debug-generator: add new generator

debug-generator can mask specific units if they are specified on the
kernel command line with systemd.mask=.

debug-generator can pull in debug-shell.service is systemd.debug-shell
is passed on the kernel command line.

.gitignore

@@ -60,6 +60,7 @@
 /systemd-cryptsetup
 /systemd-cryptsetup-generator
 /systemd-dbus1-generator
+/systemd-debug-generator
 /systemd-delta
 /systemd-detect-virt
 /systemd-efi-boot-generator

Makefile.am

@@ -371,7 +371,8 @@ rootlibexec_PROGRAMS = \
 systemgenerator_PROGRAMS = \
 	systemd-getty-generator \
 	systemd-fstab-generator \
-	systemd-system-update-generator
+	systemd-system-update-generator \
+	systemd-debug-generator
 
 dist_bashcompletion_DATA = \
 	shell-completion/bash/busctl \
@@ -1891,6 +1892,14 @@ systemd_getty_generator_LDADD = \
 	libsystemd-label.la \
 	libsystemd-shared.la
 
+# ------------------------------------------------------------------------------
+systemd_debug_generator_SOURCES = \
+	src/debug-generator/debug-generator.c
+
+systemd_debug_generator_LDADD = \
+	libsystemd-label.la \
+	libsystemd-shared.la
+
 # ------------------------------------------------------------------------------
 systemd_fstab_generator_SOURCES = \
 	src/fstab-generator/fstab-generator.c \

src/debug-generator/Makefile

@@ -0,0 +1 @@
+../Makefile

src/debug-generator/debug-generator.c

@@ -0,0 +1,137 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd 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 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "util.h"
+#include "strv.h"
+#include "unit-name.h"
+#include "mkdir.h"
+
+static const char *arg_dest = "/tmp";
+static char **arg_mask = NULL;
+static bool arg_debug_shell = false;
+
+static int parse_proc_cmdline_item(const char *key, const char *value) {
+        int r;
+
+        if (streq(key, "systemd.mask")) {
+
+                if (!value)
+                        log_error("Missing argument for systemd.mask= kernel command line parameter.");
+                else {
+                        char *n;
+
+                        n = strdup(value);
+                        if (!n)
+                                return log_oom();
+
+                        r = strv_consume(&arg_mask, n);
+                        if (r < 0)
+                                return log_oom();
+                }
+        } else if (streq(key, "systemd.debug-shell")) {
+
+                if (value) {
+                        r = parse_boolean(value);
+                        if (r < 0)
+                                log_error("Failed to parse systemd.debug-shell= argument '%s', ignoring.", value);
+                        else
+                                arg_debug_shell = r;
+                } else
+                        arg_debug_shell = true;
+        }
+
+        return 0;
+}
+
+static int generate_mask_symlinks(void) {
+        char **u;
+        int r = 0;
+
+        if (strv_isempty(arg_mask))
+                return 0;
+
+        STRV_FOREACH(u, arg_mask) {
+                _cleanup_free_ char *m = NULL, *p = NULL;
+
+                m = unit_name_mangle(*u, MANGLE_NOGLOB);
+                if (!m)
+                        return log_oom();
+
+                p = strjoin(arg_dest, "/", m, NULL);
+                if (!p)
+                        return log_oom();
+
+                if (symlink("/dev/null", p) < 0) {
+                        log_error("Failed to create mask symlink %s: %m", p);
+                        r = -errno;
+                }
+        }
+
+        return r;
+}
+
+static int generate_debug_shell_symlink(void) {
+        const char *p;
+
+        if (!arg_debug_shell)
+                return 0;
+
+        p = strappenda(arg_dest, "/default.target.wants/debug-shell.service");
+
+        mkdir_parents_label(p, 0755);
+
+        if (symlink(SYSTEM_DATA_UNIT_PATH "/debug-shell.service", p) < 0) {
+                log_error("Failed to create %s symlink: %m", p);
+                return -errno;
+        }
+
+        return 0;
+}
+
+int main(int argc, char *argv[]) {
+        int r, q;
+
+        if (argc > 1 && argc != 4) {
+                log_error("This program takes three or no arguments.");
+                return EXIT_FAILURE;
+        }
+
+        if (argc > 1)
+                arg_dest = argv[2];
+
+        log_set_target(LOG_TARGET_SAFE);
+        log_parse_environment();
+        log_open();
+
+        umask(0022);
+
+        if (parse_proc_cmdline(parse_proc_cmdline_item) < 0)
+                return EXIT_FAILURE;
+
+        r = generate_mask_symlinks();
+
+        q = generate_debug_shell_symlink();
+        if (q < 0)
+                r = q;
+
+        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+
+}