liveupdate: register luo_ser as KHO subtree

Entirely remove the LUO FDT wrapper since the FDT only carries the
compatible string and the pointer to the centralized struct luo_ser.
Instead, register the struct luo_ser via the KHO raw subtree
API, placing the compatibility string inside the structure itself.

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260603154402.468928-5-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

1 files changed, 25 insertions, 60 deletions

diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 085c0dfc1ef1..69b00e7d0f8f 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -54,7 +54,6 @@
 #include <linux/kexec_handover.h>
 #include <linux/kho/abi/luo.h>
 #include <linux/kobject.h>
-#include <linux/libfdt.h>
 #include <linux/liveupdate.h>
 #include <linux/miscdevice.h>
 #include <linux/mm.h>
@@ -67,8 +66,7 @@
 
 static struct {
 	bool enabled;
-	void *fdt_out;
-	void *fdt_in;
+	struct luo_ser *luo_ser_out;
 	u64 liveupdate_num;
 } luo_global;
 
@@ -85,11 +83,10 @@ early_param("liveupdate", early_liveupdate_param);
 
 static int __init luo_early_startup(void)
 {
+	phys_addr_t luo_ser_phys;
 	struct luo_ser *luo_ser;
-	int err, header_size;
-	phys_addr_t fdt_phys;
-	const void *ptr;
-	u64 luo_ser_pa;
+	size_t len;
+	int err;
 
 	if (!kho_is_enabled()) {
 		if (liveupdate_enabled())
@@ -98,40 +95,29 @@ static int __init luo_early_startup(void)
 		return 0;
 	}
 
-	/* Retrieve LUO subtree, and verify its format. */
-	err = kho_retrieve_subtree(LUO_FDT_KHO_ENTRY_NAME, &fdt_phys, NULL);
+	/* Retrieve LUO state from KHO. */
+	err = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, &luo_ser_phys, &len);
 	if (err) {
 		if (err != -ENOENT) {
-			pr_err("failed to retrieve FDT '%s' from KHO: %pe\n",
-			       LUO_FDT_KHO_ENTRY_NAME, ERR_PTR(err));
+			pr_err("failed to retrieve LUO state '%s' from KHO: %pe\n",
+			       LUO_KHO_ENTRY_NAME, ERR_PTR(err));
 			return err;
 		}
 
 		return 0;
 	}
 
-	luo_global.fdt_in = phys_to_virt(fdt_phys);
-	err = fdt_node_check_compatible(luo_global.fdt_in, 0,
-					LUO_FDT_COMPATIBLE);
-	if (err) {
-		pr_err("FDT '%s' is incompatible with '%s' [%d]\n",
-		       LUO_FDT_KHO_ENTRY_NAME, LUO_FDT_COMPATIBLE, err);
-
+	if (len < sizeof(*luo_ser)) {
+		pr_err("LUO state is too small (%zu < %zu)\n", len, sizeof(*luo_ser));
 		return -EINVAL;
 	}
 
-	header_size = 0;
-	ptr = fdt_getprop(luo_global.fdt_in, 0, LUO_FDT_ABI_HEADER, &header_size);
-	if (!ptr || header_size != sizeof(u64)) {
-		pr_err("Unable to get ABI header '%s' [%d]\n",
-		       LUO_FDT_ABI_HEADER, header_size);
-
+	luo_ser = phys_to_virt(luo_ser_phys);
+	if (strncmp(luo_ser->compatible, LUO_ABI_COMPATIBLE, LUO_ABI_COMPAT_LEN)) {
+		pr_err("LUO state is incompatible with '%s'\n", LUO_ABI_COMPATIBLE);
 		return -EINVAL;
 	}
 
-	luo_ser_pa = get_unaligned((u64 *)ptr);
-	luo_ser = phys_to_virt(luo_ser_pa);
-
 	luo_global.liveupdate_num = luo_ser->liveupdate_num;
 	pr_info("Retrieved live update data, liveupdate number: %lld\n",
 		luo_global.liveupdate_num);
@@ -164,37 +150,20 @@ static int __init liveupdate_early_init(void)
 }
 early_initcall(liveupdate_early_init);
 
-/* Called during boot to create outgoing LUO fdt tree */
-static int __init luo_fdt_setup(void)
+/* Called during boot to create outgoing LUO state */
+static int __init luo_state_setup(void)
 {
 	struct luo_ser *luo_ser;
-	u64 luo_ser_pa;
-	void *fdt_out;
 	int err;
 
-	fdt_out = kho_alloc_preserve(LUO_FDT_SIZE);
-	if (IS_ERR(fdt_out)) {
-		pr_err("failed to allocate/preserve FDT memory\n");
-		return PTR_ERR(fdt_out);
-	}
-
 	luo_ser = kho_alloc_preserve(sizeof(*luo_ser));
 	if (IS_ERR(luo_ser)) {
-		err = PTR_ERR(luo_ser);
-		goto exit_free_fdt;
+		pr_err("failed to allocate/preserve LUO state memory\n");
+		return PTR_ERR(luo_ser);
 	}
-	luo_ser_pa = virt_to_phys(luo_ser);
-
-	err = fdt_create(fdt_out, LUO_FDT_SIZE);
-	err |= fdt_finish_reservemap(fdt_out);
-	err |= fdt_begin_node(fdt_out, "");
-	err |= fdt_property_string(fdt_out, "compatible", LUO_FDT_COMPATIBLE);
-	err |= fdt_property(fdt_out, LUO_FDT_ABI_HEADER, &luo_ser_pa,
-			    sizeof(luo_ser_pa));
-	err |= fdt_end_node(fdt_out);
-	err |= fdt_finish(fdt_out);
-	if (err)
-		goto exit_free_luo_ser;
+
+	strscpy(luo_ser->compatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser->compatible));
+	luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
 
 	err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
 	if (err)
@@ -204,21 +173,17 @@ static int __init luo_fdt_setup(void)
 	if (err)
 		goto exit_free_luo_ser;
 
-	luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
-
-	err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out,
-			      fdt_totalsize(fdt_out));
+	err = kho_add_subtree(LUO_KHO_ENTRY_NAME, luo_ser, sizeof(*luo_ser));
 	if (err)
 		goto exit_free_luo_ser;
-	luo_global.fdt_out = fdt_out;
+
+	luo_global.luo_ser_out = luo_ser;
 
 	return 0;
 
 exit_free_luo_ser:
 	kho_unpreserve_free(luo_ser);
-exit_free_fdt:
-	kho_unpreserve_free(fdt_out);
-	pr_err("failed to prepare LUO FDT: %d\n", err);
+	pr_err("failed to prepare LUO state: %d\n", err);
 
 	return err;
 }
@@ -234,7 +199,7 @@ static int __init luo_late_startup(void)
 	if (!liveupdate_enabled())
 		return 0;
 
-	err = luo_fdt_setup();
+	err = luo_state_setup();
 	if (err)
 		luo_global.enabled = false;