pSeries HVC console: Add SYSRQ and handle errors better from Dave Engebretsen

arch/ppc64/kernel/pSeries_lpar.c

@@ -355,8 +355,13 @@ static int udbg_getc_pollLP(void)
 		/* get some more chars. */
 		inbuflen = 0;
 		rc = plpar_get_term_char(vtermno, &inbuflen, buf);
-		if (inbuflen == 0 && rc == H_Success)
-			return -1;
+		if (rc != H_Success)
+			inbuflen = 0;	/* otherwise inbuflen is garbage */
+	}
+	if (inbuflen <= 0 || inbuflen > 16) {
+		/* Catch error case as well as other oddities (corruption) */
+		inbuflen = 0;
+		return -1;
 	}
 	ch = buf[0];
 	for (i = 1; i < inbuflen; i++)	/* shuffle them down. */

drivers/char/hvc_console.c

@@ -22,6 +22,7 @@
 #include <linux/console.h>
 #include <linux/major.h>
 #include <linux/kernel.h>
+#include <linux/sysrq.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/sched.h>
@@ -46,6 +47,9 @@ static struct tty_struct *hvc_table[MAX_NR_HVC_CONSOLES];
 static struct termios *hvc_termios[MAX_NR_HVC_CONSOLES];
 static struct termios *hvc_termios_locked[MAX_NR_HVC_CONSOLES];
 static int hvc_offset;
+#ifdef CONFIG_MAGIC_SYSRQ
+static int sysrq_pressed;
+#endif
 
 #define N_OUTBUF	16
 
@@ -194,8 +198,19 @@ static void hvc_poll(int index)
 			n = hvc_get_chars(index + hvc_offset, buf, sizeof(buf));
 			if (n <= 0)
 				break;
-			for (i = 0; i < n; ++i)
+			for (i = 0; i < n; ++i) {
+#ifdef CONFIG_MAGIC_SYSRQ		/* Handle the SysRq Hack */
+				if (buf[i] == '\x0f') {	/* ^O -- should support a sequence */
+					sysrq_pressed = 1;
+					continue;
+				} else if (sysrq_pressed) {
+					handle_sysrq(buf[i], NULL, NULL, tty);
+					sysrq_pressed = 0;
+					continue;
+				}
+#endif
 				tty_insert_flip_char(tty, buf[i], 0);
+			}
 		}
 		if (tty->flip.count)
 			tty_schedule_flip(tty);