[kvm-unit-tests PATCH v6 03/11] s390x: Make tests bootable from disk

[kvm-unit-tests PATCH v6 03/11] s390x: Make tests bootable from disk

[Janosch Frank]

Currently tests are run with the --kernel option of Qemu, which will
load the ELF file and jump to the start address. When booting from
disk, we need to specify a start address. This is done by setting the
initial short PSW at 0x0.

.text was moved to 0x11000 because the bootloader can write from
0x10480 until 0x11000 if it has a lot to write. 0x10480 to 0x10600 was
not enough safe space.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 s390x/Makefile   |  2 +-
 s390x/cstart64.S |  8 +++++++-
 s390x/flat.lds   | 13 ++++++++++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/s390x/Makefile b/s390x/Makefile
index ede2961..ed6ef0b 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -50,7 +50,7 @@ FLATLIBS = $(libcflat)
 %.elf: %.o $(FLATLIBS) $(SRCDIR)/s390x/flat.lds $(cstart.o)
 	$(CC) $(CFLAGS) -c -o $(@:.elf=.aux.o) \
 		$(SRCDIR)/lib/auxinfo.c -DPROGNAME=\"$@\"
-	$(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/flat.lds -Ttext=0x10000 \
+	$(CC) $(LDFLAGS) -o $@ -T $(SRCDIR)/s390x/flat.lds \
 		$(filter %.o, $^) $(FLATLIBS) $(@:.elf=.aux.o)
 	$(RM) $(@:.elf=.aux.o)
 	@chmod a-x $@
diff --git a/s390x/cstart64.S b/s390x/cstart64.S
index dc7ddd6..385915e 100644
--- a/s390x/cstart64.S
+++ b/s390x/cstart64.S
@@ -14,7 +14,13 @@
 
 .section .init
 
-/* entry point - for KVM + TCG we directly start in 64 bit mode */
+/*
+ * Short init between 0x10000 and 0x10480 and then jump to 0x11000.
+ * 0x10480 - 0x11000 are written to by bootloader.
+ *
+ * For KVM and TCG kernel boot we are in 64 bit z/Arch mode.
+ * When booting from disk the initial short psw is in 31 bit mode.
+ */
 	.globl start
 start:
 	/* setup stack */
diff --git a/s390x/flat.lds b/s390x/flat.lds
index b6e2172..977af7c 100644
--- a/s390x/flat.lds
+++ b/s390x/flat.lds
@@ -1,10 +1,21 @@
 SECTIONS
 {
+	/*
+	 * Initial short psw for disk boot, with 31 bit addressing for
+	 * non z/Arch environment compatibility and the instruction
+	 * address 0x10000 (cstart64.S .init).
+	 */
+	.lowcore : {
+		. = 0;
+		 LONG(0x00080000)
+		 LONG(0x80010000)
+	}
+	. = 0x10000;
 	.text : {
 		*(.init)
 		. = 0x480;
 		ipl_args = .;
-		. = 0x600;
+		.  = 0x1000;
 		*(.text)
 		*(.text.*)
 	}
-- 
2.14.3