[PATCH v3 02/11] liveupdate: register luo_ser as KHO subtree
Pasha Tatashin
pasha.tatashin at soleen.com
Thu May 28 20:20:57 PDT 2026
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.
Signed-off-by: Pasha Tatashin <pasha.tatashin at soleen.com>
---
include/linux/kho/abi/luo.h | 57 +++++++++---------------
kernel/liveupdate/luo_core.c | 85 +++++++++++-------------------------
2 files changed, 46 insertions(+), 96 deletions(-)
diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 1b2f865a771a..9a4fe491812b 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -10,11 +10,11 @@
*
* Live Update Orchestrator uses the stable Application Binary Interface
* defined below to pass state from a pre-update kernel to a post-update
- * kernel. The ABI is built upon the Kexec HandOver framework and uses a
- * Flattened Device Tree to describe the preserved data.
+ * kernel. The ABI is built upon the Kexec HandOver framework and registers
+ * the central `struct luo_ser` via the KHO raw subtree API.
*
- * This interface is a contract. Any modification to the FDT structure, node
- * properties, compatible strings, or the layout of the `__packed` serialization
+ * This interface is a contract. Any modification to the structure fields,
+ * compatible strings, or the layout of the `__packed` serialization
* structures defined here constitutes a breaking change. Such changes require
* incrementing the version number in the relevant `_COMPATIBLE` string to
* prevent a new kernel from misinterpreting data from an old kernel.
@@ -23,31 +23,15 @@
* however, backward/forward compatibility is only guaranteed for kernels
* supporting the same ABI version.
*
- * FDT Structure Overview:
+ * KHO Structure Overview:
* The entire LUO state is encapsulated within a single KHO entry named "LUO".
- * This entry contains an FDT with the following layout:
- *
- * .. code-block:: none
- *
- * / {
- * compatible = "luo-v2";
- * luo-abi-header = <phys_addr_of_luo_ser>;
- * };
- *
- * Main LUO Node (/):
- *
- * - compatible: "luo-v2"
- * Identifies the overall LUO ABI version.
- * - luo-abi-header: u64
- * The physical address of `struct luo_ser`.
+ * This entry contains the `struct luo_ser` structure.
*
* Serialization Structures:
- * The FDT properties point to memory regions containing arrays of simple,
- * `__packed` structures. These structures contain the actual preserved state.
- *
* - struct luo_ser:
* The central ABI structure that contains the overall state of the LUO.
- * It includes the liveupdate-number and pointers to sessions and FLBs.
+ * It includes the compatibility string, the liveupdate-number, and pointers
+ * to sessions and FLBs.
*
* - struct luo_session_header_ser:
* Header for the session array. Contains the total page count of the
@@ -78,26 +62,27 @@
#ifndef _LINUX_KHO_ABI_LUO_H
#define _LINUX_KHO_ABI_LUO_H
+#include <linux/align.h>
#include <uapi/linux/liveupdate.h>
/*
- * The LUO FDT hooks all LUO state for sessions, fds, etc.
+ * The LUO state is registered under this KHO entry name.
*/
-#define LUO_FDT_SIZE PAGE_SIZE
-#define LUO_FDT_KHO_ENTRY_NAME "LUO"
-#define LUO_FDT_COMPATIBLE "luo-v2"
-#define LUO_FDT_ABI_HEADER "luo-abi-header"
+#define LUO_KHO_ENTRY_NAME "LUO"
+#define LUO_ABI_COMPATIBLE "luo-v3"
+#define LUO_ABI_COMPAT_LEN ALIGN(sizeof(LUO_ABI_COMPATIBLE), 8)
/**
* struct luo_ser - Centralized LUO ABI header.
+ * @compatible: Compatibility string identifying the LUO ABI version.
* @liveupdate_num: A counter tracking the number of successful live updates.
* @sessions_pa: Physical address of the first session block header.
* @flbs_pa: Physical address of the FLB header.
*
- * This structure is the root of all preserved LUO state. It is pointed to by
- * the "luo-abi-header" property in the LUO FDT.
+ * This structure is the root of all preserved LUO state.
*/
struct luo_ser {
+ char compatible[LUO_ABI_COMPAT_LEN];
u64 liveupdate_num;
u64 sessions_pa;
u64 flbs_pa;
@@ -111,7 +96,7 @@ struct luo_ser {
* @data: Private data
* @token: User provided token for this file
*
- * If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_file_ser {
char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
@@ -142,7 +127,7 @@ struct luo_file_set_ser {
* physical memory preserved across the kexec. It provides the necessary
* metadata to interpret the array of session entries that follow.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_session_header_ser {
u64 count;
@@ -159,7 +144,7 @@ struct luo_session_header_ser {
* session) is created and passed to the new kernel, allowing it to reconstruct
* the session context.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_session_ser {
char name[LIVEUPDATE_SESSION_NAME_LENGTH];
@@ -180,7 +165,7 @@ struct luo_session_ser {
* This structure is located at the physical address specified by the
* flbs_pa in luo_ser.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_flb_header_ser {
u64 pgcnt;
@@ -202,7 +187,7 @@ struct luo_flb_header_ser {
* passed to the new kernel. Each entry allows the LUO core to restore one
* global, shared object.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_flb_ser {
char name[LIVEUPDATE_FLB_COMPAT_LENGTH];
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index c1c290aefc76..5e12c8f8669b 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -50,7 +50,6 @@
#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>
@@ -63,8 +62,7 @@
static struct {
bool enabled;
- void *fdt_out;
- void *fdt_in;
+ struct luo_ser *luo_ser_out;
u64 liveupdate_num;
} luo_global;
@@ -81,11 +79,10 @@ 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())
@@ -94,40 +91,29 @@ 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);
@@ -156,37 +142,20 @@ 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)
@@ -196,21 +165,17 @@ 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;
}
@@ -226,7 +191,7 @@ 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;
--
2.53.0
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