agent: fix agent panic running as init

We should mount procfs before trying to parse kernel command lines.

Fixes: #771
Signed-off-by: Peng Tao <bergwolf@hyper.sh>

src/agent/src/main.rs

@@ -126,15 +126,6 @@ fn main() -> Result<()> {
     let writer = unsafe { File::from_raw_fd(wfd) };
 
     let agentConfig = AGENT_CONFIG.clone();
-    // once parsed cmdline and set the config, release the write lock
-    // as soon as possible in case other thread would get read lock on
-    // it.
-    {
-        let mut config = agentConfig.write().unwrap();
-        config.parse_cmdline(KERNEL_CMDLINE_FILE)?;
-    }
-
-    let config = agentConfig.read().unwrap();
 
     let init_mode = unistd::getpid() == Pid::from_raw(1);
     if init_mode {
@@ -148,8 +139,25 @@ fn main() -> Result<()> {
         // since before do the base mount, it wouldn't access "/proc/cmdline"
         // to get the customzied debug level.
         let logger = logging::create_logger(NAME, "agent", slog::Level::Debug, writer);
+
+        // Must mount proc fs before parsing kernel command line
+        general_mount(&logger).map_err(|e| {
+            error!(logger, "fail general mount: {}", e);
+            e
+        })?;
+
+        let mut config = agentConfig.write().unwrap();
+        config.parse_cmdline(KERNEL_CMDLINE_FILE)?;
+
         init_agent_as_init(&logger, config.unified_cgroup_hierarchy)?;
+    } else {
+        // once parsed cmdline and set the config, release the write lock
+        // as soon as possible in case other thread would get read lock on
+        // it.
+        let mut config = agentConfig.write().unwrap();
+        config.parse_cmdline(KERNEL_CMDLINE_FILE)?;
     }
+    let config = agentConfig.read().unwrap();
 
     let log_vport = config.log_vport as u32;
     let log_handle = thread::spawn(move || -> Result<()> {
@@ -335,8 +343,13 @@ fn setup_signal_handler(logger: &Logger, sandbox: Arc<Mutex<Sandbox>>) -> Result
 // init_agent_as_init will do the initializations such as setting up the rootfs
 // when this agent has been run as the init process.
 fn init_agent_as_init(logger: &Logger, unified_cgroup_hierarchy: bool) -> Result<()> {
-    general_mount(logger)?;
+    cgroups_mount(logger, unified_cgroup_hierarchy).map_err(|e| {
-    cgroups_mount(logger, unified_cgroup_hierarchy)?;
+        error!(
+            logger,
+            "fail cgroups mount, unified_cgroup_hierarchy {}: {}", unified_cgroup_hierarchy, e
+        );
+        e
+    })?;
 
     fs::remove_file(Path::new("/dev/ptmx"))?;
     unixfs::symlink(Path::new("/dev/pts/ptmx"), Path::new("/dev/ptmx"))?;