X-Git-Url: https://git.dogcows.com/gitweb?p=chaz%2Ftar;a=blobdiff_plain;f=src%2Fmisc.c;h=e92c8aa830e36fe2fca6cd25aeaf9f107d7b6bac;hp=bae6cfc1ef0a092d83133d763d35512086048ef8;hb=45ccda119355a1087450039a250359c1d0de0d08;hpb=463d99453f51ac4ae875d9bae97418671e7a62bc

diff --git a/src/misc.c b/src/misc.c
index bae6cfc..e92c8aa 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -1,11 +1,11 @@
 /* Miscellaneous functions, not really specific to GNU tar.
 
-   Copyright (C) 1988, 1992, 1994, 1995, 1996, 1997, 1999, 2000, 2001,
-   2003, 2004 Free Software Foundation, Inc.
+   Copyright 1988, 1992, 1994-1997, 1999-2001, 2003-2007, 2009-2010,
+   2012-2014 Free Software Foundation, Inc.
 
    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 2, or (at your option) any later
+   Free Software Foundation; either version 3, or (at your option) any later
    version.
 
    This program is distributed in the hope that it will be useful, but
@@ -14,17 +14,23 @@
    Public License for more details.
 
    You should have received a copy of the GNU General Public License along
-   with this program; if not, write to the Free Software Foundation, Inc.,
-   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+   with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#include "system.h"
-#include "rmt.h"
+#define COMMON_INLINE _GL_EXTERN_INLINE
+#include <system.h>
+#include <rmt.h>
 #include "common.h"
 #include <quotearg.h>
-#include <save-cwd.h>
+#include <xgetcwd.h>
+#include <unlinkdir.h>
+#include <utimens.h>
+
+#ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
+# define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
+#endif
+
+static const char *tar_getcdpath (int);
 
-static void call_arg_fatal (char const *, char const *)
-     __attribute__ ((noreturn));
 
 /* Handling strings.  */
 
@@ -33,11 +39,13 @@ static void call_arg_fatal (char const *, char const *)
 void
 assign_string (char **string, const char *value)
 {
-  if (*string)
-    free (*string);
+  free (*string);
   *string = value ? xstrdup (value) : 0;
 }
 
+#if 0
+/* This function is currently unused; perhaps it should be removed?  */
+
 /* Allocate a copy of the string quoted as in C, and returns that.  If
    the string does not have to be quoted, it returns a null pointer.
    The allocated copy should normally be freed with free() after the
@@ -50,7 +58,7 @@ assign_string (char **string, const char *value)
    when reading directory files.  This means that we can't use
    quotearg, as quotearg is locale-dependent and is meant for human
    consumption.  */
-char *
+static char *
 quote_copy_string (const char *string)
 {
   const char *source = string;
@@ -91,6 +99,7 @@ quote_copy_string (const char *string)
     }
   return 0;
 }
+#endif
 
 /* Takes a quoted C string (like those produced by quote_copy_string)
    and turns it back into the un-quoted original.  This is done in
@@ -98,7 +107,7 @@ quote_copy_string (const char *string)
    completes the unquoting anyway.
 
    This is used for reading the saved directory file in incremental
-   dumps.  It is used for decoding old `N' records (demangling names).
+   dumps.  It is used for decoding old 'N' records (demangling names).
    But also, it is used for decoding file arguments, would they come
    from the shell or a -T file, and for decoding the --exclude
    argument.  */
@@ -123,13 +132,13 @@ unquote_string (char *string)
 	  source++;
 	  break;
 
-	case 'n':
-	  *destination++ = '\n';
+	case 'a':
+	  *destination++ = '\a';
 	  source++;
 	  break;
 
-	case 't':
-	  *destination++ = '\t';
+	case 'b':
+	  *destination++ = '\b';
 	  source++;
 	  break;
 
@@ -138,8 +147,8 @@ unquote_string (char *string)
 	  source++;
 	  break;
 
-	case 'b':
-	  *destination++ = '\b';
+	case 'n':
+	  *destination++ = '\n';
 	  source++;
 	  break;
 
@@ -148,6 +157,16 @@ unquote_string (char *string)
 	  source++;
 	  break;
 
+	case 't':
+	  *destination++ = '\t';
+	  source++;
+	  break;
+
+	case 'v':
+	  *destination++ = '\v';
+	  source++;
+	  break;
+
 	case '?':
 	  *destination++ = 0177;
 	  source++;
@@ -196,6 +215,327 @@ unquote_string (char *string)
     *destination = '\0';
   return result;
 }
+
+/* Zap trailing slashes.  */
+char *
+zap_slashes (char *name)
+{
+  char *q;
+
+  if (!name || *name == 0)
+    return name;
+  q = name + strlen (name) - 1;
+  while (q > name && ISSLASH (*q))
+    *q-- = '\0';
+  return name;
+}
+
+/* Normalize FILE_NAME by removing redundant slashes and "."
+   components, including redundant trailing slashes.
+   Leave ".." alone, as it may be significant in the presence
+   of symlinks and on platforms where "/.." != "/".
+
+   Destructive version: modifies its argument. */
+void
+normalize_filename_x (char *file_name)
+{
+  char *name = file_name + FILE_SYSTEM_PREFIX_LEN (file_name);
+  char *p;
+  char const *q;
+  char c;
+
+  /* Don't squeeze leading "//" to "/", on hosts where they're distinct.  */
+  name += (DOUBLE_SLASH_IS_DISTINCT_ROOT
+	   && ISSLASH (*name) && ISSLASH (name[1]) && ! ISSLASH (name[2]));
+
+  /* Omit redundant leading "." components.  */
+  for (q = p = name; (*p = *q) == '.' && ISSLASH (q[1]); p += !*q)
+    for (q += 2; ISSLASH (*q); q++)
+      continue;
+
+  /* Copy components from Q to P, omitting redundant slashes and
+     internal "."  components.  */
+  while ((*p++ = c = *q++) != '\0')
+    if (ISSLASH (c))
+      while (ISSLASH (q[*q == '.']))
+	q += (*q == '.') + 1;
+
+  /* Omit redundant trailing "." component and slash.  */
+  if (2 < p - name)
+    {
+      p -= p[-2] == '.' && ISSLASH (p[-3]);
+      p -= 2 < p - name && ISSLASH (p[-2]);
+      p[-1] = '\0';
+    }
+}
+
+/* Normalize NAME by removing redundant slashes and "." components,
+   including redundant trailing slashes.
+
+   Return a normalized newly-allocated copy.  */
+
+char *
+normalize_filename (int cdidx, const char *name)
+{
+  char *copy = NULL;
+
+  if (IS_RELATIVE_FILE_NAME (name))
+    {
+      /* Set COPY to the absolute path for this name.
+
+         FIXME: There should be no need to get the absolute file name.
+         tar_getcdpath does not return a true "canonical" path, so
+         this following approach may lead to situations where the same
+         file or directory is processed twice under different absolute
+         paths without that duplication being detected.  Perhaps we
+         should use dev+ino pairs instead of names?  */
+      const char *cdpath = tar_getcdpath (cdidx);
+      size_t copylen;
+      bool need_separator;
+
+      if (!cdpath)
+	call_arg_fatal ("getcwd", ".");
+      copylen = strlen (cdpath);
+      need_separator = ! (DOUBLE_SLASH_IS_DISTINCT_ROOT
+			  && copylen == 2 && ISSLASH (cdpath[1]));
+      copy = xmalloc (copylen + need_separator + strlen (name) + 1);
+      strcpy (copy, cdpath);
+      copy[copylen] = DIRECTORY_SEPARATOR;
+      strcpy (copy + copylen + need_separator, name);
+    }
+
+  if (!copy)
+    copy = xstrdup (name);
+  normalize_filename_x (copy);
+  return copy;
+}
+
+
+void
+replace_prefix (char **pname, const char *samp, size_t slen,
+		const char *repl, size_t rlen)
+{
+  char *name = *pname;
+  size_t nlen = strlen (name);
+  if (nlen > slen && memcmp (name, samp, slen) == 0 && ISSLASH (name[slen]))
+    {
+      if (rlen > slen)
+	{
+	  name = xrealloc (name, nlen - slen + rlen + 1);
+	  *pname = name;
+	}
+      memmove (name + rlen, name + slen, nlen - slen + 1);
+      memcpy (name, repl, rlen);
+    }
+}
+
+
+/* Handling numbers.  */
+
+/* Convert VALUE, which is converted from a system integer type whose
+   minimum value is MINVAL and maximum MINVAL, to an decimal
+   integer string.  Use the storage in BUF and return a pointer to the
+   converted string.  If VALUE is converted from a negative integer in
+   the range MINVAL .. -1, represent it with a string representation
+   of the negative integer, using leading '-'.  */
+#if ! (INTMAX_MAX <= UINTMAX_MAX / 2)
+# error "sysinttostr: uintmax_t cannot represent all intmax_t values"
+#endif
+char *
+sysinttostr (uintmax_t value, intmax_t minval, uintmax_t maxval,
+	     char buf[SYSINT_BUFSIZE])
+{
+  if (value <= maxval)
+    return umaxtostr (value, buf);
+  else
+    {
+      intmax_t i = value - minval;
+      return imaxtostr (i + minval, buf);
+    }
+}
+
+/* Convert a prefix of the string ARG to a system integer type whose
+   minimum value is MINVAL and maximum MAXVAL.  If MINVAL is negative,
+   negative integers MINVAL .. -1 are assumed to be represented using
+   leading '-' in the usual way.  If the represented value exceeds
+   INTMAX_MAX, return a negative integer V such that (uintmax_t) V
+   yields the represented value.  If ARGLIM is nonnull, store into
+   *ARGLIM a pointer to the first character after the prefix.
+
+   This is the inverse of sysinttostr.
+
+   On a normal return, set errno = 0.
+   On conversion error, return 0 and set errno = EINVAL.
+   On overflow, return an extreme value and set errno = ERANGE.  */
+#if ! (INTMAX_MAX <= UINTMAX_MAX)
+# error "strtosysint: nonnegative intmax_t does not fit in uintmax_t"
+#endif
+intmax_t
+strtosysint (char const *arg, char **arglim, intmax_t minval, uintmax_t maxval)
+{
+  errno = 0;
+  if (maxval <= INTMAX_MAX)
+    {
+      if (ISDIGIT (arg[*arg == '-']))
+	{
+	  intmax_t i = strtoimax (arg, arglim, 10);
+	  intmax_t imaxval = maxval;
+	  if (minval <= i && i <= imaxval)
+	    return i;
+	  errno = ERANGE;
+	  return i < minval ? minval : maxval;
+	}
+    }
+  else
+    {
+      if (ISDIGIT (*arg))
+	{
+	  uintmax_t i = strtoumax (arg, arglim, 10);
+	  if (i <= maxval)
+	    return represent_uintmax (i);
+	  errno = ERANGE;
+	  return maxval;
+	}
+    }
+
+  errno = EINVAL;
+  return 0;
+}
+
+/* Output fraction and trailing digits appropriate for a nanoseconds
+   count equal to NS, but don't output unnecessary '.' or trailing
+   zeros.  */
+
+void
+code_ns_fraction (int ns, char *p)
+{
+  if (ns == 0)
+    *p = '\0';
+  else
+    {
+      int i = 9;
+      *p++ = '.';
+
+      while (ns % 10 == 0)
+	{
+	  ns /= 10;
+	  i--;
+	}
+
+      p[i] = '\0';
+
+      for (;;)
+	{
+	  p[--i] = '0' + ns % 10;
+	  if (i == 0)
+	    break;
+	  ns /= 10;
+	}
+    }
+}
+
+char const *
+code_timespec (struct timespec t, char sbuf[TIMESPEC_STRSIZE_BOUND])
+{
+  time_t s = t.tv_sec;
+  int ns = t.tv_nsec;
+  char *np;
+  bool negative = s < 0;
+
+  /* ignore invalid values of ns */
+  if (BILLION <= ns || ns < 0)
+    ns = 0;
+
+  if (negative && ns != 0)
+    {
+      s++;
+      ns = BILLION - ns;
+    }
+
+  np = umaxtostr (negative ? - (uintmax_t) s : (uintmax_t) s, sbuf + 1);
+  if (negative)
+    *--np = '-';
+  code_ns_fraction (ns, sbuf + UINTMAX_STRSIZE_BOUND);
+  return np;
+}
+
+struct timespec
+decode_timespec (char const *arg, char **arg_lim, bool parse_fraction)
+{
+  time_t s = TYPE_MINIMUM (time_t);
+  int ns = -1;
+  char const *p = arg;
+  bool negative = *arg == '-';
+  struct timespec r;
+
+  if (! ISDIGIT (arg[negative]))
+    errno = EINVAL;
+  else
+    {
+      errno = 0;
+
+      if (negative)
+	{
+	  intmax_t i = strtoimax (arg, arg_lim, 10);
+	  if (TYPE_SIGNED (time_t) ? TYPE_MINIMUM (time_t) <= i : 0 <= i)
+	    s = i;
+	  else
+	    errno = ERANGE;
+	}
+      else
+	{
+	  uintmax_t i = strtoumax (arg, arg_lim, 10);
+	  if (i <= TYPE_MAXIMUM (time_t))
+	    s = i;
+	  else
+	    errno = ERANGE;
+	}
+
+      p = *arg_lim;
+      ns = 0;
+
+      if (parse_fraction && *p == '.')
+	{
+	  int digits = 0;
+	  bool trailing_nonzero = false;
+
+	  while (ISDIGIT (*++p))
+	    if (digits < LOG10_BILLION)
+	      digits++, ns = 10 * ns + (*p - '0');
+	    else
+	      trailing_nonzero |= *p != '0';
+
+	  while (digits < LOG10_BILLION)
+	    digits++, ns *= 10;
+
+	  if (negative)
+	    {
+	      /* Convert "-1.10000000000001" to s == -2, ns == 89999999.
+		 I.e., truncate time stamps towards minus infinity while
+		 converting them to internal form.  */
+	      ns += trailing_nonzero;
+	      if (ns != 0)
+		{
+		  if (s == TYPE_MINIMUM (time_t))
+		    ns = -1;
+		  else
+		    {
+		      s--;
+		      ns = BILLION - ns;
+		    }
+		}
+	    }
+	}
+
+      if (errno == ERANGE)
+	ns = -1;
+    }
+
+  *arg_lim = (char *) p;
+  r.tv_sec = s;
+  r.tv_nsec = ns;
+  return r;
+}
 
 /* File handling.  */
 
@@ -204,17 +544,17 @@ static char *before_backup_name;
 static char *after_backup_name;
 
 /* Return 1 if FILE_NAME is obviously "." or "/".  */
-static bool
+bool
 must_be_dot_or_slash (char const *file_name)
 {
-  file_name += FILESYSTEM_PREFIX_LEN (file_name);
+  file_name += FILE_SYSTEM_PREFIX_LEN (file_name);
 
   if (ISSLASH (file_name[0]))
     {
       for (;;)
 	if (ISSLASH (file_name[1]))
 	  file_name++;
-	else if (file_name[1] == '.' 
+	else if (file_name[1] == '.'
                  && ISSLASH (file_name[2 + (file_name[2] == '.')]))
 	  file_name += 2 + (file_name[2] == '.');
 	else
@@ -245,10 +585,10 @@ safer_rmdir (const char *file_name)
       return -1;
     }
 
-  return rmdir (file_name);
+  return unlinkat (chdir_fd, file_name, AT_REMOVEDIR);
 }
 
-/* Remove FILE_NAME, returning 1 on success.  If FILE_NAME is a directory, 
+/* Remove FILE_NAME, returning 1 on success.  If FILE_NAME is a directory,
    then if OPTION is RECURSIVE_REMOVE_OPTION is set remove FILE_NAME
    recursively; otherwise, remove it only if it is empty.  If FILE_NAME is
    a directory that cannot be removed (e.g., because it is nonempty)
@@ -258,11 +598,14 @@ safer_rmdir (const char *file_name)
 int
 remove_any_file (const char *file_name, enum remove_option option)
 {
-  /* Try unlink first if we are not root, as this saves us a system
-     call in the common case where we're removing a non-directory.  */
-  if (! we_are_root)
+  /* Try unlink first if we cannot unlink directories, as this saves
+     us a system call in the common case where we're removing a
+     non-directory.  */
+  bool try_unlink_first = cannot_unlink_dir ();
+
+  if (try_unlink_first)
     {
-      if (unlink (file_name) == 0)
+      if (unlinkat (chdir_fd, file_name, 0) == 0)
 	return 1;
 
       /* POSIX 1003.1-2001 requires EPERM when attempting to unlink a
@@ -278,7 +621,7 @@ remove_any_file (const char *file_name, enum remove_option option)
   switch (errno)
     {
     case ENOTDIR:
-      return we_are_root && unlink (file_name) == 0;
+      return !try_unlink_first && unlinkat (chdir_fd, file_name, 0) == 0;
 
     case 0:
     case EEXIST:
@@ -295,7 +638,7 @@ remove_any_file (const char *file_name, enum remove_option option)
 
 	case RECURSIVE_REMOVE_OPTION:
 	  {
-	    char *directory = savedir (file_name);
+	    char *directory = tar_savedir (file_name, 0);
 	    char const *entry;
 	    size_t entrylen;
 
@@ -307,7 +650,8 @@ remove_any_file (const char *file_name, enum remove_option option)
 		 entry += entrylen + 1)
 	      {
 		char *file_name_buffer = new_name (file_name, entry);
-		int r = remove_any_file (file_name_buffer, 1);
+		int r = remove_any_file (file_name_buffer,
+                                         RECURSIVE_REMOVE_OPTION);
 		int e = errno;
 		free (file_name_buffer);
 
@@ -336,16 +680,25 @@ remove_any_file (const char *file_name, enum remove_option option)
    so, we do not have to backup block or character devices, nor remote
    entities.  */
 bool
-maybe_backup_file (const char *file_name, int this_is_the_archive)
+maybe_backup_file (const char *file_name, bool this_is_the_archive)
 {
   struct stat file_stat;
 
+  assign_string (&before_backup_name, file_name);
+
+  /* A run situation may exist between Emacs or other GNU programs trying to
+     make a backup for the same file simultaneously.  If theoretically
+     possible, real problems are unlikely.  Doing any better would require a
+     convention, GNU-wide, for all programs doing backups.  */
+
+  assign_string (&after_backup_name, 0);
+
   /* Check if we really need to backup the file.  */
 
   if (this_is_the_archive && _remdev (file_name))
     return true;
 
-  if (stat (file_name, &file_stat))
+  if (deref_stat (file_name, &file_stat) != 0)
     {
       if (errno == ENOENT)
 	return true;
@@ -361,19 +714,12 @@ maybe_backup_file (const char *file_name, int this_is_the_archive)
       && (S_ISBLK (file_stat.st_mode) || S_ISCHR (file_stat.st_mode)))
     return true;
 
-  assign_string (&before_backup_name, file_name);
-
-  /* A run situation may exist between Emacs or other GNU programs trying to
-     make a backup for the same file simultaneously.  If theoretically
-     possible, real problems are unlikely.  Doing any better would require a
-     convention, GNU-wide, for all programs doing backups.  */
-
-  assign_string (&after_backup_name, 0);
   after_backup_name = find_backup_file_name (file_name, backup_type);
   if (! after_backup_name)
     xalloc_die ();
 
-  if (rename (before_backup_name, after_backup_name) == 0)
+  if (renameat (chdir_fd, before_backup_name, chdir_fd, after_backup_name)
+      == 0)
     {
       if (verbose_option)
 	fprintf (stdlis, _("Renaming %s to %s\n"),
@@ -400,7 +746,8 @@ undo_last_backup (void)
 {
   if (after_backup_name)
     {
-      if (rename (after_backup_name, before_backup_name) != 0)
+      if (renameat (chdir_fd, after_backup_name, chdir_fd, before_backup_name)
+	  != 0)
 	{
 	  int e = errno;
 	  ERROR ((0, e, _("%s: Cannot rename to %s"),
@@ -415,44 +762,142 @@ undo_last_backup (void)
     }
 }
 
-/* Depending on DEREF, apply either stat or lstat to (NAME, BUF).  */
+/* Apply either stat or lstat to (NAME, BUF), depending on the
+   presence of the --dereference option.  NAME is relative to the
+   most-recent argument to chdir_do.  */
+int
+deref_stat (char const *name, struct stat *buf)
+{
+  return fstatat (chdir_fd, name, buf, fstatat_flags);
+}
+
+/* Read from FD into the buffer BUF with COUNT bytes.  Attempt to fill
+   BUF.  Wait until input is available; this matters because files are
+   opened O_NONBLOCK for security reasons, and on some file systems
+   this can cause read to fail with errno == EAGAIN.  Return the
+   actual number of bytes read, zero for EOF, or
+   SAFE_READ_ERROR upon error.  */
+size_t
+blocking_read (int fd, void *buf, size_t count)
+{
+  size_t bytes = safe_read (fd, buf, count);
+
+#if defined F_SETFL && O_NONBLOCK
+  if (bytes == SAFE_READ_ERROR && errno == EAGAIN)
+    {
+      int flags = fcntl (fd, F_GETFL);
+      if (0 <= flags && flags & O_NONBLOCK
+	  && fcntl (fd, F_SETFL, flags & ~O_NONBLOCK) != -1)
+	bytes = safe_read (fd, buf, count);
+    }
+#endif
+
+  return bytes;
+}
+
+/* Write to FD from the buffer BUF with COUNT bytes.  Do a full write.
+   Wait until an output buffer is available; this matters because
+   files are opened O_NONBLOCK for security reasons, and on some file
+   systems this can cause write to fail with errno == EAGAIN.  Return
+   the actual number of bytes written, setting errno if that is less
+   than COUNT.  */
+size_t
+blocking_write (int fd, void const *buf, size_t count)
+{
+  size_t bytes = full_write (fd, buf, count);
+
+#if defined F_SETFL && O_NONBLOCK
+  if (bytes < count && errno == EAGAIN)
+    {
+      int flags = fcntl (fd, F_GETFL);
+      if (0 <= flags && flags & O_NONBLOCK
+	  && fcntl (fd, F_SETFL, flags & ~O_NONBLOCK) != -1)
+	{
+	  char const *buffer = buf;
+	  bytes += full_write (fd, buffer + bytes, count - bytes);
+	}
+    }
+#endif
+
+  return bytes;
+}
+
+/* Set FD's (i.e., assuming the working directory is PARENTFD, FILE's)
+   access time to ATIME.  */
 int
-deref_stat (bool deref, char const *name, struct stat *buf)
+set_file_atime (int fd, int parentfd, char const *file, struct timespec atime)
 {
-  return deref ? stat (name, buf) : lstat (name, buf);
+  struct timespec ts[2];
+  ts[0] = atime;
+  ts[1].tv_nsec = UTIME_OMIT;
+  return fdutimensat (fd, parentfd, file, ts, fstatat_flags);
 }
 
 /* A description of a working directory.  */
 struct wd
 {
+  /* The directory's name.  */
   char const *name;
-  int saved;
-  struct saved_cwd saved_cwd;
+  /* "Absolute" path representing this directory; in the contrast to
+     the real absolute pathname, it can contain /../ components (see
+     normalize_filename_x for the reason of it).  It is NULL if the
+     absolute path could not be determined.  */
+  char *abspath;
+  /* If nonzero, the file descriptor of the directory, or AT_FDCWD if
+     the working directory.  If zero, the directory needs to be opened
+     to be used.  */
+  int fd;
 };
 
 /* A vector of chdir targets.  wd[0] is the initial working directory.  */
 static struct wd *wd;
 
 /* The number of working directories in the vector.  */
-static size_t wds;
+static size_t wd_count;
 
 /* The allocated size of the vector.  */
 static size_t wd_alloc;
 
+/* The maximum number of chdir targets with open directories.
+   Don't make it too large, as many operating systems have a small
+   limit on the number of open file descriptors.  Also, the current
+   implementation does not scale well.  */
+enum { CHDIR_CACHE_SIZE = 16 };
+
+/* Indexes into WD of chdir targets with open file descriptors, sorted
+   most-recently used first.  Zero indexes are unused.  */
+static int wdcache[CHDIR_CACHE_SIZE];
+
+/* Number of nonzero entries in WDCACHE.  */
+static size_t wdcache_count;
+
+int
+chdir_count (void)
+{
+  if (wd_count == 0)
+    return wd_count;
+  return wd_count - 1;
+}
+
 /* DIR is the operand of a -C option; add it to vector of chdir targets,
    and return the index of its location.  */
 int
 chdir_arg (char const *dir)
 {
-  if (wds == wd_alloc)
+  char *absdir;
+
+  if (wd_count == wd_alloc)
     {
-      wd_alloc = 2 * (wd_alloc + 1);
-      wd = xrealloc (wd, sizeof *wd * wd_alloc);
-      if (! wds)
+      if (wd_alloc == 0)
+	wd_alloc = 2;
+      wd = x2nrealloc (wd, &wd_alloc, sizeof *wd);
+
+      if (! wd_count)
 	{
-	  wd[wds].name = ".";
-	  wd[wds].saved = 0;
-	  wds++;
+	  wd[wd_count].name = ".";
+	  wd[wd_count].abspath = xgetcwd ();
+	  wd[wd_count].fd = AT_FDCWD;
+	  wd_count++;
 	}
     }
 
@@ -464,137 +909,124 @@ chdir_arg (char const *dir)
 	for (dir += 2;  ISSLASH (*dir);  dir++)
 	  continue;
       if (! dir[dir[0] == '.'])
-	return wds - 1;
+	return wd_count - 1;
     }
 
-  wd[wds].name = dir;
-  wd[wds].saved = 0;
-  return wds++;
+
+  /* If the given name is absolute, use it to represent this directory;
+     otherwise, construct a name based on the previous -C option.  */
+  if (IS_ABSOLUTE_FILE_NAME (dir))
+    absdir = xstrdup (dir);
+  else if (wd[wd_count - 1].abspath)
+    {
+      namebuf_t nbuf = namebuf_create (wd[wd_count - 1].abspath);
+      namebuf_add_dir (nbuf, dir);
+      absdir = namebuf_finish (nbuf);
+    }
+  else
+    absdir = 0;
+
+  wd[wd_count].name = dir;
+  wd[wd_count].abspath = absdir;
+  wd[wd_count].fd = 0;
+  return wd_count++;
 }
 
-/* Change to directory I.  If I is 0, change to the initial working
-   directory; otherwise, I must be a value returned by chdir_arg.  */
+/* Index of current directory.  */
+int chdir_current;
+
+/* Value suitable for use as the first argument to openat, and in
+   similar locations for fstatat, etc.  This is an open file
+   descriptor, or AT_FDCWD if the working directory is current.  It is
+   valid until the next invocation of chdir_do.  */
+int chdir_fd = AT_FDCWD;
+
+/* Change to directory I, in a virtual way.  This does not actually
+   invoke chdir; it merely sets chdir_fd to an int suitable as the
+   first argument for openat, etc.  If I is 0, change to the initial
+   working directory; otherwise, I must be a value returned by
+   chdir_arg.  */
 void
 chdir_do (int i)
 {
-  static int previous;
-
-  if (previous != i)
+  if (chdir_current != i)
     {
-      struct wd *prev = &wd[previous];
       struct wd *curr = &wd[i];
+      int fd = curr->fd;
 
-      if (! prev->saved)
+      if (! fd)
 	{
-	  prev->saved = 1;
-	  if (save_cwd (&prev->saved_cwd) != 0)
-	    FATAL_ERROR ((0, 0, _("Cannot save working directory")));
+	  if (! IS_ABSOLUTE_FILE_NAME (curr->name))
+	    chdir_do (i - 1);
+	  fd = openat (chdir_fd, curr->name,
+		       open_searchdir_flags & ~ O_NOFOLLOW);
+	  if (fd < 0)
+	    open_fatal (curr->name);
+
+	  curr->fd = fd;
+
+	  /* Add I to the cache, tossing out the lowest-ranking entry if the
+	     cache is full.  */
+	  if (wdcache_count < CHDIR_CACHE_SIZE)
+	    wdcache[wdcache_count++] = i;
+	  else
+	    {
+	      struct wd *stale = &wd[wdcache[CHDIR_CACHE_SIZE - 1]];
+	      if (close (stale->fd) != 0)
+		close_diag (stale->name);
+	      stale->fd = 0;
+	      wdcache[CHDIR_CACHE_SIZE - 1] = i;
+	    }
 	}
 
-      if (curr->saved)
-	{
-	  if (restore_cwd (&curr->saved_cwd))
-	    FATAL_ERROR ((0, 0, _("Cannot change working directory")));
-	}
-      else
+      if (0 < fd)
 	{
-	  if (i && ! ISSLASH (curr->name[0]))
-	    chdir_do (i - 1);
-	  if (chdir (curr->name) != 0)
-	    chdir_fatal (curr->name);
+	  /* Move the i value to the front of the cache.  This is
+	     O(CHDIR_CACHE_SIZE), but the cache is small.  */
+	  size_t ci;
+	  int prev = wdcache[0];
+	  for (ci = 1; prev != i; ci++)
+	    {
+	      int cur = wdcache[ci];
+	      wdcache[ci] = prev;
+	      if (cur == i)
+		break;
+	      prev = cur;
+	    }
+	  wdcache[0] = i;
 	}
 
-      previous = i;
+      chdir_current = i;
+      chdir_fd = fd;
     }
 }
 
-/* Decode MODE from its binary form in a stat structure, and encode it
-   into a 9-byte string STRING, terminated with a NUL.  */
-
-void
-decode_mode (mode_t mode, char *string)
-{
-  *string++ = mode & S_IRUSR ? 'r' : '-';
-  *string++ = mode & S_IWUSR ? 'w' : '-';
-  *string++ = (mode & S_ISUID
-	       ? (mode & S_IXUSR ? 's' : 'S')
-	       : (mode & S_IXUSR ? 'x' : '-'));
-  *string++ = mode & S_IRGRP ? 'r' : '-';
-  *string++ = mode & S_IWGRP ? 'w' : '-';
-  *string++ = (mode & S_ISGID
-	       ? (mode & S_IXGRP ? 's' : 'S')
-	       : (mode & S_IXGRP ? 'x' : '-'));
-  *string++ = mode & S_IROTH ? 'r' : '-';
-  *string++ = mode & S_IWOTH ? 'w' : '-';
-  *string++ = (mode & S_ISVTX
-	       ? (mode & S_IXOTH ? 't' : 'T')
-	       : (mode & S_IXOTH ? 'x' : '-'));
-  *string = '\0';
-}
-
-/* Report an error associated with the system call CALL and the
-   optional name NAME.  */
-static void
-call_arg_error (char const *call, char const *name)
+const char *
+tar_dirname (void)
 {
-  int e = errno;
-  ERROR ((0, e, _("%s: Cannot %s"), quotearg_colon (name), call));
+  return wd[chdir_current].name;
 }
 
-/* Report a fatal error associated with the system call CALL and
-   the optional file name NAME.  */
-static void
-call_arg_fatal (char const *call, char const *name)
-{
-  int e = errno;
-  FATAL_ERROR ((0, e, _("%s: Cannot %s"), quotearg_colon (name),  call));
-}
+/* Return the absolute path that represents the working
+   directory referenced by IDX.
 
-/* Report a warning associated with the system call CALL and
-   the optional file name NAME.  */
-static void
-call_arg_warn (char const *call, char const *name)
-{
-  int e = errno;
-  WARN ((0, e, _("%s: Warning: Cannot %s"), quotearg_colon (name), call));
-}
-
-void
-chdir_fatal (char const *name)
-{
-  call_arg_fatal ("chdir", name);
-}
-
-void
-chmod_error_details (char const *name, mode_t mode)
-{
-  int e = errno;
-  char buf[10];
-  decode_mode (mode, buf);
-  ERROR ((0, e, _("%s: Cannot change mode to %s"),
-	  quotearg_colon (name), buf));
-}
-
-void
-chown_error_details (char const *name, uid_t uid, gid_t gid)
+   If wd is empty, then there were no -C options given, and
+   chdir_args() has never been called, so we simply return the
+   process's actual cwd.  (Note that in this case IDX is ignored,
+   since it should always be 0.) */
+static const char *
+tar_getcdpath (int idx)
 {
-  int e = errno;
-  ERROR ((0, e, _("%s: Cannot change ownership to uid %lu, gid %lu"),
-	  quotearg_colon (name), (unsigned long) uid, (unsigned long) gid));
-}
-
-void
-close_error (char const *name)
-{
-  call_arg_error ("close", name);
-}
-
-void
-close_warn (char const *name)
-{
-  call_arg_warn ("close", name);
+  if (!wd)
+    {
+      static char *cwd;
+      if (!cwd)
+	cwd = xgetcwd ();
+      return cwd;
+    }
+  return wd[idx].abspath;
 }
-
+
 void
 close_diag (char const *name)
 {
@@ -604,56 +1036,6 @@ close_diag (char const *name)
     close_error (name);
 }
 
-void
-exec_fatal (char const *name)
-{
-  call_arg_fatal ("exec", name);
-}
-
-void
-link_error (char const *target, char const *source)
-{
-  int e = errno;
-  ERROR ((0, e, _("%s: Cannot hard link to %s"),
-	  quotearg_colon (source), quote_n (1, target)));
-}
-
-void
-mkdir_error (char const *name)
-{
-  call_arg_error ("mkdir", name);
-}
-
-void
-mkfifo_error (char const *name)
-{
-  call_arg_error ("mkfifo", name);
-}
-
-void
-mknod_error (char const *name)
-{
-  call_arg_error ("mknod", name);
-}
-
-void
-open_error (char const *name)
-{
-  call_arg_error ("open", name);
-}
-
-void
-open_fatal (char const *name)
-{
-  call_arg_fatal ("open", name);
-}
-
-void
-open_warn (char const *name)
-{
-  call_arg_warn ("open", name);
-}
-
 void
 open_diag (char const *name)
 {
@@ -663,38 +1045,6 @@ open_diag (char const *name)
     open_error (name);
 }
 
-void
-read_error (char const *name)
-{
-  call_arg_error ("read", name);
-}
-
-void
-read_error_details (char const *name, off_t offset, size_t size)
-{
-  char buf[UINTMAX_STRSIZE_BOUND];
-  int e = errno;
-  ERROR ((0, e,
-	  ngettext ("%s: Read error at byte %s, reading %lu byte",
-		    "%s: Read error at byte %s, reading %lu bytes",
-		    size),
-	  quotearg_colon (name), STRINGIFY_BIGINT (offset, buf),
-	  (unsigned long) size));
-}
-
-void
-read_warn_details (char const *name, off_t offset, size_t size)
-{
-  char buf[UINTMAX_STRSIZE_BOUND];
-  int e = errno;
-  WARN ((0, e,
-	 ngettext ("%s: Warning: Read error at byte %s, reading %lu byte",
-		   "%s: Warning: Read error at byte %s, reading %lu bytes",
-		   size),
-	 quotearg_colon (name), STRINGIFY_BIGINT (offset, buf),
-	 (unsigned long) size));
-}
-
 void
 read_diag_details (char const *name, off_t offset, size_t size)
 {
@@ -704,37 +1054,6 @@ read_diag_details (char const *name, off_t offset, size_t size)
     read_error_details (name, offset, size);
 }
 
-void
-read_fatal (char const *name)
-{
-  call_arg_fatal ("read", name);
-}
-
-void
-read_fatal_details (char const *name, off_t offset, size_t size)
-{
-  char buf[UINTMAX_STRSIZE_BOUND];
-  int e = errno;
-  FATAL_ERROR ((0, e,
-		ngettext ("%s: Read error at byte %s, reading %lu byte",
-			  "%s: Read error at byte %s, reading %lu bytes",
-			  size),
-		quotearg_colon (name), STRINGIFY_BIGINT (offset, buf),
-		(unsigned long) size));
-}
-
-void
-readlink_error (char const *name)
-{
-  call_arg_error ("readlink", name);
-}
-
-void
-readlink_warn (char const *name)
-{
-  call_arg_warn ("readlink", name);
-}
-
 void
 readlink_diag (char const *name)
 {
@@ -744,18 +1063,6 @@ readlink_diag (char const *name)
     readlink_error (name);
 }
 
-void
-savedir_error (char const *name)
-{
-  call_arg_error ("savedir", name);
-}
-
-void
-savedir_warn (char const *name)
-{
-  call_arg_warn ("savedir", name);
-}
-
 void
 savedir_diag (char const *name)
 {
@@ -765,38 +1072,6 @@ savedir_diag (char const *name)
     savedir_error (name);
 }
 
-void
-seek_error (char const *name)
-{
-  call_arg_error ("seek", name);
-}
-
-void
-seek_error_details (char const *name, off_t offset)
-{
-  char buf[UINTMAX_STRSIZE_BOUND];
-  int e = errno;
-  ERROR ((0, e, _("%s: Cannot seek to %s"),
-	  quotearg_colon (name),
-	  STRINGIFY_BIGINT (offset, buf)));
-}
-
-void
-seek_warn (char const *name)
-{
-  call_arg_warn ("seek", name);
-}
-
-void
-seek_warn_details (char const *name, off_t offset)
-{
-  char buf[UINTMAX_STRSIZE_BOUND];
-  int e = errno;
-  WARN ((0, e, _("%s: Warning: Cannot seek to %s"),
-	 quotearg_colon (name),
-	 STRINGIFY_BIGINT (offset, buf)));
-}
-
 void
 seek_diag_details (char const *name, off_t offset)
 {
@@ -806,26 +1081,6 @@ seek_diag_details (char const *name, off_t offset)
     seek_error_details (name, offset);
 }
 
-void
-symlink_error (char const *contents, char const *name)
-{
-  int e = errno;
-  ERROR ((0, e, _("%s: Cannot create symlink to %s"),
-	  quotearg_colon (name), quote_n (1, contents)));
-}
-
-void
-stat_error (char const *name)
-{
-  call_arg_error ("stat", name);
-}
-
-void
-stat_warn (char const *name)
-{
-  call_arg_warn ("stat", name);
-}
-
 void
 stat_diag (char const *name)
 {
@@ -836,98 +1091,159 @@ stat_diag (char const *name)
 }
 
 void
-truncate_error (char const *name)
+file_removed_diag (const char *name, bool top_level,
+		   void (*diagfn) (char const *name))
 {
-  call_arg_error ("truncate", name);
+  if (!top_level && errno == ENOENT)
+    {
+      WARNOPT (WARN_FILE_REMOVED,
+	       (0, 0, _("%s: File removed before we read it"),
+		quotearg_colon (name)));
+      set_exit_status (TAREXIT_DIFFERS);
+    }
+  else
+    diagfn (name);
 }
 
 void
-truncate_warn (char const *name)
+write_fatal_details (char const *name, ssize_t status, size_t size)
 {
-  call_arg_warn ("truncate", name);
+  write_error_details (name, status, size);
+  fatal_exit ();
 }
 
-void
-unlink_error (char const *name)
+/* Fork, aborting if unsuccessful.  */
+pid_t
+xfork (void)
 {
-  call_arg_error ("unlink", name);
+  pid_t p = fork ();
+  if (p == (pid_t) -1)
+    call_arg_fatal ("fork", _("child process"));
+  return p;
 }
 
+/* Create a pipe, aborting if unsuccessful.  */
 void
-utime_error (char const *name)
+xpipe (int fd[2])
 {
-  call_arg_error ("utime", name);
+  if (pipe (fd) < 0)
+    call_arg_fatal ("pipe", _("interprocess channel"));
 }
 
-void
-waitpid_error (char const *name)
+/* Return PTR, aligned upward to the next multiple of ALIGNMENT.
+   ALIGNMENT must be nonzero.  The caller must arrange for ((char *)
+   PTR) through ((char *) PTR + ALIGNMENT - 1) to be addressable
+   locations.  */
+
+static inline void *
+ptr_align (void *ptr, size_t alignment)
 {
-  call_arg_error ("waitpid", name);
+  char *p0 = ptr;
+  char *p1 = p0 + alignment - 1;
+  return p1 - (size_t) p1 % alignment;
 }
 
-void
-write_error (char const *name)
+/* Return the address of a page-aligned buffer of at least SIZE bytes.
+   The caller should free *PTR when done with the buffer.  */
+
+void *
+page_aligned_alloc (void **ptr, size_t size)
 {
-  call_arg_error ("write", name);
+  size_t alignment = getpagesize ();
+  size_t size1 = size + alignment;
+  if (size1 < size)
+    xalloc_die ();
+  *ptr = xmalloc (size1);
+  return ptr_align (*ptr, alignment);
 }
 
-void
-write_error_details (char const *name, size_t status, size_t size)
+
+
+struct namebuf
 {
-  if (status == 0)
-    write_error (name);
-  else
-    ERROR ((0, 0,
-	    ngettext ("%s: Wrote only %lu of %lu byte",
-		      "%s: Wrote only %lu of %lu bytes",
-		      size),
-	    name, (unsigned long int) status, (unsigned long int) size));
-}
+  char *buffer;		/* directory, '/', and directory member */
+  size_t buffer_size;	/* allocated size of name_buffer */
+  size_t dir_length;	/* length of directory part in buffer */
+};
 
-void
-write_fatal (char const *name)
+namebuf_t
+namebuf_create (const char *dir)
 {
-  call_arg_fatal ("write", name);
+  namebuf_t buf = xmalloc (sizeof (*buf));
+  buf->buffer_size = strlen (dir) + 2;
+  buf->buffer = xmalloc (buf->buffer_size);
+  strcpy (buf->buffer, dir);
+  buf->dir_length = strlen (buf->buffer);
+  if (!ISSLASH (buf->buffer[buf->dir_length - 1]))
+    buf->buffer[buf->dir_length++] = DIRECTORY_SEPARATOR;
+  return buf;
 }
 
 void
-write_fatal_details (char const *name, ssize_t status, size_t size)
+namebuf_free (namebuf_t buf)
 {
-  write_error_details (name, status, size);
-  fatal_exit ();
+  free (buf->buffer);
+  free (buf);
 }
 
-
-/* Fork, aborting if unsuccessful.  */
-pid_t
-xfork (void)
+char *
+namebuf_name (namebuf_t buf, const char *name)
 {
-  pid_t p = fork ();
-  if (p == (pid_t) -1)
-    call_arg_fatal ("fork", _("child process"));
-  return p;
+  size_t len = strlen (name);
+  while (buf->dir_length + len + 1 >= buf->buffer_size)
+    buf->buffer = x2realloc (buf->buffer, &buf->buffer_size);
+  strcpy (buf->buffer + buf->dir_length, name);
+  return buf->buffer;
 }
 
-/* Create a pipe, aborting if unsuccessful.  */
 void
-xpipe (int fd[2])
+namebuf_add_dir (namebuf_t buf, const char *name)
 {
-  if (pipe (fd) < 0)
-    call_arg_fatal ("pipe", _("interprocess channel"));
+  static char dirsep[] = { DIRECTORY_SEPARATOR, 0 };
+  if (!ISSLASH (buf->buffer[buf->dir_length - 1]))
+    {
+      namebuf_name (buf, dirsep);
+      buf->dir_length++;
+    }
+  namebuf_name (buf, name);
+  buf->dir_length += strlen (name);
 }
 
-/* Return an unambiguous printable representation, allocated in slot N,
-   for NAME, suitable for diagnostics.  */
-char const *
-quote_n (int n, char const *name)
+char *
+namebuf_finish (namebuf_t buf)
 {
-  return quotearg_n_style (n, locale_quoting_style, name);
+  char *res = buf->buffer;
+
+  if (ISSLASH (buf->buffer[buf->dir_length - 1]))
+    buf->buffer[buf->dir_length] = 0;
+  free (buf);
+  return res;
 }
 
-/* Return an unambiguous printable representation of NAME, suitable
-   for diagnostics.  */
-char const *
-quote (char const *name)
+/* Return the filenames in directory NAME, relative to the chdir_fd.
+   If the directory does not exist, report error if MUST_EXIST is
+   true.
+
+   Return NULL on errors.
+*/
+char *
+tar_savedir (const char *name, int must_exist)
 {
-  return quote_n (0, name);
+  char *ret = NULL;
+  DIR *dir = NULL;
+  int fd = openat (chdir_fd, name, open_read_flags | O_DIRECTORY);
+  if (fd < 0)
+    {
+      if (!must_exist && errno == ENOENT)
+	return NULL;
+      open_error (name);
+    }
+  else if (! ((dir = fdopendir (fd))
+	      && (ret = streamsavedir (dir))))
+    savedir_error (name);
+
+  if (dir ? closedir (dir) != 0 : 0 <= fd && close (fd) != 0)
+    savedir_error (name);
+
+  return ret;
 }