Dynamic Debug: Introduce ddebug_query= boot parameter

Dynamic debug lacks the ability to enable debug messages at boot time.
One could patch initramfs or service startup scripts to write to
/sys/../dynamic_debug/control, but this sucks.

This patch makes it possible to pass a query in the same format one can
write to /sys/../dynamic_debug/control via boot param.
When dynamic debug gets initialized, this query will automatically be
applied.


Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: jbaron@redhat.com
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 84d103c474e4..44ce66bdb211 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -450,6 +450,19 @@ static int ddebug_exec_query(char *query_string)
         return 0;
 }
 
+static __initdata char ddebug_setup_string[1024];
+static __init int ddebug_setup_query(char *str)
+{
+        if (strlen(str) >= 1024) {
+                pr_warning("ddebug boot param string too large\n");
+                return 0;
+        }
+        strcpy(ddebug_setup_string, str);
+        return 1;
+}
+
+__setup("ddebug_query=", ddebug_setup_query);
+
 /*
  * File_ops->write method for <debugfs>/dynamic_debug/conrol.  Gathers the
  * command text from userspace, parses and executes it.
@@ -769,6 +782,18 @@ static int __init dynamic_debug_init(void)
                 }
                 ret = ddebug_add_module(iter_start, n, modname);
         }
+
+        /* ddebug_query boot param got passed -> set it up */
+        if (ddebug_setup_string[0] != '\0') {
+                ret = ddebug_exec_query(ddebug_setup_string);
+                if (ret)
+                        pr_warning("Invalid ddebug boot param %s",
+                                   ddebug_setup_string);
+                else
+                        pr_info("ddebug initialized with string %s",
+                                ddebug_setup_string);
+        }
+
 out_free:
         if (ret) {
                 ddebug_remove_all_tables();