1 files changed, 46 insertions, 0 deletions
diff --git a/include/linux/kho/abi/kexec_metadata.h b/include/linux/kho/abi/kexec_metadata.h
new file mode 100644
index 000000000000..e9e3f7e38a7c
--- /dev/null
+++ b/include/linux/kho/abi/kexec_metadata.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/**
+ * DOC: Kexec Metadata ABI
+ *
+ * The "kexec-metadata" subtree stores optional metadata about the kexec chain.
+ * It is registered via kho_add_subtree(), keeping it independent from the core
+ * KHO ABI. This allows the metadata format to evolve without affecting other
+ * KHO consumers.
+ *
+ * The metadata is stored as a plain C struct rather than FDT format for
+ * simplicity and direct field access.
+ *
+ * Copyright (c) 2026 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2026 Breno Leitao <leitao@debian.org>
+ */
+
+#ifndef _LINUX_KHO_ABI_KEXEC_METADATA_H
+#define _LINUX_KHO_ABI_KEXEC_METADATA_H
+
+#include <linux/types.h>
+#include <linux/utsname.h>
+
+#define KHO_KEXEC_METADATA_VERSION 1
+
+/**
+ * struct kho_kexec_metadata - Kexec metadata passed between kernels
+ * @version: ABI version of this struct (must be first field)
+ * @previous_release: Kernel version string that initiated the kexec
+ * @kexec_count: Number of kexec boots since last cold boot
+ *
+ * This structure is preserved across kexec and allows the new kernel to
+ * identify which kernel it was booted from and how many kexec reboots
+ * have occurred.
+ *
+ * __NEW_UTS_LEN is part of uABI, so it safe to use it in here.
+ */
+struct kho_kexec_metadata {
+	u32 version;
+	char previous_release[__NEW_UTS_LEN + 1];
+	u32 kexec_count;
+} __packed;
+
+#define KHO_METADATA_NODE_NAME "kexec-metadata"
+
+#endif /* _LINUX_KHO_ABI_KEXEC_METADATA_H */