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kernel/Kconfig.kexec: drop select of KEXEC for CRASH_DUMP

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Ignat Korchagin complained that a potential config regression was
introduced by commit 89cde45591 ("kexec: consolidate kexec and crash
options into kernel/Kconfig.kexec").  Before the commit, CONFIG_CRASH_DUMP
has no dependency on CONFIG_KEXEC.  After the commit, CRASH_DUMP selects
KEXEC.  That enforces system to have CONFIG_KEXEC=y as long as
CONFIG_CRASH_DUMP=Y which people may not want.

In Ignat's case, he sets CONFIG_CRASH_DUMP=y, CONFIG_KEXEC_FILE=y and
CONFIG_KEXEC=n because kexec_load interface could have security issue if
kernel/initrd has no chance to be signed and verified.

CRASH_DUMP has select of KEXEC because Eric, author of above commit, met a
LKP report of build failure when posting patch of earlier version.  Please
see below link to get detail of the LKP report:

    https://lore.kernel.org/all/3e8eecd1-a277-2cfb-690e-5de2eb7b988e@oracle.com/T/#u

In fact, that LKP report is triggered because arm's <asm/kexec.h> is
wrapped in CONFIG_KEXEC ifdeffery scope.  That is wrong.  CONFIG_KEXEC
controls the enabling/disabling of kexec_load interface, but not kexec
feature.  Removing the wrongly added CONFIG_KEXEC ifdeffery scope in
<asm/kexec.h> of arm allows us to drop the select KEXEC for CRASH_DUMP. 
Meanwhile, change arch/arm/kernel/Makefile to let machine_kexec.o
relocate_kernel.o depend on KEXEC_CORE.

Link: https://lkml.kernel.org/r/20231128054457.659452-1-bhe@redhat.com
Fixes: 89cde45591 ("kexec: consolidate kexec and crash options into kernel/Kconfig.kexec")
Signed-off-by: Baoquan He <bhe@redhat.com>
Reported-by: Ignat Korchagin <ignat@cloudflare.com>
Tested-by: Ignat Korchagin <ignat@cloudflare.com>	[compile-time only]
Tested-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Eric DeVolder <eric_devolder@yahoo.com>
Tested-by: Eric DeVolder <eric_devolder@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baoquan He 2023-11-28 13:44:57 +08:00 committed by Andrew Morton
parent 8e92157d7f
commit dccf78d39f
3 changed files with 1 additions and 6 deletions
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4
arch/arm/include/asm/kexec.h
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@ -2,8 +2,6 @@
#ifndef _ARM_KEXEC_H
#define _ARM_KEXEC_H
#ifdef CONFIG_KEXEC
/* Maximum physical address we can use pages from */
#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
/* Maximum address we can reach in physical address mode */
@ -82,6 +80,4 @@ static inline struct page *boot_pfn_to_page(unsigned long boot_pfn)
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_KEXEC */
#endif /* _ARM_KEXEC_H */

2
arch/arm/kernel/Makefile
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@ -59,7 +59,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += entry-ftrace.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o insn.o patch.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o patch.o
obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o
# Main staffs in KPROBES are in arch/arm/probes/ .
obj-$(CONFIG_KPROBES) += patch.o insn.o
obj-$(CONFIG_OABI_COMPAT) += sys_oabi-compat.o

1
kernel/Kconfig.kexec
View File

@ -97,7 +97,6 @@ config CRASH_DUMP
depends on ARCH_SUPPORTS_KEXEC
select CRASH_CORE
select KEXEC_CORE
select KEXEC
help
Generate crash dump after being started by kexec.
This should be normally only set in special crash dump kernels