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-rw-r--r--arch/um/drivers/stderr_console.c63
1 files changed, 63 insertions, 0 deletions
diff --git a/arch/um/drivers/stderr_console.c b/arch/um/drivers/stderr_console.c
new file mode 100644
index 0000000000..ecc3a58149
--- /dev/null
+++ b/arch/um/drivers/stderr_console.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/console.h>
+
+#include "chan_user.h"
+
+/* ----------------------------------------------------------------------------- */
+/* trivial console driver -- simply dump everything to stderr */
+
+/*
+ * Don't register by default -- as this registers very early in the
+ * boot process it becomes the default console.
+ *
+ * Initialized at init time.
+ */
+static int use_stderr_console = 0;
+
+static void stderr_console_write(struct console *console, const char *string,
+ unsigned len)
+{
+ generic_write(2 /* stderr */, string, len, NULL);
+}
+
+static struct console stderr_console = {
+ .name = "stderr",
+ .write = stderr_console_write,
+ .flags = CON_PRINTBUFFER,
+};
+
+static int __init stderr_console_init(void)
+{
+ if (use_stderr_console)
+ register_console(&stderr_console);
+ return 0;
+}
+console_initcall(stderr_console_init);
+
+static int stderr_setup(char *str)
+{
+ if (!str)
+ return 0;
+ use_stderr_console = simple_strtoul(str,&str,0);
+ return 1;
+}
+__setup("stderr=", stderr_setup);
+
+/* The previous behavior of not unregistering led to /dev/console being
+ * impossible to open. My FC5 filesystem started having init die, and the
+ * system panicing because of this. Unregistering causes the real
+ * console to become the default console, and /dev/console can then be
+ * opened. Making this an initcall makes this happen late enough that
+ * there is no added value in dumping everything to stderr, and the
+ * normal console is good enough to show you all available output.
+ */
+static int __init unregister_stderr(void)
+{
+ unregister_console(&stderr_console);
+
+ return 0;
+}
+
+__initcall(unregister_stderr);