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s390: fix br_r1_trampoline for machines without exrl

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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>
This commit is contained in:
Martin Schwidefsky 2018-08-06 14:26:39 +02:00 committed by Greg Kroah-Hartman
parent 2edb10cbf2
commit 2502064731
1 changed files with 0 additions and 2 deletions
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arch/s390/net/bpf_jit_comp.c
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@ -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));