[PATCH v4 10/30] liveupdate: luo_subsystems: implement subsystem callbacks

[Pasha Tatashin <pasha.tatashin@soleen.com>]

Implement the core logic within luo_subsystems.c to handle the
invocation of registered subsystem callbacks and manage the persistence
of their state via the LUO FDT. This replaces the stub implementations
from the previous patch.

This completes the core mechanism enabling subsystems to actively
participate in the LUO state machine, execute phase-specific logic, and
persist/restore a u64 state across the live update transition
using the FDT.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/liveupdate/luo_subsystems.c | 167 ++++++++++++++++++++++++++++-
 1 file changed, 164 insertions(+), 3 deletions(-)

diff --git a/kernel/liveupdate/luo_subsystems.c b/kernel/liveupdate/luo_subsystems.c
index 69f00d5c000e..ebb7c0db08f3 100644
--- a/kernel/liveupdate/luo_subsystems.c
+++ b/kernel/liveupdate/luo_subsystems.c
@@ -101,8 +101,81 @@ void __init luo_subsystems_startup(void *fdt)
 	luo_fdt_in = fdt;
 }
 
+static void __luo_do_subsystems_cancel_calls(struct liveupdate_subsystem *boundary_subsystem)
+{
+	struct liveupdate_subsystem *subsystem;
+
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		if (subsystem == boundary_subsystem)
+			break;
+
+		if (subsystem->ops->cancel) {
+			subsystem->ops->cancel(subsystem,
+					       subsystem->private_data);
+		}
+		subsystem->private_data = 0;
+	}
+}
+
+static void luo_subsystems_retrieve_data_from_fdt(void)
+{
+	struct liveupdate_subsystem *subsystem;
+	int node_offset, prop_len;
+	const void *prop;
+
+	if (!luo_fdt_in)
+		return;
+
+	node_offset = fdt_subnode_offset(luo_fdt_in, 0,
+					 LUO_SUBSYSTEMS_NODE_NAME);
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		prop = fdt_getprop(luo_fdt_in, node_offset,
+				   subsystem->name, &prop_len);
+
+		if (!prop || prop_len != sizeof(u64)) {
+			luo_restore_fail("In FDT node '/%s' can't find property '%s': %s\n",
+					 LUO_SUBSYSTEMS_NODE_NAME,
+					 subsystem->name,
+					 fdt_strerror(node_offset));
+		}
+		memcpy(&subsystem->private_data, prop, sizeof(u64));
+	}
+}
+
+static int luo_subsystems_commit_data_to_fdt(void)
+{
+	struct liveupdate_subsystem *subsystem;
+	int ret, node_offset;
+
+	node_offset = fdt_subnode_offset(luo_fdt_out, 0,
+					 LUO_SUBSYSTEMS_NODE_NAME);
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		ret = fdt_setprop(luo_fdt_out, node_offset, subsystem->name,
+				  &subsystem->private_data, sizeof(u64));
+		if (ret < 0) {
+			pr_err("Failed to set FDT property for subsystem '%s' %s\n",
+			       subsystem->name, fdt_strerror(ret));
+			return -ENOENT;
+		}
+	}
+
+	return 0;
+}
+
 static int luo_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
 {
+	int node_offset, prop_len;
+	const void *prop;
+
+	node_offset = fdt_subnode_offset(luo_fdt_in, 0,
+					 LUO_SUBSYSTEMS_NODE_NAME);
+	prop = fdt_getprop(luo_fdt_in, node_offset, h->name, &prop_len);
+	if (!prop || prop_len != sizeof(u64)) {
+		luo_state_read_exit();
+		return -ENOENT;
+	}
+	memcpy(data, prop, sizeof(u64));
+
 	return 0;
 }
 
@@ -121,7 +194,30 @@ static int luo_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
  */
 int luo_do_subsystems_prepare_calls(void)
 {
-	return 0;
+	struct liveupdate_subsystem *subsystem;
+	int ret;
+
+	guard(mutex)(&luo_subsystem_list_mutex);
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		if (!subsystem->ops->prepare)
+			continue;
+
+		ret = subsystem->ops->prepare(subsystem,
+					      &subsystem->private_data);
+		if (ret < 0) {
+			pr_err("Subsystem '%s' prepare callback failed [%d]\n",
+			       subsystem->name, ret);
+			__luo_do_subsystems_cancel_calls(subsystem);
+
+			return ret;
+		}
+	}
+
+	ret = luo_subsystems_commit_data_to_fdt();
+	if (ret)
+		__luo_do_subsystems_cancel_calls(NULL);
+
+	return ret;
 }
 
 /**
@@ -139,7 +235,30 @@ int luo_do_subsystems_prepare_calls(void)
  */
 int luo_do_subsystems_freeze_calls(void)
 {
-	return 0;
+	struct liveupdate_subsystem *subsystem;
+	int ret;
+
+	guard(mutex)(&luo_subsystem_list_mutex);
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		if (!subsystem->ops->freeze)
+			continue;
+
+		ret = subsystem->ops->freeze(subsystem,
+					     &subsystem->private_data);
+		if (ret < 0) {
+			pr_err("Subsystem '%s' freeze callback failed [%d]\n",
+			       subsystem->name, ret);
+			__luo_do_subsystems_cancel_calls(subsystem);
+
+			return ret;
+		}
+	}
+
+	ret = luo_subsystems_commit_data_to_fdt();
+	if (ret)
+		__luo_do_subsystems_cancel_calls(NULL);
+
+	return ret;
 }
 
 /**
@@ -150,6 +269,18 @@ int luo_do_subsystems_freeze_calls(void)
  */
 void luo_do_subsystems_finish_calls(void)
 {
+	struct liveupdate_subsystem *subsystem;
+
+	guard(mutex)(&luo_subsystem_list_mutex);
+	luo_subsystems_retrieve_data_from_fdt();
+
+	list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+		if (subsystem->ops->finish) {
+			subsystem->ops->finish(subsystem,
+					       subsystem->private_data);
+		}
+		subsystem->private_data = 0;
+	}
 }
 
 /**
@@ -163,6 +294,9 @@ void luo_do_subsystems_finish_calls(void)
  */
 void luo_do_subsystems_cancel_calls(void)
 {
+	guard(mutex)(&luo_subsystem_list_mutex);
+	__luo_do_subsystems_cancel_calls(NULL);
+	luo_subsystems_commit_data_to_fdt();
 }
 
 /**
@@ -285,7 +419,34 @@ int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h)
 	return ret;
 }
 
+/**
+ * liveupdate_get_subsystem_data - Retrieve raw private data for a subsystem
+ * from FDT.
+ * @h:      Pointer to the liveupdate_subsystem structure representing the
+ * subsystem instance. The 'name' field is used to find the property.
+ * @data:   Output pointer where the subsystem's raw private u64 data will be
+ * stored via memcpy.
+ *
+ * Reads the 8-byte data property associated with the subsystem @h->name
+ * directly from the '/subsystems' node within the globally accessible
+ * 'luo_fdt_in' blob. Returns appropriate error codes if inputs are invalid, or
+ * nodes/properties are missing or invalid.
+ *
+ * Return:  0 on success. -ENOENT on error.
+ */
 int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
 {
-	return 0;
+	int ret;
+
+	luo_state_read_enter();
+	if (WARN_ON_ONCE(!luo_fdt_in || !liveupdate_state_updated())) {
+		luo_state_read_exit();
+		return -ENOENT;
+	}
+
+	scoped_guard(mutex, &luo_subsystem_list_mutex)
+		ret = luo_get_subsystem_data(h, data);
+	luo_state_read_exit();
+
+	return ret;
 }
-- 
2.51.0.536.g15c5d4f767-goog