feat: login - write system log to disk (0:/os/logs/montaukos) during shutdown, limit disk flush stage to non-ramdisk storage devices

programs/src/login/login_shutdown.cpp

@@ -9,6 +9,11 @@
 
 using namespace gui;
 
+bool volume0_is_persistent() {
+    if (montauk::drivekind(0) == 0) return false;
+    return true;
+}
+
 // Minimum time each shutdown stage stays on screen, so the status message is
 // readable even when the underlying work completes near-instantly.
 static constexpr uint64_t STAGE_MIN_VISIBLE_MS = 600;
@@ -23,6 +28,7 @@ static constexpr uint64_t STAGE_MIN_VISIBLE_MS = 600;
 //    wedged storage controller hits this bound.
 static constexpr uint64_t BT_STAGE_TIMEOUT_MS = 4000;
 static constexpr uint64_t FS_STAGE_TIMEOUT_MS = 10000;
+static constexpr uint64_t LOG_WRITE_TIMEOUT_MS = 10000;
 
 void draw_shutdown_screen(LoginState* ls, const char* heading, const char* status) {
     Framebuffer& fb = ls->fb;
@@ -171,6 +177,39 @@ void stage_disconnect_bluetooth() {
     }
 }
 
+static bool path_is_file(const char* path) {
+    montauk::abi::FileStat st;
+    if (montauk::stat(path, &st) < 0) return false;
+
+    return !st.isDir;
+}
+
+#define LOG_READ_SIZE 65536
+
+// Write the system log to a file on disk
+void stage_save_log() {
+    // Edge case - 0:/os/logs exists and is a file
+    if (path_is_file("0:/os/logs"))
+        return;
+
+    montauk::fmkdir("0:/os/logs");
+
+    // Clear any existing montaukos log 
+    montauk::fdelete("0:/os/logs/montaukos");
+
+    int handle = montauk::fcreate("0:/os/logs/montaukos");
+    if (handle < 0)
+        return;
+
+    uint8_t* syslog_buf = (uint8_t*)montauk::malloc(LOG_READ_SIZE);
+    int n = montauk::read_log((char *)syslog_buf, LOG_READ_SIZE);
+
+    int result = montauk::fwrite(handle, syslog_buf, 0, n);
+    
+    montauk::close(handle);
+    montauk::mfree(syslog_buf);
+}
+
 void stage_flush_filesystems() {
     montauk::fs_sync();
 }
@@ -193,13 +232,23 @@ void perform_graceful_shutdown(LoginState* ls, int action) {
         }
     }
 
-    // ==== Stage 2: flush writes and unmount filesystems ====
-    show_stage(ls, heading, "Flushing file systems...");
-    if (!run_stage(stage_flush_filesystems, FS_STAGE_TIMEOUT_MS)) {
-        show_stage(ls, heading, "Storage is unresponsive, continuing...");
+    // No need to save log files or flush to disk if volume 0 is a ramdisk anyway
+    if (volume0_is_persistent()) {
+        // ==== Stage 2: write system log to disk ====
+        show_stage(ls, heading, "Saving system log...");
+        if (!run_stage(stage_save_log, LOG_WRITE_TIMEOUT_MS)) {
+            show_stage(ls, heading, "Log save is unresponsive, continuing...");
+        } 
+
+        // ==== Stage 3: flush writes and unmount filesystems ====
+        show_stage(ls, heading, "Flushing file systems...");
+        if (!run_stage(stage_flush_filesystems, FS_STAGE_TIMEOUT_MS)) {
+            show_stage(ls, heading, "Storage is unresponsive, continuing...");
+        }
     }
 
-    // ==== Stage 3: dispatch the ACPI power-off / reset ====
+
+    // ==== Stage 4: dispatch the ACPI power-off / reset ====
     show_stage(ls, heading, rebooting ? "Restarting now..." : "Powering off...");
     if (rebooting) {
         montauk::reset();