1 files changed, 135 insertions, 0 deletions
diff --git a/lib/openat-proc.c b/lib/openat-proc.c
new file mode 100644
index 0000000..3bacf7d
--- /dev/null
+++ b/lib/openat-proc.c
@@ -0,0 +1,135 @@
+/* Create /proc/self/fd-related names for subfiles of open directories.
+
+   Copyright (C) 2006, 2009-2022 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 <https://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 <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifdef __KLIBC__
+# include <InnoTekLIBC/backend.h>
+#endif
+
+#include "intprops.h"
+
+/* Set BUF to the name of the subfile of the directory identified by
+   FD, where the subfile is named FILE.  If successful, return BUF if
+   the result fits in BUF, dynamically allocated memory otherwise.
+   Return NULL (setting errno) on error.  */
+char *
+openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
+{
+  char *result = buf;
+  int dirlen;
+
+  /* Make sure the caller gets ENOENT when appropriate.  */
+  if (!*file)
+    {
+      buf[0] = '\0';
+      return buf;
+    }
+
+#ifndef __KLIBC__
+# define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/"
+  {
+    enum {
+      PROC_SELF_FD_DIR_SIZE_BOUND
+        = (sizeof PROC_SELF_FD_FORMAT - (sizeof "%d" - 1)
+           + INT_STRLEN_BOUND (int))
+    };
+
+    static int proc_status = 0;
+    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_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK | O_CLOEXEC);
+        if (proc_self_fd < 0)
+          proc_status = -1;
+        else
+          {
+            /* Detect whether /proc/self/fd/%i/../fd exists, where %i is the
+               number of a file descriptor open on /proc/self/fd.  On Linux,
+               that name resolves to /proc/self/fd, which was opened above.
+               However, on Solaris, it may resolve to /proc/self/fd/fd, which
+               cannot exist, since all names in /proc/self/fd are numeric.  */
+            char dotdot_buf[PROC_SELF_FD_DIR_SIZE_BOUND + sizeof "../fd" - 1];
+            sprintf (dotdot_buf, PROC_SELF_FD_FORMAT "../fd", proc_self_fd);
+            proc_status = access (dotdot_buf, F_OK) ? -1 : 1;
+            close (proc_self_fd);
+          }
+      }
+
+    if (proc_status < 0)
+      return NULL;
+    else
+      {
+        size_t bufsize = PROC_SELF_FD_DIR_SIZE_BOUND + strlen (file);
+        if (OPENAT_BUFFER_SIZE < bufsize)
+          {
+            result = malloc (bufsize);
+            if (! result)
+              return NULL;
+          }
+
+        dirlen = sprintf (result, PROC_SELF_FD_FORMAT, fd);
+      }
+  }
+#else
+  /* OS/2 kLIBC provides a function to retrieve a path from a fd.  */
+  {
+    char dir[_MAX_PATH];
+    size_t bufsize;
+
+    if (__libc_Back_ioFHToPath (fd, dir, sizeof dir))
+      return NULL;
+
+    dirlen = strlen (dir);
+    bufsize = dirlen + 1 + strlen (file) + 1; /* 1 for '/', 1 for null */
+    if (OPENAT_BUFFER_SIZE < bufsize)
+      {
+        result = malloc (bufsize);
+        if (! result)
+          return NULL;
+      }
+
+    strcpy (result, dir);
+    result[dirlen++] = '/';
+  }
+#endif
+
+  strcpy (result + dirlen, file);
+  return result;
+}