Am 19.11.21 um 02:10 schrieb Nick Desaulniers:
On Wed, Nov 17, 2021 at 9:48 AM Ilie Halip <ilie.halip@xxxxxxxxx> wrote: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@xxxxxxxxxx> Signed-off-by: Ilie Halip <ilie.halip@xxxxxxxxx>Ilie, thanks for the patch! So if I understand https://sourceware.org/binutils/docs/as/s390-Directives.html#s390-Directives https://sourceware.org/binutils/docs/as/s390-Formats.html that `e,` prefix is for 16B opcodes?
e is an instruction format as specified by the architecture. See http://publibfp.dhe.ibm.com/epubs/pdf/a227832c.pdf without any parameters. Normally RR would be the right thing for MVCL, but since we try to build an invalid opcode without the assembler noticing (ab)using e seem like a safer approach.
LGTM, thanks again. Suggested-by: Ulrich Weigand <Ulrich.Weigand@xxxxxxxxxx> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
added those and added my RB. applied to the s390 tree. Thanks
I triple checked that GAS, clang, and GNU objdump are in agreement in terms of encoding here.--- 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
