[PATCH v5 1/3] kexec: move sysfs entries to /sys/kernel/kexec

[PATCH v5 1/3] kexec: move sysfs entries to /sys/kernel/kexec

[Sourabh Jain]

Several kexec and kdump sysfs entries are currently placed directly
under /sys/kernel/, which clutters the directory and makes it harder to
identify unrelated entries. To improve organization and readability,
these entries are now moved under a dedicated directory,
/sys/kernel/kexec.

For backward compatibility, symlinks are created at the old locations
so that existing tools and scripts continue to work. These symlinks can
be removed in the future once users have switched to the new path.

While creating symlinks, entries are added in /sys/kernel/ that point
to their new locations under /sys/kernel/kexec/. If an error occurs
while adding a symlink, it is logged but does not stop initialization
of the remaining kexec sysfs symlinks.

The /sys/kernel/<crash_elfcorehdr_size | kexec/crash_elfcorehdr_size>
entry is now controlled by CONFIG_CRASH_DUMP instead of
CONFIG_VMCORE_INFO, as CONFIG_CRASH_DUMP also enables
CONFIG_VMCORE_INFO.

Cc: Aditya Gupta <adityag@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: kexec@lists.infradead.org
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 kernel/kexec_core.c | 91 ++++++++++++++++++++++++++++++++++++++++++++-
 kernel/ksysfs.c     | 68 +--------------------------------
 2 files changed, 91 insertions(+), 68 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 51b1e0985eac..b90d48f77dfb 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1231,6 +1231,47 @@ int kernel_kexec(void)
 	return error;
 }
 
+static ssize_t loaded_show(struct kobject *kobj,
+				 struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", !!kexec_image);
+}
+static struct kobj_attribute loaded_attr = __ATTR_RO(loaded);
+
+#ifdef CONFIG_CRASH_DUMP
+static ssize_t crash_loaded_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%d\n", kexec_crash_loaded());
+}
+static struct kobj_attribute crash_loaded_attr = __ATTR_RO(crash_loaded);
+
+static ssize_t crash_size_show(struct kobject *kobj,
+				       struct kobj_attribute *attr, char *buf)
+{
+	ssize_t size = crash_get_memory_size();
+
+	if (size < 0)
+		return size;
+
+	return sysfs_emit(buf, "%zd\n", size);
+}
+
+static ssize_t crash_size_store(struct kobject *kobj,
+				struct kobj_attribute *attr,
+				const char *buf, size_t count)
+{
+	unsigned long cnt;
+	int ret;
+
+	if (kstrtoul(buf, 0, &cnt))
+		return -EINVAL;
+
+	ret = crash_shrink_memory(cnt);
+	return ret < 0 ? ret : count;
+}
+static struct kobj_attribute crash_size_attr = __ATTR_RW(crash_size);
+
 #ifdef CONFIG_CRASH_RESERVE
 static ssize_t crash_cma_ranges_show(struct kobject *kobj,
 				     struct kobj_attribute *attr, char *buf)
@@ -1247,18 +1288,59 @@ static ssize_t crash_cma_ranges_show(struct kobject *kobj,
 	return len;
 }
 static struct kobj_attribute crash_cma_ranges_attr = __ATTR_RO(crash_cma_ranges);
+#endif /* CONFIG_CRASH_RESERVE */
+
+#ifdef CONFIG_CRASH_HOTPLUG
+static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
+			       struct kobj_attribute *attr, char *buf)
+{
+	unsigned int sz = crash_get_elfcorehdr_size();
+
+	return sysfs_emit(buf, "%u\n", sz);
+}
+static struct kobj_attribute crash_elfcorehdr_size_attr = __ATTR_RO(crash_elfcorehdr_size);
+#endif /* CONFIG_CRASH_HOTPLUG */
+#endif /* CONFIG_CRASH_DUMP */
 
 static struct attribute *kexec_attrs[] = {
+	&loaded_attr.attr,
+#ifdef CONFIG_CRASH_DUMP
+	&crash_loaded_attr.attr,
+	&crash_size_attr.attr,
+#ifdef CONFIG_CRASH_RESERVE
 	&crash_cma_ranges_attr.attr,
+#endif
+#ifdef CONFIG_CRASH_HOTPLUG
+	&crash_elfcorehdr_size_attr.attr,
+#endif
+#endif
 	NULL
 };
 
+struct kexec_link_entry {
+	const char *target;
+	const char *name;
+};
+
+static struct kexec_link_entry kexec_links[] = {
+	{ "loaded", "kexec_loaded" },
+#ifdef CONFIG_CRASH_DUMP
+	{ "crash_loaded", "kexec_crash_loaded" },
+	{ "crash_size", "kexec_crash_size" },
+#ifdef CONFIG_CRASH_HOTPLUG
+	{ "crash_elfcorehdr_size", "crash_elfcorehdr_size" },
+#endif
+#endif
+
+};
+
 static struct kobject *kexec_kobj;
 ATTRIBUTE_GROUPS(kexec);
 
 static int __init init_kexec_sysctl(void)
 {
 	int error;
+	int i;
 
 	kexec_kobj = kobject_create_and_add("kexec", kernel_kobj);
 	if (!kexec_kobj) {
@@ -1270,6 +1352,14 @@ static int __init init_kexec_sysctl(void)
 	if (error)
 		goto kset_exit;
 
+	for (i = 0; i < ARRAY_SIZE(kexec_links); i++) {
+		error = compat_only_sysfs_link_entry_to_kobj(kernel_kobj, kexec_kobj,
+							     kexec_links[i].target,
+							     kexec_links[i].name);
+		if (error)
+			pr_err("Unable to create %s symlink (%d)", kexec_links[i].name, error);
+	}
+
 	return 0;
 
 kset_exit:
@@ -1278,4 +1368,3 @@ static int __init init_kexec_sysctl(void)
 }
 
 subsys_initcall(init_kexec_sysctl);
-#endif /* CONFIG_CRASH_RESERVE */
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index eefb67d9883c..a9e6354d9e25 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -12,7 +12,7 @@
 #include <linux/sysfs.h>
 #include <linux/export.h>
 #include <linux/init.h>
-#include <linux/kexec.h>
+#include <linux/vmcore_info.h>
 #include <linux/profile.h>
 #include <linux/stat.h>
 #include <linux/sched.h>
@@ -119,50 +119,6 @@ static ssize_t profiling_store(struct kobject *kobj,
 KERNEL_ATTR_RW(profiling);
 #endif
 
-#ifdef CONFIG_KEXEC_CORE
-static ssize_t kexec_loaded_show(struct kobject *kobj,
-				 struct kobj_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "%d\n", !!kexec_image);
-}
-KERNEL_ATTR_RO(kexec_loaded);
-
-#ifdef CONFIG_CRASH_DUMP
-static ssize_t kexec_crash_loaded_show(struct kobject *kobj,
-				       struct kobj_attribute *attr, char *buf)
-{
-	return sysfs_emit(buf, "%d\n", kexec_crash_loaded());
-}
-KERNEL_ATTR_RO(kexec_crash_loaded);
-
-static ssize_t kexec_crash_size_show(struct kobject *kobj,
-				       struct kobj_attribute *attr, char *buf)
-{
-	ssize_t size = crash_get_memory_size();
-
-	if (size < 0)
-		return size;
-
-	return sysfs_emit(buf, "%zd\n", size);
-}
-static ssize_t kexec_crash_size_store(struct kobject *kobj,
-				   struct kobj_attribute *attr,
-				   const char *buf, size_t count)
-{
-	unsigned long cnt;
-	int ret;
-
-	if (kstrtoul(buf, 0, &cnt))
-		return -EINVAL;
-
-	ret = crash_shrink_memory(cnt);
-	return ret < 0 ? ret : count;
-}
-KERNEL_ATTR_RW(kexec_crash_size);
-
-#endif /* CONFIG_CRASH_DUMP*/
-#endif /* CONFIG_KEXEC_CORE */
-
 #ifdef CONFIG_VMCORE_INFO
 
 static ssize_t vmcoreinfo_show(struct kobject *kobj,
@@ -174,18 +130,6 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
 }
 KERNEL_ATTR_RO(vmcoreinfo);
 
-#ifdef CONFIG_CRASH_HOTPLUG
-static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
-			       struct kobj_attribute *attr, char *buf)
-{
-	unsigned int sz = crash_get_elfcorehdr_size();
-
-	return sysfs_emit(buf, "%u\n", sz);
-}
-KERNEL_ATTR_RO(crash_elfcorehdr_size);
-
-#endif
-
 #endif /* CONFIG_VMCORE_INFO */
 
 /* whether file capabilities are enabled */
@@ -255,18 +199,8 @@ static struct attribute * kernel_attrs[] = {
 #ifdef CONFIG_PROFILING
 	&profiling_attr.attr,
 #endif
-#ifdef CONFIG_KEXEC_CORE
-	&kexec_loaded_attr.attr,
-#ifdef CONFIG_CRASH_DUMP
-	&kexec_crash_loaded_attr.attr,
-	&kexec_crash_size_attr.attr,
-#endif
-#endif
 #ifdef CONFIG_VMCORE_INFO
 	&vmcoreinfo_attr.attr,
-#ifdef CONFIG_CRASH_HOTPLUG
-	&crash_elfcorehdr_size_attr.attr,
-#endif
 #endif
 #ifndef CONFIG_TINY_RCU
 	&rcu_expedited_attr.attr,
-- 
2.51.1

[PATCH v5 2/3] Documentation/ABI: mark old kexec sysfs deprecated

[Sourabh Jain]

The previous commit ("kexec: move sysfs entries to /sys/kernel/kexec")
moved all existing kexec sysfs entries to a new location. The ABI
document is updated to include a note about the deprecation of the old
kexec sysfs entries.

The following kexec sysfs entries are deprecated:
- /sys/kernel/kexec_loaded
- /sys/kernel/kexec_crash_loaded
- /sys/kernel/kexec_crash_size
- /sys/kernel/crash_elfcorehdr_size

Cc: Aditya Gupta <adityag@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: kexec@lists.infradead.org
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 .../ABI/obsolete/sysfs-kernel-kexec-kdump     | 59 +++++++++++++++++++
 .../ABI/testing/sysfs-kernel-kexec-kdump      | 44 --------------
 2 files changed, 59 insertions(+), 44 deletions(-)
 create mode 100644 Documentation/ABI/obsolete/sysfs-kernel-kexec-kdump

diff --git a/Documentation/ABI/obsolete/sysfs-kernel-kexec-kdump b/Documentation/ABI/obsolete/sysfs-kernel-kexec-kdump
new file mode 100644
index 000000000000..96b4d41721cc
--- /dev/null
+++ b/Documentation/ABI/obsolete/sysfs-kernel-kexec-kdump
@@ -0,0 +1,59 @@
+NOTE: all the ABIs listed in this file are deprecated and will be removed after 2028.
+
+Here are the alternative ABIs:
++------------------------------------+-----------------------------------------+
+| Deprecated                         | Alternative                             |
++------------------------------------+-----------------------------------------+
+| /sys/kernel/kexec_loaded           | /sys/kernel/kexec/loaded                |
++------------------------------------+-----------------------------------------+
+| /sys/kernel/kexec_crash_loaded     | /sys/kernel/kexec/crash_loaded          |
++------------------------------------+-----------------------------------------+
+| /sys/kernel/kexec_crash_size       | /sys/kernel/kexec/crash_size            |
++------------------------------------+-----------------------------------------+
+| /sys/kernel/crash_elfcorehdr_size  | /sys/kernel/kexec/crash_elfcorehdr_size |
++------------------------------------+-----------------------------------------+
+
+
+What:		/sys/kernel/kexec_loaded
+Date:		Jun 2006
+Contact:	kexec@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:		Jun 2006
+Contact:	kexec@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:		Dec 2009
+Contact:	kexec@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/crash_elfcorehdr_size
+Date:		Aug 2023
+Contact:	kexec@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
diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
index 320ec75a4903..7e5e528665db 100644
--- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
+++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
@@ -1,47 +1,3 @@
-What:		/sys/kernel/kexec_loaded
-Date:		Jun 2006
-Contact:	kexec@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:		Jun 2006
-Contact:	kexec@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:		Dec 2009
-Contact:	kexec@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/crash_elfcorehdr_size
-Date:		Aug 2023
-Contact:	kexec@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
-
 What:		/sys/kernel/kexec/crash_cma_ranges
 Date:		Nov 2025
 Contact:	kexec@lists.infradead.org
-- 
2.51.1

[PATCH v5 3/3] 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@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: kexec@lists.infradead.org
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
---
 .../ABI/testing/sysfs-kernel-kexec-kdump      | 52 +++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
index 7e5e528665db..f59051b5d96d 100644
--- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
+++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
@@ -1,3 +1,55 @@
+What:		/sys/kernel/kexec/*
+Date:		Nov 2025
+Contact:	kexec@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@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@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@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@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
+
 What:		/sys/kernel/kexec/crash_cma_ranges
 Date:		Nov 2025
 Contact:	kexec@lists.infradead.org
-- 
2.51.1