ostree: Add command admin nsenter

Makefile-ostree.am

@@ -86,6 +86,7 @@ ostree_SOURCES += \
 	src/ostree/ot-admin-builtin-upgrade.c \
 	src/ostree/ot-admin-builtin-unlock.c \
 	src/ostree/ot-admin-builtin-state-overlay.c \
+	src/ostree/ot-admin-builtin-nsenter.c \
 	src/ostree/ot-admin-builtins.h \
 	src/ostree/ot-admin-instutil-builtin-selinux-ensure-labeled.c \
 	src/ostree/ot-admin-instutil-builtin-set-kargs.c \

src/ostree/ot-admin-builtin-nsenter.c

@@ -0,0 +1,122 @@
+/*
+* Copyright (C) 2024 Colin Walters <[email protected]>
+ *
+ * SPDX-License-Identifier: LGPL-2.0+
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * Author: Misaki Kasumi <[email protected]>
+ */
+
+#include "config.h"
+
+#include "libglnx.h"
+#include "ostree.h"
+#include "ot-admin-builtins.h"
+#include "ot-admin-functions.h"
+
+#include <spawn.h>
+#include <sys/wait.h>
+
+static gboolean opt_lock;
+
+static GOptionEntry options[] = {
+        { "lock", 0, 0, G_OPTION_ARG_NONE, &opt_lock,
+          "Make /sysroot writable in the mount namespace and acquire an exclusive multi-process write lock", NULL },
+        { NULL } };
+
+gboolean
+ot_admin_builtin_nsenter (int argc, char **argv, OstreeCommandInvocation *invocation,
+                         GCancellable *cancellable, GError **error)
+{
+  g_autoptr (GOptionContext) context = NULL;
+  g_autoptr (OstreeSysroot) sysroot = NULL;
+  g_autofree char **arguments = NULL;
+
+  context = g_option_context_new ("[PROGRAM [ARGUMENTS...]]");
+
+  int new_argc = argc;
+  char **new_argv = argv;
+
+  for (int i = 1; i < argc; i++)
+    {
+      if (g_str_equal (argv[i], "--"))
+        {
+          new_argc -= i;
+          argc = i;
+          new_argv = argv + i;
+          argv[i] = NULL;
+          break;
+        }
+    }
+
+  if (!ostree_admin_option_context_parse (context, options, &argc, &argv,
+                                          OSTREE_ADMIN_BUILTIN_FLAG_UNLOCKED, invocation, &sysroot,
+                                          cancellable, error))
+    return FALSE;
+
+  argc = new_argc;
+  argv = new_argv;
+  if (argc <= 1)
+    {
+      arguments = g_malloc_n (2, sizeof (char *));
+      if ((arguments[0] = getenv ("SHELL")) == NULL)
+        arguments[0] = "/bin/sh";
+      arguments[1] = NULL;
+    }
+  else
+    {
+      arguments = g_malloc_n (argc, sizeof (char *));
+      memcpy (arguments, argv + 1, (argc - 1) * sizeof (char *));
+      arguments[argc - 1] = NULL;
+    }
+
+  if (opt_lock)
+    {
+      if (!ostree_sysroot_lock (sysroot, error))
+        return FALSE;
+    }
+
+  pid_t child_pid;
+  if (posix_spawnp (&child_pid, arguments[0], NULL, NULL, arguments, environ) != 0)
+    {
+      glnx_throw_errno_prefix (error, "posix_spawnp");
+      return FALSE;
+    }
+
+  int status;
+  while (waitpid (child_pid, &status, 0) < 0)
+    {
+      if (errno != EINTR)
+        {
+          glnx_throw_errno_prefix (error, "waitpid");
+          return FALSE;
+        }
+    }
+
+  if (opt_lock)
+    ostree_sysroot_unlock (sysroot);
+
+  if (!WIFEXITED (status))
+    {
+      glnx_throw (error, "child process killed by signal");
+      return FALSE;
+    }
+
+  int exit_status = WEXITSTATUS (status);
+  if (exit_status != EXIT_SUCCESS)
+    exit (exit_status);
+
+  return TRUE;
+}

src/ostree/ot-admin-builtins.h

@@ -51,6 +51,7 @@ BUILTINPROTO (kargs);
 BUILTINPROTO (post_copy);
 BUILTINPROTO (lock_finalization);
 BUILTINPROTO (state_overlay);
+BUILTINPROTO (nsenter);
 
 #undef BUILTINPROTO
 

src/ostree/ot-builtin-admin.c

@@ -70,6 +70,8 @@ static OstreeCommand admin_subcommands[] = {
   { "upgrade", OSTREE_BUILTIN_FLAG_NO_REPO, ot_admin_builtin_upgrade,
     "Construct new tree from current origin and deploy it, if it changed" },
   { "kargs", OSTREE_BUILTIN_FLAG_NO_REPO, ot_admin_builtin_kargs, "Change kernel arguments" },
+  {"nsenter", OSTREE_BUILTIN_FLAG_NO_REPO | OSTREE_BUILTIN_FLAG_HIDDEN, ot_admin_builtin_nsenter,
+    "Run program in the mount namespace where /sysroot is present"},
   { NULL, 0, NULL, NULL }
 };
 
@@ -121,11 +123,6 @@ ostree_builtin_admin (int argc, char **argv, OstreeCommandInvocation *invocation
             }
         }
 
-      else if (g_str_equal (argv[in], "--"))
-        {
-          break;
-        }
-
       argv[out] = argv[in];
     }