[PATCH v2 4/5] kexec: document new kexec and kdump sysfs ABIs

[Sourabh Jain]

Add an ABI document for following kexec and kdump sysfs interface:

- /sys/kernel/kexec/loaded
- /sys/kernel/kexec/crash_loaded
- /sys/kernel/kexec/crash_size
- /sys/kernel/kexec/crash_elfcorehdr_size

Cc: Aditya Gupta <adityag at linux.ibm.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Baoquan he <bhe at redhat.com>
Cc: Dave Young <dyoung at redhat.com>
Cc: Hari Bathini <hbathini at linux.ibm.com>
Cc: Jiri Bohac <jbohac at suse.cz>
Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh at linux.ibm.com>
Cc: Pingfan Liu <piliu at redhat.com>
Cc: Ritesh Harjani (IBM) <ritesh.list at gmail.com>
Cc: Shivang Upadhyay <shivangu at linux.ibm.com>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: linuxppc-dev at lists.ozlabs.org
Cc: kexec at lists.infradead.org
Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
 .../ABI/testing/sysfs-kernel-kexec-kdump      | 51 +++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-kexec-kdump

diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
new file mode 100644
index 000000000000..00c00f380fea
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
@@ -0,0 +1,51 @@
+What:		/sys/kernel/kexec/*
+Date:		Nov 2025
+Contact:	kexec at lists.infradead.org
+Description:
+		The /sys/kernel/kexec/* directory contains sysfs files
+		that provide information about the configuration status
+		of kexec and kdump.
+
+What:		/sys/kernel/kexec/loaded
+Date:		Nov 2025
+Contact:	kexec at lists.infradead.org
+Description:	read only
+		Indicates whether a new kernel image has been loaded
+		into memory using the kexec system call. It shows 1 if
+		a kexec image is present and ready to boot, or 0 if none
+		is loaded.
+User:		kexec tools, kdump service
+
+What:		/sys/kernel/kexec/crash_loaded
+Date:		Nov 2025
+Contact:	kexec at lists.infradead.org
+Description:	read only
+		Indicates whether a crash (kdump) kernel is currently
+		loaded into memory. It shows 1 if a crash kernel has been
+		successfully loaded for panic handling, or 0 if no crash
+		kernel is present.
+User:		Kexec tools, Kdump service
+
+What:		/sys/kernel/kexec/crash_size
+Date:		Nov 2025
+Contact:	kexec at lists.infradead.org
+Description:	read/write
+		Shows the amount of memory reserved for loading the crash
+		(kdump) kernel. It reports the size, in bytes, of the
+		crash kernel area defined by the crashkernel= parameter.
+		This interface also allows reducing the crashkernel
+		reservation by writing a smaller value, and the reclaimed
+		space is added back to the system RAM.
+User:		Kdump service
+
+What:		/sys/kernel/kexec/crash_elfcorehdr_size
+Date:		Nov 2025
+Contact:	kexec at lists.infradead.org
+Description:	read only
+		Indicates the preferred size of the memory buffer for the
+		ELF core header used by the crash (kdump) kernel. It defines
+		how much space is needed to hold metadata about the crashed
+		system, including CPU and memory information. This information
+		is used by the user space utility kexec to support updating the
+		in-kernel kdump image during hotplug operations.
+User:		Kexec tools
-- 
2.51.0