Commit 2e83e0eb authored by Vasily Gorbik's avatar Vasily Gorbik
Browse files

s390: clean .bss before running uncompressed kernel 



Clean uncompressed kernel .bss section in the startup code before
the uncompressed kernel is executed. At this point of time initrd and
certificates have been already rescued. Uncompressed kernel .bss size
is known from vmlinux_info. It is also taken into consideration during
uncompressed kernel positioning by kaslr (so it is safe to clean it).

With that uncompressed kernel is starting with .bss section zeroed and
no .bss section usage restrictions apply. Which makes chkbss checks for
uncompressed kernel objects obsolete and they can be removed.

early_nobss.c is also not needed anymore. Parts of it which are still
relevant are moved to early.c. Kasan initialization code is now called
directly from head64 (early.c is instrumented and should not be
executed before kasan shadow memory is set up).

Reviewed-by: default avatarPhilipp Rudo <prudo@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 19413fe0

arch/s390/boot/startup.c

+6 −0
Original line number Diff line number Diff line
@@ -112,6 +112,11 @@ static void handle_relocs(unsigned long offset) 
	}

}



static void clear_bss_section(void)

{

	memset((void *)vmlinux.default_lma + vmlinux.image_size, 0, vmlinux.bss_size);

}



void startup_kernel(void)

{

	unsigned long random_lma;
@@ -151,6 +156,7 @@ void startup_kernel(void) 
	} else if (__kaslr_offset)

		memcpy((void *)vmlinux.default_lma, img, vmlinux.image_size);



	clear_bss_section();

	copy_bootdata();

	if (IS_ENABLED(CONFIG_RELOCATABLE))

		handle_relocs(__kaslr_offset);

arch/s390/kernel/Makefile

+1 −12
Original line number Diff line number Diff line
@@ -10,20 +10,12 @@ CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) 


# Do not trace early setup code

CFLAGS_REMOVE_early.o		= $(CC_FLAGS_FTRACE)

CFLAGS_REMOVE_early_nobss.o	= $(CC_FLAGS_FTRACE)



endif



GCOV_PROFILE_early.o		:= n

GCOV_PROFILE_early_nobss.o	:= n



KCOV_INSTRUMENT_early.o		:= n

KCOV_INSTRUMENT_early_nobss.o	:= n



UBSAN_SANITIZE_early.o		:= n

UBSAN_SANITIZE_early_nobss.o	:= n



KASAN_SANITIZE_early_nobss.o	:= n

KASAN_SANITIZE_ipl.o		:= n

KASAN_SANITIZE_machine_kexec.o	:= n
@@ -48,7 +40,7 @@ CFLAGS_ptrace.o += -DUTS_MACHINE='"$(UTS_MACHINE)"' 


obj-y	:= traps.o time.o process.o base.o early.o setup.o idle.o vtime.o

obj-y	+= processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o nmi.o

obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o early_nobss.o

obj-y	+= debug.o irq.o ipl.o dis.o diag.o vdso.o

obj-y	+= sysinfo.o lgr.o os_info.o machine_kexec.o pgm_check.o

obj-y	+= runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o

obj-y	+= entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
@@ -90,6 +82,3 @@ obj-$(CONFIG_TRACEPOINTS) += trace.o 
# vdso

obj-y				+= vdso64/

obj-$(CONFIG_COMPAT_VDSO)	+= vdso32/
 


chkbss := head64.o early_nobss.o

include $(srctree)/arch/s390/scripts/Makefile.chkbss

arch/s390/kernel/early.c

+16 −0
Original line number Diff line number Diff line
@@ -32,6 +32,21 @@ 
#include <asm/boot_data.h>

#include "entry.h"



static void __init reset_tod_clock(void)

{

	u64 time;



	if (store_tod_clock(&time) == 0)

		return;

	/* TOD clock not running. Set the clock to Unix Epoch. */

	if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)

		disabled_wait();



	memset(tod_clock_base, 0, 16);

	*(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;

	S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;

}



/*

 * Initialize storage key for kernel pages

 */
@@ -301,6 +316,7 @@ static void __init check_image_bootable(void) 


void __init startup_init(void)

{

	reset_tod_clock();

	check_image_bootable();

	time_early_init();

	init_kernel_storage_key();

arch/s390/kernel/early_nobss.c

deleted100644 → 0
+0 −45
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 *    Copyright IBM Corp. 2007, 2018

 */



/*

 * Early setup functions which may not rely on an initialized bss

 * section. The last thing that is supposed to happen here is

 * initialization of the bss section.

 */



#include <linux/processor.h>

#include <linux/string.h>

#include <asm/sections.h>

#include <asm/lowcore.h>

#include <asm/timex.h>

#include <asm/kasan.h>

#include "entry.h"



static void __init reset_tod_clock(void)

{

	u64 time;



	if (store_tod_clock(&time) == 0)

		return;

	/* TOD clock not running. Set the clock to Unix Epoch. */

	if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)

		disabled_wait();



	memset(tod_clock_base, 0, 16);

	*(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;

	S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;

}



static void __init clear_bss_section(void)

{

	memset(__bss_start, 0, __bss_stop - __bss_start);

}



void __init startup_init_nobss(void)

{

	reset_tod_clock();

	clear_bss_section();

	kasan_early_init();

}

arch/s390/kernel/head64.S

+3 −5
Original line number Diff line number Diff line
@@ -34,11 +34,9 @@ ENTRY(startup_continue) 
	larl	%r14,init_task

	stg	%r14,__LC_CURRENT

	larl	%r15,init_thread_union+THREAD_SIZE-STACK_FRAME_OVERHEAD

#

# Early setup functions that may not rely on an initialized bss section,

# like moving the initrd. Returns with an initialized bss section.

#

	brasl	%r14,startup_init_nobss

#ifdef CONFIG_KASAN

	brasl	%r14,kasan_early_init

#endif

#

# Early machine initialization and detection functions.

#

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