This is a note to let you know that I've just added the patch titled
s390/bpf: Fix branch shortening during codegen pass
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-bpf-fix-branch-shortening-during-codegen-pass.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1511df6f5e9ef32826f20db2ee81f8527154dc14 Mon Sep 17 00:00:00 2001
From: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Date: Tue, 7 Sep 2021 11:58:59 +0200
Subject: s390/bpf: Fix branch shortening during codegen pass
From: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx>
Fixes: 4e9b4a6883dd ("s390/bpf: Use relative long branches")
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/net/bpf_jit_comp.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- 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 b
#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); \
Patches currently in stable-queue which might be from iii@xxxxxxxxxxxxx are
queue-5.10/s390-bpf-fix-branch-shortening-during-codegen-pass.patch
queue-5.10/s390-bpf-fix-optimizing-out-zero-extensions.patch
queue-5.10/s390-bpf-fix-64-bit-subtraction-of-the-0x80000000-constant.patch
