427 lines
8.5 KiB
C
427 lines
8.5 KiB
C
/* Low-level file-handling.
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Copyright (C) 2012-2016 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "common-defs.h"
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#include "filestuff.h"
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#include "gdb_vecs.h"
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#ifdef USE_WIN32API
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#include <winsock2.h>
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#include <windows.h>
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#define HAVE_SOCKETS 1
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#elif defined HAVE_SYS_SOCKET_H
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#include <sys/socket.h>
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/* Define HAVE_F_GETFD if we plan to use F_GETFD. */
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#define HAVE_F_GETFD F_GETFD
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#define HAVE_SOCKETS 1
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#endif
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#ifdef HAVE_SYS_RESOURCE_H
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#include <sys/resource.h>
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#endif /* HAVE_SYS_RESOURCE_H */
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#ifndef O_CLOEXEC
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#define O_CLOEXEC 0
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#endif
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#ifndef SOCK_CLOEXEC
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#define SOCK_CLOEXEC 0
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#endif
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#ifndef HAVE_FDWALK
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#include <dirent.h>
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/* Replacement for fdwalk, if the system doesn't define it. Walks all
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open file descriptors (though this implementation may walk closed
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ones as well, depending on the host platform's capabilities) and
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call FUNC with ARG. If FUNC returns non-zero, stops immediately
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and returns the same value. Otherwise, returns zero when
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finished. */
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static int
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fdwalk (int (*func) (void *, int), void *arg)
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{
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/* Checking __linux__ isn't great but it isn't clear what would be
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better. There doesn't seem to be a good way to check for this in
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configure. */
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#ifdef __linux__
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DIR *dir;
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dir = opendir ("/proc/self/fd");
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if (dir != NULL)
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{
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struct dirent *entry;
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int result = 0;
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for (entry = readdir (dir); entry != NULL; entry = readdir (dir))
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{
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long fd;
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char *tail;
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int result;
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errno = 0;
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fd = strtol (entry->d_name, &tail, 10);
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if (*tail != '\0' || errno != 0)
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continue;
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if ((int) fd != fd)
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{
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/* What can we do here really? */
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continue;
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}
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if (fd == dirfd (dir))
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continue;
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result = func (arg, fd);
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if (result != 0)
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break;
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}
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closedir (dir);
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return result;
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}
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/* We may fall through to the next case. */
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#endif
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{
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int max, fd;
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#if defined(HAVE_GETRLIMIT) && defined(RLIMIT_NOFILE)
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struct rlimit rlim;
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if (getrlimit (RLIMIT_NOFILE, &rlim) == 0 && rlim.rlim_max != RLIM_INFINITY)
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max = rlim.rlim_max;
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else
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#endif
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{
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#ifdef _SC_OPEN_MAX
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max = sysconf (_SC_OPEN_MAX);
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#else
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/* Whoops. */
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return 0;
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#endif /* _SC_OPEN_MAX */
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}
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for (fd = 0; fd < max; ++fd)
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{
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struct stat sb;
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int result;
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/* Only call FUNC for open fds. */
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if (fstat (fd, &sb) == -1)
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continue;
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result = func (arg, fd);
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if (result != 0)
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return result;
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}
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return 0;
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}
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}
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#endif /* HAVE_FDWALK */
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/* A VEC holding all the fds open when notice_open_fds was called. We
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don't use a hashtab because libiberty isn't linked into gdbserver;
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and anyway we don't expect there to be many open fds. */
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static VEC (int) *open_fds;
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/* An fdwalk callback function used by notice_open_fds. It puts the
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given file descriptor into the vec. */
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static int
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do_mark_open_fd (void *ignore, int fd)
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{
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VEC_safe_push (int, open_fds, fd);
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return 0;
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}
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/* See filestuff.h. */
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void
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notice_open_fds (void)
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{
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fdwalk (do_mark_open_fd, NULL);
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}
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/* See filestuff.h. */
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void
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mark_fd_no_cloexec (int fd)
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{
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do_mark_open_fd (NULL, fd);
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}
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/* See filestuff.h. */
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void
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unmark_fd_no_cloexec (int fd)
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{
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int i, val;
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for (i = 0; VEC_iterate (int, open_fds, i, val); ++i)
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{
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if (fd == val)
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{
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VEC_unordered_remove (int, open_fds, i);
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return;
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}
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}
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gdb_assert_not_reached (_("fd not found in open_fds"));
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}
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/* Helper function for close_most_fds that closes the file descriptor
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if appropriate. */
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static int
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do_close (void *ignore, int fd)
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{
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int i, val;
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for (i = 0; VEC_iterate (int, open_fds, i, val); ++i)
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{
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if (fd == val)
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{
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/* Keep this one open. */
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return 0;
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}
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}
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close (fd);
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return 0;
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}
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/* See filestuff.h. */
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void
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close_most_fds (void)
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{
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fdwalk (do_close, NULL);
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}
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/* This is a tri-state flag. When zero it means we haven't yet tried
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O_CLOEXEC. When positive it means that O_CLOEXEC works on this
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host. When negative, it means that O_CLOEXEC doesn't work. We
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track this state because, while gdb might have been compiled
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against a libc that supplies O_CLOEXEC, there is no guarantee that
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the kernel supports it. */
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static int trust_o_cloexec;
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/* Mark FD as close-on-exec, ignoring errors. Update
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TRUST_O_CLOEXEC. */
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static void
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mark_cloexec (int fd)
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{
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#ifdef HAVE_F_GETFD
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int old = fcntl (fd, F_GETFD, 0);
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if (old != -1)
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{
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fcntl (fd, F_SETFD, old | FD_CLOEXEC);
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if (trust_o_cloexec == 0)
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{
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if ((old & FD_CLOEXEC) != 0)
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trust_o_cloexec = 1;
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else
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trust_o_cloexec = -1;
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}
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}
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#endif /* HAVE_F_GETFD */
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}
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/* Depending on TRUST_O_CLOEXEC, mark FD as close-on-exec. */
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static void
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maybe_mark_cloexec (int fd)
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{
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if (trust_o_cloexec <= 0)
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mark_cloexec (fd);
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}
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#ifdef HAVE_SOCKETS
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/* Like maybe_mark_cloexec, but for callers that use SOCK_CLOEXEC. */
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static void
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socket_mark_cloexec (int fd)
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{
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if (SOCK_CLOEXEC == 0 || trust_o_cloexec <= 0)
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mark_cloexec (fd);
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}
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#endif
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/* See filestuff.h. */
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int
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gdb_open_cloexec (const char *filename, int flags, unsigned long mode)
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{
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int fd = open (filename, flags | O_CLOEXEC, mode);
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if (fd >= 0)
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maybe_mark_cloexec (fd);
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return fd;
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}
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/* See filestuff.h. */
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FILE *
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gdb_fopen_cloexec (const char *filename, const char *opentype)
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{
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FILE *result;
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/* Probe for "e" support once. But, if we can tell the operating
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system doesn't know about close on exec mode "e" without probing,
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skip it. E.g., the Windows runtime issues an "Invalid parameter
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passed to C runtime function" OutputDebugString warning for
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unknown modes. Assume that if O_CLOEXEC is zero, then "e" isn't
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supported. */
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static int fopen_e_ever_failed_einval = O_CLOEXEC == 0;
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if (!fopen_e_ever_failed_einval)
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{
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char *copy;
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copy = (char *) alloca (strlen (opentype) + 2);
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strcpy (copy, opentype);
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/* This is a glibc extension but we try it unconditionally on
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this path. */
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strcat (copy, "e");
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result = fopen (filename, copy);
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if (result == NULL && errno == EINVAL)
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{
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result = fopen (filename, opentype);
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if (result != NULL)
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fopen_e_ever_failed_einval = 1;
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}
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}
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else
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result = fopen (filename, opentype);
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if (result != NULL)
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maybe_mark_cloexec (fileno (result));
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return result;
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}
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#ifdef HAVE_SOCKETS
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/* See filestuff.h. */
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int
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gdb_socketpair_cloexec (int domain, int style, int protocol,
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int filedes[2])
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{
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#ifdef HAVE_SOCKETPAIR
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int result = socketpair (domain, style | SOCK_CLOEXEC, protocol, filedes);
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if (result != -1)
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{
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socket_mark_cloexec (filedes[0]);
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socket_mark_cloexec (filedes[1]);
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}
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return result;
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#else
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gdb_assert_not_reached (_("socketpair not available on this host"));
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#endif
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}
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/* See filestuff.h. */
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int
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gdb_socket_cloexec (int domain, int style, int protocol)
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{
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int result = socket (domain, style | SOCK_CLOEXEC, protocol);
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if (result != -1)
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socket_mark_cloexec (result);
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return result;
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}
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#endif
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/* See filestuff.h. */
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int
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gdb_pipe_cloexec (int filedes[2])
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{
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int result;
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#ifdef HAVE_PIPE2
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result = pipe2 (filedes, O_CLOEXEC);
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if (result != -1)
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{
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maybe_mark_cloexec (filedes[0]);
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maybe_mark_cloexec (filedes[1]);
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}
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#else
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#ifdef HAVE_PIPE
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result = pipe (filedes);
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if (result != -1)
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{
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mark_cloexec (filedes[0]);
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mark_cloexec (filedes[1]);
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}
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#else /* HAVE_PIPE */
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gdb_assert_not_reached (_("pipe not available on this host"));
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#endif /* HAVE_PIPE */
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#endif /* HAVE_PIPE2 */
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return result;
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}
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/* Helper function which does the work for make_cleanup_close. */
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static void
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do_close_cleanup (void *arg)
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{
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int *fd = (int *) arg;
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close (*fd);
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}
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/* See filestuff.h. */
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struct cleanup *
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make_cleanup_close (int fd)
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{
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int *saved_fd = XNEW (int);
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*saved_fd = fd;
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return make_cleanup_dtor (do_close_cleanup, saved_fd, xfree);
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}
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