s390/boot: move sclp early buffer from fixed address in asm to C

To make the decompressor relocatable, the early SCLP buffer with a fixed
address must be replaced with a relocatable C buffer of the according size
and alignment as required by SCLP.

Introduce a new function sclp_early_set_buffer() into the SCLP driver
which enables the decompressor to change the SCLP early buffer at any time.
This will be useful when the decompressor becomes fully relocatable and
might need to change the SCLP early buffer to one with an address < 2G
as required by SCLP because it was loaded at an address >= 2G.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

6 files changed, 17 insertions, 7 deletions

diff --git a/arch/s390/boot/boot.h b/arch/s390/boot/boot.h
index 3d7d5ef4d169..716c35c1d78f 100644
--- a/arch/s390/boot/boot.h
+++ b/arch/s390/boot/boot.h
@@ -13,6 +13,7 @@ void setup_boot_command_line(void);
 void parse_boot_command_line(void);
 void verify_facilities(void);
 void print_missing_facilities(void);
+void sclp_early_setup_buffer(void);
 void print_pgm_check_info(void);
 unsigned long get_random_base(unsigned long safe_addr);
 void __printf(1, 2) decompressor_printk(const char *fmt, ...);
diff --git a/arch/s390/boot/compressed/vmlinux.lds.S b/arch/s390/boot/compressed/vmlinux.lds.S
index 0bd8aaaa4b33..d6a69aa6e937 100644
--- a/arch/s390/boot/compressed/vmlinux.lds.S
+++ b/arch/s390/boot/compressed/vmlinux.lds.S
@@ -3,6 +3,7 @@
 #include <asm/vmlinux.lds.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
+#include <asm/sclp.h>
 
 OUTPUT_FORMAT("elf64-s390", "elf64-s390", "elf64-s390")
 OUTPUT_ARCH(s390:64-bit)
@@ -54,7 +55,9 @@ SECTIONS
 		KEEP(*(.dma.ex_table))
 		_stop_dma_ex_table = .;
 	}
-	.dma.data : { *(.dma.data) }
+	.dma.data : {
+		*(.dma.data)
+	}
 	. = ALIGN(PAGE_SIZE);
 	_edma = .;
 
diff --git a/arch/s390/boot/head.S b/arch/s390/boot/head.S
index 4ac3958b3032..759f77c6af45 100644
--- a/arch/s390/boot/head.S
+++ b/arch/s390/boot/head.S
@@ -320,6 +320,7 @@ SYM_CODE_START_LOCAL(startup_normal)
 	spt	6f-.LPG0(%r13)
 	mvc	__LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
 	larl	%r15,_stack_end-STACK_FRAME_OVERHEAD
+	brasl	%r14,sclp_early_setup_buffer
 	brasl	%r14,verify_facilities
 	brasl	%r14,startup_kernel
 SYM_CODE_END(startup_normal)
@@ -410,7 +411,4 @@ SYM_DATA_START(parmarea)
 	.org	PARMAREA+__PARMAREA_SIZE
 SYM_DATA_END(parmarea)
 
-	.org	EARLY_SCCB_OFFSET
-	.fill	EXT_SCCB_READ_SCP
-
 	.org	HEAD_END
diff --git a/arch/s390/boot/sclp_early_core.c b/arch/s390/boot/sclp_early_core.c
index 5a19fd7020b5..6f30646afbd0 100644
--- a/arch/s390/boot/sclp_early_core.c
+++ b/arch/s390/boot/sclp_early_core.c
@@ -1,2 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
+#include "boot.h"
 #include "../../../drivers/s390/char/sclp_early_core.c"
+
+/* SCLP early buffer must stay page-aligned and below 2GB */
+static char __sclp_early_sccb[EXT_SCCB_READ_SCP] __aligned(PAGE_SIZE);
+
+void sclp_early_setup_buffer(void)
+{
+	sclp_early_set_buffer(&__sclp_early_sccb);
+}
diff --git a/arch/s390/include/asm/sclp.h b/arch/s390/include/asm/sclp.h
index 3adbb417f740..835adb85b016 100644
--- a/arch/s390/include/asm/sclp.h
+++ b/arch/s390/include/asm/sclp.h
@@ -115,6 +115,7 @@ struct zpci_report_error_header {
 	u8 data[0];	/* Subsequent Data passed verbatim to SCLP ET 24 */
 } __packed;
 
+void sclp_early_set_buffer(void *sccb);
 int sclp_early_read_info(void);
 int sclp_early_read_storage_info(void);
 int sclp_early_get_core_info(struct sclp_core_info *info);
diff --git a/arch/s390/include/asm/setup.h b/arch/s390/include/asm/setup.h
index cf285f57579f..b72714c632d7 100644
--- a/arch/s390/include/asm/setup.h
+++ b/arch/s390/include/asm/setup.h
@@ -7,15 +7,13 @@
 #define _ASM_S390_SETUP_H
 
 #include <linux/bits.h>
-#include <asm/sclp.h>
 #include <uapi/asm/setup.h>
 #include <linux/build_bug.h>
 
 #define EP_OFFSET		0x10008
 #define EP_STRING		"S390EP"
 #define PARMAREA		0x10400
-#define EARLY_SCCB_OFFSET	0x11000
-#define HEAD_END		(EARLY_SCCB_OFFSET + EXT_SCCB_READ_SCP)
+#define HEAD_END		0x11000
 
 /*
  * Machine features detected in early.c