CCall Examples

//file: ./bin/cheritest/cheritest_libcheri_trustedstack.c
/*
 * Perform a return without a corresponding invocation, to underflow the
 * trusted stack.
 */
void
test_sandbox_trustedstack_underflow(const struct cheri_test *ctp __unused)
{
	struct cheri_object returncap;
	void * __capability codecap /* currently ignored: asm ("$c1") */;
	void * __capability datacap /* currently ignored: asm ("$c2") */;

	returncap = libcheri_make_sealed_return_object();
	codecap = returncap.co_codecap;
	datacap = returncap.co_datacap;
	/*
	 * TODO: the branch delay slot has been removed. We can remove the nop
	 * once we no longer expect to run on older bitfiles
	 */
	__asm__ __volatile__ ("ccall %0, %1, 1\n\tnop" : : "C"(codecap),
	    "C"(datacap));
	cheritest_failure_errx("continued after attempted CReturn");
}