X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=lib%2Fopenat-proc.c;fp=lib%2Fopenat-proc.c;h=25384127ebf944f7aeb83ef11e40ef19afb34776;hb=a2016c1de6e4884f6c8ed5cc498f3bf821c25ca4;hp=0000000000000000000000000000000000000000;hpb=c7e61475680fa226bd9b8bdd469cd66914e630f5;p=debian%2Fgzip

diff --git a/lib/openat-proc.c b/lib/openat-proc.c
new file mode 100644
index 0000000..2538412
--- /dev/null
+++ b/lib/openat-proc.c
@@ -0,0 +1,105 @@
+/* Create /proc/self/fd-related names for subfiles of open directories.
+
+   Copyright (C) 2006, 2009-2010 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 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/>.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include "openat-priv.h"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "dirname.h"
+#include "intprops.h"
+#include "same-inode.h"
+#include "xalloc.h"
+
+/* The results of open() in this file are not used with fchdir,
+   and we do not leak fds to any single-threaded code that could use stdio,
+   therefore save some unnecessary work in fchdir.c.
+   FIXME - if the kernel ever adds support for multi-thread safety for
+   avoiding standard fds, then we should use open_safer.  */
+#undef open
+#undef close
+
+#define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
+
+#define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
+  (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
+   + INT_STRLEN_BOUND (int) + (len) + 1)
+
+
+/* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
+   respectively for %d and %s.  If successful, return BUF if the
+   result fits in BUF, dynamically allocated memory otherwise.  But
+   return NULL if /proc is not reliable.  */
+char *
+openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
+{
+  static int proc_status = 0;
+
+  /* Make sure the caller gets ENOENT when appropriate.  */
+  if (!*file)
+    {
+      buf[0] = '\0';
+      return buf;
+    }
+
+  if (! proc_status)
+    {
+      /* Set PROC_STATUS to a positive value if /proc/self/fd is
+         reliable, and a negative value otherwise.  Solaris 10
+         /proc/self/fd mishandles "..", and any file name might expand
+         to ".." after symbolic link expansion, so avoid /proc/self/fd
+         if it mishandles "..".  Solaris 10 has openat, but this
+         problem is exhibited on code that built on Solaris 8 and
+         running on Solaris 10.  */
+
+      int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
+      if (proc_self_fd < 0)
+        proc_status = -1;
+      else
+        {
+          struct stat proc_self_fd_dotdot_st;
+          struct stat proc_self_st;
+          char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
+          sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
+          proc_status =
+            ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
+              && stat ("/proc/self", &proc_self_st) == 0
+              && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
+             ? 1 : -1);
+          close (proc_self_fd);
+        }
+    }
+
+  if (proc_status < 0)
+    return NULL;
+  else
+    {
+      size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
+      char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
+      sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
+      return result;
+    }
+}