setjmp: export symbolic offsets in assembler

sdk/include/setjmp-assembly.h

diff --git a/sdk/include/setjmp-assembly.h b/sdk/include/setjmp-assembly.h
new file mode 100644
index 0000000..5c2bc30
--- /dev/null
+++ b/sdk/include/setjmp-assembly.h
@@ -0,0 +1,11 @@
+// Copyright CHERIoT Contributors.
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <assembly-helpers.h>
+
+EXPORT_ASSEMBLY_OFFSET(__jmp_buf, __cs0, 0)
+EXPORT_ASSEMBLY_OFFSET(__jmp_buf, __cs1, 8)
+EXPORT_ASSEMBLY_OFFSET(__jmp_buf, __csp, 16)
+EXPORT_ASSEMBLY_OFFSET(__jmp_buf, __cra, 24)

sdk/include/setjmp.h

diff --git a/sdk/include/setjmp.h b/sdk/include/setjmp.h
index b375667..9710ccd 100644
--- a/sdk/include/setjmp.h
+++ b/sdk/include/setjmp.h
@@ -30,6 +30,8 @@
  */
 typedef struct __jmp_buf jmp_buf[1];
 
+#include <setjmp-assembly.h>
+
 __BEGIN_DECLS
 /**
  * C `setjmp` function.  Returns (up to) twice.  First returns 0, returns a