s390/early: move functions which may not access bss section to extra file

Move functions which may not access bss section to extra file. This
makes it easier to verify that all early functions which may not rely
on an initialized bss section are not accessing it.

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/arch/s390/kernel/early_nobss.c b/arch/s390/kernel/early_nobss.c
new file mode 100644
index 000000000000..2d84fc48df3a
--- /dev/null
+++ b/arch/s390/kernel/early_nobss.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *    Copyright IBM Corp. 2007, 2018
+ */
+
+/*
+ * Early setup functions which may not rely on an initialized bss
+ * section. The last thing that is supposed to happen here is
+ * initialization of the bss section.
+ */
+
+#include <linux/processor.h>
+#include <linux/string.h>
+#include <asm/sections.h>
+#include <asm/lowcore.h>
+#include <asm/setup.h>
+#include <asm/timex.h>
+#include "entry.h"
+
+static void __init reset_tod_clock(void)
+{
+	u64 time;
+
+	if (store_tod_clock(&time) == 0)
+		return;
+	/* TOD clock not running. Set the clock to Unix Epoch. */
+	if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)
+		disabled_wait(0);
+
+	memset(tod_clock_base, 0, 16);
+	*(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;
+	S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;
+}
+
+static void __init rescue_initrd(void)
+{
+	unsigned long min_initrd_addr = (unsigned long) _end + (4UL << 20);
+
+	/*
+	 * Just like in case of IPL from VM reader we make sure there is a
+	 * gap of 4MB between end of kernel and start of initrd.
+	 * That way we can also be sure that saving an NSS will succeed,
+	 * which however only requires different segments.
+	 */
+	if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD))
+		return;
+	if (!INITRD_START || !INITRD_SIZE)
+		return;
+	if (INITRD_START >= min_initrd_addr)
+		return;
+	memmove((void *) min_initrd_addr, (void *) INITRD_START, INITRD_SIZE);
+	INITRD_START = min_initrd_addr;
+}
+
+static void __init clear_bss_section(void)
+{
+	memset(__bss_start, 0, __bss_stop - __bss_start);
+}
+
+void __init startup_init_nobss(void)
+{
+	reset_tod_clock();
+	rescue_initrd();
+	clear_bss_section();
+}