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-rw-r--r--gl/lib/openat-proc.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/gl/lib/openat-proc.c b/gl/lib/openat-proc.c
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+++ b/gl/lib/openat-proc.c
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+/* 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;
+}