s390/decompressor: get rid of .bss usage

Using .bss in early code should be avoided. It might overlay initrd
image or not yet be initialized. Clean up the last couple of places in
the decompressor's code where .bss is used and enfore no .bss usage
check on boot/compressed/misc.c. In particular:
- initializing free_mem_ptr and free_mem_end_ptr with values guarantee
that these variables won't end up in the .bss section.
- define STATIC_RW_DATA to go into .data section.

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

arch/s390/boot/compressed/Makefile

@@ -62,6 +62,6 @@ OBJCOPYFLAGS_piggy.o := -I binary -O elf64-s390 -B s390:64-bit --rename-section
 $(obj)/piggy.o: $(obj)/vmlinux.bin$(suffix-y) FORCE
 	$(call if_changed,objcopy)
 
-chkbss := $(filter-out $(obj)/misc.o $(obj)/piggy.o $(obj)/info.o,$(OBJECTS))
+chkbss := $(filter-out $(obj)/piggy.o $(obj)/info.o,$(OBJECTS))
 chkbss-target := $(obj)/vmlinux.bin
 include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/boot/compressed/misc.c

@@ -11,12 +11,14 @@
 #include <asm/page.h>
 #include <asm/sclp.h>
 #include <asm/ipl.h>
+#include <asm/sections.h>
 #include "decompressor.h"
 
 /*
  * gzip declarations
  */
 #define STATIC static
+#define STATIC_RW_DATA static __section(.data)
 
 #undef memset
 #undef memcpy
@@ -26,21 +28,20 @@
 
 /* Symbols defined by linker scripts */
 extern char _end[];
-extern char _bss[], _ebss[];
 extern unsigned char _compressed_start[];
 extern unsigned char _compressed_end[];
 
 static void error(char *m);
 
-static unsigned long free_mem_ptr;
-static unsigned long free_mem_end_ptr;
-
 #ifdef CONFIG_HAVE_KERNEL_BZIP2
 #define HEAP_SIZE	0x400000
 #else
 #define HEAP_SIZE	0x10000
 #endif
 
+static unsigned long free_mem_ptr = (unsigned long) _end;
+static unsigned long free_mem_end_ptr = (unsigned long) _end + HEAP_SIZE;
+
 #ifdef CONFIG_KERNEL_GZIP
 #include "../../../../lib/decompress_inflate.c"
 #endif
@@ -102,14 +103,6 @@ void *decompress_kernel(void)
 	}
 #endif
 
-	/*
-	 * Clear bss section. free_mem_ptr and free_mem_end_ptr need to be
-	 * initialized afterwards since they reside in bss.
-	 */
-	memset(_bss, 0, _ebss - _bss);
-	free_mem_ptr = (unsigned long) _end;
-	free_mem_end_ptr = free_mem_ptr + HEAP_SIZE;
-
 	__decompress(_compressed_start, _compressed_end - _compressed_start,
 		     NULL, NULL, output, 0, NULL, error);
 	return output;