otcore: add debug logging capability for ostree-prepare-root

This commit introduces a new function, proc_cmdline_has_key, to check for
specific keys in the kernel command line. Additionally, it adds a debug
logging mechanism in ostree-prepare-root.c, which is controlled by the
presence of the "ostree-prepare-root.debug" key in the kernel command line.

These changes provide enhanced visibility into the mounting process,
aiding in troubleshooting.

Signed-off-by: Eric Curtin <ecurtin@redhat.com>

src/libotcore/otcore-prepare-root.c

@@ -25,6 +25,24 @@
 // which can be used to fully verify the target filesystem tree.
 #define BINDING_KEYPATH "/etc/ostree/initramfs-root-binding.key"
 
+bool
+proc_cmdline_has_key (const char *cmdline, const char *key)
+{
+  for (const char *iter = cmdline; iter;)
+    {
+      if (g_str_equal (iter, key))
+        return true;
+
+      iter = strchr (iter, ' ');
+      if (iter == NULL)
+        return false;
+
+      iter += strspn (iter, " ");
+    }
+
+  return false;
+}
+
 static bool
 proc_cmdline_has_key_starting_with (const char *cmdline, const char *key)
 {

src/libotcore/otcore.h

@@ -43,6 +43,7 @@ bool otcore_ed25519_init (void);
 gboolean otcore_validate_ed25519_signature (GBytes *data, GBytes *pubkey, GBytes *signature,
                                             bool *out_valid, GError **error);
 
+bool proc_cmdline_has_key (const char *cmdline, const char *key);
 char *otcore_find_proc_cmdline_key (const char *cmdline, const char *key);
 gboolean otcore_get_ostree_target (const char *cmdline, gboolean *is_aboot, char **out_target,
                                    GError **error);

src/switchroot/ostree-prepare-root.c

@@ -97,6 +97,20 @@
 
 #include "ostree-mount-util.h"
 
+static bool enable_debug = false;
+
+__attribute__ ((__format__ (printf, 1, 2))) static void
+dbg (const char *format, ...)
+{
+  if (enable_debug)
+    {
+      va_list args;
+      va_start (args, format);
+      vprintf (format, args);
+      va_end (args);
+    }
+}
+
 static bool
 sysroot_is_configured_ro (const char *sysroot)
 {
@@ -124,6 +138,7 @@ resolve_deploy_path (const char *root_mountpoint)
 
   g_autoptr (GError) error = NULL;
   g_autofree char *ostree_target = NULL;
+  enable_debug = proc_cmdline_has_key (kernel_cmdline, "ostree-prepare-root.debug");
   if (!otcore_get_ostree_target (kernel_cmdline, NULL, &ostree_target, &error))
     errx (EXIT_FAILURE, "Failed to determine ostree target: %s", error->message);
   if (!ostree_target)
@@ -564,6 +579,8 @@ main (int argc, char *argv[])
 
           g_autofree char *ovl_options
               = g_strdup_printf ("lowerdir=%s,upperdir=%s,workdir=%s", lowerdir, upperdir, workdir);
+          dbg ("mount (\"overlay\", \"" TMP_SYSROOT "/etc\", \"overlay\", MS_SILENT, \"%s\")\n",
+               ovl_options);
           if (mount ("overlay", TMP_SYSROOT "/etc", "overlay", MS_SILENT, ovl_options) < 0)
             err (EXIT_FAILURE, "failed to mount transient etc overlayfs");
         }
@@ -598,6 +615,9 @@ main (int argc, char *argv[])
       // Propagate readonly state
       if (!sysroot_currently_writable)
         mflags |= MS_RDONLY;
+
+      dbg ("mount (\"overlay\", \"" TMP_SYSROOT "/usr\", \"overlay\", %lu, \"%s\")\n", mflags,
+           usr_ovl_options);
       if (mount ("overlay", TMP_SYSROOT "/usr", "overlay", mflags, usr_ovl_options) < 0)
         err (EXIT_FAILURE, "failed to mount /usr overlayfs");
     }