1 files changed, 73 insertions, 22 deletions

diff --git a/kernel/debug/kdb/kdb_keyboard.c b/kernel/debug/kdb/kdb_keyboard.c
index 4bca634975c..118527aa60e 100644
--- a/kernel/debug/kdb/kdb_keyboard.c
+++ b/kernel/debug/kdb/kdb_keyboard.c
@@ -25,6 +25,7 @@
 #define KBD_STAT_MOUSE_OBF      0x20    /* Mouse output buffer full */
 
 static int kbd_exists;
+static int kbd_last_ret;
 
 /*
  * Check if the keyboard controller has a keypress for us.
@@ -90,8 +91,11 @@ int kdb_get_kbd_char(void)
                 return -1;
         }
 
-        if ((scancode & 0x80) != 0)
+        if ((scancode & 0x80) != 0) {
+                if (scancode == 0x9c)
+                        kbd_last_ret = 0;
                 return -1;
+        }
 
         scancode &= 0x7f;
 
@@ -178,35 +182,82 @@ int kdb_get_kbd_char(void)
                 return -1;      /* ignore unprintables */
         }
 
-        if ((scancode & 0x7f) == 0x1c) {
-                /*
-                 * enter key.  All done.  Absorb the release scancode.
-                 */
+        if (scancode == 0x1c) {
+                kbd_last_ret = 1;
+                return 13;
+        }
+
+        return keychar & 0xff;
+}
+EXPORT_SYMBOL_GPL(kdb_get_kbd_char);
+
+/*
+ * Best effort cleanup of ENTER break codes on leaving KDB. Called on
+ * exiting KDB, when we know we processed an ENTER or KP ENTER scan
+ * code.
+ */
+void kdb_kbd_cleanup_state(void)
+{
+        int scancode, scanstatus;
+
+        /*
+         * Nothing to clean up, since either
+         * ENTER was never pressed, or has already
+         * gotten cleaned up.
+         */
+        if (!kbd_last_ret)
+                return;
+
+        kbd_last_ret = 0;
+        /*
+         * Enter key. Need to absorb the break code here, lest it gets
+         * leaked out if we exit KDB as the result of processing 'g'.
+         *
+         * This has several interesting implications:
+         * + Need to handle KP ENTER, which has break code 0xe0 0x9c.
+         * + Need to handle repeat ENTER and repeat KP ENTER. Repeats
+         *   only get a break code at the end of the repeated
+         *   sequence. This means we can't propagate the repeated key
+         *   press, and must swallow it away.
+         * + Need to handle possible PS/2 mouse input.
+         * + Need to handle mashed keys.
+         */
+
+        while (1) {
                 while ((inb(KBD_STATUS_REG) & KBD_STAT_OBF) == 0)
-                        ;
+                        cpu_relax();
 
                 /*
-                 * Fetch the scancode
+                 * Fetch the scancode.
                  */
                 scancode = inb(KBD_DATA_REG);
                 scanstatus = inb(KBD_STATUS_REG);
 
-                while (scanstatus & KBD_STAT_MOUSE_OBF) {
-                        scancode = inb(KBD_DATA_REG);
-                        scanstatus = inb(KBD_STATUS_REG);
-                }
+                /*
+                 * Skip mouse input.
+                 */
+                if (scanstatus & KBD_STAT_MOUSE_OBF)
+                        continue;
 
-                if (scancode != 0x9c) {
-                        /*
-                         * Wasn't an enter-release,  why not?
-                         */
-                        kdb_printf("kdb: expected enter got 0x%x status 0x%x\n",
-                               scancode, scanstatus);
-                }
+                /*
+                 * If we see 0xe0, this is either a break code for KP
+                 * ENTER, or a repeat make for KP ENTER. Either way,
+                 * since the second byte is equivalent to an ENTER,
+                 * skip the 0xe0 and try again.
+                 *
+                 * If we see 0x1c, this must be a repeat ENTER or KP
+                 * ENTER (and we swallowed 0xe0 before). Try again.
+                 *
+                 * We can also see make and break codes for other keys
+                 * mashed before or after pressing ENTER. Thus, if we
+                 * see anything other than 0x9c, we have to try again.
+                 *
+                 * Note, if you held some key as ENTER was depressed,
+                 * that break code would get leaked out.
+                 */
+                if (scancode != 0x9c)
+                        continue;
 
-                return 13;
+                return;
         }
-
-        return keychar & 0xff;
 }
-EXPORT_SYMBOL_GPL(kdb_get_kbd_char);