Commit 26f84384 authored Aug 06, 2018 by Martin Schwidefsky

s390: fix br_r1_trampoline for machines without exrl



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: de5cb6eb ("s390: use expoline thunks in the BPF JIT")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

parent 5eda25b1

arch/s390/net/bpf_jit_comp.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -485,8 +485,6 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
		/* 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));