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authorHeiko Carstens <heiko.carstens@de.ibm.com>2014-01-17 09:37:15 +0100
committerDavid S. Miller <davem@davemloft.net>2014-01-17 18:54:49 -0800
commit3af57f78c38131b7a66e2b01e06fdacae01992a3 (patch)
treee19b729126d28efa4f4325b21f834100d981e5bf /arch/s390/net
parent75b99dbd634f9caf7b4e48ec5c2dcec8c1837372 (diff)
downloadlinux-3af57f78c38131b7a66e2b01e06fdacae01992a3.tar.gz
s390/bpf,jit: fix 32 bit divisions, use unsigned divide instructions
The s390 bpf jit compiler emits the signed divide instructions "dr" and "d" for unsigned divisions. This can cause problems: the dividend will be zero extended to a 64 bit value and the divisor is the 32 bit signed value as specified A or X accumulator, even though A and X are supposed to be treated as unsigned values. The divide instrunctions will generate an exception if the result cannot be expressed with a 32 bit signed value. This is the case if e.g. the dividend is 0xffffffff and the divisor either 1 or also 0xffffffff (signed: -1). To avoid all these issues simply use unsigned divide instructions. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/s390/net')
-rw-r--r--arch/s390/net/bpf_jit_comp.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index fc0fa77728e1..708d60e40066 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -368,16 +368,16 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
EMIT4_PCREL(0xa7840000, (jit->ret0_ip - jit->prg));
/* lhi %r4,0 */
EMIT4(0xa7480000);
- /* dr %r4,%r12 */
- EMIT2(0x1d4c);
+ /* dlr %r4,%r12 */
+ EMIT4(0xb997004c);
break;
case BPF_S_ALU_DIV_K: /* A /= K */
if (K == 1)
break;
/* lhi %r4,0 */
EMIT4(0xa7480000);
- /* d %r4,<d(K)>(%r13) */
- EMIT4_DISP(0x5d40d000, EMIT_CONST(K));
+ /* dl %r4,<d(K)>(%r13) */
+ EMIT6_DISP(0xe340d000, 0x0097, EMIT_CONST(K));
break;
case BPF_S_ALU_MOD_X: /* A %= X */
jit->seen |= SEEN_XREG | SEEN_RET0;
@@ -387,8 +387,8 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
EMIT4_PCREL(0xa7840000, (jit->ret0_ip - jit->prg));
/* lhi %r4,0 */
EMIT4(0xa7480000);
- /* dr %r4,%r12 */
- EMIT2(0x1d4c);
+ /* dlr %r4,%r12 */
+ EMIT4(0xb997004c);
/* lr %r5,%r4 */
EMIT2(0x1854);
break;
@@ -400,8 +400,8 @@ static int bpf_jit_insn(struct bpf_jit *jit, struct sock_filter *filter,
}
/* lhi %r4,0 */
EMIT4(0xa7480000);
- /* d %r4,<d(K)>(%r13) */
- EMIT4_DISP(0x5d40d000, EMIT_CONST(K));
+ /* dl %r4,<d(K)>(%r13) */
+ EMIT6_DISP(0xe340d000, 0x0097, EMIT_CONST(K));
/* lr %r5,%r4 */
EMIT2(0x1854);
break;