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Diffstat (limited to '')
| -rw-r--r-- | src/mds-vt.c | 371 |
1 files changed, 371 insertions, 0 deletions
diff --git a/src/mds-vt.c b/src/mds-vt.c new file mode 100644 index 0000000..2167fb1 --- /dev/null +++ b/src/mds-vt.c @@ -0,0 +1,371 @@ +/** + * mds — A micro-display server + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * 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 "mds-vt.h" + +#include <libmdsserver/macros.h> +#include <libmdsserver/util.h> +#include <libmdsserver/mds-message.h> + +#include <errno.h> +#include <inttypes.h> +#include <string.h> +#include <stdio.h> +#include <stdlib.h> +#include <sys/ioctl.h> +#include <linux/kd.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <unistd.h> +#include <signal.h> +#define reconnect_to_display() -1 /* TODO */ + + + +#define MDS_VT_VARS_VERSION 0 + + + +/** + * This variable should declared by the actual server implementation. + * It must be configured before `main` is invoked. + * + * This tells the server-base how to behave + */ +server_characteristics_t server_characteristics = + { + .require_privileges = 1, /* we want to open the new tty (the rest is fine without root for some reason) */ + .require_display = 1, + .require_respawn_info = 0, + .sanity_check_argc = 1, + .fork_for_safety = 0, + .danger_is_deadly = 0 + }; + + + +/** + * Value of the ‘Message ID’ header for the next message + */ +static int32_t message_id = 1; + +/** + * Buffer for received messages + */ +static mds_message_t received; + +/** + * Whether the server is connected to the display + */ +static int connected = 1; + + + +/** + * This function will be invoked before `initialise_server` (if not re-exec:ing) + * or before `unmarshal_server` (if re-exec:ing) + * + * @return Non-zero on error + */ +int __attribute__((const)) preinitialise_server(void) +{ + return 0; +} + + +/** + * This function should initialise the server, + * and it not invoked after a re-exec. + * + * @return Non-zero on error + */ +int initialise_server(void) +{ + const char* const message = + "Command: intercept\n" + "Message ID: 0\n" + "Length: 14\n" + "\n" + "Command: echo\n"; + + if (full_send(message, strlen(message))) + return 1; + fail_if (server_initialised() < 0); + fail_if (mds_message_initialise(&received)); + + return 0; + pfail: + xperror(*argv); + mds_message_destroy(&received); + return 1; +} + + +/** + * This function will be invoked after `initialise_server` (if not re-exec:ing) + * or after `unmarshal_server` (if re-exec:ing) + * + * @return Non-zero on error + */ +int postinitialise_server(void) +{ + if (connected) + return 0; + + if (reconnect_to_display()) + { + mds_message_destroy(&received); + return 1; + } + connected = 1; + return 0; +} + + +/** + * Calculate the number of bytes that will be stored by `marshal_server` + * + * On failure the program should `abort()` or exit by other means. + * However it should not be possible for this function to fail. + * + * @return The number of bytes that will be stored by `marshal_server` + */ +size_t marshal_server_size(void) +{ + return 2 * sizeof(int) + sizeof(int32_t) + mds_message_marshal_size(&received); +} + + +/** + * Marshal server implementation specific data into a buffer + * + * @param state_buf The buffer for the marshalled data + * @return Non-zero on error + */ +int marshal_server(char* state_buf) +{ + buf_set_next(state_buf, int, MDS_VT_VARS_VERSION); + buf_set_next(state_buf, int, connected); + buf_set_next(state_buf, int32_t, message_id); + mds_message_marshal(&received, state_buf); + + mds_message_destroy(&received); + return 0; +} + + +/** + * Unmarshal server implementation specific data and update the servers state accordingly + * + * On critical failure the program should `abort()` or exit by other means. + * That is, do not let `reexec_failure_recover` run successfully, if it unrecoverable + * error has occurred or one severe enough that it is better to simply respawn. + * + * @param state_buf The marshalled data that as not been read already + * @return Non-zero on error + */ +int unmarshal_server(char* state_buf) +{ + int r; + /* buf_get_next(state_buf, int, MDS_VT_VARS_VERSION); */ + buf_next(state_buf, int, 1); + buf_get_next(state_buf, int, connected); + buf_get_next(state_buf, int32_t, message_id); + r = mds_message_unmarshal(&received, state_buf); + if (r) + { + xperror(*argv); + mds_message_destroy(&received); + } + return r; +} + + +/** + * Attempt to recover from a re-exec failure that has been + * detected after the server successfully updated it execution image + * + * @return Non-zero on error + */ +int __attribute__((const)) reexec_failure_recover(void) +{ + return -1; +} + + +/** + * Perform the server's mission + * + * @return Non-zero on error + */ +int master_loop(void) +{ + int rc = 1; + + while (!reexecing && !terminating) + { + int r = mds_message_read(&received, socket_fd); + if (r == 0) + { + r = 0; /* FIXME */ + if (r == 0) + continue; + } + + if (r == -2) + { + eprint("corrupt message received, aborting."); + goto fail; + } + else if (errno == EINTR) + continue; + else if (errno != ECONNRESET) + goto pfail; + + eprint("lost connection to server."); + mds_message_destroy(&received); + mds_message_initialise(&received); + connected = 0; + if (reconnect_to_display()) + goto fail; + connected = 1; + } + + rc = 0; + goto fail; + pfail: + xperror(*argv); + fail: + if (rc || !reexecing) + mds_message_destroy(&received); + return rc; +} + + +/** + * Send a full message even if interrupted + * + * @param message The message to send + * @param length The length of the message + * @return Non-zero on success + */ +int full_send(const char* message, size_t length) +{ + size_t sent; + + while (length > 0) + { + sent = send_message(socket_fd, message, length); + if (sent > length) + { + eprint("Sent more of a message than exists in the message, aborting."); + return -1; + } + else if ((sent < length) && (errno != EINTR)) + { + xperror(*argv); + return -1; + } + message += sent; + length -= sent; + } + return 0; +} + + +/** + * Get the index of the next available virtual terminal + * + * @return -1 on error, 0 if the terminals are exhausted, otherwise the next terminal + */ +int vt_get_next_available(void) +{ + int next_vt = -1; + int r = ioctl(STDIN_FILENO, VT_OPENQRY, &next_vt); + if (r < 0) + return r; + return ((next_vt < 0) || (MAX_NR_CONSOLES < next_vt)) ? 0 : next_vt; +} + + +/** + * Get the currently active virtual terminal + * + * @return -1 on error, otherwise the current terminal + */ +int vt_get_active(void) +{ + struct vt_stat state; + if (ioctl(STDIN_FILENO, VT_GETSTATE, &state) < 0) + return -1; + return state.v_active; +} + + +/** + * Change currently active virtual terminal and wait for it to complete the switch + * + * @param vt The index of the terminal + * @return Zero on success, -1 on error + */ +int vt_set_active(int vt) +{ + if (ioctl(STDIN_FILENO, VT_ACTIVATE, vt) < 0) + return -1; + + if (ioctl(STDIN_FILENO, VT_WAITACTIVE, vt) < 0) + xperror(*argv); + + return 0; +} + + +/** + * Open a virtual terminal + * + * @param vt The index of the terminal + * @return The file descriptor for the terminal, -1 on error + */ +int vt_open(int vt) +{ + char vtpath[64]; /* Should be small enought and large enought for any + lunatic alternative to /dev/ttyNNN, if not you + will need to apply a patch (or fix your system.) */ + sprintf(vtpath, VT_PATH_PATTERN, vt); + return open(vtpath, O_RDWR); +} + + +/** + * Construct a virtual terminal mode that can be used in `vt_get_set_mode` + * + * @param vt_switch_control Whether we want to be able to block and delay VT switches + * @param vt_leave_signal The signal that should be send to us we a process is trying + * to switch terminal to another terminal + * @param vt_enter_signal The signal that should be send to us we a process is trying + * to switch terminal to our terminal + * @param mode Output parameter + */ +void vt_construct_mode(int vt_switch_control, int vt_leave_signal, + int vt_enter_signal, struct vt_mode* restrict mode) +{ + mode->mode = vt_switch_control ? VT_PROCESS : VT_AUTO; + mode->waitv = 0; + mode->relsig = (short int)vt_leave_signal; + mode->acqsig = (short int)vt_enter_signal; +} + |