Merge pull request #18375 from yuwata/cli-tools-also-read-kernel-command-line

tree-wide: make CLI tools also read kernel command line when run as service

src/basic/env-util.c

@@ -12,6 +12,8 @@
 #include "extract-word.h"
 #include "macro.h"
 #include "parse-util.h"
+#include "process-util.h"
+#include "stdio-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "utf8.h"
@@ -749,3 +751,24 @@ int set_unset_env(const char *name, const char *value, bool overwrite) {
                 return -errno;
         return 0;
 }
+
+int setenv_systemd_exec_pid(bool update_only) {
+        char str[DECIMAL_STR_MAX(pid_t)];
+        const char *e;
+
+        /* Update $SYSTEMD_EXEC_PID=pid except when '*' is set for the variable. */
+
+        e = secure_getenv("SYSTEMD_EXEC_PID");
+        if (!e && update_only)
+                return 0;
+
+        if (streq_ptr(e, "*"))
+                return 0;
+
+        xsprintf(str, PID_FMT, getpid_cached());
+
+        if (setenv("SYSTEMD_EXEC_PID", str, 1) < 0)
+                return -errno;
+
+        return 1;
+}

src/basic/env-util.h

@@ -55,3 +55,5 @@ int getenv_bool_secure(const char *p);
 
 /* Like setenv, but calls unsetenv if value == NULL. */
 int set_unset_env(const char *name, const char *value, bool overwrite);
+
+int setenv_systemd_exec_pid(bool update_only);

src/basic/log.c

@@ -1157,20 +1157,38 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
         return 0;
 }
 
-void log_parse_environment(void) {
-        if (getpid_cached() == 1 || get_ctty_devnr(0, NULL) < 0)
-                /* Only try to read the command line in daemons. We assume that anything that has a
-                 * controlling tty is user stuff. For PID1 we do a special check in case it hasn't
-                 * closed the console yet. */
-                (void) proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_STRIP_RD_PREFIX);
+static bool should_parse_proc_cmdline(void) {
+        const char *e;
+        pid_t p;
 
-        log_parse_environment_cli();
+        /* PID1 always reads the kernel command line. */
+        if (getpid_cached() == 1)
+                return true;
+
+        /* If the process is directly executed by PID1 (e.g. ExecStart= or generator), systemd-importd,
+         * or systemd-homed, then $SYSTEMD_EXEC_PID= is set, and read the command line. */
+        e = getenv("SYSTEMD_EXEC_PID");
+        if (!e)
+                return false;
+
+        if (streq(e, "*"))
+                /* For testing. */
+                return true;
+
+        if (parse_pid(e, &p) < 0)
+                /* We know that systemd sets the variable correctly. Something else must have set it. */
+                log_debug("Failed to parse \"$SYSTEMD_EXEC_PID=%s\". Ignoring.", e);
+
+        return getpid_cached() == p;
 }
 
-void log_parse_environment_cli(void) {
+void log_parse_environment(void) {
+        const char *e;
+
         /* Do not call from library code. */
 
-        const char *e;
+        if (should_parse_proc_cmdline())
+                (void) proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_STRIP_RD_PREFIX);
 
         e = getenv("SYSTEMD_LOG_TARGET");
         if (e && log_set_target_from_string(e) < 0)
@@ -1460,22 +1478,10 @@ int log_dup_console(void) {
         return 0;
 }
 
-void log_setup_service(void) {
-        /* Sets up logging the way it is most appropriate for running a program as a service. Note that using this
-         * doesn't make the binary unsuitable for invocation on the command line, as log output will still go to the
-         * terminal if invoked interactively. */
-
+void log_setup(void) {
         log_set_target(LOG_TARGET_AUTO);
         log_parse_environment();
         (void) log_open();
-}
-
-void log_setup_cli(void) {
-        /* Sets up logging the way it is most appropriate for running a program as a CLI utility. */
-
-        log_set_target(LOG_TARGET_AUTO);
-        log_parse_environment_cli();
-        (void) log_open();
         if (log_on_console() && show_color < 0)
                 log_show_color(true);
 }

src/basic/log.h

@@ -69,7 +69,6 @@ void log_close(void);
 void log_forget_fds(void);
 
 void log_parse_environment(void);
-void log_parse_environment_cli(void);
 
 int log_dispatch_internal(
                 int level,
@@ -301,5 +300,4 @@ int log_syntax_invalid_utf8_internal(
 
 #define DEBUG_LOGGING _unlikely_(log_get_max_level() >= LOG_DEBUG)
 
-void log_setup_service(void);
-void log_setup_cli(void);
+void log_setup(void);