pid1: propagate the original command line when reexecuting

When we reexec the manager in a container, we lose configuration settings on
the kernel command line:

  $ systemd-nspawn -M rawhide -b systemd.status-unit-format=name systemd.show-status=yes
  ...
  # tr '\0' ' ' </proc/1/cmdline
  /usr/lib/systemd/systemd systemd.status_unit_format=combined systemd.show-status=yes
  # sudo systemctl daemon-reexec
  # tr '\0' ' ' </proc/1/cmdline
  /usr/lib/systemd/systemd --system --deserialize 20

  This means that after daemon-reexec, the settings that we gain from the
  commandline are reset to defaults.

So let's reeexecute with the original arguments copied over, modulo some
filtering.

(cherry picked from commit 846f1da465beda990c1c01346311393f485df467)
(cherry picked from commit f3af6ba86c1128ccf6d6f896f70c22f9645a51c5)

1 files changed, 53 insertions, 10 deletions

diff --git a/src/core/main.c b/src/core/main.c
index 3ee8d0a869..fd3691f6f9 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1719,9 +1719,50 @@ static void update_numa_policy(bool skip_setup) {
                 log_warning_errno(r, "Failed to set NUMA memory policy: %m");
 }
 
+static void filter_args(const char* dst[], unsigned *pos, char **src, int argc) {
+        assert(dst);
+        assert(pos);
+
+        /* Copy some filtered arguments into the dst array from src. */
+        for (int i = 1; i < argc; i++) {
+                if (STR_IN_SET(src[i],
+                               "--switched-root",
+                               "--system",
+                               "--user"))
+                        continue;
+
+                if (startswith(src[i], "--deserialize="))
+                        continue;
+                if (streq(src[i], "--deserialize")) {
+                        i++;                            /* Skip the argument too */
+                        continue;
+                }
+
+                /* Skip target unit designators. We already acted upon this information and have queued
+                 * appropriate jobs. We don't want to redo all this after reexecution. */
+                if (startswith(src[i], "--unit="))
+                        continue;
+                if (streq(src[i], "--unit")) {
+                        i++;                            /* Skip the argument too */
+                        continue;
+                }
+
+                if (startswith(src[i],
+                               in_initrd() ? "rd.systemd.unit=" : "systemd.unit="))
+                        continue;
+
+                if (runlevel_to_target(src[i]))
+                        continue;
+
+                /* Seems we have a good old option. Let's pass it over to the new instance. */
+                dst[*pos] = src[i];
+                (*pos)++;
+        }
+}
+
 static void do_reexecute(
                 int argc,
-                char *argv[],
+                char* argv[],
                 const struct rlimit *saved_rlimit_nofile,
                 const struct rlimit *saved_rlimit_memlock,
                 FDSet *fds,
@@ -1729,7 +1770,7 @@ static void do_reexecute(
                 const char *switch_root_init,
                 const char **ret_error_message) {
 
-        unsigned i, j, args_size;
+        unsigned i, args_size;
         const char **args;
         int r;
 
@@ -1759,11 +1800,11 @@ static void do_reexecute(
                         log_error_errno(r, "Failed to switch root, trying to continue: %m");
         }
 
-        args_size = MAX(6, argc+1);
+        args_size = argc + 6;
         args = newa(const char*, args_size);
 
         if (!switch_root_init) {
-                char sfd[DECIMAL_STR_MAX(int) + 1];
+                char sfd[DECIMAL_STR_MAX(int)];
 
                 /* First try to spawn ourselves with the right path, and with full serialization. We do this only if
                  * the user didn't specify an explicit init to spawn. */
@@ -1773,8 +1814,9 @@ static void do_reexecute(
 
                 xsprintf(sfd, "%i", fileno(arg_serialization));
 
-                i = 0;
-                args[i++] = SYSTEMD_BINARY_PATH;
+                i = 1;         /* Leave args[0] empty for now. */
+                filter_args(args, &i, argv, argc);
+
                 if (switch_root_dir)
                         args[i++] = "--switched-root";
                 args[i++] = arg_system ? "--system" : "--user";
@@ -1792,8 +1834,9 @@ static void do_reexecute(
                  */
                 valgrind_summary_hack();
 
+                args[0] = SYSTEMD_BINARY_PATH;
                 (void) execv(args[0], (char* const*) args);
-                log_debug_errno(errno, "Failed to execute our own binary, trying fallback: %m");
+                log_debug_errno(errno, "Failed to execute our own binary %s, trying fallback: %m", args[0]);
         }
 
         /* Try the fallback, if there is any, without any serialization. We pass the original argv[] and envp[]. (Well,
@@ -1806,9 +1849,9 @@ static void do_reexecute(
         /* Reopen the console */
         (void) make_console_stdio();
 
-        for (j = 1, i = 1; j < (unsigned) argc; j++)
+        i = 1;         /* Leave args[0] empty for now. */
+        for (int j = 1; j <= argc; j++)
                 args[i++] = argv[j];
-        args[i++] = NULL;
         assert(i <= args_size);
 
         /* Re-enable any blocked signals, especially important if we switch from initial ramdisk to init=... */
@@ -1819,7 +1862,7 @@ static void do_reexecute(
         if (switch_root_init) {
                 args[0] = switch_root_init;
                 (void) execve(args[0], (char* const*) args, saved_env);
-                log_warning_errno(errno, "Failed to execute configured init, trying fallback: %m");
+                log_warning_errno(errno, "Failed to execute configured init %s, trying fallback: %m", args[0]);
         }
 
         args[0] = "/sbin/init";