From: Ilya Leoshkevich iii@linux.ibm.com
[ Upstream commit 5fa6974471c5518a50bdd814067508dbcb477251 ]
"BPF_MAXINSNS: Maximum possible literals" test causes panic with bpf_jit_harden = 2. The reason is that BPF_JMP | BPF_EXIT is always emitted as brc, however, after removal of JITed image size limitations, brcl might be required.
Fix by using brcl when necessary.
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches") Signed-off-by: Ilya Leoshkevich iii@linux.ibm.com Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20200717165326.6786-4-iii@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/net/bpf_jit_comp.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 6b3d612948fba..6b8968f6e207d 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1268,8 +1268,12 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, last = (i == fp->len - 1) ? 1 : 0; if (last) break; - /* j <exit> */ - EMIT4_PCREL(0xa7f40000, jit->exit_ip - jit->prg); + if (!is_first_pass(jit) && can_use_rel(jit, jit->exit_ip)) + /* brc 0xf, <exit> */ + EMIT4_PCREL_RIC(0xa7040000, 0xf, jit->exit_ip); + else + /* brcl 0xf, <exit> */ + EMIT6_PCREL_RILC(0xc0040000, 0xf, jit->exit_ip); break; /* * Branch relative (number of skipped instructions) to offset on