init: Add maintenance shell

Signed-off-by: Ian Moffett <ian@osmora.org>

4 files changed, 214 insertions, 2 deletions

diff --git a/usr.sbin/init/Makefile b/usr.sbin/init/Makefile
index 13ac173..1bf7718 100644
--- a/usr.sbin/init/Makefile
+++ b/usr.sbin/init/Makefile
@@ -3,4 +3,4 @@ include ../sbin.mk
 .PHONY: all
 all:
 	@ # $(CC) -pie -nostdlib main.c -o init -e main
-	$(CC) main.c -o init $(INTERNAL_CFLAGS)
+	$(CC) main.c mshell.c -o init $(INTERNAL_CFLAGS)
diff --git a/usr.sbin/init/main.c b/usr.sbin/init/main.c
index 754b98e..4a7176c 100644
--- a/usr.sbin/init/main.c
+++ b/usr.sbin/init/main.c
@@ -28,6 +28,7 @@
  */
 
 #include <stdio.h>
+#include "mshell.h"
 
 #define VERSION "v0.0.1"
 
@@ -43,7 +44,11 @@ int
 main(int argc, char **argv)
 {
     loginfo("Hyra init " VERSION " loaded\n");
-    loginfo("Hello, World!\n");
+    loginfo("Dropping into maintenance shell...\n");
+
+    if (mshell_enter() != 0)
+        loginfo("Failed to launch mshell!\n");
+
     loginfo("** EXITING 0 **\n");
     return 0;
 }
diff --git a/usr.sbin/init/mshell.c b/usr.sbin/init/mshell.c
new file mode 100644
index 0000000..78c3a82
--- /dev/null
+++ b/usr.sbin/init/mshell.c
@@ -0,0 +1,172 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* Maintenance shell */
+
+#include <sys/reboot.h>
+#include <sys/auxv.h>
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <termios.h>
+#include "mshell.h"
+
+#define INPUT_SIZE 32
+#define TTY_DEV "/dev/tty1"
+#define PROMPT "mshell> "
+
+struct mshell_state {
+    uint8_t running : 1;
+    char input[INPUT_SIZE];
+};
+
+static void
+help(void)
+{
+    printf(
+        "MSHELL COMMANDS\n"
+        "\thelp - show this message\n"
+        "\treboot - reboot the system\n"
+        "\ttty - show the current TTY\n"
+        "\tpagesize - get the current page size\n"
+        "\texit - exit the shell\n"
+    );
+}
+
+static void
+parse_input(struct mshell_state *state)
+{
+    char cmd[INPUT_SIZE];
+    char *p = &state->input[0];
+    size_t cmd_idx = 0;
+
+    /* Skip leading whitespace */
+    while (*p && *p == ' ')
+        ++p;
+
+    /* Push the command */
+    while (*p && *p != '\n')
+        cmd[cmd_idx++] = *p++;
+
+    cmd[cmd_idx] = '\0';
+
+    if (strcmp(cmd, "reboot") == 0) {
+        reboot(REBOOT_DEFAULT);
+    } else if (strcmp(cmd, "pagesize") == 0) {
+        printf("%d\n", auxv_entry(AT_PAGESIZE));
+    } else if (strcmp(cmd, "tty") == 0) {
+        printf("%s\n", TTY_DEV);
+    } else if (strcmp(cmd, "help") == 0) {
+        help();
+    } else if (strcmp(cmd, "exit") == 0) {
+        state->running = 0;
+    } else {
+        printf("Unknown command '%s'\n", cmd);
+        printf("Use 'help' for help\n");
+    }
+}
+
+int
+mshell_enter(void)
+{
+    int fd, tmp;
+    size_t input_idx;
+    struct termios tm_old, tm;
+    struct mshell_state state = {
+        .running = 1
+    };
+
+    /* Try opening the TTY */
+    fd = open(TTY_DEV, O_RDONLY);
+    if (fd < 0)
+        return -1;
+
+    /* Set raw mode */
+    tcgetattr(fd, &tm_old);
+    tm = tm_old;
+    tm.c_lflag &= ~(ICANON | ECHO);
+    tcsetattr(fd, 0, &tm);
+
+    printf("%s", PROMPT);
+    input_idx = 0;
+
+    while (state.running) {
+        if (read(fd, &tmp, 1) <= 0)
+            continue;
+
+        switch (tmp) {
+        case '\n':
+            /*
+             * Parse the input, the newline is so that any printed
+             * text that is the result of a command can have
+             * its own lines.
+             */
+            printf("\n");
+            parse_input(&state);
+
+            /* Reset the buffer */
+            input_idx = 0;
+            state.input[0] = '\0';
+
+            printf("%s", PROMPT);
+            fflush(stdout);
+            break;
+        case '\b':
+            if (input_idx > 0) {
+                /*
+                 * Replace the last char with a '\0' and rewrite
+                 * the prompt.
+                 */
+                state.input[--input_idx] = '\0';
+                printf("\b");
+                fflush(stdout);
+                continue;
+            }
+
+            break;
+        default:
+            if (input_idx < INPUT_SIZE) {
+                state.input[input_idx++] = tmp;
+                state.input[input_idx] = '\0';
+
+                printf("%c", tmp);
+                fflush(stdout);
+            }
+
+            break;
+        }
+
+    }
+
+    /* Restore TTY state */
+    tcsetattr(fd, 0, &tm_old);
+    close(fd);
+    return 0;
+}
diff --git a/usr.sbin/init/mshell.h b/usr.sbin/init/mshell.h
new file mode 100644
index 0000000..9e9b456
--- /dev/null
+++ b/usr.sbin/init/mshell.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef MSHELL_H
+#define MSHELL_H
+
+int  mshell_enter(void);
+
+#endif  /* MSHELL_H */