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: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2019-08-11 20:55:18 +02:00
parent 19413fe04f
commit 2e83e0eb85
7 changed files with 26 additions and 68 deletions

View File

@ -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);

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@ -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

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@ -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();

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@ -1,45 +0,0 @@
// 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();
}

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@ -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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@ -11,6 +11,3 @@ lib-$(CONFIG_UPROBES) += probes.o
# Instrumenting memory accesses to __user data (in different address space)
# produce false positives
KASAN_SANITIZE_uaccess.o := n
chkbss := mem.o
include $(srctree)/arch/s390/scripts/Makefile.chkbss

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@ -49,6 +49,3 @@ obj-$(CONFIG_CRASH_DUMP) += sclp_sdias.o zcore.o
hmcdrv-objs := hmcdrv_mod.o hmcdrv_dev.o hmcdrv_ftp.o hmcdrv_cache.o diag_ftp.o sclp_ftp.o
obj-$(CONFIG_HMC_DRV) += hmcdrv.o
chkbss := sclp_early_core.o
include $(srctree)/arch/s390/scripts/Makefile.chkbss