[PATCH v15 05/23] tools: include: Add kbuild.h for assembly structure offsets

[Lisa Wang <wyihan@google.com>]

From: Sagi Shahar <sagis@google.com>

Add the Kbuild macros needed to enable the filechk_offsets mechanism to
generate C header files containing structure member offset information.

Tools depending on assembly code that operate on structures have to
hardcode the offsets of structure members. The Kbuild infrastructure
can instead generate C header files with these offsets automatically,
allowing them to be included in assembly code as symbolic constants.

For example, the TDX guest boot code requires access to parameters
passed in the C structure (struct td_boot_parameters). This header
provides the macros needed to extract these offsets from C code and
expose them to assembly, ensuring the two remain synchronized.

Signed-off-by: Sagi Shahar <sagis@google.com>
Signed-off-by: Lisa Wang <wyihan@google.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
---
 tools/include/linux/kbuild.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/include/linux/kbuild.h b/tools/include/linux/kbuild.h
new file mode 100644
index 000000000000..957fd55cd159
--- /dev/null
+++ b/tools/include/linux/kbuild.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __TOOLS_LINUX_KBUILD_H
+#define __TOOLS_LINUX_KBUILD_H
+
+#define DEFINE(sym, val) \
+	asm volatile("\n.ascii \"->" #sym " %0 " #val "\"" : : "i" (val))
+
+#define OFFSET(sym, str, mem) \
+	DEFINE(sym, __builtin_offsetof(struct str, mem))
+
+#endif /* __TOOLS_LINUX_KBUILD_H */

-- 
2.56.0.rc1.315.gc6ed9934b7-goog