8 files changed, 43 insertions, 64 deletions
diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile
index 9e6668ee93de..1b5a95b1ab09 100644
--- a/arch/s390/boot/Makefile
+++ b/arch/s390/boot/Makefile
@@ -27,7 +27,7 @@ endif
 
 CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
 
-obj-y	:= head.o als.o ebcdic.o sclp_early_core.o mem.o
+obj-y	:= head.o als.o startup.o ebcdic.o sclp_early_core.o mem.o
 targets	:= bzImage startup.a $(obj-y)
 subdir-	:= compressed
 
diff --git a/arch/s390/boot/boot.h b/arch/s390/boot/boot.h
new file mode 100644
index 000000000000..36c93e6cbc3f
--- /dev/null
+++ b/arch/s390/boot/boot.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_BOOT_H
+#define BOOT_BOOT_H
+
+void startup_kernel(void);
+
+#endif /* BOOT_BOOT_H */
diff --git a/arch/s390/boot/compressed/Makefile b/arch/s390/boot/compressed/Makefile
index 04609478d18b..c16ded8a35be 100644
--- a/arch/s390/boot/compressed/Makefile
+++ b/arch/s390/boot/compressed/Makefile
@@ -9,7 +9,7 @@ KCOV_INSTRUMENT := n
 GCOV_PROFILE := n
 UBSAN_SANITIZE := n
 
-obj-y	:= $(if $(CONFIG_KERNEL_UNCOMPRESSED),,head.o misc.o) piggy.o
+obj-y	:= $(if $(CONFIG_KERNEL_UNCOMPRESSED),,misc.o) piggy.o
 targets	:= vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2
 targets += vmlinux.bin.xz vmlinux.bin.lzma vmlinux.bin.lzo vmlinux.bin.lz4
 targets += vmlinux.scr.lds $(obj-y) $(if $(CONFIG_KERNEL_UNCOMPRESSED),,sizes.h)
@@ -32,9 +32,6 @@ quiet_cmd_sizes = GEN     $@
 $(obj)/sizes.h: vmlinux
 	$(call if_changed,sizes)
 
-AFLAGS_head.o += -I$(objtree)/$(obj)
-$(obj)/head.o: $(obj)/sizes.h
-
 CFLAGS_misc.o += -I$(objtree)/$(obj)
 $(obj)/misc.o: $(obj)/sizes.h
 
diff --git a/arch/s390/boot/compressed/decompressor.h b/arch/s390/boot/compressed/decompressor.h
new file mode 100644
index 000000000000..0dd0b84679c4
--- /dev/null
+++ b/arch/s390/boot/compressed/decompressor.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_COMPRESSED_DECOMPRESSOR_H
+#define BOOT_COMPRESSED_DECOMPRESSOR_H
+
+#ifdef CONFIG_KERNEL_UNCOMPRESSED
+static inline void *decompress_kernel(unsigned long *uncompressed_size) {}
+#else
+void *decompress_kernel(unsigned long *uncompressed_size);
+#endif
+
+#endif /* BOOT_COMPRESSED_DECOMPRESSOR_H */
diff --git a/arch/s390/boot/compressed/head.S b/arch/s390/boot/compressed/head.S
deleted file mode 100644
index 4041fcfd8980..000000000000
--- a/arch/s390/boot/compressed/head.S
+++ /dev/null
@@ -1,52 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Startup glue code to uncompress the kernel
- *
- * Copyright IBM Corp. 2010
- *
- *   Author(s):	Martin Schwidefsky <schwidefsky@de.ibm.com>
- */
-
-#include <linux/init.h>
-#include <linux/linkage.h>
-#include <asm/asm-offsets.h>
-#include <asm/thread_info.h>
-#include <asm/page.h>
-#include <asm/ptrace.h>
-#include "sizes.h"
-
-__HEAD
-ENTRY(startup_decompressor)
-	basr	%r13,0			# get base
-.LPG1:
-	# setup stack
-	lg	%r15,.Lstack-.LPG1(%r13)
-	brasl	%r14,decompress_kernel
-	# Set up registers for memory mover. We move the decompressed image to
-	# 0x100000, where startup_continue of the decompressed image is supposed
-	# to be.
-	lgr	%r4,%r2
-	lg	%r2,.Loffset-.LPG1(%r13)
-	lg	%r3,.Lmvsize-.LPG1(%r13)
-	lgr	%r5,%r3
-	# Move the memory mover someplace safe so it doesn't overwrite itself.
-	la	%r1,0x200
-	mvc	0(mover_end-mover,%r1),mover-.LPG1(%r13)
-	# When the memory mover is done we pass control to
-	# arch/s390/kernel/head64.S:startup_continue which lives at 0x100000 in
-	# the decompressed image.
-	lgr	%r6,%r2
-	br	%r1
-mover:
-	mvcle	%r2,%r4,0
-	jo	mover
-	br	%r6
-mover_end:
-
-	.align	8
-.Lstack:
-	.quad	0x8000 + THREAD_SIZE - STACK_FRAME_OVERHEAD
-.Loffset:
-	.quad	0x100000
-.Lmvsize:
-	.quad	SZ__bss_start
diff --git a/arch/s390/boot/compressed/misc.c b/arch/s390/boot/compressed/misc.c
index f66ad73c205b..321f6151ded9 100644
--- a/arch/s390/boot/compressed/misc.c
+++ b/arch/s390/boot/compressed/misc.c
@@ -12,6 +12,7 @@
 #include <asm/sclp.h>
 #include <asm/ipl.h>
 #include "sizes.h"
+#include "decompressor.h"
 
 /*
  * gzip declarations
@@ -82,7 +83,7 @@ static void error(char *x)
 	asm volatile("lpsw %0" : : "Q" (psw));
 }
 
-unsigned long decompress_kernel(void)
+void *decompress_kernel(unsigned long *uncompressed_size)
 {
 	void *output, *kernel_end;
 
@@ -111,6 +112,8 @@ unsigned long decompress_kernel(void)
 	free_mem_end_ptr = free_mem_ptr + HEAP_SIZE;
 
 	__decompress(input_data, input_len, NULL, NULL, output, 0, NULL, error);
-	return (unsigned long) output;
+	if (uncompressed_size)
+		*uncompressed_size = SZ__bss_start;
+	return output;
 }
 
diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S
index d0736a05bc7f..e209cfe69bb9 100644
--- a/arch/s390/boot/head.S
+++ b/arch/s390/boot/head.S
@@ -312,11 +312,7 @@ ENTRY(startup_kdump)
 	mvc	__LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
 	l	%r15,.Lstack-.LPG0(%r13)
 	brasl	%r14,verify_facilities
-#ifdef CONFIG_KERNEL_UNCOMPRESSED
-	jg	startup_continue
-#else
-	jg	startup_decompressor
-#endif
+	brasl	%r14,startup_kernel
 
 .Lstack:
 	.long	0x8000 + THREAD_SIZE - STACK_FRAME_OVERHEAD
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
new file mode 100644
index 000000000000..2a9ce355f8e6
--- /dev/null
+++ b/arch/s390/boot/startup.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/string.h>
+#include "compressed/decompressor.h"
+#include "boot.h"
+
+void startup_kernel(void)
+{
+	void (*startup_continue)(void) = (void *)0x100000;
+	unsigned long uncompressed_size;
+	void *uncompressed_img;
+
+	if (!IS_ENABLED(CONFIG_KERNEL_UNCOMPRESSED)) {
+		uncompressed_img = decompress_kernel(&uncompressed_size);
+		memmove(startup_continue, uncompressed_img, uncompressed_size);
+	}
+	startup_continue();
+}