rtld: Add MD_OBJ_ENTRY to extend Struct_Obj_Entry

Add a macro the architectures can use to add per-arch fields to
Struct_Obj_Entry.

Reviewed by:	kib
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D45116

libexec/rtld-elf/aarch64/rtld_machdep.h

@@ -37,6 +37,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 #define	rtld_dynamic(obj)						\
 ({									\

libexec/rtld-elf/amd64/rtld_machdep.h

@@ -35,6 +35,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 Elf_Dyn *rtld_dynamic_addr(void);
 #define	rtld_dynamic(obj)	rtld_dynamic_addr()

libexec/rtld-elf/arm/rtld_machdep.h

@@ -36,6 +36,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 #define rtld_dynamic(obj) (&_DYNAMIC)
 

libexec/rtld-elf/i386/rtld_machdep.h

@@ -35,6 +35,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 #define rtld_dynamic(obj) \
     ((const Elf_Dyn *)((obj)->relocbase + (Elf_Addr)&_DYNAMIC))

libexec/rtld-elf/powerpc/rtld_machdep.h

@@ -35,6 +35,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 #define rtld_dynamic(obj)    (&_DYNAMIC)
 

libexec/rtld-elf/powerpc64/rtld_machdep.h

@@ -35,6 +35,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 /* Return the address of the .dynamic section in the dynamic linker. */
 #define rtld_dynamic(obj)    (&_DYNAMIC)
 

libexec/rtld-elf/riscv/rtld_machdep.h

@@ -42,6 +42,8 @@
 
 struct Struct_Obj_Entry;
 
+#define	MD_OBJ_ENTRY
+
 uint64_t set_gp(struct Struct_Obj_Entry *obj);
 
 /* Return the address of the .dynamic section in the dynamic linker. */

libexec/rtld-elf/rtld.h

@@ -277,6 +277,8 @@ typedef struct Struct_Obj_Entry {
     bool unholdfree : 1;	/* unmap upon last unhold */
     bool doomed : 1;		/* Object cannot be referenced */
 
+    MD_OBJ_ENTRY;
+
     struct link_map linkmap;	/* For GDB and dlinfo() */
     Objlist dldags;		/* Object belongs to these dlopened DAGs (%) */
     Objlist dagmembers;		/* DAG has these members (%) */