[RFC v1 8/9] kho: decouple vmalloc compatibility from global KHO version and update memfd

[Pasha Tatashin]

Decouple the vmalloc preservation compatibility version from the global
KHO compatibility version KHO_FDT_COMPATIBLE.

Define the independent compatibility version "vmalloc-v1" for vmalloc
preservation KHO_VMALLOC_COMPATIBLE in vmalloc.h.

Integrate KHO_VMALLOC_COMPATIBLE into the composite root compatibility
string KHO_FDT_COMPATIBLE.

Additionally, update the memfd compatibility string
MEMFD_LUO_FH_COMPATIBLE to include the vmalloc compatibility dependency,
and add a static assertion to verify its length limit.

Signed-off-by: Pasha Tatashin <pasha.tatashin at soleen.com>
---
 include/linux/kho/abi/kexec_handover.h | 4 +++-
 include/linux/kho/abi/memfd.h          | 9 ++++++++-
 include/linux/kho/abi/vmalloc.h        | 6 ++++--
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/kho/abi/kexec_handover.h b/include/linux/kho/abi/kexec_handover.h
index 49ac4b47cc3d..f048bc95fed3 100644
--- a/include/linux/kho/abi/kexec_handover.h
+++ b/include/linux/kho/abi/kexec_handover.h
@@ -10,6 +10,7 @@
 #define _LINUX_KHO_ABI_KEXEC_HANDOVER_H
 #include <linux/kho/abi/compat.h>
 #include <linux/kho/abi/radix_tree.h>
+#include <linux/kho/abi/vmalloc.h>
 
 /**
  * DOC: Kexec Handover ABI
@@ -87,7 +88,8 @@
 #define KHO_FDT_COMPAT_BASE "kho-v4"
 #define KHO_FDT_COMPATIBLE						\
 	KHO_FDT_COMPAT_BASE						\
-	KHO_SUB_COMPAT(KHO_RADIX_COMPATIBLE)
+	KHO_SUB_COMPAT(KHO_RADIX_COMPATIBLE)				\
+	KHO_SUB_COMPAT(KHO_VMALLOC_COMPATIBLE)
 
 /* The FDT property for the preserved memory map. */
 #define KHO_FDT_MEMORY_MAP_PROP_NAME "preserved-memory-map"
diff --git a/include/linux/kho/abi/memfd.h b/include/linux/kho/abi/memfd.h
index af310c0c9fdf..24ecbf48cbe1 100644
--- a/include/linux/kho/abi/memfd.h
+++ b/include/linux/kho/abi/memfd.h
@@ -11,7 +11,9 @@
 #ifndef _LINUX_KHO_ABI_MEMFD_H
 #define _LINUX_KHO_ABI_MEMFD_H
 
+#include <linux/kho/abi/compat.h>
 #include <linux/kho/abi/kexec_handover.h>
+#include <linux/kho/abi/luo.h>
 #include <linux/kho/abi/vmalloc.h>
 #include <linux/types.h>
 
@@ -89,6 +91,11 @@ struct memfd_luo_ser {
 } __packed;
 
 /* The compatibility string for memfd file handler */
-#define MEMFD_LUO_FH_COMPATIBLE	"memfd-v2"
+#define MEMFD_LUO_FH_COMPAT_BASE "memfd-v2"
+#define MEMFD_LUO_FH_COMPATIBLE						\
+	MEMFD_LUO_FH_COMPAT_BASE					\
+	KHO_SUB_COMPAT(KHO_VMALLOC_COMPATIBLE)
+
+static_assert(KHO_COMPAT_ALIGN(MEMFD_LUO_FH_COMPATIBLE) <= LIVEUPDATE_HNDL_COMPAT_LENGTH);
 
 #endif /* _LINUX_KHO_ABI_MEMFD_H */
diff --git a/include/linux/kho/abi/vmalloc.h b/include/linux/kho/abi/vmalloc.h
index 87650e1dd774..1847b82e147b 100644
--- a/include/linux/kho/abi/vmalloc.h
+++ b/include/linux/kho/abi/vmalloc.h
@@ -9,13 +9,13 @@
  *
  * The Kexec Handover ABI for preserving vmalloc'ed memory is defined by
  * a set of structures and helper macros. The layout of these structures is a
- * stable contract between kernels and is versioned by the KHO_FDT_COMPATIBLE
+ * stable contract between kernels and is versioned by the KHO_VMALLOC_COMPATIBLE
  * string.
  *
  * This interface is a contract. Any modification to the structure fields,
  * compatible strings, or the layout of the serialization structures defined
  * here constitutes a breaking change. Such changes require incrementing the
- * version number in the `KHO_FDT_COMPATIBLE` string to prevent a new kernel
+ * version number in the `KHO_VMALLOC_COMPATIBLE` string to prevent a new kernel
  * from misinterpreting data from an old kernel.
  *
  * Changes are allowed provided the compatibility version is incremented;
@@ -36,6 +36,8 @@
 #include <linux/types.h>
 #include <asm/page.h>
 
+#define KHO_VMALLOC_COMPATIBLE "vmalloc-v1"
+
 /* Helper macro to define a union for a serializable pointer. */
 #define DECLARE_KHOSER_PTR(name, type)	\
 	union {                        \
-- 
2.53.0