linux-kernel - [PATCH 4/5] crash: remove dependency of FA_DUMP on CRASH

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Date: Fri,  5 Jan 2024 18:33:04 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org,
	kexec@...ts.infradead.org,
	hbathini@...ux.ibm.com,
	arnd@...db.de,
	ignat@...udflare.com,
	eric_devolder@...oo.com,
	viro@...iv.linux.org.uk,
	ebiederm@...ssion.com,
	x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-riscv@...ts.infradead.org,
	linux-fsdevel@...r.kernel.org,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH 4/5] crash: remove dependency of FA_DUMP on CRASH_DUMP

In kdump kernel, /proc/vmcore is an elf file which maps the crashed kernel's
read_from_oldmemmemory content. Its elf header is constructed in 1st kernel and passed
to kdump kernel via elfcorehdr_addr. Config CRASH_DUMP enables the code
of 1st kernel's old memory accessing in different architectures.

Currently, config FA_DUMP has dependency on CRASH_DUMP because fadump
needs access global variable 'elfcorehdr_addr' to judge if it's in
kdump kernel within function is_kdump_kernel(). In kernel/crash_dump.c,
variable 'elfcorehdr_addr' is defined, and function setup_elfcorehdr()
is used to parse kernel parameter 'elfcorehdr' to fetch the passed
value of elfcorehdr_addr. With the need of accessing elfcorehdr_addr,
FA_DUMP doesn't have to depends on CRASH_DUMP.

To remove the dependency of FA_DUMP on CRASH_DUMP to avoid confusion,
rename kernel/crash_dump.c to kernel/elfcorehdr.c, and build it when
CONFIG_VMCORE_INFO is ebabled. With this, FA_DUMP doesn't need to depend
on CRASH_DUMP.

In file included from kernel/vmcore_info.c:25:
kernel/kexec_internal.h:11:54: warning: ‘struct kexec_segment’ declared inside parameter list will not be visible outside of this definition or declaration
   11 | int kimage_load_segment(struct kimage *image, struct kexec_segment *segment);
      |                                                      ^~~~~~~~~~~~~

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 arch/powerpc/Kconfig                  | 1 -
 kernel/Makefile                       | 3 +--
 kernel/{crash_dump.c => elfcorehdr.c} | 0
 kernel/kexec_internal.h               | 2 ++
 4 files changed, 3 insertions(+), 3 deletions(-)
 rename kernel/{crash_dump.c => elfcorehdr.c} (100%)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index d391e8cddf6c..22a04891c68d 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -691,7 +691,6 @@ config FA_DUMP
 	depends on PPC64 && (PPC_RTAS || PPC_POWERNV)
 	select VMCORE_INFO
 	select CRASH_RESERVE
-	select CRASH_DUMP
 	help
 	  A robust mechanism to get reliable kernel crash dump with
 	  assistance from firmware. This approach does not use kexec,
diff --git a/kernel/Makefile b/kernel/Makefile
index 08980e5c2080..25ac9345ef79 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -68,7 +68,7 @@ obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_KALLSYMS_SELFTEST) += kallsyms_selftest.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
-obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o
+obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o elfcorehdr.o
 obj-$(CONFIG_CRASH_RESERVE) += crash_reserve.o
 obj-$(CONFIG_KEXEC_CORE) += kexec_core.o
 obj-$(CONFIG_KEXEC) += kexec.o
@@ -120,7 +120,6 @@ obj-$(CONFIG_PERF_EVENTS) += events/
 
 obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
 obj-$(CONFIG_PADATA) += padata.o
-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_JUMP_LABEL) += jump_label.o
 obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
 obj-$(CONFIG_TORTURE_TEST) += torture.o
diff --git a/kernel/crash_dump.c b/kernel/elfcorehdr.c
similarity index 100%
rename from kernel/crash_dump.c
rename to kernel/elfcorehdr.c
diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index 74da1409cd14..2595defe8c0d 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -4,6 +4,8 @@
 
 #include <linux/kexec.h>
 
+struct kexec_segment;
+
 struct kimage *do_kimage_alloc_init(void);
 int sanity_check_segment_list(struct kimage *image);
 void kimage_free_page_list(struct list_head *list);
-- 
2.41.0