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authorIlya Leoshkevich <iii@linux.ibm.com>2020-09-10 01:21:41 +0200
committerAlexei Starovoitov <ast@kernel.org>2020-09-14 18:21:31 -0700
commitd72714c1da138e6755d3bd14662dc5b7f17fae7f (patch)
tree2189c79bb786aa66f50823217cdc9c3e91b392fd /samples/bpf
parent2bab48c5bef00d103085da71a01da27ec7200c08 (diff)
downloadlinux-stericsson-d72714c1da138e6755d3bd14662dc5b7f17fae7f.tar.gz
s390/bpf: Fix multiple tail calls
In order to branch around tail calls (due to out-of-bounds index, exceeding tail call count or missing tail call target), JIT uses label[0] field, which contains the address of the instruction following the tail call. When there are multiple tail calls, label[0] value comes from handling of a previous tail call, which is incorrect. Fix by getting rid of label array and resolving the label address locally: for all 3 branches that jump to it, emit 0 offsets at the beginning, and then backpatch them with the correct value. Also, do not use the long jump infrastructure: the tail call sequence is known to be short, so make all 3 jumps short. Fixes: 6651ee070b31 ("s390/bpf: implement bpf_tail_call() helper") Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200909232141.3099367-1-iii@linux.ibm.com
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