Commit dda014ba authored Nov 29, 2024 by Juergen Gross

objtool/x86: allow syscall instruction



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 <andrew.cooper3@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Co-developed-by: Peter Zijlstra <peterz@infradead.org>

parent efbcd61d

tools/objtool/check.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -3820,10 +3820,13 @@ static int validate_branch(struct objtool_file file, struct symbol func,
		break;

		case INSN_CONTEXT_SWITCH:
		if (func && (!next_insn \|\| !next_insn->hint)) {
		if (func) {
		if (!next_insn \|\| !next_insn->hint) {
		WARN_INSN(insn, "unsupported instruction in callable function");
		return 1;
		}
		break;
		}
		return 0;

		case INSN_STAC: