From 8750a06b6caa9c1d33872cb7b0fa077497ef9888 Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Thu, 20 Apr 2023 10:31:37 +0200
Subject: [PATCH] log: Add knob to disable kmsg ratelimiting

This allows us to disable kmsg ratelimiting in the integration tests
and mkosi for easier debugging.
---
 man/common-variables.xml    |  8 ++++++++
 man/kernel-command-line.xml |  1 +
 man/systemd.xml             | 14 +++++++++++---
 src/basic/log.c             | 22 +++++++++++++++++++++-
 4 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/man/common-variables.xml b/man/common-variables.xml
index 0e220b3f9eb..81425e57e20 100644
--- a/man/common-variables.xml
+++ b/man/common-variables.xml
@@ -81,6 +81,14 @@
       </listitem>
     </varlistentry>
 
+    <varlistentry id='log-ratelimit-kmsg'>
+      <term><varname>$SYSTEMD_LOG_RATELIMIT_KMSG</varname></term>
+
+      <listitem><para id='log-ratelimit-kmsg-body'> Whether to ratelimit kmsg or not. Takes a boolean.
+      Defaults to <literal>true</literal>. If disabled, systemd will not ratelimit messages written to kmsg.
+      </para></listitem>
+    </varlistentry>
+
     <varlistentry id='pager'>
       <term><varname>$SYSTEMD_PAGER</varname></term>
 
diff --git a/man/kernel-command-line.xml b/man/kernel-command-line.xml
index 27ef72da361..09f8ace4de6 100644
--- a/man/kernel-command-line.xml
+++ b/man/kernel-command-line.xml
@@ -66,6 +66,7 @@
         <term><varname>systemd.log_level=</varname></term>
         <term><varname>systemd.log_location=</varname></term>
         <term><varname>systemd.log_color</varname></term>
+        <term><varname>systemd.log_ratelimit_kmsg</varname></term>
         <term><varname>systemd.default_standard_output=</varname></term>
         <term><varname>systemd.default_standard_error=</varname></term>
         <term><varname>systemd.setenv=</varname></term>
diff --git a/man/systemd.xml b/man/systemd.xml
index 1a68301d50b..ca9e4e99880 100644
--- a/man/systemd.xml
+++ b/man/systemd.xml
@@ -680,6 +680,11 @@
         <para>This can be overridden with <option>--log-target=</option>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>$SYSTEMD_LOG_RATELIMIT_KMSG</varname></term>
+        <listitem><xi:include href="common-variables.xml" xpointer="log-ratelimit-kmsg" /></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>$XDG_CONFIG_HOME</varname></term>
         <term><varname>$XDG_CONFIG_DIRS</varname></term>
@@ -865,13 +870,16 @@
         <term><varname>systemd.log_target=</varname></term>
         <term><varname>systemd.log_time</varname></term>
         <term><varname>systemd.log_tid</varname></term>
+        <term><varname>systemd.log_ratelimit_kmsg</varname></term>
 
         <listitem><para>Controls log output, with the same effect as the
         <varname>$SYSTEMD_LOG_COLOR</varname>, <varname>$SYSTEMD_LOG_LEVEL</varname>,
         <varname>$SYSTEMD_LOG_LOCATION</varname>, <varname>$SYSTEMD_LOG_TARGET</varname>,
-        <varname>$SYSTEMD_LOG_TIME</varname>, and <varname>$SYSTEMD_LOG_TID</varname> environment variables
-        described above. <varname>systemd.log_color</varname>, <varname>systemd.log_location</varname>,
-        <varname>systemd.log_time</varname>, and <varname>systemd.log_tid=</varname> can be specified without
+        <varname>$SYSTEMD_LOG_TIME</varname>, <varname>$SYSTEMD_LOG_TID</varname> and
+        <varname>$SYSTEMD_LOG_RATELIMIT_KMSG</varname> environment variables described above.
+        <varname>systemd.log_color</varname>, <varname>systemd.log_location</varname>,
+        <varname>systemd.log_time</varname>, <varname>systemd.log_tid</varname> and
+        <varname>systemd.log_ratelimit_kmsg</varname> can be specified without
         an argument, with the same effect as a positive boolean.</para></listitem>
       </varlistentry>
 
diff --git a/src/basic/log.c b/src/basic/log.c
index 75f59c43431..d0fef3554f5 100644
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -50,6 +50,7 @@ static void *log_syntax_callback_userdata = NULL;
 static LogTarget log_target = LOG_TARGET_CONSOLE;
 static int log_max_level = LOG_INFO;
 static int log_facility = LOG_DAEMON;
+static bool ratelimit_kmsg = true;
 
 static int console_fd = STDERR_FILENO;
 static int syslog_fd = -EBADF;
@@ -552,7 +553,7 @@ static int write_to_kmsg(
         if (kmsg_fd < 0)
                 return 0;
 
-        if (!ratelimit_below(&ratelimit))
+        if (ratelimit_kmsg && !ratelimit_below(&ratelimit))
                 return 0;
 
         xsprintf(header_priority, "<%i>", level);
@@ -1178,6 +1179,17 @@ int log_set_max_level_from_string(const char *e) {
         return 0;
 }
 
+static int log_set_ratelimit_kmsg_from_string(const char *e) {
+        int r;
+
+        r = parse_boolean(e);
+        if (r < 0)
+                return r;
+
+        ratelimit_kmsg = r;
+        return 0;
+}
+
 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
 
         /*
@@ -1228,6 +1240,10 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
                 if (log_show_time_from_string(value ?: "1") < 0)
                         log_warning("Failed to parse log time setting '%s'. Ignoring.", value);
 
+        } else if (proc_cmdline_key_streq(key, "systemd.log_ratelimit_kmsg")) {
+
+                if (log_set_ratelimit_kmsg_from_string(value ?: "1") < 0)
+                        log_warning("Failed to parse log ratelimit kmsg boolean '%s'. Ignoring.", value);
         }
 
         return 0;
@@ -1268,6 +1284,10 @@ void log_parse_environment_variables(void) {
         e = getenv("SYSTEMD_LOG_TID");
         if (e && log_show_tid_from_string(e) < 0)
                 log_warning("Failed to parse log tid '%s'. Ignoring.", e);
+
+        e = getenv("SYSTEMD_LOG_RATELIMIT_KMSG");
+        if (e && log_set_ratelimit_kmsg_from_string(e) < 0)
+                log_warning("Failed to parse log ratelimit kmsg boolean '%s'. Ignoring.", e);
 }
 
 void log_parse_environment(void) {