s390: fix br_r1_trampoline for machines without exrl

commit 26f8438 upstream.

For machines without the exrl instruction the BFP jit generates
code that uses an "br %r1" instruction located in the lowcore page.
Unfortunately there is a cut & paste error that puts an additional
"larl %r1,.+14" instruction in the code that clobbers the branch
target address in %r1. Remove the larl instruction.

Cc: <[email protected]> # v4.17+
Fixes: de5cb6e ("s390: use expoline thunks in the BPF JIT")
Signed-off-by: Martin Schwidefsky <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Martin Schwidefsky

arch/s390/net/bpf_jit_comp.c

@@ -522,8 +522,6 @@ static void bpf_jit_epilogue(struct bpf_jit *jit)
 			/* br %r1 */
 			_EMIT2(0x07f1);
 		} else {
-			/* larl %r1,.+14 */
-			EMIT6_PCREL_RILB(0xc0000000, REG_1, jit->prg + 14);
 			/* ex 0,S390_lowcore.br_r1_tampoline */
 			EMIT4_DISP(0x44000000, REG_0, REG_0,
 				   offsetof(struct _lowcore, br_r1_trampoline));