4.4-stable review patch. If anyone has any objections, please let me know.
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From: Martin Schwidefsky schwidefsky@de.ibm.com
commit 26f843848bae973817b3587780ce6b7b0200d3e4 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: stable@vger.kernel.org # v4.17+ Fixes: de5cb6eb51 ("s390: use expoline thunks in the BPF JIT") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/s390/net/bpf_jit_comp.c | 2 -- 1 file changed, 2 deletions(-)
--- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -522,8 +522,6 @@ static void bpf_jit_epilogue(struct bpf_ /* 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));