path: root/libdwfl/find-debuginfo.c

/* Standard find_debuginfo callback for libdwfl.
   Copyright (C) 2005, 2006, 2007, 2008 Red Hat, Inc.
   This file is part of Red Hat elfutils.

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   it under the terms of the GNU General Public License as published by the
   Free Software Foundation; version 2 of the License.

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   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.

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   this file solely under the GPL without exception.

   Red Hat elfutils is an included package of the Open Invention Network.
   An included package of the Open Invention Network is a package for which
   Open Invention Network licensees cross-license their patents.  No patent
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#include "libdwflP.h"
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include "system.h"


/* Try to open64 [DIR/][SUBDIR/]DEBUGLINK, return file descriptor or -1.
   On success, *DEBUGINFO_FILE_NAME has the malloc'd name of the open file.  */
static int
try_open (const char *dir, const char *subdir, const char *debuglink,
	  char **debuginfo_file_name)
{
  char *fname;
  if (dir == NULL && subdir == NULL)
    {
      fname = strdup (debuglink);
      if (fname == NULL)
	return -1;
    }
  else if ((subdir == NULL ? asprintf (&fname, "%s/%s", dir, debuglink)
	    : dir == NULL ? asprintf (&fname, "%s/%s", subdir, debuglink)
	    : asprintf (&fname, "%s/%s/%s", dir, subdir, debuglink)) < 0)
    return -1;

  int fd = TEMP_FAILURE_RETRY (open64 (fname, O_RDONLY));
  if (fd < 0)
    free (fname);
  else
    *debuginfo_file_name = fname;

  return fd;
}

/* Return true iff the FD's contents CRC matches DEBUGLINK_CRC.  */
static inline bool
check_crc (int fd, GElf_Word debuglink_crc)
{
  uint32_t file_crc;
  return (__libdwfl_crc32_file (fd, &file_crc) == 0
	  && file_crc == debuglink_crc);
}

static bool
validate (struct dwfl_build_id **build_idp, GElf_Addr bias,
	  int fd, bool check, GElf_Word debuglink_crc)
{
  /* If we have a build ID, check only that.  */
  if (BUILD_ID_PTR (*build_idp))
    {
      /* We need to open an Elf handle on the file so we can check its
	 build ID note for validation.
	 XXX: Maybe backdoor the handle into the module data structure
	 since we had to open it early anyway?  */

      Elf * elf = elf_begin (fd, ELF_C_READ_MMAP_PRIVATE, NULL);
      if (unlikely (__libdwfl_find_build_id (build_idp, bias,
					     false, elf) != 2))
	{
	  free (*build_idp);
	  *build_idp = NULL;
	}
      elf_end (elf);

      return *build_idp != NULL;
    }

  return !check || check_crc (fd, debuglink_crc);
}

static int
find_debuginfo_in_path (Dwfl_Module *mod, const char *file_name,
			const char *debuglink_file, GElf_Word debuglink_crc,
			char **debuginfo_file_name)
{
  bool cancheck = debuglink_crc != (GElf_Word) 0;

  const char *file_basename = file_name == NULL ? NULL : basename (file_name);
  if (debuglink_file == NULL)
    {
      if (file_basename == NULL)
	{
	  errno = 0;
	  return -1;
	}

      size_t len = strlen (file_basename);
      char *localname = alloca (len + sizeof ".debug");
      memcpy (localname, file_basename, len);
      memcpy (&localname[len], ".debug", sizeof ".debug");
      debuglink_file = localname;
      cancheck = false;
    }

  /* Look for a file named DEBUGLINK_FILE in the directories
     indicated by the debug directory path setting.  */

  const Dwfl_Callbacks *const cb = mod->dwfl->callbacks;
  char *path = strdupa ((cb->debuginfo_path ? *cb->debuginfo_path : NULL)
			?: DEFAULT_DEBUGINFO_PATH);

  /* A leading - or + in the whole path sets whether to check file CRCs.  */
  bool defcheck = true;
  if (path[0] == '-' || path[0] == '+')
    {
      defcheck = path[0] == '+';
      ++path;
    }

  char *file_dirname = (file_basename == file_name ? NULL
			: strndupa (file_name, file_basename - 1 - file_name));
  char *p;
  while ((p = strsep (&path, ":")) != NULL)
    {
      /* A leading - or + says whether to check file CRCs for this element.  */
      bool check = defcheck;
      if (*p == '+' || *p == '-')
	check = *p++ == '+';
      check = check && cancheck;

      const char *dir, *subdir;
      switch (p[0])
	{
	case '\0':
	  /* An empty entry says to try the main file's directory.  */
	  dir = file_dirname;
	  subdir = NULL;
	  break;
	case '/':
	  /* An absolute path says to look there for a subdirectory
	     named by the main file's absolute directory.
	     This cannot be applied to a relative file name.  */
	  if (file_dirname == NULL || file_dirname[0] != '/')
	    continue;
	  dir = p;
	  subdir = file_dirname + 1;
	  break;
	default:
	  /* A relative path says to try a subdirectory of that name
	     in the main file's directory.  */
	  dir = file_dirname;
	  subdir = p;
	  break;
	}

      char *fname;
      int fd = try_open (dir, subdir, debuglink_file, &fname);
      if (fd < 0)
	switch (errno)
	  {
	  case ENOENT:
	  case ENOTDIR:
	    continue;
	  default:
	    return -1;
	  }

      if (validate (&mod->main.shared->build_id, mod->bias,
		    fd, check, debuglink_crc))
	{
	  *debuginfo_file_name = fname;
	  return fd;
	}
      free (fname);
      close (fd);
    }

  /* No dice.  */
  errno = 0;
  return -1;
}

int
dwfl_standard_find_debuginfo (Dwfl_Module *mod,
			      void **userdata __attribute__ ((unused)),
			      const char *modname __attribute__ ((unused)),
			      GElf_Addr base __attribute__ ((unused)),
			      const char *file_name,
			      const char *debuglink_file,
			      GElf_Word debuglink_crc,
			      char **debuginfo_file_name)
{
  /* First try by build ID if we have one.  If that succeeds or fails
     other than just by finding nothing, that's all we do.  */
  const unsigned char *bits;
  GElf_Addr vaddr;
  if (INTUSE(dwfl_module_build_id) (mod, &bits, &vaddr) > 0)
    {
      int fd = INTUSE(dwfl_build_id_find_debuginfo) (mod,
						     NULL, NULL, 0,
						     NULL, NULL, 0,
						     debuginfo_file_name);
      if (fd >= 0 || errno != 0)
	return fd;
    }

  /* Failing that, search the path by name.  */
  int fd = find_debuginfo_in_path (mod, file_name,
				   debuglink_file, debuglink_crc,
				   debuginfo_file_name);

  if (fd < 0 && errno == 0)
    {
      /* If FILE_NAME is a symlink, the debug file might be associated
	 with the symlink target name instead.  */

      char *canon = canonicalize_file_name (file_name);
      if (canon != NULL && strcmp (file_name, canon))
	fd = find_debuginfo_in_path (mod, canon,
				     debuglink_file, debuglink_crc,
				     debuginfo_file_name);
      free (canon);
    }

  return fd;
}
INTDEF (dwfl_standard_find_debuginfo)