elf: Allow core dump-related fields to be overridden

Allow some core dump-related fields to be overridden.  This allows
core dumps to work correctly for x32.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>

fs/binfmt_elf.c

@@ -1390,6 +1390,22 @@ static void do_thread_regset_writeback(struct task_struct *task,
 		regset->writeback(task, regset, 1);
 }
 
+#ifndef PR_REG_SIZE
+#define PR_REG_SIZE(S) sizeof(S)
+#endif
+
+#ifndef PRSTATUS_SIZE
+#define PRSTATUS_SIZE(S) sizeof(S)
+#endif
+
+#ifndef PR_REG_PTR
+#define PR_REG_PTR(S) (&((S)->pr_reg))
+#endif
+
+#ifndef SET_PR_FPVALID
+#define SET_PR_FPVALID(S, V) ((S)->pr_fpvalid = (V))
+#endif
+
 static int fill_thread_core_info(struct elf_thread_core_info *t,
 				 const struct user_regset_view *view,
 				 long signr, size_t *total)
@@ -1404,11 +1420,11 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 	 */
 	fill_prstatus(&t->prstatus, t->task, signr);
 	(void) view->regsets[0].get(t->task, &view->regsets[0],
-				    0, sizeof(t->prstatus.pr_reg),
-				    &t->prstatus.pr_reg, NULL);
+				    0, PR_REG_SIZE(t->prstatus.pr_reg),
+				    PR_REG_PTR(&t->prstatus), NULL);
 
 	fill_note(&t->notes[0], "CORE", NT_PRSTATUS,
-		  sizeof(t->prstatus), &t->prstatus);
+		  PRSTATUS_SIZE(t->prstatus), &t->prstatus);
 	*total += notesize(&t->notes[0]);
 
 	do_thread_regset_writeback(t->task, &view->regsets[0]);
@@ -1438,7 +1454,7 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
 						  regset->core_note_type,
 						  size, data);
 				else {
-					t->prstatus.pr_fpvalid = 1;
+					SET_PR_FPVALID(&t->prstatus, 1);
 					fill_note(&t->notes[i], "CORE",
 						  NT_PRFPREG, size, data);
 				}