1 files changed, 98 insertions, 0 deletions

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index adf6541f70f9..94762de1fe5f 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -18,7 +18,9 @@
 #include <linux/kexec.h>
 #include <linux/kexec_handover.h>
 #include <linux/kho_radix_tree.h>
+#include <linux/utsname.h>
 #include <linux/kho/abi/kexec_handover.h>
+#include <linux/kho/abi/kexec_metadata.h>
 #include <linux/libfdt.h>
 #include <linux/list.h>
 #include <linux/memblock.h>
@@ -1268,6 +1270,8 @@ EXPORT_SYMBOL_GPL(kho_restore_free);
 struct kho_in {
 	phys_addr_t fdt_phys;
 	phys_addr_t scratch_phys;
+	char previous_release[__NEW_UTS_LEN + 1];
+	u32 kexec_count;
 	struct kho_debugfs dbg;
 };
 
@@ -1392,6 +1396,96 @@ static __init int kho_out_fdt_setup(void)
 	return err;
 }
 
+static void __init kho_in_kexec_metadata(void)
+{
+	struct kho_kexec_metadata *metadata;
+	phys_addr_t metadata_phys;
+	size_t blob_size;
+	int err;
+
+	err = kho_retrieve_subtree(KHO_METADATA_NODE_NAME, &metadata_phys,
+				   &blob_size);
+	if (err)
+		/* This is fine, previous kernel didn't export metadata */
+		return;
+
+	/* Check that, at least, "version" is present */
+	if (blob_size < sizeof(u32)) {
+		pr_warn("kexec-metadata blob too small (%zu bytes)\n",
+			blob_size);
+		return;
+	}
+
+	metadata = phys_to_virt(metadata_phys);
+
+	if (metadata->version != KHO_KEXEC_METADATA_VERSION) {
+		pr_warn("kexec-metadata version %u not supported (expected %u)\n",
+			metadata->version, KHO_KEXEC_METADATA_VERSION);
+		return;
+	}
+
+	if (blob_size < sizeof(*metadata)) {
+		pr_warn("kexec-metadata blob too small for v%u (%zu < %zu)\n",
+			metadata->version, blob_size, sizeof(*metadata));
+		return;
+	}
+
+	/*
+	 * Copy data to the kernel structure that will persist during
+	 * kernel lifetime.
+	 */
+	kho_in.kexec_count = metadata->kexec_count;
+	strscpy(kho_in.previous_release, metadata->previous_release,
+		sizeof(kho_in.previous_release));
+
+	pr_info("exec from: %s (count %u)\n",
+		kho_in.previous_release, kho_in.kexec_count);
+}
+
+/*
+ * Create kexec metadata to pass kernel version and boot count to the
+ * next kernel. This keeps the core KHO ABI minimal and allows the
+ * metadata format to evolve independently.
+ */
+static __init int kho_out_kexec_metadata(void)
+{
+	struct kho_kexec_metadata *metadata;
+	int err;
+
+	metadata = kho_alloc_preserve(sizeof(*metadata));
+	if (IS_ERR(metadata))
+		return PTR_ERR(metadata);
+
+	metadata->version = KHO_KEXEC_METADATA_VERSION;
+	strscpy(metadata->previous_release, init_uts_ns.name.release,
+		sizeof(metadata->previous_release));
+	/* kho_in.kexec_count is set to 0 on cold boot */
+	metadata->kexec_count = kho_in.kexec_count + 1;
+
+	err = kho_add_subtree(KHO_METADATA_NODE_NAME, metadata,
+			      sizeof(*metadata));
+	if (err)
+		kho_unpreserve_free(metadata);
+
+	return err;
+}
+
+static int __init kho_kexec_metadata_init(const void *fdt)
+{
+	int err;
+
+	if (fdt)
+		kho_in_kexec_metadata();
+
+	/* Populate kexec metadata for the possible next kexec */
+	err = kho_out_kexec_metadata();
+	if (err)
+		pr_warn("failed to initialize kexec-metadata subtree: %d\n",
+			err);
+
+	return err;
+}
+
 static __init int kho_init(void)
 {
 	struct kho_radix_tree *tree = &kho_out.radix_tree;
@@ -1425,6 +1519,10 @@ static __init int kho_init(void)
 	if (err)
 		goto err_free_fdt;
 
+	err = kho_kexec_metadata_init(fdt);
+	if (err)
+		goto err_free_fdt;
+
 	if (fdt) {
 		kho_in_debugfs_init(&kho_in.dbg, fdt);
 		return 0;