linux-kernel - [PATCH] s390/test_unwind: use raw opcode instead of invalid instruction

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Date:   Wed, 17 Nov 2021 19:48:21 +0200
From:   Ilie Halip <ilie.halip@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ilie Halip <ilie.halip@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Mete Durlu <meted@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        linux-s390@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH] 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.

Link: https://github.com/ClangBuiltLinux/linux/issues/1421
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Ilie Halip <ilie.halip@...il.com>
---
 arch/s390/lib/test_unwind.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/lib/test_unwind.c b/arch/s390/lib/test_unwind.c
index cfc5f5557c06..d342bc884b94 100644
--- a/arch/s390/lib/test_unwind.c
+++ b/arch/s390/lib/test_unwind.c
@@ -176,7 +176,7 @@ static noinline int unwindme_func4(struct unwindme *u)
 		 * trigger specification exception
 		 */
 		asm volatile(
-			"	mvcl	%%r1,%%r1\n"
+			"	.insn e,0x0e11\n"	/* mvcl	%%r1,%%r1" */
 			"0:	nopr	%%r7\n"
 			EX_TABLE(0b, 0b)
 			:);
-- 
2.25.1