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s390/bpf: Fix branch shortening during codegen pass

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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: 4e9b4a6883 ("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>
This commit is contained in:
Ilya Leoshkevich 2021-09-07 11:58:59 +02:00 committed by Greg Kroah-Hartman
parent 4320c222c2
commit ab7cf22501
1 changed files with 1 additions and 2 deletions
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arch/s390/net/bpf_jit_comp.c
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@ -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); \