s390/boot: enable .bss section for compressed kernel

- Support static uninitialized variables in compressed kernel.
- Remove chkbss script
- Get rid of workarounds for not having .bss section

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/Makefile

@@ -73,7 +73,3 @@ $(obj)/startup.a: $(OBJECTS) FORCE
 install:
 	sh -x  $(srctree)/$(obj)/install.sh $(KERNELRELEASE) $(obj)/bzImage \
 	      System.map "$(INSTALL_PATH)"
-
-chkbss := $(obj-y)
-chkbss-target := startup.a
-include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/boot/compressed/Makefile

@@ -62,7 +62,3 @@ $(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE
 OBJCOPYFLAGS_piggy.o := -I binary -O elf64-s390 -B s390:64-bit --rename-section .data=.vmlinux.bin.compressed
 $(obj)/piggy.o: $(obj)/vmlinux.bin$(suffix-y) FORCE
 	$(call if_changed,objcopy)
-
-chkbss := $(filter-out piggy.o info.o, $(obj-y))
-chkbss-target := vmlinux.bin
-include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/boot/compressed/decompressor.c

@@ -16,7 +16,6 @@
  * gzip declarations
  */
 #define STATIC static
-#define STATIC_RW_DATA static __section(.data)
 
 #undef memset
 #undef memcpy

arch/s390/boot/compressed/vmlinux.lds.S

@@ -58,6 +58,19 @@ SECTIONS
 	BOOT_DATA
 	BOOT_DATA_PRESERVED
 
+	/*
+	 * This is the BSS section of the decompressor and not of the decompressed Linux kernel.
+	 * It will consume place in the decompressor's image.
+	 */
+	. = ALIGN(8);
+	.bss : {
+		_bss = . ;
+		*(.bss)
+		*(.bss.*)
+		*(COMMON)
+		_ebss = .;
+	}
+
 	/*
 	 * uncompressed image info used by the decompressor it should match
 	 * struct vmlinux_info. It comes from .vmlinux.info section of
@@ -81,15 +94,6 @@ SECTIONS
 		FILL(0xff);
 		. = ALIGN(4096);
 	}
-	. = ALIGN(256);
-	.bss : {
-		_bss = . ;
-		*(.bss)
-		*(.bss.*)
-		*(COMMON)
-		. = ALIGN(8);	/* For convenience during zeroing */
-		_ebss = .;
-	}
 	_end = .;
 
 	/* Sections to be discarded */

arch/s390/boot/head.S

@@ -313,6 +313,12 @@ ENTRY(startup_kdump)
 	spt	6f-.LPG0(%r13)
 	mvc	__LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
 	l	%r15,.Lstack-.LPG0(%r13)
+	// Clear decompressor's BSS section
+	larl	%r2,_bss
+	slgr	%r3,%r3
+	larl	%r4,_ebss
+	slgr	%r4,%r2
+	brasl	%r14,memset
 	brasl	%r14,verify_facilities
 	brasl	%r14,startup_kernel
 

arch/s390/boot/ipl_parm.c

@@ -21,7 +21,7 @@ unsigned long __bootdata(memory_end);
 int __bootdata(memory_end_set);
 int __bootdata(noexec_disabled);
 
-int kaslr_enabled __section(.data);
+int kaslr_enabled;
 
 static inline int __diag308(unsigned long subcode, void *addr)
 {
@@ -209,7 +209,7 @@ static void modify_fac_list(char *str)
 	check_cleared_facilities();
 }
 
-static char command_line_buf[COMMAND_LINE_SIZE] __section(.data);
+static char command_line_buf[COMMAND_LINE_SIZE];
 void parse_boot_command_line(void)
 {
 	char *param, *val;

arch/s390/boot/startup.c

@@ -120,6 +120,9 @@ static void handle_relocs(unsigned long offset)
 	}
 }
 
+/*
+ * This function clears the BSS section of the decompressed Linux kernel and NOT the decompressor's.
+ */
 static void clear_bss_section(void)
 {
 	memset((void *)vmlinux.default_lma + vmlinux.image_size, 0, vmlinux.bss_size);

arch/s390/kernel/setup.c

@@ -307,7 +307,7 @@ void machine_power_off(void)
 void (*pm_power_off)(void) = machine_power_off;
 EXPORT_SYMBOL_GPL(pm_power_off);
 
-void *restart_stack __section(.data);
+void *restart_stack;
 
 unsigned long stack_alloc(void)
 {

arch/s390/scripts/Makefile.chkbss

-# SPDX-License-Identifier: GPL-2.0
-
-chkbss-target ?= built-in.a
-$(obj)/$(chkbss-target): chkbss
-
-chkbss-files := $(addsuffix .chkbss, $(chkbss))
-clean-files += $(chkbss-files)
-
-PHONY += chkbss
-chkbss: $(addprefix $(obj)/, $(chkbss-files))
-
-quiet_cmd_chkbss = CHKBSS  $<
-      cmd_chkbss = \
-	if ! $(OBJSIZE) --common $< | $(AWK) 'END { if ($$3) exit 1 }'; then \
-		echo "error: $< .bss section is not empty" >&2; exit 1; \
-	fi; \
-	touch $@;
-
-$(obj)/%.o.chkbss: $(obj)/%.o
-	$(call cmd,chkbss)