The patch titled
Subject: kernel/Kconfig.kexec: drop select of KEXEC for CRASH_DUMP
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Baoquan He <bhe@xxxxxxxxxx>
Subject: kernel/Kconfig.kexec: drop select of KEXEC for CRASH_DUMP
Date: Tue, 28 Nov 2023 13:44:57 +0800
Ignat Korchagin complained that a potential config regression was
introduced by commit 89cde455915f ("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@xxxxxxxxxx/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@xxxxxxxxxx
Fixes: commit 89cde455915f ("kexec: consolidate kexec and crash options into kernel/Kconfig.kexec")
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Reported-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx>
Tested-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx> [compile-time only]
Tested-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Reviewed-by: Eric DeVolder <eric_devolder@xxxxxxxxx>
Tested-by: Eric DeVolder <eric_devolder@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/kexec.h | 4 ----
arch/arm/kernel/Makefile | 2 +-
kernel/Kconfig.kexec | 1 -
3 files changed, 1 insertion(+), 6 deletions(-)
--- a/arch/arm/include/asm/kexec.h~kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump
+++ a/arch/arm/include/asm/kexec.h
@@ -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_p
#endif /* __ASSEMBLY__ */
-#endif /* CONFIG_KEXEC */
-
#endif /* _ARM_KEXEC_H */
--- a/arch/arm/kernel/Makefile~kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump
+++ a/arch/arm/kernel/Makefile
@@ -59,7 +59,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += entry-f
obj-$(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
--- a/kernel/Kconfig.kexec~kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump
+++ a/kernel/Kconfig.kexec
@@ -99,7 +99,6 @@ 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
_
Patches currently in -mm which might be from bhe@xxxxxxxxxx are
drivers-base-cpu-crash-data-showing-should-depends-on-kexec_core.patch
kernel-kconfigkexec-drop-select-of-kexec-for-crash_dump.patch
resource-add-walk_system_ram_res_rev.patch
kexec_file-load-kernel-at-top-of-system-ram-if-required.patch
