s390: introduce .boot.preserved.data section

Introduce .boot.preserve.data section which is similar to .boot.data and
"shared" between the decompressor code and the decompressed kernel. The
decompressor will store values in it, and copy over to the decompressed
image before starting it. This method allows to avoid using pre-defined
addresses and other hacks to pass values between those boot phases.

Unlike .boot.data section .boot.preserved.data is NOT a part of init data,
and hence will be preserved for the kernel life time.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

6 files changed, 31 insertions, 0 deletions

diff --git a/arch/s390/boot/compressed/decompressor.h b/arch/s390/boot/compressed/decompressor.h
index e1c1f2ec60f4..424cf524aac1 100644
--- a/arch/s390/boot/compressed/decompressor.h
+++ b/arch/s390/boot/compressed/decompressor.h
@@ -17,6 +17,8 @@ struct vmlinux_info {
 	unsigned long bss_size;		/* uncompressed image .bss size */
 	unsigned long bootdata_off;
 	unsigned long bootdata_size;
+	unsigned long bootdata_preserved_off;
+	unsigned long bootdata_preserved_size;
 };
 
 extern char _vmlinux_info[];
diff --git a/arch/s390/boot/compressed/vmlinux.lds.S b/arch/s390/boot/compressed/vmlinux.lds.S
index 7efc3938f595..1c8ef393c656 100644
--- a/arch/s390/boot/compressed/vmlinux.lds.S
+++ b/arch/s390/boot/compressed/vmlinux.lds.S
@@ -34,6 +34,7 @@ SECTIONS
 		_edata = . ;
 	}
 	BOOT_DATA
+	BOOT_DATA_PRESERVED
 
 	/*
 	 * uncompressed image info used by the decompressor it should match
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index bdfc5549a299..57d7f9446e29 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -6,6 +6,7 @@
 #include "boot.h"
 
 extern char __boot_data_start[], __boot_data_end[];
+extern char __boot_data_preserved_start[], __boot_data_preserved_end[];
 
 void error(char *x)
 {
@@ -43,6 +44,9 @@ static void copy_bootdata(void)
 	if (__boot_data_end - __boot_data_start != vmlinux.bootdata_size)
 		error(".boot.data section size mismatch");
 	memcpy((void *)vmlinux.bootdata_off, __boot_data_start, vmlinux.bootdata_size);
+	if (__boot_data_preserved_end - __boot_data_preserved_start != vmlinux.bootdata_preserved_size)
+		error(".boot.preserved.data section size mismatch");
+	memcpy((void *)vmlinux.bootdata_preserved_off, __boot_data_preserved_start, vmlinux.bootdata_preserved_size);
 }
 
 void startup_kernel(void)
diff --git a/arch/s390/include/asm/sections.h b/arch/s390/include/asm/sections.h
index 7afe4620685c..29e55739b516 100644
--- a/arch/s390/include/asm/sections.h
+++ b/arch/s390/include/asm/sections.h
@@ -16,4 +16,11 @@
  */
 #define __bootdata(var) __section(.boot.data.var) var
 
+/*
+ * .boot.preserved.data is similar to .boot.data, but it is not part of the
+ * .init section and thus will be preserved for later use in the decompressed
+ * kernel.
+ */
+#define __bootdata_preserved(var) __section(.boot.preserved.data.var) var
+
 #endif
diff --git a/arch/s390/include/asm/vmlinux.lds.h b/arch/s390/include/asm/vmlinux.lds.h
index 2d127f900352..cbe670a6861b 100644
--- a/arch/s390/include/asm/vmlinux.lds.h
+++ b/arch/s390/include/asm/vmlinux.lds.h
@@ -18,3 +18,16 @@
 		*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.boot.data*)))		\
 		__boot_data_end = .;					\
 	}
+
+/*
+ * .boot.preserved.data is similar to .boot.data, but it is not part of the
+ * .init section and thus will be preserved for later use in the decompressed
+ * kernel.
+ */
+#define BOOT_DATA_PRESERVED						\
+	. = ALIGN(PAGE_SIZE);						\
+	.boot.preserved.data : {					\
+		__boot_data_preserved_start = .;			\
+		*(SORT_BY_ALIGNMENT(SORT_BY_NAME(.boot.preserved.data*))) \
+		__boot_data_preserved_end = .;				\
+	}
diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 8429ab079715..6ef9c62bb01b 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -72,6 +72,7 @@ SECTIONS
 	__end_ro_after_init = .;
 
 	RW_DATA_SECTION(0x100, PAGE_SIZE, THREAD_SIZE)
+	BOOT_DATA_PRESERVED
 
 	_edata = .;		/* End of data section */
 
@@ -161,6 +162,9 @@ SECTIONS
 		QUAD(__bss_stop - __bss_start)			/* bss_size */
 		QUAD(__boot_data_start)				/* bootdata_off */
 		QUAD(__boot_data_end - __boot_data_start)	/* bootdata_size */
+		QUAD(__boot_data_preserved_start)		/* bootdata_preserved_off */
+		QUAD(__boot_data_preserved_end -
+		     __boot_data_preserved_start)		/* bootdata_preserved_size */
 	} :NONE
 
 	/* Debugging sections.	*/