From a7593244dc31ad0eea70319f6110975f9c738dca Mon Sep 17 00:00:00 2001
From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Tue, 7 Sep 2021 11:58:59 +0200
Subject: [PATCH] s390/bpf: Fix branch shortening during codegen pass
Git-commit: 1511df6f5e9ef32826f20db2ee81f8527154dc14
Patch-mainline: v5.15-rc3
References: stable-5.14.7
commit 1511df6f5e9ef32826f20db2ee81f8527154dc14 upstream.
EMIT6_PCREL() macro assumes that the previous pass generated 6 bytes
of code, which is not the case if branch shortening took place. Fix by
using jit->prg, like all the other EMIT6_PCREL_*() macros.
Reported-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
arch/s390/net/bpf_jit_comp.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 59ed11f1660f..840d8594437d 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -248,8 +248,7 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
#define EMIT6_PCREL(op1, op2, b1, b2, i, off, mask) \
({ \
- /* Branch instruction needs 6 bytes */ \
- int rel = (addrs[(i) + (off) + 1] - (addrs[(i) + 1] - 6)) / 2;\
+ int rel = (addrs[(i) + (off) + 1] - jit->prg) / 2; \
_EMIT6((op1) | reg(b1, b2) << 16 | (rel & 0xffff), (op2) | (mask));\
REG_SET_SEEN(b1); \
REG_SET_SEEN(b2); \
--
2.26.2