From: Ilya Leoshkevich <iii@linux.ibm.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH 3/5] s390/bpf: use brcl for jumping to exit_ip if necessary
Date: Fri, 17 Jul 2020 18:53:24 +0200 [thread overview]
Message-ID: <20200717165326.6786-4-iii@linux.ibm.com> (raw)
In-Reply-To: <20200717165326.6786-1-iii@linux.ibm.com>
"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>
---
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 67608f6092f8..625ebe32b2d1 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -1358,8 +1358,12 @@ 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
--
2.25.4
next prev parent reply other threads:[~2020-07-17 16:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 16:53 [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 1/5] selftests: bpf: test_kmod.sh: fix running out of srctree Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 2/5] s390/bpf: fix sign extension in branch_ku Ilya Leoshkevich
2020-07-17 22:23 ` Seth Forshee
2020-07-17 16:53 ` Ilya Leoshkevich [this message]
2020-07-17 16:53 ` [PATCH 4/5] s390/bpf: tolerate not converging code shrinking Ilya Leoshkevich
2020-07-17 16:53 ` [PATCH 5/5] s390/bpf: use bpf_skip() in bpf_jit_prologue() Ilya Leoshkevich
2020-07-21 18:17 ` [PATCH 0/5] s390/bpf: fix lib/test_bpf.c failures Alexei Starovoitov
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