--- /dev/null
+/* Linux namespaces(7) support.
+
+ Copyright (C) 2015 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ 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/>. */
+
+#include "common-defs.h"
+#include "nat/linux-namespaces.h"
+#include "filestuff.h"
+#include <fcntl.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <signal.h>
+#include <sched.h>
+
+/* See nat/linux-namespaces.h. */
+int debug_linux_namespaces;
+
+/* Handle systems without setns. */
+
+#ifndef HAVE_SETNS
+static int
+setns (int fd, int nstype)
+{
+#ifdef __NR_setns
+ return syscall (__NR_setns, fd, nstype);
+#else
+ errno = ENOSYS;
+ return -1;
+#endif
+}
+#endif
+
+/* A Linux namespace. */
+
+struct linux_ns
+{
+ /* Filename of this namespace's entries in /proc/PID/ns. */
+ const char *filename;
+
+ /* Nonzero if this object has been initialized. */
+ int initialized;
+
+ /* Nonzero if this namespace is supported on this system. */
+ int supported;
+
+ /* ID of the namespace the calling process is in, used to
+ see if other processes share the namespace. The code in
+ this file assumes that the calling process never changes
+ namespace. */
+ ino_t id;
+};
+
+/* Return the absolute filename of process PID's /proc/PID/ns
+ entry for namespace NS. The returned value persists until
+ this function is next called. */
+
+static const char *
+linux_ns_filename (struct linux_ns *ns, int pid)
+{
+ static char filename[PATH_MAX];
+
+ gdb_assert (pid > 0);
+ xsnprintf (filename, sizeof (filename), "/proc/%d/ns/%s", pid,
+ ns->filename);
+
+ return filename;
+}
+
+/* Return a representation of the caller's TYPE namespace, or
+ NULL if TYPE namespaces are not supported on this system. */
+
+static struct linux_ns *
+linux_ns_get_namespace (enum linux_ns_type type)
+{
+ static struct linux_ns namespaces[NUM_LINUX_NS_TYPES] =
+ {
+ { "ipc" },
+ { "mnt" },
+ { "net" },
+ { "pid" },
+ { "user" },
+ { "uts" },
+ };
+ struct linux_ns *ns;
+
+ gdb_assert (type >= 0 && type < NUM_LINUX_NS_TYPES);
+ ns = &namespaces[type];
+
+ if (!ns->initialized)
+ {
+ struct stat sb;
+
+ if (stat (linux_ns_filename (ns, getpid ()), &sb) == 0)
+ {
+ ns->id = sb.st_ino;
+
+ ns->supported = 1;
+ }
+
+ ns->initialized = 1;
+ }
+
+ return ns->supported ? ns : NULL;
+}
+
+/* See nat/linux-namespaces.h. */
+
+int
+linux_ns_same (pid_t pid, enum linux_ns_type type)
+{
+ struct linux_ns *ns = linux_ns_get_namespace (type);
+ const char *filename;
+ struct stat sb;
+
+ /* If the kernel does not support TYPE namespaces then there's
+ effectively only one TYPE namespace that all processes on
+ the system share. */
+ if (ns == NULL)
+ return 1;
+
+ /* Stat PID's TYPE namespace entry to get the namespace ID. This
+ might fail if the process died, or if we don't have the right
+ permissions (though we should be attached by this time so this
+ seems unlikely). In any event, we can't make any decisions and
+ must throw. */
+ filename = linux_ns_filename (ns, pid);
+ if (stat (filename, &sb) != 0)
+ perror_with_name (filename);
+
+ return sb.st_ino == ns->id;
+}
+
+/* We need to use setns(2) to handle filesystem access in mount
+ namespaces other than our own, but this isn't permitted for
+ multithreaded processes. GDB is multithreaded when compiled
+ with Guile support, and may become multithreaded if compiled
+ with Python support. We deal with this by spawning a single-
+ threaded helper process to access mount namespaces other than
+ our own.
+
+ The helper process is started the first time a call to setns
+ is required. The main process (GDB or gdbserver) communicates
+ with the helper via sockets, passing file descriptors where
+ necessary using SCM_RIGHTS. Once started the helper process
+ runs until the main process terminates; when this happens the
+ helper will receive socket errors, notice that its parent died,
+ and exit accordingly (see mnsh_maybe_mourn_peer).
+
+ The protocol is that the main process sends a request in a
+ single message, and the helper replies to every message it
+ receives with a single-message response. If the helper
+ receives a message it does not understand it will reply with
+ a MNSH_MSG_ERROR message. The main process checks all
+ responses it receives with gdb_assert, so if the main process
+ receives something unexpected (which includes MNSH_MSG_ERROR)
+ the main process will call internal_error.
+
+ For avoidance of doubt, if the helper process receives a
+ message it doesn't handle it will reply with MNSH_MSG_ERROR.
+ If the main process receives MNSH_MSG_ERROR at any time then
+ it will call internal_error. If internal_error causes the
+ main process to exit, the helper will notice this and also
+ exit. The helper will not exit until the main process
+ terminates, so if the user continues through internal_error
+ the helper will still be there awaiting requests from the
+ main process.
+
+ Messages in both directions have the following payload:
+
+ - TYPE (enum mnsh_msg_type, always sent) - the message type.
+ - INT1 and
+ - INT2 (int, always sent, though not always used) - two
+ values whose meaning is message-type-dependent.
+ See enum mnsh_msg_type documentation below.
+ - FD (int, optional, sent using SCM_RIGHTS) - an open file
+ descriptor.
+ - BUF (unstructured data, optional) - some data with message-
+ type-dependent meaning.
+
+ Note that the helper process is the child of a call to fork,
+ so all code in the helper must be async-signal-safe. */
+
+/* Mount namespace helper message types. */
+
+enum mnsh_msg_type
+ {
+ /* A communication error occurred. Receipt of this message
+ by either end will cause an assertion failure in the main
+ process. */
+ MNSH_MSG_ERROR,
+
+ /* Requests, sent from the main process to the helper. */
+
+ /* A request that the helper call setns. Arguments should
+ be passed in FD and INT1. Helper should respond with a
+ MNSH_RET_INT. */
+ MNSH_REQ_SETNS,
+
+ /* A request that the helper call open. Arguments should
+ be passed in BUF, INT1 and INT2. The filename (in BUF)
+ should include a terminating NUL character. The helper
+ should respond with a MNSH_RET_FD. */
+ MNSH_REQ_OPEN,
+
+ /* A request that the helper call unlink. The single
+ argument (the filename) should be passed in BUF, and
+ should include a terminating NUL character. The helper
+ should respond with a MNSH_RET_INT. */
+ MNSH_REQ_UNLINK,
+
+ /* A request that the helper call readlink. The single
+ argument (the filename) should be passed in BUF, and
+ should include a terminating NUL character. The helper
+ should respond with a MNSH_RET_INTSTR. */
+ MNSH_REQ_READLINK,
+
+ /* Responses, sent to the main process from the helper. */
+
+ /* Return an integer in INT1 and errno in INT2. */
+ MNSH_RET_INT,
+
+ /* Return a file descriptor in FD if one was opened or an
+ integer in INT1 otherwise. Return errno in INT2. */
+ MNSH_RET_FD,
+
+ /* Return an integer in INT1, errno in INT2, and optionally
+ some data in BUF. */
+ MNSH_RET_INTSTR,
+ };
+
+/* Print a string representation of a message using debug_printf.
+ This function is not async-signal-safe so should never be
+ called from the helper. */
+
+static void
+mnsh_debug_print_message (enum mnsh_msg_type type,
+ int fd, int int1, int int2,
+ const void *buf, int bufsiz)
+{
+ gdb_byte *c = (gdb_byte *) buf;
+ gdb_byte *cl = c + bufsiz;
+
+ switch (type)
+ {
+ case MNSH_MSG_ERROR:
+ debug_printf ("ERROR");
+ break;
+
+ case MNSH_REQ_SETNS:
+ debug_printf ("SETNS");
+ break;
+
+ case MNSH_REQ_OPEN:
+ debug_printf ("OPEN");
+ break;
+
+ case MNSH_REQ_UNLINK:
+ debug_printf ("UNLINK");
+ break;
+
+ case MNSH_REQ_READLINK:
+ debug_printf ("READLINK");
+ break;
+
+ case MNSH_RET_INT:
+ debug_printf ("INT");
+ break;
+
+ case MNSH_RET_FD:
+ debug_printf ("FD");
+ break;
+
+ case MNSH_RET_INTSTR:
+ debug_printf ("INTSTR");
+ break;
+
+ default:
+ debug_printf ("unknown-packet-%d", type);
+ }
+
+ debug_printf (" %d %d %d \"", fd, int1, int2);
+
+ for (; c < cl; c++)
+ debug_printf (*c >= ' ' && *c <= '~' ? "%c" : "\\%o", *c);
+
+ debug_printf ("\"");
+}
+
+/* Forward declaration. */
+
+static void mnsh_maybe_mourn_peer (void);
+
+/* Send a message. The argument SOCK is the file descriptor of the
+ sending socket, the other arguments are the payload to send.
+ Return the number of bytes sent on success. Return -1 on failure
+ and set errno appropriately. This function is called by both the
+ main process and the helper so must be async-signal-safe. */
+
+static ssize_t
+mnsh_send_message (int sock, enum mnsh_msg_type type,
+ int fd, int int1, int int2,
+ const void *buf, int bufsiz)
+{
+ struct msghdr msg;
+ struct iovec iov[4];
+ char fdbuf[CMSG_SPACE (sizeof (fd))];
+ ssize_t size;
+
+ /* Build the basic TYPE, INT1, INT2 message. */
+ memset (&msg, 0, sizeof (msg));
+ msg.msg_iov = iov;
+
+ iov[0].iov_base = &type;
+ iov[0].iov_len = sizeof (type);
+ iov[1].iov_base = &int1;
+ iov[1].iov_len = sizeof (int1);
+ iov[2].iov_base = &int2;
+ iov[2].iov_len = sizeof (int2);
+
+ msg.msg_iovlen = 3;
+
+ /* Append BUF if supplied. */
+ if (buf != NULL && bufsiz > 0)
+ {
+ iov[3].iov_base = alloca (bufsiz);
+ memcpy (iov[3].iov_base, buf, bufsiz);
+ iov[3].iov_len = bufsiz;
+
+ msg.msg_iovlen ++;
+ }
+
+ /* Attach FD if supplied. */
+ if (fd >= 0)
+ {
+ struct cmsghdr *cmsg;
+
+ msg.msg_control = fdbuf;
+ msg.msg_controllen = sizeof (fdbuf);
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+
+ memcpy (CMSG_DATA (cmsg), &fd, sizeof (int));
+
+ msg.msg_controllen = cmsg->cmsg_len;
+ }
+
+ /* Send the message. */
+ size = sendmsg (sock, &msg, 0);
+
+ if (size < 0)
+ mnsh_maybe_mourn_peer ();
+
+ if (debug_linux_namespaces)
+ {
+ debug_printf ("mnsh: send: ");
+ mnsh_debug_print_message (type, fd, int1, int2, buf, bufsiz);
+ debug_printf (" -> %ld\n", size);
+ }
+
+ return size;
+}
+
+/* Receive a message. The argument SOCK is the file descriptor of
+ the receiving socket, the other arguments point to storage for
+ the received payload. Returns the number of bytes stored into
+ BUF on success, which may be zero in the event no BUF was sent.
+ Return -1 on failure and set errno appropriately. This function
+ is called from both the main process and the helper and must be
+ async-signal-safe. */
+
+static ssize_t
+mnsh_recv_message (int sock, enum mnsh_msg_type *type,
+ int *fd, int *int1, int *int2,
+ void *buf, int bufsiz)
+{
+ struct msghdr msg;
+ struct iovec iov[4];
+ char fdbuf[CMSG_SPACE (sizeof (*fd))];
+ struct cmsghdr *cmsg;
+ ssize_t size, fixed_size;
+ int i;
+
+ /* Build the message to receive data into. */
+ memset (&msg, 0, sizeof (msg));
+ msg.msg_iov = iov;
+
+ iov[0].iov_base = type;
+ iov[0].iov_len = sizeof (*type);
+ iov[1].iov_base = int1;
+ iov[1].iov_len = sizeof (*int1);
+ iov[2].iov_base = int2;
+ iov[2].iov_len = sizeof (*int2);
+ iov[3].iov_base = buf;
+ iov[3].iov_len = bufsiz;
+
+ msg.msg_iovlen = 4;
+
+ for (fixed_size = i = 0; i < msg.msg_iovlen - 1; i++)
+ fixed_size += iov[i].iov_len;
+
+ msg.msg_control = fdbuf;
+ msg.msg_controllen = sizeof (fdbuf);
+
+ /* Receive the message. */
+ size = recvmsg (sock, &msg, MSG_CMSG_CLOEXEC);
+ if (size < 0)
+ {
+ if (debug_linux_namespaces)
+ debug_printf ("namespace-helper: recv failed (%ld)\n", size);
+
+ mnsh_maybe_mourn_peer ();
+
+ return size;
+ }
+
+ /* Check for truncation. */
+ if (size < fixed_size || (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC)))
+ {
+ if (debug_linux_namespaces)
+ debug_printf ("namespace-helper: recv truncated (%ld 0x%x)\n",
+ size, msg.msg_flags);
+
+ mnsh_maybe_mourn_peer ();
+
+ errno = EBADMSG;
+ return -1;
+ }
+
+ /* Unpack the file descriptor if supplied. */
+ cmsg = CMSG_FIRSTHDR (&msg);
+ if (cmsg != NULL
+ && cmsg->cmsg_len == CMSG_LEN (sizeof (int))
+ && cmsg->cmsg_level == SOL_SOCKET
+ && cmsg->cmsg_type == SCM_RIGHTS)
+ memcpy (fd, CMSG_DATA (cmsg), sizeof (int));
+ else
+ *fd = -1;
+
+ if (debug_linux_namespaces)
+ {
+ debug_printf ("mnsh: recv: ");
+ mnsh_debug_print_message (*type, *fd, *int1, *int2, buf,
+ size - fixed_size);
+ debug_printf ("\n");
+ }
+
+ /* Return the number of bytes of data in BUF. */
+ return size - fixed_size;
+}
+
+/* Shortcuts for returning results from the helper. */
+
+#define mnsh_return_int(sock, result, error) \
+ mnsh_send_message (sock, MNSH_RET_INT, -1, result, error, NULL, 0)
+
+#define mnsh_return_fd(sock, fd, error) \
+ mnsh_send_message (sock, MNSH_RET_FD, \
+ (fd) < 0 ? -1 : (fd), \
+ (fd) < 0 ? (fd) : 0, \
+ error, NULL, 0)
+
+#define mnsh_return_intstr(sock, result, buf, bufsiz, error) \
+ mnsh_send_message (sock, MNSH_RET_INTSTR, -1, result, error, \
+ buf, bufsiz)
+
+/* Handle a MNSH_REQ_SETNS message. Must be async-signal-safe. */
+
+static ssize_t
+mnsh_handle_setns (int sock, int fd, int nstype)
+{
+ int result = setns (fd, nstype);
+
+ return mnsh_return_int (sock, result, errno);
+}
+
+/* Handle a MNSH_REQ_OPEN message. Must be async-signal-safe. */
+
+static ssize_t
+mnsh_handle_open (int sock, const char *filename,
+ int flags, mode_t mode)
+{
+ int fd = gdb_open_cloexec (filename, flags, mode);
+ ssize_t result = mnsh_return_fd (sock, fd, errno);
+
+ if (fd >= 0)
+ close (fd);
+
+ return result;
+}
+
+/* Handle a MNSH_REQ_UNLINK message. Must be async-signal-safe. */
+
+static ssize_t
+mnsh_handle_unlink (int sock, const char *filename)
+{
+ int result = unlink (filename);
+
+ return mnsh_return_int (sock, result, errno);
+}
+
+/* Handle a MNSH_REQ_READLINK message. Must be async-signal-safe. */
+
+static ssize_t
+mnsh_handle_readlink (int sock, const char *filename)
+{
+ char buf[PATH_MAX];
+ int len = readlink (filename, buf, sizeof (buf));
+
+ return mnsh_return_intstr (sock, len,
+ buf, len < 0 ? 0 : len,
+ errno);
+}
+
+/* The helper process. Never returns. Must be async-signal-safe. */
+
+static void mnsh_main (int sock) ATTRIBUTE_NORETURN;
+
+static void
+mnsh_main (int sock)
+{
+ while (1)
+ {
+ enum mnsh_msg_type type;
+ int fd, int1, int2;
+ char buf[PATH_MAX];
+ ssize_t size, response = -1;
+
+ size = mnsh_recv_message (sock, &type,
+ &fd, &int1, &int2,
+ buf, sizeof (buf));
+
+ if (size >= 0 && size < sizeof (buf))
+ {
+ switch (type)
+ {
+ case MNSH_REQ_SETNS:
+ if (fd > 0)
+ response = mnsh_handle_setns (sock, fd, int1);
+ break;
+
+ case MNSH_REQ_OPEN:
+ if (size > 0 && buf[size - 1] == '\0')
+ response = mnsh_handle_open (sock, buf, int1, int2);
+ break;
+
+ case MNSH_REQ_UNLINK:
+ if (size > 0 && buf[size - 1] == '\0')
+ response = mnsh_handle_unlink (sock, buf);
+ break;
+
+ case MNSH_REQ_READLINK:
+ if (size > 0 && buf[size - 1] == '\0')
+ response = mnsh_handle_readlink (sock, buf);
+ break;
+
+ default:
+ break; /* Handled below. */
+ }
+ }
+
+ /* Close any file descriptors we were passed. */
+ if (fd >= 0)
+ close (fd);
+
+ /* Can't handle this message, bounce it back. */
+ if (response < 0)
+ {
+ if (size < 0)
+ size = 0;
+
+ mnsh_send_message (sock, MNSH_MSG_ERROR,
+ -1, int1, int2, buf, size);
+ }
+ }
+}
+
+/* The mount namespace helper process. */
+
+struct linux_mnsh
+{
+ /* PID of helper. */
+ pid_t pid;
+
+ /* Socket for communication. */
+ int sock;
+
+ /* ID of the mount namespace the helper is currently in. */
+ ino_t nsid;
+};
+
+/* In the helper process this is set to the PID of the process that
+ created the helper (i.e. GDB or gdbserver). In the main process
+ this is set to zero. Used by mnsh_maybe_mourn_peer. */
+static int mnsh_creator_pid = 0;
+
+/* Return an object representing the mount namespace helper process.
+ If no mount namespace helper process has been started then start
+ one. Return NULL if no mount namespace helper process could be
+ started. */
+
+static struct linux_mnsh *
+linux_mntns_get_helper (void)
+{
+ static struct linux_mnsh *helper = NULL;
+
+ if (helper == NULL)
+ {
+ static struct linux_mnsh h;
+ struct linux_ns *ns;
+ pid_t helper_creator = getpid ();
+ int sv[2];
+
+ ns = linux_ns_get_namespace (LINUX_NS_MNT);
+ if (ns == NULL)
+ return NULL;
+
+ if (gdb_socketpair_cloexec (AF_UNIX, SOCK_STREAM, 0, sv) < 0)
+ return NULL;
+
+ h.pid = fork ();
+ if (h.pid < 0)
+ {
+ int saved_errno = errno;
+
+ close (sv[0]);
+ close (sv[1]);
+
+ errno = saved_errno;
+ return NULL;
+ }
+
+ if (h.pid == 0)
+ {
+ /* Child process. */
+ close (sv[0]);
+
+ mnsh_creator_pid = helper_creator;
+
+ /* Debug printing isn't async-signal-safe. */
+ debug_linux_namespaces = 0;
+
+ mnsh_main (sv[1]);
+ }
+
+ /* Parent process. */
+ close (sv[1]);
+
+ helper = &h;
+ helper->sock = sv[0];
+ helper->nsid = ns->id;
+
+ if (debug_linux_namespaces)
+ debug_printf ("Started mount namespace helper process %d\n",
+ helper->pid);
+ }
+
+ return helper;
+}
+
+/* Check whether the other process died and act accordingly. Called
+ whenever a socket error occurs, from both the main process and the
+ helper. Must be async-signal-safe when called from the helper. */
+
+static void
+mnsh_maybe_mourn_peer (void)
+{
+ if (mnsh_creator_pid != 0)
+ {
+ /* We're in the helper. Check if our current parent is the
+ process that started us. If it isn't, then our original
+ parent died and we've been reparented. Exit immediately
+ if that's the case. */
+ if (getppid () != mnsh_creator_pid)
+ _exit (0);
+ }
+ else
+ {
+ /* We're in the main process. */
+
+ struct linux_mnsh *helper = linux_mntns_get_helper ();
+ int status;
+ pid_t pid;
+
+ if (helper->pid < 0)
+ {
+ /* We already mourned it. */
+ return;
+ }
+
+ pid = waitpid (helper->pid, &status, WNOHANG);
+ if (pid == 0)
+ {
+ /* The helper is still alive. */
+ return;
+ }
+ else if (pid == -1)
+ {
+ if (errno == ECHILD)
+ warning (_("mount namespace helper vanished?"));
+ else
+ internal_warning (__FILE__, __LINE__,
+ _("unhandled error %d"), errno);
+ }
+ else if (pid == helper->pid)
+ {
+ if (WIFEXITED (status))
+ warning (_("mount namespace helper exited with status %d"),
+ WEXITSTATUS (status));
+ else if (WIFSIGNALED (status))
+ warning (_("mount namespace helper killed by signal %d"),
+ WTERMSIG (status));
+ else
+ internal_warning (__FILE__, __LINE__,
+ _("unhandled status %d"), status);
+ }
+ else
+ internal_warning (__FILE__, __LINE__,
+ _("unknown pid %d"), pid);
+
+ /* Something unrecoverable happened. */
+ helper->pid = -1;
+ }
+}
+
+/* Shortcuts for sending messages to the helper. */
+
+#define mnsh_send_setns(helper, fd, nstype) \
+ mnsh_send_message (helper->sock, MNSH_REQ_SETNS, fd, nstype, 0, \
+ NULL, 0)
+
+#define mnsh_send_open(helper, filename, flags, mode) \
+ mnsh_send_message (helper->sock, MNSH_REQ_OPEN, -1, flags, mode, \
+ filename, strlen (filename) + 1)
+
+#define mnsh_send_unlink(helper, filename) \
+ mnsh_send_message (helper->sock, MNSH_REQ_UNLINK, -1, 0, 0, \
+ filename, strlen (filename) + 1)
+
+#define mnsh_send_readlink(helper, filename) \
+ mnsh_send_message (helper->sock, MNSH_REQ_READLINK, -1, 0, 0, \
+ filename, strlen (filename) + 1)
+
+/* Receive a message from the helper. Issue an assertion failure if
+ the message isn't a correctly-formatted MNSH_RET_INT. Set RESULT
+ and ERROR and return 0 on success. Set errno and return -1 on
+ failure. */
+
+static int
+mnsh_recv_int (struct linux_mnsh *helper, int *result, int *error)
+{
+ enum mnsh_msg_type type;
+ char buf[PATH_MAX];
+ ssize_t size;
+ int fd;
+
+ size = mnsh_recv_message (helper->sock, &type, &fd,
+ result, error,
+ buf, sizeof (buf));
+ if (size < 0)
+ return -1;
+
+ gdb_assert (type == MNSH_RET_INT);
+ gdb_assert (fd == -1);
+ gdb_assert (size == 0);
+
+ return 0;
+}
+
+/* Receive a message from the helper. Issue an assertion failure if
+ the message isn't a correctly-formatted MNSH_RET_FD. Set FD and
+ ERROR and return 0 on success. Set errno and return -1 on
+ failure. */
+
+static int
+mnsh_recv_fd (struct linux_mnsh *helper, int *fd, int *error)
+{
+ enum mnsh_msg_type type;
+ char buf[PATH_MAX];
+ ssize_t size;
+ int result;
+
+ size = mnsh_recv_message (helper->sock, &type, fd,
+ &result, error,
+ buf, sizeof (buf));
+ if (size < 0)
+ return -1;
+
+ gdb_assert (type == MNSH_RET_FD);
+ gdb_assert (size == 0);
+
+ if (*fd < 0)
+ {
+ gdb_assert (result < 0);
+ *fd = result;
+ }
+
+ return 0;
+}
+
+/* Receive a message from the helper. Issue an assertion failure if
+ the message isn't a correctly-formatted MNSH_RET_INTSTR. Set
+ RESULT and ERROR and optionally store data in BUF, then return
+ the number of bytes stored in BUF on success (this may be zero).
+ Set errno and return -1 on error. */
+
+static ssize_t
+mnsh_recv_intstr (struct linux_mnsh *helper,
+ int *result, int *error,
+ void *buf, int bufsiz)
+{
+ enum mnsh_msg_type type;
+ ssize_t size;
+ int fd;
+
+ size = mnsh_recv_message (helper->sock, &type, &fd,
+ result, error,
+ buf, bufsiz);
+
+ if (size < 0)
+ return -1;
+
+ gdb_assert (type == MNSH_RET_INTSTR);
+ gdb_assert (fd == -1);
+
+ return size;
+}
+
+/* Return values for linux_mntns_access_fs. */
+
+enum mnsh_fs_code
+ {
+ /* Something went wrong, errno is set. */
+ MNSH_FS_ERROR = -1,
+
+ /* The main process is in the correct mount namespace.
+ The caller should access the filesystem directly. */
+ MNSH_FS_DIRECT,
+
+ /* The helper is in the correct mount namespace.
+ The caller should access the filesystem via the helper. */
+ MNSH_FS_HELPER
+ };
+
+/* Return a value indicating how the caller should access the
+ mount namespace of process PID. */
+
+static enum mnsh_fs_code
+linux_mntns_access_fs (pid_t pid)
+{
+ struct cleanup *old_chain;
+ struct linux_ns *ns;
+ struct stat sb;
+ struct linux_mnsh *helper;
+ ssize_t size;
+ int fd, saved_errno;
+
+ if (pid == getpid ())
+ return MNSH_FS_DIRECT;
+
+ ns = linux_ns_get_namespace (LINUX_NS_MNT);
+ if (ns == NULL)
+ return MNSH_FS_DIRECT;
+
+ old_chain = make_cleanup (null_cleanup, NULL);
+
+ fd = gdb_open_cloexec (linux_ns_filename (ns, pid), O_RDONLY, 0);
+ if (fd < 0)
+ goto error;
+
+ old_chain = make_cleanup_close (fd);
+
+ if (fstat (fd, &sb) != 0)
+ goto error;
+
+ if (sb.st_ino == ns->id)
+ {
+ do_cleanups (old_chain);
+
+ return MNSH_FS_DIRECT;
+ }
+
+ helper = linux_mntns_get_helper ();
+ if (helper == NULL)
+ goto error;
+
+ if (sb.st_ino != helper->nsid)
+ {
+ int result, error;
+
+ size = mnsh_send_setns (helper, fd, 0);
+ if (size < 0)
+ goto error;
+
+ if (mnsh_recv_int (helper, &result, &error) != 0)
+ goto error;
+
+ if (result != 0)
+ {
+ /* ENOSYS indicates that an entire function is unsupported
+ (it's not appropriate for our versions of open/unlink/
+ readlink to sometimes return with ENOSYS depending on how
+ they're called) so we convert ENOSYS to ENOTSUP if setns
+ fails. */
+ if (error == ENOSYS)
+ error = ENOTSUP;
+
+ errno = error;
+ goto error;
+ }
+
+ helper->nsid = sb.st_ino;
+ }
+
+ do_cleanups (old_chain);
+
+ return MNSH_FS_HELPER;
+
+error:
+ saved_errno = errno;
+
+ do_cleanups (old_chain);
+
+ errno = saved_errno;
+ return MNSH_FS_ERROR;
+}
+
+/* See nat/linux-namespaces.h. */
+
+int
+linux_mntns_open_cloexec (pid_t pid, const char *filename,
+ int flags, mode_t mode)
+{
+ enum mnsh_fs_code access = linux_mntns_access_fs (pid);
+ struct linux_mnsh *helper;
+ int fd, error;
+ ssize_t size;
+
+ if (access == MNSH_FS_ERROR)
+ return -1;
+
+ if (access == MNSH_FS_DIRECT)
+ return gdb_open_cloexec (filename, flags, mode);
+
+ gdb_assert (access == MNSH_FS_HELPER);
+
+ helper = linux_mntns_get_helper ();
+
+ size = mnsh_send_open (helper, filename, flags, mode);
+ if (size < 0)
+ return -1;
+
+ if (mnsh_recv_fd (helper, &fd, &error) != 0)
+ return -1;
+
+ if (fd < 0)
+ errno = error;
+
+ return fd;
+}
+
+/* See nat/linux-namespaces.h. */
+
+int
+linux_mntns_unlink (pid_t pid, const char *filename)
+{
+ enum mnsh_fs_code access = linux_mntns_access_fs (pid);
+ struct linux_mnsh *helper;
+ int ret, error;
+ ssize_t size;
+
+ if (access == MNSH_FS_ERROR)
+ return -1;
+
+ if (access == MNSH_FS_DIRECT)
+ return unlink (filename);
+
+ gdb_assert (access == MNSH_FS_HELPER);
+
+ helper = linux_mntns_get_helper ();
+
+ size = mnsh_send_unlink (helper, filename);
+ if (size < 0)
+ return -1;
+
+ if (mnsh_recv_int (helper, &ret, &error) != 0)
+ return -1;
+
+ if (ret != 0)
+ errno = error;
+
+ return ret;
+}
+
+/* See nat/linux-namespaces.h. */
+
+ssize_t
+linux_mntns_readlink (pid_t pid, const char *filename,
+ char *buf, size_t bufsiz)
+{
+ enum mnsh_fs_code access = linux_mntns_access_fs (pid);
+ struct linux_mnsh *helper;
+ int ret, error;
+ ssize_t size;
+
+ if (access == MNSH_FS_ERROR)
+ return -1;
+
+ if (access == MNSH_FS_DIRECT)
+ return readlink (filename, buf, bufsiz);
+
+ gdb_assert (access == MNSH_FS_HELPER);
+
+ helper = linux_mntns_get_helper ();
+
+ size = mnsh_send_readlink (helper, filename);
+ if (size < 0)
+ return -1;
+
+ size = mnsh_recv_intstr (helper, &ret, &error, buf, bufsiz);
+
+ if (size < 0)
+ {
+ ret = -1;
+ errno = error;
+ }
+ else
+ gdb_assert (size == ret);
+
+ return ret;
+}
projects / deliverable / binutils-gdb.git / commitdiff
