objtool/x86: allow syscall instruction

commit dda014ba59331dee4f3b773a020e109932f4bd24 upstream. The syscall instruction is used in Xen PV mode for doing hypercalls. Allow syscall to be used in the kernel in case it is tagged with an unwind hint for objtool. This is part of XSA-466 / CVE-2024-53241. Reported-by: Andrew Cooper <[email protected]> Signed-off-by: Juergen Gross <[email protected]> Co-developed-by: Peter Zijlstra <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
frank-w · Dec 19, 2024 · 8fb54fe · 8fb54fe
1 parent aac984c
commit 8fb54fe
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
@@ -3719,9 +3719,12 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			break;
 
 		case INSN_CONTEXT_SWITCH:
-			if (func && (!next_insn || !next_insn->hint)) {
-				WARN_INSN(insn, "unsupported instruction in callable function");
-				return 1;
+			if (func) {
+				if (!next_insn || !next_insn->hint) {
+					WARN_INSN(insn, "unsupported instruction in callable function");
+					return 1;
+				}
+				break;
 			}
 			return 0;