptr dwz_bfd (gdb_bfd_open (filename.c_str (), gnutarget));
   if (dwz_bfd != NULL)
     {
       if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
 	dwz_bfd.reset (nullptr);
     }

   if (dwz_bfd == NULL)
     dwz_bfd = build_id_to_debug_bfd (buildid_len, buildid);

   if (dwz_bfd == nullptr)
     {
       /* If the user has provided us with different
 	 debug file directories, we can try them in order.  */
       dwz_bfd = dwz_search_other_debugdirs (filename, buildid, buildid_len);
     }

   if (dwz_bfd == nullptr)
     {
       gdb::unique_xmalloc_ptr<char> alt_filename;
       const char *origname = bfd_get_filename (per_bfd->obfd);

       scoped_fd fd (debuginfod_debuginfo_query (buildid,
 						buildid_len,
 						origname,
 						&alt_filename));

       if (fd.get () >= 0)
 	{
 	  /* File successfully retrieved from server.  */
 	  dwz_bfd = gdb_bfd_open (alt_filename.get (), gnutarget);

 	  if (dwz_bfd == nullptr)
 	    warning (_("File \"%s\" from debuginfod cannot be opened as bfd"),
 		     alt_filename.get ());
 	  else if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
 	    dwz_bfd.reset (nullptr);
 	}
     }

   if (dwz_bfd == NULL)
     error (_("could not find '.gnu_debugaltlink' file for %s"),
 	   bfd_get_filename (per_bfd->obfd));

   std::unique_ptr<struct dwz_file> result
     (new struct dwz_file (std::move (dwz_bfd)));

   for (asection *sec : gdb_bfd_sections (result->dwz_bfd))
     locate_dwz_sections (result->dwz_bfd.get (), sec, result.get ());

   gdb_bfd_record_inclusion (per_bfd->obfd, result->dwz_bfd.get ());
   per_bfd->dwz_file = std::move (result);
   return per_bfd->dwz_file.get ();
 }
	/* DWARF DWZ handling for GDB.

	Copyright (C) 2003-2021 Free Software Foundation, Inc.

	This file is part of GDB.

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 3 of the License, or
	(at your option) any later version.

	This program 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 a copy of the GNU General Public License
	along with this program. If not, see <http://www.gnu.org/licenses/>. */

	#include "defs.h"
	#include "dwarf2/dwz.h"

	#include "build-id.h"
	#include "debuginfod-support.h"
	#include "dwarf2/read.h"
	#include "dwarf2/sect-names.h"
	#include "filenames.h"
	#include "gdb_bfd.h"
	#include "gdbcore.h"
	#include "gdbsupport/pathstuff.h"
	#include "gdbsupport/scoped_fd.h"

	const char *
	dwz_file::read_string (struct objfile *objfile, LONGEST str_offset)
	{
	str.read (objfile);

	if (str.buffer == NULL)
	error (_("DW_FORM_GNU_strp_alt used without .debug_str "
	"section [in module %s]"),
	bfd_get_filename (dwz_bfd.get ()));
	if (str_offset >= str.size)
	error (_("DW_FORM_GNU_strp_alt pointing outside of "
	".debug_str section [in module %s]"),
	bfd_get_filename (dwz_bfd.get ()));
	gdb_assert (HOST_CHAR_BIT == 8);
	if (str.buffer[str_offset] == '\0')
	return NULL;
	return (const char *) (str.buffer + str_offset);
	}

	/* A helper function to find the sections for a .dwz file. */

	static void
	locate_dwz_sections (bfd abfd, asection sectp, dwz_file *dwz_file)
	{
	/* Note that we only support the standard ELF names, because .dwz
	is ELF-only (at the time of writing). */
	if (dwarf2_elf_names.abbrev.matches (sectp->name))
	{
	dwz_file->abbrev.s.section = sectp;
	dwz_file->abbrev.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.info.matches (sectp->name))
	{
	dwz_file->info.s.section = sectp;
	dwz_file->info.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.str.matches (sectp->name))
	{
	dwz_file->str.s.section = sectp;
	dwz_file->str.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.line.matches (sectp->name))
	{
	dwz_file->line.s.section = sectp;
	dwz_file->line.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.macro.matches (sectp->name))
	{
	dwz_file->macro.s.section = sectp;
	dwz_file->macro.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.gdb_index.matches (sectp->name))
	{
	dwz_file->gdb_index.s.section = sectp;
	dwz_file->gdb_index.size = bfd_section_size (sectp);
	}
	else if (dwarf2_elf_names.debug_names.matches (sectp->name))
	{
	dwz_file->debug_names.s.section = sectp;
	dwz_file->debug_names.size = bfd_section_size (sectp);
	}
	}

	/* Attempt to find a .dwz file (whose full path is represented by
	FILENAME) in all of the specified debug file directories provided.

	Return the equivalent gdb_bfd_ref_ptr of the .dwz file found, or
	nullptr if it could not find anything. */

	static gdb_bfd_ref_ptr
	dwz_search_other_debugdirs (std::string &filename, bfd_byte *buildid,
	size_t buildid_len)
	{
	/* Let's assume that the path represented by FILENAME has the
	"/.dwz/" subpath in it. This is what (most) GNU/Linux
	distributions do, anyway. */
	size_t dwz_pos = filename.find ("/.dwz/");

	if (dwz_pos == std::string::npos)
	return nullptr;

	/* This is an obvious assertion, but it's here more to educate
	future readers of this code that FILENAME at DWZ_POS must
	contain a directory separator. */
	gdb_assert (IS_DIR_SEPARATOR (filename[dwz_pos]));

	gdb_bfd_ref_ptr dwz_bfd;
	std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
	= dirnames_to_char_ptr_vec (debug_file_directory.c_str ());

	for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
	{
	/* The idea is to iterate over the
	debug file directories provided by the user and
	replace the hard-coded path in the "filename" by each
	debug-file-directory.

	For example, suppose that filename is:

	/usr/lib/debug/.dwz/foo.dwz

	And suppose that we have "$HOME/bar" as the
	debug-file-directory. We would then adjust filename
	to look like:

	$HOME/bar/.dwz/foo.dwz

	which would hopefully allow us to find the alt debug
	file. */
	std::string ddir = debugdir.get ();

	if (ddir.empty ())
	continue;

	/* Make sure the current debug-file-directory ends with a
	directory separator. This is needed because, if FILENAME
	contains something like "/usr/lib/abcde/.dwz/foo.dwz" and
	DDIR is "/usr/lib/abc", then could wrongfully skip it
	below. */
	if (!IS_DIR_SEPARATOR (ddir.back ()))
	ddir += SLASH_STRING;

	/* Check whether the beginning of FILENAME is DDIR. If it is,
	then we are dealing with a file which we already attempted to
	open before, so we just skip it and continue processing the
	remaining debug file directories. */
	if (filename.size () > ddir.size ()
	&& filename.compare (0, ddir.size (), ddir) == 0)
	continue;

	/* Replace FILENAME's default debug-file-directory with
	DDIR. */
	std::string new_filename = ddir + &filename[dwz_pos + 1];

	dwz_bfd = gdb_bfd_open (new_filename.c_str (), gnutarget);

	if (dwz_bfd == nullptr)
	continue;

	if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
	{
	dwz_bfd.reset (nullptr);
	continue;
	}

	/* Found it. */
	break;
	}

	return dwz_bfd;
	}

	/* See dwz.h. */

	struct dwz_file *
	dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd, bool require)
	{
	bfd_size_type buildid_len_arg;
	size_t buildid_len;
	bfd_byte *buildid;

	if (per_bfd->dwz_file != NULL)
	return per_bfd->dwz_file.get ();

	bfd_set_error (bfd_error_no_error);
	gdb::unique_xmalloc_ptr<char> data
	(bfd_get_alt_debug_link_info (per_bfd->obfd,
	&buildid_len_arg, &buildid));
	if (data == NULL)
	{
	if (bfd_get_error () == bfd_error_no_error)
	{
	if (!require)
	return nullptr;
	error (_("could not read '.gnu_debugaltlink' section"));
	}
	error (_("could not read '.gnu_debugaltlink' section: %s"),
	bfd_errmsg (bfd_get_error ()));
	}

	gdb::unique_xmalloc_ptr<bfd_byte> buildid_holder (buildid);

	buildid_len = (size_t) buildid_len_arg;

	std::string filename = data.get ();

	if (!IS_ABSOLUTE_PATH (filename.c_str ()))
	{
	gdb::unique_xmalloc_ptr<char> abs
	= gdb_realpath (bfd_get_filename (per_bfd->obfd));

	filename = ldirname (abs.get ()) + SLASH_STRING + filename;
	}

	/* First try the file name given in the section. If that doesn't
	work, try to use the build-id instead. */
	gdb_bfd_ref_ptr dwz_bfd (gdb_bfd_open (filename.c_str (), gnutarget));
	if (dwz_bfd != NULL)
	{
	if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
	dwz_bfd.reset (nullptr);
	}

	if (dwz_bfd == NULL)
	dwz_bfd = build_id_to_debug_bfd (buildid_len, buildid);

	if (dwz_bfd == nullptr)
	{
	/* If the user has provided us with different
	debug file directories, we can try them in order. */
	dwz_bfd = dwz_search_other_debugdirs (filename, buildid, buildid_len);
	}

	if (dwz_bfd == nullptr)
	{
	gdb::unique_xmalloc_ptr<char> alt_filename;
	const char *origname = bfd_get_filename (per_bfd->obfd);

	scoped_fd fd (debuginfod_debuginfo_query (buildid,
	buildid_len,
	origname,
	&alt_filename));

	if (fd.get () >= 0)
	{
	/* File successfully retrieved from server. */
	dwz_bfd = gdb_bfd_open (alt_filename.get (), gnutarget);

	if (dwz_bfd == nullptr)
	warning (_("File \"%s\" from debuginfod cannot be opened as bfd"),
	alt_filename.get ());
	else if (!build_id_verify (dwz_bfd.get (), buildid_len, buildid))
	dwz_bfd.reset (nullptr);
	}
	}

	if (dwz_bfd == NULL)
	error (_("could not find '.gnu_debugaltlink' file for %s"),
	bfd_get_filename (per_bfd->obfd));

	std::unique_ptr<struct dwz_file> result
	(new struct dwz_file (std::move (dwz_bfd)));

	for (asection *sec : gdb_bfd_sections (result->dwz_bfd))
	locate_dwz_sections (result->dwz_bfd.get (), sec, result.get ());

	gdb_bfd_record_inclusion (per_bfd->obfd, result->dwz_bfd.get ());
	per_bfd->dwz_file = std::move (result);
	return per_bfd->dwz_file.get ();
	}