[RFC v2 02/16] kho: allow to drive kho from within kernel

[Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>]

Allow to do finalize and abort from kernel modules, so LUO could
drive the KHO sequence via its own state machine.

Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
---
 include/linux/kexec_handover.h   | 15 +++++++++
 kernel/kexec_handover.c          | 54 ++++++++++++++++++++++++++++++++
 kernel/kexec_handover_debug.c    |  2 +-
 kernel/kexec_handover_internal.h |  2 ++
 4 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 348844cffb13..f98565def593 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -54,6 +54,10 @@ void kho_memory_init(void);
 
 void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,
 		  u64 scratch_len);
+
+int kho_finalize(void);
+int kho_abort(void);
+
 #else
 static inline bool kho_is_enabled(void)
 {
@@ -104,6 +108,17 @@ static inline void kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
 				phys_addr_t scratch_phys, u64 scratch_len)
 {
 }
+
+static inline int kho_finalize(void)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int kho_abort(void)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif /* CONFIG_KEXEC_HANDOVER */
 
 #endif /* LINUX_KEXEC_HANDOVER_H */
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 5b65970e9746..8ff561e36a87 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -734,6 +734,60 @@ int __kho_finalize(void)
 	return err;
 }
 
+int kho_finalize(void)
+{
+	int ret = 0;
+
+	if (!kho_enable)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&kho_out.lock);
+
+	if (kho_out.finalized) {
+		ret = -EEXIST;
+		goto unlock;
+	}
+
+	ret = __kho_finalize();
+	if (ret)
+		goto unlock;
+
+	kho_out.finalized = true;
+	ret = kho_out_update_debugfs_fdt();
+
+unlock:
+	mutex_unlock(&kho_out.lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kho_finalize);
+
+int kho_abort(void)
+{
+	int ret = 0;
+
+	if (!kho_enable)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&kho_out.lock);
+
+	if (!kho_out.finalized) {
+		ret = -ENOENT;
+		goto unlock;
+	}
+
+	ret = __kho_abort();
+	if (ret)
+		goto unlock;
+
+	kho_out.finalized = false;
+	ret = kho_out_update_debugfs_fdt();
+
+unlock:
+	mutex_unlock(&kho_out.lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kho_abort);
+
 struct kho_in kho_in = {
 	.fdt_list = LIST_HEAD_INIT(kho_in.fdt_list),
 };
diff --git a/kernel/kexec_handover_debug.c b/kernel/kexec_handover_debug.c
index 696131a3480f..a15c238ec98e 100644
--- a/kernel/kexec_handover_debug.c
+++ b/kernel/kexec_handover_debug.c
@@ -55,7 +55,7 @@ int kho_debugfs_fdt_add(struct kho_serialization *ser, const char *name,
 				     fdt);
 }
 
-static int kho_out_update_debugfs_fdt(void)
+int kho_out_update_debugfs_fdt(void)
 {
 	int err = 0;
 	struct fdt_debugfs *ff, *tmp;
diff --git a/kernel/kexec_handover_internal.h b/kernel/kexec_handover_internal.h
index 65ff0f651192..0b534758d39d 100644
--- a/kernel/kexec_handover_internal.h
+++ b/kernel/kexec_handover_internal.h
@@ -60,6 +60,7 @@ void kho_in_debugfs_init(const void *fdt);
 int kho_out_debugfs_init(void);
 int kho_debugfs_fdt_add(struct kho_serialization *ser, const char *name,
 			const void *fdt);
+int kho_out_update_debugfs_fdt(void);
 #else
 static inline int kho_debugfs_init(void) { return 0; }
 static inline void kho_in_debugfs_init(const void *fdt) { }
@@ -67,6 +68,7 @@ static inline int kho_out_debugfs_init(void) { return 0; }
 static inline int kho_debugfs_fdt_add(struct kho_serialization *ser,
 				      const char *name,
 				      const void *fdt) { return 0; }
+static inline int kho_out_update_debugfs_fdt(void) { return 0; }
 #endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
 
 #endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
-- 
2.49.0.1101.gccaa498523-goog