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examples/consoles: Support attaching consoles and pipes at runtime
Signed-off-by: Matej Hrica <mhrica@redhat.com>
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‎examples/consoles.c‎

Lines changed: 284 additions & 0 deletions
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdarg.h>
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#include <pthread.h>
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#include <poll.h>
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#include <sys/wait.h>
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#include <sys/stat.h>
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#include <libkrun.h>
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#define NUM_RESERVED_PORTS 64
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static int cmd_output(char *output, size_t output_size, const char *prog, ...)
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{
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va_list args;
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const char *argv[32];
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int argc = 0;
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int pipe_fds[2] = { -1, -1 };
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argv[argc++] = prog;
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va_start(args, prog);
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while (argc < 31) {
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const char *arg = va_arg(args, const char *);
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argv[argc++] = arg;
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if (arg == NULL) break;
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}
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va_end(args);
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argv[argc] = NULL;
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if (output && output_size > 0) {
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if (pipe(pipe_fds) < 0) return -1;
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}
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pid_t pid = fork();
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if (pid < 0) return -1;
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if (pid == 0) {
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if (pipe_fds[0] >= 0) {
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close(pipe_fds[0]);
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dup2(pipe_fds[1], STDOUT_FILENO);
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close(pipe_fds[1]);
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}
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execvp(prog, (char *const *)argv);
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abort();
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}
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if (pipe_fds[0] >= 0) {
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close(pipe_fds[1]);
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ssize_t n = read(pipe_fds[0], output, output_size - 1);
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close(pipe_fds[0]);
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if (n < 0) n = 0;
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output[n] = '\0';
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}
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int status;
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if (waitpid(pid, &status, 0) < 0) return -1;
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if (!WIFEXITED(status)) return -1;
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return WEXITSTATUS(status);
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}
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#define cmd(...) ({ char _d[1]; cmd_output(_d, 0, __VA_ARGS__); })
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static int create_tmux_tty(const char *session_name)
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{
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char tty_path[256];
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char wait_cmd[128];
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snprintf(wait_cmd, sizeof(wait_cmd), "waitpid %d", (int)getpid());
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if (cmd("tmux", "new-session", "-d", "-s", session_name, "sh", "-c", wait_cmd, NULL) != 0)
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return -1;
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char hook_cmd[128];
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snprintf(hook_cmd, sizeof(hook_cmd), "run-shell 'kill -WINCH %d'", (int)getpid());
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cmd("tmux", "set-hook", "-g", "client-resized", hook_cmd, NULL);
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if (cmd_output(tty_path, sizeof(tty_path), "tmux", "display-message", "-p", "-t", session_name, "#{pane_tty}", NULL) != 0)
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return -1;
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tty_path[strcspn(tty_path, "\n")] = '\0';
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int fd = open(tty_path, O_RDWR);
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if (fd < 0) return -1;
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return fd;
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}
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static int mkfifo_if_needed(const char *path)
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{
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if (mkfifo(path, 0666) < 0) {
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if (errno != EEXIST) return -1;
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}
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return 0;
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}
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static int create_fifo_inout(const char *fifo_in, const char *fifo_out, int *input_fd, int *output_fd)
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{
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if (mkfifo_if_needed(fifo_in) < 0) return -1;
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if (mkfifo_if_needed(fifo_out) < 0) return -1;
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*input_fd = open(fifo_in, O_RDWR | O_NONBLOCK);
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if (*input_fd < 0) return -1;
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*output_fd = open(fifo_out, O_RDWR | O_NONBLOCK);
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if (*output_fd < 0) {
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close(*input_fd);
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return -1;
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}
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return 0;
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}
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struct console_state {
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uint32_t ctx_id;
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uint32_t console_id;
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int ready_fd;
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};
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static void *dynamic_console_thread(void *arg)
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{
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struct console_state *state = arg;
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int ready_fd = state->ready_fd;
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struct pollfd pfd = { .fd = ready_fd, .events = POLLIN };
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fprintf(stderr, "Waiting for console device...\n");
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if (poll(&pfd, 1, -1) < 0) {
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perror("poll");
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return NULL;
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}
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uint64_t val;
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if (read(ready_fd, &val, sizeof(val)) != sizeof(val)) {
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perror("read eventfd");
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return NULL;
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}
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fprintf(stderr, "\n");
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fprintf(stderr, "=== VM Started ===\n");
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fprintf(stderr, "\n");
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fprintf(stderr, "*** To interact with the VM (hvc0), run in another terminal: ***\n");
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fprintf(stderr, " tmux attach -t krun-console-1\n");
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fprintf(stderr, "\n");
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fprintf(stderr, "Commands: 'c' = add console\n");
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fprintf(stderr, " 'p' = add pipe\n");
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fprintf(stderr, "\n");
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int console_count = 1; /* console-1 already exists (hvc0) */
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int pipe_count = 0;
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char line[16];
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while (1) {
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fprintf(stderr, "> ");
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if (fgets(line, sizeof(line), stdin) == NULL) break;
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if (line[0] == 'c' || line[0] == 'C') {
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console_count++;
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char sess[64], port[64];
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snprintf(sess, sizeof(sess), "krun-console-%d", console_count);
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snprintf(port, sizeof(port), "console-%d", console_count);
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int fd = create_tmux_tty(sess);
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if (fd < 0) { fprintf(stderr, "tmux: failed to create session '%s'\n", sess); continue; }
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int err = krun_add_console_port_tty(state->ctx_id, state->console_id, port, fd);
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if (err) { fprintf(stderr, "add port: %s\n", strerror(-err)); close(fd); continue; }
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fprintf(stderr, "Created console '%s' (port %d, /dev/hvc%d):\n", port, console_count + pipe_count - 1, console_count - 1);
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fprintf(stderr, " On host: tmux attach -t %s\n", sess);
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fprintf(stderr, " In guest: setsid /sbin/agetty -a $(whoami) -L hvc%d xterm-256color\n", console_count - 1);
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if (console_count + pipe_count > NUM_RESERVED_PORTS) {
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fprintf(stderr, "Reached max reserved ports (%d)\n", NUM_RESERVED_PORTS);
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break;
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}
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}
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if (line[0] == 'p' || line[0] == 'P') {
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pipe_count++;
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char port[64], fifo_in[128], fifo_out[128];
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snprintf(port, sizeof(port), "pipe-%d", pipe_count);
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snprintf(fifo_in, sizeof(fifo_in), "/tmp/krun_pipe%d_in", pipe_count);
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snprintf(fifo_out, sizeof(fifo_out), "/tmp/krun_pipe%d_out", pipe_count);
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int in_fd, out_fd;
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if (create_fifo_inout(fifo_in, fifo_out, &in_fd, &out_fd) < 0) {
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perror("create_fifo_inout"); continue;
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}
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int err = krun_add_console_port_inout(state->ctx_id, state->console_id, port, in_fd, out_fd);
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if (err) {
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fprintf(stderr, "add port: %s\n", strerror(-err));
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close(in_fd);
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close(out_fd);
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continue;
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}
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fprintf(stderr, "Created pipe '%s' (port %d):\n", port, console_count + pipe_count - 1);
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fprintf(stderr, " In guest: DEV=/dev/$(grep -l %s /sys/class/virtio-ports/*/name | cut -d/ -f5)\n", port);
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fprintf(stderr, " cat $DEV OR echo data > $DEV\n");
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fprintf(stderr, " On host: echo 'data' > %s # send to guest\n", fifo_in);
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fprintf(stderr, " cat %s # receive from guest\n", fifo_out);
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if (console_count + pipe_count > NUM_RESERVED_PORTS) {
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fprintf(stderr, "Reached max reserved ports (%d)\n", NUM_RESERVED_PORTS);
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break;
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}
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}
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}
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return NULL;
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}
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int main(int argc, char *const argv[])
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{
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if (argc < 3) {
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fprintf(stderr, "Usage: %s ROOT_DIR COMMAND [ARGS...]\n", argv[0]);
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return 1;
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}
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const char *root_dir = argv[1];
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const char *command = argv[2];
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const char *const *command_args = (argc > 3) ? (const char *const *)&argv[3] : NULL;
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const char *const envp[] = { 0 };
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krun_set_log_level(KRUN_LOG_LEVEL_DEBUG);
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int err;
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int ctx_id = krun_create_ctx();
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if (ctx_id < 0) { errno = -ctx_id; perror("krun_create_ctx"); return 1; }
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if ((err = krun_disable_implicit_console(ctx_id))) {
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errno = -err; perror("krun_disable_implicit_console"); return 1;
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}
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int console_id = krun_add_virtio_console_multiport(ctx_id);
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if (console_id < 0) {
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errno = -console_id; perror("krun_add_virtio_console_multiport"); return 1;
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}
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/* Create 1 initial console BEFORE VM starts - this will run the command */
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{
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int fd = create_tmux_tty("krun-console-1");
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if (fd < 0) { fprintf(stderr, "create_tmux_tty failed (session already exists?)\n"); return 1; }
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if ((err = krun_add_console_port_tty(ctx_id, console_id, "console-1", fd))) {
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errno = -err; perror("krun_add_console_port_tty"); return 1;
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}
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}
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/* Reserve ports for dynamic addition */
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if ((err = krun_console_reserve_ports(ctx_id, console_id, NUM_RESERVED_PORTS))) {
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errno = -err; perror("krun_console_reserve_ports"); return 1;
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}
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if ((err = krun_set_vm_config(ctx_id, 4, 4096))) {
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errno = -err; perror("krun_set_vm_config"); return 1;
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}
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if ((err = krun_set_root(ctx_id, root_dir))) {
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errno = -err; perror("krun_set_root"); return 1;
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}
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if ((err = krun_set_exec(ctx_id, command, command_args, envp))) {
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errno = -err; perror("krun_set_exec"); return 1;
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}
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fprintf(stderr, "\nStarting VM...\n");
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int ready_fd = krun_get_console_ready_fd(ctx_id, console_id);
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if (ready_fd < 0) {
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errno = -ready_fd; perror("krun_get_console_ready_fd"); return 1;
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}
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struct console_state state = {
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.ctx_id = ctx_id,
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.console_id = console_id,
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.ready_fd = ready_fd,
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};
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pthread_t dyn_thread;
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pthread_create(&dyn_thread, NULL, dynamic_console_thread, &state);
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pthread_detach(dyn_thread);
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/* Run VM in main thread - this blocks until VM exits, then calls _exit() */
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if ((err = krun_start_enter(ctx_id))) {
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errno = -err; perror("krun_start_enter"); return 1;
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}
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return 0;
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}

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