Add serial communication program

Makefile

@@ -22,7 +22,8 @@ STAGE_BIN=$(STAGE)/init \
 		  $(STAGE)/bin/mkdir \
 		  $(STAGE)/bin/login \
 		  $(STAGE)/bin/ase \
-		  $(STAGE)/bin/su
+		  $(STAGE)/bin/su \
+		  $(STAGE)/bin/com
 sh_OBJS=$(O)/sh/sh.o \
 		$(O)/sh/readline.o \
 		$(O)/sh/builtin.o \

core/bin/com.c

@@ -0,0 +1,128 @@
+#include <sys/select.h>
+#include <termios.h>
+#include <unistd.h>
+#include <string.h>
+#include <signal.h>
+#include <errno.h>
+#include <stdio.h>
+
+// TODO: baud rate support in kernel
+static int ready = 0, there_fd;
+static struct termios here_tc, here_tc_old;
+static struct termios there_tc, there_tc_old;
+
+static void sig_handler(int signum) {
+    // Restore old termios
+    if (ready) {
+        printf("Interrupted\n");
+        tcsetattr(STDIN_FILENO, TCSANOW, &here_tc_old);
+        tcsetattr(there_fd, TCSANOW, &there_tc_old);
+    }
+    exit(0);
+}
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        printf("Usage: com /dev/ttySn\n");
+        return -1;
+    }
+
+    signal(SIGINT, sig_handler);
+
+    char buf[512];
+    fd_set fds;
+    ssize_t len;
+    int res;
+
+    if ((there_fd = open(argv[1], O_RDWR, 0)) < 0) {
+        perror(argv[1]);
+        return -1;
+    }
+
+    if (tcgetattr(STDIN_FILENO, &here_tc_old)) {
+        perror("stdin");
+        close(there_fd);
+        return -1;
+    }
+
+    if (tcgetattr(there_fd, &there_tc_old) != 0) {
+        perror(argv[1]);
+        close(there_fd);
+        return -1;
+    }
+
+    ready = 1;
+
+    // Make them both raw
+    memcpy(&here_tc, &here_tc_old, sizeof(struct termios));
+    memcpy(&there_tc, &there_tc_old, sizeof(struct termios));
+
+    here_tc.c_iflag &= ~ICANON;
+    here_tc.c_lflag &= ~ECHO;
+    there_tc.c_iflag &= ~ICANON;
+    there_tc.c_lflag &= ~ECHO;
+
+    res = -1;
+
+    if (tcsetattr(STDIN_FILENO, TCSANOW, &here_tc) != 0) {
+        perror("stdin");
+        goto cleanup;
+    }
+
+    if (tcsetattr(there_fd, TCSANOW, &there_tc) != 0) {
+        perror(argv[1]);
+        goto cleanup;
+    }
+
+    while (1) {
+        FD_ZERO(&fds);
+        FD_SET(STDIN_FILENO, &fds);
+        FD_SET(there_fd, &fds);
+
+        if ((res = select(there_fd + 1, &fds, NULL, NULL, NULL)) < 0) {
+            goto cleanup;
+        }
+
+        if (FD_ISSET(STDIN_FILENO, &fds)) {
+            if ((len = read(STDIN_FILENO, buf, sizeof(buf))) <= 0) {
+                if (len != 0) {
+                    perror("read()");
+                    res = -1;
+                }
+                goto cleanup;
+            }
+
+            if (write(there_fd, buf, len) != len) {
+                perror("write()");
+                res = -1;
+                goto cleanup;
+            }
+        }
+        if (FD_ISSET(there_fd, &fds)) {
+            if ((len = read(there_fd, buf, sizeof(buf))) <= 0) {
+                if (len == 0) {
+                    printf("Remote side hang up\n");
+                } else {
+                    perror("read()");
+                    res = -1;
+                }
+                goto cleanup;
+            }
+
+            if (write(STDOUT_FILENO, buf, len) != len) {
+                perror("write()");
+                res = -1;
+                goto cleanup;
+            }
+        }
+    }
+
+    res = 0;
+cleanup:
+    tcsetattr(there_fd, TCSANOW, &there_tc_old);
+    tcsetattr(STDIN_FILENO, TCSANOW, &here_tc_old);
+    close(there_fd);
+    ready = 0;
+
+    return 0;
+}