s390/test_unwind: use raw opcode instead of invalid instruction

Building with clang & LLVM_IAS=1 leads to an error:
    arch/s390/lib/test_unwind.c:179:4: error: invalid register pair
                        "       mvcl    %%r1,%%r1\n"
                        ^

The test creates an invalid instruction that would trap at runtime, but the
LLVM inline assembler tries to validate it at compile time too.

Use the raw instruction opcode instead.

Reported-by: Nick Desaulniers <[email protected]>
Signed-off-by: Ilie Halip <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Suggested-by: Ulrich Weigand <[email protected]>
Link: ClangBuiltLinux#1421
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Christian Borntraeger <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>
[[email protected]: use illegal opcode, and update comment]
Signed-off-by: Heiko Carstens <[email protected]>

Author: ihalip

arch/s390/lib/test_unwind.c

@@ -173,10 +173,11 @@ static noinline int unwindme_func4(struct unwindme *u)
 		}
 
 		/*
-		 * trigger specification exception
+		 * Trigger operation exception; use insn notation to bypass
+		 * llvm's integrated assembler sanity checks.
 		 */
 		asm volatile(
-			"	mvcl	%%r1,%%r1\n"
+			"	.insn	e,0x0000\n"	/* illegal opcode */
 			"0:	nopr	%%r7\n"
 			EX_TABLE(0b, 0b)
 			:);