kdb: Prevent kernel oops with kdb_defcmd

The kdb_defcmd can only be used to display the available command aliases
while using the kernel debug shell.  If you try to define a new macro
while the kernel debugger is active it will oops.  The debug shell
macros must use pre-allocated memory set aside at the time kdb_init()
is run, and the kdb_defcmd is restricted to only working at the time
that the kdb_init sequence is being run, which only occurs if you
actually activate the kernel debugger.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index cdfc0a7e583e..496f596aa807 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -681,6 +681,10 @@ static int kdb_defcmd(int argc, const char **argv)
         }
         if (argc != 3)
                 return KDB_ARGCOUNT;
+        if (in_dbg_master()) {
+                kdb_printf("Command only available during kdb_init()\n");
+                return KDB_NOTIMP;
+        }
         defcmd_set = kmalloc((defcmd_set_count + 1) * sizeof(*defcmd_set),
                              GFP_KDB);
         if (!defcmd_set)
@@ -2796,8 +2800,8 @@ static void __init kdb_inittab(void)
           "Stack traceback", 1, KDB_REPEAT_NONE);
         kdb_register_repeat("btp", kdb_bt, "<pid>",
           "Display stack for process <pid>", 0, KDB_REPEAT_NONE);
-        kdb_register_repeat("bta", kdb_bt, "[DRSTCZEUIMA]",
-          "Display stack all processes", 0, KDB_REPEAT_NONE);
+        kdb_register_repeat("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]",
+          "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE);
         kdb_register_repeat("btc", kdb_bt, "",
           "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE);
         kdb_register_repeat("btt", kdb_bt, "<vaddr>",