kernel: syslog: Handle userspace kmsg logging

- Add USER_KMSG option to configure if kernel messages
  should be logged in user contexts

- Add syslog_silence() to silence kernel messages in user
  contexts if USER_KMSG is "yes"

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/sys/kern/kern_syslog.c b/sys/kern/kern_syslog.c
index 656362e..db50a3c 100644
--- a/sys/kern/kern_syslog.c
+++ b/sys/kern/kern_syslog.c
@@ -40,8 +40,15 @@
 #define SERIAL_DEBUG 0
 #endif
 
+#if defined(__USER_KMSG)
+#define USER_KMSG __USER_KMSG
+#else
+#define USER_KMSG 0
+#endif
+
 /* Global logger lock */
 static struct spinlock lock = {0};
+static bool no_cons_log = false;
 
 static void
 syslog_write(const char *s, size_t len)
@@ -58,6 +65,15 @@ syslog_write(const char *s, size_t len)
         }
     }
 
+    /*
+     * If the USER_KMSG option is disabled in kconf,
+     * do not log to the console if everything else
+     * has already started.
+     */
+    if (!USER_KMSG && no_cons_log) {
+        return;
+    }
+
     cons_putstr(&g_root_scr, s, len);
 }
 
@@ -116,3 +132,16 @@ kprintf(const char *fmt, ...)
     va_end(ap);
     spinlock_release(&lock);
 }
+
+/*
+ * Silence kernel messages in if the system
+ * is already operating in a user context.
+ *
+ * XXX: This is ignored if the kconf USER_KMSG
+ *      option is set to "no"
+ */
+void
+syslog_silence(bool option)
+{
+    no_cons_log = option;
+}