core: parse rd.rescue and rd.emergency as initrd-specific shorthands (#3488)

Typing `rd.rescue` is easier than `rd.systemd.unit=rescue.target`.

man/kernel-command-line.xml

@@ -146,7 +146,9 @@
 
       <varlistentry>
         <term><varname>-b</varname></term>
+        <term><varname>rd.emergency</varname></term>
         <term><varname>emergency</varname></term>
+        <term><varname>rd.rescue</varname></term>
         <term><varname>rescue</varname></term>
         <term><varname>single</varname></term>
         <term><varname>s</varname></term>
@@ -158,7 +160,7 @@
         <term><varname>5</varname></term>
         <listitem>
           <para>Parameters understood by the system and service
-          manager, as compatibility options. For details, see
+          manager, as compatibility and convenience options. For details, see
           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
         </listitem>
       </varlistentry>

man/systemd.xml

@@ -1024,25 +1024,27 @@
 
       <varlistentry>
         <term><varname>emergency</varname></term>
+        <term><varname>rd.emergency</varname></term>
         <term><varname>-b</varname></term>
 
         <listitem><para>Boot into emergency mode. This is equivalent
-        to <varname>systemd.unit=emergency.target</varname> and
+        to <varname>systemd.unit=emergency.target</varname> or
-        provided for compatibility reasons and to be easier to
+        <varname>rd.systemd.unit=emergency.target</varname>, respectively, and
-        type.</para></listitem>
+        provided for compatibility reasons and to be easier to type.</para></listitem>
       </varlistentry>
 
       <varlistentry>
         <term><varname>rescue</varname></term>
+        <term><varname>rd.rescue</varname></term>
         <term><varname>single</varname></term>
         <term><varname>s</varname></term>
         <term><varname>S</varname></term>
         <term><varname>1</varname></term>
 
         <listitem><para>Boot into rescue mode. This is equivalent to
-        <varname>systemd.unit=rescue.target</varname> and provided for
+        <varname>systemd.unit=rescue.target</varname> or
-        compatibility reasons and to be easier to
+        <varname>rd.systemd.unit=rescue.target</varname>, respectively, and
-        type.</para></listitem>
+        provided for compatibility reasons and to be easier to type.</para></listitem>
       </varlistentry>
 
       <varlistentry>

src/basic/proc-cmdline.c

@@ -160,17 +160,29 @@ static const char * const rlmap[] = {
         "3",         SPECIAL_MULTI_USER_TARGET,
         "4",         SPECIAL_MULTI_USER_TARGET,
         "5",         SPECIAL_GRAPHICAL_TARGET,
+        NULL
+};
+
+static const char * const rlmap_initrd[] = {
+        "emergency", SPECIAL_EMERGENCY_TARGET,
+        "rescue",    SPECIAL_RESCUE_TARGET,
+        NULL
 };
 
 const char* runlevel_to_target(const char *word) {
         size_t i;
+        const char * const *rlmap_ptr = in_initrd() ? rlmap_initrd
+                                                    : rlmap;
 
         if (!word)
                 return NULL;
 
-        for (i = 0; i < ELEMENTSOF(rlmap); i += 2)
+        if (in_initrd() && (word = startswith(word, "rd.")) == NULL)
-                if (streq(word, rlmap[i]))
+                return NULL;
-                        return rlmap[i+1];
+
+        for (i = 0; rlmap_ptr[i] != NULL; i += 2)
+                if (streq(word, rlmap_ptr[i]))
+                        return rlmap_ptr[i+1];
 
         return NULL;
 }

src/basic/util.c

@@ -64,6 +64,7 @@ assert_cc(EAGAIN == EWOULDBLOCK);
 
 int saved_argc = 0;
 char **saved_argv = NULL;
+static int saved_in_initrd = -1;
 
 size_t page_size(void) {
         static thread_local size_t pgsz = 0;
@@ -454,11 +455,10 @@ int fork_agent(pid_t *pid, const int except[], unsigned n_except, const char *pa
 }
 
 bool in_initrd(void) {
-        static int saved = -1;
         struct statfs s;
 
-        if (saved >= 0)
+        if (saved_in_initrd >= 0)
-                return saved;
+                return saved_in_initrd;
 
         /* We make two checks here:
          *
@@ -470,11 +470,15 @@ bool in_initrd(void) {
          * emptying when transititioning to the main systemd.
          */
 
-        saved = access("/etc/initrd-release", F_OK) >= 0 &&
+        saved_in_initrd = access("/etc/initrd-release", F_OK) >= 0 &&
-                statfs("/", &s) >= 0 &&
+                          statfs("/", &s) >= 0 &&
-                is_temporary_fs(&s);
+                          is_temporary_fs(&s);
 
-        return saved;
+        return saved_in_initrd;
+}
+
+void in_initrd_force(bool value) {
+        saved_in_initrd = value;
 }
 
 /* hey glibc, APIs with callbacks without a user pointer are so useless */

src/basic/util.h

@@ -86,6 +86,7 @@ int prot_from_flags(int flags) _const_;
 int fork_agent(pid_t *pid, const int except[], unsigned n_except, const char *path, ...);
 
 bool in_initrd(void);
+void in_initrd_force(bool value);
 
 void *xbsearch_r(const void *key, const void *base, size_t nmemb, size_t size,
                  int (*compar) (const void *, const void *, void *),

src/core/main.c

@@ -409,7 +409,7 @@ static int parse_proc_cmdline_item(const char *key, const char *value) {
                 if (detect_container() > 0)
                         log_set_target(LOG_TARGET_CONSOLE);
 
-        } else if (!in_initrd() && !value) {
+        } else if (!value) {
                 const char *target;
 
                 /* SysV compatibility */

src/test/test-proc-cmdline.c

@@ -23,6 +23,7 @@
 #include "proc-cmdline.h"
 #include "special.h"
 #include "string-util.h"
+#include "util.h"
 
 static int parse_item(const char *key, const char *value) {
         assert_se(key);
@@ -36,9 +37,19 @@ static void test_parse_proc_cmdline(void) {
 }
 
 static void test_runlevel_to_target(void) {
+        in_initrd_force(false);
         assert_se(streq_ptr(runlevel_to_target(NULL), NULL));
         assert_se(streq_ptr(runlevel_to_target("unknown-runlevel"), NULL));
+        assert_se(streq_ptr(runlevel_to_target("rd.unknown-runlevel"), NULL));
         assert_se(streq_ptr(runlevel_to_target("3"), SPECIAL_MULTI_USER_TARGET));
+        assert_se(streq_ptr(runlevel_to_target("rd.rescue"), NULL));
+
+        in_initrd_force(true);
+        assert_se(streq_ptr(runlevel_to_target(NULL), NULL));
+        assert_se(streq_ptr(runlevel_to_target("unknown-runlevel"), NULL));
+        assert_se(streq_ptr(runlevel_to_target("rd.unknown-runlevel"), NULL));
+        assert_se(streq_ptr(runlevel_to_target("3"), NULL));
+        assert_se(streq_ptr(runlevel_to_target("rd.rescue"), SPECIAL_RESCUE_TARGET));
 }
 
 int main(void) {